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71.
J. I. Ramos 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(8):548-563
Summary The nonlinear dynamics of axisymmetric, inviscid, incompressible, thin, annular liquid jets subjected to fluctuating body forces is studied numerically by means of an adaptive finite difference method which maps the time-dependent, curvilinear geometry of the jet into a unit square. The fluctuating body forces may arise from fluctuations in the gravitational acceleration in inertial frames or from the acceleration of a non-inertial frame of reference which translates parallelly to an inertial one. It is shown that both the pressure coefficient and the axial location at which the annular jet becomes a solid one are periodic functions of time with a period equal to that of the imposed body force fluctuations, and that their magnitude increases as the amplitude of the body force fluctuations is increased. It has also been shown that, for both intermittent, sinusoidal or rectangular excitations, increases in the frequency of the excitation result in the creation of superharmonics, broad, albeit peaked, spectra, and closed phase planes with many loops.The research reported in this paper was supported by Project PB91-0767 from the D.G.I.C.Y.T. of Spain. 相似文献
72.
Yue-Tzu Yang 《国际流体数值方法杂志》1995,20(7):641-648
The paper presents numerical predictions of a turbulent axisymmetric jet impinging onto a porous plate, based on a finite volume method of solving the Navier-Stokes equations for an incompressible air jet with the K–ε turbulence model. The velocity and pressure terms of the momentum equations are solved by the SIMPLE (semi-implicit method for pressure-linked equation) method. In this study, non-uniform staggered grids are used. The parameters of interest include the nozzle-to-wall distance and the suction velocity. The results of the present calculations are compared with available data reported in the literature. It is found that suction effects reduce the boundary layer thickness and increase the velocity gradient near the wall. 相似文献
73.
Jet quenching has successfully served as a hard probe to study the properties of Quark-Gluon Plasma (QGP). As a multi-particle system, jets require time to develop from a highly virtual parton to a group of partons close to mass shells. In this study, we present a systematical analysis on the effects of this formation time on jet quenching in relativistic nuclear collisions. Jets from initial hard scatterings were simulated with Pythia, and their interactions with QGP were described using a Linear Boltzmann Transport (LBT) model that incorporates both elastic and inelastic scatterings between jet partons and the thermal medium. Three different estimations of the jet formation time were implemented and compared, including instantaneous formation, formation from single splitting, and formation from sequential splittings, before which no jet-medium interaction was assumed. We found that deferring the jet-medium interaction with a longer formation time not only affects the overall magnitude of the nuclear modification factor of jets but also its dependence on the jet transverse momentum. 相似文献
74.
线型聚能装药的理论研究 总被引:11,自引:0,他引:11
本文提出了一端起爆的线型聚能装药射流形成的不定常理论模型。根据这一模型,当金属罩在爆轰波作用下的运动速度为已知时,则不论此速度是否是时间或初始位置的函数,都能得到射流形成时的速度,质量和位置等参数。 按照本文模型,Defourneaux.M.的定常射流形成定常模型是一个简单的特例。我们利用本文的模型对等厚度装药的情况进行了计算,并与实验结果比较,两者符合良好。同时计算结果表明,考虑射流形成的不定常因素,可以较好地解释射流头部的质量堆积和射流内部的反向速度梯度等实验现象。本文的模型可以为线型聚能切割索的设计提供较为准确的理论指导。 相似文献
75.
高速液体受限射流扩展形态研究 总被引:4,自引:0,他引:4
采用一种火药燃烧驱动液体喷射的新装置及其测试系统,研究受限空间中高速惰性液体射流的扩展结构。观察了环境反压、液体粘性、喷嘴结构等参量对射流扩展形态的影响,分析了射流雾化机理。研究结果对改进燃烧室设计及控制燃烧稳定性有一定的指导意义。 相似文献
76.
Details from cavitation bubble dynamics are reported: jet formation, counterjet formation, shock wave radiation and light emission. Multiple shock wave radiation from single bubble collapse with jet formation could be time resolved by high speed photography with 20 million frames per second. An explanation of counterjet formation is given. Pictures of the light emission (sonoluminescence) in acoustic cavitation are presented. 相似文献
77.
78.
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
79.
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
80.
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