格栅-空腔自激振荡流场扰动形成机理研究

格栅-空腔流动会引发流场自激振荡现象,产生结构振动及噪声问题.研究此类现象的形成机理对相关设备的减振降噪设计具有重要意义.目前已知这种现象是在流场正逆向两种扰动的耦合作用下形成的,但上述两种扰动的形成机理尚未明确.针对该问题,建立了格栅-空腔流动数值模型,并进行非稳态数值模拟.通过分析压力振荡数据及流场结构演化过程,对两种扰动的形成过程进行了研究.研究结果表明,正逆向两种扰动的形成均与格栅间隔中形成的小尺度涡团有关.上游小尺度涡团从格栅间隔中依次脱离并聚集演化为大尺度涡团,形成该流动系统的正向扰动.下游小尺度涡团脱离格栅间隔激发的逆向扰流构成该流动系统的逆向扰动,并对正向扰动产生持续的正反馈作用.

The formation mechanism of disturbances in self-excited oscillating louver-cavity flows

Flow past a louvered cavity can give rise to self-excited oscillations which can lead to structural vibrations or noise problems.It is significant to study the formation mechanism of this phenomenon for the design of vibration or noise reduction of related equipment.At present,it is known that this phenomenon is excited under the coupling of the forward and backward disturbances in the flow field.However,the formation mechanism of these two disturbances is not clear.To solve this problem,a numerical model of louver-cavity flow is established and unsteady simulation is carried out.By analyzing the pressure oscillation data and the flow structure evolution process,the formation progress of the two kinds of disturbances is studied.The results show that both the forward and backward disturbances are related to the small-scale vortices formed in the gaps of the louver.The small-scale vortices in the upstream region separate from the gaps of the louver successively and aggregate into large-scale vortices.The forward disturbance of the flow system is excited during this progress.The backward disturbance is composed of disturbing reverse flow caused by the separation of the small-scale vortices in the downstream region and has a continuous positive feedback effect on the forward disturbance.