大渦數值模擬高層建築物地下室風場分析與改善可行性之研究

Large eddy simulation of wind field analysis and improvement feasibility of high-rise building basement

江毅倫(Yi-Loon Chiang)

指導教授 ： 朱錦洲

共同指導教授 ： 張建成

國立臺灣大學/工學院/應用力學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902564

摘要

雖然研究城市環境風場的學者很多，但是探討高層建築對於地下室的影響卻鮮少有人提及。由於迎風面流速較高，導致強風流入迎風面開口的地下室，使內部風速與壓力上升，造成人員行走與搬運貨物上的困難。強風通過狹縫的聲音也讓人心惶惶，嚴重時可能會使電梯設備損壞無法正常開啟關閉。
本研究使用大渦模擬(Large Eddy Simulation)計算含有地下室之高層建築物的高雷諾數流動。為了準確模擬流場流動，在近地與建築物設置邊界層網格，入流使用指數剖面大氣邊界層，建築物周圍與地面設置無滑移條件，並在外流場與地下室設置出口。研究結果表明進入地下室的氣流並不是地表氣流，而是建築物高度1/2至2/3處之氣流，藉由迎風面下衝渦流(upstream downwash vortex)流經地表並進入地下室。由於大氣邊界層高度越高速度越快的特性，流入地下室的氣流風速是高於地表風速的，高速氣流的流入會使地下室入口風速與電梯門處壓力上升。分析不同風向上的變化可以發現，若風向與迎風面夾角越大，入口處的二次分離流動區域增加，減少進入地下室的氣流，達到降低電梯門壓力的效果。若將地下室入口處外觀改變以阻擋氣流流入，發現在地下室車道加上屋頂可以有效減少入口處風速與電梯門壓力50%以上。車道入口高度降低更能有效地降低電梯門壓力。

關鍵字

行人風場 ； 高層建築物 ； 地下室 ； 紊流 ； 大渦模擬 ； 風速

並列摘要

Although there are many scholars studying the urban environmental wind field, it is rarely mentioned that the influence of high-rise buildings on the basement . Due to the high flow velocity on the windward side, strong winds flow into the basement opening in the windward side, causing the internal wind speed and pressure to rise, causing difficulties for personnel to walk and carry goods. The sound of strong wind passing through the slit is also heart-wrenching. In severe cases, the elevator equipment may be damaged and cannot be opened normally.
This study uses Large Eddy Simulation to calculate high Reynolds number flows for high-rise buildings with a basement. In order to accurately simulate the flow field flow, a boundary layer grid is set in the near ground and the building. The inflow uses the exponential atmospheric boundary layer, and there is no slip condition around the building and the ground, and an exit is set in the outer flow field and the basement. The results show that the airflow into the basement is not close to the ground airflow, but the airflow at 1/2 to 2/3 of the height of the building, flowing through the ground and entering the basement through the upstream downwash vortex.Because the higher the boundary layer height is, the faster the velocity is. The airflow velocity into the basement is higher than the surface wind speed. The inflow of high-speed airflow will increase the inlet wind speed of the basement and the pressure at the elevator door. Analysis of the changes in different wind directions can be found that if the angle between the wind direction and the windward surface is larger, the secondary separation flow area at the entrance increases, reducing the airflow entering the basement and achieving the effect of reducing the pressure of the elevator door. If the appearance of the entrance to the basement is changed to block the inflow of air. If the appearance of the basement entrance is changed to block the inflow of airflow, it is found that adding a roof to the basement lane can effectively reduce the wind speed at the entrance and the elevator door pressure by more than 50%. The reduction in lane entry height is more effective in reducing elevator door pressure.

並列關鍵字

Pedestrian Wind Environmental ； high-rise buildings ； basement ； turbulence ； large eddy simulation ； wind speed

參考文獻

[1] 朱佳仁, "高層建築物風場環境評估規範研議," 內政部建築研究所研究報 告, 2000.

[2] A. F. Handbook, "American Society of Heating," Refrigerating and Air Conditioning Engineers, Atlanta, 2005.

[3] D. J. Wilson, "Flow patterns over flat roofed buildings and application to exhaust stack design," ASHRAE Trans., vol. 85, pp. 284-295, 1979.

[4] J. H. Ferziger and M. Peric, "Computational methods for fluid dynamics." Springer Science & Business Media, 2012.

[5] J. He and C. C. Song, "Evaluation of pedestrian winds in urban area by numerical approach," Journal of Wind Engineering and Industrial Aerodynamics, vol. 81, no. 1-3, pp. 295-309, 1999.