We propose a fast random simulation strategy based on differentially weighted MC. The strategy improves computation efficiency significantly, and guarantees enough calculation accuracy, thus coordinates contradiction between computation cost and computation accuracy. The main idea is based on majorant kernel. It is possible to transfer a traditional coagulation kernel to a majorant kernel through splitting and amplifying slightly. The maximum of majornant kernel is obtained by single looping over all simulation particles. The maximum majornant kernel is used to approximate the maximum coagulation kernel in particle population, and is further used to search coagulation particle pairs randomly with acceptance-rejection method. The waiting time (time-step) for a coagulation event is calculated by summing coagulation kerenls of particle pairs involved in acceptance/rejection processes.. Double looping in normal Monte Carlo simulation is avoided and computation efficiency is improved greatly.

An LB-based gas-solid two-phase model with two-way coupling is developed considering feedback forcing of particles in evolution equation of fluid particles. Smagorinsky subgrid model is also introduced in simulation of flow field with high Reynolds numbers. Classic particle-laden flow over a backward facing step is simulated and velocity profiles of gas phase and particles (considering one-way coupling and two-way coupling respectively) are compared with experimental results. The results of two-way coupling LB model are obviously better than these of one-way coupling LB model. Furthermore, preferential concentration of particles with different Stokes numbers (St) is investigated. It is found that small particles (St~0(0.1)) show better following behaviors with gas phase and are uniformly distributed in the flow field. Particles with moderate Stokes numbers (St~0(1)) are hard to be entrained into the vortex and show strong preferential concentration. On the other hand, large particles (St~0(10)) can enter into the vortex because of great inertial and are distributed more uniformly in flow field.

We present an extension of lattice-Boltzmann-lattice-gas method proposed by Masselot and Chopard for gas-solid flows,in which the drag force between gas and solid is considered.The method is applied to particles in a driven cavity flow.Effects of Stokers number and total number of particles are analyzed.Simulation results are compared with previous works.It shows that the proposed LBE-LGA method can serve as a promising tool for simulating gas-particle flows.

Zone method has been commonly used in radiative heat transfer calculation in industry, but it has difficulty in calculating multi integration for solution of direct radiative exchange areas, and also in treating with non uniformal gas absorbing and scattering. this paper presents Monte-Carlo method for solution of direct radiative exchange areas, compiling the corresponding program such areas between the zones of enclosed square system filled with uniform absorbing medium are calculated, and comparing the numerical results with analytical ones.