【作者】 贾力平；

【导师】 张嘉钟；

【作者基本信息】 哈尔滨工业大学 ， 一般力学与力学基础， 2007， 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,其减阻的主要原理是利用在航行体表面形成的气层使周围液体与航行体表面相隔离,减少其沾湿面积,从而大幅度的降低了航行体的粘性阻力。超空泡的理论研究过去主要是应用势流理论,近十几年出现了应用基于N-S方程的均质平衡流理论来处理空泡流的研究。现有的空化模型在自然空化仿真研究中取得了较好的效果,但由于没有考虑或者没有合适考虑气体可压缩性,对通气超空泡的仿真,造成了与实验结果的极大偏离。本文把完全气体方程引入均质平衡流理论的空化模型,导出了考虑压缩性的通气空化模型,基于该模型对空化器超空泡特性进行了详细的数值仿真。超空泡的实验研究根据实验设施主要有水洞实验和射弹实验,两种设施各有优劣。本文利用水洞与射弹实验两种方法对空化器超空泡特性开展了大量的实验研究。具体研究工作如下:数值仿真工作主要是基于导出的可压缩通气空化模型,对典型空化器模型通气超空泡形态规律进行了仿真,分析了通气超空泡的流场特性,研究了流场参数对通气超空泡形态发展规律的影响,获得了超空泡形态随通气率和空化数变化关系的拟合公式;仿真和分析了空化器参数对通气超空泡形态和减阻特性的影响规律,为水下超空泡航行体的通气规律设计提供了一定参考依据。基于自然空化模型,对圆锥空化器的超空泡形态和阻力特性进行了数值仿真。研究了圆锥空化器的超空泡形态和阻力系数随空化数和锥角的变化关系;讨论了圆锥空化器的零空化数的特性和意义;对可移动圆锥空化器特性进行了数值仿真研究;对自由闭合和非自由闭合的超空泡形态发展规律进行了比较分析;开展了三维模拟计算,分析了圆盘空化器攻角变化对超空泡形态和减阻特性的影响规律。实验研究工作包括水洞实验和射弹实验。利用水洞实验研究分析了通气超空泡的形成和发展过程,以及空化器参数对通气系数数门限值和超空泡形态的影响规律;给出了空化器直径与超空泡的减阻效果关系;探讨分析了空化器缩颈长度对超空泡形态的影响;研究了流场参数(自然空化数和弗鲁德数)对通气超空泡生成特点和形态尺寸的影响规律;利用细杆模型试验分析了自由闭合通气超空泡特性,验证了数值仿真结果的有效性。利用射弹实验,研究分析了自然超空泡的生成和发展规律。给出了平头和120 o圆锥头弹体超空泡尺寸随空化数变化的拟合公式,并与文献中经典理论公式进行了比较,验证了理论公式的正确性。同时,与本文的数值仿真结果进行比较,验证了数值仿真的有效性。对部分自然和通气超空泡的外形轮廓进行了测量研究分析,并与文献中的经验公式进行了比较,验证了经验公式的可使用性。更多还原

【Abstract】 Supercavitation technology is a new theory and approach which realizes high speed navigation of water vehicles. The main principle of its reduction drag is using a layer gas on body wall make the moving body isolated from water to avoid considerable viscous forces. The theoretical studies of cavitation primarily utilize the potential flow theory. Studies dealing with cavitation modeling through the computation of the N–S equations have emerged in the last decade. The current cavitation models can reasonably model natural cavity, but there are some limitation for modeling ventilated cavity due to ignoring considering condensability of the gas, which results in the bigger difference between simulated and experimental results. In this paper, state equation of complete gas is imported into cavitation model and the ventilated cavitation model with condensability effect is deduced. Based on the model, the main characteristics of supercavity initiated at cavitator are numerically simulated. Experimental apparatus applied for cavitation study may be divided into two great groups: hydrodynamic tunnels or flumes and projectiles, which have separately advantage and shortage. In this paper, water tunnel and projectile experiments are also carried out to study main characteristics of cavitator supercavity. The main works are as follows:The main works of numerical model are that the developed rules of ventilated supercavity are numerically simulated based on the ventilation cavitation model with condensability effect. The flow field of ventilated supercavity is analyzed, and flow parameters effecting on the developed rules of ventilated supercavity is studied. The fitted formulae between supercavity size and ventilation coefficient or cavitation number are obtained and using ventilated cavitation model also simulates the effect of cavitator parameters on ventilated supercavity shape and reduction drag. Those research results provide some reference for the design of ventilation system of underwater vehicles.Simultaneity, using natural caivtation model simulates natural supercavity shape and drag characteristics for cone cavitators. The main studies are the relations of cavitation number and the angle of cone effecting on supercavity size and drag coefficient, and zero cavitation number is analyzed. The speciality of movable cone cavitators is numereically simulated. The free-close and non-free-close supercavities are numerically simulated and compared. Using three-dimension numerical simulation obtaines the effect rules of disk cavitator attack angle on supercavity shape and drag reduction.Experimental works mainly include water tunnel and projectile experiments. Through water tunnel experiments, the formulation and development of ventilated supercavity have been analyzed and cavitator parameters effectting on the critical ventilation coefficient and supercavity size has been studied. The relations between cavitator diameter and reduction drag of ventilated supercavity are given. Influence of cavitator neck length on ventilated supercavity shape has been discussed. Influence rule of flow parameters (natural cavitation number and Froude number) on ventilated supercavity formation and size has been obtained. Using the experimental results of slender pole model analyzes free-close ventilated supercavity and validates the validity of numerical simulated results.Using projectile experiments studies the formulation and development of natural supercavity. The empirical formulae of natural supercavity shape have been presented. The typical formulae of supercavity size in literatures are been compared with experimental results. The experimental results are also been compared with numerical simulated results. The contour of partial natural and ventilated supercavities are measured and studied. Their contours are compared with experiential formulae and confirm its validity.更多还原