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1.
The paper presents the developed physical and mathematical models, calculation procedure based on finite-element method, and
also the software for the numerical studying the processes of the non-stationary conjugate heat exchange and phase transition
during the surface processing with high-concentrated energy fluxes with stationary, pulse, and movable heat sources (fusing
of coatings, surface layer quenching, surface cleaning, etc.). The proposed and realized method permits to study the processes
within a wide range of the power density of external heat fluxes q∈[107; 1014] W/m2 with significantly different spatial and temporal scales. The results presented are of interest for understanding and simulation
of the processes occurring at the surface processing of the coatings and materials with high-concentrated energy fluxes.
The project has been financially supported by the Russian Foundation for Basic Research (Grant No. 07-08-00209). 相似文献
2.
文章通过对EFM(effective field modeling)模型进行简化, 消除了原模型的非守恒性项和非双曲性特性项, 发展了一种基于密度的气液两相流模拟方法: ρ-VOF方法.利用体积分数信息对控制单元内的自由界面进行重构, 得到了控制单元内流体的空间分布, 并采用AUSM+-up格式获得考虑气液流体接触间断信息的对流通量.新方法可统一处理激波间断和接触间断的相互作用, 保持自由界面的尖锐性, 并且其计算量与自由界面的空间复杂度无关.最后, 数值模拟了液体激波管气液激波管和气体激波跨二维液滴传播等问题, 并与文献结果进行对比, 验证了本方法在气液两相流模拟中的准确性. 相似文献
3.
4.
E. A. Chinnov S. M. Kharlamov A. V. Saprykina O. V. Zhukovskaya 《Thermophysics and Aeromechanics》2007,14(2):241-246
The fluorescence method was used to measure the instantaneous thickness field of the falling nonisothermal water film. The
process of rivulet formation in a heated film was registered.
Measurement averaging allowed determination of the degree of transverse deformation of a film. In the lower half of the heater
within the interrivulet zone of the non-isothermal film, the wave amplitude decreases with a rise of the heat flux and reduction
of the average thickness. Two zones of the heat flux effect on liquid film deformation were distinguished. At low heat fluxes,
the film flow is weakly deformed. At high heat fluxes the thermal-capillary forces provide formation of rivulets and a thin
film between them.
The work was financially supported by the President of RF (NSh-6749.2006.8), Russian Foundation for Basic Research (Grants
Nos. 05-08-33325-a, 06-01-00360-a), National Center on Science and Innovations (State contract No. 02.438.11.7002), and SB
RAS (Interdisciplinary Integration Project No. 111). 相似文献
5.
Pressure-based flow solvers couple continuity and linearized truncated momentum equations to derive a Poisson type pressure correction equation and use the well known SIMPLE algorithm. Momentum equations and the pressure correction equation are typically solved sequentially. In many cases this method results in slow and often difficult convergence. The current paper proposes a novel computational algorithm, solving for pressure and velocity simultaneously within a pressure-correction coupled solution approach using finite volume method on structured and unstructured meshes. The method can be applied to both incompressible and subsonic compressible flows. For subsonic compressible flows, the energy equation is also coupled with flow field and the density of fluid is obtained by equation of state. The procedure eliminates the pressure correction step, the most expensive component of the SIMPLE-like algorithms. The proposed coupled continuity-momentum-energy equation method can be used to simulate steady state or transient flow problems. The method has been tested on several CFD benchmark cases with excellent results showing dramatically improved numerical convergence and significant reduction in computational time. 相似文献
6.
Liang Pan Guiping Zhao Baolin Tian Shuanghu Wang 《Journal of computational physics》2012,231(22):7518-7536
Numerical methods for the Baer–Nunziato (BN) two-phase flow model have attracted much attention in recent years. In this paper, we present a new gas kinetic scheme for the BN two-phase flow model containing non-conservative terms in the framework of finite volume method. In the view of microscopic aspect, a generalized Bhatnagar–Gross–Krook (BGK) model which matches with the BN model is constructed. Based on the integral solution of the generalized BGK model, we construct the distribution functions at the cell interface. Then numerical fluxes can be obtained by taking moments of the distribution functions, and non-conservative terms are explicitly introduced into the construction of numerical fluxes. In this method, not only the complex iterative process of exact solutions is avoided, but also the non-conservative terms included in the equation can be handled well. 相似文献
7.
The developed general physical-mathematical model, FEM-based calculation procedure as well as the software were in practical
use to simulate the processes of the non-stationary conjugate heat exchange and phase transformations during the processing
of the surface with a high-concentrated energy fluxes, with a stationary, pulsed, and movable heating sources (the processing,
including the surface fusing with a quasilaminar plasma jet, transfer electric arc and impulse electron beam; cleaning of
the metal substrate surfaces from an oxide layer with the aid of a cathode vacuum arc, etc). The processes of practical importance
with considerably different spatial and temporal scales featuring the density of the heat fluxes power q ∈ [107; 1014] W/m2 have been studied.
The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-08-00209). 相似文献
8.
The local discontinuous Galerkin (LDG) method is a spatial discretization procedure for convection–diffusion equations, which employs useful features from high resolution finite volume schemes, such as the exact or approximate Riemann solvers serving as numerical fluxes and limiters, which is termed as Runge–Kutta LDG (RKLDG) when TVD Runge–Kutta method is applied for time discretization. It has the advantage of flexibility in handling complicated geometry, h-p adaptivity, and efficiency of parallel implementation and has been used successfully in many applications. However, the limiters used to control spurious oscillations in the presence of strong shocks are less robust than the strategies of essentially non-oscillatory (ENO) and weighted ENO (WENO) finite volume and finite difference methods. In this paper, we investigated RKLDG methods with WENO and Hermite WENO (HWENO) limiters for solving convection–diffusion equations on unstructured meshes, with the goal of obtaining a robust and high order limiting procedure to simultaneously obtain uniform high order accuracy and sharp, non-oscillatory shock transition. Numerical results are provided to illustrate the behavior of these procedures. 相似文献
9.
Analytical solutions of governing equations of various phenomena have their irreplaceable theoretical meanings. In addition,
they can also be the benchmark solutions to verify the outcomes and codes of numerical solutions, and even to develop various
numerical methods such as their differencing schemes and grid generation skills as well. A hybrid method of separating variables
for simultaneous partial differential equation sets is presented. It is proposed that different methods of separating variables
for different independent variables in the simultaneous equation set may be used to improve the solution derivation procedure,
for example, using the ordinary separating method for some variables and using extraordinary methods of separating variables,
such as the separating variables with addition promoted by the first author, for some other variables. In order to prove the
ability of the above-mentioned hybrid method, a lot of analytical exact solutions of two-buoyancy convection in porous media
are successfully derived with such a method. The physical features of these solutions are given.
Supported by the National Natural Science Foundation of China (Grant No. 50576097) and the National Basic Research Development
Program of China (Grant No. 2007CB206902) 相似文献
10.
Mathematical Development and Verification of a Finite Volume Model for Morphodynamic Flow Applications
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Fayssal Benkhaldoun Mohammed Seaï d & Slah Sahmim 《advances in applied mathematics and mechanics.》2011,3(4):470-492
The accuracy and efficiency of a class of finite volume methods are investigated for
numerical solution of morphodynamic problems in one space dimension. The governing
equations consist of two components, namely a hydraulic part described by the shallow
water equations and a sediment part described by the Exner equation. Based on different
formulations of the morphodynamic equations, we propose a family of three finite volume
methods. The numerical fluxes are reconstructed using a modified Roe's scheme that
incorporates, in its reconstruction, the sign of the Jacobian matrix in the morphodynamic
system. A well-balanced discretization is used for the treatment of the source terms.
The method is well-balanced, non-oscillatory and suitable for both slow and rapid
interactions between hydraulic flow and sediment transport. The obtained results for
several morphodynamic problems are considered to be representative, and might be helpful
for a fair rating of finite volume solution schemes, particularly in long time computations. 相似文献
11.
We present a new three-dimensional hybrid level set (LS) and volume of fluid (VOF) method for free surface flow simulations on tetrahedral grids. At each time step, we evolve both the level set function and the volume fraction. The level set function is evolved by solving the level set advection equation using a second-order characteristic based finite volume method. The volume fraction advection is performed using a bounded compressive normalized variable diagram (NVD) based scheme. The interface is reconstructed based on both the level set and the volume fraction information. The novelty of the method lies in that we use an analytic method for finding the intercepts on tetrahedral grids, which makes interface reconstruction efficient and conserves volume of fluid exactly. Furthermore, the advection of volume fraction makes use of the NVD concept and switches between different high resolution differencing schemes to yield a bounded scalar field, and to preserve both smoothness and sharp definition of the interface. The method is coupled to a well validated finite volume based Navier–Stokes incompressible flow solver. The code validation shows that our method can be employed to resolve complex interface changes efficiently and accurately. In addition, the centroid and intercept data available as a by-product of the proposed interface reconstruction scheme can be used directly in near-interface sub-grid models in large eddy simulation. 相似文献
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J. Vázquez R. González-Palma P.L. López-Alemany P. Villares R. Jiménez-Garay 《Journal of Physics and Chemistry of Solids》2005,66(7):1264-1273
A procedure has been developed for analyzing the evolution with time of the actual volume fraction transformed, for calculating the kinetic parameters and for analyzing the glass-crystal transformation mechanisms in solid systems involving formation and growth of nuclei. By defining an extended volume of transformed material and assuming spatially random transformed regions, a general expression of the extended volume fraction has been obtained as a function of the temperature. Considering the mutual interference of regions growing from separate nuclei (impingement effect) and from the above-mentioned expression, the actual volume fraction transformed has been deduced. The kinetic parameters have been obtained, assuming that the reaction rate constant is a time function through its Arrhenian temperature dependence. The theoretical method developed has been applied to the crystallization kinetics of a set semiconducting alloys, prepared in our laboratory, corresponding to the Sb-As-Se and Ge-Sb-Se glassy systems. The obtained values for the kinetic parameters agree satisfactorily with the calculated results by the Austin-Rickett kinetic equation, under non-isothermal regime. This fact allows to check the validity of the theoretical model developed. 相似文献
14.
以流体比容方法和三阶PPM方法为基础,给出了适用于三级气炮超高速发射过程数值模拟的多流计算方法和计算代码MFPPM。利用Sandia实验室一系列的实验装置及其结果对计算代码进行了验证和确认,获得了较好的数值模拟结果(其中最大相对误差为1.07%),同时对冲击波物理与爆轰物理实验室设计的实验装置进行了数值模拟,计算结果与实验结果相差1.04%。为了更好地满足超高压下材料状态方程的测量,提出了一种带汇聚型的改进装置设计,并给出了相应的数值模拟结果。 相似文献
15.
We present a new second-order accurate monotone finite volume (FV) method for the steady-state advection–diffusion equation. The method uses a nonlinear approximation for both diffusive and advective fluxes and guarantees solution non-negativity. The interpolation-free approximation of the diffusive flux uses the nonlinear two-point stencil proposed in Lipnikov [23]. Approximation of the advective flux is based on the second-order upwind method with a specially designed minimal nonlinear correction. The second-order convergence rate and monotonicity are verified with numerical experiments. 相似文献
16.
Pierre-Henri Maire 《Journal of computational physics》2009,228(18):6882-6915
The goal of this paper is to present high-order cell-centered schemes for solving the equations of Lagrangian gas dynamics written in cylindrical geometry. A node-based discretization of the numerical fluxes is obtained through the computation of the time rate of change of the cell volume. It allows to derive finite volume numerical schemes that are compatible with the geometric conservation law (GCL). Two discretizations of the momentum equations are proposed depending on the form of the discrete gradient operator. The first one corresponds to the control volume scheme while the second one corresponds to the so-called area-weighted scheme. Both formulations share the same discretization for the total energy equation. In both schemes, fluxes are computed using the same nodal solver which can be viewed as a two-dimensional extension of an approximate Riemann solver. The control volume scheme is conservative for momentum, total energy and satisfies a local entropy inequality in its first-order semi-discrete form. However, it does not preserve spherical symmetry. On the other hand, the area-weighted scheme is conservative for total energy and preserves spherical symmetry for one-dimensional spherical flow on equi-angular polar grid. The two-dimensional high-order extensions of these two schemes are constructed employing the generalized Riemann problem (GRP) in the acoustic approximation. Many numerical tests are presented in order to assess these new schemes. The results obtained for various representative configurations of one and two-dimensional compressible fluid flows show the robustness and the accuracy of our new schemes. 相似文献
17.
A numerical model for solving the Boltzmann unsteady non-local kinetic equation for the distribution function of electrons
over energy is constructed. The Boltzmann equation for isotropic part of the distribution function written in natural variables
the kinetic energy — the coordinate was solved by the pseudo-unsteady method. The model was applied for describing the spatiotemporal
evolution of the distribution function of electrons in a uniform electric field. For a model distribution of the electric
field with the “negative” value in the Faraday dark space and the “positive” value in the positive column of the glow discharge,
the main macroscopic parameters of electrons are obtained, the diffusion mechanism of the electron current transfer in the
negative electric field region is confirmed.
The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-02-00781-a) and by State Contract
No. 02.513.11.3242. 相似文献
18.
We investigate the acoustic wave propagation in bubbly liquid inside a pilot sonochemical reactor which aims to produce antibacterial medical textile fabrics by coating the textile with ZnO or CuO nanoparticles. Computational models on acoustic propagation are developed in order to aid the design procedures. The acoustic pressure wave propagation in the sonoreactor is simulated by solving the Helmholtz equation using a meshless numerical method. The paper implements both the state-of-the-art linear model and a nonlinear wave propagation model recently introduced by Louisnard (2012), and presents a novel iterative solution procedure for the nonlinear propagation model which can be implemented using any numerical method and/or programming tool. Comparative results regarding both the linear and the nonlinear wave propagation are shown. Effects of bubble size distribution and bubble volume fraction on the acoustic wave propagation are discussed in detail. The simulations demonstrate that the nonlinear model successfully captures the realistic spatial distribution of the cavitation zones and the associated acoustic pressure amplitudes. 相似文献
19.
《Ultrasonics sonochemistry》2014,21(1):154-161
Unsteady numerical computations are performed to investigate the flow field, wave propagation and the structure of bubbles in sonochemical reactors. The turbulent flow field is simulated using a two-equation Reynolds-Averaged Navier–Stokes (RANS) model. The distribution of the acoustic pressure is solved based on the Helmholtz equation using a finite volume method (FVM). The radial dynamics of a single bubble are considered by applying the Keller–Miksis equation to consider the compressibility of the liquid to the first order of acoustical Mach number. To investigate the structure of bubbles, a one-way coupling Euler–Lagrange approach is used to simulate the bulk medium and the bubbles as the dispersed phase. Drag, gravity, buoyancy, added mass, volume change and first Bjerknes forces are considered and their orders of magnitude are compared. To verify the implemented numerical algorithms, results for one- and two-dimensional simplified test cases are compared with analytical solutions. The results show good agreement with experimental results for the relationship between the acoustic pressure amplitude and the volume fraction of the bubbles. The two-dimensional axi-symmetric results are in good agreement with experimentally observed structure of bubbles close to sonotrode. 相似文献
20.
R.O. Fox 《Journal of computational physics》2009,228(20):7771-7791
Kinetic equations containing terms for spatial transport, body forces, and particle–particle collisions occur in many applications (e.g., rarefied gases, dilute granular gases, fluid-particle flows). The direct numerical solution of the kinetic equation is usually intractable due to the large number of independent variables. A useful alternative is to reformulate the problem in terms of the moments of the velocity distribution function. Closure of the moment equations is challenging for flows sufficiently far away from the Maxwellian limit. In previous work, a quadrature-based third-order moment closure was derived for approximating solutions to the kinetic equation for arbitrary Knudsen number. A key component of quadrature-based closures is the moment-inversion algorithm used to find the non-negative weights and velocity abscissas. Here, a robust inversion procedure is proposed for three-component velocity moments up to ninth order. By reconstructing the velocity distribution function, the spatial fluxes in the moment equations are treated using a kinetic-based finite-volume solver. Because the quadrature-based moment method employs the moment transport equations directly instead of a discretized form of the kinetic equation, the mass, momentum and energy are conserved for arbitrary Knudsen and Mach numbers. The computational algorithm is tested for the Riemann shock problem and, for increasing Knudsen numbers (i.e. larger deviations from the Maxwellian limit), the accuracy of the moment closure is shown to be determined by the discrete representation of the spatial fluxes. 相似文献