RANS方法预报对转桨定常敞水性能研究

以时均化的雷诺方程结合标准k-ε湍流模式作为控制方程,采用混合面模型(MP)将对转桨非定常问题简化为定常,建立对转桨敞水性能数值模拟方法.开展了两对水下高速航行体用对转桨的敞水性能数值模拟,与试验结果及MRF模型预报结果进行了对比分析,结果表明:两种数值模拟方法均能可靠地预报对转桨的敞水性能,预报精度满足工程应用需要.     

基于CFD的导管调距桨尺度效应研究

常规螺旋桨在进行水动力实验时,需要满足临界雷诺数的要求,这样,实桨的尺度效应就可以忽略。但是,对于非常规螺旋桨,如导管螺旋桨,尺度效应能否忽略值得研究,因为机翼型导管和螺旋桨水动力性能各自随几何尺寸变化的规律不一致。基于CFD计算方法,对某导管调距桨的尺度效应进行数值研究。在获得可靠的数值模拟方法后,数值模拟了两个螺距比和两个进速下不同尺寸导管螺旋浆的流场。比尺包括1、1.7、3.4、4.25、8.5和17共6个几何尺寸。计算结果表明,导管螺旋桨敞水性能的尺度效应比预期的要明显。随着尺寸增大即雷诺数增大,导管的推力先略有增加后基本不变,螺旋桨的扭矩和推力略有下降,但效率有所增加;小螺距比工况下的尺度效应要比大螺距比的大。     

VLCC大侧斜螺旋桨设计可行性研究

本文阐述了大侧斜螺旋桨设计软件包的功能及其使用特点。设计软件包括升力线和升力面设计程序，并能自动生成桨的三投影图和标准尺寸。通过对４艘大型船舶６个大仙斜桨的模型试验，证实了设计方法是可信的，程序包是有效的。为与常规的图谱设计方法进行比较，对其中两艘船按桢的条件各设计了一个ＭＡＵ桨，并加工了桨模。在大型空不筒中用假尾模拟伴流场后对７个桨模作了脉动压力测量。试验结果表明，大侧斜桨与常规桨相比，脉动压力     

On the mechanism of the bursting phenomena of propeller tip vortex cavitation

 The bursting phenomenon of tip vortex cavitation of a propeller sometimes causes severe high-frequency vibration, but its mechanism has not yet been elucidated. In this study, we carried out model experiments by changing the propellers, wake distributions, thrust coefficients, and cavitation numbers parametrically, examined the bursting phenomenon with a high-speed video camera, and measured the pressure fluctuations caused by the phenomenon. We also measured flow distribution around the tip vortex. As a result, we found that in the bursting phenomenon, large pressure fluctuations occurred twice, and that they strongly depended on the wake distribution. Two means were suggested to suppress the bursting phenomenon, other than changing the wake distribution: stabilizing tip vortex cavitation or reducing the cavity volume. Numerical fluid simulations around a propeller in noncavitating, unsteady conditions were also conducted, and the strength of the tip vortex along the circumference and its derivative were examined. As a result, the phenomena were parameterized by the time derivative of the strength of the tip vortex, and if it was higher than a threshold value, the tip vortex cavitation burst. Therefore, it is possible to predict the occurrence of the bursting phenomenon by numerical analysis. Received: November 6, 2001 / Accepted: January 24, 2002     

螺旋桨叶剖面优化设计比较研究

比较研究了船舶螺旋桨最高空泡起始航速的叶剖面优化设计方法。优化设计方法由剖面参数表达、空泡斗预报和最佳空泡起始性能遗传算法翼型优化三部分组成。Eppler方法采用10个参数表达任一翼型,已被有效应用到最高起始航速的螺旋桨叶剖面优化设计中。除了Eppler方法中的设计参数,剖面参数表达也可采用B样条曲线的控制点参数实现。对上述两种剖面参数表达方法进行了叶剖面优化设计比较研究,得到了一些结论。     

均流中PPTC螺旋桨梢涡空泡数值预报

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.     

基于Eppler剖面设计方法上的提高空泡起始航速的非定常螺旋桨设计方法

为了提高螺旋桨的空泡起始航速，本文提供了一个基于Eppler剖面设计方法上的非定常螺旋桨设计方法，二维剖面直接由Eppler剖面设计方法给出并直接输入到升力面设计程序中进行三维剖面设计。计算结果表明新剖面螺旋桨方案的空泡斗要比常规剖面的宽。在平均伴流条件下使用升力线、升力面设计程序给出一个初步螺旋桨方案。然后用定常/非定常面法检查设计结果是否满足推力要求并作修改设计，从中选择一个不符合空泡要求的剖面作为关键剖面。使用Eppler剖面设计方法来改善空泡斗，为了研究剖面弦向负荷对螺旋桨性能影响，本文设计两只螺旋桨，一只为带有Naca66迭加Naca a=0.8，另一只为新剖面的方案。模型试验结果证实了设计方法的有效性。     

孔腔脉动压力及其波数—频率谱的大涡模拟研究

孔腔流动中包含着流动分离和失稳以及涡旋相互干扰等复杂的流动现象。孔腔涡旋流动引起的流体振荡能够引起脉动压力的显著增加从而产生强烈的噪声,在工程实际中备受关注。湍流脉动压力是流激噪声的重要来源,也是湍流研究中的基础性问题,对其进行数值计算研究是流声耦合领域的重要内容,而湍流脉动压力波数—频率谱的构建更是该领域的技术难点。文章采用大涡模拟方法(LES)对孔腔脉动压力进行了数值模拟,考察了四套网格和四种亚格子应力模型对计算结果的影响,并与试验结果进行比较,验证数值计算方法的可靠性。首先采用大涡模拟方法计算了孔腔的脉动压力,并与中国船舶科学研究中心的空泡水筒试验结果进行对比分析。接着详细地分析孔腔脉动压力,研究亚格子应力模型和网格数量对计算结果的影响。最后,对数值计算得到的脉动压力多元阵列结果进行时间/空间Fourier变换,构建了三维脉动压力波数-频率谱。该文工作对今后流激结构振动噪声的预报和流动控制研究奠定了基础。     

相位差对双桨船脉动压力预报的影响研究

文章对双桨船脉动压力进行了计算,计算时考虑了左右螺旋桨之间的相位差对脉动压力计算的影响,结果证明汁算双桨船的脉动压力时,相位差的影响不能忽略,不同的相位差得到的计算结果有明显差别,越靠近船体内侧,相位差引起的幅值变化越大.相位差的影响还同双桨的距离有关系,双桨的距离越近,相位差的影响越显著,随着双桨距离加大,相位差的影响减小.这可以部分解释脉动压力模型实验和实船测试中的一些现象,同时也提醒试验人员在进行双桨船脉动压力试验时,要注意双桨相位差的影响.     

水面舰船流噪声数值预报研究与应用

在梳理流噪声数值预报方法的基础上,采用流场大涡模拟（large eddy simulation,LES）和声学边界元（boundary element method,BEM）方法在频域内计算预报了船体流噪声谱曲线,求取了其等效声中心.LES计算时选用动力学Smagorinsky-Lilly（dynamic Smagorinsky-Lilly,DSM）亚格子应力模型,流噪声由船体壁面脉动压力和法向速度特性决定,声源节点和声节点变量传递采用一对一的守恒传递方式.结果表明：某型船在航速14 kn时,裸船体流噪声在20 Hz~2 kHz频段内总声源级为133dB;当计算有效频段扩展到20 kHz时,总声源级达143.3 dB.流噪声主要来源于兴波引起的涡量,且主要集中于100 Hz~10 kHz频段.球首尾流区和船体尾涡区对流噪声辐射量贡献明显,特别是球首尾流区,对全频段都有明显的贡献,为水面舰艇流噪声研究提供了一条新的途径.     

诱导轮对离心泵空化性能影响数值分析

为了提髙诱导轮离心泵的空化性能和运行稳定性，阐明诱导轮对离心泵空化性能的影响规律，以某型船用凝水泵为研究对象，采用数值模拟手段预测前置诱导轮的空化性能，同时预测了多工况下叶轮的空化性能。数值模拟结果表明：在小流量工况和额定工况下，空化性能曲线基本一致；在大流量工况下，空化特性曲线波动相对比较严重，空化性能较差。     

熵格子Boltzmann方法的重整化群代数湍流模型

重整化群理论所建立的湍流模型能够最大程度地减小模型经验性,因此文章尝试将重整化群代数湍流模型引入到熵格子Boltzmann方法中,建立新型的计算模型以对高雷诺数湍流进行模拟研究。同时为了进行比较研究,还建立了熵格子Boltzmann方法的标准大涡模拟模型。完成了对高雷诺数湍流绕流场的模拟计算。结果表明:所建立的熵格子Boltzmann方法重整化群代数湍流模型能够有效地模拟高雷诺数湍流流动问题;其对紧贴壁面处较小尺度湍涡的模拟结果趋近于大涡模拟的结果;重整化群代数湍流模型在对高雷诺数湍流的模拟中表现出耗散模型的特征。     

Numerical investigation of turbulence near a sheared air–water interface. Part 1: Turbulence statistics beneath a flat water surface sheared by wind

Direct numerical simulation (DNS) and large eddy simulation (LES) of turbulent shear flow beneath a flat water surface with imposed wind shear stress are presented. The results of DNS indicate that there are clear differences, and also similarities, between wind-driven flow and the flow near a solid wall. The qualitative structures of turbulence are similar in both types of flow. Low-speed streaks are also present in wind-driven flow. On the other hand, profiles of the mean velocity and turbulence intensities in wind-driven flow are significantly different from those in flow near a solid wall. The differences are attributed to the lack of a viscous sublayer, and to the boundary condition which allows fluctuations of the tangential velocity components at the boundary. LES of the same flow was also carried out to evaluate subgrid-scale models. It was shown that the features of the flow observed in DNS are well simulated by all models tested, and that the discrepancies between DNS and LES with the dynamic mixed model are very small. Received: August 17, 2000 / Accepted: December 22, 2000     

基于CFD方法的6500TEU集装箱船舵空泡腐蚀数值模拟研究

舵的空泡腐蚀研究在船型优化设计和新船型开发中具有重要意义。文章以6 500 TEU集装箱船的NACA0021舵为研究对象,通过对船、桨、舵整体三维建模,运用CFD方法在3D计算域下对舵的非定常空化现象进行数值模拟,得到了与试验比较一致的结果。同时还对改善舵空蚀现象的措施进行了分析。研究表明,通过整体建模的数值模拟方法对舵空泡性能进行预测研究,其结果是合理可信的。     

基于CFD法的对转螺旋桨敞水性能参数匹配研究

摘要：采用雷诺平均纳维-斯托克斯（RANS)法对B型螺旋桨和对转螺旋桨周围的粘性流场进行数值处理,运用Pro/E和GAMBIT软件分别进行三维建模和网格划分,并采用ORIGIN和TECPLOT后处理软件对结果进行图像处理。分析研究湍流模型对螺旋桨水动力性能的影响,对对转桨进行数值计算验证,同时对其敞水性能参数的匹配问题进行探讨,分析其尾流和速度场的变化情况。结果表明：SST 模型为较佳的湍流模型;对转桨在适当的桨距比和直径比的情况下,后桨可充分吸收前桨的尾涡能量,其推进效率明显提高。     

Development of a time domain prediction method for hull pressure fluctuation induced by marine propeller sheet cavitation with consideration of scattering effects

Using a time domain acoustic analogy, we develop a method to predict the sound field and hull pressure fluctuation generated by unsteady sheet cavitation on marine propellers. Formulation 1A of Farassat is introduced to enhance theoretical understanding of this work, and it is applied to modeling the scattered sound field created by the fuselage boundary. To express the direct sound field resulting from sheet cavitation, a new solution is studied which considers the Doppler effect and also separately expresses the near and far fields. A small cube model is used to verify the method. Computed acoustic field pressures around the cube are compared with the boundary element method, and the numerical results show good agreement. Finally, the pressure fluctuation on a ship stern model is calculated.     

Effect of injection angle on artificial cavitation using the design of experiment method

Using the supercavitation phenomenon is necessary to reach high velocities underwater. Supercavitation can be achieved in two ways: natural and artificial. In this article, the simulation of flows around a torpedo was studied naturally and artificially. The validity of simulation using theoretical and practical data in the natural and artificial phases was evaluated. Results showed that the simulations were consistent with the laboratory results. The results in different injection coefficient rates, injection angles, and cavitation numbers were studied. The obtained results showed the importance of cavitation number, injection rate coefficient, and injection angle in cavity shape. At the final level, determining the performance conditions using the Design of Experiment (DOE) method was emphasized, and the performance of cavitation number, injection rate coefficient, and injection angle in drag and lift coefficient was studied. The increase in injection angle in the low injection rate coefficient resulted in a diminished drag coefficient and that in the high injection rate coefficient resulted in an enhanced drag coefficient.     

两艘多用途船的螺旋桨设计研究

以2艘多用途船螺旋桨设计为例，运用螺旋桨理论设计与模型试验为手段，探索了特定条件下加大桨叶后倾角（增加桨叶梢与船底板间隙）、改变螺旋桨叶面积以及增加桨叶侧斜角对诱导脉动压力和效率的影响。结果表明：采用减小空泡裕度增加盘面比的措施，对降低脉动压力的效果最为显著；增大侧斜角措施的效果居中；通过改变后倾角增大叶梢与船底板间隙的措施，降低脉动压力效果相对要小一些。     

Application of large eddy simulation in the performance study of wave blocker

The configuration and aerodynamic performance of the inlet system are important aspects in the process of installing a gas turbine on a naval vessel. Under the requirements, large eddy simulation （LES） is used to simulate the three-dimensional fluid flow in the wave blocker of a marine inlet filter. The Smagorinsky-Lilly sub-grid model was used to model motions of small-scale structures. During numerical simulation, the SIMPLE algorithm was applied. The central-differencing spatial discretization scheme and the second order accuracy finite difference for the temporal discretization were used. Simulation gives satisfactory distribution of the vorticity fields and turbulent kinetic energy. Compared with the k-ε turbulent model, the results of LES are better for the distribution of parameters. The results of experimental study in a small-scale wind tunnel indicate that numerical calculation has higher accuracy. Therefore, the methods used are worthy of reference and introduction for the design of an inlet system.     

非均匀船舶尾流中工作的常规和大侧斜船用螺旋桨的水动力和水声计算预报（英文）

Despite their high manufacturing cost and structural deficiencies especially in tip regions, highly skewed propellers are preferred in the marine industry, where underwater noise is a significant design criterion. However, hydrodynamic performances should also be considered before a decision to use these propellers is made. This study investigates the trade-off between hydrodynamic and hydroacoustic performances by comparing conventional and highly skewed Seiun Maru marine propellers for a noncavitating case.Many papers in the literature focus solely on hydroacoustic calculations for the open-water case. However, propulsive characteristics are significantly different when propeller-hull interactions take place. Changes in propulsion performance also reflect on the hydroacoustic performances of the propeller. In this study, propeller-hull interactions were considered to calculate the noise spectra.Rather than solving the full case, which is computationally demanding, an indirect approach was adopted; axial velocities from the nominal ship wake were introduced as the inlet condition of the numerical approach. A hybrid method based on the acoustic analogy was used in coupling computational fluid dynamics techniques with acoustic propagation methods, implementing the Ffowcs Williams-Hawkings(FW-H) equation. The hydrodynamic performances of both propellers were presented as a preliminary study.Propeller-hull interactions were included in calculations after observing good accordance between our results, experiments, and quasi-continuous method for the open-water case. With the use of the time-dependent flow field data of the propeller behind a nonuniform ship wake as an input, simulation results were used to solve the FW-H equation to extract acoustic pressure and sound pressure levels for several hydrophones located in the near field. Noise spectra results confirm that the highest values of the sound pressure levels are in the low-frequency range and the first harmonics calculated by the present method are in good accordance with the theoretical values. Results also show that a highly skewed propeller generates less noise even in noncavitating cases despite a small reduction in hydrodynamic efficiency.