Direct Computation of Jet Noise Produced by Large-Scale Axisymmetric Structures

A methodology is presented for directly calculating the noise emission associated with large-scale structures in a supersonic jet. The nonlinear governing equations are solved in a computational domain that encompasses both the jet e ow and the acoustic near e eld. A high-order discretization scheme is used along with careful boundary treatment to capture the disturbance e eld accurately. Nonlinear interactions among the various frequency modes of the e ow structure were found to alter the development of each mode and, hence, ine uence its radiation pattern. Comparingthecalculatedradiationpatterntoexperimentalobservationsindicatesthattheaxisymmetricstructure contributes preferentially in the forward direction, whereas the azimuthal structure is associated with a higher emission angle and with a stronger effect on jet spreading. Sensitivity of the radiated sound e eld to the type of incoming disturbances is studied.