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91.
Oscillatory flows of a choked underexpanded supersonic impinging jet issuing from a convergent nozzle have been computed using
the axisymmetric unsteady Navier--Stokes system. This paper focuses on the oscillatory flow features associated with the variation
of the nozzle-to-plate distance and nozzle pressure ratio. Frequencies of the surface pressure oscillation and flow structural
changes from computational results have been analyzed. Staging behavior of the oscillation frequency has been observed for
both cases of nozzle-to-plate distance variation and pressure ratio variation. However, the staging behavior for each case
exhibits different features. These two distinct staging behaviors of the oscillation frequency are found to correlate well
if the frequency and the distance are normalized by the length of the shock cell. It is further found that the staging behavior
is strongly correlated with the change of the pressure wave pattern in the jet shear layer, but not with the shock cell structure.
Communicated by K. Takayama
PACS 02.60.Cb; 47.40.−x; 47.40.Nm; 47.35.+I; 47.15.−x 相似文献
92.
Some experiments were made for the buoyant jet from a square orifice with a square disc placed on it in static ambient and concentration along the axis in self-similar area behind disc was measured. And at the same time a three-dimensional mathematical model was established to simulate the whole flowing under different conditions. All the results predicted by the numerical calculation were substantiated by the experiments. The results were compared with experiential formula for obstructed round buoyant vertical jets in static ambient and it was found that the two concentration distributions had good accordance. Star shape of temperature isolines on cross-sections in the near areas from the disc was found and it was a very special figure for obstructed square buoyant vertical jets with a square disc. The shape will transform to concentric circles gradually alike to the round buoyant vertical jet in self-similar area with increasing of the distance from the disc. 相似文献
93.
Axisymmetric impingement of a hot jet on a flat plate: equilibrium flow analysis of high-temperature air 总被引:1,自引:0,他引:1
The flow structure of an underexpanded supersonic jet with high reservoir temperature impinging on a flat plate has been numerically investigated using a Total Variation Diminishing (TVD) scheme. When the temperature of the flow field is high enough to cause chemical reaction, the specific heat ratio,, is no longer equal to 1.4, nor constant. This explains the difference found in the literature between the flow properties of the calorically perfect gas and that of the chemically reacting flow. Under the equilibrium flow assumption the effect of high temperature gas on the impinging jet has been taken into account in the present paper by using specific heat ratio and speed of sound given by correlation polynomials of thermodynamic variables. The limiting case of cold jet calculation in the present numerical results agreed well with the existing experimental data. For the equilibrium jet with high reservoir temperature,T
o=1000K, qualitative support of the present result has been provided by means of the approximation theory.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
94.
G. P. Romano 《Applied Scientific Research》1996,56(2-3):209-220
The near flow field of an axisymmetric water jet at Reynolds numbers between 2000 and 5000 is investigated using Particle-Tracking Velocimetry. Measurements are taken in the longitudinal section (along the mean flow) and in cross-sections (orthogonal to the mean flow). From the former, correlation coefficients of the two in-plane velocity components in a Lagrangian framework are obtained: thus Lagrangian integral scales can be computed. Those of the streamwise velocity (axial) component increase on moving away from the centreline, whereas the opposite happens for the vertical velocity (radial) component: integral time scales of the two components are almost equal at the interface between jet and ambient fluids. On the other hand, integral scales are almost constant or increase slightly with the axial direction. In cross-sections, fluid ejection and injection from the jet centreline are observed to be connected to counter-rotating vortices (mushroom): their number and size change with Reynolds number in agreement with results from other authors. The maximum ejection velocity (orthogonal to the mean jet flow), at 3 nozzle diameters downstream of the outlet, is found to be one half of the mean outlet velocity. 相似文献
95.
The quasi-parallel regime of a Darcy–Boussinesq boundary-layer flow over a permeable vertical flat plate adjacent to a fluid saturated porous medium is considered. Quasi-parallel means here a plane flow with a constant transversal velocity v=–v
0 directed perpendicularly towards the vertical surface, where a lateral suction with the same velocity –v
0 is applied. The plate is held at a constant temperature T
w which coincides with the ambient temperature T
of the fluid. The heat released by viscous dissipation induces a density gradient in the fluid. Thus, although T
w=T
, a thermal convection occurs. The steady regime of this self-sustaining buoyant flow has been examined in detail. Wall jet-like profiles with a continuous but finite spectrum of the momentum flow have been found. These self-sustaining buoyant jets show a universal behavior, that is, there exist certain length, velocity and temperature scales such that the flow characteristics become independent of the (constant) material properties of the fluid and the porous medium as well. 相似文献
96.
本文介绍了对特定条件下的闪光X射线摄影技术所作的改造及其在聚能装药等爆轰实验中拍摄2m幅长的X射线照片的应用情况。 相似文献
97.
98.
聚能射流侵彻的一种耦合算法 总被引:3,自引:0,他引:3
介绍了一种能有效模拟聚能射流侵彻过程的计算方法,即二维数值解和解析解相耦合的方法。实际应用表明,此方法计算结果准确可靠,经济省时,其软件是聚能装药优化设计的实用工具。 相似文献
99.
Xin-Zhuang Wu Jun-Jie Yan Shu-Feng Shao Yan Cao Ji-Ping Liu 《International Journal of Multiphase Flow》2007,33(12):1296-1307
The condensation of supersonic steam jet submerged in the quiescent subcooled water was investigated experimentally. The results indicated that the shape of steam plume was controlled by the steam exit pressure and water temperature. Six different shapes of steam plume were observed under the present test conditions. Their distribution as a function of the steam exit pressures and water temperatures was given. As the steam mass velocity and water temperature increase, the measured maximum expansion ratio and dimensionless penetration length of steam plume were in the ranges of 1.08–1.95 and 3.05–13.15, respectively. The average heat transfer coefficient of supersonic steam jet condensation was found to be in the range of 0.63–3.44 MW/m2K. An analytical model of steam plume was found and the correlations to predict the maximum expansion ratio, dimensionless penetration length and average heat transfer coefficient were also investigated. 相似文献
100.
The present work is devoted to the experimental and numerical study ofthe interaction of a turbulent plane jet with a rectangular cavity.Several flow regimes have been found to occur: the non-oscillationregime, the stable oscillation regime and an unstable oscillationregime. The first two regimes have been particularly considered. Theexperimental study has been carried out using hot wire anemometry andsome visualisations. The numerical predictions based on statisticalmodelling have been made using on the one hand the standard k– model and on the other hand a two-scales split spectrum model. The structuralproperties of the flow have been described for the different situations.For the oscillatory regime, a parametrical study allowed to determinethe influence of the jet exit location and the Reynolds number on thefrequency of the jet flapping. The one point closures have been able topredict the oscillatory regime, and in particular the two-scales modelled to improved results because better account is taken of lag effectsin unsteady non-equilibrium situations. 相似文献