【作者】 金大桥；

【导师】 邹振祝； 王聪；

【作者基本信息】 哈尔滨工业大学 ， 固体力学， 2010， 博士

【摘要】 超空泡减阻技术是实现水下航行体高速航行的新原理和新途径。空泡流动是一种复杂的流动问题,包含了非定常、可压缩、相变、湍动等流体力学研究中比较复杂的流动现象,对空泡流的数值模拟和试验研究都带来了很大的困难。由于水下动能射弹超空泡流动的复杂性,本文采用数值模拟和试验相结合的方法对射弹空泡形态和流体动力特性进行研究,具体研究工作如下:介绍了研究水下动能射弹空泡形态和流体动力特性的数值方法,通过对超空泡流动模拟选用RANS方法中的四种湍流模型对比分析,并与试验结果进行比较,确立了适合数值模拟水下射弹的湍流模型,为后续研究奠定基础。采用上述数值模拟方法对圆柱体自然空泡流体动力特性进行了研究。得到了长细比和空化数以及圆柱体局部结构中头部锥角、倒角、表面凸起、凹槽对空化特性和阻力特性的影响,通过圆柱体射弹试验得到了空泡形态随空化数的变化规律,并和数值模拟结果进行了对比分析,两者吻合较好。研究了自然超空泡射弹空泡形态和流体动力特性的变化规律。得到空泡闭合位置对压差阻力系数、摩擦阻力系数、总阻力系数的影响。研究了水下射弹模型结构参数对自然超空泡减阻特性的影响:空化器直径、空化器长度、长细比、尾部形状及模型表面粗糙度在空泡形成过程中对空化特性和流体动力特性产生影响,形成超空泡后,空化器直径对阻力系数起决定作用。研究了射弹弹体和空化器有攻角时空泡形态、阻力特性和升力特性的变化规律;弹体有攻角时空泡形态偏移明显,空化器有攻角时,升力系数增加明显。研究了超空泡射弹的受力状况及减阻特性。研究了射弹发射后速度和射程的变化规律,得到了射弹质量、阻力系数、发射速度及发射深度对射程影响的规律。通过对水下射弹形成的局部空泡通气,得到了水下射弹的通气超空泡,实现了中等速度条件下超空泡射弹。研究了通气超空泡形态特性,数值模拟得到形成通气超空泡后阻力系数的变化规律以及不同空化数条件下形成超空泡需要的通气量。通过试验得到通气超空泡射弹的速度变化以及速度衰减量、位移值和阻力系数,并与同样速度的不通气射弹进行对比分析,通气超空泡射弹速度衰减慢,位移大,阻力系数小,对超空泡的减阻特性进行了验证。研究了水下射弹关联运动流体动力特性。得到了串列两圆柱体的减阻规律,并与单独圆柱绕流情况进行了对比研究。分析了两圆柱体的受力,得到了模型参数对减阻规律的影响,两射弹串列可以大幅度减阻。研究了三个圆柱体串列的情况,获得多个圆柱体串列运行时的超空泡减阻规律。研究了射弹尾部气泡运动情况,得到了射弹串列运行时尾部气泡对发射频率的影响。研究了并列发射时两个射弹相互影响情况下流体动力特性,得到了不同间距情况下射弹阻力系数的变化规律,当两射弹间距过小时射弹间会产生侧向力。更多还原

【Abstract】 Supercavitation technology is a fresh theory and approach for the drag reduction of underwater bodies. Supercavitation flow is one of the most complicated multiphase hydrodynamics, which involves unsteady flow, compressibility, phase transformation, turbulence and other complicated hydrodynamics phenomena, and all of those behavior and properties involve great difficulties for the understanding of the cavity flow. In the content of this dissertation, numerical simulation methodology for vapor-filled and gas-filled cavity shape and drag behavior of kinetic energy projectiles is developed, and a matched laboratory experiments supercavitation kinetic energy projectiles were conducted. The major contributions of the present study are summarized below:The numerical simulation methodology of cavity shape and hydrodynamics characteristics of underwater kinetic energy projectile is conducted. The turbulence models used in supercavitation numerical simulation are analyzed. The numerical results are compared with the experimental results, and the suitable turbulence model is chosen for the future research.Numerical simulation studies on the hydrodynamics characteristics of the natural cavity flow over circular cylinder are conducted. The computation works include the analysis the influence of the aspect ratio on the cavity shape and drag characteristics, the cavitation number on the dimensionless length and diameter of the cavity, the cones, chamfer and flute on the circular cylinder on the cavitaion and drag characteristics. Direct comparisons experiments of circular cylinder kinetic energy projectile are conducted.The cavity shape and hydrodynamics of natural supercavitaion kinetic energy projectile are investigated. The influence of the location of the cavity closure on the pressure drag coefficient, friction drag coefficient and the total drag coefficien are analyzed. Numerical computation study on underwater projectile’s outline parameter, including diameter and length of cavitator, the aspect ratio of projectile, tails contour, and surface condition, And get the behavior and properties of cavitaion and drag reduction. The computation works are conducted on the influences of angle of attack of cavitator and angle of attack of projectile on the outline of cavity, drag, and lift behavior, the results show that the angle of attack of bodies induce displacement away from the axis of initial cavity, the angle of attack of cavitator make the lift coefficient increase greatly. The influences of projectile mass, drag coefficients, initial speed, and launch depth are investigated.When the partial natural cavitaion is ventilated, the ventilated supercavitation is obtained. The ventilated supercavitation projectiles are obtained at middle velocity, and the ventilated supercavitation shapes are investigated. The drag coefficients after the forming of supercavitation and the ventilation volume rate that can form supercavitation at different cavitation numbers are obtained. The velocity, velocity attenuation and displacement of projectile at different time obtained. Compaired with the unventilated projectile, the ventilated projectile has slow velocity attenuation, long displacement and small drag coefficient. The drag reduction characteristics of supercavitation are validated.The correlation motion hydrodynamic characteristics of underwater projectile are investigated. Using the numerical simulation the drag behavior of two circular cylinders in tandem arrangement is obtained, and compared with that of one circular cylinder. The force of two circular cylinders is analyzed, and the effect of model parameters on the drag is obtained. The results shows that the drag decreases a lot as two circular cylinders are arranged in tandem. The drag behavior of three circular cylinders in tandem arrangement is investigated, and the supercavitation drag reduction is obtained as multi circular cylinder is arranged in tandem. The bubble motion at tail of underwater projectile is studied, and the effect of bubble motion on launch frequency as multi circular cylinder is arranged in tandem. The hydrodynamic of two circular cylinders parallel arrangement is investigated, and the effect of distance on the drag coefficient of underwater projectile is studied. The side force appears when the distance is small.更多还原