共查询到20条相似文献,搜索用时 156 毫秒
1.
2.
分析了滑移线延长线与楔面交点附近的流动特点,研究了准定常强激波反射中马赫杆的变形,建立了马赫杆突出变形消失的过渡准则,并用激波极曲线方法进行了求解。对马赫杆的变形过程进行了描述,研究了比热比、马赫数的变化对马赫杆突出变形消失条件的影响,并对突出变形消失区域与终点双马赫反射区域进行了比较。结果表明:马赫杆突出变形的消失是低比热比介质中出现的一种激波反射现象。马赫杆突出变形的消失,导致出现一种新的无射流、直马赫杆的双马赫反射结构。 相似文献
3.
基于三波理论和Whitham方法对带隔板装药爆轰波相互作用后发生的正规反射和非正规反射进行了理论分析,给出了爆轰波发生马赫反射时临界入射角和马赫杆增长角等参数的变化规律,提出了马赫杆高度的计算模型。基于凝聚炸药爆轰Jones-Wilkins-Lee(JWL)模型和冲击起爆的Lee-Tarver模型,利用有限元计算软件对带隔板装药爆轰波的传播过程进行了数值模拟。结果表明,发生马赫反射后,随着爆轰波的传播,马赫杆的高度不断增加。数值模拟结果与理论计算结果吻合较好,说明本文中采用的理论模型和数值模拟方法能够较准确地描述带隔板装药爆轰波马赫反射的传播过程。 相似文献
4.
采用一种两步化学反应模型对胞格爆轰波的楔面马赫反射过程进行了数值研究,从而澄清和解释胞格不稳定性对马赫反射发展模式和自相似性的影响。考虑到反应欧拉方程源项的刚性问题,本文采用附加RungeKutta方法耦合非刚性对流项和刚性反应源项,对流项的离散采用五阶精度的WENO格式。计算结果表明,对于稳定胞格爆轰波而言,其马赫反射过程本质上与ZND爆轰波的马赫反射是一致的,整体上不存在自相似性,胞格不稳定性只是造成了三波点轨迹线局部小振幅的波动。在楔面顶点附近,由于马赫杆是强过驱的,爆轰波的马赫反射过程是自相似的。在远场,爆轰波马赫反射的三波点轨迹线渐近的趋向于一条直线,说明重新获得了自相似性。对于不稳定的爆轰波,由于自身的不稳定性可以与马赫反射的强度相匹配,定义其三波点的轨迹是困难的,进行自相似性分析没有意义。 相似文献
5.
6.
7.
本文描述爆炸波的马赫反射的物理图象和过程,并且用几何方法来分析确定马赫反射的起点,进而确定地面上马赫反射峰值超压的近似计算公式,然后很容易地求得马赫波阵面上的其它一些参数。 相似文献
8.
9.
10.
激波在收缩管内的反射与聚焦会形成高温高压区,点燃可燃混合气并诱导爆轰,因此对爆轰发动机的点火具有重要意义。本文基于二维N-S方程,结合五阶WENO格式,对马赫数为6的正激波在三角形楔面内的反射与聚焦现象进行了数值研究。结果表明,楔面顶角的变化对激波的反射类型以及聚焦均有明显的影响:随着顶角的增加,激波的反射类型从马赫反射向过渡马赫反射和双马赫反射转变,且壁面上的前向射流更加明显;三波点第一次碰撞产生的高温高压区足够满足可燃混合气体的点火条件,且其温度与压力值随顶角的增加而增大;当激波在楔面上发生临界双马赫反射时,温度与压力达到最大;当顶角增加到一定值时,激波在楔面反射转变为常规反射,不会产生激波对碰,因而没有高温高压区。 相似文献
11.
A numerical simulation was performed for the process of formation of single Mach reflection on a wedge by solving a BGK type kinetic equation for the reduced distribution function with a finite difference scheme. The calculations were carried out for a shock Mach number 2.75 and wedge angle 25° in a monatomic gas, which corresponds to the conditions of single Mach reflection in the classical von Neumann theory. The calculations were performed for both diffuse and specular reflection of molecules at the wall surface. It is concluded that the diffuse reflection of molecules at the wall surface or the existence of the viscous or thermal layer is an essential factor for a nonstationary process at the initial stage of Mach reflection. Furthermore, the numerical results for diffuse reflection are found to simulate the experimental results very well, such as a transient process from regular reflection to Mach reflection along with shock propagation.This article was processed using Springer-Verlag TEX Shock Waves macro package 1990. 相似文献
12.
The internal flowfield including shock reflections structure inside a 2-D half inlet model was examined by a double exposure holographic interferometry using a Q-switched pulse laser. The interferograms give detailed flow visualization pictures. The structures of regular reflection, lambda reflection and Mach reflection in the inlet channel were observed. From the analysis of fringe patterns, the quantitative distributions of flow density, pressure and Mach number of the internal flowfield have been reconstructed. The boundary layer thickening and separation in the case of lambda reflection and the Mach stem in the case of Mach reflection were clearly demonstrated in the holographic fringe patterns. The results show that the shock interacitons with the ramp and the wall introduce a complicated flow structure which could strongly affect the efficiency of the inlet.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
13.
Shock waves impinging on axisymmetric converging passages of moderate wall angle undergo cyclical Mach reflection processes which are generally not self-similar during progression through the contraction. This paper presents the results of shock tube experiments in air where shocks of moderate strength are incident on cones having a range of wall angles of 10° to 30°. Mach reflection is maintained as the dominant reflection process throughout this range but the number of cycles decreases as wall angle increases. A ray-shock approach, used to calculate the triple-point trajectories gives good agreement with the experimental locations of their intersections with the centreline and wall. 相似文献
14.
气相爆轰波在障碍物上Mach反射的实验验证 总被引:3,自引:0,他引:3
本文公布了气相爆轰波沿收缩管道传播时发生Mach反射的实验证据。在爆轰波通过的管道中安装不同楔角的楔块,形成管道的收缩。爆轰波在通过楔块时会发生Mach反射。利用烟熏玻璃片记录到了爆轰波Mach反射时形成的三波点迹线及其两侧胞格尺寸和密度的变化。据我们掌握的资料,这是首次用胞格结构变化的记录证实,气相爆轰波与无化学反应的空气中的冲击波一样,在一定的入射条件下会发生Mach反射。这一实验结果可使我们更深入了解爆轰波的本质,也为数值模拟气相爆轰波在障碍物上Mach反射现象提供了可对比的依据。 相似文献
15.
The reflection of a triple-shock configuration was studied numerically in two dimensions using the Navier–Stokes equations. The flow field was initialized using three shock theory, and the reflection of the triple point on a plane of symmetry was studied. The conditions simulated a stoichiometric methane-oxygen detonation cell at low pressure on time scales preceding ignition when the gas was assumed to be inert. Viscosity was found to play an important role on some shock reflection mechanisms believed to accelerate reaction rates in detonations when time scales are small. A small wall jet was present in the double Mach reflection and increased in size with Reynolds number, eventually forming a small vortex. Kelvin–Helmholtz instabilities were absent, and there was no Mach stem bifurcation at Reynolds numbers corresponding to when the Mach stem had travelled distances on the scale of the induction length. Kelvin–Helmholtz instabilities are found to not likely be a source of rapid reactions in detonations at time scales commensurate with the ignition delay behind the Mach stem. 相似文献
16.
可燃气体中激波聚焦的点火特性 总被引:4,自引:0,他引:4
数值模拟了二维平面激波从抛物面上反射在可燃气体中聚焦的过程,研究了形
成爆轰波的点火特性. 对理想化学当量比氢气/空气混合气体,在初始压强20kPa的条件下,
马赫数2.6-2.8的激波聚焦能产生两个点火区:第1个点火区是反射激波会聚引起的,第
2个点火区是由入射激波在抛物面上发生马赫反射引起的. 这种条件下流场中会出现爆燃转
爆轰,起爆点分别分布在管道壁面、抛物反射面和第2点火区附近. 起爆机理分别为激波管
道壁面反射、点火诱导激波的抛物面反射和点火诱导的激波与第2点火区产生的爆燃波的相
互作用. 不同的点火和起爆过程导致了不同的流场波系结构,同时影响了爆轰波传播的波动
力学过程. 相似文献
17.
Shock structure in separated nozzle flows 总被引:2,自引:1,他引:1
In the case of high overexpansion, the exhaust jet of the supersonic nozzle of rocket engines separates from nozzle wall because
of the large adverse pressure gradient. Correspondingly, to match the pressure of the separated flow region, an oblique shock
is generated which evolves through the supersonic jet starting approximately at the separation point. This shock reflects
on the nozzle axis with a Mach reflection. Thus, a peculiar Mach reflection takes place whose features depend on the upstream
flow conditions, which are usually not uniform. The expected features of Mach reflection may become much difficult to predict,
depending on the nozzle shape and the position of the separation point along the divergent section of the nozzle.
相似文献
18.
Beric W. Skews 《Shock Waves》2005,14(3):137-146
The two-dimensional diffraction of a shock wave over a wall made up of a series of plane and/or curved sections is considered.
The analysis is based on the theory presented by, for the interaction of an originally plane shock wave with a corner. A method
is presented by which the shock profile may be determined for a wall of any shape and for any incident Mach number, in regions
where the characteristics form a simple wave. Comparisons are made between experimental measurements and theoretical predictions
for convex walls consisting of a number of facets, and for circular arcs, for a range of incident shock wave Mach numbers.
It is shown that the theory gives a satisfactory prediction of the wave shape, which improves as the Mach number increases.
Modifications in the flow field behind the shock, compared to that for a simple corner made up of two plane walls is discussed,
particularly relating to flow separation. For circular arc concave walls a inverse Mach reflection results experimentally,
leading to regular reflection, for which the theory is of no use.
PACS 47.40.Nm 相似文献
19.
It has been shown that when a plane shock wave is reflected off a surface consisting of a 75-mm radius circular arc followed
by a plane section inclined at 45°, it takes some time for the interaction to reach a pseudosteady reflection configuration.
The current study extends this work at a constant Mach number of 1.346, with three compound walls, consisting of leading circular
sections of 30, 50 and 75 mm radius, joined to a plane wall section. Testing was done at various wall angles for each of the
test pieces. The reflected wave angle was measured and was found to increase along the plane wall section until it reached
an asymptotic value, at which time pseudosteady flow was established. The asymptotic values are consistent with reflection
off plane wedges and are independent of the leading radius. For lower wall angles which lead to Mach reflection the length
required to reach pseudosteady flow increases as the wall angle increases to the pseudosteady transition angle. The reverse
occurs when the final pseudosteady reflection is regular, in that as the wall angle increases the distance travelled to reach
pseudosteady flow conditions decreases. Additional tests were conducted on a specimen consisting of a plane section at 60°
wall angle with 30-mm radius circular arc sections at either end. It is demonstrated how the information from the two slope
changes influences the shape of the reflected shock. The trajectories of two perturbations on the reflected shock arising
from the joints between the circular sections and the plane wall show that the reflected wave remains linear between these
two points, as it received no knowledge from either circular section until the perturbations from the upper and lower joints
cross. 相似文献
20.
徐立功 《应用数学和力学(英文版)》1989,10(6):545-552
The influence of a nontotal reflection on the interaction of a reflected shock wave with the boundary layer in a reflected shock tunnel has been investigated. The calculating method of the velocity, the temperature and the Mach number profiles in the boundary layer in reflected shock fixed coordinates has been obtained. To account for equilibrium real gas effects of nitrogen, the numerical results show that the minimum Mach number in the boundary layer has been moved from the wall into the boundary layer with the increasing of the incident shock Mach number. The minimum Mach number, the shock angle in the bifurcated foot and the jet velocity along the wall to the end plate are reduced owing to the increasing of the area of nozzle throat. The numerical results are in good agreement with measurements. 相似文献