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浸入边界—晶格波尔兹曼法在流固耦合等复杂的流体系统中得到广泛的应用.本文采用基于速度源修正的浸入边界—晶格玻尔兹曼法,建立了仿生微流体驱动模型,创新性地将波动弹性体的速度引入晶格玻尔兹曼方程,避免了传统浸入边界—晶格玻尔兹曼法中浸入边界速度-结构变形-力之间的转换,提高了计算效率和准确率.研究了行波波动细丝对流场内流动速度和压力的影响,重点分析了驱动模型各项参数对微流体的驱动效果.研究结果表明:细丝长度、频率、振幅的增加引起出口处流量的增加;波长、流体粘滞系数以及细丝位置与出口处流量呈复杂的非线性关系. 相似文献
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针对流固耦合问题,发展了基于浸入边界-多松弛时间格子玻尔兹曼通量求解法(immersed boundary method multi-relaxation-time lattice Boltzmann flux solver,IB-MRT-LBFS)的弱耦合算法.依据多尺度Chapman-Enskog展开,建立不可压宏观方程状态变量和通量与格子玻尔兹曼方程中粒子密度分布函数之间的关系;采用强制浸入边界法处理流固界面使固壁表面满足无滑移边界条件,根据修正的速度求解动量方程力源项;结构运动方程采用四阶龙格-库塔法求解.格子模型与浸入边界法的引入使流固耦合计算可以在笛卡尔网格下进行,无需生成贴体网格及运用动网格技术,简化了计算过程.数值模拟了单圆柱横向涡激振动、单圆柱及串列双圆柱双自由度涡激振动问题.结果表明,IB-MRT-LBFS能够准确预测圆柱涡激振动的锁定区间、振动响应、受力情况以及捕捉尾流场结构形态,验证了该算法在求解流固耦合问题的有效性和可行性. 相似文献
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《物理学报》2017,(4)
提出了一种径向基函数虚拟网格法浸入边界法以模拟复杂或多体浸入边界黏性绕流问题.在该方法中,采用有限差分法离散固定笛卡尔交错网格上的不可压缩Navier-Stokes方程,以分步法结合三阶Runge-Kutta格式进行时间积分,高阶TVDMUSCL(total variation diminishing monotonic upstream-centered scheme forconservation laws)格式离散对流项;一个边界连续的虚拟网格法施加物面边界条件以考虑尖锐边界对流场的影响;引入具多项式基的径向基函数描述和重构任意复杂浸入界面,并识别背景网格属性状态.采用Fortran90语言开发相应的求解器,模拟了绕圆柱、机翼和交错布置圆柱群的黏性绕流问题,验证了本文方法的正确性、可靠性和对复杂边界流动问题的适用性. 相似文献
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Ghost Fluid方法与双介质可压缩流动计算 总被引:1,自引:1,他引:0
应用带有Isobaric修正的GhostFluid方法配合LevelSet方法计算可压缩双介质无粘流动.该方法可以消除计算流体界面时所产生的数值跳动和耗散,且编程上比界面跟踪法简单.应用WENO格式数值求解欧拉方程和LevelSet方程,对由刚性气体状态方程所支配的一二维双介质流动进行数值计算,得到了分辨率较高的计算结果. 相似文献
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波的传播往往在复杂的地质结构中进行,如何有效地求解非均匀介质中的波动方程一直是研究的热点.本文将局部间断Galekin(local discontinuous Galerkin, LDG)方法引入到数值求解波动方程中.首先引入辅助变量,将二阶波动方程写成一阶偏微分方程组,然后对相应的线性化波动方程和伴随方程构造间断Galerkin格式;为了保证离散格式满足能量守恒,在单元边界上选取广义交替数值通量,理论证明该方法满足能量守恒性.在时间离散上,采用指数积分因子方法,为了提高计算效率,应用Krylov子空间方法近似指数矩阵与向量的乘积.数值实验中给出了带有精确解的算例,验证了LDG方法的数值精度和能量守恒性;此外,也考虑了非均匀介质和复杂计算区域的计算,结果表明LDG方法适合模拟具有复杂结构和多尺度结构介质中的传播. 相似文献
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将镜像法与保角变换法相结合,求解复杂形状边界的二维边值问题,得出电场分布规律,并通过Matlab数据处理软件的数值计算功能进行数值模拟,绘制出其电场线与等势线(面)分布图,验证了所得结论的正确性.此方法拓展了镜像法的应用范围,为求解边界形状复杂的二维静电场的边值问题提供了一种新的思路和途径. 相似文献
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Yih-Ferng Peng Rajat Mittal Amalendu Sau Robert R. Hwang 《Journal of computational physics》2010,229(19):7072-7101
In this work, the local grid refinement procedure is focused by using a nested Cartesian grid formulation. The method is developed for simulating unsteady viscous incompressible flows with complex immersed boundaries. A finite-volume formulation based on globally second-order accurate central-difference schemes is adopted here in conjunction with a two-step fractional-step procedure. The key aspects that needed to be considered in developing such a nested grid solver are proper imposition of interface conditions on the nested-block boundaries, and accurate discretization of the governing equations in cells that are with block-interface as a control-surface. The interpolation procedure adopted in the study allows systematic development of a discretization scheme that preserves global second-order spatial accuracy of the underlying solver, and as a result high efficiency/accuracy nested grid discretization method is developed. Herein the proposed nested grid method has been widely tested through effective simulation of four different classes of unsteady incompressible viscous flows, thereby demonstrating its performance in the solution of various complex flow–structure interactions. The numerical examples include a lid-driven cavity flow and Pearson vortex problems, flow past a circular cylinder symmetrically installed in a channel, flow past an elliptic cylinder at an angle of attack, and flow past two tandem circular cylinders of unequal diameters. For the numerical simulations of flows past bluff bodies an immersed boundary (IB) method has been implemented in which the solid object is represented by a distributed body force in the Navier–Stokes equations. The main advantages of the implemented immersed boundary method are that the simulations could be performed on a regular Cartesian grid and applied to multiple nested-block (Cartesian) structured grids without any difficulty. Through the numerical experiments the strength of the solver in effectively/accurately simulating various complex flows past different forms of immersed boundaries is extensively demonstrated, in which the nested Cartesian grid method was suitably combined together with the fractional-step algorithm to speed up the solution procedure. 相似文献
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A dispersion-relation-preserving dual-compact scheme developed in Cartesian grids is applied together with the immersed boundary method to solve the flow equations in irregular and time-varying domains. The artificial momentum forcing term applied at certain points in cells containing fluid and solid allows an imposition of velocity condition to account for the motion of solid body. We develop in this study a differential-based interpolation scheme which can be easily extended to three-dimensional simulation. The results simulated from the proposed immersed boundary method agree well with other numerical and experimental results for the chosen benchmark problems. The accuracy and fidelity of the IB flow solver developed to predict flows with irregular boundaries are therefore demonstrated. 相似文献
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A High-Order Immersed Boundary Method for Acoustic Wave Scattering and Low-Mach Number Flow-Induced Sound in Complex Geometries 总被引:1,自引:0,他引:1
A new sharp-interface immersed boundary method based approach for the computation of low-Mach number flow-induced sound around complex geometries is described. The underlying approach is based on a hydrodynamic/acoustic splitting technique where the incompressible flow is first computed using a second-order accurate immersed boundary solver. This is followed by the computation of sound using the linearized perturbed compressible equations (LPCE). The primary contribution of the current work is the development of a versatile, high-order accurate immersed boundary method for solving the LPCE in complex domains. This new method applies the boundary condition on the immersed boundary to a high-order by combining the ghost-cell approach with a weighted least-squares error method based on a high-order approximating polynomial. The method is validated for canonical acoustic wave scattering and flow-induced noise problems. Applications of this technique to relatively complex cases of practical interest are also presented. 相似文献
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《Physics letters. A》2006,354(3):173-182
A momentum exchange-based immersed boundary-lattice Boltzmann method is presented in this Letter for simulating incompressible viscous flows. This method combines the good features of the lattice Boltzmann method (LBM) and the immersed boundary method (IBM) by using two unrelated computational meshes, an Eulerian mesh for the flow domain and a Lagrangian mesh for the solid boundaries in the flow. In this method, the non-slip boundary condition is enforced by introducing a forcing term into the lattice Boltzmann equation (LBE). Unlike the conventional IBM using the penalty method with a user-defined parameter or the direct forcing scheme based on the Navier–Stokes (NS) equations, the forcing term is simply calculated by the momentum exchange of the boundary particle density distribution functions, which are interpolated by the Lagrangian polynomials from the underlying Eulerian mesh. Numerical examples show that the present method can provide very accurate numerical results. 相似文献
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A method for reducing the spurious pressure oscillations observed when simulating moving boundary flow problems with sharp-interface immersed boundary methods (IBMs) is proposed. By first identifying the primary cause of these oscillations to be the violation of the geometric conservation law near the immersed boundary, we adopt a cut-cell based approach to strictly enforce geometric conservation. In order to limit the complexity associated with the cut-cell method, the cut-cell based discretization is limited only to the pressure Poisson and velocity correction equations in the fractional-step method and the small-cell problem tackled by introducing a virtual cell-merging technique. The method is shown to retain all the desirable properties of the original finite-difference based IBM while at the same time, reducing pressure oscillations for moving boundaries by roughly an order of magnitude. 相似文献
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Pilhwa Lee Boyce E. Griffith Charles S. Peskin 《Journal of computational physics》2010,229(13):5208-5227
We describe an immersed boundary method for problems of fluid–solute-structure interaction. The numerical scheme employs linearly implicit timestepping, allowing for the stable use of timesteps that are substantially larger than those permitted by an explicit method, and local mesh refinement, making it feasible to resolve the steep gradients associated with the space charge layers as well as the chemical potential, which is used in our formulation to control the permeability of the membrane to the (possibly charged) solute. Low Reynolds number fluid dynamics are described by the time-dependent incompressible Stokes equations, which are solved by a cell-centered approximate projection method. The dynamics of the chemical species are governed by the advection–electrodiffusion equations, and our semi-implicit treatment of these equations results in a linear system which we solve by GMRES preconditioned via a fast adaptive composite-grid (FAC) solver. Numerical examples demonstrate the capabilities of this methodology, as well as its convergence properties. 相似文献
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An adaptive version of ghost-cell immersed boundary method for incompressible flows with complex stationary and moving boundaries 总被引:1,自引:0,他引:1
WANG Liang & WU ChuiJie School of Science PLA University of Science Technology Nanjing China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian School of Aeronautics Astronautics 《中国科学:物理学 力学 天文学(英文版)》2010,(5)
An adaptive version of immersed boundary method for simulating flows with complex stationary and moving boundaries is presented.The method employs a ghost-cell methodology which allows for a sharp representation of the immersed boundary.To simplify the implementation of the methodology,a volume-of-fluid method is introduced to identify the immersed boundary.In addition,the domain is spatially discretized using a tree-based discretization which is relatively simple to implement a fully flexible adaptive refi... 相似文献
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A local domain-free discretization-immersed boundary method (DFD-IBM)
is presented in this paper to solve incompressible Navier-Stokes equations
in the primitive variable form. Like the conventional immersed boundary method
(IBM), the local DFD-IBM solves the governing equations in the whole domain including
exterior and interior of the immersed object. The effect of immersed boundary
to the surrounding fluids is through the evaluation of velocity at interior and
exterior dependent points. To be specific, the velocity at interior dependent points
is computed by approximate forms of solution and the velocity at exterior dependent
points is set to the wall velocity. As compared to the conventional IBM, the
present approach accurately implements the non-slip boundary condition. As a result,
there is no flow penetration, which is often appeared in the conventional IBM
results. The present approach is validated by its application to simulate incompressible
viscous flows around a circular cylinder. The obtained numerical results
agree very well with the data in the literature. 相似文献
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<正>In this paper,based on the improved complex variable moving least-square(ICVMLS) approximation,a new complex variable meshless method(CVMM) for two-dimensional(2D) transient heat conduction problems is presented. The variational method is employed to obtain the discrete equations,and the essential boundary conditions are imposed by the penalty method.As the transient heat conduction problems are related to time,the Crank-Nicolson difference scheme for two-point boundary value problems is selected for the time discretization.Then the corresponding formulae of the CVMM for 2D heat conduction problems are obtained.In order to demonstrate the applicability of the proposed method,numerical examples are given to show the high convergence rate,good accuracy,and high efficiency of the CVMM presented in this paper. 相似文献
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Jiannong Fang Marc DieboldChad Higgins Marc B. Parlange 《Journal of computational physics》2011,230(22):8179-8191
It is known that, when the immersed boundary method (IBM) is implemented within spectral-like methods, the Gibbs oscillation seriously deteriorates the calculation of derivatives near the body surface. In this paper, a radial basis function (RBF) based smoothing technique is proposed with the intention of eliminating or efficiently reducing the Gibbs oscillation without affecting the flow field outside the body. Based on this technique, a combined IBM/spectral scheme is developed to solve the incompressible Navier–Stokes equations. Numerical simulations of flow through a periodic lattice of cylinders of various cross sections are performed. The results demonstrate that the proposed methodology is able to give accurate and nearly oscillation-free numerical solutions of incompressible viscous flows. 相似文献