共查询到20条相似文献,搜索用时 125 毫秒
1.
2.
3.
4.
三角翼涡破裂的高精度数值模拟 总被引:1,自引:0,他引:1
采用5阶精度的加权紧致非线性格式(WCNS-E-5)数值模拟65°后掠角尖前缘三角翼的大攻角跨声速绕流流场,考察低耗散、高分辨率的WCNS-E-5格式对于三角翼涡破裂模拟的适用性,及激波旋涡干扰对涡破裂点位置的影响,重点研究三角翼大攻角旋涡破裂点的突然前移.通过求解任意坐标系下的非定常雷诺平均N-S方程,采用WCNS-E-5和SST两方程湍流模型,与试验结果和文献计算结果对比,表明既有高阶精度又能光滑捕捉激波的WCNS格式在模拟三角翼旋涡破裂方面具有一定优势,其数值结果与试验结果吻合较好,三角翼大攻角旋涡破裂点的突然前移是由于跨声速流场的激波旋涡干扰. 相似文献
5.
本文提出了一个新的高阶Godunov格式。此格式放弃了[9]、[10]中关于参数在格子中满足多项式分布近似及在格子边界上存在间断的假设,直接引入了一个分段边界层型函数分布假设。由于引入的分布函数是单调可微的,因此PBLM格式无需进行如同MUSCL、PPM等格式中的单调性校核。该格式由于不进行单调性修正,在PPM格式中需进行修正而精度降阶的点上仍保持原有精度。对一维激波管的计算表明PBLM格式对激波的展开比PPM格式还要小,计算时间相当。同PPM格式一样,PBLM格式在激波后存在有2%~4%的皮后伪振荡,应加上适当的人工粘性。 相似文献
6.
在激波与气柱相互作用问题中,压力与密度间断不平行产生的斜压涡量会引起流动的不稳定性,从而促进物质间的混合.本文基于双通量模型,结合五阶加权基本无振荡(WENO)格式,求解多组分二维Navier-Stokes方程,分析激波作用面积相同结构不同的椭圆气柱所致的流动和混合.数值结果清晰地显示了激波诱导Richtmyer-Meshkov不稳定性引起的气柱界面变形和波系演化.同时定量地从界面运动、界面结构参数变化(长度和高度)、气柱体积压缩率、环量及混合率等角度分析激波诱导的流动混合机制,研究椭圆几何构型对氦气混合过程的影响.结果表明,界面及相关参数的演化与气柱初始形状密切相关.当激波沿椭圆长轴作用于气柱时,气柱前端出现空气射流结构,且射流不断增长并渗透到下游界面,致使气柱分离成两个独立涡团,离心率越大,射流发展越快;同时激波作用气柱后在界面处产生不规则反射现象.圆形气柱界面演化与这种作用情形类似.当激波沿椭圆短轴作用于气柱时,界面上游出现类平面结构,随后平面上下缘处产生涡旋,主导流动发展,激波在界面作用产生规则反射,离心率越大,这些现象越明显.界面高度、长度、体积压缩率也因此有所差异.对界面演化、环量和混合率的综合分析表明,激波沿长轴作用于气柱且离心率较大时,流动发展较快,不稳定性导致的流动越复杂,越有利于氦气与环境介质的混合. 相似文献
7.
基于大涡模拟, 结合五阶加权基本无振荡格式与沉浸边界法对激波自左向右与R22重气柱作用过程进行了数值模拟. 数值结果清晰地显示了激波诱导Richtmyer-Meshkov不稳定性所导致的重气柱变形过程, 并与Haas 和 Sturtevant 的实验结果符合. 另外, 结果还揭示了入射激波在气柱内右侧边界发生聚焦并诱导射流的过程, 以及在Kelvin-Helmhotz 次不稳定性作用下两个主涡滑移层形成次级涡的过程, 并分析了气柱变形过程中与周围空气的混合机理. 最后, 通过改变反射距离对反射激波与不同变形阶段的气柱的再次作用过程进行了研究. 结果表明: 当激波反射距离较长时, 反射激波与充分变形后的气柱作用, 使其在流向方向上进一步被压缩; 而当激波反射距离较短时, 反射激波会在气柱内发生马赫反射, 两个三波点附近产生两个高压区, 当其传播至气柱左侧边界时对气柱边界造成冲击加速, 诱导两道向左传播的反向射流.
关键词:
Richtmyer-Meshkov不稳定性
R22重气柱
反射激波
射流 相似文献
8.
9.
对流扩散方程的指数型摄动差分法 总被引:7,自引:0,他引:7
改进了作者所提出的对流扩散方程四阶指数型摄动差分格式,并阐明其在高Reynolds数适应性和节省计算量方面的显著优点。指数型摄动差分法经改进后具有较为简便的形式,克服了其他紧致高阶格式不能使用于高Reynolds数问题的致命弱点。文中针对计算流体力学的基本困难,作一至三维流动模型方程和自然对流传热问题的精细计算,且以双精制算法检验格式的四阶精度,表明摄动差分法能在较粗的网格下给出相当准确的结果,十分显著地节省计算机时,并对"激波"和"边界层"等高Reynolds数效应有极高的分辨能力。 相似文献
10.
11.
可压缩混合层气动光学效应研究 总被引:5,自引:0,他引:5
建立具有普适性的流场光学传输效应计算方法,针对脉动流场的光学传输计算方法可以预测空间非均匀分布的脉动流场引起的光学传输效应.以高阶紧致差分格式求解三维可压缩滤波N-S方程,对可压缩混合层流动进行空间模式的大涡数值模拟,得到流动失稳转捩直至完全湍流的空间发展全过程,采用时间模式的直接数值模拟进行对比验证.分析流动不同阶段对光学传输效应的影响,初步讨论流场特性与光学传输效应之间的联系,计算结果表明,在转捩区域流场引起的成像畸变最为严重. 相似文献
12.
Based on multi-fluid volume fraction and piecewise parabolic method
(PPM), a multi-viscosity-fluid hydrodynamic code MVPPM
(Multi-Viscosity-Fluid Piecewise Parabolic Method) is developed and
applied to the problems of shock-induced hydrodynamic interfacial
instability and mixing. Simulations of gas/liquid interface
instability show that the influences of initial perturbations on the
fluid mixing zone (FMZ) growth are significant, especially at the
late stages, while grids have only a slight effect on the FMZ width,
when the interface is impulsively accelerated by a shock wave
passing through it. A numerical study of the hydrodynamic
interfacial instability and mixing of gaseous flows impacted by
re-shocks is presented. It reveals that the numerical results are in
good agreement with the experimental results and the mixing growth
rate strongly depends on initial conditions. Ultimately, the jelly
layer experiment relevant to the instability impacted by exploding
is simulated. The shape of jelly interface, position of front face
of jelly layer, crest and trough of perturbation versus time are
given; their simulated results are in good agreement with
experimental results. 相似文献
13.
Formation of transverse waves in oblique detonations 总被引:1,自引:0,他引:1
Jimmy Verreault Andrew J. Higgins Robert A. Stowe 《Proceedings of the Combustion Institute》2013,34(2):1913-1920
The structure of oblique detonation waves stabilized on a hypersonic wedge in mixtures characterized by a large activation energy is investigated via steady method of characteristics (MoC) calculations and unsteady computational flowfield simulations. The steady MoC solutions show that, after the transition from shock-induced combustion to an overdriven oblique detonation, the shock and reaction complex exhibit a spatial oscillation. The degree of overdrive required to suppress this oscillation was found to be nearly equal to the overdrive required to force a one-dimensional piston-driven detonation to be stable, demonstrating the equivalence of two-dimensional steady oblique detonations and one-dimensional unsteady detonations. Full unsteady computational simulations of the flowfield using an adaptive refinement scheme showed that these spatial oscillations are transient in nature, evolving in time into transverse waves on the leading shock front. The formation of left-running transverse waves (facing upstream) precedes the formation of right-running transverse waves (facing downstream). Both sets of waves are convected downstream away from the wedge in the supersonic flow behind the leading oblique front, such that the mechanism of instability must continuously generate new transverse waves from an initially uniform flow. Together, these waves define a cellular structure that is qualitatively similar to a normal propagating detonation. 相似文献
14.
为了研究弹头激波诱导燃烧,基于有限体积的考虑化学反应的Navier-Stokes(N-S)方程,对预混氢气-空气化学恰当比时的燃烧流场进行了数值模拟.时间项基于2阶隐式LU-SGS格式,对流项基于Steger-Warming进行离散,化学反应源项采用对角化隐式处理.首先,研究了网格对燃烧爆轰流场结构的影响,并利用Lehr实验结果验证了计算方法的可靠性;其次,研究了弹头的飞行Mach数(Ma=4.18,5.11,6.46)、弹头直径(D=5,10,15 mm)对燃烧流场稳定性的影响.研究表明:计算网格对氢气-空气爆轰流场结构影响很大;弹头直径一定时,氢气-空气燃烧流场稳定性随着飞行Mach数的增大而增强;弹头飞行Mach数一定时,氢气-空气燃烧流场稳定性随着弹头直径减小而增强. 相似文献
15.
Susanne Kränkl 《Physics letters. [Part B]》2011,703(4):519-523
Renormalization of composite three-quark operators in dimensional regularization is complicated by the mixing of physical and unphysical (evanescent) operators. This mixing must be taken into account in a consistent subtraction scheme. In this work we propose a particular scheme that allows one to avoid the necessity of additional finite renormalization and is convenient in QCD applications. As an illustration, we calculate the two-loop anomalous dimensions of local three-quark operators in this scheme. 相似文献
16.
Simulation of shock-induced instability using an essentially conservative adaptive CE/SE method
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An essentially conservative adaptive space time conservation element and solution element(CE/SE)method is proposed for the effective simulation of shock-induced instability with low computational cost.Its implementation is based on redefined conservation elements(CEs)and solution elements(SEs),optimized interpolations and a Courant number insensitive CE/SE scheme.This approach is used in two applications,the Woodward double Mach reflection and a twocomponent Richtmyer–Meshkov instability experiment.This scheme reveals the essential features of the investigated cases,captures small unstable structures,and yields a solution that is consistent with the results from experiments or other high order methods. 相似文献
17.
B. V. Perepelitsa 《Thermophysics and Aeromechanics》2010,17(4):559-563
Results of visual studies of the flow structure of the air jet in a channel with corrugated wall are presented. The studies
have been carried out in the laminar and turbulent flows. The typical large-scale structures and zones of intensive turbulent
mixing have been determined in the flow. The general scheme of the flow is suggested. 相似文献
18.
预混火焰界面的RM(Richtmyer-Meshkov)不稳定现象在自然界和工程实践中十分常见,但目前关于反应性RM不稳定的研究主要集中于均匀介质的情况,而实际中的预混气体往往是非均匀的,因此开展非均匀介质中火焰界面演化和混合特性的研究十分必要。采用带单步化学反应的Navier-Stokes方程和高精度数值格式,研究了预混火焰界面在入射激波及反射激波作用下的RM不稳定过程,考察了化学反应活性以及介质非均匀性对RM不稳定过程中火焰界面混合特性的变化规律的影响。结果表明,在入射激波作用后的阶段,在均匀介质中的火焰界面形态呈现典型的"钉-帽-泡"结构,化学反应活性越强,界面的"泡"结构和"钉-帽"结构增长越快;而在非均匀介质中,火焰界面形态则呈现"钉-钉"结构,界面在流向速度差的诱导下被更大程度地拉伸。在第一次反射激波作用后的阶段,混合区的增长速率不依赖于反应活性和均匀性,仅与流动特性有关。时间尺度的研究表明,大尺度流动是反应性RM不稳定的主导因素,其次是化学反应,最后是小尺度混合,化学反应的强化会抑制大尺度流动,非均匀性会强化大尺度流动。 相似文献
19.
We study the fingering instability induced by a shock that propagates across a perturbed interface that separates two types of discrete particles. If collisions between particles conserve energy, then the relative sizes and growth rates of the fingers are similar to those in the analogous shock-induced fingering instability in fluids. However, we show that energy loss during particle collisions, even when very small, causes the qualitative features of the finger growth to be completely opposite to the fluid case. The fingers formed by light particles grow faster and become longer and narrower than the fingers formed by heavy particles. In addition, the finger composed of light particles collapses into an extremely compact, tortuous filament, and diffusive mixing between particle types at the particle scale is heavily suppressed. 相似文献
20.
Experiments are presented on pattern formation in the Belousov-Zhabotinsky (BZ) reaction in a blinking vortex flow. Mixing in this flow is chaotic, with nearby tracers separating exponentially with time. The patterns that form in this flow with the BZ reaction mimic chaotic mixing structures seen in passive transport. The behavior is analyzed in terms of a mixing time taum and a characteristic decorrelation time TBZ for the BZ system. Flows with taum comparable to or smaller than TBZ generate large-scale patterns whose features are captured by simulations of mixing fields for the flow. 相似文献