Numerical Simulation Of Shock Wave And Expansion Propagating In Spherical Array With Large Porosity

The interaction of a shock wave,or an expansion wave with a solid particle group is an important research topic in supersonic two-phase flow gas dynamics.The theory of shock wave and expansion wave to drive a solid particle group is also widely used in military,medical,aerospace fields,etc.So far,many scholars at home and abroad have studied the flow phenomena of solid particles driven by shock waves and expansion waves and conducted investigations using experimental and numerical simulation methods.In order to study the air flow characteristics of shock waves and expansion waves propagating through structured sphere arrays with large porosities,by solving the three-dimensional RANS equations and the realizable k-epsilon turbulence model via ANSYS FLUENT.The air flow fields that are induced by shock waves'and expansion waves'propagation through different particle volume fraction,different Mach number of the incident shock waves(for shock waves)and different rupture pressure ratios(for expansion waves)are numerically simulated on the Fluent software platform.The main research objective is to analyze the influence of these parameters on the propagation characteristics inside the sphere arrays and the drag coefficients of the spheres.The results show that:1.In the process of shock waves propagating through a sphere array,the reflectioneffect of a staggered cubic(SC)sphere array against an incident shock wave is quite different for different incident shock Mach numbers.As the incident shock Mach number increases,the aggregation and superposition effect of the reflected shock wave increases.There is a critical value for the incident shock Mach number which makes the reflection effect stable.For a given arrangement of spheres under a certain operating condition,there exists a critical volume fraction.A reflected shock wave front is not able to form unless the practical volume fraction of spheres is larger than it.2.In the process of expansion waves propagating through a sphere array,the reflected expansion waves will appear.For smaller rupture pressure ratios,these reflection waves exist stably for a long time and therefore form a regular wave front more easily,furthermore,the drag coefficients of the spheres increase.For a given arrangement of spheres under a certain operating condition,there exists a critical volume fraction.A reflected expansion wave front is not able to form unless the practical volume fraction of the spheres is larger than it.Under a restriction of larger porosities,the increase of volume fraction is in favour of the enhancement of inference of the reflected expansion waves,and thus the drag coefficients of the spheres increase.Comparing three different arrangements of spheres,namely,crystal cubic(CC),bis-face-centered cubic(BFCC),and staggered cubic(SC)arrangements,the drag coefficients are sorted from largest to smallest as SC,BFCC and CC arrangements mainly due to the difference of interval distances of the neighboring spheres.