多爆源云雾爆炸波相互作用的三维数值研究

从三维全N S方程出发,用二阶迎风TVD格式,针对贴地和近地三种不同的爆源位置,研究了两团云雾爆炸后爆炸场的相互作用。计算结果表明:本文的方法可模拟多爆源爆炸后冲击波的传播和爆炸场复杂的波系结构。压力分布可确定爆炸场任意位置的压力时间变化历程。     

双燃式超燃发动机冷态内流场的数值研究

研究了双燃式一体化通道(包含进气道、双燃式燃烧室和尾喷管)的冷态内流场特性.首次在激波风洞中对内流场进行纹影照相,用TVD格式求解三维全N-S方程对喷管和一体化通道进行分区数值模拟,并考察了几何参数对内流场的影响.结果表明对典型工况(h     

TVD自相容流体力学拉氏格式研究

流体力学数值模拟格式总体上可分为Eulerian(欧氏)、Lagrangian(拉氏)和ALE(Arbitrary LagrangianEulerian),TVD广泛应用于Eulerian格式。本文利用具有TVD保持性质的Runge-Kutta型时间离散方法,构造了流体力学Lagrangian(拉氏)自相容格式,应用von Neumann小扰动技术分析了该格式的稳定性,并进行了相应的数值模拟,较好地抑制了激波波后非物理振荡。     

超声速气流中雾化燃料喷射的三维数值研究

首次用双流体模型对雾化燃料在扩张形超燃室中沿九喷嘴顺流喷射的混合问题进行了数值研究。气相用迎风 TVD格式求解三维全 Navier- Stokes方程 ,液相用预估、校正 NND格式求解三维 Euler方程。相间相互作用的常微分方程用预估、校正Runge- Kutta法求解。用三维 Poisson方程生成网格。结果表明 :气相较液相的扩散效果好 ,小直径液滴的扩散效果好。相间速度滑移、改变气相喷射压力和喷射速度对液相扩散的贡献不大 ,但调整喷射角度会明显地增强液相的扩散、混合 ,本文结果未出现阻塞。     

二维洪水演进数值模拟

利用非结构化的有限体积方法,建立了二维浅水方程高精度、高分辨率模型。以Roe类型的近似Rie-mann解计算界面通量,通过MUSCL和两步TVD Runge-Kutta法获得了空间和时间都具有二级精度的TVD格式。采用特征分解的方法处理底坡源项和采用半隐式方法处理摩擦源项均能保证了格式的稳定性与和谐性。通过水滴算例对模型进行验证,并应用此模型对98年胖头泡分滞洪区分洪过程进行模拟,获得滞洪区不同时段的淹没范围和淹没水深,为防洪救灾提供了依据。     

高精度PPM格式在湍流燃烧中的应用

利用处理三维可压缩粘性流体流动问题中的沉浸边界法,并结合基于PPM方法的高精度TVD格式,对三维方形管道中部的圆柱火焰绕流及惰性气体绕流问题进行了数值模拟。计算湍流时采用大涡模拟(LES),化学反应速率采用EBU漩涡破碎模型。通过计算结果与实验结果的比较,发现高精度PPM格式能精确模拟两类圆柱绕流问题。计算中还发现,火焰圆柱绕流算例中,在火焰翻越圆柱前,由于燃烧的膨胀作用,使得火焰正面前的未燃气体流动并形成惰性气体绕流,这与无燃烧时的惰性气体绕流类似。但当火焰翻越圆柱过程中及完全翻越圆柱后,两种算例绕流流场出现明显变化。     

非理想爆源产生的爆炸场数值模拟

本文采用有限差分方法TVD(Total Variation Diminishing,A. Harten,1983)格式对非理想爆源在地面上形成的二维轴对称爆炸场进行了数值模拟,数值计算值与试验结果吻合得相当好。     

A CLASS OF COMPACT UPWIND TVD DIFFERENCE SCHEMES

A new method was proposed for constructing total variation diminishing (TVD) upwind schemes in conservation forms. Two limiters were used to prevent non-physical oscillations across discontinuity. Both limiters can ensure the nonlinear compact schemes TVD property. Two compact TVD (CTVD) schemes were tested, one is third-order accuracy, and the other is fifth-order. The performance of the numerical algorithms was assessed by one-dimensional complex waves and Riemann problems, as well as a two-dimensional shock-vortex interaction and a shock-boundary flow interaction. Numerical results show their high-order accuracy and high resolution, and low oscillations across discontinuities.     

非理想爆源产生的爆炸场数值模拟

本文采用有限差分方法——TVD(Total Variation Diminishing,A. Harten,1983)格式对非理想爆源在地面上形成的二维轴对称爆炸场进行了数值模拟,数值计算值与试验结果吻合得相当好。     

数值研究激波与旋涡的相互作用

从非定常形式的Euler方程出发,数值模拟了运动激波与旋涡相互作用的非定常流动过程。为保证激波具有较高的分辨率,采用对称型TVD格式进行了数值计算。结果表明。这样可以有效地模拟流场中一些复杂的流动现象,如激波变形、激波分叉和三波点的形成,以及旋涡结构的变化过程等,并与已有的实验流动显示相符良好。同时,也是对TVD格式求解这类问题的一次初步尝试。     

A dimension split method for the incompressible Navier–Stokes equations in three dimensions

In this paper, we describe a new method for the three‐dimensional steady incompressible Navier–Stokes equations, which is called the dimension split method (DSM). The basic idea of DSM is that the three‐dimensional space is split up into a cluster of two‐dimensional manifolds and then the three‐dimensional solution is approximated by the solutions on these two‐dimensional manifolds. Through introducing some technologies, such as SUPG stabilization, multigrid method, and such, we firstly make DSM feasible in the computation of real flow. Because of split property of DSM, all computation is carried out on these two‐dimensional manifolds, namely, a series of two‐dimensional problems only need to be solved in the computation of three‐dimensional problem, which greatly reduces the difficulty and the computational cost in the mesh generation. Moreover, these two‐dimensional problems can be computed simultaneously and a coarse‐grained parallel algorithm would be constructed, whereas the two‐dimensional manifold is considered as the computation unit. In the last, we explore the behavior and the accuracy of the proposed method in two numerical examples. Firstly, error estimates, performance of multigrid method, and parallel algorithm are well‐demonstrated by the known analytical solution case. Secondly, the computations of three‐dimensional lid‐driven cavity flows with different Reynolds numbers are compared with other numerical simulations. Results show that the present implementation is able to exhibit good stability and accuracy properties for real flows. Copyright © 2013 John Wiley & Sons, Ltd.     

压电材料三维问题的虚边界元——最小二乘配点法

从压电材料三维问题的基本方程出发,利用已有的压电材料三维问题的基本解以及弹性力学虚边界元方法的基本思想和线性叠加原理,提出了压电材料三维问题的虚边界元——最小二乘配点解法。虚边界元解法继承了传统边界元方法的优点,并且有效避免了传统边界元方法中可能遇到的边界积分奇异性问题。最后,文章给出了压电材料三维问题的几个数值算例,并且与解析解做了比较,结果表明本文的方法具有较高的精度,是解决该问题一个十分有效的数值求解方法。     

高速碰撞的三维欧拉数值模拟方法

介绍一种可用于高速碰撞问题数值模拟的三维弹塑性流体动力学数值计算方法,以及应用该方法研制的应用软件ＭＥＰＨ３Ｄ,并给出了一些高速碰撞问题的数值计算结果,计算结果表明该程序具有计算三维高速碰撞问题的能力。     

三维复杂流动的间断有限元方法模拟

本文基于三维可压缩Euler方程,采用基于Runge-Kutta时间离散的间断有限元方法(RKDG方法),对三维前台阶、三维Riemann问题和球Riemann等问题进行了模拟。结果表明,本文的RKDG方法能够在很少的网格内清晰地捕捉到三维复杂流场中的激波和接触间断;同时,将球Riemann问题中z=0.4平面压强沿到对称轴距离的分布与文献中的近似精确解相比,吻合较好,这也验证了本文的RKDG方法不仅能够进行三维复杂流场的定性描述,也能够应用于三维复杂流场的定量计算。     

Computational study of the axial instability of rimming flow using Arnoldi method

Axial instability of rimming flow has been investigated by solving a linear generalized eigenvalue problem that governs the evolution of perturbations of two‐dimensional base flow. Using the Galerkin finite element method, full Navier–Stokes equations were solved to calculate base flow and this base flow was perturbed with three‐dimensional disturbances. The generalized eigenproblem formulated from these equations was solved by the implicitly restarted Arnoldi method using shift‐invert technique. This study presents instability curves to identify the critical wavelength of the neutral mode and the critical β, which measures the importance of gravity relative to viscosity. The axial instability of rimming flow is examined and three‐dimensional flow was reconstructed by using eigenvector and growth rate at a critical wave number. The critical β value in the axial instability analysis was observed to be comparable to the onset β value of the transition between the bump and the homogeneous film state in 2‐D base flow calculations. Copyright © 2006 John Wiley & Sons, Ltd.     

边坡三维极限平衡法的通用形式

基于以下假定条件:(1) 稳定系数定义为材料的强度折减系数;(2) 土体为刚体,底滑面服从Mohr-Columb强度破坏准则;(3) 微条柱底部法向力dNz的作用点处于条柱底部中点;(4)滑面剪力与底滑面和xoz平面交线的夹角为θ。本文建立了边坡三维极限平衡法的通用形式,通过给定不同的限制条件,可分别得到三维普通条分法 、三维简化毕肖普法 、三维简化简布法 、三维Spencer法 等三维极限平衡的具体算法。     

球形厚壳的应力分析

文中将球形厚壳视为三维弹性体，按三维弹性理论问题求解其应力及位移。     

列车与结构动态耦合分析的并行计算方法

在分析结构动态响应时考虑列车与结构的动态耦合作用,采用详细三维有限元模型会带来计算量太大的问题。本文采用并行计算方法,根据列车与结构动态耦合模型的计算特点,设计实现了列车结构耦合均衡的分区算法,并以两个工程应用为例,利用该方法对列车结构三维数值模型进行分区计算,结果表明该分区方法比递归坐标二分法有更好的并行效率。     

A three-dimensional transient two-phase flow analysis with a density pertubation finite volume method

In this paper, we present the analysis of a full three dimensional transient two-phase flow with strong disequilibria. This analysis uses a finite volume scheme with a recently developed density perturbation method. The application test case is a three dimensional extension of a one-dimensional experiment on blowdown pipe. The results are stable with mesh refinements and show realistic three-dimensional effects.     

Fundamental validation of the finite volume particle method for 3D sloshing dynamics

The use of the finite volume particle (FVP) method is validated for three‐dimensional sloshing dynamics with a free surface by comparing with results from experiments. In the first part, two typical sloshing experiments for a single liquid phase are simulated, and slosh characteristics that include the free surface behavior and hydrodynamic pressure are reported. Moreover, the influences of the circular wall geometry and spatial resolution in the simulation are studied in a sensitivity analysis. In the second part, two sloshing problems with solid bodies are simulated to preliminarily verify the applicability of the FVP method to three‐dimensional solid bodies' motion in liquid flow. Good agreement between simulations and corresponding experiments indicates that the present FVP method well reproduces three‐dimensional sloshing behavior. Copyright © 2010 John Wiley & Sons, Ltd.