【作者】 王健；

【导师】 刘影；

【作者基本信息】 北京理工大学 ， 动力工程及工程热物理， 2015， 硕士

【摘要】 空化是指在一定条件下液体介质内部出现蒸汽穴或者蒸汽泡的现象。通常，当物体在液体中作高速运动或高速运动的液体绕物体流动时，高速促使空化产生，反过来，空化又极大地影响物体的水动力特性。发展合理的空泡流模型用于模拟高速条件下复杂的空化流动迫在眉睫，不仅具有重要的理论指导意义，而且有着广泛的工程应用价值。本文以圆盘空化器为研究对象，主要研究了高速条件下的空化流动特性及数值计算方法。主要研究内容及成果如下：基于实验结果，比较和分析了两种湍流模型在空泡形态、流场结构和阻力特性等方面的差异。发现标准k-模型对圆盘空化器的阻力基本保持不变，空泡形态稳定，压力场、速度场和涡量场均上下对称，与实验结果相差较大；而FBM模型对圆盘空化器的阻力表现出与实验相同的波动规律，FBM和实验的阻力均值非常接近，空泡形态与实验均表现为产生—发展—脱落的周期性。建立一种高速空泡流模型，该模型以介质的可压缩性为理论基础，引入能量方程和修正的空化模型进行完善。基于实验结果，研究了高速空泡流模型在低速不可压缩计算中的应用。与实验结果的对比表明，建立的模型能够很好的捕捉空泡的产生—发展—脱落的周期过程，数值和实验所获得的阻力非常接近。基于势流理论、细长体理论以及半经验公式，研究了高速空泡流在高速可压缩计算中的应用。结果表明，建立的模型的空泡形态与1/3理论、势流理论的解析解和半经验公式的经验解的空泡形态基本吻合，印证了空泡前端轮廓与空化数无关的结论。在马赫数不变的情况下，印证了细长体理论关于马赫数不变时，空泡长细比随着空化数的减小而增大的结论，同时印证了势流理论关于马赫数不变时，阻力系数随着空化数增加而增大的结论。马赫数对绕圆盘空化器空化流动特性的影响较大。在空化数不变的情况下，印证了势流理论关于空化数不变时，空泡长细比和阻力系数随马赫数增加而增大的结论，并且对应流场中的最高压力、最大混合密度均增加，最小混合密度减小。空化数对绕圆盘空化器空化流动特性的影响较大。在马赫数不变的情况下，随着空化数的减小，其对应流场中的最小密度下降，空泡长细比增加。更多还原

【Abstract】 Cavitation is a kind of phenomenon that vapor cavity or vapor bubble appears in liquidphase at some specific conditions. When an object as a high-speed movement in a liquid orthe liquid in high-speed flow around the object, the high-speed promote cavitationgenerated, cavitation also greatly affect the hydrodynamic characteristics of the object.Develop a reasonable model applied to simulation the complex cavitation flow athigh-speed, it’s not only of great theoretical significance but also of wide application valueson engineering. This dissertation is aimed at researching the cavitation flow characteristicsand numerical methods at high speed around the disc cavitator. The primary researchingcontents and results are as follows:In order to research the differences in cavity shape, flow filed structure and dragcharacteristics, two different turbulence models are compared and analyzed based on theexperimental results. The results show, In the standard k-model, the resistance against thedisc cavitator and cavity shape are stable, pressure, velocity and vorticity field are verticallysymmetrical, which is difference with the experiment results. In the FBM model and theexperiment, the resistance against the disc cavitator show the same fluctuation law, and themean of the resistance are very close, and the cavity shape are shown togeneration-development-shedding cyclical.Establish a high-speed cavitation flow model. In this model, the compressibility of themedium as the theoretical basis, and take into the energy equation and cavitation modelwhich was modified. The high-speed cavitation flow model in low-speed incompressiblecalculation is researched based on the experimental results. The results show, thehigh-speed cavitation flow model can well capture the generation-development-sheddingcycle process of the cavity shape, the resistance obtained by the numerical and theexperiment are very close. The high-speed cavitation flow model in high-speedcompressible calculation is researched based on the potential flow theory, the slender bodytheory and the semi-empirical formula. The results show, the cavity shape of the numericalis consistent with the results of the1/3theory, the potential flow theory and thesemi-empirical formula, confirm the conclusion that the contour of the front cavity shapewhich is unrelated with the cavitation number. Under the condition of the mach number isconstant, confirm the conclusion that the cavity slenderness ratio decrease as the cavitation number increase in the slender body theory, and confirm the conclusion that the dragcoefficient increase as the cavitation number increase in the potential flow theory.The mach number has a great influence on the flow filed characteristics around thedisc cavitator, under the condition of the cavitation number is constant, confirm theconclusion that the cavity slenderness ratio and the drag coefficient increase as the machnumber increase, and the corresponding maximum pressure and the maximum mixeddensity in the flow filed increase, the corresponding minimum mixed density in the flowfiled decrease.The cavitation number has a great influence on the flow filed characteristics aroundthe disc cavitator, under the condition of the mach number is constant, the correspondingminimum density in the flow filed decrease and the cavity slenderness ratio increase as thecavitation number increase.更多还原