A Study On The Efficient Microcosmic Algorithm For Multscale Combustion

There are remaining unclear mechanisms of the fluid and combustion in multi-scale supersonic combustion phenomena,where the complicated coupling between physics and chemistry and complex reaction kinetic mechanism bring countless difficulties to the numerical study on it.In this paper,we take advantage of the direct simulation of Monte Carlo(DSMC)method in predicting the non-equilibrium transport and strong discontinuous to perform a microcosmic algorithm investigation on the micro-scale combustion phenomenon,taking the fundamental study on the multi-scale shock/turbulence/combustion interaction as the starting point of this paper.Some contribution works has been accomplished on algorithms and mechanisms.Considering the works on the algorithm,this paper extends the traditional single vibrational mode into multi-vibrational mode so that the developed algorithm can be used to predict the combustion problem with polyatomic molecules.Moreover,we successfully develop the DSMC-QK algorithm which can solve some multi-scale flow problems with coupling the complex combustion phenomena,providing algorithmic supports for the fundamental studies on micro-scale combustion problems.Considering the works on the shock/combustible vortex interaction,we observe a new phenomenon that the heat release improves the production of the dilatational vorticity production but not the net vorticity,which results from the strong energy transport under the current condition.More specifically,the energy transport changes the way of dilatational vorticity transport,meanwhile,it also contribute to the kinetic dissipation of the flowfield.This providesnew insights into the mechanism study of the heat conduction and viscosity during the shock/vortex interaction.The current works focus on the above contributions and research objectives,and the main investigated contents and corresponding conclusions can be stated as below:(1)Developing the efficient microscopic algorithm for multi-scale combustion problems.With the use of the physical quantum-kinetic chemical reaction model,we develop the DSMC-QK algorithm for the multi-scale combustion system in which the traditional single vibrational mode is transformed into multi-vibrational mode.The current algorithmic works support the fundamental and theoretical investigation of multi-scale combustion phenomena.(2)The establishment of an assessment strategy for algorithms in multi-scale flow coupling combustion problems.We evaluate the ability of the DSMC-QK method using a decoupling-to-coupling way,which results in that the DSMC-QK method is much accurate in predicting the shock structure,chemical equilibrium state and the shock/reaction coupling features.(3)The study of the micro scale shock/flammable vortex interaction.The numerical result shows that the vorticity generated by shearing plays a dominant role in the micro-scale interaction mechanism.Considering the shock/flammable vortex interaction,we observe that the heat release by combustion increases the production of the dilatational vorticity,while it does not promote the vorticity generation.More specific study shows that the energy transport under the strong heat conduction condition changes the transport way of the dilatational vorticity,meanwhile,it increases the kinetic dissipation of the flow field.This observation provides a new insight for the study of the mechanism of the heat conduction and viscocity during the shock/vortex interaction.