Numerical investigation of a deep cavity with an overhanging lip considering aeroacoustic feedback mechanism

TL;DR

This study investigates the flow-induced noise in a deep cavity with an overhanging lip, using numerical simulations to analyze flow structures, acoustic feedback, and the effects of domain dimensionality at different velocities.

Contribution

It provides detailed insights into turbulent flow structures, acoustic feedback mechanisms, and validates the reduction of 3D to 2D domain for aeroacoustic simulations.

Findings

Flow structures vary with velocity and domain dimensionality.

Acoustic feedback mechanism is influenced by vortex-edge interactions.

Pressure spectrum peaks are linked to specific flow mechanisms.

Abstract

In modern transport systems, passengers' comfort is greatly influenced by flow-induced noise. In this study we investigate a generic deep cavity with an overhanging lip, mimicking a door gap in a vehicle, that is overflowed by air at two different free stream velocities, 26.8m/s and 50m/s. The turbulent boundary layer and the acoustic waves interact with the cavity's geometry and form a strong feedback mechanism. In the present work, we focus on the details of the compressible turbulent flow structures and their variations concerning the velocity, the boundary layer as well as the domain dimensionality for a later acoustic simulation within a hybrid aeroacoustic workflow. Furthermore, we verify the feasibility of reducing the acoustic computational domain from 3D to 2D for this application by conducting a coherence study of acoustically active flow structures in the spanwise direction. The role of the three-dimensional Taylor-G\"ortler vortices from the recirculation regarding the vortex formation and the vortex-edge interaction was also evaluated. Remarkably for the lower approaching velocity (26.8m/s), we found a special vortex-edge interaction, namely an alternating sequence of complete clipping and a subsequent partial escape. Lastly, we assigned previous unknown peaks in the pressure spectrum to their corresponding mechanisms.