Sanz Rodrigo 2012

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Wind engineering in the integrated design of princess Elisabeth Antarctic base

Javier Sanz Rodrigo*, Jeroen van Beeck, Jean-Marie Buchlin

von Karman Institute for Fluid Dynamics (VKI), Chaussée de Waterloo 72, B-1640 Rhode-St-Genèse, Belgium

a r t i c l e i n f o

Article history:

Received 15 October 2011

Received in revised form

19 December 2011

Accepted 29 December 2011

Keywords:

Antarctica

Integrated design

Wind engineering

Snowdrift

Wind loading

Sand erosion

a b s t r a c t

The Belgian Antarctic Base Princess Elisabeth is based on an elevated building on top of sloping terrain

and connected to an under-snow garage. The integrated design of the base was supported by wind

engineering testing that looked into building aerodynamics (pressure taps) and snowdrift management.Wind tunnel modeling using sand erosion technique allowed ef cient evaluation of the snow erosion

and deposition around different building-block shapes during the conceptual design phase. Parametric

testing shows that the positioning of the main building on the ridge has a signicant impact on wind

loading and snow erosion and deposition. Important reductions in wind loading and snow deposition

can be obtained by elevating the building and reducing the windward cantilever. The positioning of the

garage roof can further decrease the wind loading by acting as a diffuser in the back of the building. This

study shows that, not only for safety and cost reduction but also for the integration of renewable

energies, important benets in the design of a building can be achieved if wind engineering is considered

since the conceptual phase of the integrated building design process.

2012 Elsevier Ltd. All rights reserved.

1. Introduction

The concern about Climate Change has signicantly increased

the interest of scientic research in Antarctica. Coinciding with the

International Polar Year (IPY) 2007e2008, three European research

bases were designed and have recently been deployed in Antarc-

tica: Halley VI (United Kingdom), Newmayer III (Germany) and

Princess Elisabeth (Belgium).

The new stations put in evidence the primary role that the

environmental conditions play on their design, especially when

higher levels of sustainability and energy ef ciency are pursued, as

it is the case for the Princess Elisabeth “Zero Emission” research

station.

The integrated design process, implemented in the case of the

Princess Elisabeth base, aims at making best use of the ambient

conditions in the design of energy ef cient buildings with the leastimpact on the environment throughout their lifetime. The use of

renewable energies in Antarctica as primary energy source

provides more autonomy, minimizing the fuel consumption with

the corresponding savings in logistics, CO2 emissionsand risks of oil

spill contamination.

The extreme weather conditions make Antarctic construction

the forefront of Bioclimatic Architecture, with katabatic winds up to

70 m s1 that induce important structural loading; snow drifting

that can produce annual build-ups as high as 1.5 m, making

accessibility dif cult and increasing maintenance works; temper-

atures as lowas 60 C that induce important heat losses; and very

low humidity that increases the risk of re. Furthermore, the

Antarctic environment constitutes an excellent test bench for the

demonstration of renewable energies and energy ef ciency

technology.

All in all, it is evident that building design in Antarctica

requires careful consideration of the environment in order to nd

safe and cost-effective solutions with the least impact on the

environment, a key aspect of the Antarctic-Environmental

Protocol (1991).

1.1. Philosophy of a zero emission station

The Princess Elisabeth Antarctic research station is situated

approximately 1 km North of Utsteinen Nunatak, on a small and

relatively at granite ridge (71570S 23200E, 1390 m a.s.l.), 173 km

inland from the former Roi Baudouin base and 55 km from former

Japanese Asuka station. The new station occupies the empty space,

in the 20e30 East sector, left by the closing of Asuka station in

1992. The nearest permanent stations are Syowa (Japan), 684 km to

the west, and the Novolazarevskaya (Russia), 431 km to the east.

The nearest coast is some 190 km north.

* Corresponding author. National Renewable Energy Centre of Spain (CENER),

C/Ciudad de la Innovación 7, 31621 Sarriguren, Spain. Tel.: þ34 948 25 28 00;

fax: þ34 948 27 07 74.

E-mail address: [email protected] (J. Sanz Rodrigo).

Contents lists available at SciVerse ScienceDirect

Building and Environment

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c om / l o c a t e / b u i l d e n v

0360-1323/$ e see front matter 2012 Elsevier Ltd. All rights reserved.

doi:10.1016/j.buildenv.2011.12.023

Building and Environment 52 (2012) 1e18

mailto:[email protected]://www.sciencedirect.com/science/journal/03601323http://www.elsevier.com/locate/buildenvhttp://dx.doi.org/10.1016/j.buildenv.2011.12.023http://dx.doi.org/10.1016/j.buildenv.2011.12.023http://dx.doi.org/10.1016/j.buildenv.2011.12.023http://dx.doi.org/10.1016/j.buildenv.2011.12.023http://dx.doi.org/10.1016/j.buildenv.2011.12.023http://dx.doi.org/10.1016/j.buildenv.2011.12.023http://www.elsevier.com/locate/buildenvhttp://www.sciencedirect.com/science/journal/03601323mailto:[email protected]


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The selected site is very convenient as it provides stable ground

for anchoring. The station design makes best use of terrain condi-

tions for the integration of the building following a hybrid design.

The main building, above ground-level and anchored onto snow-

free rock area is connected, with a weather protected bridge, to

an adjacent garage/storage building, constructed under the snow

surface (Fig. 1). The summer station is designed for optimal use by

12 people with a surface area (living, technical, research, storage) of

800 m2. An extension, based on heated shelters, make it possible to

accommodate another 8 to 18 people.

The system design of the station is based on sustainable tech-

nology and high-energy ef ciency, with full-year monitoring and

remote sensing capability. The station aims at being zero-

emissions, making use of renewable energy as the primary

energy source and integrating passive building design in

a comprehensive energy management regime, thereby minimizing

the use of fossil fuels. The power budget of the station is composed

of 48% of wind power from nine wind turbines, 20% of solar

photovoltaic from 380 m2 of solar panels and 12% solar thermal

with 22 m2 of solar panels.

The internal layout of the main building is designed with

concentric layers around a central technical core, which holds the

control systems, the water treatment unit and the batteries forenergy storage. Around the technical core, the kitchen and laundry

rooms and the sleeping and living rooms are distributed. A

substantial contribution to the zero-emissions target is met by

having very good insulation, with a stainless steel outer skin and 7

insulation layers in the walls and triple glazed windows. Passive

heating is also an important energy saver because it recycles the

heat produced inside the building.

The interested reader should refer to the Comprehensive Envi-

ronmental Evaluation CEE report [1] fora broader description of the

scope of the base and its design particularities. A dedicated website

(http://www.antarcticstation.org) is also available for the follow up

of the station activities.

1.2. The integrated building design process

The Princess Elisabeth base was designed by the International

Polar Foundation (IPF). An integrated building design approach was

followed whereby multiple design disciplines were assembled

from the beginning of the project to obtain a highly synergic design

that allows optimizing the performance and ef ciency of the

building. This kind of approach is the state of the art in building

design and it is being adopted in singular buildings or building

complexes where high levels of energy ef ciency and sustainability

are pursued.

A key to successful integrated building design is the early

participation of experts from different specialties: civil engi-

neering, architecture, interior and landscape design, energy and

wind engineering, etc. The early collaboration among them

allows nding opportunities at conceptual level that can produce

a very signicant impact in the nal performance and cost of the

design.

In the Antarctic integrated building design process, wind engi-

neering (wind and snowdrift assessment) and energy ef ciency

lead decisions about the optimal positioning, orientation and shape

of the building. The integration of renewable energies and opera-

tional aspects like the positioning of entrances, emergency exits or

snow collection facilities (for water consumption) are also deter-

mined after careful assessment of the environmental conditions of

the building envelop.

The aerodynamic design of Princess Elisabeth station had three

phases: the conceptual design phase, the building envelop design

and the optimization phase. In the conceptual phase, the designers

had to decide about the optimum building typology by trading off basic design parameters on a number of building-block concepts.

Once the basic typology was selected, the building envelope was

shaped and positioned on the ridge considering both internal

constraints (internal layout and system integration) and external

environmental aspects. From the wind engineering point of view,

snowdrift control and wind loading had to be tested in order to

assess the aerodynamic performance of different building proto-

types and ridge integration alternatives. Finally, an optimization

phase looked at more detailed elements of the building like, for

instance, localized forces on the corners of the building or the

integration of the under-snow garage.

1.3. Wind engineering strategy

Wind engineering constitutes a crucial aspect in the design of

modern Antarctic bases [3]. Not only for safety and cost reduction

but also for the integration of renewable energies, important

benets in the design of a building can be achieved if wind engi-

neering is part of the integrated building design process since the

very beginning.

Fig. 1. Sketch of the building and its integration in the ridge.

J. Sanz Rodrigo et al. / Building and Environment 52 (2012) 1e182

http://www.antarcticstation.org/http://www.antarcticstation.org/


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All modern buildings have undergone aerodynamic studies at

different stages of their design. Delpech et al. [4] simulated the

snowdrift around Concordia station using real snow in a climatic

wind tunnel. Waechter and Williams [5] used water ume and CFD

modeling of snowdrifts to support the design of a new building for

the Amundsen Scott base at the South Pole. Beyers and Harms [6]

made eld tests of snow accumulation in the vicinity of SANAE IV

station using a reduced scale model of the building. Leitl et al. [7]

performed wind tunnel simulations of Neumayer III station on

snowdrift and wind loading. The design of the new Halley VI station

has also been supported with CFD simulations (not published).

The wind engineering aspects of Princess Elisabeth station were

tested at the von Karman Institute L1-B wind tunnel with support

from numerical CFD models at different stages of the design. This

paper will only deal with the experimental part. Information about

the numerical aspects can be found in Ref. [2].

Snowdrift modeling in wind tunnel is a dif cult task due to the

inherent impossibility to maintain similarity of all the driving

forces. It is also very costly and time consuming as it takes several

hours to develop signicant build-ups. As a result, it was not

feasible to use this technique in the very demanding conceptual

design phase, where many building congurations had to be tested

in a very limited amount of time. Instead, the sand erosion tech-nique proved to be a cost-effective solution to evaluate the wind

conditions at ground-level and, at the same time, identify snow

accumulation and erosion regions. The application of this technique

to snowdrift assessment is published on this paper forthe rst time.

The sand erosion technique allowed the evaluation of six

different building-block concepts with several ridge integration

strategies. Prismatic blocks were used in order to offer the best

perspective for a systematic comparison of the different design

concepts. Two block concepts offered similar aerodynamic perfor-

mance: a square-based one-storey building or a rectangular-based

two-storey building aligned with the wind direction.

After a site visit during Belare-2005 expedition, IPF selected the

location on the ridge offering the best conditions for anchoring and

accessibility. It also turned out that a one-storey building would bepreferable for a better compatibility with the internal layout of the

building, which would be based on a concentric architecture

around a technical core reserved for the system installations. The

square-based model had better compatibility with this concentric

concept than the rectangular-based concept. Hence, it constituted

the reference for the building envelop design phase in which the

square building would be shaped and positioned to obtain better

aerodynamic performance.

The reference building-block was instrumented with pressure

taps to measure wind loading at different building-ridge integra-

tions. A parametric study showed that the height of the building

legs and the positioning across the ridge were sensitive parameters

for both aerodynamics and snowdrift control.

While elevating the main building with legs solves the problemof snow accumulation, it might generate problems of snow erosion

around the under-snow garage. Hence, dune visualization tests

were performed to check the impact of the snow erosion generated

by the building on the integrity of garage.

Several evolutions of the envelop design were tested until the

adoption of a nal one, whose aerodynamic performance was again

tested with pressure taps to assess the nal loads and to optimize

the nal positioning on the ridge. During this phase, wind tunnel

testing also revealed some aerodynamic aspects of the garage roof,

which could be used as a diffuser to modify the wind loading on the

building.

These wind tunnel testing phases will be summarized in this

paper. The test case shows how wind engineering can aid the

integrated building design process and the bene

ts of considering

these aspects from an early stage.The originality of the test case can

be focused on the study of the inuence of the ow under the

building on the aerodynamic aspects of the building. Elevated

buildings on pillars are the typical design solution in snow regions

to cope with snowdrifts but they are typically placed in at terrain.

Having sloping terrain under the building makes the building

aerodynamics less predictable. It is shown in the paper that by

carefully positioning the building on top of the ridge important

reductions in wind loading and snowdrift can be obtained.

2. Experimental setup

2.1. Wind tunnel site and ABL model

A model of the southern part of the ridge topography at a scale

1:100 was built and installed at the 2.8 m diameter turning table of

the VKI L1-B atmospheric boundary layer wind tunnel (Fig. 2, left).

The wind tunnel is of the close-circuit type, equipped with two

contrarotating fans of 580 kW that forces wind speeds up to

6 0 m s1. The rectangular wind engineering test section is 2 m high,

3 m wideand20 m longwith a roughedoor to allow the growth of

a turbulent boundary layer similar to the lower part of the atmo-

spheric boundary layer (ABL).

The site topography is made of 3 mm thick wooden layers

smoothed up with high denition plaster within the steps. Of

course, the model represents both the ridge and the snow surface

as it was found in Antarctica. Once the building is situated on top of

the ridge, the snow surface behind it will change under the action

of the erosion and deposition generated by the building.

Since no Coriolis forces and thermal stratication can be

reproduced, the test section is suitable for the characterization of

the surface boundary layer in neutral conditions. This is suitable for

the purposes of this investigation since we are interested in

snowdrift and wind loading at high wind speeds in the rst 20 m

above the ground. At low wind speeds the Antarctic boundary layer

is characterized by stable stratication due to a quasi-permanent

temperature inversion due to radiative cooling.The incoming surface boundary layer is modeled in the wind

tunnel using a 20 m rough oor that reproduces the logarithmic

wind prole according to Monin Obukhov theory:

U ¼ u*k

ln

z

z 0

(1)

where u* ¼ ffiffiffiffiffiffiffis=r

p is the friction velocity, s is the shear stress, r is

the air density, k ¼ 0.4 is the von Karman constant, and z 0 is the

roughness length. Beyers and Harms [6] also used this logarithmic

prole to t measurements in the vicinity of SANAE IV station. The

effective roughness height above snow covered terrain is propor-

tional to the saltation layer thickness, which varies with the square

of the friction velocity.

z 0;eff ¼ C 1u2*

2 g (2)

where g ¼ 9.8 m s2 is the acceleration of gravity and the constant

C 1 depends on the snow properties. Beyers and Harms [3] present

values from different authors ranging from 0.035 to 0.12. The

effective roughness is low for wet snow and high for fresh snow

cover after snowfall. At SANAE IV they found a value of 0.0035 over

wet snow for friction velocities above 0.4 m s1. The effective

roughness height was between 2.8$105 m and 1.8$104 m for

friction velocities ranging from 0.4 to 1 m s1 respectively. For dry

uncompacted snow the saltation layer and roughness height will be

higher. Considering the upper limit of C 1 for high effective

J. Sanz Rodrigo et al. / Building and Environment 52 (2012) 1e18 3


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roughness conditions, the values of z 0 can range between 104 m

and 6$103 m for the same range of friction velocities. Therefore,

the variability of the effective roughness length can be quite large,

although always very low, as it depends on the snow properties and

the friction velocity.

The sensitivity associated to the ABL is assessed by testing two

ABL classes: Class I or ‘smooth ABL ’ ( z 0 ¼ 2$104 m, 7% turbulence

intensity at building height, in full-scale units), close to the ex-

pected site conditions, and Class IV or ‘rough ABL ’ ( z 0 ¼ 0.4 m, 20%

turbulence intensity at building height, in full-scale units), typical

of the urban environment. The class I boundary layer is obtained by

removing the roughness elements of the class IV boundary layer.

The urban boundary layer is of course an unrealistic extreme casefor Antarctica but it is interesting to check the sensitivity of the

building aerodynamics to the incoming wind prole since the

incoming ABL is not known a priori. Nevertheless, it is expected

that snow erosion and deposition will be dominated by the

disturbance generated by the building rather than by the incoming

ow conditions.

2.2. Wind climate from onsite AWS data

An automatic weather station (AWS) was placed at the south-

ernmost edge of the ridge since December 2004. During the winter

2005, a station malfunction resulted in loss of measurements

between the 2nd of July and the 14th of August. Nevertheless, the

annual data availability is suf cient to assess the local wind climatethroughout the year 2005, with an annual 4-m mean velocity of

5.9 m s1 and a prevailing wind direction sector from E to SSE. The

most energetic wind direction is E with 90% of the energy

content (Fig. 3). A CFD simulation of the mean ow from this wind

direction results in the 4-m high speed-up contour map of Fig. 2

(right) with respect to the AWS mean velocity. It is observed that

the building area in top of the ridge has 20% higher wind speeds

than the ones observed at the AWS position.

The estimatedmean velocity is ratherlow due to the presence of

nearby Utsteinen and the Sor Rondane Mountains to the S-SE, that

shelter from the intense katabatic winds of the region. Wind speed

measured at Asuka Station between 1986 and 1991, 60 km north-

east, were twice as high due to a more exposed site to the katabatic

winds.

Even though the mean wind speed is not high, the site is char-

acterized by the presence of intense wind storms, especially during

the winter season. This is revealed by an annual velocity distribu-

tion with a long tail characterized by a Weibull shape factor of 1.35.

2.3. Snowdrift assessment: sand erosion tests

The presence of strong winds in Antarctica is responsible for the

transport of large quantities of snow in the form of snowdrifts,

producing a variety of operational problems around buildings and

structures.

It is normal practice in Polar Regions to use elevated buildings as

they can passively remove the snow through the window passingunder the building. Almost all modern stations use this basic

principle in their design. Some of them like Halley V, where the

snow accumulation rate is 1.5 m per year, even include jackable legs

to adapt to the progressively higher snow level.

The size of the building generated snowdrifts will depend,

among other factors, on the height of the pillars and the orientation

of the building against the wind. General guidelines about snow-

drifts around prismatic buildings on at terrain can be found in

Refs. [8,9]. Elevated buildings present smaller snowdrifts by

increasing the height or the length of the building in the direction

of the wind. On the contrary, increasing the width perpendicular to

the wind direction increases the size of the snowdrifts. Kwok et al.

[10] studied the optimum spacing between groups of buildings in

order to minimize snowdrift. Kwok and Smedley [11] studied theeffect of the corner geometry and the wind incidence on the

snowdrift size. A very signicant reduction in snowdrift is obtained

by chamfering or rounding the corners with respect to a sharp-

edged building model. Hence, the chamfer should be as large as

the internal layout allows. Irrespectively of the corner geometry

they also recommended to align the building with the main wind

direction and use longer pillar heights to reduce the volume of the

snowdrift. Chamfering the corners is also a well known technique

to decrease wind loading on the building facades.

In the case of Princess Elisabeth base, the presence of the ridge

sticking out of the snow surface constitutes a particular situation in

which the wind speed-up generated between the building and the

ridge can be used to enhance the snow removal ef ciency of the

building, allowingfor theuse of shorter pillars.The same principleis

Fig. 2. Topographic model of the ridge at a scale 1/100 in the L1-B wind tunnel (left) and Eastern speed-up contours at 4 m with respect to the AWS velocity (right).



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used in the new AmundseneScott base in the South Pole, where the

bottom edge of the building facing the wind is shaped like an airfoil

to accelerate the ow and increase the erosive action on the snow.

The snow drifting process is described in detail in Ref. [12]. The

requirements for wind tunnel modeling of snowdrifts around

obstacles can be found from different authors [9,13e

15]. Geometricsimilitude of snowdrifts is fullled if the model and prototype windelds are similar because the snowdrift development is driven by

the wind shear stress. Hence, standard wind engineering require-

ments can be adopted to obtain ow similarity [16]. Apart from

scaling the topography and building geometry and the ABL prole,

In the case of bluff body aerodynamics it is standard practice to

assume ow similarity when a fully turbulent regime is attained,

which is achieved with Re > 104.

Testing the snowdrift development rate requires length exper-

iments at low wind speeds in order to avoid too much Froude

distortion [9]. Since the interest of the design process was rather on

the comparison of different building typologies, in the conceptual

and envelope design phases, than on the prediction of the amount

of snow build up, partial snowdrift modeling was adopted. Thealternative model is based on the sand erosion or scour technique,

which is used in wind engineering studies related to the assess-

ment of the wind comfort around buildings [17e19], i.e. the

prediction of the occurrence of high level winds at ground (i.e.

pedestrian) level in the urban environment.

The test procedure is straightforward. A thin layer of sand

(w3 mm) is spread all over the oor of the test section. A uniform

freestream velocity is set in the wind tunnel for a certain time

(1 min) such that a quasi-steady erosion contour is obtained. This

contour indicates lines where the friction velocity reaches the

threshold for saltation. By increasing the freestream velocity in

progressive steps (from 5 to 13 m s1 in steps of 0.5 m s1),

a family of contours is obtained, each one associated to a particular

value of the freestream velocity and the same value of the local

(threshold) friction velocity. A picture is taken from the top at the

end of each time step and a contour detection algorithm extracts

the contours that are gridded to obtain a contour map of erosion

wind speeds.

Even though some advances have been made in the quanti-

cation of the sand erosion tests as a measurement of the shearstress [20,21], the technique is still mostly used as a visualization

tool in order to spot areas with high or low skin friction. Livesey

et al. [18] compared thewind speeds inferred from the sand erosion

technique with those measured with a hot-lm anemometer. He

found that the sand erosion measurement, rather than the mean

speed, was related to the gust speed, dened as the mean plus one

standard deviation. Nevertheless, the wind speeds inferred had

considerably large variability. As a result, it was concluded that the

technique was suitable to identify areas of high relative winds and,

as such it shall be used in comparative studies. This capability will

be used in the present context to infer the action of the building on

the snow surface around it by comparison with the situation

without the building and, as a result, distinguish areas of snow

deposition and erosion. Therefore, the sand erosion technique isperformed in two steps: rst without the building (reference case)

and then with the building model at the position and orientation of

interest.

Being the erosion contours related to a gust factor [18] the

contours never reach a steady state shape because they are all the

time eroded under the action of turbulence gusts. Nevertheless, in

the rst minute after a change in the freestream velocity, the largest

changes are produced as a result of the new mean wind speed [21].

Therefore, the contours recorded during the test are assumed to be

contributed mostly by the mean wind speed.

Once the two erosion speed contour maps are obtained, the

ratio between both will reect an amplication factor, Ae,

a measure of the action of the building on the reference or back-

ground

ow

led:

Fig. 3. AWS wind speed and direction distributions (JJA corresponds to summer season and DJF to winter season).



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Ae ¼ U 0U b

(4)

where U 0 is the erosion wind speed from the building-free case and

U b is the erosion wind speed from the building case. That is, Ae > 1

implies a relative increase of the wind shear and Ae < 1 a decrease

of the wind shear. Then, in areas where Ae is equal or close to 1, the

building does not change the background surface wind ow.

The sand, as the snow, is eroded when the shear stress of thewind acting on the ground exceeds a certain threshold. This

condition is satised, in the case of the sand employed in this study,

fora thresholdfrictionvelocity of 0.23 m s1. The contoursobtained

from the sand erosion patterns delimit the positions at which the

friction velocity is near the threshold value, separating the erosion

(friction velocity higher than the threshold) from the deposition

areas (friction velocities bellow the threshold) for a given velocity.

According to Anno [14] “the geometrical similitude of a border line

between the eroded area and the deposited area constitute the

most important similitude in the modeling of a snowdrift since the

snowdrift would be formed as a combination of erosion and

deposition”. Hence, provided that the ow similitude parameters

are satised, the extension of the snow deposition areas will be

delimited with the contour at which the local friction velocityequals the threshold friction velocity. The scaling of the snowdrift

areas is directly related to the ratio of friction velocity to threshold

friction velocity (u*/u*t , ratio between the wind shear stress and the

particle cohesive forces). Hence, the scale factor between the eld

velocity and the wind tunnel velocity is directly the ratio of

threshold friction velocities:

u* ¼ u*; WTu*t

u*t ;WT; U ¼ U WT

u*t u*t ;WT

(5)

where the subscript WT denotes wind tunnel parameters.

The threshold friction velocity of the snow in the led is dif cult

to predict and ranges between 0.1 m s1 for dry uncompacted snow

and 0.4 m s1 for wind hardened snow [22]. Li and Pomeroy [23]

found threshold 10 m wind speeds ranging from 7 to 14 m s 1 forwet snow and from 4 to11 m s1 for dry snow using meteorological

data from 16 stations in western Canada. Beyers and Harms [6]

found a threshold 10 m wind speed of 8 m s 1, equivalent to

a threshold friction velocity of 0.28 m s1, from prole measure-

ments at SANAE IV base (Droning Maud Land, Antarctica). Mann

et al. [24] analyzed particle counter prolesof snow at Halley (Coats

Land, Antarctica) and found threshold friction velocities in the

range 0.22e0.36 m s1, depending on the time since the last

blowing snow deposition. Hence it seems that an average value of

0.3 m s1 can be assumed for the threshold friction velocity of the

snow in Antarctica. Since it is 30% higher than that of the sand

particles used in the sand erosion tests, it means that the eld

velocities will be scaled by a factor 1.3 of the wind tunnel velocities

according to Eq. (5).Of course, the sand erosion technique is a surface visualization

and does not provide information about the development rate of

the height of erosion or deposition. Therefore, the comparisons

between the different building typologies will be based on the size

of the areas with Ae < 1, as an indicator of the ef ciency of the

building to accumulate snow. Considering a typical threshold wind

velocity for snowdrift of 5 m s1 at 4 m in the AWS position, 91% of

the snowdrift will come from the sector E-ESE (63%) and SE-SSE

(28%) sectors. Two prevailing snowdrift directions where selected

for testing during the design phase: 101 and 145. The rst one is

the most energetic and will bring the largest contribution to

snowdrifts as it is noticed from the snow patterns behind the ridge.

Fig. 4 shows some examples of photos obtained from erosion

tests. The wind speed is progressively increased from the top

(6 m s1) to the bottom (12 m s1). The left column presents the

building-free test which is used as a reference to compute the

amplication factor. The middle and right columns show two

erosion tests for a rectangular building, situated on top of the ridge

with two orientations: parallel and perpendicular to the incoming

wind direction (145). The building in both cases is elevated from

the ground leaving a clearance of one (full-scale) meter between

the building and the top of the ridge.

The areas out of the inuence of the building present similar

erosion patterns to the building-free case. The small differences are

due to the inherent lack of repeatability of the manual sand

spreading process. Nevertheless, the reproducibility of the erosion

tests is quite good, with uncertainties on the erosion velocities

bellow 0.5 m s1.

At low erosion velocities, the rst erosion patterns appear near

the corners and bellow the building, where the turbulence and

wind speed-up are the highest. At high velocities, only the sand in

the best sheltered areas remains. These areas will have good wind

comfort butwill also build up snow.As expected, when the building

is oriented perpendicular to the prevailing wind direction, the

snow accumulation areas are increased both behind and in from of

the building. The accumulation in the back is not so problematic if

there is some space left between the building and the snowdrift,where the main entrance would be placed. The snowdrift accu-

mulated in the front is more risky as it will progressively block the

ow underneath the building creating more build up in the back.

2.4. Garage integration: dune formation tests

The surface erosion tests are very helpful in the analysis of the

wind conditions at surface level but they do not offer much infor-

mation about the vertical development of erosion or deposition. As

the elevated building concept seems to have the snow accumula-

tion problem under control, it was important to assess the effect

that the building aerodynamics would have on the snow erosion

around the under-snow garage, situated just behind the main

building. Aerodynamically speaking the garage roof serves asa platform that avoids the development of too large snow erosion in

the vicinity of the main building, providing a more stable ground to

give access to the building from the West.

To study the garage integration, an 80 cm wide portion of the

wooden ridge model was removed from the lee side at the location

of the building. A vertical cut of 8 cm, following the rock prole asit

was found on the site, gives room for the accommodation of

a 45 11 5 cm3 garage. The height between the garage roof and

the ridge top was kept at 1 m in full scale. The empty space left waslled up with sand plus an additional centimeter to cover the

garage entirely. This situation constitutes the setup for the dune

formation visualizations. These testsare done, similar to the surface

erosion tests, at progressively increasing speeds but now the time

for each velocity step is extended to 5 min to account for the longerdevelopment of the dune patterns. The edges of the cut have been

placed suf ciently far away from the action of the building, making

use of the results from the sand erosion tests. This will ensure that

the dunes are only driven by the action of the wind and not by the

presence of extra vorticity from the edges of the cut. Interestingly,

at the end of the experiments the erosion patterns show a smooth

transition from the snow bed to the wooden proles at the edges.

Since these proles are obtained in real scale by erosion and

deposition generated by the ridge alone, this can be considered as

a good indication of the similarity of the snow erosion patterns in

the wind tunnel. In fact, by measuring the snow surface topography

before and after the construction of the station, Pattyn et al. [25]

conrmed that, apart from the immediate vicinity, the building

has a limited effect on the patterns of snowdrift behind the ridge.



7/18

The sand bed is very erodible, compared with the wind hard-

ened snow and ice bed, so the results cannot be directly related to

the eld conditions. As with the erosion tests, the dune formation

test can be used to qualitatively compare the relative difference

between different building congurations.

2.5. Wind loading assessment: pressure taps tests

To study the building-ridge integration from the wind loading

point of view, a model of the reference and nal building models

was manufactured with a distribution of pressure taps to map the

pressure acting on the building skin (Fig. 5).

The number of pressure taps was limited by the size of the

evacuation bridge situated in the back of the building, through

which all the 1 mm diameter tubes had to pass in order to reach

three scanning valves situated under the wind tunnel. The low

frequency response of the tubing only allowed the measurement of

mean pressures for the characterization the mean wind loading.

Uematsu and Isyumov [26] state that, when the characteristic

dimension of the building is small compared with the turbulence

integral scale of the incoming winds, the maximum load effects can

be evaluated using a quasi-steady approach. This is the standard

practice of many codes, like the Eurocode [27] or the Japanese AIJ

[32] recommendations, which deduce the design load from the

mean pressure

eld. It is also convenient when the turbulence

eld

Fig. 4. Example of erosion tests: Building-free test as reference (left column), rectangular building oriented along the incoming wind direction (middle column) and perpendicular

to the incoming wind (right column). The wind direction (145 ) is indicated with an arrow.



8/18

is unknown, as in the present case. The quasi-steady method

assumes that the pressure uctuations on the building are fully

correlated with the velocity uctuations, i.e. the maximum pres-

sure will appear at the maximum velocity peak. Then, the designpressure is calculated by multiplying the mean pressure coef cient

with the peak dynamic pressure calculated with the extreme

(design) wind velocity. This approach fails when the building

generated turbulence, at separation regions, contributes signi-

cantly to the pressure uctuations. This building generated turbu-

lence has smaller scales that can be important for small elements

on the skin of the building. As a result, the quasi-steady approach

can be safely used to calculate design loads for the main structure

or for large elements of the building but not for localized small

elements.

Tieleman et al. [33] conclude, in their review of the wind tunnel

requirements for wind loading assessment of low-rise buildings,

that the incoming wind prole does not inuence the mean pres-

sure coef

cient. It is more important to match the incoming hori-zontal turbulence intensities if one is interested in reproducing well

the uctuations of the pressure coef cients. The independence of

the mean pressure coef cient with the incoming turbulence was

also demonstrated in Ref. [28]. Hence, the uncertainty associated

with the incoming boundary layer conditions might not be that

important for the modeling of the mean pressure eld. Neverthe-

less two limiting classes of neutral ABL were tested in order to

verify this hypothesis.

The mean pressure coef cient is dened according to the

incoming dynamic pressure at freestream level:

Cp10 ¼ D p

1

2rU 2AWS

(6)

where D p is the measured mean pressure relative to a common

undisturbed reference outside the wind tunnel, r is the air density

and U AWS is the reference wind speed velocity measured at the

AWS position. Notice that the AWS is located at a lower elevation

than the building of around 10 m. The subscript 10 is used in

accordance with the Eurocode [27] to stand for global pressure

coef cient, to be used for structural design, or local pressure

coef cient for surfaces greater or equal to 10 m2. The AWS position

is used as a reference for the wind speed because it can be related

later with the eld measurements to obtain the design dynamic

pressure:

D p50 ¼ Cp101

2

rU 2AWS;50 (7)

where U AWS,50 is the design velocity estimated using extreme value

analysis at the AWS position. The mean yearly air density measured

at the site is 1.13 kg m3.

The overall forces acting on the building are obtained by inte-gration of the mean pressure coef cients on the building facades.

The force coef cient along i axis, CF i, is dened as follows:

CF i ¼ F i

1

2rU 2AWS Ai

(8)

where Ai is the frontal area perpendicular to the incoming wind

direction along the i axis.

3. Conceptual design

The conceptual design of the base started from the selection of

a number of block geometries, with the least detail level, offering

the best perspective for a systematic comparison of the designprototypes. Six different block concepts were selected for testing

during the conceptual design phase, all of them with the same

living area. The differences between them were on the shape of

the base (square or rectangular), the number of storeys (one or

two) and whether the building was integrated on the ridge or

elevated. Several wind incidences and ridge positions were

tested.

3.1. Selection of reference building-block concept

Fig. 6 shows three models, made of transparent plexiglas to

look through, that provided similar performance from the

snowdrift point of view (two building orientations are tested).

Two other building concepts integrated on the ridge presentedsnow accumulation areas next to the building, indicating prob-

lems of accessibility [3]. It is clearly noticed the impact of the

building orientation on the winds at surface level. When the

rectangular two-storey building is placed perpendicular to the

incoming wind it presents a much larger obstruction to the ow

and generates higher speed-ups (erosion areas) and also larger

areas for snow accumulation in the from and in the back of the

building. When the frontal area is minimized by aligning the

building with the wind direction, the snow deposition area is very

much reduced, as indicated by Kim et al. [8] in at terrain

conditions.

The square-based buildings present similar snow accumulation

areas. The orientation at 45 seems to present fewer problems for

snow build-up in front of the building.

Fig. 5. Reference (left) and nal (right) building models instrumented with 133 and 159 pressure taps respectively.



9/18

The rectangular model presents the smallest snowdrift area of

the three models, when it is aligned with the incoming wind. Inthe other hand, it is also more sensitive to the wind direction

variability. Therefore it was concluded from these tests that the

three concepts had similar performance with respect to snow.

Hence, the selection of the building typology to follow the design

process could be left to other design criteria. Because of an easier

construction and a better compatibility with the internal layout

the elevated square-based and one-storey building model was

selected.

A 20 20 5 m3 square-based model, selected in the

conceptual phase, was modied with 2 m depth chamfered at the

four vertical edges and 1 m depth chamfer at the top and bottom

edges, to offer much better performance in reducing snowdrifts, as

it was observed in Ref. [11]. This model shall constitute the refer-

ence for further optimizations of the design.

3.2. Building-ridge integration

After Belare-2005 expedition to Antarctica, IPF selected the area

with the best terrain conditions for the anchoring of the building.

This area is situated some 40 m north of the previously selected

area for the erosion tests presented in Fig. 6. The positioning of the

building on the ridge is constrained by the anchoring conditions on

the rock, which are more dif cult at the lee side of the ridge due to

an almost vertical slope. Therefore, the building can be better

positioned with the back side on top of the ridge and some canti-

lever upstream.

Fig. 7 presents a sensitivity analysis of the amplication factor

versus the integration of the reference building, considering the

height of the clearance and the position acrossthe ridge. In the top-

left gure, the building is at a reference position X 0 and is elevated

1 m from the top of the ridge. When the building is lifted to 2 m at

Fig. 6. Amplication factor contours for models oriented parallel (left) and at an incidence angle (right) to the incoming wind direction from SE þ 10.



10/18

the same position (top-right gure), the deposition area is reduced.

In the contrary, if the building is moved backwards by just 2.5 m

(bottom-left gure), the snow deposition area is signicantlyenhanced. This situation is partly alleviated if the elevation is

increased to 2 m (bottom-right gure).

The positioning of the building across the ridge appears to be an

important aspect for controlling snow accumulation and erosion. A

building with larger windward cantilever offers more speed-up

underneath producing more aggressive erosion behind the

building. When the building is shifted backwards, the ow nds

more resistance to go under it and deviates more to the sides

producing less erosion behind the building. In both situations

elevating the building improves the erosion. It will be explained

later how the positioning of the building also affects the wind

loading as both aspects are controlled by the drag of the building-

ridge conguration.The building at 45 incidence has a “delta wing” conguration

generating more vorticity and hence more erosion than the

building aligned with the incoming wind direction [3]. This was

also concluded by Beyers [31] from numerical CFD simulations of

the snowdrifts around SANAE IV station.

The wind loading on the building will be also inuenced by its

positioning on the ridge. To study the building-ridge integration

from the wind loading point of view, a model of the reference

building model was manufactured with 133 pressure taps to map

the pressure acting on the building facades.

Fig. 7. Amplication factor contours for the reference building model. Sensitivity to elevation height and across-ridge positioning.

Fig. 8. Mean pressure coef

cient at reference position, with 1 m clearance and wind incidences 0

(left) and 45

(right). The wind direction is 101

parallel to the X axis.



11/18

Fig. 8 shows the mean pressure coef cient distribution

throughout the building facades, obtained by linear interpolation

in the top and bottom faces and by nearest neighbor interpolation

in the rest, for two wind incidences: 0 and 45. The positioning of

the taps is also indicated. The typical pressure build-up in the

stagnation area of the frontal face is depicted as well as the high

suction in the separation region at the leading edge of the top

surface. The latter is much higher for the building oriented at 45

wind incidence due to the formation of “delta wing” vortices,

similar to the situation of ground-based buildings with at roofs

[28].

The pressure map at the top surface does not vary much with

the positioning of the building. The high suction generated at the

leading edge is increased at higher building elevations. This is due

to the higher surface velocities that create larger suction, as it is the

case for ground-based buildings [29]. A slight decrease in the top

surface suction is observed when the building is positioned back-

wards, probably due to lower local velocities. Large suction areas

occur very close to the roof edges in the upwind corners and is

typically alleviated using parapets [30]. Unfortunately this remedy

will also create snow accumulation on the roof and thus it is not

a good solution in this case. Due to the sloping terrain, the wind

approaches the building with a small up-ow angle. Hence, a smallnegative inclination of the roof would decrease the relative up-ow

angle, reducing the ow separation area and decreasing the overall

lift on the rooftop.

The most interesting results happen in the bottom surface,

where the ow interacts with the building and the ridge. Here, it

can be noticed a positivepressure at the leading edge due tothe up-

ow generated by the sloping terrain. Then, the pressure turns to

negative, due to the speed-up generated by a convergent clearance,

as the ow approaches the ridge top. At the ridge top the speed-up

and the suction reaches a maximum value which is then decreased

by a divergent clearance at the rear of the building.

Fig. 9 shows the effect of the clearance height on the pressure

distribution on the bottom surface. The left column shows the

sensitivity of the pressure distribution to the elevation height,when this one is set to 0, 1 and 2 m. The right column shows the

sensitivity to the across-ridge positioning of the building, when this

one is placed 3 m backwards, at the reference position ( X 0) and 3 m

forward.

When the building sits in top of the ridge (Fig. 9, top-left) a high

blockage is created on theow under the building, which generates

high pressure build-up and a net positive lift force on the building.

The lift force is two times higher than the one obtained with 1 m

clearance. Using a clearance of 2 m (Fig. 9, bottom-left) instead of

1 m further decreases the lift force. Even though the lift force is

counteracted with the self weight of the building, a positive aero-

dynamic lift will lead to vibrations on the structure, so it should be

avoided. Owing to the ridge slope, the elevated building concept is

not only a good solution to decrease snow deposition but alsoa more convenient conguration from the aerodynamic point of

view.

The sensitivity of the positioning of the building across the ridge

is also quite remarkable. The highest suction on the bottom face is

alwaysgenerated at the ridge top, where theowaccelerates due to

the contraction of the clearance. The larger the area situated at the

ridge top the higher the suction on the bottom surface and,

therefore, the lower the overall lift force on the building.

4. Building envelope design

Once the reference concept has been developed, the building

envelope evolves with the integration of the interior layout and the

technical systems. At this stage of the process, the internal layout

becomes the main design driver of both the internal and external

geometry of the base.

The aim for a modular base, which would allow easier

manufacturing and transportation, lead to an octagonal building.

From the aerodynamic point of view, this geometry could be

considered as an intermediate case between the square building at

0 and 45 wind incidence. The integration of solar panels also

required an inclination of the side walls of 30 for a more ef cient

energy capture. The accommodation of some units of the system in

the center of the building required some extra space, which was

found by adding a second storey that sticks out of the roof. This

add-on would also be used to give access to the roof and to

accommodate some more solar panels.

The new building envelope was tested using sand erosion tests.

Fig. 10 shows the amplication factor erosion maps obtained for the

octagonal building with the same congurations of Fig. 7 for the

reference building. At rst glance, it is clear that the new geometry

is much more effective at removing snow.Indeed, the building in its

back position and with an elevation of 2 m removes almost entirely

all the deposition area situated behind the building, leaving only

the two deposition tails delimiting the building wake.

Theerosion strength is bettervisualizedwith dune tests (Fig.11).

The visualizations reveal the formation of two dunes delimited atboth sides by erosion streams originated by the interaction of the

vortex shedding from the edges of the building with the wake of the

building. The two most external erosion streams are generated by

the corner vortices generated at the front of the building. The third

erosion stream, in between thetwo dunes, isattributed tothe vortex

shedding from the trailing edge of the building, where the ow

passing underneath meets the low pressure in the wake. These two

vortex streams arevery intense at the exit of thebuilding producing

very intense wind shear that removes the sand on top of the garage

roof very early in the erosion tests. The intensity of these vortices

depends again on the speed-up generated under the building and

hence on the building-ridge positioning.

The dune formation tests are consistent with the surface erosion

test: the erosion strength is more important when the building iselevated or is moved forward. Even with the very erodible sand bed

it seems that the garage integrity is preserved because the erosion

does not expose the garage too much in the reference building. In

the other hand, the octagonal building presents much deeper

snowdrifts. In effect, by reducing the surface in the back of the

octagonal building the suction created at the ridge top is acting on

a smaller area and the overall lift force is increased. This V shape at

the exit of the clearance also enhances the vorticity which is the

responsible for the strong erosion streams just behind the building.

To cope with potential erosion problems and lift forces, the back

of the building was modied back to its original extension, still

leaving the inclined walls for the solar panels. Dune formation tests

on this new building envelope are shown in Fig. 11 (right). It is

remarkable the important effect of the geometry at the back of thebuilding on the erosion patterns. The larger area on top of the ridge

attenuates the trailing edge vorticity decreasing the erosion very

signicantly.

The new building geometry was considered denitive and no

mayor changes were done on it. As with the reference building,

wind loading tests were also conducted to verify the sensitivity of

the nal geometry on the building positioning.

5. Design optimization and nal assessment

A model of the nal building geometry, obtained at the end of

the envelope design phase, was instrumented with 159 pressure

taps in order to assess the nal wind loading specications (Fig. 5).

This time, the positioning of the pressure taps wasdeterminedfrom



12/18

CFD simulations of the pressure distribution on the skin of the

building. By using CFD, the uncertainty on the global forces due to

tap resolution was reduced from 30%, in the reference building

when CFD simulationswere not available, to 3% in thenal building

model. The positioning of the taps and the associated uncertainty

was estimated by comparing the integrated CFD forces obtained

from all the grid cells of the skin and based only on the cells of the

tap positions. The garage was also included in the nal wind

loading tests. The height between the garage rooftop and the ridge

was another parameter to be tested.

Fig. 9. Mean pressure coef cient in the bottom face of the reference building. Sensitivity to elevation height and across-ridge positioning. The axes grid size is 10 m. Wind direction

is 101 aligned with the building, from right to left.



13/18

Fig. 11. Dune formation tests for the reference building (left), octagonal building (center) and nal building (right) at X ¼ X 0 2.5 m and 2 m pillars height. The wind direction is

101

, parallel to the building.

Fig. 10. Amplication factor contours for octagonal building with inclined walls. Sensitivity to elevation height and across-ridge positioning.



14/18

Fig. 12 shows the pressure eld on the nal building geometry,

this time using linear interpolation in all faces because of the better

repartition of the pressure taps. The

nal geometry offers a signif-icant reduction of drag force due to a more aerodynamic shape in

the front.

Again, building-ridge integration was studied for the nal

geometry. Fig.13 shows the effectof the elevation of the building on

drag and lift coef cients for different across-ridge positions in the

reference building and the nal building, which is always situated

in the backwards position ( X 0e3 m).

The sensitivity to the incoming ABL is also studied, with

measurements using the smooth (snow type) and rough (urban

type) test section. The effect on the lift and drag forces are indeednot signicant in agreement with similar studies [28,33]. However,

the nal geometry offers 40% reduction on drag with respect to the

reference building, due to the aerodynamic frontal shape. The drag

decreases a further 20e30% as the building moves backwards due

to the effect of a smaller building-ridge wake.

The high positive lift force is also signicantly decreased when

the reference building is shifted backwards due to the larger

Fig. 12. Mean pressure coef cient on nal building model from pressure taps.

Fig. 13. Lift (left) and drag (right) coef

cients for the reference and

nal building models. Effect of clearance height, across-ridge positioning and incoming ABL.



15/18

suction on the bottom surface. For the same reason, when the

clearance height is increased, the lift force decreases.

Therefore, the elevated building is not only a good solution to

cope with snow accumulation but also a more convenient cong-

uration, from the structural point of view, in this particular situa-

tion in which the building is installed in sloping terrain. Above 2 mthe decrease in lift force is not very signicant, so it seems to be

a good choice for the pillars height, also providing comfortable

accessibility under the building. The nal building geometry offers

higher lift coef cient due to a lower suction under the building.

Besides, the inclined faces on the sides, most of them under suction,

also increase the lift.

Having the back of the building partly on top of the garage roof

makes the positioning of the latter another design parameter to

take into account. Fig. 14 shows the inuence of the step height

between the garage roof and the ridge top on the aerodynamic

coef cients.

An optimum is noticed around 1 m, with 60% lower lift and 20%

lower drag than the position with the garage roof leveled at the

ridge top. With a xed step of 1 m, tilting the garage roof down bya small angle of 3.5 results in a reduction of 20% in lift and drag. In

fact, the garage is acting as a diffuser, enhancing the speed-up

under the building. At 9.5 garage tilt the aerodynamic forces are

not reduced any further. This angle is close to the mean slope

observed in the snow surface at the lee side of the ridge, which was

the surface geometry present during the testing of the reference

building as the garage was not included.

Regarding wind direction variability (Fig. 15) it is remarkable

howlow dependency is of the lift coef cient with wind direction in

the nal building geometry. Surprisingly, the drag coef cient is the

lowest, not at 101 when the building has a parallel orientation to

the wind, but at 135. At 101 the ridge is perpendicular to the

incoming wind and the frontal area offered by the building-ridge

ensemble is the largest, producing a larger wake and thereforehigher drag. In the contrary, when the building is aligned with the

wind direction the highest speed-up is generated under the

building and the lowest lift is produced. The presence of the tower

increases the drag in the SE-S sector.

6. Evaluation of the design in the eld

Unfortunately there are no eld measurements that could be

used for validation of the wind tunnel design. Nevertheless it is

worth looking at some photos that were taken behind the Princess

Elisabeth station during the rst years of operation of the station

that allow a visualization of the nal capabilities of the building to

cope with snowdrifts.

Fig. 16 shows the situation of the snowdrifts behind the station

at the arrival of the BELARE 2008e09 season in November 2008.

The station was built in the previous season and was left inhabited

during the winter. Therefore, the situation shown in the photo

reects the state of the snow surface after 7 months of untouched

snowdrift development. The situation is fairly good with a cleangarage surface and no apparent snowdrift build-up behind the

building. As expected, the erosion patterns produced by the

building are not as severe as showed by the volumetric sand

erosion tests. Overall, the snowdrift aspects seem under control.

Aiming for more energy independence, during the BELARE

2008e09 season the station was equipped with an array of solar

panels that covered the entire surface of the garage roof just

behind the building. This had important consequences in the

building aerodynamics as it is clearly noticed in the photos of

Fig. 17, taken one year later, at the beginning of the BELARE

2009e10.

The solar panels increase the overall drag of the building and

reduce the wind speed-up underneath. This reduces the ef ciency

of the building aerodynamics to passively remove snowdrift. Alsosnow accumulation dunes develop and bury some of the solar

panels increasing the maintenance works. Interestingly, the

asymmetric development of the two snowdrift dunes also

appeared in the wind tunnel tests, where larger accumulations

were observed in the southern side of the building ( Fig. 11).

The snowdrifts might be different from year to year

depending on the interannual variability of the surface wind

Fig. 14. Inuence of garage roof positioning. Final building geometry with 2 m clearance height at 101 wind direction.

Fig.15. Lift and drag coef cients dependency on wind direction for the reference and

nal building models.



16/18

speed. Since AWS measurements are not available during the

operational phase of the station, ERA-Interim reanalysis data

has been used to compute the mean 10 m wind speed in the E-

SSE snowdrift sector over the wintering unmanned period

AprileSeptember as a proxy to snowdrift transport. The snow

transport can be esti mated based on the empirical

function found during the STABLE2 experiment in Halley (Ant-

arctica) [34].

Fig. 16. Situation of snowdrifts behind the princess Elisabeth station at the beginning of BELARE 2008e09 season. Courtesy of René Robert, International Polar Foundation,

November 2008.

Fig. 17. Situation of snowdrifts behind the princess Elisabeth station at the beginning of BELARE 2009e10 season. Courtesy of René Robert, International Polar Foundation,

Novemeber 2009.



17/18

logðQ Þ ¼ 0:632U 3:69 (9)where Q is the snow mass ux in g m1 s1 and U is the mean

velocity. The interannual variability of the mean velocity and snow

transport is provided in Fig. 18 in terms of anomalies, i.e. the ratio of

the seasonal mean to the long term seasonal mean 1989e2010.

It is observed that the snow transport was 14% lower in 2009

than in 2008 which means that the generation of snow build-ups

during the 2009 winter season can be attributed to the presence of

solar panels rather than to changing climatological conditions.

Snowdrift build-ups where also found at the beginning of

BELARE 2010e11 and 2011e12 seasons. Regardless of the large

interannual variability between 2009 and 2010 (58% increase) the

size of the snowdrifts was quite similar which means that the

cumulated volume reaches a quasi-steady state within the winter

season. Nevertheless, the main building always remains snow-freeensuring accessibility. The maintenance works for removing the

snow around the solar panels and garage entrance take a few days

at the beginning of each season as reported in the station’s website.

7. Conclusions

The integrated design of an Antarctic building requires careful

consideration of the environmental conditions in which it will be

immersed. The conceptual design requires a rapid prototyping

process where the sand erosion technique proves useful to assess

snowdrift and wind conditions around different building concepts.

Dune formation tests help visualizing the erosion strength of the

building wake around the under-snow garage. Sand erosion and

wind loading tests showed the high sensitivity of the aerodynamicsof the building with the positioning on the ridge, all controlled by

the behavior of the ow under the building.

The envelope and optimization design phases were also sup-

ported with wind tunnel testing and CFD modeling aiding the

decision making process until the assessment of the nal design.

The aerodynamic shape of the nal building results in 40% drag

reduction. The overall forces can be further lowered by using the

garage roof as a diffuser. Increasing the trailing edge area by

introducing a step between the ridge top and the garage rood

results in 60% lower lift and 20% lower drag. A small inclination of

the roof by 3.5 reduced further lift and drag by 20%.

After therst years of operation of the Princess Elisabeth base, it

can be concluded that the station can effectively cope with snow-

drift, producing no signi

cant impact in the snow patterns behind

the ridge as predicted by the wind tunnel sand erosion tests and

conrmed with measurements of the snow surface topography

before and after the construction of the building [25].

This study constitutes a good example of the advantages of

including wind engineering since the beginning of the integrated

building design process, giving the opportunity to consider the

most effective use of the environment while achieving important

structural and maintenance savings by carefully selecting the

optimum positioning and shape of the building.

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Fig. 18. Mean velocity and snow transport anomalies with respect to the long term

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the prevailing wind direction E-SSE.



18/18

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