共查询到20条相似文献,搜索用时 15 毫秒
1.
Shock wave propagation in a branched duct 总被引:2,自引:0,他引:2
The propagation of a planar shock wave in a 90° branched duct is studied experimentally and numerically. It is shown that
the interaction of the transmitted shock wave with the branching segment results in a complex, two-dimensional unsteady flow.
Multiple shock wave reflections from the duct's walls cause weakening of transmitted waves and, at late times, an approach
to an equilibrium, one-dimensional flow. While at most places along the branched duct walls calculated pressures are lower
than that existing behind the original incident shock wave, at the branching segment's right corner, where a head on-collision
between the transmitted wave and the corner is experienced, pressures that are significantly higher than those existing behind
the original incident shock wave are encountered. The numerically evaluated pressures can be accepted with confidence, due
to the very good agreement found between experimental and numerical results with respect to the geometry of the complex wave
pattern observed inside the branched duct.
Received 15 July 1996 / Accepted 20 February 1997 相似文献
2.
A simple two-dimensional square cavity model is used to study shock attenuating effects of dust suspension in air. The GRP
scheme for compressible flows was extended to simulate the fluid dynamics of dilute dust suspensions, employing the conventional
two-phase approximation. A planar shock of constant intensity propagated in pure air over flat ground and diffracted into
a square cavity filled with a dusty quiescent suspension. Shock intensities were and , dust loading ratios were and , and particle diameters were and {\rm \mu}$m. It was found that the diffraction patterns in the cavity were decisively attenuated by the dust suspension, particularly
for the higher loading ratio. The particle size has a pronounced effect on the flow and wave pattern developed inside the
cavity. Wall pressure histories were recorded for each of the three cavity walls, showing a clear attenuating effect of the
dust suspension.
Received 15 November 1999 / Accepted 25 October 2000 相似文献
3.
Shock wave attenuation by grids and orifice plates 总被引:2,自引:0,他引:2
The interaction of weak shock waves with porous barriers of different geometries and porosities is examined. Installing a barrier inside the shock tube test section will cause the development of the following wave pattern upon a head-on collision between the incident shock wave and the barrier: a reflected shock from the barrier and a transmitted shock propagating towards the shock tube end wall. Once the transmitted shock wave reaches the end wall it is reflected back towards the barrier. This is the beginning of multiple reflections between the barrier and the end wall. This full cycle of shock reflections/interactions resulting from the incident shock wave collision with the barrier can be studied in a single shock tube test. A one-dimensional (1D), inviscid flow model was proposed for simulating the flow resulting from the initial collision of the incident shock wave with the barrier. Fairly good agreement is found between experimental findings and simulations based on a 1D flow model. Based on obtained numerical and experimental findings an optimal design procedure for shock wave attenuator is suggested. The suggested attenuator may ensure the safety of the shelter’s ventilation systems. 相似文献
4.
Shock wave attenuation in partially confined channels 总被引:2,自引:0,他引:2
An approximate analytical solution is presented for the attenuation of planar shock waves in channels with perforated walls. The problem is considered as quasi-one-dimensional. Good agreement is found between the theoretical results and available experimental data regarding the rate of shock wave attenuation within the range of initial shock Mach numbers between 1.1 and 4 and perforation ratios between 4.5 × 10–3 and 0.53. A correlation for the discharge coefficient of a single hole perforation is presented which gives quantitatively good agreement with particular experimental observations.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
5.
P. Kosinski 《Shock Waves》2006,15(1):13-20
The problem of wave propagation in a dust–air mixture inside a branched channel has not been studied widely in literature, even though this topic has many important applications especially in process safety (dust explosions). In this paper, a shock wave interaction with a cloud of solid particles, and the further behaviour of both gas and particulate phases were studied using numerical techniques. The geometry mimicked a real channel where bends or branches are common. Two numerical approaches were used: Eulerian–Eulerian and Eulerian–Lagrangian. Using Eulerian-Lagrangian simulation, it was possible to include the effects of particle–particle and particle–wall collisions in a realistic and direct manner. Results are mainly shown as snap-shots of particle positions during the simulations and statistics for the particle displacement. The results show that collisions significantly influence the process of particle cloud formation.
PACS47.40.Nm, 02.60.Cb, 47.55.kf 相似文献
6.
V.M. Boiko V.P. Kiselev S.P. Kiselev A.N. Papyrin S.V. Poplavsky V.M. Fomin 《Shock Waves》1997,7(5):275-285
The present paper is devoted to experimental and theoretical investigation of the shock wave (SW) propagation in a mixture
of gas and solid particles in the presence of explicit boundaries of the two-phase region (cloud of particles). The effect
of the qualitative change in the supersonic flow behind the SW in a cloud of particles within the range of the volume concentration
of the disperse phase 0.1-3% is experimentally shown and theoretically grounded.
Received 15 April 1996 / Accepted 3 June 1996 相似文献
7.
K.D. Joshi N. Suresh G. Jyoti S.K. Kulshreshtha S.C. Gupta S.K. Sikka 《Shock Waves》1998,8(3):173-176
Shock wave induced response of the berlinite form of FePO has been investigated up to 8.5 GPa. The X-ray diffraction measurements on the shock recovered samples reveal transition
to the mixture of an amorphous phase and an orthorhombic phase around 5 GPa. The proportion of the amorphous material in the
recovered sample is found to decrease at higher pressure. The results are interpreted in terms of a three-level free energy
diagram for the crystal to amorphous transitions.
Received 26 May 1997 / Accepted 1 September 1997 相似文献
8.
The propagation phenomenon of a detonation wave is particularly interesting, because the detonation wave is composed of a
3D shock wave system accompanied by a reaction front. Thus, the passage of a detonation wave draws cellular patterns on a
soot-covered plate. The pressure and temperature behind the detonation wave are extremely high and may cause serious damages
around the wave. Therefore, it is of great significance from a safety-engineering point of view to decay the detonation wave
with a short distance from the origin. In the present study, experiments using high-speed schlieren photography are conducted
in order to investigate the behaviors of the detonation wave diffracting from two slits. The detonation wave produced in a
stoichiometric mixture of hydrogen and oxygen is propagated through the slits, and the behaviors behind the slit-plate are
investigated experimentally. When a detonation wave diffracts from the slits, a shock wave is decoupled with a reaction front.
Since the two shock waves propagate from the slits interact with each other at the center behind the plate, the detonation
wave is reinitiated by generating a hot-spot sufficient to cause local explosions. Furthermore, it is clarified that the shock
wave reflected from a tube-wall is also capable of reinitiating the detonation wave. The reinitiation distance of the detonation
wave from the slit-plate is correlated using a number of cells emerged from each slit.
相似文献
9.
Saito T. Marumoto M. Yamashita H. Hosseini S.H.R. Nakagawa A. Hirano T. Takayama K. 《Shock Waves》2003,13(2):139-148
The attenuation of an underwater shock wave by a thin porous layer is studied both experimentally and numerically. The shock waves are generated by exploding 10 mg silver azide pellets and the pressures at different distances from the explosion center are measured. Measurements are also carried out with a gauze layer placed between the explosion source and the pressure gauge. The results with and without the gauze layer are compared evaluating the shock wave attenuation. Numerical simulations of the phenomenon are also carried out for a simple wave attenuation model. The results are compared with the experimental data. Despite the simple mathematical model of wave attenuation, the agreement between the experimental and numerical results is reasonable.Received: 22 October 2002, Accepted: 17 June 2003, Published online: 5 August 2003PACS:
47.11.+j, 47.40.Nm, 47.55.Mh 相似文献
10.
A. Chatterjee 《Shock Waves》1999,9(2):95-105
An initially planar shock wave can undergo significant distortion to its shape along with changes in its strength during
the period of its interaction with a compressible vortex. This phenomenon is studied by numerically simulating the shock wave-vortex
interaction with a high resolution shock-capturing scheme. Incident shock waves of various Mach numbers are made to interact
with a compressible vortex and the dependence of the shock wave distortion on the strength of the incident shock wave is studied
in detail. It is known that the type of complex shock structure formed in the later stages of a compressible vortex-shock
wave interaction is dependent on the Mach number of the incident shock wave. A simple physical model based on the principle
of shock wave reflection is proposed to explain this complex shock structure formation and its dependence on the relative
strengths of the interacting vortex and shock wave.
Received July 28, 1997 / Accepted November 17, 1997 相似文献
11.
The equations governing the head-on collision of a planar shock wave with a cellular material and a numerical scheme for solving the set of the governing equations were outlined. In addition, the condition for the transmitted compression waves to transform into a shock wave, inside the cellular material was introduced. It was proved analytically that a cellular material cannot be used as a means of reducing the pressure load acting on the end-wall of the shock tube. In subsequent papers, the interaction of planar shock waves with specific cellular materials, e.g., foams and honeycombs will be described in detail.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
12.
Ablation created by a Q-switched Nd:Yttrium Aluminum Garnet (Nd:YAG) laser beam focusing on a thin aluminum foil surface spontaneously
generates a shock wave that propagates through the foil and deforms it at a high speed. This high-speed foil deformation can
project dry micro- particles deposited on the anterior surface of the foil at high speeds such that the particles have sufficient
momentum to penetrate soft targets. We used this method of particle acceleration to develop a drug delivery device to deliver
DNA/drug coated microparticles into soft human-body targets for pharmaceutical applications. The device physics has been studied
by observing the process of particle acceleration using a high-speed video camera in a shadowgraph system. Though the initial
rate of foil deformation is over 5 km/s, the observed particle velocities are in the range of 900–400 m/s over a distance
of 1.5–10 mm from the launch pad. The device has been tested by delivering microparticles into liver tissues of experimental
rats and artificial soft human-body targets, modeled using gelatin. The penetration depths observed in the experimental targets
are quite encouraging to develop a future clinical therapeutic device for treatments such as gene therapy, treatment of cancer
and tumor cells, epidermal and mucosal immunizations etc.
相似文献
13.
The interaction between an air shock wave and a rigid wall covered by a porous screen is investigated numerically and experimentally. A mathematical two velocity with two stress tensors model is used for studying the wave processes in saturated porous media. The process of reflection of a step-type wave from a rigid wall covered with a porous layer is considered, the effect of the porous medium and wave parameters on the reflection is analyzed, and the numerical results are compared with the experimental data.Received: 30 July 2002, Accepted: 24 December 2002, Published online: 27 May 2003 相似文献
14.
In the Shock Wave Journal Vol. 2, No. 4 a benchmark test for shock wave reflection over wedges was announced. International
scientists who are interested in shock wave research were invited to participate. The benchmark test aimed at comparison of
various advanced numerical schemes as well as experimental results. During the last three years more than twenty results,
including both CFD and experiments, were collected from all over the world. Efforts contributed by these scientists made the
present benchmark test reach to a standard of the state of the art of the computational fluid dynamics applied to the shock
wave research. However, it was regrettable not to publish all the results collected due to limitation on the available page
number.
Received 5 November 1994 / Accepted 9 September 1996 相似文献
15.
Beric Skews 《Experiments in fluids》2005,39(5):875-884
Previous detailed studies of the interaction of a shock wave with a perforated sheet considered the impact of a shock wave
on a plate with regularly spaced slits giving area blockages of 60 and 67%, at various angles of incidence, and resulting
in both regular and Mach reflection. The current work extends this study to a much wider variety of plate geometries. Blockage
ratios of 20, 25, 33, 50, and 67 and inclinations of 45, 60, 75, and 90° to the shock wave were tested. Four different thicknesses
of plate were tested at the same frontal blockage in order to assess the effects of gap guidance. Tests were conducted at
two shock Mach numbers of 1.36 and 1.51 (inverse pressure ratios of 0.4 and 0.5). It is found that secondary reflected and
transmitted waves appear due to the complex interactions within the grid gaps, and that the vortex pattern which is generated
under the plate is also complex due to these interactions. The angle of the reflected shock, measured relative to the plate,
decreases with plate blockage and the angle of inflow to the plate reduces with increasing blockage. By analysing the flow
on the underside of the plate the pseudo-steady flow assumption is found to be a reasonable approximation. Both the pressure
difference and the stagnation pressure loss across the plate are evaluated. It is found that over the range tested the plate
thickness has a minimal effect. 相似文献
16.
An aircraft travelling at supersonic speeds close to the ground generates a bow wave which is reflected off the ground surface.
If a valley is traversed a complex reflection pattern will be generated. Similar patterns will evolve with a plane wave traversing
a depression on a surface or structure. To simulate the process a planar shock wave, generated in a shock tube, is moved over
several notched wedge configurations. Schlieren photographs were produced to assist in identifying the resulting complex three-dimensional
wave structures and then verified and extended by three- dimensional computations. The valley geometries investigated are
rectangular, triangular, parabolic and conical with a number of valley floor inclinations. The main features are extracted
in surface models to demonstrate the complexity of the flow, and in particular in the case where the reflection is regular
on the ground plane and Mach reflection in the valley.
相似文献
17.
The structure of the relaxation zone behind a shock wave of moderate strength in a mixture of gas, vapour and droplets is analysed. A model is presented for shock induced evaporation, which is based on wet-bulb equilibrium and on the absence of relative motion between droplets and gas. Experimental and numerical data on heterogeneous condensation induced by an unsteady rarefaction wave and on re-evaporation due to shock wave passage are reported for a mixture of water vapour, nitrogen gas and condensation nuclei. Pressure, temperature, saturation ratio and droplet size are experimentally obtained and are very well predicted by a numerical simulation based on the non-linear quasisteady wet-bulb model for phase transition, as well for the expansion wave as for the shock wave. During expansion, droplet number density decays much faster than predicted, which is not yet satisfactorily explained. Shock induced droplet evaporation is studied for post-shock saturation ratios ranging from 5×10–3 to 0.2, corresponding to shock Mach numbers of 1.2 to 1.9. The evaporation times are well predicted by the theoretical model. No evidence is found for droplet break-up for Weber numbers up to 13, and droplet radii of the order of 1m.On leave at Institute of Fluid Science, Shock Wave Research Center, Tohoku University, Sendai 980, JapanThis 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
18.
Some aspects of streamwise vortex behavior during oblique shock wave/vortex interaction 总被引:1,自引:0,他引:1
An experimental study of the flowfield generated by the interaction of a streamwise vortex having a strong wake-type axial
Mach number profile and a two-dimensional oblique shock wave was conducted in a Mach 2.49 flow. The experiments were aimed
at investigating the dynamics of supersonic vortex distortion and to study downstream behavior of a streamwise vortex during
a strong shock wave/vortex encounter. The experiments involved positioning an oblique shock generator in the form of a two-dimensional
wedge downstream of a semi-span, vortex generator wing section so that the wing-tip vortex interacted with the otherwise planar
oblique shock wave. Planar laser sheet visualizations of the flowfield indicated an expansion of the vortex core in crossing
a spherically blunt-nose shock front. The maximum vortex core diameter occurred at a distance of 12.7 mm downstream of the
wedge leading edge where the vortex had a core diameter of more than double its undisturbed value. At distances further downstream
the vortex core diameter remained nearly constant, while it appeared to become more diffused at distances far from the wedge
leading edge. Measurements of vortex trajectory revealed that the vortex convected in the freestream direction immediately
downstream of the bulged-forward shock structure, while it traveled parallel to the wedge surface at distances further downstream.
The turbulent distorted vortex structure which formed as a result of the interaction, was found to be sensitive to downstream
disturbances in a manner consistent with incompressible vortex breakdown. Physical arguments are presented to relate behavior
of streamwise vortices during oblique and normal shock wave interactions.
Received 7 September 1996 / Accepted 10 February 1998 相似文献
19.
Results from an experimental investigation of the interaction of a “non-ideal” shock wave and a single obstacle are reported. The shock wave is produced ahead of an accelerated flame in a 14 cm inner-diameter tube partially filled with orifice plates. The shock wave interacts with a single larger blockage orifice plate placed 15–45 cm after the last orifice plate in the flame acceleration section of the tube. Experiments were performed with stoichiometric ethylene–oxygen mixtures with varying amounts of nitrogen dilution at atmospheric pressure and temperature. The critical nitrogen dilution was found for detonation initiation. It is shown that detonation initiation occurs if the chemical induction time based on the reflected shock state is shorter than the time required for an acoustic wave to traverse the orifice plate upstream surface, from the inner to the outer diameter. The similarity between the present results and those obtained from previous investigators looking at detonation initiation by ideal shock reflection produced in a shock tube indicates that the phenomenon is not sensitive to the detailed structure of the shock front but only on the average shock strength.This paper is based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive Systems, Montreal, Canada, July 31–August 5, 2005. 相似文献
20.
A numerical study of the interaction of plane blast waves with a cylinder is presented. Computations are carried out for
various blast-wave durations and comparisons are obtained with the corresponding results of planar shock-wave. Both inviscid
and viscous results based on the solution of the Euler and Navier-Stokes equations are presented. The equations are solved
by an adaptive-grid method and a second-order Godunov scheme. The shock wave diffraction over the cylinder is investigated
by means of various contour plots, as well as, pressure and skin-friction histories. The study reveals that the blast-wave
duration significantly influences the unsteady flow over the cylinder. The differences between the viscous and inviscid results
are also discussed.
Received 2 March 1996 / Accepted 28 February 1997 相似文献