【作者】 王瑞；

【导师】 党建军；

【作者基本信息】 西北工业大学 ， 兵器科学与技术， 2019， 博士

【摘要】 超空泡减阻技术可使航行体壁面附近的流体由水变为气体,从而大大降低航行阻力。超空泡减阻技术应用于火炮领域后,可使火炮发射的超空泡射弹具备水下作战能力,能够对水雷、鱼雷、UUV、蛙人等水下目标进行硬杀伤,将对未来水下近程防御作战方式和装备发展产生革命性作用。超空泡射弹以其优异的跨介质和水下作战能力,具有广阔的军事应用前景。然而超空泡射弹火炮武器工程研制中还面临着超空泡射弹流体动力外形设计、稳定入水、水弹道优化等技术“瓶颈”,急需开展相关方面的基础理论研究。本文运用数值仿真、理论分析和试验研究相结合的方法,对射弹跨音速航行超空泡绕流特性、超空泡射弹跨音速入水及水中航行流体动力特性与弹道特性、超空泡射弹流体动力外形设计方法等进行了研究,主要研究工作和创新点如下:(1)建立了高速射弹可压缩自然超空泡流场计算方法。该计算方法考虑了水的可压缩性,深入而系统的研究了不同多相流模型、湍流模型、空化模型在跨音速自然超空泡流场仿真计算过程中的计算效率和计算精度,并利用经典文献试验结果考核了该计算方法。数值模拟获得的射弹高速入水空泡形态、水中跨音速航行时的空泡形态及水中激波形态与文献试验结果吻合良好,验证了计算方法的计算精度和有效性。(2)研究了超空泡射弹跨音速入水过程与水中跨音速航行过程的绕流特性。研究表明:高速入水过程中,入水速度、入水角等主要影响入水空泡的开口尺度和对称性,对120_nD以后的空泡轮廓影响不大;攻角主要影响入水空泡的对称性。水中跨音速航行时,超空泡发展受到压缩性影响,弹体头部的密度、压力增大,弹体头部压缩波面堆积形成弓形脱体激波;空化数主要影响空泡总体长度,可压缩性主要影响弹体周围的空泡尺度;攻角主要影响射弹和超空泡的位置关系,大攻角时,射弹沾湿严重;这些结论是超空泡绕流特性在考虑可压缩性时表现出的新特征和新规律。(3)研究了不同工况条件下入水及水中跨音速航行时定常与非定常流体动力特性,获得了不同参数对流体动力特性的影响规律。研究表明:射弹入水过程中,存在临界入水初速和临界入水攻角,且不同入水速度存在不同的临界入水攻角;当入水初速、入水攻角均小于临界值时,流体动力系数峰值在形成稳定尾拍时达到最大,有利于减阻航行;仅入水攻角大于临界值时,流体动力系数峰值入水首个波峰达到最大,并逐渐降低至稳定尾拍时的流体动力系数峰值,不利于减阻航行;该结论尚未见公开报道。(4)研究并试验验证了超空泡射弹空中弹道、入水及水中弹道特性。根据建立的超空泡射弹空间运动方程组,研究了发射角、攻角、俯仰角等初始参数对空中弹道的影响规律,提出了获得较好入水初始参数的要求。利用6DOF方法开展了射弹入水及水中弹道特性仿真研究,获得了入水角、入水速度、入水攻角、入水角速度等参数对入水及水中弹道特性的影响规律;并利用水平入水弹道试验数据对超空泡尺度、速度变化曲线等仿真计算结果进行了验证,结果表明该计算方法正确合理,计算精度良好。(5)提出了超空泡射弹结构外形设计方法。基于超空化理论与空气动力学理论知识,结合前面章节的研究成果,提出了超空泡射弹头部空化器、主体段、尾翼外形与布局等部位的设计原理,并对某超空泡射弹结构外形尺寸进行了改进优化。通过对改进前后超空泡射弹的气动特性、入水及水中空泡形态、流体动力与弹道特性等进行仿真与试验评估,认为改进后的超空泡射弹兼备良好的空中稳定性和水中稳定性,且水弹道性能获得较大的提升,证明了超空泡射弹结构外形设计方法的正确性和合理性。本文的研究成果可为跨音速超空泡射弹弹道预报、流体动力布局设计和工程应用提供理论依据。更多还原

【Abstract】 The supercavitation drag reduction technology can change the fluid near the surface of the vehicle from water to gas,thus greatly reducing the navigation resistance.After the application of supercavitation drag reduction technology in the field of artillery,the supercavitation projectile launched by artillery can have the ability of underwater combat,and can hardly damage underwater targets such as mines,torpedoes,UUV and frogman,etc.It will play a revolutionary role in the development of underwater short-range defense combat mode and equipment in the future.Supercavitating projectiles have broad military application because of their excellent cross-medium and underwater combat capabilities.However,there are still technical bottlenecks in the development of supercavitating projectile weapon engineering,such as hydrodynamic configuration design,stable water entry,water trajectory optimization and so on.It is urgent to carry out basic theoretical research in related fields.In this paper,numerical simulation,theoretical analysis and experimental study are combined to study the supercavitation flow around projectiles in transonic navigation,hydrodynamic and ballistic characteristics of supercavitating projectiles in transonic water entry and underwater navigation,and hydrodynamic configuration design method of supercavitation projectiles.The main research work and innovations are as follows:(1)A computational method for compressible natural supercavitation flow field of high-speed projectiles is established.Considering the compressibility of water,the computational efficiency and accuracy of different multiphase flow models,turbulence models and cavitation models in the simulation of transonic natural supercavitation flow field are studied thoroughly and systematically.The cavity profile of the projectile entering water and under water transonic navigation as well as the profile of underwater shock wave obtained by numerical simulation are in good agreement with the experimental results in literature,which verifies the validity of the calculation method.(2)The flow characteristics of supercavitating projectiles in transonic water ertry and underwater transonic navigation are studied.The results show that in the process of high-speed water entry,the velocity and angle of water entry mainly affect the opening size and symmetry of the water-entry cavity,but have little effect on the cavity profile which are120 times the diameter of the cavitator from the head,and the angle of attack mainly affects the symmetry of the water-entry cavity.When navigating at transonic speed in water,the development of supercavitation is affected by compressibility.The density and pressure around the projectile head increase,and the compressional wave in front of the projectile head accumulates to form a bow-shaped detached shock wave.The cavitation number mainly affects the overall length of the cavity,the compressibility mainly affects the size of the cavity around the projectile and the angle of attack mainly affects the positional relationship between projectile and supercavity.These conclusions are new features and laws of supercavitation flow characteristics when considering compressibility.(3)The steady and unsteady hydrodynamic characteristics of entering water and underwater transonic navigation under different conditions are studied,and the effects of different parameters on hydrodynamic characteristics are obtained.The results show that there are critical initial velocity and critical angle of attack in the process of projectile entering water,and there are different critical angle of attack with different velocity of entering water.When the initial velocity and angle of attack are less than the critical value,the peak value of hydrodynamic coefficient reaches the maximum when the steady tail-slap is formed,which is beneficial to reducing drag navigation.When the angle of attack is greater than the critical value,the peak value of hydrodynamic coefficient reaches the maximum at the first wave peak of water entry,and gradually decreases to the peak value of hydrodynamic coefficient at steady tail slap,which is harmful to drag reduction.The above conclusion has not been reported publicly.(4)The trajectory characteristics of supercavitating projectile from air navigation to entering water and underwater navigation are studied and tested.Based on the space motion equations of supercavitating projectiles,the influence of initial parameters such as launch angle,attack angle and pitch angle on air trajectory are studied,and the requirement of obtaining better initial parameters of water entry is put forward.The simulation study of projectile’s entering water and underwater trajectory characteristics are carried out by using 6DOF method.The effects of entering water parameters such as angle,velocity,attack angle and angular velocity on the trajectory characteristics of water entry and underwater navigation are achieved.The simulation results of supercavity profile and velocity curve are validated by using the horizontal water entry trajectory test data.The results show that the calculation method is correct and reasonable,and the calculation accuracy is good.(5)The configuration design method of supercavitating projectile is put forward.Based on spercavitation theory and aerodynamics theory,the design method of supercavitation projectile’s head,main section,tail shape and layout are presented combined with the research results of the previous chapters.By using this method,the configuration of a supercavitating projectile are improved and optimized.Compare the simulation and experimental evaluation of the aerodynamic characteristics,cavity profile,hydrodynamic and ballistic characteristics of the supercavitating projectile before and after the improvement,it is considered that the improved supercavitating projectile has both good air stability and water stability,and the water ballistic performance has been greatly improved,which prove the correctness and reliability of the design method of supercavitating projectile configuration.Research results of this paper provide theoretical basis for trajectory prediction,hydrodynamic layout design and engineering application of transonic supercavitating projectile.更多还原