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1.
The paper reports results of experiments regarding toroidal shock wave focusing in a vertical shock tube as a part of a series
of converging shock wave studies. This compact vertical shock tube was designed to achieve a high degree of reproducibility
with minimum shock formation distance by adopting a diaphragmless operating system. The shock tube was manufactured in the
Institute of Fluid Science, Tohoku University. An aspheric lens shaped cylindrical test section was connected at the open
end of the shock tube to visualize the diffraction and focusing of the toroidal shock wave released from the ring shaped shock
tube opening. Pressure transducers were flush mounted on the shock tube’s test section to measure pressure histories at the
converging test section. Double exposure holographic interferometry was employed to quantitatively visualize the shock waves.
The whole sequence of toroidal shock wave diffraction, focusing, and its reflection from the symmetrical axis were successfully
studied. The transition of reflected shock waves was observed. 相似文献
2.
The instability theory of shock wave in a shock tube including the effects of tube wall and contact surface is studied. The
experimental data of unstable shock wave coincide with one of instability criteria derived in the present paper. 相似文献
3.
We set up a diaphragmless driver section as the first step towards developing a shock tube at microscale which has high experimental
efficiency, independent of tube dimensions or the ratio of driver and driven pressure. The experiment described in this paper
is performed by using our diaphragmless driver section. We measured the operating time and the velocity of the fast opening
valve. Additionally we have introduced and calculated the differential equation, by using the Runge–Kutta–Gill method, to
understand the motion of the fast opening valve. We achieved good agreement between experimental and calculated results for
the velocity. We can conclude that the diaphragmless driver section is highly suitable for a narrow channel shock tube.
相似文献
4.
A new friction operated single piston shock tube driver design that is capable of generating shock waves of Mach number 1.1
to 2 is presented. By using different test gases and evacuating the driven section Mach 5 shock waves can easily be produced.
The driver is efficient with shock wave Mach numbers within 9% of that predicted by ideal shock tube theory and the non-dimensional
formation length lies between 20 and 40. The brake pad mechanism, that restrains the piston until tests commence, removes
the necessity of venting an auxiliary chamber rapidly, thus speeding up the displacement of the piston. It is believed that
the design is a practical, simple and cost effective way of generating reproducible shock tube tests with very short test
turn around times, while removing the necessity of using a diaphragm and exposing the test gases to the atmosphere. Results
for three pistons with masses of 4.4, 0.71 and 0.38 kg (brass, PVC and hollow aluminium respectively) with driver gauge pressures
of between 2 and 50 bar (Mach 1.2 to 2) are given.
Received 27 February 1998 / Accepted 8 July 1998 相似文献
5.
Shock wave interaction with a sphere is one of the benchmark tests in shock dynamics. However, unlike wind tunnel experiments, unsteady drag force on a sphere installed in a shock tube have not been measured quantitatively. This paper presents an experimental and numerical study of the unsteady drag force acting on a 80 mm diameter sphere which was vertically suspended in a 300 mm x 300 mm vertical shock tube and loaded with a planar shock wave of M
s
= 1.22 in air. The drag force history on the sphere was measured by an accelerometer installed in it. Accelerometer output signals were subjected to deconvolution data processing, producing a drag history comparable to that obtained by solving numerically the Navier-Stokes equations. A good agreement was obtained between the measured and computed drag force histories. In order to interpret the interaction of shock wave over the sphere, high speed video recordings and double exposure holographic interferometric observations were also conducted. It was found that the maximum drag force appeared not at the time instant when the shock arrived at the equator of the sphere, but at some earlier time before the transition of the reflected shock wave from regular to Mach reflection took place. A negative value of the drag force was observed, even though for a very short duration of time, when the Mach stem of the transmitted shock wave relfected and focused at the rear stagnation point of the sphere.Received: 31 March 2003, Accepted: 7 July 2003, Published online: 2 September 2003 相似文献
6.
7.
In this paper, focusing of a toroidal shock wave propagating from an annular shock tube into a cylindrical chamber was investigated
numerically with the dispersion controlled dissipation (DCD) scheme. The first case for an incident Mach number of 1.5 was
conducted and compared with experiments for validation. Then, several cases were calculated for higher incident Mach numbers
varying from 2.0 to 5.0, and complicated flow structures were observed. The numerical study was mainly focused on two aspects:
focusing process and flow structures. The process, including diffraction, focusing, and reflection, is displayed to reveal
the focusing mechanism, and the flow structures at different incident. Mach numbers are used to demonstrate shock reflection
styles and focusing characteristics.
PACS 47.40.Ki; 47.40.Nm; 52.35.Tc 相似文献
8.
本文在自行研制的无膜激波管中,实验研究了不同快速卸压装置对该激波管运行特性的影响。通过控制高压段充气压力和测量压力波形,得到了高低压段压比和激波马赫数的关系曲线以及在测压点处形成激波所需的最低压比。实验结果表明排气快慢对激波形成距离和所形成激波的强度产生很大的影响。对不同装置产生的结果差异进行了一定的分析。 相似文献
9.
The high-speed combustible gas ignited by a hot gas jet, which is induced by shock focusing, was experimentally investigated. By use of the separation mode of shock tube, the test section of a single shock tube is split into two parts, which provide the high-speed flow of combustible gas and pilot flame of hot gas jet, respectively. In the interface of two parts of test sections the flame of jet was formed and spread to the high-speed combustible gas. Two kinds of the ignitions, 3-D “line-flame ignition” and 2-D “plane-flame ignition”, were investigated. In the condition of 3-D “line-flame ignition” of combustion, thicker hot gas jet than pure air jet, was observed in schlieren photos. In the condition of 2-D “plane-flame ignition” of combustion, the delay time of ignition and the angle of flame front in schlieren photos were measured, from which the velocity of flame propagation in the high-speed combustible gas is estimated in the range of 30–90m/s and the delay time of ignition is estimated in the range of 0.12–0.29ms.
PACS 47.40.Nm; 82.40.FpPart of this paper was presented at the 5th International Workshop on Shock/Vortex Interaction, Kaohsiung, October 27–31, 2003. 相似文献
10.
11.
Shi Honghui Kazuhiko Kawai Motoyuki Itoh Yu Hongru Jiang Zonglin 《Acta Mechanica Sinica》2002,18(3):288-301
An experimental study and a numerical simulation were conducted to investigate the mechanical and thermodynamic processes
involved in the interaction between shock waves and low density foam. The experiment was done in a stainless shock tube (80
mm in inner diameter, 10 mm in wall thickness and 5 360 mm in length). The velocities of the incident and reflected compression
waves in the foam were measured by using piezo-ceramic pressure sensors. The end-wall peak pressure behind the reflected wave
in the foam was measured by using a crystal piezoelectric sensor. It is suggested that the high end-wall pressure may be caused
by a rapid contact between the foam and the end-wall surface. Both open-cell and closed-cell foams with different length and
density were tested. Through comparing the numerical and experimental end-wall pressure, the permeability coefficients α and
β are quantitatively determined. 相似文献
12.
A high pressure pulse, which was produced by a shock tube, was hit repeatedly on a pellet of mouse EL-4 T-lymphoma cells packed
in a small test tube which was filled up with culture medium. The pressure pulse measured at the conical bottom of the tube
had about 30 μs width and up to 8.4 MPa height depending on the driver gas pressure of the shock tube. The lymphoma cells
began to be destroyed by hitting with 100 pulses having a peak pressure around 3 MPa. The fraction of dead cells in the tube
exposed to the shock wave of 100 pulses rose exponentially as the peak pressure was increased from 3 MPa to 8 MPa. The fraction
of dead cells at 6.0 MPa of the peak pressure was around 10%. However, proliferative function of the cells survived after
exposure to 6.0 MPa-peak-pressure pulses seemed intact because the cells which survived the exposure proliferated as well
as the nonexposed control cells. 相似文献
13.
Wu Qingsong 《Acta Mechanica Sinica》1988,4(3):239-247
In this paper, the random choice method (RCM) with an operator-splitting technique is applied to the numerical simulation
of shock propagation down a tube of changing area with a nonuniform steady flow and the flow properties behind the shock.
The change rules of the shock strength and flow properties behind it are obtained, and the results are analysed. 相似文献
14.
15.
基于二维Euler方程,结合五阶加权基本无振荡(weighted essentially nonoscillatory,WENO)格式以及自适应网格加密(adaptive mesh refinement,AMR)技术对入射激波在矩形凹槽管道内传播过程进行了数值模拟。数值结果清晰地显示了入射激波传播过程中与多个矩形凹槽作用以及在凹槽内变化的整个过程,且与已有的实验结果吻合较好。另外,结果还揭示了入射激波与单个凹槽作用时,会发生绕射产生膨胀波,还会发生碰撞从而诱导反射激波。膨胀波会导致入射激波压力降低,而反射激波则导致其升高,但膨胀波的影响占主导作用,因而入射激波波阵面强度出现振荡下降。 相似文献
16.
This paper presents the electromagnetic wave propagation characteristics in plasma and the attenuation coefficients of the microwave in terms of the parameters he, v, w, L, wb. The φ800 mm high temperature shock tube has been used to produce a uniform plasma. In order to get the attenuation of the electromagnetic wave through the plasma behind a shock wave, the microwave transmission has been used to measure the relative change of the wave power. The working frequency is f = (2-35)GHz (ω=2πf, wave length A =15cm-8mm). The electron density in the plasma is ne = (3×10^10-1×10^14) cm^-3. The collision frequency v = (1×10^8-6×10^10) Hz. The thickness of the plasma layer L = (2-80)cm. The electron circular frequency ωb=eBo/me, magnetic flux density B0 = (0-0.84)T. The experimental results show that when the plasma layer is thick (such as L/λ≥10), the correlation between the attenuation coefficients of the electromagnetic waves and the parameters ne,v,ω, L determined from the measurements are in good agreement with the theoretical predictions of electromagnetic wave propagations in the uniform infinite plasma. When the plasma layer is thin (such as when both L and A are of the same order), the theoretical results are only in a qualitative agreement with the experimental observations in the present parameter range, but the formula of the electromagnetic wave propagation theory in an uniform infinite plasma can not be used for quantitative computations of the correlation between the attenuation coefficients and the parameters ne,v,ω, L. In fact, if ω<ωp, v^2<<ω^2, the power attenuations K of the electromagnetic waves obtained from the measurements in the thin-layer plasma are much smaller than those of the theoretical predictions. On the other hand, if ω>ωp, v^2<<ω^2 (just v≈f), the measurements are much larger than the theoretical results. Also, we have measured the electromagnetic wave power attenuation value under the magnetic field and without a magnetic field. The result indicates that the value measured under the magnetic field shows a distinct improvement. 相似文献
17.
Abstract. A new large cross-section shock tube has been developed in order to investigate different stages of the development of the
Richtmyer-Meshkov instability and the instability-induced turbulent mixing. The main benefits of such a facility are that
it allows, first, to create a free turbulent mixing with the knowledge of its initial conditions and, second, to follow different
transition phases from the beginning to the fully developed turbulent stage.
Received 10 May 2002 / Accepted 20 July 2002 Published online 4 February 2003
Correspondence to: L. Houas (e-mail: Lazhar.Houas@polytech.univ-mrs.fr) 相似文献
18.
Xu Fu 《Acta Mechanica Sinica》1987,3(2):113-122
The stability of shock wave based on the definition of Landau and Lifschitz[1] is treated in this paper. This is tantamount to solving the problem of interaction of small disturbances with a shock wave.
Small disturbances are introduced on both sides of a steady, non-dissipative, plane shock wave. Landau et al.[1] obtained the stability criterionM
1>1,M
2<1 for small disturbances which are travelling in the direction perpendicular to the shock wave. In the present paper, we
assume that the small disturbances may be two dimensional, i.e. they may be propagating in the direction inclined to the shock
wave. The conclusions obtained are: regardless of whether the incident wave and diverging wave are defined according to the
direction of the phase velocity or the group velocity, the shock wave is unstable for some frequencies and longitudinal wave
lengths of the disturbances, even if the conditionsM
1>1,M
2<1 are fulfilled. Then several experiments are proposed, and the problem of ways to define the incident wave and diverging
wave is discussed. The meaning of this problem is illustrated.
The same results can be obtained for the steady shock wave in a tube. 相似文献
19.
G. Jourdan L. Schwaederlé L. Houas J.-F. Haas A.N. Aleshin S.V. Sergeev S.G. Zaytsev 《Shock Waves》2001,11(3):189-197
A constant temperature hot-wire anemometry method is applied to the study of mixing zones induced by the interaction of a
shock wave with Mach number 1.25 in air with air/helium (heavy/light), air/argon or air/krypton (light/heavy) initially plane
interfaces. The single wire gauge is positioned at various locations along the shock tube axis. At the present stage of our
investigation, although the analysis of the hot-wire signal is not achieved yet, we report the interesting concept of using
hot-wire anemometry as a diagnostic method for shock tube studies of the Richtmyer-Meshkov instability. Based on this preliminary
work, we discuss prospective experimental signal conversion, in order to provide some new results for this field of investigation,
in particular for resolving characteristics of the turbulent mixing zone which is of most interest.
Received 3 August 2000 / Accepted 15 February 2001 相似文献