This thesis deals with the surface pressure spectrum analysis due to a flow fluctuation and a flow noise propagation. A theoretical analysis of the flow noise is applied to the pressure fluctuations of boundary layer flows. A numerical scheme is used to calculate the flow fields induced by a cylinder above the semi-infinite flat plate. In the vicinity of low wavenumber, the compressibility must be considered to analyse the surface pressure inducing the flow noise on the plate. Theoretical results show the finite wavenumber-whiteness at the wavenumber near zero and the infinite acoustic peak at the wavenumber corresponding to the acoustic speed propagation. The theoretical variations of wall pressure spectrum with the change of surface condition are also considered.
The pressure and velocity fluctuations in the flow field induced by vortex shedding of the cylinder are calculated numerically with the assumption of incompressible flow. The surface pressure spectrum is obtained by the flow and acoustic analysis, which inducing the acoustic contributions due to the flow fluctuation in terms of quadrupole as well as the incompressible pressure fluctuations. The wavenumber whiteness and the acoustic peak are observed from the numerical results which are expected from the theoretical analysis expecially for the wavenumber regions where the compressibility should be considered. It is expected that the resolution of the wavenumber spectrum can be improved with the lager computational domains.
