防风网透流风空气动力学特性大涡数值模拟研究

摘要

Large eddy simulations model were established for turbulent flow of incompressible viscous fluids based on finite volume method.Smagorinsky-Lilly model was used as the subgrid model and immersed boundary method (IBM)was introduced to implement nonslip wall boundary conditions.In-vestigations were carried out for seepage winds from windbreak with Reynolds numbers ranging from 30 to 30000.Based on the simulation results,four typical flow zones were identified for the seepage wind behind butterfly-shaped windbreak.There are large scale stratified shear flow structures in the flow, which are caused by the butterfly shape and significantly enhance energy dissipation.Laminar to turbu-lent flow transition occurs at Reynolds number of around 300.When Reynolds number increases to 3000, the flow develops to fully turbulence with streamwise turbulent intensity up to about 70%.The drag resistance of windbreak is much larger than the linear adding of individual orifice plate flows,which implies that the interaction among the j et flows and the shear flow structures may significantly contribute to the flow resistance.This provides scientific support to saving windbreak material via optimizing porthole arrangements and the windbreak shapes.%基于有限体积法建立不可压缩粘性流体运动的大涡模拟模型，采用 Smagorinsky-Lilly亚格子模型，并引入浸入边界法(IBM)实现无滑移固壁边界条件，对雷诺数30~30000之间防风网透流风进行模拟研究。基于模拟结果，提出蝶型防风网透流风存在4个典型分区结构，流场中存在由蝶型形态引起的大尺度分层剪切流动，加强流体动能耗散。透流风在雷诺数300时发生层流至湍流的转捩，而在雷诺数增长至3000以上时，湍流充分发展，纵向流速脉动强度可达70%。防风网整体空气阻力远大于单个孔口射流阻力的线性叠加，射流间的相互作用以及大尺度的分层剪切结构大大增加流体阻力损失，这为通过优化孔口布置和网板形态来节省材料提供了科学依据。