外掠百叶板流场自持振荡数值模拟研究

外掠百叶板流动在工程中十分常见，由其引发的流场自持振荡现象能够导致流场压力持续波动，使周围结构承受持续作用的周期载荷，造成结构疲劳安全隐患。采用数值模拟方法，针对外掠百叶板流场自持振荡问题进行研究。计算结果表明：低马赫数条件下，外掠百叶板流场中产生的自持振荡现象属于纯流体动力学问题，其形成原因为流场剪切层振荡所引发的大尺度涡团的形成与迁移。同时，随之产生的压力振荡具有持续性及周期性。自持振荡频率是空间均匀的，而幅值在主流方向上呈先急剧增大后稳定，最后小幅减小的趋势。随着百叶板内侧的空腔体积不断增大，振荡频率变化较小，振荡幅值逐渐增大并在空腔体积达到一定值后保持稳定。

Numerical simulation of self-sustained oscillations in flow past a louver

Flow past louvers is common in engineering applications. Self-sustained oscillations caused by the flow configuration lead to periodical pressure fluctuations. Because of that, periodic loads will be applied on circumambient structures continuously and may give rise to fatigue problems. Using a numerical simulation method, self-sustained oscillations caused by flow past a louver are studied in this paper. The numerical results show that when the Mach number is small, the self-sustained oscillations belong to a pure fluid dynamic problem. This phenomenon is induced by generation and propagation of large-scale vortices which are generated from fluctuations of the shear layer. In addition, pressure oscillations generated by this phenomenon contain two significant features: sus-tainability and periodicity. The frequency of the self-sustained oscillations is spatially uniform. Along the mainstream direction, the amplitude of the self-sustained oscillations sharply increases first and then stabilizes. At the impingement edge, it slightly decreases. With an increasing size of the cavity inside the louver, the variation of the frequency basically remains stable. On the other hand, the amplitude increases gradually and remains stable when the cavity size reaches a critical value.