建築物與地形在大氣邊界層中的流場模擬; Numerical analysis of building and terrain in the atmospheric boundary layer

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Title:	建築物與地形在大氣邊界層中的流場模擬;Numerical analysis of building and terrain in the atmospheric boundary layer
Authors:	周郁汶;Chou,Yu-Wen
Contributors:	機械工程學系
Keywords:	計算流體力學;山丘與建築物的氣流交互作用;大氣邊界層;Computational fluid dynamics;Wind flow interaction with hill and building;Atmospheric boundary layer
Date:	2013-08-19
Issue Date:	2013-10-08 15:28:35 (UTC+8)
Publisher:	國立中央大學
Abstract:	建築物在不同地形下受到大氣紊流特性影響，造成結構損壞或降低壽命。因此本文針對二維山丘和三維對稱山丘的地形模型重建，以ANSYS FLUENT軟體配合realizable k-ε紊流模型對山丘地形進行大氣邊界層模擬，並比較不同參考風速及地表粗糙程度，分析建築物受地形影響下之橫風向與順風向之受力分析。為確保模擬結果準確性，驗證的例子，包含單一山丘、山丘與建築物、兩平行建築物及斜型屋頂等。當流體流經山丘後，產生加速現象，進而影響到下游流場；若下游處有建築物等，於建築物的迎風面產生迴流現象，此類迴流又稱為馬蹄型渦流。從斜型屋頂驗證可發現，傾斜式屋頂較平坦屋頂會加速屋頂上方流速。模擬結果顯示，建築物受到不同的地形影響甚大，當地形為二維時，在流場風速範圍內（<10 m/s），迎風面處的正壓皆在上緣處產生，但隨著地形變為三維時，正壓影響的範圍從上緣變至中間偏高的位置，當風速加至10 m/s時，則正壓變為左側位置，其兩者差異來自三維地形較二維地形多了側向梯度影響造成。建築物受三維地形影響的大氣紊流特性，以建築物的兩側邊最為明顯，當改變不同間距時，迎風面及兩側受到的紊流影響也較二維來得明顯，顯示長時間下，亦受到紊流影響的區域，需加強結構物的強度，而二維地形，少了側向影響，對建築物側邊的影響則見低許多。受力方面，當地形為二維時，建築物受順向風力及側向風力影響較大，而地形變至三維時，由於多了側向影響，使得建築物背風面之尾流區負壓漸增，使得背風面受力較大。 Buildings on different terrain are affected by atmospheric turbulence characteristics, which cause structural damage or reduce the life of buildings. This study is aimed to study two different terrain models, two-dimensional and three-dimensional hills. The numerical work uses ANSYS FLUENT with the realizable k-ε turbulence model to simulate the atmospheric boundary layer over the hill and buildings and compare effects of wind speed and surface roughness. In addition, analysis of wind forces along the streamwise and side on buildings were also investigated. To ensure the accuracy of the simulation results, several validation cases were made, including single hill, hill interacted with building, two parallel buildings and sloping roofs cases. When the fluid flows through the hills, resulting in flow acceleration and affecting the downstream flow field if there is a building behind the hill, recirculation may occurred on the windward side of the building, this is known as horseshoe vortex. From the validation of slanted- and flat-roof buildings, it can be found that the slanted roof-shaped can increase flow velocity at the roof top easily. This study show that the building was affected by different hills. For two-dimensional hill, the flow field could generate positive pressure at the up edge of windward. As for the three-dimensional hill, the region of positive pressure changed from the up edge to the middle of windward surface. When the wind velocity increase to 10 m/s, positive pressure occur at the left of windward, because of three-dimensional hill have additional lateral gradient effect than the two-dimensional hill.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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