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1.
Transition between regular and Mach reflection of shock waves: new numerical and experimental results 总被引:1,自引:0,他引:1
M.S. Ivanov D. Vandromme V.M. Fomin A.N. Kudryavtsev A. Hadjadj D.V. Khotyanovsky 《Shock Waves》2001,11(3):199-207
New numerical and experimental results on the transition between regular and Mach reflections of steady shock waves are presented.
The influence of flow three-dimensionality on transition between steady regular and Mach reflection has been studied in detail
both numerically and experimentally. Characteristic features of 3D shock wave configuration, such as peripheral Mach reflection,
non-monotonous Mach stem variation in transverse direction, the existence of combined Mach-regular-peripheral Mach shock wave
configuration, have been found in the numerical simulations. The application of laser sheet imaging technique in streamwise
direction allowed us to confirm all the details of shock wave configuration in the experiments. Close agreement of the numerical
and experimental data on Mach stem heights is shown.
Received 23 November 2000 / Accepted 25 April 2001 相似文献
2.
Numerical investigation of shock wave reflections near the head ends of rotating detonation engines 总被引:5,自引:0,他引:5
The influence of various chamber geometries on shock wave reflections near the head end of rotating detonation engines was investigated. A hydrogen/air one-step chemical reaction model was used. The results demonstrated that the variation in flow field along the radial direction was not obvious when the chamber width was small, but became progressively more obvious as the chamber width increased. The thrust increased linearly, and the detonation height and the fuel-based gross specific impulse were almost constant as the chamber width increased. Near the head end, shock waves reflected repeatedly between the inner and outer walls. Both regular and Mach reflections were found near the head end. The length of the Mach stem increased as the chamber length increased. When the chamber width, chamber length and injection parameters were the same, the larger inner radius resulted in more shock wave reflections between the inner and outer walls. The greater the ratio of the chamber width to the inner radius, the weaker the shock wave reflection near the head end. The detonation height on the outer wall and the thrust, both increased correspondingly, while the specific impulse was almost constant as the inner radius of the chamber increased. The numerical shock wave reflection phenomena coincided qualitatively with the experimental results. 相似文献
3.
In this paper, the “FLIC” difference method with triangular mesh is adopted to numerically simulate the regular and Mach reflections
that occur when a shock wave pass around a wedge. The compuational result is compared with the shock tube experimental results
of G. Ben-Dor and I. I. Glass. The comparison shows that the position, shape of shock wave and height of Mach stem all show
a good agreement. Consequently, the “FLIC” difference method with triangular mesh is quite satisfactory in numerical simulation
of the regular and Mach reflections. 相似文献
4.
5.
The pattern of shock wave reflection over a wedge is, in general, either a regular reflection or a Mach reflection, depending
on wedge angles, shock wave Mach numbers, and specific heat ratios of gases. However, regular and Mach reflections can coexist,
in particular, over a three-dimensional wedge surface, whose inclination angles locally vary normal to the direction of shock
propagation. This paper reports a result of diffuse double exposure holographic interferometric observations of shock wave
reflections over a skewed wedge surface placed in a 100 × 180 mm shock tube. The wedge consists of a straight generating line
whose local inclination angle varies continuously from 30° to 60°. Painting its surface with fluorescent spray paint and irradiating
its surface with a collimated object beam at a time interval of a few microseconds, we succeeded in visualizing three-dimensional
shock reflection over the skewed wedge surface. Experiments were performed at shock Mach numbers, 1.55, 2.02, and 2.53 in
air. From reconstructed holographic images, we estimated critical transition angles at these shock wave Mach numbers and found
that these were very close to those over straight wedges. This is attributable to the flow three-dimensionality.
相似文献
6.
The effects of energy deposition in the free stream on steady regular and Mach shock wave reflections are studied numerically. A short-duration laser pulse is focused upstream of the incident shock waves. It causes formation of the expanding blast wave and the residual hot-spot interacting in a complex way with the steady shock wave reflection. It was found that the laser energy addition in the free stream may force the transition from regular to Mach reflection in the dual solution domain. In contrast to previously reported numerical results, the transition from Mach to regular reflection has not been reproduced in our refined computations since the Mach reflection is restored after the flow perturbation. 相似文献
7.
Numerical simulations have been performed to investigate the stability of shock wave reflection in supersonic steady flow.
Wall deflection control has been applied just downstream of the reflection point in the regular reflection configuration.
The results provide the magnitude of the disturbance required to cause transition from one configuration to the other throughout
the range of incident shock angle. An argument focusing on the subsonic region generated behind the Mach stem in the Mach
reflection configuration explains the mechanism of the transition. Numerical results show that both regular and Mach reflections
are possible in the dual-solution domain, and also indicate the presence of the hysteresis effect. The transition processes
and the stability of the possible states are shown to be described consistently by an analogy based on the potential energy
of a particle on a surface. The necessity of more sophisticated experimental investigations is emphasized to verify the argument
about the stability of shock reflections and proposed analogy.
Received 17 March 1997 / Accepted 26 February 1998 相似文献
8.
This study employs the Space-Time Conservation Element and Solution Element (CE/SE) method to determine the influence of downstream
flow conditions on Mach stem height. The results indicate that the Mach stem height depends on the incident shock wave angle
and the distance between the trailing edge and the symmetry plane. Furthermore, it is shown that the downstream length ratio
and the trailing edge angle do not affect the Mach stem height nor the Mach reflection (MR) configuration, and the Space-Time
Conservation Element and Solution Element method is able to simulate the MR as well as many other numerical schemes.
Communicated by K. Takayama
PACS 47.40.Nm 相似文献
9.
Akira Sakurai
L. F. Henderson
Kazuyoshi Takayama
Zbigniew Walenta
Philip Colella
《Fluid Dynamics Research》1989,4(5-6):333-345Recent experimental and numerical studies of weak Mach reflections are examined. It is shown that the fundamental reason for the von Neumann paradox is that his theory of Mach reflection is based on the assumption that the flow downstream of the reflected wave and the Mach shock near the wave triple point is uniform. The assumption is shown to be valid for strong Mach reflection which agrees with experiment, but invalid for weak Mach reflection which does not agree with experiment. It is also shown that viscous effects are dominant when the incident shock is within about 100 mean free path lengths of the corner, but not otherwise. The analytical theory of the entire subsonic region supports these conclusions. 相似文献
10.
The three-dimensional (3D) shock wave reflections over two perpendicularly intersecting wedges are numerically studied in
this paper, using the finite volume method which is based on the MUSCL-Hancock interpolation technique and self-adaptive unstructured
mesh. Two kinds of 3D Mach stem structures are demonstrated by the numerical simulations for different shock Mach numbers
and wedge angles. A four-shock or three-shock wave configuration appears in the vicinity of the corner of the wedges. 相似文献
11.
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
12.
Classification of various types of the reflections of a shock wave over a straight wedge is proposed. The idea about entire reflection phenomenon as a result of interaction of two processes—the shock wave reflection process and the flow deflection process—serves as a basis for the classification. To recognize the types of reflection, changes in the shapes of the reflected wave, Mach stem, and contact surface (slipstream) are taken into account. The boundaries and domains of existence for various types of reflection configuration are reported. New terms for some types of reflection are proposed. The domain of irregular non-Mach reflection is analyzed carefully. It is shown that the von Neumann reflection pattern can result from not only the weak shock reflection but also the strong shock reflection over thin wedges. Shadowgraph images of different types of irregular reflection that illustrate the suggested classification are presented. Emphasis is placed on near-wall behavior of the contact discontinuity in the Mach configuration. 相似文献
13.
Highly complicated shock wave dynamics has been numerically calculated by solving the Euler equations for a circular shock
tube suddenly expanded three times of the original tube diameter atx=0. Shock waves of different shock Mach number,M
s
=1.5 and 2.0, have produced remarkably distinct blast jet structures. A planar shock wave took its final form after the blast
by repeated Mach reflections of the blast wave: the first one at the wall and the second one at the central axis. The central
Mach disc overtook and merged with the annular Mach stem before the planar shock wave was formed. In contrast to the blast
wave which would propagate spherically in an open space, the present blast wave undergoes complex morphological transformation
in the restricted flow passage, resulting in an unstable and oscillatory blast jet structure of highly rotational nature.
The slipstream tube emanating from the shock tube exit corner decomposed into a chain of small vortex rings that interacted
with the barrel shock of the jet, which caused periodic collapse of the jet structure. The finite volume-FCT formulation equipped
with the time-dependenth-refinement adaptive unstructured triangular mesh technique in the present paper has contributed to resolution of the intricate
physical discontinuities developing in the blast flow fields. 相似文献
14.
The objective of this study is to understand the flow structures of weak and strong spherical blast waves either propagating
in a free field or interacting with a flat plate. A 5th-order weighted essentially non-oscillatory scheme with a 4th-order
Runge-Kutta method is employed to solve the compressible Euler/Navier-Stokes equations in a finite volume approach. The real-gas
effects are taken into account when high temperature occurs. A shock-tube problem with the real-gas effect is first tested
in order to verify the solver accuracy. Moreover, unsteady shock waves moving over a stationary wedge with various wedge angles,
resulting in different types of shock wave reflections, are also tested. It is found that the computed results agreed well
with the existing data. Second, the propagation of a weak spherical blast wave, created by rupture of a high-pressure isothermal
sphere, in a free field is studied. It is found that there are three minor shock waves moving behind the main shock. Third,
the problem of a strong blast wave interacting with a flat plate is investigated. The flow structures associated with single
and double Mach reflections are reported in detail. It is found that there are at least three local high-pressure regions
near the flat plate.
Received 27 July 2000 / Accepted 25 January 2002 – Published online 17 June 2002 相似文献
15.
An experimental study shows that the Guderley reflection (GR) of shock waves can be produced in a standard shock tube. A new
technique was utilised which comprises triple point of a developed weak Mach reflection undergoing a number of reflections
off the ceiling and floor of the shock tube before arriving at the test section. Both simple perturbation sources and diverging
ramps were used to generate a transverse wave in the tube which then becomes the weak reflected wave of the reflection pattern.
Tests were conducted for three ramp angles (10°, 15°, and 20°) and two perturbation sources for a range of Mach numbers (1.10–1.40)
and two shock tube expansion chamber lengths (2.0 and 4.0 m). It was found that the length of the Mach stem of the reflection
pattern is the overall vertical distance traveled by the triple point. Images with equivalent Mach stem lengths in the order
of 2.0 m were produced. All tests showed evidence of the fourth wave of the GR, namely the expansion wave behind the reflected
shock wave. A shocklet terminating the expansion wave was also identified in a few cases mainly for incident wave Mach numbers
of approximately 1.20. 相似文献
16.
Many theoretical studies have shown the existence of a hysteresis effect in the solution of oblique shock reflections. In
fact, a wide domain of free-stream Mach number and shock angle values exists where regular reflection and Mach reflection
are both possible solutions for the same flow conditions. Part of this domain overlaps the typical operating conditions of
supersonic air intakes, and therefore it is of practical interest to obtain a deeper understanding of the theoretical problem.
Indeed, although both solutions are theoretically possible, they yield very different flowfields and consequently large discrepancies
in the evaluation of the air intake performance. Numerical solutions for steady configurations have been carried out and compared
with the flow evolution obtained for time-dependent cases. The results have confirmed numerically the existence of the multiple
solution domain where hysteresis takes place in time-dependent simulations. The analysis of the physical and numerical problems
encountered has provided indications for a correct simulation in practical applications.
Received 10 August 1999 / Accepted 6 October 2000 相似文献
17.
This paper presents an experimental and numerical investigation of three-dimensional shock wave reflections over a corner
of two wedges intersecting perpendicularly in a shock tube. Experiments were conducted in a diaphragmless shock tube equipped with double-exposure diffuse holographic interferometry in which the time interval between
the first and second exposure was set to be . This arrangement clearly visualized complex configurations of three-dimensional shock wave reflections. A numerical study
was also carried out for interpreting these holographic interferometric observations by using the Weighted Average Flux (WAF)
method to solve the three-dimensional unsteady compressible Euler equations. It was found that along the line of the intersection
of these two wedges, two Mach stems intersected each other resulting in the formation of a Mach stem which leaned forward.
Received 30 June 1996 / Accepted 6 October 1996 相似文献
18.
We have developed a computational code based on the axisymmetric Navier–Stokes equations with thermochemical kinetics for assessing wave drag reduction and other effects in pulse-energy deposition ahead of a bow shock by means of full simulations from generation of a laser-induced blast wave to interaction with the bow shock. Thermochemical nonequilibrium computations can reproduce the process of blast wave formation with laser ray tracing, and the computed low-density core inside the blast wave has a teardrop-like shape, depending on the laser input condition. The flowfield interacting with a bow shock formed in Mach 5 flow was computed. The result suggests that the shape of the low-density core affects the resultant wave drag, and parameters of an incident laser beam should be taken into account in exploring the optimal condition of the proposed wave-drag scheme. 相似文献
19.
Abstract. This paper reports on the characteristics of a compact vertical diaphragmless shock tube, which was constructed and tested
in the Shock Wave Research Center to study experimentally the behavior of toroidal shock waves. It is 1.15 m in height and
has a self-sustained co-axial vertical structure consisting of a 100 mm i.d. outer tube and an 80 mm o.d. inner tube. To create
a ring shaped shock wave between the inner and outer tubes, a rubber sheet is inserted to separate a high pressure driver
gas from a test gas, which is bulged with auxiliary high pressure helium from the behind. When the rubber membrane is contracted
by the sudden release of the auxiliary gas so as to break the seal, shock waves are formed. Special design features of the
shock tube are described and their role in producing repeatable shock waves is discussed. Its special opening characteristics
make possible the production of annular shaped shock waves that are unlikely met with a conventional tube that uses rupturing
diaphragms. Performance of the shock tube is evaluated in terms of the shock wave Mach numbers and the measured flow properties.
It eventually showed a higher degree of repeatability and the scatter in the shock wave Mach numbers Ms was found to be 0.2%
for Ms ranging from 1.1 to 1.8. The shock wave Mach number so far measured agreed very well with the simple shock tube theory.
Received 3 February 1999 / Accepted 6 April 2000 相似文献
20.
空腔流动存在剪切层运动、涡脱落与破裂,以及激波与激波、激波与剪切层、激波与膨胀波和激波/涡/剪切层相互干扰等现象,流动非常复杂,特别是高马赫数(M>2)时,剪切层和激波更强,激波与激波干扰更严重,对数值格式的要求更高,既需要格式耗散小,对分离涡等有很高的模拟精度,又需要格式在激波附近具有较大的耗散,可以很好地捕捉激波,防止非物理解的出现。Roe和HLLC等近似Riemann解格式在高马赫数强激波处可能会出现红玉现象,而HLLE++格式大大改善了这种缺陷,在捕捉高超声速激波时避免了红玉现象的发生,同时还保持在光滑区域的低数值耗散特性。本文在结构网格下HLLE++格式的基础上,通过改进激波探测的求解,建立了基于非结构混合网格的HLLE++计算方法,通过无粘斜坡算例,验证了HLLE++格式模拟高马赫数流动的能力,并应用于高马赫数空腔流动的数值模拟,开展了网格和湍流模型影响研究,验证了方法模拟高马赫数空腔流动的可靠性和有效性。 相似文献