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191.
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
192.
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
193.
The unsteady behavior of flow driven by a jet suddenly injected into an elliptical cell is numerically studied by solving
the axisymmetric two-dimensional compressible Navier–Stokes equations. This system is a model of laser ablation of a certain
duration followed by a discharging process through the exit hole at the downstream end of the cell. The parameters for the
calculations are the exit diameter of the cell, the Mach number and duration of the injected jet. The injected jet becomes
a traveling plume approaching the downstream end of the elliptical cell and discharges from the cell through an exit hole.
The plume generates and interacts with a shock wave in the elliptical cell. The unsteady flow properties downstream of the
cell are found to be attenuated by the combination of the phenomena occurring in the cell and at the exit. Monitoring the
velocity at the exit hole is used to clarify the characteristics of the flow and apply them to applications in pulse laser
ablation. The results show that the vortex in the plume head with the same radius as the exit diameter (i.e., De/Dj = 2.7, where De is the exit diameter and Dj is the injected jet diameter) causes a relatively constant velocity at the exit for about 10 μs. In the downstream flow characteristics,
the suddenly injected jet makes a single or double peak in the velocity variation outside the cell depending on the combination
of parameters. This suggests that a single laser pulse might generate two beams through the exit hole of a cell, which could
increase the efficiency of beam generation with the combination of an elliptical cell and the laser ablation. It is also found
that the wave form of the variations and their level are roughly determined by the durations of the jet and the exit diameters
of the cell exit, respectively.
PACS 51.35.+a; 47.40.Nm 相似文献
194.
Available test time is an important issue for ground-based flow research, particularly for impulse facilities such as shock
tunnels, where test times of the order of several ms are typical. The early contamination of the test flow by the driver gas
in such tunnels restricts the test time. This paper reports measurements of the driver gas arrival time in the test section
of the T4 free-piston shock-tunnel over the total enthalpy range 3–17 MJ/kg, using a time-of-flight mass spectrometer. The
results confirm measurements made by previous investigators using a choked duct driver gas detector at these conditions, and
extend the range of previous mass spectrometer measurements to that of 3–20 MJ/kg. Comparisons of the contamination behaviour
of various piston-driven reflected shock tunnels are also made.
PACS 07.75.th; 47.40.-x 相似文献
195.
Experimental results on the shock structure of dual co-axial jets are presented. The effects of the geometric parameters of
the inner nozzle, jet static pressure ratio (ratio of the exit plane static pressures of the inner and outer nozzles) and
the ratio of outer to inner nozzle throat area on the shock structure were studied. A superimposed outer and inner jet structure
was observed in the schlieren photographs. The inner flow is compressed by the outer flow resulting in the formation of a
Mach disc and an exit shock. A parameter incorporating the effect of Mach number of the inner nozzle and jet static pressure
ratio was found to correlate the observations regarding the Mach disc location. 相似文献
196.
B. E. Gelfand A. M. Bartenev S. P. Medvedev A. N. Polenov S. V. Khomik M. Lenartz H. Grönig 《Shock Waves》1994,4(3):137-143
On the basis of numerical modeling specific features of shock wave reflections were analyzed. It was found, that after diaphragm rupture self-modeling pressure and velocity distributions nearby the shock front establish. But in some special cases the temperature behind the shock front can rise. This peculiarity should be taken into account when performing experiments with high reactive gaseous mixtures. The temperature on the shock front and the velocity gradient behind it are uniform in the case of strong blast wave reflections. This effect is observed in the zone with an elevated temperature profile behind the incident blast wave. The reflected triangular waves conserve a quasi-self-modeling character by pressure. Typical experiments were carried out to verify the theoretical predictions. The effects of reflected wave acceleration in the case of triangular waves and the self-similar character of the pressure profiles were observed.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
197.
Shock wave attenuation in polyurethane foams is investigated experimentally and numerically. This study is a part of research project regarding shock propagation in polyurethane foams with high-porosities
= 0.951 ~ 0.977 and low densities of ρc = 27.6 ~55.8 kg/m3. Sixty Millimeter long cylindrical foams with various cell numbers and foam insertion condition were installed in a horizontal shock tube of 50 mm i.d. and 5.4 mm in length. Results of pressure measurements in air/foam combination are compared with CFD simulation solving the one-dimensional Euler equations. In the case of a foam B fixed on shock tube wall, pressures at the shock tube end wall increases relatively slowly comparing to non-fixed foam, free to move and a foam A fixed on shock tube wall. This implies that elastic inertia hardly contributes to pressure build up. Pressures behind a foam C fixed on shock tube wall decrease indicating that shock wave is degenerated into compression wave. Dimensionless impulse and attenuation factor decrease as the initial cell number increases. The momentum loss varies depending on cell structure and cell number. 相似文献
198.
Shock compression was used to produce the first observation of a metallic state of condensed hydrogen. The conditions of
metallization are a pressure of 140 GPa (1.4 Mbar), 0.6 g/cm (ninefold compression of initial liquid-H density), and 3000 K. The relatively modest temperature generated by a reverberating shock wave produced the metallic state
in a warm fluid at a lower pressure than expected previously for the crystallographically ordered solid at low temperatures.
The relatively large sample diameter of 25 mm permitted measurement of electrical conductivity. The experimental technique
and data analysis are described.
Received 12 November 1997 / Accepted 10 November 1998 相似文献
199.
Burgers-KdV混合型方程的显式精确解 总被引:3,自引:0,他引:3
本文提出了双参数假设,用直接积分的方法得到了Burgers-KdV方程的显式精确解,分析了解的结构。 相似文献
200.
用X-rayDiffraction(XRD)研究激波对FeCuNbSiB非晶合金的影响。结果表明:一定强度的激波能使非晶态转变为晶态,而且晶粒尺寸在100纳米范围内。 相似文献