  The present study reports the effect of different source terms on the near
and far-field acoustic characteristics of compressible flow over a rectangular
cavity using hybrid computational aeroacoustics methodology. We use a low
dispersive and dissipative compressible fluid flow solver in conjunction with
an acoustic perturbation equation solver based on the spectral/hp element
method. The hybrid approach involves calculating the base fields and the
acoustic sources from a fluid simulation in the first step. In the next step,
the acoustic solver utilizes the variables to predict the acoustic propagation
due to the given sources. The validation of the methodology against benchmark
cases provides quite accurate results while compared against the existing
literature. The study is then extended to assess the importance of the entropy
source term for the flow over a rectangular cavity. The predictions of hybrid
simulations with vortex and entropy source terms reproduce the perturbation
pressure values very close to the existing direct numerical simulation results.
Moreover, the results suggest that the use of just the vortex source terms
over-predicts the perturbation pressure near the source region. Finally, we
have carried out detailed simulations with all the source terms to investigate
the noise sources for compressible flow over the cavity for different Mach
number ranges (M = 0.4; 0.5; 0.6; 0.7; 1.5). The obtained acoustic spectra and
the sound directivity are in close agreement with the reference experiment.
