Shock-tube studies of vibrational relaxation in nitrous oxide

1966 ◽  
Vol 25 (4) ◽  
pp. 817-820 ◽  
Author(s):  
J. K. Bhangu
Keyword(s):  
Nitrous Oxide ◽  
Mach Number ◽  
Shock Waves ◽  
Shock Tube ◽  
Vibrational Relaxation ◽  
Density Ratio ◽  
Zehnder Interferometer ◽  
Experimental Investigations ◽  
Number Range ◽  
Good Agreement

Results of experimental investigations of vibrational relaxation regions of shock waves in nitrous oxide are reported in this paper. The Mach-number range covered was from 1·5 to 7·5 and the photographs of the shocks were made using a Mach-Zehnder interferometer and a spark source. The experimental and calculated values of the over-all density ratio were found to be in good agreement, and the values of the relaxation frequencies were consistent with the data of other workers.

Density profiles in argon and nitrogen shock waves measured by the absorption of an electron beam

1976 ◽  
Vol 74 (3) ◽  
pp. 497-513 ◽  
Author(s):  
H. Alsmeyer
Keyword(s):  
Electron Beam ◽  
Mach Number ◽  
Shock Waves ◽  
Shock Tube ◽  
Rotational Relaxation ◽  
Density Profiles ◽  
Number Range ◽  
Realistic Interaction ◽  
Mach Numbers ◽  
Interaction Law

Accurate measurements of the density distribution in Ar and N2 shock waves have been made in a shock tube for the Mach number range from 1.55 to 9 and 10 respectively by the absorption of an electron beam. A modified absorption law has been used for data reduction. The density profiles were corrected for the influence of shock curvature and density rise behind the shock wave. The measurements in Ar agree to within 1% with those of Schmidt (1969) in the mean range of Ms but give a slightly smaller density gradient for Ms = 9. Comparison with various theories shows very good agreement with Bird's Monte Carlo simulation in the whole Mach number range for a simple repulsive intermolecular force law. Further, the agreement with the Mott-Smith density profile for the same interaction law is also good, and surprisingly is found to be better for lower than for higher Mach numbers. Qualitative agreement is obtained with the solutions of Hicks & Yen for hard-sphere and Maxwell molecules. The Navier-Stokes and BGK solutions are found to differ significantly from the present experiments even for the lowest measured Mach number (1·55), whereas the Burnett equation gives better agreement, especially with respect to the asymmetry of the profiles.The measured N2 profiles agree on the whole with the shock-tube measurements of other investigators but show substantial deviations from the low density wind-tunnel experiments of Robben & Talbot (1966b) for higher Mach numbers. Bird's ‘energy sink model’ (1971) is in agreement with the measured density profiles for a realistic interaction law and a suitable rotational collision number. Rotational relaxation in nitrogen is found to be very fast for all Mach numbers. Consequently the coupling between rotational and translational relaxation is very strong.

Equilibrium Thermodynamic Properties Behind Strong Shocks in Helium

1968 ◽  
Vol 72 (686) ◽  
pp. 155-159
Author(s):  
M. Lalor ◽  
H. Daneshyar
Keyword(s):  
Mach Number ◽  
Partition Function ◽  
Shock Waves ◽  
Thermodynamic Properties ◽  
Strong Shock ◽  
Equilibrium Thermodynamic ◽  
Ionized Gas ◽  
Number Range ◽  
Shock Mach Number ◽  
Strong Shock Waves

Summary Tables of equilibrium thermodynamic properties of the ionized gas formed behind strong shock waves in Helium are presented, in the Mach number range 10 to 30, for initial pressures of 0-1, 0-5, 1, 5, 10, 50, 100 torr. The effect of the inclusion of the full partition function series is demonstrated in the Mach number range 20 to 30. A numerical solution has been developed such that the only experimental quantities required for its use are the shock Mach number and the pre-shock conditions.

scholarly journals Secondary breakup of a drop at moderate Weber numbers

2015 ◽  
Vol 471 (2177) ◽  
pp. 20140930 ◽  
Author(s):  
Mohit Jain ◽  
R. Surya Prakash ◽  
Gaurav Tomar ◽  
R. V. Ravikrishna
Keyword(s):  
Numerical Simulations ◽  
Lognormal Distribution ◽  
Weber Number ◽  
Drop Size ◽  
Density Ratio ◽  
Transition Regime ◽  
Number Range ◽  
High Density Ratio ◽  
Secondary Breakup ◽  
Good Agreement

We present volume of fluid based numerical simulations of secondary breakup of a drop with high density ratio (approx. 1000) and also perform experiments by injecting monodisperse water droplets in a continuous jet of air and capture the breakup regimes, namely, bag formation, bag-stamen, multibag and shear breakup, observed in the moderate Weber number range (20–120). We observe an interesting transition regime between bag and shear breakup for We =80, in both simulations as well as experiments, where the formation of multiple lobes, is observed, instead of a single bag, which are connected to each other via thicker rim-like threads that hold them. We show that the transition from bag to shear breakup occurs owing to the rim dynamics which shows retraction under capillary forces at We =80, whereas the rim is sheared away with flow at We =120 thus resulting in a backward facing bag. The drop characteristics and timescales obtained in simulations are in good agreement with experiments. The drop size distribution after the breakup shows bimodal nature for the single-bag breakup mode and a unimodal nature following lognormal distribution for higher Weber numbers.

Some Experimental Results of Two-Dimensional Compressor Cascades at Supersonic Inlet Velocities

1970 ◽  
Vol 92 (3) ◽  
pp. 267-274 ◽  
Author(s):  
H. Starken ◽  
H. J. Lichtfuss
Keyword(s):  
Mach Number ◽  
Density Ratio ◽  
Great Influence ◽  
Simple Calculation ◽  
Two Dimensional ◽  
Number Range ◽  
Pressure Loss Coefficient ◽  
Supersonic Inlet ◽  
Profile Losses ◽  
Total Pressure Loss Coefficient

The paper presents two-dimensional cascade results which have been obtained in transonic and supersonic cascade windtunnels. The upstream Mach number range is 1,0 ≤ M1 ≤ 1,4. Tests have been carried out with three different blade shapes; these are double-circular-arc and wedge profiles. The influence of solidity on the performance of these cascades has been investigated. A detailed analysis and calculation of the shock losses shows the great influence of profile shape on the total pressure loss coefficient. The profile losses are roughly constant in the investigated Mach number range. In addition, some measurements for different back pressures are presented. These results are analyzed with the aid of a simple calculation, which shows that the axial velocity-density ratio has to be considered as an important parameter in supersonic cascade measurements.

Measurement of the relaxation frequency of the asymmetric stretching mode of carbon dioxide

1969 ◽  
Vol 35 (1) ◽  
pp. 171-183 ◽  
Author(s):  
J. P. Hodgson ◽  
R. J. Hine
Keyword(s):  
Carbon Dioxide ◽  
Shock Waves ◽  
Shock Tube ◽  
Vibrational Relaxation ◽  
Thermal Emission ◽  
Relaxation Frequency ◽  
Rate Of Change ◽  
Density Measurements ◽  
Bending Mode ◽  
Made In

The vibrational relaxation frequency of carbon dioxide has been determined by measuring the rate of change of thermal emission in shock waves near 4±3μ. This method of measuring the relaxation frequency depends mainly on the degree of excitation of the asymmetric stretching mode of the molecule, and the results are compared with those of earlier density measurements made in the same shock tube. The gas samples used are not optically thin, and it is shown that self-absorption can be taken into account. The results imply that the relaxation frequency of the asymmetric stretching mode is about 70% of that of the bending mode.

The perturbed region behind a diffracting shock wave

1967 ◽  
Vol 29 (4) ◽  
pp. 705-719 ◽  
Author(s):  
B. W. Skews
Keyword(s):  
Shock Wave ◽  
Experimental Study ◽  
Mach Number ◽  
Shock Waves ◽  
Contact Surface ◽  
Fair Agreement ◽  
Number Range ◽  
Corner Angle ◽  
Theoretical Predictions

The results of an experimental study of the diffraction of shock waves on plane-walled convex corners are given for a Mach number range from 1·0 to 5·0. The behaviour of the disturbances produced in the region perturbed by the corner are discussed. It is shown that the position of the slipstream and tail of the Prandtl-Meyer fan, and the velocities of the contact surface and second shock become independent of corner angle for angles greater than 75°. Comparisons with theoretical predictions of Jones, Martin & Thornhill (1951) and Parks (1952) are included. In most cases fair agreement is obtained.

Shock‐Tube Study of Vibrational Relaxation in Nitrous Oxide

1968 ◽  
Vol 49 (2) ◽  
pp. 509-513 ◽  
Author(s):  
C. J. S. M. Simpson ◽  
K. B. Bridgman ◽  
T. R. D. Chandler
Keyword(s):  
Nitrous Oxide ◽  
Shock Tube ◽  
Vibrational Relaxation ◽  
Tube Study

Vortex shedding behind a square cylinder in transonic flows

1987 ◽  
Vol 178 ◽  
pp. 303-323 ◽  
Author(s):  
Takeo Nakagawa
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Shock Waves ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Acoustic Waves ◽  
Strong Shock ◽  
Square Cylinder ◽  
Number Range ◽  
Reynolds Number Range

This paper is primarily concerned with Mach-number effects on the vortex shedding behind a square cylinder (side length D = 20 mm) in a Reynolds-number range of 0.696 × 105 < Re < 4.137 × 105, and a Mach-number range of 0.1522 < M < 0.9049.Regular periodic vortex shedding is present, irrespective of the appearance of shock waves around a square cylinder. The shape of the vortices is, however, deformed by the shock waves, and each vortex centre becomes non-uniform while the vortex passes through the gap between the upper and lower shock waves. Weak shock waves around the square cylinder do not alter the Strouhal number, but strong shock waves weaken the vortex shedding and increase the Strouhal number suddenly. Acoustic waves have been recorded by the Mach-Zehnder interferometer when the Mach number is close to the critical value. The acoustic waves are generated most strongly at the instant when each vortex hits the foot of the shock waves formed above and below the vortex formation region.From the present work and that of Okajima (1982), it is suggested that the Strouhal number of alternating vortices shed from a square cylinder can be estimated to be about 0.13 in the Reynolds-number range between 102 and 3.4 × 105.

Instabilities of intense shock waves in monatomic gases

1997 ◽  
Vol 58 (3) ◽  
pp. 385-394 ◽  
Author(s):  
R. ANNOU ◽  
B. FERHAT
Keyword(s):  
Differential Equation ◽  
Mach Number ◽  
Shock Waves ◽  
Shock Tube ◽  
Wave Front ◽  
Strong Shock ◽  
Equation System ◽  
Relaxation Processes ◽  
Differential Equation System ◽  
Strong Shock Waves

A wave-front distortion of strong shock waves in gases for particular Mach numbers M has been repeatedly noted. We propose two approaches according to which there is a threshold Mach number above which the instability occurs; this Mach number is related to the unperturbed gas pressure P1. The first approach is macroscopic, and takes account of radiation; the second is microscopic, and takes account of radiation, electron diffusion to the walls of the shock tube and the non-equilibrium relaxation processes. A mechanism of four reactions is proposed. A nonlinear differential equation system is established. The latter becomes unstable for critical values of the Mach number.

Further results on the over-all density ratios of shock waves in carbon dioxide

1963 ◽  
Vol 17 (2) ◽  
pp. 267-270 ◽  
Author(s):  
H. K. Zienkiewicz ◽  
N. H. Johannesen ◽  
J. H. Gerrard
Keyword(s):  
Carbon Dioxide ◽  
Mach Number ◽  
Shock Waves ◽  
Density Ratio ◽  
Shock Mach Number ◽  
Density Ratios

Previous results on the over-all density ratio of shock waves in CO2, confirming experimentally the theoretical equilibrium value, have been extended to a shock Mach number of 7·3. The discrepancy between our results and earlier Princeton results approaches 18% at a Mach number of 7. Possible reasons for this are discussed, with particular reference to the interferometer technique, but no explanation has been found.

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