Numerical research on blunt body shock-induced oscillating combustion phenomena

An improved uncoupled solver of non-equilibrium flow wasused to split the axisymmetric Euler equations for a reacting flow. Inviscidflux was calculated with fifth-order WENO scheme. Simplified implicitformulation was adopted to deal with the stiffness generated by the chemicalreacting source term of species equations. Time integration was performedwith two-order TVD Runge-Kutta scheme. At the flow Mach number M of 4.48 and4.79, shock-induced oscillating combustion phenomena around blunt body inH₂/Air mixture were calculated. It shows that the numerical results aremore sensitive to the grid refinement on normal direction than on flowdirection. To get accurate solution, there must be enough grid nodes in theheat release zone. At the flow Mach number of 4.48, sensitive analysis ofdifferent reaction mechanisms were studied. At the given experimentalconditions, the values of induction time calculated from J and B-Wmechanisms are close to each other and their calculated frequencies nearlyequal to the experimental results. Density-time distribution along thestagnation streamline from J and B-W mechanisms agree well with McVey-Toongtheory. Induction time calculated from JM mechanism is longer than others,and the calculated oscillating frequency is lower than experimental results.At flow Mach number of 4.79, calculated frequency of J mechanism agrees withexperimental result. B-W mechanism is sensitive to fluctuations offlowfield, and its release time is short. Fiercely oscillating combustionfront would easily lead to local detonations, which made the pressurehistory of stagnation point disordered. Due to using the fifth-order WENOscheme, relatively high-resolution of present calculation can be obtained.