Moving shocks through metallic grids: their interaction and potential for blast wave mitigation |
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Authors: | Y Andreopoulos S Xanthos K Subramaniam |
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Institution: | (1) Experimental Fluid Mechanics and Aerodynamics Laboratory, Department of Mechanical Engineering, The City College of the City University of New York, New York, NY 10031, USA;(2) Structural Solid Mechanics Laboratory, Department of Civil Engineering, The City College of the City University of New York, New York, NY 10031, USA |
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Abstract: | Numerical simulations and laboratory measurements have been used to illuminate the interaction of a moving shock wave impacting
on metallic grids at various shock strengths and grid solidities. The experimental work was carried out in a large scale shock
tube facility while computational work simulated the flow field with a time-dependent inviscid and a time-dependent viscous
model. The pressure drop measured across the grids is a result of two phenomena which are associated with the impact of the
shock on the metallic grids. First are the reflection and refraction of the incoming shock on the grid itself. This appears
to be the main inviscid mechanism associated with the reduction of the strength of the transmitted shock. Second, viscous
phenomena are present during the reflection and refraction of the wave as well as during the passage of the induced flow of
the air through the grid. The experimental data of pressure drop across the grid obtained in the present investigation are
compared with those obtained from computations. The numerical results slightly overpredict the experimental data of relative
pressure drop which increases substantially with grid solidity at fixed flow Mach numbers. The processes of shock reflection
and refraction are continuous and they can be extended in duration by using thicker grids that will result in lower compression
rates of the structural loading and increase the viscous losses associated with these phenomena which will further attenuate
the impacting shock. Preliminary theoretical analysis suggests that the use of a graded porosity/solidity material will result
in higher pressure drop than a constant porosity/solidity material and thus provide effective blast mitigation.
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Keywords: | Shock-blast waves Shock tubes Grid generated turbulence |
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