It is definitely not always the case that the wind blows less hard in the city. After all, a considerable portion of the wind that collides with tall buildings is deflected downwards. If this air currents subsequently moves around the building at street level, very high wind speeds arise locally.
A nearby example is residential tower block De Admirant, which caused wind nuisance in the Nieuwe Emmasingel in Eindhoven. For this reason, on the advice of TU/e professor Bert Blocken and his colleagues from the Building Physics and Services unit, a 750-square-meter awning has recently been installed, which is intended to decimate the wind speed in the shopping street.
Such wind nuisance can be tackled in a variety of ways, says Thijs van Druenen, who graduated on similar research. He thinks it can be achieved by removing parts of a floor, by applying an awning as on De Admirant, or by creating a podium – a low extension. “For those three methods I have calculated how they can be applied in the most effective manner. To do so I made a computer simulation of a building that is sixty meters high and wide, and fifteen meters deep.”
Entrance Hoofdgebouw is a notorious wind hole
A notorious wind hole on the TU/e campus is located in front of the entrance to Atlas. This tallies entirely with the results of his simulations, says Van Druenen. “Openings in a building on the ground floor and the first floor prove to be the most unfavorable. For the optimal result at the level of pedestrians the best thing to do really would be to take out the whole second floor.” Indeed, the wind blowing through the resulting hole is subsequently deflected upwards. Of course, having said that he is fully aware that this is a solution that would be hard to realize. “Still, you can consider leaving out portions of certain floors; that could definitely help.”
Simulating air currents in the built environment is actually still in its infancy, Van Druenen explains. This is due in particular to the computing required for the simulations. Thus, the calculation of a single scenario (certain structural adjustments and wind direction) took a full day at the computation cluster of the Department of Architecture, Building and Planning. “On my laptop it would certainly have taken me a week. And I tried some ninety different simulations, so that was not an option.”
His main conclusion: each situation is different, which makes it risky to start building on the basis of general assumptions. “For example, a small podium can have a negative effect in case of a specific wind direction. You really need to compute each situation with different wind directions.”
Scoring 9.5, Van Druenen passed his graduation research with flying colors. As a result, he can continue his calculations of air currents as a PhD candidate at Building Physics and Services for the coming years. Possibly applied toaerodynamics in sport. “That is a kind of hobby project embraced by Bert Blocken; I cooperated in that as a student assistant and I would like to continue that.”