Compatibility conditions, modulation mechanisms and preferred modes in incompressible flow over a cavity

TL;DR

This paper investigates the mechanisms behind self-sustained oscillations in incompressible cavity flows, focusing on shear layer instability, feedback, and modulation, and identifies two preferred oscillation modes at medium Reynolds numbers.

Contribution

It introduces a detailed categorization of flow modulated regimes and highlights the existence of two preferred oscillation modes in cavity flows.

Findings

Identification of two preferred oscillation modes.

Analysis of frequency coincidence due to spectral sidebands.

Persistent mode involved in flow modulation across regimes.

Abstract

Self-sustained oscillations in cavity-flows can be strongly influenced by shear layer instability acting together with feedback and modulation mechanisms. When coherently organized, these oscillations lock-on at a fundamental frequency and compatibility conditions exist between shear layer forcing, non linear interactions and low-frequency modulations. Special attention is given to the frequency coincidence which may appear in spectral distributions due to combinations between the dominant peak and its sidebands. Hence, the possible existence of two preferred modes in incompressible cavity-flows at medium Reynolds numbers is shown. This leads to a detailed categorization of the flow modulated regimes and to the specification of a persistent mode involved in modulation process whatever the oscillation stage.