Numerical Simulation Of Shock-Flame-Boundary Layer Interactions

In this thesis,numerical simulation of shock-flame-boundary layer interactions have been investigated,while the flame acceleration and Detonation-to-Detonation Transition(DDT)process caused by shock-flame-boundary layer interactions have been studied.In order to capture complex flow structures,which are involved in supersonic turbulent combustion,such as shock wave,turbulent flow,boundary layer and so on,a hyperviscosity shock-capturing technique based on the TTGC(Two-step Taylor-Galerkin C)finite element scheme with third-order accuracy both in time and space has been proposed.A bulk viscosity and a shear viscosity,which are related to the local grid dimension,are introduced to improve the shock-capturing accuracy and the reliability in the shock-turbulence interaction capture technology.The classical one-dimensional shock tube case,one-dimensional Shu-Osher case,two-dimensional shock-bubble interactions and two-dimensional shock-cylinder interactions are used to verify the proposed method.The results show that the proposed method can capture the complex flow information effectively,such as shock wave,flame,turbulence and boundary layer in supersonic reaction flow field.In addition,the numerical dissipation near the complex flow,such as shock wave,can be controlled perfectly.Furthermore,the present method,which combines LES technology and dynamically thickening flame model,is applied to the numerical simulation of shock-flame-boundary layer interactions.The reaction gas is considered as a methane-air mixture with a stoichiometric ratio,for which reaction mechanism is described by the two-steps scheme with six components.The calculation results show that the presented method can be effectively applied to the calculation of supersonic turbulent flow field.Based on the numerical method proposed in this thesis,the characteristics of shock bifurcations,caused by the interactions of shock and boundary layer have been studied.The results show that bifurcated height firstly increases with the movement of reflected shock,then fluctuates within a certain range,and bifurcated angle fluctuates within a certain range.With the increase of incident shock intensity,the bifurcated height increases,while the bifurcated angle decreases.Furthermore,the effects of shock bifurcation on shock-flame interactions have been investigated.Under the conditions of various incident shock intensities and various activation energies,the influence of bifurcated structure on the accelerated propagation of flame has been studied.It has been found that the bifurcated structure has little effects on the flame acceleration at lower incident shock intensity(M = 1.9)and higher activation energy.The phenomenon of flame acceleration is not obvious.However,under the conditions of higher incident shock intensity(M = 2.1)and low activation energy,the phenomenon of flame acceleration in bifurcated structure has been observed.At the same time,the Mach stem and several local hot spots have formed close to the symmetry plane,which lead to intense burning,even DDT.