Numerical Study Of The Non-equilibrium Effect Induced By Particle Relaxation On High-speed Flows

The propagation and reflection of a shock wave as well as the shocked-induced in-terfacial instability are significant physical problems in compressible high speed flows.Much attention has been paid to them,and previous studies mainly focus on such prob-lems in a pure gas environment.Nevertheless,in real applications such as the explosive safety in coal mines,high speed flight in rain,shock-particle interactions in solid-fuel booster,the environmental gas is usually seeded with small particles,which is usually called dusty gas.In the dusty flow,particles and gas exchange their momentum and energy continuously,and hence produce a non-equilibrium effect,which would change the fluid properties and the flow characteristics.In this thesis,we mainly investigate the non-equilibrium effect caused by the particle relaxation on compressible flows using a compressible multi-phase solver based on the non-structural adaptive grid technique.The main content is concluded as follows:First,the compressible two-phase problem of injecting static particles with differ-ent temperatures into one-dimension pipe flow is investigated numerically.It is found that the continuous momentum and energy exchanges between particles and gas during the injection process can give rise to unsteady wave patterns.The coupling of particles and gas flow is analyzed in detail and the dependence of the generated wave patterns on the flow parameters is highlighted.It is found that the variation of the particle temper-ature and the flow velocity can alter the intensity and structure of the unsteady wave.In addition,through solving the thermodynamic parameters in different flow regions,a phase diagram showing the variation of the wave pattern intensity versus the flow parameters is obtained,which illustrates the quantitative influence of the flow parame-ters on the wave pattern.The present study is of fundamental importance for studying complex dusty flows in the two-dimensional geometry.Then,the dusty shock reflection over a double wedge with different length scales is systematically studied using the adaptive multi-phase solver,and the non-equilibrium effect caused by the particle relaxation is found to significantly influence the initial con-ditions of the shock reflection on the back wedge and the subsequent shock reflection process.Specifically,it behaves differently for double wedges with different length scales of the first wedge L1.For a double wedge with a L1 relatively longer than the particle relaxation length ?,the equilibrium shock dominates the shock reflection and seven typical reflection processes are obtained,which is similar to the pure gas counter-part.For a double wedge with a Ll shorter than A,the non-equilibrium effect manifests more evidently,i.e.,three parts of the dusty shock system including the frozen shock,the relaxation zone and the equilibrium shock together dominate the reflection process.As a result,the shock reflection is far more complicated than the pure gas counterpart and eleven transition processes are found under various wedge angles.These findings give a complete description of all possible processes of dusty shock reflection over a double wedge,and may be useful for better understanding the non-equilibrium shock reflection over complex structures.Finally,a series of simulations about the interaction of a shock wave with a dusty gas cylinder is carried out with the adaptive multi-phase solver.It is found that the non-equilibrium effect caused by the particle relaxation influences the velocity of transmis-sion shock,the relaxation length,the pressure peak,and the evolution of the cylindrical interface.The numerical results show that as the particle radius is increased,the gas in the cylinder closer to frozen flow,the curvature of the transmission shock as well as the pressure peak reduces,whereas the velocity of the transmitted shock and the relaxation length increase.Particularly,for particles with a large radius,at late stages the gaseous interface departs from the particle interface.and the particles also escape from the vor-tex core.The increase of the vorticity strength and particle size will exacerbate these phenomena.