Fully kinetic Particle-in-cell (PIC) simulations are performed to study the structure of collisional plasma shock waves with different Mach numbers. It is found that for low-Mach shocks, the spatial gradient of physical quantities near the shock front is gentle, corresponding to small Knudsen numbers, and the plasma transport properties (e. g. viscosity, heat flux) are well described by the classical transport theory. The simulated shock structure is consistent with that obtained from the numerical solution of the two-fluid equations. With increasing Mach numbers, the spatial gradient of physical quantities near the shock front becomes steep (i. e. the Knudsen number is increased), and the influence of kinetic effects on plasma transport properties become significant. For high-Mach shocks, kinetics effects come into play mainly in the following two aspects: (1) enhanced ion viscosity and heat flux due to the precursor ions and (2) nonlocal transport effects on the electron heat flux. Kinetic effects can significantly influence the shock wave structure by changing the plasma transport properties.

The influence of plasma effect on the shock wave and hydrodynamic instabilities is a widely concerned problem in the current research of laser fusion. However, due to the limitations of the numerical simulation methods, there is still a lack of research tools on this issue. In this work, a hybrid fluid PIC(particle-in-cell) simulation method is established tentatively. Electrons are described by a massless fluid, and multi-component ions are described by PIC method; The fluid motion is obtained by solving the equations of electro-magnetohydrodynamic, and the electromagnetic fields are obtained by solving Ohm's law and Faraday's law. Aiming at the plasma condition of laser fusion, we use hybrid fluid-PIC simulation to study the shock wave structure and its characteristics in high energy density conditions, and the influence of plasma effect on the evolution of hydrodynamic instabilities. Hybrid fluid-PIC physical modeling provides a new research method for studying the effect of plasma effect on shock wave and hydrodynamic instabilities under high energy density.

With assumption that the lubricant is a mixture of fluid and bubble nuclei and its distribution is homogeneous, we introduce a dynamic model of cavitation and couple it with Reynolds equation of hydrodynamic lubrication of plain bearings. The model under lubrication state is sovled with numerical simulation. Euler method, a 4-5th order Runge-Kutta method and a finite difference method are used to explore effect of initial gas content on axis trajectory and lubrication characteristics.

A Darcy-Brinkman-Forchheimer model based lattice Boltzmann method is conducted to the simnlation of double-diffusive natural convection in an inclined square porous enclosure. Effects of porosity (0.2≤ε≤0.9), Rayleigh number (10³≤Ra≤10⁶), buoyancy ratio (-4≤Br≤2) and inclination angle (0°≤γ≤80°) on the local and total entropy generation are systematically investigated. It shows that as ε and Ra increased, peaks of local entropy generation due to heat transfer, fluid friction and mass transfer grow higher and the contribution of fluid friction to total entropy generation increased prominently. In addition, the clear fluid term has more influence on fluid friction entropy generation. Br=-1 is a critical value for the change of local entropy generation distribution. At the same time, the total entropy generation tends to zero. With the increase of inclination angle, the high entropy generation region of local fluid friction entropy generation moves clockwise. The maximum entropy caused by clear fluid term and Darcy dissipation term appears at 40° and 60°, respectively.