合成双射流冲击平板流场结构与模态分解分析

为揭示合成双射流冲击平板流场结构特征,通过大涡模拟方法对合成双射流冲击平板流动进行了仿真,采用有限时间Lyapunov指数方法对流场的拉格朗日涡结构进行了识别,并与欧拉框架下的速度矢量和涡量结果进行了对比分析。结果表明,在合成双射流两股射流交替作用下,射流核心区涡系结构较为复杂且涡量丰富,远离核心区存在一对稳定的涡结构,且拉格朗日涡结构与涡量对应较好,为合成双射流冲击冷却的布局设计提供了指导。另外,流场本征正交分解表明,第一阶模态关于激励器出口中心轴线大致对称,其能量占总体能量的35%,前6阶模态的能量占80%；根据前6阶模态所反映的流场特性,合成双射流冲击平板流场具有高度的对称性。

Flow field structures and mode decomposition analysis of dual synthetic jets impinging plate

To reveal the flow field characteristics of dual synthetic jets impinging plate, the large eddy simulation method was used to numerically study the flow of dual synthetic jets impinging plate. The Lagrangian coherent structure of the flow field was identified on the basis of the finite-time Lyapunov exponents, and the results were compared with the vorticity results in the Euler frame. It is found that the vortex structure of the jet core area of dual synthetic jets is exceeding complex and rich under the alternating action of periodical jets, and there is a pair of stable vortex structure far away from the core. Lagrangian coherent structures are well corresponding to the vorticity, provided guidance for the layout design of dual synthetic jets impingement cooling. Proper orthogonal decomposition analysis is performed on the flow field of dual synthetic jets. The results show that the first-order mode is approximately symmetrical about the central axis of the exit of the actuator, and its energy accounts for 35% of the total energy, and the first 6 modes account for 80%. According to the characteristics of the flow field reflected by the first 6 modes, the flow field of dual synthetic jets impinging plate has a high degree of symmetry.