Shock Attenuation In Baffle Systems

Abstract: The purpose of shock attenuating baffle systems is to reduce the peak pressure of shock waves exiting into the environment. In this study, numerical and experimental tools are used to investigate how the layout of a generic baffle chamber influences peak pressure and impulse associated with a shock of Mach number 1.55 leaving an open shock tube with circular cross section. An adaptive, second-order, finite-volume scheme solving the axisymmetric Euler equations was used for the numerical simulation, while flow visualisation and pressure transducers were the main diagnostics in the experiments. The outer contour of the baffle chamber was given a bespoke aspheric shape that allowed one to visualise the internal flow with minimum distortion. Number, angle, and layout of the equidistantly arranged baffles were varied in a limited parameter study in order to determine general trends and dependencies between shock attenuation and baffle chamber geometry. The multi-segment layout of the baffle chamber led to multiple shock diffractions and a resulting wavelet sequence with low peak pressures. Numerical data showed a strong correlation to experimental results for early time-steps but degraded with increased time and distance downstream. Organised porosity of the baffles in the shape of regular slots increased the number of diffraction processes within the baffle chamber but was not seen to significantly improve peak pressure reduction outside of the chamber when compared to solid baffles. Keywords: shock wave attenuation, baffle system, density-sensitive flow visualisation