关于通气空泡及其路径数值求解的挑战性问题（英文）

Ventilated cavitation has been successfully employed as ship drag reduction technology and potentially can mitigate flowinduced vibration. The obtained successes were based on solutions of design problems considered in the framework of ideal fluid theory with their following validation by towing tank tests. However, various aspects of the interaction of ventilated cavities with the viscous flows around the ship hulls remain unclear, whereas there is usually no possibility to simultaneously keep the full-scale Froude number and cavitation number in the test facilities. So, the further progress of the application of ventilated cavitation substantially depends on the ability of computational tools to predict this interaction. This paper briefly describes the state-of-the-art computation of ventilated cavitation and points out the most challenging unsolved problems that appeared in the model tests(prediction of air demand by cavities, ventilation effect on ship drag, on hydrofoil lift, and on the propagation of shock waves in cavities).     

转弯运动通气超空泡形态及流场结构数值研究

超空泡航行体机动过程中空泡形态的预测是目前该领域亟待研究的问题。文章在两流体多相流模型的框架内建立了用于求解通气超空泡流转弯机动的三维数值模型。通过求解RANS方程和SST(Shear Stress Transport)湍流方程,预测了圆盘空化器转弯机动条件下生成的通气空泡形态,并同Logvinovich独立膨胀原理的计算结果进行对比,验证了文中数值模型的有效性。在此基础上,分析了转弯半径对通气空泡的形态尺度的影响,对比研究了不同弗鲁德数条件下通气空泡的流场结构。     

均流中PPTC螺旋桨梢涡空泡数值预报（英文）

文章采用Sauer空化模型,研究了网格类型和湍流模型对均流中螺旋桨梢涡空泡数值模拟的影响,研究表明,现有的空泡模型适合于螺旋桨梢涡空泡的数值模拟,其中梢涡空泡区域网格密度是关键,文中提出了一种合适的梢涡空泡区域网格加密方法。对PPTC螺旋桨全湿流和梢涡空泡进行了数值预报,螺旋桨梢涡空泡形态与试验结果进行了对比,并应用涡判据Q准则和λ2准则分析了梢涡与梢涡空泡的流动特征。全湿流中梢涡区域的涡量随周向的分布呈现单峰特性,最小涡量在涡心处,而空泡流中梢涡空泡区域的涡量随周向的分布呈现双峰特性,最小涡量不在涡心处。     

空化器倾斜角对超空泡流影响的三维数值仿真研究

为了研究空化器倾斜角发生变化时流体动力变化规律及其对超空泡航行体控制有效性的影响,对圆盘和圆锥空化器在具有不同倾斜角时进行了数值仿真,仿真结果表明:空化器锥角不同时生成的超空泡形态和空化器的流体动力特性都有很大的不同;不同超空泡航行体对于空化器的选择应该根据航行体自身特点进行选择;将圆盘和圆锥空化器进行组合可以改变单一种类空化器的外形和流体动力特性,增加对空化器选择的灵活性.     

水下亚声速圆盘空化器射弹超空泡流动数值计算方法研究（英文）

To deal with the effect of compressible fluids on the supercavitating flow over the subsonic disk cavitator of a projectile, a finite volume method is formulated based on the ideal compressible potential theory. By using the continuity equation and Tait state equation as well as Riabouchinsky closure model, an inverse problem solution is presented for the supercavitating flow. According to the impenetrable condition on the surface of supercavity, a new iterative method for the supercavity shape is designed to deal with the effect of compressibility on the supercavity shape, pressure drag coefficient and density field. By this method, the very low cavitation number can be computed. The calculated results agree well with the experimental data and empirical formula. At the subsonic condition, the fluid compressibility will make supercavity length and radius increase. The supercavity expands, but remains spheroid. The effect on the first 1/3 part of supercavity is not obvious. The drag coefficient of projectile increases as the cavitation number or Mach number increases. With Mach number increasing, the compressibility is more and more significant. The compressibility must be considered as far as the accurate calculation of supercavitating flow is concerned.     

超空泡流理论的应用(英文)

对于二元定常超空泡流可以化成Rieman-Hilbert混合边值问题用奇异积分方程的方法来求解。对三元空泡流问题由于速度图映射法不能应用,只能求助于数值解。 与高速水翼和超空泡螺旋桨的设计有关的水翼剖面超空泡绕流问题属于小扰动问题,作者在1964年和1966年已求得解答。在螺旋桨设计中应用二元超空泡水翼理论,尚需考虑翼栅效应。作者介绍了应用动量理论求解超空泡翼栅流。 在换算实验结果与理论计算时必须注意筒壁对空泡流的影响。作者列出其估算式。 近年来对空泡流问题获得相当大的进展,现有的二元及准二元自由流线理论可以成功地用来设计定常运行下的超空泡翼型、螺旋桨及水泵。但对于非定常超空泡流尚须进一步研究。     

回注射流及其对通气超空泡形态影响的研究

通过水洞实验对回注射流现象及其对通气超空泡形态的影响进行了研究.实验水洞为封闭的连续通气水洞.通过高速摄像机记录回注射流及通气超空泡的动态变化过程.摄像机的拍摄速率为每秒1 000帧.文中在实验的基础上分析了超空泡形态变化趋势与回注射流之问的关系并讨论了回注射流的形成机理.此外,还分析了通气系数对回注射流的影响.     

液体可压缩性对高速射弹超空泡流的影响

旨在研究水的可压缩性和温度场对超高速水下航行体超空泡现象及其运动特性的影响。

首先,基于CFD通用软件Fluent 19.2,采用同时考虑水的压缩性和温度场的数值模型,对跨超声速航行体的自由运动进行计算,并与文献[相似文献   

流线型潜体首型对纵倾斜流涡结构的影响数值模拟（英文）

A flow field around a streamlined body at an intermediate angle of incidence is dominated by cross-flow separation and vortical flow fields. The separated flow leads to a pair of vortices on the leeside of the body; therefore, it is essential to accurately determine this pair and estimate its size and location. This study utilizes the element-based finite volume method based on RANS equations to compute a 3D axisymmetric flow around a SUBOFF bare submarined hull. Cross-flow vortex structures are then numerically simulated and compared for a submarine with SUBOFF and DRDC STR bows. Computed results of pressure and shear stress distribution on the hull surface and the strength and locations of the vortex structures are presented at an intermediate incidence angle of 20°. A wind tunnel experiment is also conducted to experimentally visualize the vortex structures and measure their core locations. These experimental results are compared with the numerical data, and a good agreement is found.     

波浪中船底空泡对振动吸收的研究（英文）

Bottom ventilated cavitation is the successfully proven ship drag reduction technology, but the impact of sea waves on ships with bottom cavities is the substantial concern for a broad technology implementation. The influence of waves on vertical force experienced by such ships is analyzed in this paper using a perturbation technique. The unperturbed cavity shape at given Froude number and cavity length was found from a nonlinear steady ideal fluid problem. The ship response to an impact of a wave of the given length and amplitude is considered as the one-frequency perturbation. This perturbation was found by combined consideration of compressible flow in the cavity and incompressible flow in the surrounding water. Computational examples relate to an earlier tested model with the bottom cavity restricted by skegs. The vertical forces on the model with bottom cavities and in cavitation-free conditions were compared in head and following seas. It was found that within the major part of the consider range of wavelengths the cavity acts as a shock absorber significantly reducing the vertical force pulsation and ship acceleration in waves.     

三维空泡回射流的理论研究（英文）

空泡回射流以某个方向冲击空泡壁面是导致空泡发生不同脱落方式的重要原因,但是空泡回射流的方向目前认为是一个不确定量,需要人为指定。该文针对无界重力流场中的三维空泡,基于势流假设和积分方程推导了一个计算回射流角度和回射流截面面积的三角函数代数方程组,并且在小角度条件下给出了回射流角度和截面面积的理论解析式。研究表明,空泡回射流角度与空化器的攻角、阻力和空泡浮力有关。     

海岸桩结构布置对波浪参数影响的数值模拟研究（英文）

In this study, the passage of waves through pile groups with different arrangements is investigated using a three-dimensional(3D)numerical model. For the simulations, waves of three different heights of 36, 58, and 81 mm, a fixed period of 0.88s, and a fixed wave length of 1.128 m were used. To simulate the waves and flow pattern through the piles, Reynolds-averaged Navier–Stokes(RANS) equations of fluid motion were solved based on the finite volume method(FVM). Piles were defined as obstacles in the rectangular domain using the fractional area/volume obstacle representation(FAVOR) method. The volume-of-fluid(VOF) and re-normalization group(RNG) methods were used to simulate the free surface and turbulence phenomenon, respectively. By performing different numerical simulations, the effect of coastal pile arrangements on wave pattern was studied and was compared with existing experimental data, and an acceptable agreement was achieved.     

空化器几何参数对通气超空泡生成影响的实验研究

为了探索通气超空泡的生成机理和获取形态可控有效减阻的超空泡,文章利用中速可持续通气空泡水洞进行了空化器和通气联合生成超空泡的实验研究.详细分析了通气超空泡的生成和发展过程;给出了空化器直径、空化器线形对通气系数门限值和通气超空泡形态的影响.研究表明,在相同条件下,较大直径空化器模型形成通气超空泡需要的通气系数门限值较低,相应的超空泡尺寸也较大;平头倒角形和圆盘形空化器比圆锥形的形成通气超空泡需要的通气系数门限值低,相同条件下前者形成的超空泡尺寸也较后者大;对于圆锥形空化器,锥角较小的不易形成通气超空泡.文中实验研究结果为水下航行体的空化器合理设计提供了重要的参考依据.     

基于空泡数值模拟的船尾流激振动治理研究

应用CFD数值模拟技术对螺旋桨空泡及其脉动压力进行评估,为螺旋桨、船尾线型及附体的优化设计提供依据。针对一艘双桨船振动过高的问题,提出轴支架和螺旋桨优化设计的方案。经评估,优化后螺旋桨空泡性能得到显著改善,诱导的船尾脉动压力从10 kPa以上降低至3 kPa左右,船尾振动得到大幅降低,并得到了实船振动测试结果的验证。     

螺旋桨空泡和噪声特性试验研究（英文）

本文通过螺旋桨空泡噪声模型试验,研究螺旋桨空泡和噪声特征,以及螺旋桨不同阶段空泡和噪声的关系,探究螺旋桨噪声产生及控制机理。建立了螺旋桨空泡和噪声同步测试方法,针对2400 TEU集装箱船螺旋桨开展模型试验。从螺旋桨模型试验结果分析得出:片空泡脱落形成梢涡空泡产生的噪声量级最高,且具有宽带特性,梢涡空泡噪声量级次之;模型状态下片空泡脱落形成梢涡空泡,以及独立的梢涡空泡引起的空泡噪声均在1 000 Hz附近存在明显峰值,对应实桨的峰值频率为50-60 Hz。     

细长体出水空泡特性实验研究（英文）

Experimental studies are carried out with slender bodies vertically exiting out of the water using a high-speed camera. The mechanisms for the formation, development, and collapse of the cavity around the slender body are explored. The dynamic characteristics of the shoulder cavity and the trail cavity during the water-exit of low-speed bodies are analyzed for various water depths and initial velocities. The results show that the initial velocity has a great influence on the formation, development, and collapse of the cavity. The length and the thickness of the shoulder cavity vary non-linearly with the depth.     

通气超空泡形态及视景仿真研究

超高速航行器在水下运动时,其大部分表面被超空泡包裹,构成了一种新的流体动力布局,运动模式和运动特性完全不同于常规水下航行器。为了分析超高速水下航行器运动的稳定性,本文对超空泡生成机理进行研究,给出描述超空泡形态的数学模型,得到不同影响因素作用下超空泡形态的变化规律。为验证超空泡实时生成效果和超高速水下航行器运动过程各种动作功能,采用Vega Prime构建三维虚拟环境,在此基础上设计超空泡视景演示系统,通过ADI仿真系统实时解算超空泡和水下航行器运动数据来驱动超空泡视景系统,逼真地演示超空泡动态生成过程以及水下航行器高速运行轨迹和“空泡+航行器”的相对运动关系等关键技术。     

通气空泡内部流场结构实验研究

采用人工通气的办法在水下航行体表面生成通气超空泡可以大幅降低水下航行阻力。保持通气空泡的形态稳定是保证航行体水下流体动力稳定的前提,因此需要了解通气空泡内部气体流动结构及其与空泡泄气方式的相互影响规律。该文建立了通气空泡内部流场结构的实验测量装置,并运用PIV(粒子成像测速)方法对通气超空泡内流场结构进行了测量,归纳了通气空泡三种典型的内部流场结构形式及其成因,并给出了泡内气流流速的变化趋势。     

通气超空泡形态及视景仿真研究

超高速航行器在水下运动时,其大部分表面被超空泡包裹,构成了一种新的流体动力布局,运动模式和运动特性完全不同于常规水下航行器。为了分析超高速水下航行器运动的稳定性,本文对超空泡生成机理进行研究,给出描述超空泡形态的数学模型,得到不同影响因素作用下超空泡形态的变化规律。为验证超空泡实时生成效果和超高速水下航行器运动过程各种动作功能,采用Vega Prime构建三维虚拟环境,在此基础上设计超空泡视景演示系统,通过ADI仿真系统实时解算超空泡和水下航行器运动数据来驱动超空泡视景系统,逼真地演示超空泡动态生成过程以及水下航行器高速运行轨迹和"空泡+航行器"的相对运动关系等关键技术。     

通气超空泡研究中的几个问题

根据在水洞中所作的系列通气超空泡试验,以及国内外的大量相关文献,综述和探讨了通气超空泡实验研究中的几个主要问题.主要内容包括通气超空泡试验中的相似准则考虑;重力场对通气超空流的影响规律;通气超空泡的闭合和气体泄漏问题;通气超空泡的不稳定性机理.最后,对通气超空泡的试验研究方向进行了展望.