邊界層流中高層建築風力特性之數值模擬

Numerical Simulation of wind loads on a high-rise building in turbulent boundary layer flow

陳宥芸(Yu-Yu Chen)

指導教授 ： 鄭啟明

淡江大學/工學院/土木工程學系碩士班/碩士(2010年)

https://doi.org/10.6846/TKU.2010.00682

摘要

本研究主要是在使用大渦模擬法去模擬風場中高寬比1:3之方柱所受的風載重，對風載重的模擬結果會做結構反應分析並對照風洞實驗室的實驗結果；探討方向分為三個部份。
首先，在第一部份模擬均勻流場中方柱問題主要在確立方柱周圍的網格劃分，我們將方柱放在上游距離入流口8D的位置，並給予Re=1×105的均勻入流；而本文的模擬結果風壓分布對照實驗結果在迎風面結果吻合，但在背風面風壓值偏大，使得拖曳力係數值偏大，雖然如此，由於與前人的模擬結果誤差相近，而史特赫數、擾動昇力係數接近實驗值，因而確立此未來網格劃分。
第二部份目的則在模擬大氣邊界層風速剖面的風場，因此本研究在入流口給予淡江大學風洞實驗室邊界層，即給予平均風速、紊流能量、紊流消散率，並在地面給予表面剪應力當作在風洞實驗室在地面的粗糙元素，在距離上游入流8D的位置會是後面我們放置建築物的位置，我們希望模擬出來的風場能吻合實驗室的邊界層；模擬結果在風場的1/3高以上在平均風速跟擾動風速可以的到好的剖面，但在下方的擾動風速明顯較小，有明顯的紊流消散在影響這個風場。
到了第三部份我們要將高寬比1:3之方柱建築物放在距離上游入流8D的大氣邊界層風速剖面的風場裡，所有初始設立的條件都與第二部份相同，即在入流給予平均風速、紊流能量、紊流消散率，並在地面給予表面剪應力；計算結果與實驗數據比較，在拖曳力係數Cd、擾動拖曳力係數Cd’，我們得到的結果都比實驗值大23%，擾動性昇力係數Cl’較為偏大，史特赫數為0.09。

關鍵字

數值模擬 ； 風工程 ； LES ； 邊界層

並列摘要

This study is the wind load of the square shaped building with the aspect ratio 1:3 were simulated by large-eddy simulation method. The simulation results of wind load and structural response analysis were compared with those of wind-tunnel test. There are three parts would be study.
First, it divide grids around the square column mainly. We set the square column at 8D downstream of the inflow boundary, and gives the uniform flow of Re=1×105 in inflow. The results of this study, wind pressure is agree in the windward, but bigger than wind-tunnel test in the leeward. These causes the drag force coefficient to be big. Because the results is closed to the simulation of predecessor. The Strouhal number and lift coefficient close experimentation value. So it confirmed the grids.
Second, a fully developed boundary layer flow initially generated in the wind tunnel was selected as the target flow field. Additional a fully developed boundary layer flow of the wind tunnel test, i.e., mean wind speed, kinetic energy and dissipation rate. And additional the surface shear was set on the ground to represent the effects of wind tunnel surface roughness elements. The upper twe-third of the profile is also agreed well with target flow. The flow in the lower one-third of the calculation domain has excessive energy dissipation, with RMS wind speed lower then the target flow field.
In the third stage of this project, the 1:1:3 square shaped building model was installed at 8D downstream of the inflow boundary. All the initial conditions are set up with the second part of the same, i.e., add mean wind speed, kinetic energy and dissipation rate at the inflow boundary, and shear stress on the ground. The result compare with wind tunnel test,the mean drag force coefficient and RMS drag force coefficient value are found 23% larder than wind tunnel measurement, and lift coefficient is too large. The Strouhal number is 0.09.

並列關鍵字

numerical simulation ； wind engineering ； LES ； boundary layer

參考文獻

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