紊流邊界層之入流邊界模擬為計算風工程領域之重要課題,Huang(2010)提出先進的DSRFG(discretizing and synthesizing random flow generation)方法,建構適用於大渦模擬(LES)之入流紊流產生器,可輸入任意風速頻譜,並且滿足非等向性與空間相關性。Castro(2011)基於DSRFG方法進行修正研究,除維持原有特性與優點外,另提升空間相關因子的可調式性,並加入時間相關性因子,得到改良式隨機紊流產生法(modified discretizing and synthesizing random flow generation,MDSRFG),使得該紊流產生器的調適度更加提升。本研究數值模擬之紊流模型採用大渦模擬的方法,入流邊界條件由MDSRFG方法產生,以市郊地況(suburban terrain)之大氣邊界層參數設定入流面條件包含平均風速、紊流強度以及紊流積分長度尺度。此外,利用風洞實驗所量測之風場交相關與自相關分析結果,調適空間與時間相關性因子。最後檢視數值模擬結果之紊流強度沿主流向之變化,以及空間中紊流頻譜的特性,進而探討紊流產生器於大氣邊界層模擬的適用性以及範圍。 Generating the atmospheric boundary layer is one of the important issue of computational wind engineering (CWE) techniques. The discretizing and synthesizing random flow generation (DSRFG) method, a newly developed inflow turbulence generation method proposed by Huang et al. (2010), was adopted to produce an inlet fluctuating velocity field satisfying any target spectrum. Castro et al. (2011) modified the DSRFG (MDSRFG) method, which is based on DSRFG, preserving its main characteristics and advantages. It preserves the statistical quantities that would be prescribed at the inlet of the domain independently of the number of points in the spectrum. The main objective of this study is to generate a suitable urban terrain condition inlet for LES simulation, and evaluate the parameters of time and spatial correlation. We also checked the maintenance of turbulence intensity profiles and wind speed spectrums along wind direction to confirm the upstream distance to the testing object in the wind tunnel.
Relation:
2013電子計算機於土木水利工程應用研討會論文集=Conference on Computer Applications in Civil and Hydraulic Engineering 2013 (CCACHE 2013),10頁