Flow turning and admittance correction - An experimental comparison

The proper Way of incorporating viscosity-related acoustic losses into solid propellant rocket motor linear stability analyses has been an open question for years. Mainly, two distinct theories are proposed in the literature and are referred to as the flow turning and admittance correction approaches. The two theories are briefly presented, then competitively used to derive composite solid propellant pressure-coupled response functions from experiments. The experimental setup is succinctly described and experimental results are presented. Comparisons between the theoretical approaches are made on the basis that the proper approach should yield equal values for the propellant response function, irrespective of particular grain geometry, provided that the same mean chamber pressure and frequency are achieved in the chamber. Results favor the admittance correction approach, as the flow turning approach seems to overestimate viscous losses.