Two-dimensional model of low Mach number vortex sound generation in a lined duct.

The sound generated by a vortex moving across a duct section lined with porous materials and the corresponding vortex dynamics are studied numerically in the present investigation. The combined effects of the effective fluid density, the flow resistance, the length, and the thickness of the porous linings on the vortex dynamics and sound generation are examined in detail. Results show that stronger sound radiation will take place when the length and the thickness of the porous linings are increased or when the effective fluid density is reduced. The flow resistance can only result in stronger sound radiation within a range whose width depends on the above-mentioned system parameters. Such sound amplification cannot be achieved when the initial vortex height gets closer and closer to the duct centerline. The present results also indicate the strong correlation between vortex acceleration and the sound radiation under the actions of the porous linings.