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1.
基于ALE方法的3D充填流动模拟   总被引:1,自引:1,他引:0       下载免费PDF全文
基于任意拉格朗日-欧拉方法发展了三维充填流动的数值模拟方案.该方案采用ALE方法准确地追踪移动自由面的位置并避免了网格扭曲;基于移动最小二乘曲面拟合方法提出了移动自由面上网格节点重定位方法,将充填流动的网格更新过程简化为自由面附近的局部网格重划分过程,并通过分级多面体三角剖分实现,减小了网格划分的计算量,实现了实时网格生成.给出的数值算例结果表明了该数值模型对三维充填流动模拟的有效性.  相似文献   

2.
中国空气动力研究与发展中心超高速所即将建成的高焓喷胀管采用自由活塞驱动,为了能够使该设备有效运行试验时间达到最长,需要对设备中的压缩管长度进行优化。针对压缩管中的自由活塞运动,本文通过数值求解单一组分和混合驱动气体条件下的活塞运动准一维常微分控制方程组,分析了不同试验设计参数和不同驱动气体介质对压缩管定压驱动时间的影响。采用数值解结合脊线(局部极值曲线)理论获得了定压驱动时间局部极值曲面,基于压缩管四种摩尔比例驱动气体(100%H2,85%H2+15%N2,100%He,85%He+15%Ar)和三组压缩比(λ=60,100,140)下的极值曲面,研究发现,定压驱动时间脊线高度随着压缩管的有效长度(初始活塞头部到压缩管末端膜片的距离)和内径之比L/D增加而增加。本文研究最终获得了给定参数条件下满足最长定压驱动时间要求的最佳压缩管长度。  相似文献   

3.
高超声速激波风洞研究进展   总被引:3,自引:0,他引:3  
姜宗林  俞鸿儒 《力学进展》2009,39(6):766-776
回顾了高超声速激波风洞的研制与发展, 并依据高超声速实验研究对地面实验模拟技术的要求, 分别介绍了应用轻气体、自由活塞和爆轰驱动技术研制的主要激波风洞的性能、特点和存在问题. 重点介绍了爆轰驱动高焓激波风洞的3种主要运行模式: 反向、正向爆轰驱动与双爆轰驱动. 根据这些运行模式的工作原理, 分析了应用这些驱动技术产生的高温、高压气源的特点, 探讨了不同驱动技术可能影响激波风洞性能的关键问题与解决方法. 目前发展的激波风洞已经能够用于开展马赫数 3$\sim$30的高超声速流动的试验模拟研究, 但是试验气流的品质还不能满足高超声速科技研究的需求. 为了获得可靠的实验结果, 通过不断改进、完善、提高激波风洞的性能, 尽可能复现高超声速飞行条件是今后主要的研究方向.  相似文献   

4.
徐立功 《力学进展》1992,22(3):324-331
自由活塞激波风洞是一种使用自由活塞压缩器驱动的高焓脉冲型激波风洞。这种风洞是由R J Stalker提出并在澳大利亚国立大学首先建成和逐渐发展起来的高焓实验设备。经过30多年的改进与发展,日趋完善,现已成为研究高超声速气动加热、计及真实气体效应的气体动力学现象、特别是超声速或高超声速燃氢冲压发动机(scamjet)的重要设备之一,受到国际上航空航天界的重视。本文概述了自由活塞激波风洞的发展过程,系统地阐述了这种设备的结构特点和运行原理,给出了性能参数的计算方法和算例,及其性能指标,并讨论了这类风洞的优缺点。  相似文献   

5.
为了预测氢氧定容燃烧驱动的高温激波管性能,需要准确分析激波管非定常化学非平衡流动过程.本文在破膜前的驱动段定容燃烧以及破膜后的化学非平衡流动数值模拟中,引入双时间步长方法,发展高温激波管化学非平衡流动数值模拟方法,该方法在时间上具有二阶精度.计算结果与目前存在的激波管流动解析解以及零维化学反应系统的数值解进行了比较,吻合较好.对于典型高温激波管状态,采用有限体积方法离散准一维流动Euler控制方程,并通过将流动过程和化学反应动力学过程耦合求解,获得了激波管内部的化学非平衡流动特征.  相似文献   

6.
用于ALE有限元模拟的网格更新方法   总被引:1,自引:0,他引:1  
周宏  李俊峰  王天舒 《力学学报》2008,40(2):267-272
任意拉格朗日欧拉法(ALE)可以通过定义参考网格的运动,实现自由液面跟 踪,完成液体晃动的数值计算. 综合用于更新网格节点的3种基本计算方法,将多方 向更新网格速度的技术应用于任意拉格朗日欧拉网格节点的速度计算. 给出了水平圆柱形贮 箱和椭圆形贮箱内液体晃动算例,实现了多方向更新网格运动与晃动流场计算的耦合,使ALE 方法能胜任复杂几何边界下的自由液面流动的数值模拟.  相似文献   

7.
针对高超声速飞行伴随的热化学反应流动,本文回顾了郭永怀先生的科研理念和学科布局,综述了他亲手成立的高温气动团队在高超声速飞行风洞实验模拟理论与方法方面的研究进展.高温气体的迅速产生与迅速应用是一种理想的风洞运行方法,而激波管就是这样一种实验装备.论文首先介绍了激波管技术的基本理论与方程,指出将其用于高超声速流动实验模拟时所具有的独特优势.然后讨论了应用激波风洞复现需要的高超声速飞行状态的可行性、基本方程和需要解决的关键问题.针对这些关键问题,进一步介绍了如何应用爆轰现象研发激波风洞驱动技术的理论,并给出了基于爆轰驱动方法的技术发展和工程应用验证.最后,论文介绍了爆轰驱动激波风洞的界面匹配条件,该条件奠定了长实验时间激波风洞运行基础,是其他驱动方法尝试解决而没能完全解决的难题.高温气动团队关于高超声速飞行复现风洞的理论与技术研究,实现了郭永怀先生的战略规划,成就了国际领先的高超声速热化学反应流动研究平台.   相似文献   

8.
针对高超声速飞行伴随的热化学反应流动,本文回顾了郭永怀先生的科研理念和学科布局,综述了他亲手成立的高温气动团队在高超声速飞行风洞实验模拟理论与方法方面的研究进展.高温气体的迅速产生与迅速应用是一种理想的风洞运行方法,而激波管就是这样一种实验装备.论文首先介绍了激波管技术的基本理论与方程,指出将其用于高超声速流动实验模拟时所具有的独特优势.然后讨论了应用激波风洞复现需要的高超声速飞行状态的可行性、基本方程和需要解决的关键问题.针对这些关键问题,进一步介绍了如何应用爆轰现象研发激波风洞驱动技术的理论,并给出了基于爆轰驱动方法的技术发展和工程应用验证.最后,论文介绍了爆轰驱动激波风洞的界面匹配条件,该条件奠定了长实验时间激波风洞运行基础,是其他驱动方法尝试解决而没能完全解决的难题.高温气动团队关于高超声速飞行复现风洞的理论与技术研究,实现了郭永怀先生的战略规划,成就了国际领先的高超声速热化学反应流动研究平台.  相似文献   

9.
正向爆轰驱动高焓激波风洞的数值模拟   总被引:5,自引:1,他引:4  
对充满氢氧可燃气体、带扩容腔的正向爆轰驱动的激波风洞进行了数值模拟。计算采用了欧拉方程,频散可控耗散差分格式(DCD)和改进的二阶段化学反应模型。在扩容腔附近采用二维轴对称计算模型,而在驱动段和被驱动段的直管道部分则采用一维计算模型。本文分析了爆轰波在管道中的传播、反射和绕射过程。计算结果表明扩容腔的尺寸对爆轰波的传播、反射、汇聚等起着决定性的作用;带扩容腔的正向爆轰驱动的激波风洞能够得到平稳的持续时间较长的气流,提高了实验的精确度和可重复性。  相似文献   

10.
激波风洞高低压段钢膜片破裂特性研究   总被引:1,自引:0,他引:1  
激波风洞是用于高超声速飞行器气动外形设计和优化的常用地面试验装置,基于爆轰驱动技术,激波风洞能够在短时间(毫秒级)内产生高温、高压的驱动气体来模拟高超声速试验气流.主膜片位于激波风洞中的爆轰驱动段和激波管段之间,试验时膜片在爆轰脉冲压力下打开,膜片的打开状态和脱落情况对激波风洞气流品质有很大的影响. 同时,膜片也是形成激波的先决条件. 传统的风洞采用铝质膜片进行试验,在激波风洞中需要承压能力更强的膜片, 此时铝质膜片不再适用, 需要采用钢质膜片.因此, 对激波风洞中的钢膜片破裂特性进行研究很有必要.将数值计算结果与试验结果进行比较, 发现数值计算结果与试验结果吻合得比较理想,计算结果具有可靠性. 基于膜片的应力-应变模型, 建立了膜片打开的动力学模型,根据CJ爆轰理论, 采用有限元软件计算模拟了膜片破裂的过程,分析总结了膜片破裂的机制和力学特性规律.采用控制变量法对不同厚度和凹槽长度的膜片进行分析研究,得到了膜片破膜压力和有效破膜时间的变化规律. 在激波风洞试验中,根据膜片总破膜时间设计了适用于JF-12复现风洞的膜片参数.   相似文献   

11.
Accurate prediction of extrudate (die) swell in polymer melt extrusion is important as this helps in appropriate die design for profile extrusion applications. Extrudate swell prediction has shown significant difficulties due to two key reasons. The first is the appropriate representation of the constitutive behavior of the polymer melt. The second is regarding the simulation of the free surface, which requires special techniques in the traditionally used Eulerian framework. In this paper we propose a method for simulation of extrudate swell using an Arbitrary Lagrangian Eulerian (ALE) technique based finite element formulation. The ALE technique provides advantages of both Lagrangian and Eulerian frameworks by allowing the computational mesh to move in an arbitrary manner, independent of the material motion. In the present method, a fractional-step ALE technique is employed in which the Lagrangian phase of material motion and convection arising out of mesh motion are decoupled. In the first step, the relevant flow and constitutive equations are solved in Lagrangian framework. The simpler representation of polymer constitutive equations in a Lagrangian framework avoids the difficulties associated with convective terms thereby resulting in a robust numerical formulation besides allowing for natural evolution of the free surface with the flow. In the second step, mesh is moved in ALE mode and the associated convection of the variables due to relative motion of the mesh is performed using a Godunov type scheme. While the mesh is fixed in space in the die region, the nodal points of the mesh on the extrudate free surface are allowed to move normal to flow direction with special rules to facilitate the simulation of swell. A differential exponential Phan Thien Tanner (PTT) model is used to represent the constitutive behavior of the melt. Using this method we simulate extrudate swell in planar and axisymmetric extrusion with abrupt contraction ahead of the die exit. This geometry allows the extrudate to have significant memory for shorter die lengths and acts as a good test for swell predictions. We demonstrate that our predictions of extrudate swell match well with reported experimental and numerical simulations.  相似文献   

12.
We present an extended finite element method (XFEM) for the direct numerical simulation of the flow of viscoelastic fluids with suspended particles. For moving particle problems, we devise a temporary arbitrary Lagrangian–Eulerian (ALE) scheme which defines the mapping of field variables at previous time levels onto the computational mesh at the current time level. In this method, a regular mesh is used for the whole computational domain including both fluid and particles. A temporary ALE mesh is constructed separately and the computational mesh is kept unchanged throughout the whole computations. Particles are moving on a fixed Eulerian mesh without any need of re-meshing. For mesh refinements around the interface, we combine XFEM with the grid deformation method, in which nodal points are redistributed close to the interface while preserving the mesh topology. Our method is verified by comparing with the results of boundary fitted mesh problems combined with the conventional ALE scheme. The proposed method shows similar accuracy compared with boundary fitted mesh problems and superior accuracy compared with the fictitious domain method. If the grid deformation method is combined with XFEM, the required computational time is reduced significantly compared to uniform mesh refinements, while providing mesh convergent solutions. We apply the proposed method to the particle migration in rotating Couette flow of a Giesekus fluid. We investigate the effect of initial particle positions, the Weissenberg number, the mobility parameter of the Giesekus model and the particle size on the particle migration. We also show two-particle interactions in confined shear flow of a viscoelastic fluid. We find three different regimes of particle motions according to initial separations of particles.  相似文献   

13.
The flux reconstruction (FR) formulation can unify several popular discontinuous basis high-order methods for fluid dynamics, including the discontinuous Galerkin method, in a simple, efficient form. An arbitrary Lagrangian–Eulerian (ALE) extension to the high-order FR scheme is developed here for moving mesh fluid flow problems. The ALE Navier–Stokes equations are derived by introducing a grid velocity. The conservation law are spatially discretised on hybrid unstructured meshes using Huynh’s scheme (Huynh 2007) on anisotropic elements (quadrilaterals) and using Correction Procedure via Reconstruction scheme on isotropic elements (triangles). The temporal discretisation uses both explicit and implicit treatments. The mesh movement is described by node positions given as a time series, instead of an analytical formula. The geometric conservation law is tested using free stream preservation problem. An isentropic vortex propagation test case is performed to show the high-order accuracy of the developed method on both moving and fixed hybrid meshes. Flow around an oscillating cylinder shows the capability of the method to solve moving boundary viscous flow problems, with the numeric method further verified by comparison of the result on a smoothly deforming mesh and a rigid moving mesh.  相似文献   

14.
Improvement of a free piston driver for a high-enthalpy shock tunnel   总被引:1,自引:0,他引:1  
In order to improve the operation of a high-enthalpy free piston shock tunnel its tuned operation was studied analytically and experimentally. First, the piston motion in the free piston driver tube was analytically solved by proposing a simple piston/gasdynamic model, and the tuned operation condition was formulated as an eigenvalue with which the piston has sufficiently high speed at the moment of diaphragm rupture, so as to maintain a constant driver gas pressure, and reduces its speed to come to rest when very closely approaching the end of the driver tube. Second, the result of this analysis was validated by its comparison with experiments which were conducted in the medium-sized free piston shock tunnel HEK installed at the NAL Kakuda Research Center. By observing the detail of piston landing at the end of the driver tube the present tuned operation was found to be successfully achieved with the operating condition given here. Its advantages in improving the pressure recovery factor and in enhancing the stagnation enthalpy were successfully demonstrated. Received 8 June 1997 / Accepted 1 October 1997  相似文献   

15.
Multi-Material Arbitrary Lagrangian–Eulerian (ALE) finite element methods can solve large deformations in fast dynamic problems like explosions because the mesh motion can be independent of the material motion. However materials must flow between elements and this advection involves numerical dissipations. The rezoning mesh method presented in this paper was designed to reduce these numerical errors for shock wave propagation. The mesh moves to refine the elements near the shock front. This refinement limits the advection fluxes and so the numerical diffusion. This technique is applied to the numerical simulations of airblast problems for which a parameter controlling the mesh refinement is studied.  相似文献   

16.
In this paper, a fully discrete high‐resolution arbitrary Lagrangian–Eulerian (ALE) method is developed over untwisted time–space control volumes. In the framework of the finite volume method, 2D Euler equations are discretized over untwisted moving control volumes, and the resulting numerical flux is computed using the generalized Riemann problem solver. Then, the fluid flows between meshes at two successive time steps can be updated without a remapping process in the classic ALE method. This remapping‐free ALE method directly couples the mesh motion into a physical variable update to reflect the temporal evolution in the whole process. An untwisted moving mesh is generated in terms of the vorticity‐free part of the fluid velocity according to the Helmholtz theorem. Some typical numerical tests show the competitive performance of the current method. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

17.
The Lagrangian approach is usually used for the simulation of flow with strong shock waves. Moreover, this approach is particularly well suited to treatment of material interfaces in the case of multimaterial flows.Unfortunately, this formulation leads to very large deformations in the mesh. The arbitrary Lagrangian‐Eulerian method overcomes this drawback by using a mesh regularization that is based on an analysis of cell geometry. The regularization step may be considered as a method used to correct the nonconvex and potentially tangled cells that constitute the mesh. In this paper, we present a new approach to mesh regularization. Instead of using a purely geometric criterion, we propose that the mesh evolution is computed on the basis of the flow vorticity. This approach is called the large Eddy limitation method, and it is aimed here to be used in finite volume direct arbitrary Lagrangian‐Eulerian methods. The large Eddy limitation method is general, which means that it is not restricted to applications in the finite volume framework dedicated to fluid flow simulation; for instance, it could also be naturally applied to the finite element framework.  相似文献   

18.
Experimental investigation on tunnel sonic boom   总被引:1,自引:0,他引:1  
Upon the entrance of a high-speed train into a relatively long train tunnel, compression waves are generated in front of the train. These compression waves subsequently coalesce into a weak shock wave so that a unpleasant sonic boom is emitted from the tunnel exit. In order to investigate the generation of the weak shock wave in train tunnels and the emission of the resulting sonic boom from the train tunnel exit and to search for methods for the reduction of these sonic booms, a 1300 scaled train tunnel simulator was constructed and simulation experiments were carried out using this facility.In the train tunnel simulator, an 18 mm dia. and 200 mm long plastic piston moves along a 40 mm dia. and 25 m long test section with speed ranging from 60 to 100 m/s. The tunnel simulator was tilted 8° to the floor so that the attenuation of the piston speed was not more than 10 % of its entrance speed. Pressure measurements along the tunnel simulator and holographic interferometric optical flow visualization of weak shock waves in the tunnel simulator clearly showed that compression waves, with propagation, coalesced into a weak shock wave. Although, for reduction of the sonic boom in prototype train tunnels, the installation of a hood at the entrance of the tunnels was known to be useful for their suppression, this effect was confirmed in the present experiment and found to be effective particularly for low piston speeds. The installation of a partially perforated wall at the exit of the tunnel simulator was found to smear pressure gradients at the shock. This effect is significant for higher piston speeds. Throughout the series of train tunnel simulator experiments, the combination of both the entrance hood and the perforated wall significantly reduces shock overpressures for piston speeds ofu p ranging from 60 to 100 m/s. These experimental findings were then applied to a real train tunnel and good agreement was obtained between the tunnel simulator result and the real tunnel measurements.  相似文献   

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