细长体出水动力学的实验研究及数值模拟

发布时间：2018-02-14 11:29

本文关键词： 高速航行体出水超空泡自由面大攻角数值模拟　出处：《浙江理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：超空泡减阻技术军民两用前景广阔，虽然我国近几年来在超空泡减阻技术方面开展了大量的研究，也取得了大量的成果，但是与西方发达国家尤其是与美国和英国相比，我国在超空泡以及空蚀方面的研究方法和研究进展都未达到国际先进水平，在高速航行体出水水动力学特性和机理方面的研究基本上还是处于初级阶段，取得的成果也相对较少，所以无论是在数值计算还是在试验研究方面都有待于我们进一步深入。本文的工作目的是：通过实验和数值计算的方法研究高速航行体出水时壁面在水中形成的自然空泡的生长和溃灭机理以及航行体对自由液面的扰动规律，主要的工作包括：（1）根据本文研究工作的需要，自主设计搭建了一套安全可靠地高速航行体出水的实验研究系统，利用高速摄影系统拍摄和观测不同模型以不同攻角出水时细长体周围的空化现象以及流场形态，利用计算机辅助软件整理分析出有价值的实验数据。（2）通过商业软件FLUENT对实验中细长体以不同攻角和不同速度出水工况进行数值模拟，计算结果与实验数据进行对比验证。取得的一些研究成果如下：（1）由于流体的粘性作用以及细长体壁面与局部空泡发生碰撞，造成细长体出水速度振荡式下降。（2）细长体随着随时间不断的露出水面时，液体对壁面的粘性阻力开始下降，细长体壁面所产生的空泡在自由液面附近开始溃灭，造成细长体的浮力和附加质量力都迅速下降，导致细长体出水速度在完全出水时刻有一个突增，，随后继续震荡下降。（3）随着细长体速度的增大细长体壁面逐步产生超空泡，并且细长体的头部和尾部极易产生局部空泡，头部超空泡的闭合以及溃灭规律与空泡闭合经验模型相符。（4）头型尖锐的细长体对自由液面隆起程度影响较小，而相对平钝的尾部对自由液面隆起程度影响较大，并且液面的隆起时间发生较早。（5）随着细长体的速度和本身尺寸的增大对自由液面造成的挤压和撞击作用加剧，“喷溅”现象也就越明显并且对整个流场影响范围扩大。（6）随着细长体出水攻角的增大，细长体的迎风面与背风面两侧的自由液面隆起程度是不对称的，细长体迎风面的液面隆起较为陡立并且影响范围较小，而背风面的液面隆起较为平缓并且影响范围较大。（7）通过数值模拟计算航行体的长径比，出水速度，以及出水攻角对自由液面的扰动与实验结果吻合度较大。
[Abstract]:Super cavitation drag reduction technology has a broad prospect for both military and civil use. Although China has carried out a lot of research in the field of supercavitation drag reduction technology in recent years and achieved a great deal of results, it is compared with western developed countries, especially the United States and Britain. The research methods and research progress of supercavitation and cavitation erosion in China are not up to the international advanced level, and the research on the hydrodynamic characteristics and mechanism of high-speed navigation body is still in the primary stage. The results obtained are also relatively few, so we need to further study both numerical calculation and experimental research. The purpose of this paper is to study the growth and collapse mechanism of the wall cavitation formed in the water and the disturbance law of the free liquid surface by the method of experiment and numerical calculation. The main work includes: (1) according to the needs of the research work in this paper, a set of experimental research system for safe and reliable effluent from high-speed navigation body was designed and built independently. The cavitation phenomena around the slender body and the shape of the flow field around the slender body with different angles of attack were recorded and observed by high-speed photography system. Computer aided software is used to analyze valuable experimental data. (2) numerical simulation of slender body with different attack angle and different velocity is carried out by commercial software FLUENT. Some of the results obtained are as follows: 1) due to the viscous effect of the fluid and the collision between the slender wall and the local cavitation, As the slender body emerges over time, the viscous resistance of the liquid to the wall begins to decrease, and the cavitation produced by the slender wall begins to collapse near the free surface. The buoyancy and the additional mass force of the slender body decrease rapidly, which results in a sudden increase in the outlet velocity of the slender body at the time of the complete effluent, and then continues to oscillate and decrease. 3) with the increase of the velocity of the slender body, the supercavitation is gradually produced on the wall of the slender body. It is easy to produce local cavitation in the head and tail of the slender body. The closure and collapse of the supercavitation in the head are consistent with the empirical model of cavitation closure. 4) the sharp slender body of the head has little effect on the free surface uplift. The relatively flat tail has a greater effect on the free surface uplift. And the uplift of the liquid surface occurred earlier. 5) with the increase of the velocity and size of the slender body, the extrusion and impact on the free liquid surface increased, and the phenomenon of "spatter" became more obvious and affected the whole flow field. With the increase of the angle of attack of the slender body, The degree of free liquid surface uplift on both sides of windward surface and leeward surface of slender body is asymmetrical, and the liquid surface uplift of slender body windward surface is steeper and has a smaller influence range. On the other hand, the leeward surface uplift is relatively gentle and has a large influence range. 7) the numerical simulation is used to calculate the ratio of length to diameter, the velocity of outlet water and the disturbance of outlet angle of attack to the free liquid surface, which is in good agreement with the experimental results.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TJ6;U674.70

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