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1.
水下超音速气体射流胀鼓和回击的关联性研究   总被引:6,自引:0,他引:6  
阐述了水下超音速气体射流的实验研究结果.用高速摄影仪实时记录了水下超音速气体射流喷射的状态,清晰地演示了射流气体在上中游流域的演化过程.具体分析了水下高速气体射流的动态不稳定性形貌,并从实时记录的射流照片中统计测量出了胀鼓和回击随机频率.结果发现,胀鼓频率越大,回击频率越大;胀鼓频率随着喷嘴的驻室压力与出口背压的比值增大而增大.通过胀鼓与回击事件前后实验数据的对比分析表明其二者之间存在相关性:胀鼓和回击均由射流内部压力振荡引发并且存在一定的随机性;胀鼓是回击前的能量积聚一个前征和表现,当胀鼓的振荡即能量积聚到一定程度后,引发回击.  相似文献   

2.
一种超声速气动发电机实验装置及实验技术研究   总被引:1,自引:1,他引:0  
陈志敏  于昆龙 《实验力学》2004,19(3):386-390
在对超声速榴弹炮以及导弹引信供电系统的发电机研究中,过去常在闭口式风洞进行实验,但由于闭口式风洞中各种相似参数和特有的因素影响,使得实验数据与真实飞行数据完全不符。因此,多年来只得靠实弹打靶来完善设计方案。本文利用气体动力学和实验空气动力学理论,设计了一种适合气动发电机的超声速试验射流装置,并通过试验详细地研究了装置在出口的流场品质和不同几何外形气动发电机的转速特性,给出了合理的模型试验区、喷管出口流速的确定方法和射流实验区参考压力的选取方法,最后对模型实验结果与打靶遥测数据进行了对照。研究表明,利用超声速射流的工作原理进行导弹引信发电机的模拟实验是可行的,并且该装置可用于引信产品验收。  相似文献   

3.
将Hartmann-Sprenger(H-S)管集成到传统射流装置中形成激励射流,研究其在超声速流场中的混合特性.设计了3种频率的CO_2激励射流,将其横向注入Ma=2.5的均匀超声速来流当中.采用平面激光散射技术对其进行瞬态可视化成像,利用组分采样进行时均分析.结果表明:H-S激励射流可以有效提高射流穿透深度,形成较多大尺度结构,从而获得较好的混合效果.  相似文献   

4.
对充液腔体中气体射流的冲击效应进行了实验研究. 测量结果表明了冲击压力的瞬态最 大值、稳态平均值和脉动值随喷管进口压比的增加而增加,冲击区是主要的噪声源和动态压 力承载部位. 通过充气与充水两种状态的对比实验,还揭示了腔体充水时气体射流冲击压力 出现一个上冲阶段,其瞬态最大值比充气值有显著的增加.  相似文献   

5.
针对具有不同类型喷管的爆轰管在水下爆轰中形成的燃气射流问题,搭建了爆轰实验平台,研究了单次爆轰过程中尾部喷管对水下气泡形态与压力特征的影响。采用数字粒子图像测速技术对高速摄影机拍摄得到的气泡脉动图片进行流场可视化分析,得到各喷管工况下的气泡速度场。为了确认爆轰管内是否形成稳定爆轰波,并观察爆轰波在气液两相界面上的透反射特性,爆轰管尾部安装有2个动态压力传感器,同时在距离喷管一定距离处设置一个水下爆炸传感器,以监测水中传播的压力波。结果表明:扩张喷管工况下的气泡脉动过程与直喷管工况基本一致,但扩张喷管提高了燃气射流速度,气泡膨胀体积更大;因为燃气射流的持续性,收敛喷管工况下的气泡脉动过程具有明显差异,气泡膨胀体积较小,但气泡二次脉动时长相较于一次脉动时长衰减更小;扩张喷管提高了气泡脉动强度,扩张喷管工况下的气泡脉动压力与透射冲击波压力远大于直喷管工况下的气泡脉动压力与透射冲击波压力;收敛喷管工况下的气泡脉动压力与透射冲击波压力都较小,但收敛喷管燃气射流的持续性减缓了气泡脉动压力的衰减速度。相比于直喷管,扩张喷管工况下的气泡脉动时间、气泡脉动压力与透射冲击波压力都更大。收敛喷管工况下的气泡...  相似文献   

6.
固体火箭燃气射流驱动液柱过程的CFD分析   总被引:1,自引:0,他引:1  
王健  阮文俊  王浩  张磊 《爆炸与冲击》2017,37(2):186-193
固体火箭燃气射流驱动液柱过程会产生一个复杂的非稳态多相流场,为了研究液柱对固体火箭发动机工作过程中射流流场的降温效果,并揭示燃气冲击液柱的流动演化和气水之间的相互作用,利用FLUENT软件中耦合了液态水汽化方程的VOF多相流计算模型对燃气与液柱之间的耦合流动及相变过程进行了数值模拟,并与无液柱情况下射流流场的计算结果进行了对比分析。计算结果表明,当有液柱平衡体时射流流场中的压力、温度、速度波动幅度均减小,减弱了射流流场中的湍流脉动强度;液柱与燃气之间的汽化以及液柱的阻碍作用减小了射流流场的轴向发展位移,尾管后的完全发展射流流场核心区域内的压力峰值降低了0.9 MPa,温度峰值降低了503 K,速度峰值降低了291 m/s,验证了实验中液柱对燃气射流流场的降温效果。  相似文献   

7.
Hartmann-Sprenger(H-S)管处于吞吐模式下可以产生高频高幅度的气流振荡。本文将H-S管集成到传统射流装置中形成激励射流,研究其在超声速流场中的混合特性。本文设计了三种频率的CO2激励射流,将其横向注入马赫数2.5的均匀超声速来流当中。采用平面激光散射技术对其进行瞬态可视化成像,利用组分采样、测量总压进行时均分析。结果表明:H-S激励射流可以有效提高射流穿透深度,形成较多大尺度结构,从而获得较好的混合效果。关键词: 激励射流 超声速混合 穿透深度 大尺度结构  相似文献   

8.
李帅  彭俊  罗长童  胡宗民 《力学学报》2021,53(12):3284-3297
激波-激波干扰流场预测是超声速乃至高超声速流动中最具挑战性的问题之一. 特别地, 第IV类激波干扰由于其在壁面驻点附近产生极高的热载荷而备受关注. 本文针对圆柱诱导的弓形激波和入射斜激波的干扰问题, 分别基于量热完全气体模型和考虑振动激发的热完全气体模型, 数值求解有黏二维可压缩NS方程, 分析了高温气体效应对激波干扰流场结构, 以及第IV类激波干扰流场状态参数的影响. 接着, 本文基于一种具有广义可分离特性的遗传算法 (多层分块算法), 给出能够预测不同气体模型下第IV类激波干扰流场三波点的坐标位置、超声速射流的几何形状等特征性几何结构的数学模型, 进一步获得高温气体效应对激波干扰类型转变准则影响的定量化评估. 激波干扰类型转变准则面上的多组临界工况的激波干扰流场结构以及壁面压力和壁面热流分布的对比结果表明, 不同气体模型下的激波干扰类型和流场结构差异较为显著, 获得的定量化预测模型对工程中气动热环境的预测具有一定的参考价值.   相似文献   

9.
李帅  张阿漫  韩蕊 《力学学报》2019,51(6):1666-1681
具有脉动特性的气泡(如水下爆炸气泡、螺旋桨空泡和气枪气泡)动力学行为很大程度上取决于其边界条件. 实验已证实,近自由液面气泡在坍塌过程中常常产生背离自由液面的水射流现象,而近刚性边界气泡在坍塌阶段产生朝向壁面的高速水射流,严重威胁水中结构的局部强度. 前人基于 Rayleigh-Plesset 气泡理论和 “Bjerknes” 力来预测气泡射流方向,然而理论方法难以透彻的揭示气泡射流的初生、发展和砰击过程中丰富的力学机理. 本文首先采用水下高压放电技术产生气泡,并通过高速摄影对不同边界条件下气泡的运动特性进行实验研究. 然后,采用边界积分法模拟气泡非球状坍塌过程. 研究表明,边界条件改变了气泡周围的流场压力梯度方向,进而影响气泡射流初生位置;射流在发展阶段,气泡附近流场的局部高压区和射流之间存在“正反馈效应”,从而揭示了气泡射流速度在短时间内即可增加到百米每秒的力学机理. 射流砰击会在流场中造成局部高压区,随着气泡回弹,射流速度和砰击压力逐渐减小. 本文还探讨了无量纲距离参数对气泡运动及射流砰击载荷的影响,旨为近场水下爆炸等相关领域提供参考.   相似文献   

10.
具有脉动特性的气泡(如水下爆炸气泡、螺旋桨空泡和气枪气泡)动力学行为很大程度上取决于其边界条件.实验已证实,近自由液面气泡在坍塌过程中常常产生背离自由液面的水射流现象,而近刚性边界气泡在坍塌阶段产生朝向壁面的高速水射流,严重威胁水中结构的局部强度.前人基于Rayleigh-Plesset气泡理论和"Bjerknes"力来预测气泡射流方向,然而理论方法难以透彻的揭示气泡射流的初生、发展和砰击过程中丰富的力学机理.本文首先采用水下高压放电技术产生气泡,并通过高速摄影对不同边界条件下气泡的运动特性进行实验研究.然后,采用边界积分法模拟气泡非球状坍塌过程.研究表明,边界条件改变了气泡周围的流场压力梯度方向,进而影响气泡射流初生位置;射流在发展阶段,气泡附近流场的局部高压区和射流之间存在"正反馈效应",从而揭示了气泡射流速度在短时间内即可增加到百米每秒的力学机理.射流砰击会在流场中造成局部高压区,随着气泡回弹,射流速度和砰击压力逐渐减小.本文还探讨了无量纲距离参数对气泡运动及射流砰击载荷的影响,旨为近场水下爆炸等相关领域提供参考.  相似文献   

11.
Multiphase flows are ubiquitous in our daily lifeand engineering applications.It is important to investigatethe flow structures to predict their dynamical behaviors effectively.Lagrangian coherent structures(LCS) defined bythe ridges of the finite-time Lyapunov exponent(FTLE) isutilized in this study to elucidate the multiphase interactionsin gaseous jets injected into water and time-dependent turbulent cavitation under the framework of Navier-Stokes flowcomputations.For the gaseous jets injected into water,the highlightedphenomena of the jet transportation can be observed by theLCS method,including expansion,bulge,necking/breaking,and back-attack.Besides,the observation of the LCS revealsthat the back-attack phenomenon arises from the fact that theinjected gas has difficulties to move toward downstream region after the necking/breaking.For the turbulent cavitatingflow,the ridge of the FTLE field can form a LCS to capturethe front and boundary of the re-entraint jet when the adverse pressure gradient is strong enough.It represents a barrier between particles trapped inside the circulation regionand those moving downstream.The results indicate that theFTLE field has the potential to identify the structures of multiphase flows,and the LCS can capture the interface/barrieror the vortex/circulation region.  相似文献   

12.
Gaseous jets injected into water are typically found in underwater propulsion,and the flow is essentially unsteady and turbulent.Additionally,the high water-to-gas density ratio can result in complicated flow structures;hence measuring the flow structures numerically and experimentally remains a challenge.To investigate the performance of the underwater propulsion,this paper uses detailed Navier-Stokes flow computations to elucidate the gas-water interactions under the framework of the volume of fluid(VOF) model.Furthermore,these computations take the fluid compressibility,viscosity,and energy transfer into consideration.This paper compares the numerical results and experimental data,showing that phenomena including expansion,bulge,necking/breaking,and back-attack are highlighted in the jet process.The resulting analysis indicates that the pressure difference on the rear and front surfaces of the propulsion system can generate an additional thrust.The strong and oscillatory thrust of the underwater propulsion system is caused by the intermittent pulses of the back pressure and the nozzle exit pressure.As a result,the total thrust in underwater propulsion is not only determined by the nozzle geometry but also by the flow structures and associated pressure distributions.  相似文献   

13.
为深入研究重气泡内激波聚焦和射流生成的机理,采用高精度计算格式和高网格分辨率对马赫数为1.23的平面入射激波与SF6重气泡的作用过程进行数值模拟,计算结果与文献中实验吻合较好。结果显示:入射激波在重气泡内首先在流向上汇聚形成上、下对称的高压区,随后,这对高压区在SF6重气泡中心对称轴处再次碰撞,完成激波聚焦过程,并在气泡下游界面附近形成远大于初始压力和密度的局部高压高密度区,体现出SF6重气泡极强的聚能效应;激波聚焦还引起气泡下游界面附近的涡量变化,涡对的旋转能够加速射流形成与发展。因此,SF6重气泡下游界面附近的高压区和涡量分布对形成射流结构均有促进作用。  相似文献   

14.
Oscillation flow induced by underwater supersonic gas jets   总被引:1,自引:0,他引:1  
This paper describes an experimental study on the oscillation flow characteristics of submerged supersonic gas jets issued from Laval nozzles. The flow pattern during the jet development and the jet expansion feedback phenomenon are studied using a high-speed camera and a pressure measurement system. The experimental results indicate that along the downstream distance, the jet has three flow regimes: (1) momentum jet; (2) buoyant jet; (3) plume. In the region near the nozzle exit a so-called bulge phenomenon is found. Bulging of the jet occurs many times before the more violent jet expansion feedback occurs. During the feedback process, the jet diameter can become several times that of the original one depending on the jet Mach number. The frequencies of the jet bulging and the jet expansion feedback are measured.  相似文献   

15.
Results are presented of an experimental study of an axisymmetric liquid nitrogen jet propagating at supercritical pressure (real gas) in a medium of gaseous nitrogen, and a comparison is given of the experimental data and results of theoretical calculations.  相似文献   

16.
舒畅  宫兆新  刘桦 《力学季刊》2023,44(1):15-30
认识带尾喷流和自然超空泡的水下高速航行体流体动力特性并发展其预报与控制方法仍是水动力学领域极具挑战性的课题.本研究采用CFD方法对尾喷流和自然超空泡之间的相互作用进行了数值研究.针对发动机欠膨胀超音速喷流,采用现有实验结果验证了基于两方程湍流模型的二维轴对称流动数值模型的可靠性.尾喷流在空气和蒸汽环境中流动的数值计算结果表明,由于蒸汽环境中背压较低,欠膨胀尾喷流无法及时形成压缩波,使得蒸汽环境中尾喷流的过膨胀区和气相扩散区的体积比空气中大;尾喷流很难形成规则的激波格栅,波系结构相对简单.针对携尾喷流的平头航行体超空泡流状态的数值模拟结果表明,尾喷流注入超空泡后迅速充满航行体周围的空腔区域;尾喷流与超空泡尾迹区域形成的回射流相互作用最终导致超空泡断裂,断裂过程中伴随着燃气泡的下泄现象;受空泡壁面约束,尾喷流难以在狭窄的超空泡空腔内完全膨胀,尾喷流的激波波系结构有显著的变化:在喷嘴附近受到压缩,在远离喷嘴区域受到超空泡水汽掺混的破坏;空泡内压强基本维持在饱和蒸汽压附近,没有显著增加.  相似文献   

17.
This paper describes an experimental study of the removal of fine (12 μm) polystyrene particles from a glass substrate, using a gas jet that impinges obliquely onto a particle-laden surface. In order to avoid transient affects associated with jet start-up, the sample was slowly translated under a steady jet. The translating gas jet produces a long, clean path that provides very good statistics for exploring the effect of jet parameters. This study focuses on the dependence of the spatial distribution of removal on the jet pressure ratio and impingement angle. The jet is translated over the sample both longitudinally and transversely to determine both the width and the length of the particle removal footprint. The width of the removal footprint increases and the length decreases as the impingement angle is increased. Previous researchers have reported seemingly contradictory results regarding the dependence of removal efficiency on impingement angle; this paper seeks to resolve these differences. For the steady jet, the threshold jet pressure ratio required for 50% particle removal increases with decreasing impingement angle. In addition, studies of the entrainment of well-characterized particles from well-characterized substrates provide insight into the surface shear stress imposed by the oblique jet. Received: 15 December 1998/Accepted: 15 March 2000  相似文献   

18.
为了解小火箭发射噪声特性及其在喷口外围的声压场分布规律,针对燃气射流产生噪声问题进行了实验研究和数值计算。讨论了超声速射流噪声的3个主要成分(湍流混合噪声、啸音和宽带激波相关噪声)及相关特点,指出它们产生的根本原因是湍流射流的速度扰动。通过分析不同实验测点的射流噪声声压级峰值,得到了燃气射流噪声在轴向和径向上的分布规律,即随着离喷口距离的增大,轴向噪声的衰减程度大于径向。在实验基础上,利用大涡模拟与FW-H(Ffowcs Williams-Hawkings)声学比拟相结合的方法对燃气射流噪声的声学特性进行计算。结果表明,此方法获得的计算结果与实验结果吻合较好,可为进一步研究射流噪声控制提供参考。  相似文献   

19.
 This paper describes an experimental study of the removal of fine (8.3 μm) polystyrene particles from a glass substrate using a gas jet at normal impingement. In order to avoid transient effects associated with jet startup, the sample was slowly translated under a steady jet. The translating gas jet produces a long clean path that provides very good statistics for exploring the effect of jet parameters. The dependence of the spatial distribution of removal efficiency on the jet pressure ratio, the jet height, and the translation speed is examined. Clean paths greater than 16 jet diameters wide are produced with a jet pressure ratio of 7 translating at 9.0 mm/s at a dimensionless height of 10. The path width is independent of the jet height at high pressure ratios and inversely dependent on the jet translation speed. A harmonic oscillator model for particle detachment accounts for the effect of translation speed. Results suggest that the particles act as nearly-quantized shear stress sensors that provide a direct, though as yet uncalibrated, measure of the surface shear stress. Further, knowledge of the pressure required to remove 50% of the particles from the central region of the path is sufficient to predict the extent of particle removal at higher pressures. Received: 30 June 1997/Accepted: 24 June 1998  相似文献   

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