An experimental study of liquefaction shock waves

1979 ◽  
Vol 95 (2) ◽  
pp. 279-304 ◽  
Author(s):  
Georg Dettleff ◽  
Philip A. Thompson ◽  
Gerd E. A. Meier ◽  
Hans-Dieter Speckmann
Keyword(s):  
Shock Wave ◽  
Incident Shock ◽  
Shock Velocity ◽  
Index Of Refraction ◽  
Clear Liquid ◽  
Two Phase ◽  
Condensation Zone ◽  
Temperature Index ◽  
Reflected Shock ◽  
Beam Attenuation

The existence of a liquefaction shock wave, a compression shock which converts vapour into liquid, has recently been predicted on physical grounds. The liquefaction shock was experimentally produced as the reflected shock at the closed end of a shock tube. Measurements of pressure, temperature, index of refraction and shock velocity confirm the existence of the shock and its general conformity to classical Rankine-Hugoniot conditions, with a discrepancy ∼ 10°C between measured and predicted liquid temperatures. Photographic observations confirmed the existence of a clear liquid phase and revealed the (unanticipated) presence of small two-phase torus-form rings. These rings are interpreted as vortices and are formed in or near the shockfront (∼ 50 rings/mm2 are visible near the shockfront at any given time). Separate experiments with the incident shock under conditions of partial liquefaction produced a fog behind the shock: measurements of laser-beam attenuation yielded the thickness of the condensation zone and estimates of the droplet size (∼ 10−7 m).

Weak shock reflection in channel flows for dense gases

2019 ◽  
Vol 874 ◽  
pp. 131-157 ◽  
Author(s):  
A. Kluwick ◽  
E. A. Cox
Keyword(s):  
Shock Wave ◽  
Practical Importance ◽  
Weak Shock ◽  
Normal Incidence ◽  
Incident Shock ◽  
Shock Reflection ◽  
Mach Stem ◽  
Dense Gases ◽  
Reflected Shock ◽  
Guderley Reflection

The canonical problem of transonic dense gas flows past two-dimensional compression/expansion ramps has recently been investigated by Kluwick & Cox (J. Fluid Mech., vol. 848, 2018, pp. 756–787). Their results are for unconfined flows and have to be supplemented with solutions of another canonical problem dealing with the reflection of disturbances from an opposing wall to finally provide a realistic picture of flows in confined geometries of practical importance. Shock reflection in dense gases for transonic flows is the problem addressed in this paper. Analytical results are presented in terms of similarity parameters associated with the fundamental derivative of gas dynamics $(\unicode[STIX]{x1D6E4})$, its derivative with respect to the density at constant entropy $(\unicode[STIX]{x1D6EC})$ and the Mach number $(M)$ of the upstream flow. The richer complexity of flows scenarios possible beyond classical shock reflection is demonstrated. For example: incident shocks close to normal incidence on a reflecting boundary can lead to a compound shock–wave fan reflected flow or a pure wave fan flow as well as classical flow where a compressive reflected shock attached to the reflecting boundary is observed. With incident shock angles sufficiently away from normal incidence regular reflection becomes impossible and so-called irregular reflection occurs involving a detached reflection point where an incident shock, reflected shock and a Mach stem shock which remains connected to the boundary all intersect. This triple point intersection which also includes a wave fan is known as Guderley reflection. This classical result is demonstrated to carry over to the case of dense gases. It is then finally shown that the Mach stem formed may disintegrate into a compound shock–wave fan structure generating an additional secondary upstream shock. The aim of the present study is to provide insight into flows realised, for example, in wind tunnel experiments where evidence for non-classical gas dynamic effects such as rarefaction shocks is looked for. These have been predicted theoretically by the seminal work of Thompson (Phys. Fluids, vol. 14 (9), 1971, pp. 1843–1849) but have withstood experimental detection in shock tubes so far, due to, among others, difficulties to establish purely one-dimensional flows.

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.

ON THE GASDYNAMIC MECHANISMS OF EXOTHERMIC REACTION WAVE FORMATION BEHIND SHOCK WAVES

2020 ◽  
Author(s):  
A. Kiverin ◽  
◽  
I. Yakovenko ◽  
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Gas Flow ◽  
Exothermic Reaction ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Wave Formation ◽  
Mixture Flow ◽  
Reflected Shock ◽  
Reaction Wave

The paper analyzes the gasdynamic evolution of the test mixture flow in the shock tube at the stage prior to reaction start. The numerical analysis clearly shows that the incepience of reaction kernels is associated with the specific features of flow development in the boundary layer behind an incident shock wave. It is shown that similar to the processes in the gas flow near a solid surface, the gasdynamic instability arises and develops in the flow behind a shock wave. The linear stage of instability development determines the formation of roll-up vortices at a certain distance behind the shock front. Further, at the nonlinear stage, these roll-up vortices transform in more complex structures that diffuse into the bulk flow. Evolution of vortices causes temperature redistribution on the scales of the boundary layer. On the one hand, there is a certain heating due to the kinetic energy dissipation. On the other hand, there are heat losses to the wall. As a result, the temperature field near the wall becomes nonuniform. The reflected shock amplifies temperature perturbations when interacts with the developed boundary layer. This mechanism determines the formation of hot kernels in which the reaction starts. So, the localized sites of exothermal reaction are arising providing conditions for reaction wave formation and propagation in the precompressed test gas.

Transition processes in shock wave interactions

1957 ◽  
Vol 2 (1) ◽  
pp. 33-48 ◽  
Author(s):  
Robert G. Jahn
Keyword(s):  
Shock Wave ◽  
Mach Reflection ◽  
Intersection Point ◽  
Incident Shock ◽  
Similar Process ◽  
Wave Interactions ◽  
Wave Refraction ◽  
Shock Interactions ◽  
Reflected Shock ◽  
Shock Wave Interactions

This paper is a discussion of recent experiments in shock-wave refraction which have clarified a special type of shock outflow process appearing to have relevance to other shock interactions, and notably to shock reflection from an oblique wall. For certain incident shock strengths and angles of incidence α, the air/methane refraction problem simulates closely the situation in the trouble-some range of the reflection problem, in which α lies between the value αe at which the theoretical solutions terminate and the value α0 that marks the onset of Mach reflection, and in which the flow deflections cannot be reconciled with theoretically permissible reflected shock strengths. In the analogous refraction cases, the reflected shock is observed to increase in strength along its length to a maximum value at the intersection point, and to be followed by a subsonic rarefaction zone which also increases in severity near the intersection. In fact, this zone appers to coalesce into a subsonic discontinuity, just at the intersection point—a feature which would contradict one of the basic assumptions of the regular reflection and refraction theories. Other refraction experiments suggest that a similar process is relevant to the Mach reflection configuration, and may account for the discrepancies in the three-shock theory for weak incident shocks.

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 Experimental investigation of shock waves in liquid helium I and II

1976 ◽  
Vol 75 (2) ◽  
pp. 373-383 ◽  
Author(s):  
John C. Cummings
Keyword(s):  
Shock Wave ◽  
Experimental Investigation ◽  
Shock Waves ◽  
Shock Tube ◽  
Liquid Helium ◽  
Initial Conditions ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Liquid Interface ◽  
Reflected Shock

The flow field produced by a shock wave reflecting from a helium gas-liquid interface was investigated using a cryogenic shock tube. Incident and reflected shock waves were observed in the gas; transmitted first- and second-sound shocks were observed in the liquid. Wave diagrams are constructed to compare the data with theoretical wave trajectories. Qualitative agreement between data and theory is shown. Quantitative differences between data and theory indicate a need for further analysis of both the gas-liquid interface and the propagation of nonlinear waves in liquid helium.This work was a first step in the experimental investigation of a complex non-equilibrium state. The results demonstrate clearly the usefulness of the cryogenic shock tube as a research tool. The well-controlled jump in temperature and pressure across the incident shock wave provides unique initial conditions for the study of dynamic phenomena in superfluid helium.

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.

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