To investigate influence mechanism of the second viscosity on internal flow of a normal shock wave, one-dimensional Navier-Stokes equations are numerically solved. It indicates that the second viscosity has a smoothing effect on density, heat flow and energy distribution in the shock wave, which results in a decrease of peak value of heat and entropy flows, and an increase of shock thickness. Due to the production of normal viscous dissipation, some lost mechanical energy is converted into internal energy. As considering the second viscosity, density distribution and shock thickness are greatly improved. They are in good agreement with experimental data. In addition, Knudsen number is obtained 0.12≤Kn≤0.4 within Mach number range from 1.2 to 10. It indicates that Navier-Stokes equations with the second viscosity simulate normal shock structure more accurately.

With kinetic and continuum theories of bulk viscosity coefficient, bulk-viscosity effect on two-dimensional toroidal shock-wave focus (Mach number Ma=2.0) is studied numerically. It shows that bulk-viscosity effect on toroidal shock-wave focusing is not negligible for perfect gases. Due to bulk viscous effect in compressible flows, pressure, temperature and density at the central focus perform 20% reduction, 10% increase and 30% reduction, respectively. Compared with rotational mode, shock wave focusing present obvious bulk-viscosity effect in vibrational mode, since bulk viscous stress has same order of magnitude with thermodynamic pressure.

According to advection upstream splitting method,a flux splitting method called K-CUSP is proposed.The greatest difference between K-CUSP and two traditional CUSP schemes,namely H-CUSP and E-CUSP,is splitting of total energy:All kinematic quantities and thermodynamic quantities should be separately split into convective term and pressure term by K-CUSP scheme.Numerical tests indicate that:① K-CUSP scheme inherits the simplicity and robustness of FVS scheme.It is less prone to pressure overshoot after shock and no oscillations in expansion area,which is better than AUSM and WPS schemes.② K-CUSP scheme also inherits resolution of FDS scheme.Shock resolution is almost the same with H-CUSP and E-CUSP schemes.Contact discontinuity resolution is better than FVS schemes,a little worse than Roe,AUSM and WPS schemes.However,velocity of contact discontinuity in AUSM and WPS schemes exist large oscillation,while our scheme does not.

Three-dimensional algorithms solving laminar Navier-Stokes equations coupled with chemical reaction and transportation equations are developed.Detailed flow field and distribution of yield,dissociation and pumping rates and small signal gain are obtained which cannot easily be got in experiments.The reason that experimental results are not as good as that in theories is analyzed.Furthermore,a better way to operate the system is suggested.It is shown that the mixing and chemical process in a nozzle of limited length is not complete due to the high speed in supersonic mixing zone and low mixing efficiency.Higher iodine concentration for speeding up chemical reaction causes insufficient of singlet oxygen,so as an unreasonable gain.A primary flow without buffer gas is claimed necessary and essential to reduce flow velocity and assure mixing process and chemical reaction accomplished before arriving the cavity.With an appropriate flow rate ratio,a small signal gain can reach 1.3% cm^-1.

Three-dimensional CFD technology is applied in an RADICL model by solving laminar Navier-Stokes equations and transportation equations. Mixing and reaction of flows, gas-dynamics fields and gains are studied at different jet intensity. It is found that the penetration depth plays an important role for special distribution of small signal gain macroscopically. Strong impinges between jets and unsteady structures are induced by over-penetration in mixing flow field.