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    Education in Research through Research


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    Education in Research through Research


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  • von Karman Institute for Fluid Dynamics

    Education in Research through Research


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impression of the building configuration The selection of the most suitable location and the assessment of the aerodynamic behavior of the base are fundamental design issues. The most important parameters from the aerodynamic point of view are: snow accumulation and erosion, wind loading and wind comfort and safety.

The station has evolved to a hybrid design, with the main building above ground-level and anchored onto snow-free rock area and a garage and storage building constructed under the snow in the lee side of the ridge. Both are connected with the main building through a weather protected bridge. Figure 1 shows an as presented in the press conference in May 2006.

The facilities will use renewable energy as the primary energy source with the minimum use of fossil fuels [1][2]. The whole station is conceived as state of the art of sustainable development technologies with the highest energy efficiency and the lowest environmental impact, fundamental issues of the Antarctic Environmental Protocol.

The severe ambient conditions at the site make the use of wind tunnel modeling an invaluable tool to support the design process. A model of the ridge topography at a scale 1:100 has been installed at the 3-m wide test section of the VKI L1-B atmospheric boundary layer wind tunnel. Both a layered and a smoothed model have been tested to simulate the appropriate roughness conditions of the atmospheric boundary layer. Numerical simulations and wind tunnel measurements enable the characterization of the wind over the ridge topography.

VKI L1-B wind tunnel model of the ridge topography with a hot wire probe
Figure 2: VKI L1-B wind tunnel model of the ridge topography with a hot wire probe

The main concern from the aerodynamics point of view is the ability of the building to cope with intense drifting show. Many Antarctic stations have had serious problems with snow drifting and deposition, with eventual buried structures that require costly maintenance to prevent from inaccessibility and structural damage. To overcome this problem, it is common practice to use elevated buildings, which allow the wind to flow underneath blowing the snow away from the downwind building walls. Preliminary snowdrift tests have been conducted in the L1-B wind tunnel, using sodium bicarbonate to simulate the snow phase, on a scaled model of the Observation Hut of the Japanese Syowa Station in Antarctica.


Snowdrift test Figure 3: Snowdrift test

The snowdrift model provides realistic results of the snow deposition and enables the estimation of the snowdrift development rate for the real conditions. The influence of the ridge topography on the snowdrift patterns has been studied for several building block concepts. Sand erosion technique has been proven very efficient to point out those areas of dangerous wind comfort and, at the same time, give an idea of the expected snow accumulation and erosion regions. Those areas which are not eroded at high velocities indicate high probability for snow buildup and those eroded very soon indicate poor wind confort, both problems to be considered for a safe operation and accesibility of the base.


Sand erosion tests Figure 4: Sand erosion tests (using pink-coloured sand) and extracted speed-up contour map

The positioning of the building on the ridge and its orientation against the prevailing winds from the East has been studied with regard to wind loading. A reference building model instrumented with 133 pressure taps enables the mapping of the mean pressure field on the external walls. By integration, the overall mean wind loading can be determined.

The building windward cantilever is an important optimization parameter as it triggers both the wind loading and the snow erosion and accumulation. Depending of the building orientation an optimum positioning is determined that minimizes the wind loading while preserving the snow erosion and deposition under control.


Model instrumented with pressure taps Figure 5: Model instrumented with pressure taps and measured mean pressure coefficient maps in the top and bottom building faces. Configuration at 45o wind incidence.

The building oriented with a wind incidence of 0o, with respect to the prevailing winds from the East, has better aerodynamic performance than the one at 45o. The delta wing vortices generated by the 45o case result in higher wind loading, specially with regard to lift forces, and a stronger erosion on the snow surface around the garage.

From the reference square-based building concept the geometry has evolved to an octagonal-based building offering better modularity for construction. The new building geometry has been tested using sand to emulate the snow erosion (Figure 6). The vorticity generated by the building clears up the sand on top of the garage and creates important erosion on the loose sand bed behind it.


Sand erosion behind the buildingFigure 6: Sand erosion behind the building.

The detailed design of the building is approached with Computational Fluid Dynamics as it gives access to very detailed information about the simulated flow field. Figure 7 shows the velocity speed-up factor generated by the building. It is clearly noticed the high acceleration generated under the building, leading to poor wind comfort and high snow erosion on the top of the garage.

 

 

 

Velocity speed-up factor generated by the building Figure 7: Velocity speed-up factor generated by the building

 

 

 

Pressure field on building facadesFigure 8: Pressure field on building facades

 

 

 

 

The aerodynamic optimization of the building continues during the detailed design phase…

For more information, Jeroen van Beeck

Links:International Polar Foundation

[1] Belgian Science Policy and International Polar Foundation, Construction and Operation of the New Belgian Research Station, Dronning Maud Land, Antarctica. Draft Comprehensive Environmental Evaluation (CEE), February 2006, 94 pgs.
[2] J.Sanz Rodrigo, J. van Beeck, C. Gorle, J. Berte, L. Dewilde, Y. Cabooter, F. Pattyn. Wind Power in the future Belgian Antarctic Research Station. Proceedings of the European Wind Energy Conference, Athens, February 2006.