基于相干结构的大涡模拟壁面模型

首先对湍流边界层近壁区相干结构群进行研究,根据共振三波理论使用沿流向周期性发展的多个三维波构造其初始结构,通过直接数值模拟得到该相干结构群的演化特性.在此基础上,提出了基于近壁区相干结构流动参数的新型大涡模拟壁面模型.确定了此壁面模型与主流大涡模拟衔接的原理方案.计算结果表明:该壁面模型在减少计算量的同时,能够为主流区大涡模拟提供重要的壁面大尺度结构信息,使计算取得准确的结果,实现了壁面模型的基本功能.

Wall model in LES based on coherent structures

The evolvement of a group of coherent structures in a turbulent boundary layer was studied previously.An initial structure was formed by the resonant triad waves which developed periodically in the streamwise direction.The characteristics and evolvement processes of the coherent structures were obtained by direct numerical simulation.Based on the coherent structures,a new type of wall model for large-eddy simulation(LES) was established.The height at which to supply the wall model was determined.And different choices of boundary conditions were tested.The results of a channel flow LES indicate that: the wall model decreases grid number adjacent to the wall region;the wall model provides the core flow LES sufficient near-wall region information so that the simulation can gain exact results compared with that without wall models.