An iDdQ(q-1) MRT LB model with external force term is proposed with multi-scale expansion and inverse design method. It recovers to incompressible Navier-Stokes equation with external force term under low Mach number assumption. With simulations of Poiseuille flow, pulsatile flow in a three-dimensional square channel, and two-dimensional Taylor vortex flow in a square box, it is found that numerical results are in good agreement with analytical solutions. In addition, spatial accuracy of the model reaches second order, which verifies effectiveness of the model in simulating steady and unsteady incompressible flows driven by external forces.

A scheme of convolutional perfectly matched layer (CPML) absorbing boundary condition (ABC) is proposed, which is used to truncate finite-difference time-domain (FDTD) method modeling transient electromagnetic (TEM) response. It derives specially CPML formulation dealing explicitly with divergence of magnetic induction and conceives an algorithm calculating convolutional term of z component. Then, the scheme is validated by numerical modeling of a homogeneous half-space model. The results indicate that efficient calculation of TEM is achieved.

A method is developed with a relationship between volume of fluid and velocity and molecular dynamics method.Flow velocity of liquid argon is calculated in simulations of three-dimensional Poiseuille flows and cavity flows.It shows that calculated flow velocities are basically consistent with that obtained from traditional molecular dynamics method.The method can be applied to various kinds of channel flows.For flows driven in square cavities,calculated velocities are roughly the same,but the boundary velocities are varied widely.Accuracy of the new method is better with a faster convergence rate.

An improved particle tracking algorithm based on unstructured grids and hybrid grids with arbitrary polygon faces is presented.A dummy triangulation of non-planar polygon faces is carried out as tracking particles across arbitrary hybrid cell faces.Feasibility and reliability are shown through numerical examples.cpu time of the algorithm is compared with that of two algorithms introduced by Haselbacher et al for particles spray into a fixed chamber.The speed up can reach as high as 47% for 10000 particle tracking.

An algorithm with unstructured girds is introduced in which coupling of density and temperature is considered.Static enthalpy equation is employed to construct relation between temperature correction and pressure correction.As in Rhie-Chow method,temperature and pressure corrections of grid interfaces are interpolated by static enthalpy equation and omitting neighbour temperature correction as in the velocity-pressure coupling in SIMPLEC.CGNS is taken as I/O in the in-house unstructured FVM code.For combustion simulation,Arrinius-Eddy dissipation model is employed.

In a fluid model of DBD(dielectric barrier discharge) with atmospheric pressure, a finite difference algorithm with fixed grids is adopted to solve two-dimensional fluid continuous equations by using four-order and six-order phase error FCT(flux-corrected transport) methods, respectively. With uniform initial conditions, spatial evolution of the electron density during avalanche propagation is studied. Two FCT algorithms are compared in detail. The simulation agrees with theoretical and experimental results. It demonstrates high accuracy and precision of the FCT method.

An unstructured hybrid grid computational method is proposed,in which CGNS API(CFD General Notation System Application Programming Interface) is taken as pre- and post-processing and FVM(Finite Volume Method) is taken as a PDE(Partial Differential Equation) solver.In the pre-processing,the interior mesh faces and boundary mesh faces are indexed with hash table method for the requirment of the FVM solver.The results of the solver are written into original CGNS files with which the post-processing is dealt with by post-processing softwares,such as tecplot,fluent and CFX.For the solver,a cell centered FVM is applied to solve the coupled pressure and velocities with the SIMPLEC(Semi Implicit Method for Pressure Linked Equation Consistent).Two numerical examples are shown.

The fiber fine structure in solar radio bursts carries small-scale magnetic field information in the initial phase of the burst.We deal with fiber structures to analyze the frequency drift rate.The background is obtained by a wavelet transformation.With a subtraction of the background and a threshold processing,the fiber structures are seperated.We select continuous segments in each channel.The cubic spline interpolation is used to fit the intensity-time relation with which the moments of intensity maxima are determined.Finally,the drift rate is calculated with linear regression.The algorithm is used to calculate frequency drift rate of the radio fiber event on 21-April-2002.The mean frequency drift rate obtained is beween -0.041 0~-0.013 8 GHz·s^-1.

A parallel algorithm for time-independent Monte Carlo transport is successful since particles are independent and they are distributed to multiple processors.However,for time-dependent Monte Carlo transport problems, the parallel efficiency reduces and the parallel scale is limited due to the communication of scattering source attribute and meshes in each time-step.We propose two algorithms in them adaptive processor assignment and optimized processor choice are obtained.With a Monte Carlo stratified sampling technique for scattering source treatment the communication cost is reduced greatly.The parallel expandability is improved.A large speedup over the basic algorithm is obtained.

A model is proposed to study numerically the dynamics for the energy transportion of amide Ⅰ vibrations in proteins.The results show that there exists static and moving localized models in the mode and thus it may provides alternative mechanism of the energy transport in protein molecules.

A two parameter numerical inverse method of differential equation with only one complementary condition is presented.According to this principle a simultaneous inverse algorithm of lithology parameter and seismic source function of one dimensional wave equation is given in detail.Theoretical analysis and numerical examples demonstrate the existence of solution,stability and accuracy of the method.The method provides a suitable way to solve the difficulty of unknown source function in practical seismic exploration.The numerical results show the feasibility of the algorithm.

This paper presents a new method, FR method, to solve the inverse problems of acoustic wave equations. FR method is a general numerical inversion algorithm of acoustic wave equations. It can be used to one, two or three dimensional inverse problems with any different boundary conditions. The basic principle and formulae are derived carefully in the paper, and numerical examples of one and two dimensional inverse problems are given. The numerical results show the accuracy and stability of the method.