Investigation on noise generation of open cavity flow using Lagrangian coherent structures

The noise generation mechanism of an open cavity flow is investigated using Lagrangian coherent structures (LCS) together with dynamic mode decomposition and Helmholtz decomposition methods. The flow field of an open cavity with the length-depth ratio L/D = 2, Mach number Ma = 0.8 and Reynolds number Re = 2500 is first obtained through direct numerical simulation with 5-th order weighted essentially non-oscillatory (WENO) scheme. LCSs are then obtained from flow field reconstructed by the mean velocity field and the decomposed modes. The interactions between LCSs inside the shear layer and the squeezing zone are found to be important sound sources. The method efficiently isolates the structures responsible for the noise generation. (paper)