The effect of an internal object on self-sustained oscillations in a flow past a louvered cavity

Abstract

Self-excited oscillations occur when fluid passes through a louvered cavity. In practical engineering applications, various devices are often installed in such cavities. In this study, numerical simulations are conducted to investigate the self-excited oscillations of the flow field within a louvered cavity containing an internal object. The effects of the Reynolds number (Re) and the object-louver distance (λ) on the amplitude and frequency of self-excited oscillations are summarized. It is found that stage switching occurs when Re and λ are above or below the critical values. When stage switching occurs, the flow field operates in a new pattern with a low-frequency oscillation component added to the original spectrum. The frequency of this low-frequency component is half of the original dominant frequency. The reason for this phenomenon is that large-scale vortices exhibit different motion patterns at the impingement edge under various Re and λ. In addition, dynamic mode decomposition is then used to decompose the flow field. The results show that when stage switching occurs, the mode corresponding to the new low-frequency component dominates the flow field, and its influence region mainly locates at the downstream part of the louver.