地表粗糙元素對於模擬大氣邊界層之影響

The effect of surface roughness elements on the atmospheric boundary layer

胡琮普(Tsung-Pu Hu)

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(2012年)

https://doi.org/10.6846/TKU.2012.00499

摘要

風力規範對於建築物設計風力有重要影響的參數可分為三大類：設計風速及風場特性，風壓係數，陣風反應因子。其中影響最為重要，且具有本土特性的是設計風速及風場特性。探討自然風場特性的可行方法不外乎實場監測與風洞模擬，二種研究方法各有其優缺點。實場監測的數據最為真實可信，然而確有設備昂貴、設點不易、量測困難、強風難求等諸多難處。風洞縮尺實驗最為便捷，然而僅採用風洞試驗進行自然風場之模擬亦有不及之處。本文首先依據在都會區、鄉鎮區以及農村等三個不同地況的平均風速剖面實場量測監測結果為依據，在淡江大學風洞實驗室，根據實際地況之建築分佈特性，建構地表粗糙元素，並據以發展紊流邊界層特性。本文所得之紊流邊界層特性與實場量測所得之平均風速剖面以及風洞完全縮尺模擬所得之紊流邊界層比較，三者相似性良好。除了代表平均風速剖面之α與z0值之外，本文分別求得三種地況之紊流強度、紊流尺度以及紊流頻譜之分佈特性。本文研究結果並顯示，建構風洞模擬所需之均勻地表粗糙元素時，必須考慮地況特性與量測位址之距離權重參數。

關鍵字

大氣邊界層 ； 粗糙元素 ； 風洞實驗

並列摘要

It is well known that the characteristics of the nature wind, the wind pressure (force) coefficients and the gust response factors are the three most important factors in the building wind code. Among the three items, the nature wind field exerts probably the most significant impact on the design wind load, and at the same time, is the most localized wind load parameter. Field measurement is the direct approach to study the characteristics of atmospheric boundary layers. It is also the most expensive and difficult way to do it. Wind tunnel simulation provides an easier alternative for this purpose. However, wind tunnel results need careful validation. This research project performed an in-depth investigation on the characteristics of nature wind. Based on the in-situ measurements at three different monitoring sites that represent urban, suburban and open terrain categories, three turbulent boundary layers were simulated in wind tunnel. The floor roughness elements used in these simulations were signed based on the actual building developments at the three monitoring sites. The wind profiles of the wind tunnel simulations agree well with the field data and the wind tunnel results of the “replica terrain models”. Wind tunnel study further indicates that the influence of upstream surface roughness on the development of turbulent boundary layer in a medium length test section wind tunnel is proportional to the upstream distance.

並列關鍵字

Atmospheric boundary layer ； roughness ； wind tunnel

參考文獻

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