scholarly journals Numerical Study of Air Flow Induced by Shock Impact on an Array of Perforated Plates

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 1051
Author(s):  
Lite Zhang ◽  
Zilong Feng ◽  
Mengyu Sun ◽  
Haozhe Jin ◽  
Honghui Shi
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Air Flow ◽  
Perforated Plate ◽  
Incident Shock ◽  
Reflected Shock Wave ◽  
Perforated Plates ◽  
Reflected Shock ◽  
Shock Mach Number ◽  
Dynamic Wave

This study is focused on the propagation behavior and attenuation characteristics of a planar incident shock wave when propagating through an array of perforated plates. Based on a density-based coupled explicit algorithm, combined with a third-order MUSCL scheme and the Roe averaged flux difference splitting method, the Navier–Stokes equations and the realizable k-ε turbulence model equations describing the air flow are numerically solved. The evolution of the dynamic wave and ring vortex systems is effectively captured and analyzed. The influence of incident shock Mach number, perforated-plate porosity, and plate number on the propagation and attenuation of the shock wave was studied by using pressure- and entropy-based attenuation rates. The results indicate that the reflection, diffraction, transmission, and interference behaviors of the leading shock wave and the superimposed effects due to the trailing secondary shock wave are the main reasons that cause the intensity of the leading shock wave to experience a complex process consisting of attenuation, local enhancement, attenuation, enhancement, and attenuation. The reflected shock interactions with transmitted shock induced ring vortices and jets lead to the deformation and local intensification of the shock wave. The formation of nearly steady jets following the array of perforated plates is attributed to the generation of an oscillation chamber for the inside dynamic wave system between two perforated plates. The vorticity diffusion, merging and splitting of vortex cores dissipate the wave energy. Furthermore, the leading transmitted shock wave attenuates more significantly whereas the reflected shock wave from the first plate of the array attenuates less significantly as the shock Mach number increases. The increase in the porosity weakens the suppression effects on the leading shock wave while increases the attenuation rate of the reflected shock wave. The first perforated plate in the array plays a major role in the attenuation of the shock wave.

An investigation of the metastable argon atoms in a shock tube driven atomic beam

1969 ◽  
Vol 312 (1508) ◽  
pp. 1-12
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Atomic Beam ◽  
Rotating Disk ◽  
Copper Surface ◽  
Reflected Shock Wave ◽  
Reflected Shock ◽  
Wave Measurements ◽  
Shock Mach Number ◽  
Primary Shock

Metastable atoms and photons have been detected in the beam by their ability to eject electrons from a copper surface. The contribution due to the metastable atoms was found by 'chopping’ the beam with a rotating disk so that the signals due to metastable atoms were displaced in time relative those due to photoemission. The velocity of the atoms found agreed well with the theoretical flow velocity of gas expanding supersonically from the region behind the reflected shock wave. Measurements have been made for primary shock Mach numbers between 6.1 and 8.7 and typical values of the intensity and velocity of the atoms for a primary shock Mach number of 6.34 are 1 x 10 16 metastable atoms sr -1 s -1 and 3.08 x 10 3 m/s respectively.

scholarly journals Three-dimensional simulation of combustion, detonation and deflagration to detonation transition processes

2018 ◽  
Vol 209 ◽  
pp. 00003
Author(s):  
Nickolay Smirnov ◽  
Valeriy Nikitin
Keyword(s):  
Shock Wave ◽  
Three Dimensional ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Reflected Shock Wave ◽  
Zone Formation ◽  
Flame Acceleration ◽  
Reflected Shock ◽  
Transient Regimes ◽  
Chemically Reacting

The paper presents results of numerical and experimental investigation of mixture ignition and detonation onset in shock wave reflected from inside a wedge. Contrary to existing opinion of shock wave focusing being the mechanism for detonation onset in reflection from a wedge or cone, it was demonstrated that along with the main scenario there exists a transient one, under which focusing causes ignition and successive flame acceleration bringing to detonation onset far behind the reflected shock wave. Several different flow scenarios manifest in reflection of shock waves all being dependent on incident shock wave intensity: reflecting of shock wave with lagging behind combustion zone, formation of detonation wave in reflection and focusing, and intermediate transient regimes. Comparison of numerical and experimental results made it possible to validate the developed 3-D transient mathematical model of chemically reacting gas mixture flows incorporating hydrogen – air mixtures.

Paper 14: On the Reflection of Shock Waves from Deflector Plates

1965 ◽  
Vol 180 (10) ◽  
pp. 245-259
Author(s):  
W. A. Woods
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Reflected Shock Wave ◽  
Reflected Wave ◽  
Reflected Shock ◽  
Pressure Time ◽  
Wave Travel ◽  
Wave Region

The paper first explains the importance of the reflection of shock waves in the design of certain chemical plant. The theory of the reflection of shock waves is also discussed in the first part of the paper. It is shown that when a shock wave travelling along a pipe containing stationary gas reaches the outlet end of the pipe there may be ( a) a reflected expansion wave, ( b) a reflected shock wave, ( c) a reflected sound wave, ( d) no reflected wave at all, ( e) a standing shock wave situated at the end of the pipe, depending upon the strength of the incident shock wave and the amount of blockage present at the outlet end of the pipe. The conditions for each kind of reflection are determined, and in the case of the reflected shock wave region the strengths and speeds of the reflected shock waves are established throughout the region and the results are presented graphically. In the second part of the paper the results are given of experiments carried out on a shock tube fitted with various kinds of deflector plates. The experiments were performed to study the reflection of shock waves from the deflector plates by measuring pressure/time indicator diagrams near the outlet end of the pipe. The indicator diagrams revealed the approximate pressure amplitudes of the incident and reflected shock waves and also the wave travel times for the shock waves. This information was used in conjunction with the charts given in the first part of the paper to establish the deflector geometry and spacing needed in order to avoid the occurrence of a reflected shock wave.

Experimental investigation of diaphragm material combinations in a small-scale shock tube

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Anugya Singh ◽  
Aravind Satheesh Kumar ◽  
Kannan B.T.
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Shock Tube ◽  
Production Capacity ◽  
Incident Shock ◽  
Small Scale ◽  
Content Type ◽  
Shock Mach Number ◽  
Reinforcing Material ◽  
Shock Wave Mach Number

Purpose The purpose of this study is to experimentally investigate the trends in shock wave Mach number that were observed when different diaphragm material combinations were used in the small-scale shock tube. Design/methodology/approach A small-scale shock tube was designed and fabricated having a maximum Mach number production capacity to be 1.5 (theoretically). Two microphones attached in the driven section were used to calculate the shock wave Mach number. Preliminary tests were conducted on several materials to obtain the respective bursting pressures to decide the final set of materials along with the layered combinations. Findings According to the results obtained, 95 GSM tracing paper was seen to be the strongest reinforcing material, followed by 75 GSM royal executive bond paper and regular 70 GSM paper for aluminium foil diaphragms. The quadrupled layered diaphragms revealed a variation in shock Mach number based on the position of the reinforcing material. In quintuple layered combinations, the accuracy of obtaining a specific Mach number was seen to be increasing. Optimization of the combinations based on the production of the shock wave Mach number was carried out. Research limitations/implications The shock tube was designed taking maximum incident shock Mach number as 1.5, the experiments conducted were found to achieve a maximum Mach number of 1.437. Thus, an extension to further experiments was avoided considering the factor of safety. Originality/value The paper presents a detailed study on the effect of change in the material and its position in the layered diaphragm combinations, which could lead to variation in Mach numbers that are produced. This could be used to obtain a specific Mach number for a required study accurately, with a low-cost setup.

scholarly journals Unsteady aspects of an incident shock wave/turbulent boundary layer interaction

2009 ◽  
Vol 635 ◽  
pp. 47-74 ◽  
Author(s):  
R. A. HUMBLE ◽  
F. SCARANO ◽  
B. W. van OUDHEUSDEN
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Reflected Shock Wave ◽  
Reversed Flow ◽  
Layer Interaction ◽  
Reflected Shock ◽  
Boundary Layer Interaction

An incident shock wave/turbulent boundary layer interaction at Mach 2.1 is investigated using particle image velocimetry in combination with data processing using the proper orthogonal decomposition, to obtain an instantaneous and statistical description of the unsteady flow organization. The global structure of the interaction is observed to vary considerably in time. Although reversed flow is often measured instantaneously, on average no reversed flow is observed. On an instantaneous basis, the interaction exhibits a multi-layered structure, characterized by a relatively high-velocity outer region and low-velocity inner region. Discrete vortical structures are prevalent along their interface, which create an intermittent fluid exchange as they propagate downstream. A statistical analysis suggests that the instantaneous fullness of the incoming boundary layer velocity profile is (weakly) correlated with the size of the separation bubble and position of the reflected shock wave. The eigenmodes show an energetic association between velocity fluctuations within the incoming boundary layer, separated flow region and across the reflected shock wave, and portray subspace features that represent the phenomenology observed within the instantaneous realizations.

Nonsteady Supercritical Discharge Through an Orifice

1961 ◽  
Vol 83 (4) ◽  
pp. 663-670 ◽  
Author(s):  
George Rudinger
Keyword(s):  
Shock Wave ◽  
Pressure Rise ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Layer Growth ◽  
Reflected Shock Wave ◽  
Supercritical Flow ◽  
Lag Effects ◽  
Reflected Shock ◽  
Flow Adjustment

Previous studies of shock reflection from open-ended duct configurations indicate that a steady discharge is not instantaneously formed and that the effects of this lag may occasionally be important. A theory is available which satisfactorily describes the lag effects in subcritical flow, but its validity for supercritical flow has not previously been verified. Shock-tube experiments are therefore carried out to study the lag effects in supercritical flow from a sharp-edged orifice. The incident shock wave either modifies an initial supercritical discharge, or establishes such a discharge with the gas initially being at rest. Schlieren photographs show a violent transition of the flow downstream of the orifice that lasts several milliseconds. Pressure records taken inside the duct indicate a small, but distinct, pressure rise that also lasts for several milliseconds following the passage of the reflected shock wave. It is shown that this apparent agreement of the transition times is accidental. A method is described to evaluate the effect of boundary-layer growth on the pressure behind the reflected shock wave, and the results indicate that the entire observed pressure rise is accounted for by this effect. Consequently, flow adjustment in the orifice may be considered as instantaneous for all practical purposes.

Shock-wave reflection from a rigid wall in a dusty gas

1986 ◽  
Vol 404 (1826) ◽  
pp. 55-67 ◽  
Keyword(s):  
Shock Wave ◽  
Equations Of Motion ◽  
Rigid Wall ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Gas Analysis ◽  
Reflected Shock Wave ◽  
Dusty Gas ◽  
Splitting Technique ◽  
Reflected Shock

The flow that results when a shock wave in a dusty gas is reflected from a rigid wall is studied theoretically. By applying an idealized equilibrium gas analysis, it is shown that there are three types of shock reflection. The incident shock wave and the reflected shock wave are partly dispersed if the incident shock is strong the former is partly dispersed but the latter is fully dispersed if the incident shock is of intermediate strength and both of them are fully dispersed if the incident shock is weak. The equations of motion are also solved numerically with a modified random-choice method involving an operator splitting technique to study the time-dependent non-equilibrium flow. The results demonstrate the details of the formation of the reflected shock wave for the three types described.

scholarly journals Blast mitigation by perforated plates using an explosive driven shock tube: study of geometry effects and plate numbers

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
T. Schunck ◽  
D. Eckenfels
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Blast Wave ◽  
Perforated Plate ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Metallic Foam ◽  
Blast Mitigation ◽  
Geometric Means ◽  
Perforated Plates

AbstractThis work is set in the context of blast mitigation based on geometric means, namely perforated metallic plates or grids. When a shock wave passes through a perforated plate, the flow field is modified, and new shock waves are created, as well as regions of vortices and turbulence in which the energy of the wave can be dissipated. In this study, an explosive driven shock tube (EDST) was used to visualize the interaction of a blast wave with perforated plates or with a piece of cast metallic foam. Additionally, the overpressure and the impulse of the reflected blast wave on a wall located downstream were assessed. The use of an EDST allowed the evaluation of the mitigation capacity under a high dynamic loading. Several combinations of perforated plates were tested, varying the geometry and the number of plates, as well as switching between two different spacings. When the shock wave collided with a plate, we observed that part of the incident shock wave was reflected by the plate, while the remaining wave was transmitted through it. Downstream of the plate, both the overpressure and the impulse were reduced, this effect being more prominent as the porosity of the plates decreased. When two plates were placed as obstacles, this phenomenon of reflection/transmission was repeated twice consecutively, further reducing the downstream reflected overpressure and impulse. An array of three plates or a piece of metallic foam were even more effective in mitigating the blast wave. Varying the distance between two or three plates had no effect on blast mitigation.

Shock reflexion and shock-wave interaction in field-aligned flows

1975 ◽  
Vol 14 (1) ◽  
pp. 39-51 ◽  
Author(s):  
Manfred Natter
Keyword(s):  
Shock Wave ◽  
Wave Interaction ◽  
Flow Speed ◽  
Ideal Gas ◽  
Incident Shock ◽  
Reflected Shock Wave ◽  
Heat Conducting ◽  
Fluid Medium ◽  
Reflected Shock ◽  
Monatomic Gas

This paper considers the steady two-dimensional problem of regular reflexion and symmetric intersection of oblique magnetogasdynamic shock waves. It is assumed that the fluid medium is a non-viscous, non-heat-conducting, ideal gas of infinite electrical conductivity, and that the applied magnetic field is parallel to the velocity of the approaching stream. In view of the complexity of the shock relations, a graphical method is presented for determining the orientation and strength of the reflected shock wave in terms of the Laval number M*1 (flow speed divided by critical sound speed), the Alfvén number A1 (flow speed divided by Alfvén speed), and the shock angle ϑ 1 ahead of the incident shock. Moreover, the possible ranges of M*1, A1, and ϑ 1, for which regular reflexion may occur, are calculated and illustrated graphically for the case of a monatomic gas.

The shape of a diffracting shock wave

1967 ◽  
Vol 29 (2) ◽  
pp. 297-304 ◽  
Author(s):  
B. W. Skews
Keyword(s):  
Shock Wave ◽  
Experimental Study ◽  
Mach Number ◽  
Sound Wave ◽  
Diffraction Theory ◽  
Incident Shock ◽  
Linearized Theory ◽  
Shock Mach Number ◽  
Mach Numbers ◽  
Good For

This paper describes an experimental study of the shape of a shock diffracting around a corner made up of two plane walls, for corner angles from 15 to 165° (in 15° steps) and shock Mach numbers from M0 = 1·0 to 4·0. The results are compared with profiles determined from the diffraction theory of Whitham (1957, 1959). The agreement is shown to be good for an incident shock Mach number of 3·0, and fair in other cases. The behaviour is found to follow the trends established by Lighthill (1949) in a linearized theory. Results for the Mach number of the wall shock are also presented. The shock does not degenerate to a sound wave even for large corner angles and low Mach numbers.

Sign in / Sign up

Export Citation Format

Share Document