共查询到20条相似文献,搜索用时 31 毫秒
1.
Formation of transverse waves in oblique detonations 总被引:1,自引:0,他引:1
Jimmy Verreault Andrew J. Higgins Robert A. Stowe 《Proceedings of the Combustion Institute》2013,34(2):1913-1920
The structure of oblique detonation waves stabilized on a hypersonic wedge in mixtures characterized by a large activation energy is investigated via steady method of characteristics (MoC) calculations and unsteady computational flowfield simulations. The steady MoC solutions show that, after the transition from shock-induced combustion to an overdriven oblique detonation, the shock and reaction complex exhibit a spatial oscillation. The degree of overdrive required to suppress this oscillation was found to be nearly equal to the overdrive required to force a one-dimensional piston-driven detonation to be stable, demonstrating the equivalence of two-dimensional steady oblique detonations and one-dimensional unsteady detonations. Full unsteady computational simulations of the flowfield using an adaptive refinement scheme showed that these spatial oscillations are transient in nature, evolving in time into transverse waves on the leading shock front. The formation of left-running transverse waves (facing upstream) precedes the formation of right-running transverse waves (facing downstream). Both sets of waves are convected downstream away from the wedge in the supersonic flow behind the leading oblique front, such that the mechanism of instability must continuously generate new transverse waves from an initially uniform flow. Together, these waves define a cellular structure that is qualitatively similar to a normal propagating detonation. 相似文献
2.
解有激波的气体力学问题的数值解法,主要有特征线法和有限差分法两类。特征线法一般能给出高的精度,但当激波很弱、与特征线几乎平行时就需特殊处理[1]。有限差分法的研究和发展更广,有人工粘性法[2]、激波捕捉法[8]、分离奇性法[1]等处理激波的方案,它们又各有其特殊的技巧和问题。 相似文献
3.
使用计算流体动力学的方法,对经典的运动激波绕射现象做数值模拟,研究了一类复杂激波反射问题一入射的运动斜激波绕射现象.给出一组运动斜激波绕射波纹壁面的非定常过程的模拟结果。计算结果显示出由运动斜激波绕射诱导的多波干扰产生的复杂流场结构。 相似文献
4.
Effect of solid dust particles on the propagation of shock wave in planar and non-planar gasdynamics
The aim of the present study is to analyze the propagation of shock wave along the characteristic path in planar and non-planar unsteady compressible ideal gas flow in presence of small solid dust particles. The analytical solution of the governing quasilinear hyperbolic system is computed in the characteristic plane and it is found that this analytical linear solution in this plane can exhibit non-linear phenomenon in the physical plane. The effect of the dust particles on the evolutionary behavior of the propagating shock wave in ideal gas flow is discussed. The transport equations leading to the evolution of shock wave is determined which introduces the conditions of shock formation. The growth and decay of compressive waves and expansive waves, respectively, in planar and non-planar ideal gas dynamics influenced by the presence of small solid dust particles, is discussed. 相似文献
5.
The presence of an adverse pressure gradient, shock/shock interaction and shock wave/boundary layer interaction often induces
flow separation around bodies. However, the effect of dissociated flow on separated flow characteristics, especially at hypersonic
speeds, is still not clear, and considerable differences are observed between experiments and numerical simulations. In this
investigation, the unsteady separated flow features around double cones are visualized in the Shock Wave Research Center (SWRC)
free-piston driven shock tunnel at a nominal Mach Number of 6.99 using multiple optical techniques. The time resolved shock
structure oscillations in the flow field around double cones (first cone, semi-apex angle = 25°; second cone, semi-apex angles=50°,
65°, 68° and 70°) have been visualized using a high-speed image converter camera (IMACON) at a nominal stagnation enthalpy
of 4.8 MJ/kg. In addition, flow visualization studies around the double cone is also carried out using Schlieren and double
exposure holographic interferometry in order to precisely locate the separation point and measure the separation length. The
presence of a triple shock structure in front of the second cone and a non-linear unsteady shock structure oscillation in
the flow field are the significant results from visualization studies on the 25° /65°, 25° /68° and 25°/70° double cones.
On the other hand, the flow field around 25° /50° is relatively steady and Type V shock/shock interaction is observed. Illustrative
numerical simulation studies are carried out by solving N-S equations to complement the experiments. The simulated flow features
around a double cone agree well qualitatively with experiments. 相似文献
6.
A. N. Golubiatnikov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(1):116-120
A method for specifying a class of potential flows of inhomogeneous continuous media is developed. The general approach is
based on expanding a medium material symmetry group to a special volume-preserving group, allowing us to obtain a law for
the conservation of vorticity and, when there is no vorticity, to derive the unsteady Bernoulli equation. As illustrations,
plane steady stationary flows of an inhomogeneous incompressible fluid and variable-entropy gas are considered. The problem
of an inhomogeneous gas flow around a wedge yielding the formation of a shock wave is solved. 相似文献
7.
8.
准确地给出激波位置信息对于激波装配极为重要.但是,在使用计算流体力学(computational fluid dyna-mics,CFD)方法模拟复杂流动时很难准确地给出激波的位置.根据激波捕捉得到的流场信息确定的激波位置往往带有极大误差,在定常问题的模拟中,这种误差可以随着迭代逐渐消除,然而在非定常问题的模拟中,这种误差往往会积累甚至导致计算崩溃.文章将基于特征线理论的激波辨识技术应用到激波装配中,根据已有流场信息准确判断激波的位置.对于定常问题,该方法的应用加速了收敛速度;对于非定常问题,该方法的应用可以极大地避免初始误差的产生. 相似文献
9.
跨音压气机转子叶尖间隙复杂流动观测 总被引:8,自引:1,他引:7
本文利用高频响动态压力传感器,在文献[1]的基础上,对WP11压气机转子叶尖间隙 流场进行了流场测量。测试包括三个转速多个节流条件下的间隙流场。测试结果表明:激波总体位 置随节流加深而向上游移动,但吸力面最小压力点基本维持在40%或20%弦长处不变。当激波位 置在该点之后时,二次漏流直接冲击激波结构;当激波位置在该点之前时,激波结构基本只受前缘 漏流的影响。 相似文献
10.
使用非定常无反射边界条件模拟上游尾迹/叶片排干扰问题 总被引:1,自引:1,他引:0
本文采用显式时间推进方法求解二维Euler方程计算了上游尾迹与下游叶片排相互干扰而形成的复杂流场。根据Giles提出的理论编制了无反射边界条件非定常计算程序,取得了满意的效果。进口上游尾迹的特性白尾迹模型给定.预测到了尾迹在叶栅流道内的切割,迁移及剪切等重要的非定常现象。 相似文献
11.
完全气体一元变截面不定常带激波流动的一套显式解析解 总被引:1,自引:0,他引:1
本文绘出了可压缩完全气体一元变截面不定常带撤波流动的一套代数显式解析解。据作者所知此解是不定常带激波流的第一个显式解析解。此解除在理论上有其重要意义外,还可以用来作为检验各种数值解及研究各种数值解法之用,也有重大实用价值。 相似文献
12.
Journal of Visualization - The unsteady flow structures and pressure fluctuations of the cylinder-induced shock wave/boundary layer interactions (SBLIs) were investigated at Mach 3.4 and 3.8. The... 相似文献
13.
本文求解了二维不定常磁流体力学方程组,从而讨论星系磁场和星系激波的起源和演化过程。初始均匀的磁场将缠卷而在星系盘中形成螺旋形的结构,其中磁场和星际气体是冻结在一起的。分析了星际磁场对形成星系激波的影响。由于磁场不是很强,它对星系激波的影响不是非常强。 相似文献
14.
The results of an experimental study of the impact of the focused pulsed-periodic radiation from a CO2 laser on a gas-dynamic structure in a supersonic jet are presented. The radiation of the CO2 laser is propagated across the stream and focused by a lens on the axis of the supersonic jet. To register the flow structure, a shadow scheme with a slit and a flat knife located along the flow is used. The image is fixed by a speed camera with an exposure time of 1.5 μs and a frame rate of 1000 1/s. In the flow, the plasma initiated by the pulsedperiodic laser is visualized in order to identify and determine the period of plasma development, as well as the motion of the initial front of the shock wave. It is shown that at the transverse input of laser radiation into the stream the periodic structure of the thermal trace is created with the formation of an unsteady shock wave from the energy release zone. At small repetition rates of laser radiation pulses, the thermal spot interacts with the flow in the pulsed mode. It is shown that elliptic nonstationary shock waves are formed only at low subsonic flow velocities and in a stationary atmosphere. The process of nonstationary ignition by an optical discharge of a methane–air mixture during a subsonic outflow into a motionless atmosphere is shown experimentally. The results of optical visualization indicate burning in the trace behind the optical discharge region. 相似文献
15.
16.
17.
18.
Yancheng You Heinrich Luedeke Klaus Hannemann 《Proceedings of the Combustion Institute》2013,34(2):2083-2092
The low momentum flux ratio jet in the HyShot II scramjet combustor is studied by DES (Detached Eddy Simulation) and RANS (Reynolds-Averaged Navier–Stokes) methods. The flow structure near the injector, shock pattern in the symmetry plane as well as the instantaneous coherent structures are presented and explained. Further insight into the flow physics is obtained by visualizing instantaneous coherent structures. The formation of Ω-shaped vortices, which was previously observed in experiments but never well-studied numerically, is discussed in detail. A new schematic of flow physics is proposed to enhance the understanding of the low momentum flux ratio jet. Compared to the DES result, the RANS method is unable to capture the dynamics of turbulent structures. The DES method provides much detailed information about mixing patterns and a more reliable mixing efficiency than the RANS result. The RANS method over-predicts the eddy-viscosity during turbulence modeling and suppresses unsteady turbulent fluctuations by time averaging, which results in a 25% over-estimation of the mixing efficiency. 相似文献
19.
超/高超声速尾退分离在防热、保形、隐身、多次投放、回收等方面具有明显优势,有望成为高超声速飞行器载荷投放的优选方案。由此面临一类新的多体分离问题:超/高超声速尾退分离问题(aft super/hypersonic ejection separation, ASES)。超/高超声速尾退分离问题本质上是带空腔底部流动与多体分离构成的耦合问题,具有流场结构复杂、气动非定常非线性非对称效应显著的特点。针对超声速尾退分离问题,采用网格测力和轨迹捕获(captive trajectory system, CTS)风洞试验方法探索了尾退分离干扰流场的结构,发现可根据流场结构和舵效变化分为低速-亚声速无激波、高亚声速-跨声速弱激波、超声速激波和准自由流弱干扰4种典型干扰特征,揭示了尾流场影响后不同区域的全弹气动特性和舵效特性以及控制律、攻角、高度和Mach数对分离位移和姿态的影响规律。相关结论将有助于增强对尾退分离问题的认识,对尾退分离技术的工程实践具有参考价值。 相似文献
20.
S. M. Aulchenko V. P. Zamuraev I. A. Znamenskaya A. P. Kalinina D. M. Orlov N. N. Sysoev 《Technical Physics》2009,54(3):343-353
A way of effectively affecting the gasdynamic structures of a transonic flow over a surface by means of instantaneous local
directed energy deposition into a near-surface layer is proposed. Experimental investigations into the influence of a pulsed
high-current nanosecond surface discharge of the “plasma sheet” type on gas fast flow with a shock wave near the surface are
carried out. The self-localization of energy deposition into a low-pressure region in front of the shock wave is described.
Based on this effect, a facility for automated energy deposition into a dynamic region bounded by the moving shock front can
be designed. The limiting value of the specific energy deposition on the surface in front of the shock wave is found. With
the help of the direct-shadow method, an unsteady quasi-two-dimensional discontinuous flow arising when a plasma sheet is
initiated on the wall in a flow with a plane shock wave is studied. By numerically solving the two-dimensional nonstationary
equations of gas dynamics, the influence of the energy of a pulsed nanosecond discharge, which is applied in the frequency
regime, on the aerodynamic characteristics of a high-lift profile is investigated. It is ascertained that the energy delivered
to the gas before the closing shock wave in a local supersonic region that is located in the neighborhood of the profile contour
in zones extended along the profile considerably decreases the wave drag of the profile. 相似文献