Strong shock propagation through decreasing density

1972 ◽  
Vol 54 (2) ◽  
pp. 297-304 ◽  
Author(s):  
D. A. Freiwald
Keyword(s):  
Strong Shock ◽  
Limited Range ◽  
Ideal Gas ◽  
Experimental Results ◽  
Shock Acceleration ◽  
Shock Propagation ◽  
Final State ◽  
Free Expansion ◽  
Real Gas Effects ◽  
Expansion Model

The acceleration of a shock wave in an ideal gas of decreasing density has previously been studied. The problem is reconsidered here with empirical inclusion of real-gas effects for strong shocks in hydrogen. Experimental results suggest that previous shock acceleration models are valid only for a limited range of the Knudsen number in finite geometries and that for large final-state Knudsen numbers a free-expansion model best describes the experimental results.

scholarly journals Radiation effects on shock propagation in Al target relevant to equation of state measurements

2007 ◽  
Vol 25 (1) ◽  
pp. 23-30 ◽  
Author(s):  
T. DESAI ◽  
R. DEZULIAN ◽  
D. BATANI
Keyword(s):  
Equation Of State ◽  
Reference Material ◽  
Radiation Effects ◽  
Laser Energy ◽  
Strong Shock ◽  
Shock Propagation ◽  
Laser Irradiance ◽  
X Rays ◽  
High Laser ◽  
High Intensity Laser

We present one-dimensional simulations performed using the multi group radiation hydro code MULTI with the goal of analyzing the target preheating effect under conditions similar to those of recent experiments aimed at studying the Equation of State (EOS) of various materials. In such experiments, aluminum is often used as reference material; therefore its behavior under strong shock compression and high-intensity laser irradiation (1013–1014 W/cm2) should be studied in detail. Our results reveal that at high laser irradiance, the laser energy available to induce shock pressure is reduced due to high X-rays generation. Simultaneously X-rays preheat the bulk of the reference material causing significant heating prior to shock propagation. Such effects induce deviations in shock propagation with respect to cold aluminum.

The determination of arc temperatures from shock velocities

1957 ◽  
Vol 240 (1220) ◽  
pp. 54-66 ◽  
Keyword(s):  
Shock Wave ◽  
Strong Shock ◽  
Weak Shock ◽  
Wave Theory ◽  
New Method ◽  
Shock Propagation ◽  
Plane Shock ◽  
Gas Temperature ◽  
Specific Heats ◽  
Arc Discharges

The measurement of the high gas temperatures associated with arc discharges requires special techniques. One such method, developed by Suits (1935), depends on the measure­ment of the velocity of a sound wave passing through an arc column, although in fact Suits measured the velocity of a very weak shock wave. The new method described in the present paper is one in which temperatures are determined from the measurement of the velocity of a relatively strong shock wave propagated through an arc. The new method has the merit of consistently producing accurately measurable records and of increasing the accuracy of the temperature determination. The shock velocities are measured by means of a rotating mirror camera. Within the arc, the shock propagation is observable by virtue of the increased arc brightness produced by the shock. In the non-luminous regions surrounding the arc, the shock propagation is displayed by means of a Schlieren system. The interpretation of the measurements depends upon a one-dimensional analysis given in this paper which is similar to that of Chisnell (1955) and which describes the interaction of a plane shock with a con­tinuously varying temperature distribution. In our analysis account is taken also of the continuous variation in specific heats and molecular weight which are of importance under high gas temperature conditions. In practice plane wave theory cannot adequately describe the shock propagation, since attenuation occurs both in the free gas and in the arc column. The effects of this attenuation on the temperature determinations may be accounted for by the use of an experimentally determined attenuation relationship given in the paper. The finally developed method yields temperature values to an accuracy of ± 2%. Experiments are described for carbon and tungsten arcs in air and nitrogen for currents up to 55 amperes and pressures up to 3 atmospheres. The values obtained range from 6200 to 7700° K and are in good agreement with values determined by other techniques.

scholarly journals Fermi bubbles from stochastic acceleration of electrons in a Galactic outflow

2019 ◽  
Vol 622 ◽  
pp. A203 ◽  
Author(s):  
P. Mertsch ◽  
V. Petrosian
Keyword(s):  
Large Scale ◽  
Transport Coefficients ◽  
Strong Shock ◽  
High Energy ◽  
Brightness Distribution ◽  
Shock Acceleration ◽  
Galactic Centre ◽  
Large Reservoir ◽  
Stochastic Acceleration ◽  
Multi Wavelength

The discovery of the Fermi bubbles – a huge bilobular structure seen in GeV gamma-rays above and below the Galactic centre – implies the presence of a large reservoir of high energy particles at ~10 kpc from the disk. The absence of evidence for a strong shock coinciding with the edge of the bubbles, and constraints from multi-wavelength observations point towards stochastic acceleration by turbulence as a likely mechanism of acceleration. We have investigated the time-dependent acceleration of electrons in a large-scale outflow from the Galactic centre. For the first time, we present a detailed numerical solution of the particle kinetic equation that includes the acceleration, transport and relevant energy loss processes. We also take into account the addition of shock acceleration of electrons at the bubble’s blast wave. Fitting to the observed spectrum and surface brightness distribution of the bubbles allows determining the transport coefficients, thereby shedding light on the origin of the Fermi bubbles.

Propagation of strong shock waves in a non-ideal gas

2019 ◽  
Vol 159 ◽  
pp. 96-104 ◽  
Author(s):  
Amit Tomar ◽  
Rajan Arora ◽  
Antim Chauhan
Keyword(s):  
Shock Waves ◽  
Strong Shock ◽  
Ideal Gas ◽  
Strong Shock Waves

Supercooling in hypersonic nitrogen wind tunnels

1994 ◽  
Vol 269 ◽  
pp. 283-299 ◽  
Author(s):  
Wayland C. Griffith ◽  
William J. Yanta ◽  
William C. Ragsdale
Keyword(s):  
Vibrational Energy ◽  
Ideal Gas ◽  
Wind Tunnels ◽  
Pure Nitrogen ◽  
Real Gas ◽  
Absolute Limit ◽  
Real Gas Effects ◽  
Supercooled Region ◽  
The Ideal

Recent experimental observation of supercooling in large hypersonic wind tunnels using pure nitrogen identified a broad range of non-equilibrium metastable vapour states of the flow in the test cell. To investigate this phenomenon a number of real-gas effects are analysed and compared with predictions made using the ideal-gas equation of state and equilibrium thermodynamics. The observed limit on the extent of supercooling is found to be at 60% of the temperature difference from the sublimation line to Gibbs’ absolute limit on phase stability. The mass fraction then condensing is calculated to be 12–14%. Included in the study are virial effects, quantization of rotational and vibrational energy, and the possible role of vibrational relaxation and freezing in supercooling. Results suggest that use of the supercooled region to enlarge the Mach–Reynolds number test envelope may be practical. Data from model tests in supercooled flows support this possibility.

Experimental Measurement of a Three Lobe Air Bearing Rotordynamic Coefficients

2006 ◽  
Author(s):  
Rafael O. Ruiz ◽  
Marcelo H. Di Liscia ◽  
Sergio Di´az ◽  
Luis Medina
Keyword(s):  
Reynolds Equation ◽  
Ideal Gas ◽  
Magnetic Bearing ◽  
Experimental Results ◽  
Rotating Speed ◽  
Rotordynamic Coefficients ◽  
Fluid Film Bearings ◽  
Bearing Force ◽  
Air Film ◽  
Gas Journal Bearing

This work presents direct experimental measurements of air film rotordynamic coefficients on a three lobe bearing. The test rig uses two magnetic bearing actuators to impose desired test orbits to the journal. Tests are conducted at several rotating speeds up to 12,000rpm. Journal whirling excitation is independent of the rotating speed, thus allowing asynchronous excitations. One-dimensional orbits in the horizontal and vertical axes are applied as excitations at each rotating speed. The experimental results show the behavior of the rotordynamic coefficients of the air film bearing under synchronous and asynchronous excitation. The synchronous experimental results are compared to numerical estimation of the bearing force coefficients through solution of the isotropic ideal gas journal bearing Reynolds equation coupled with the pressure drop through the feeding holes. The results of this work prove the suitability of the rig to identify both the synchronous and nonsynchronous response of air fluid film bearings.

Experimental results on proton-proton interactions at 10 GeV/c with six charged particles in the final state

1968 ◽  
Vol 57 (1) ◽  
pp. 20-38 ◽  
Author(s):  
S. O. Holmgren ◽  
S. Nilsson ◽  
T. Olhede ◽  
N. Yamdagni
Keyword(s):  
Charged Particles ◽  
Experimental Results ◽  
Final State ◽  
Proton Proton

A numerical scheme for shock propagation in three dimensions

1988 ◽  
Vol 416 (1850) ◽  
pp. 179-198 ◽  
Keyword(s):  
Numerical Scheme ◽  
Three Dimensional ◽  
Experimental Results ◽  
Three Dimensions ◽  
Shock Propagation ◽  
Two Dimensional ◽  
Shock Surface ◽  
Shock Dynamics ◽  
Geometrical Shock Dynamics ◽  
Three Space

A numerical scheme for shock propagation in three space dimensions is presented. The motion of the leading shock surface is calculated by using Whitham’s theory of geometrical shock dynamics. The numerical scheme is used to examine the focusing of initially curved shock surfaces and the diffraction of shocks in a pipe with a 90° bend. Numerical and experimental results for the corresponding two-dimensional or axi-symmetrical cases are used to compare with the new and more complicated three-dimensional results.

From free expansion to abrupt compression of an ideal gas

2008 ◽  
Vol 30 (1) ◽  
pp. 177-183 ◽  
Author(s):  
Joaquim Anacleto ◽  
Mário G Pereira
Keyword(s):  
Ideal Gas ◽  
Free Expansion
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