Numerical Study Of Terrain Influence On The Airflow Over Hilly Land

While air flows over hilly lands, the complex terrain features and physiognomy will observably change turbulence characteristic, wind speed and wind pressure of boundary-layer flow, which results in hilly land's flow environment is much different from plat land's and results in the distributing of wind speed and wind pressure is much anomalistic. So, to research about the characteristic of flow field distributing in hilly area and the rules of flow change results from variety hill height, slope and variety airflow angle is significant for both choosing an appropriate city address in hilly lands and wind resistance design.By adopting numerical model method which bases on Computational Fluid Dynamics, in the first place, for 2D model, it systemically computed and analyzed the airflow field (such as wind speed, wind pressure and turbulence characteristic) of typical terrain, discussed the influence laws of single hill's slope angle, relative size of crest and valley on wind speed of hilltop, turbulence frame, wind profile and so on. The interaction between variety height hills in double hill terrain is also discussed. And then, for 3D model, the wind speed and wind pressure distributing of single hill with diverse slope is researched. Based on it, the principle and process of narrow channels effect forming is showed visually and the change of airflow field in the valley and out of the valley under different wind angle is studied. In the end, considering real terrain, a complex hilly model was formed by three single hills of different heights, different slope, whose airflow characteristic was researched under different wind angle.By comparing and analyzing, it is concluded that for simple and slow slope terrain, the change of wind speed around hill can be truly calculated by some experimental formula such as MSFD calculations. While for cliffy slope and complex terrain experimental formula can't calculate the wind speed truly, it is well to analyze the question by numerical simulation. Based on the distributing characteristic summarization of airflow field in various terrains, some advice about building address choosing was put forward.