Measurement/Model of Effects of Grazing Flow on Resonator Impedance

The proposed SBIR Phase II research project is divided into four parts. The principal objective of the first part is to conduct hot-wire measurements to assess the accuracy of Dean?s Two Microphone Impedance Measurement Method. They will also be used to calibrate CAA numerical codes. The principal objective of the second part is to develop a computationally simple 2-DOF resonator impedance model. The model will include non-linearity of the cavity sound particle velocities pumped into/out-of the inner/outer orifices. The model will be calibrated by Impedance measurements as a function of SPL and grazing flow speed.The principal objective of the third part is to use hot-wires to measure cavity inflow/outflow sound particle velocities near the orifices of multiple orifice resonators, backed by a common cavity. These measurements should provide fundamental understanding of orifice-to-orifice interaction. They will be used to assess potential resonator bandwidth improvement as a function of orifice spacing in grazing flow applications.The principal objective of the fourth part is to design and construct a prototype low self-noise probe microphone to measure broadband sound in high-speed flow duct applications. The performance of the prototype probe will be validated in the NASA LaRC 2-in by 2-in wind tunnel.