水翼部分空化流动二维数值仿真研究（英文）

In the present study, a new approach is applied to the cavity prediction for two-dimensional(2D) hydrofoils by the potential based boundary element method(BEM). The boundary element method is treated with the source and doublet distributions on the panel surface and cavity surface by the use of the Dirichlet type boundary conditions. An iterative solution approach is used to determine the cavity shape on partially cavitating hydrofoils. In the case of a specified cavitation number and cavity length, the iterative solution method proceeds by addition or subtraction of a displacement thickness on the cavity surface of the hydrofoil. The appropriate cavity shape is obtained by the dynamic boundary condition of the cavity surface and the kinematic boundary condition of the whole foil surface including the cavity. For a given cavitation number the cavity length of the 2D hydrofoil is determined according to the minimum error criterion among different cavity lengths, which satisfies the dynamic boundary condition on the cavity surface. The NACA 16006, NACA 16012 and NACA 16015 hydrofoil sections are investigated for two angles of attack. The results are compared with other potential based boundary element codes, the PCPAN and a commercial CFD code(FLUENT). Consequently, it has been shown that the results obtained from the two dimensional approach are consistent with those obtained from the others.     

基于混合迭代法的二维水翼空泡性能分析(英文)

In order to study cavitation characteristics of a 2-D hydrofoil, the method that combines nonlinear cavitation model and mixed-iteration is used to predict and analyze the cavitation performance of hydrofoils. The cavitation elements are nonlinearly disposed based on the Green formula and perturbation potential panel method. At the same time, the method that combines cavity shape for fixed cavity length (CSCL) iteration and cavity shape for fixed cavitation number (CSCN) iteration is used to work out the thickness and length of hydrofoil cavitations. Through analysis of calculation results, it can be concluded that the jump of pressure and velocity potentially exist between cavitation end area and non-cavitations area on suction surface when cavitation occurs on hydrofoil. In certain angles of attack, the cavitation number has a negative impact on the length of cavitations. And under the same angle of attack and cavitation number, the bigger the thickness of the hydrofoil, the shorter the cavitations length.     

The effect of finite depth on 2D and 3D cavitating hydrofoils

The iterative numerical method that has been developed for cavitating hydrofoils and surface piercing bodies moving inside a numerical towing tank is modified and extended to the case of fully submerged, both two- and three-dimensional cavitating hydrofoils in water of finite depth, and the effects of subcritical speed, critical speed and supercritical speed are investigated in detail. The iterative numerical method based on Green’s theorem allows separating the cavitating hydrofoil problem, the free surface problem and finite bottom problem both in two and three dimensions. The cavitating hydrofoil surface, the free surface and the surface of finite bottom are modeled with constant strength dipole and constant strength source panels. While the kinematic boundary condition is applied on the hydrofoil surface, a dynamic condition is applied with a cavity closure condition on the cavity surface. The source strengths on the free surface are expressed in terms of perturbation potential by applying the linearized free surface conditions. No radiation condition is enforced for downstream and transverse boundaries. The source strengths on the bottom surface are zero because of vanishing normal velocity. The method is applied to 2D and 3D cavitating hydrofoils, and the effect of finite bottom on lift and drag coefficients, cavity number and wave elevation is investigated.     

局部空泡水翼性能研究

空泡对水翼的水动力特性具有重要的影响,使用数值模拟方法研究空泡特性及其机理有着广泛的工程应用价值。对二维NACA翼型的模拟结果表明,基于势流理论的边界元积分方法适用于局部空泡水翼的性能研究,翼型几何参数变化对空泡长度和升力性能均有显著影响,在水翼设计与使用过程中必须对空泡发生与变化给予充分关注。     

涂层对空化流动特性影响的实验研究

利用实验的方法研究了涂层对绕水翼空化流动特性的影响。分别针对喷涂环氧涂层和氟碳涂层的 Clark-Y 型水翼,采用高速摄像装置观察了不同空化阶段的空化流动形态。研究结果表明：（1）在初生空化阶段,当σ=1.82时,沿环氧涂层水翼表面展向排列着初生空泡,而氟碳涂层水翼还处于无空化状态,说明相对于环氧涂层,氟碳涂层对空化现象的产生有一定的抑制作用,氟碳涂层水翼初生空化数为1.50;（2）在片状附着型阶段,当σ小于1.63时,绕环氧涂层水翼的空化先于氟碳涂层水翼发展至片状空化,绕水翼空化流动产生大量分散空泡,沿水翼表面向后运动过程中逐渐长大,在高压区溃灭后形成小空泡并以马蹄涡形式继续运动。同一空化数下,绕环氧涂层水翼空化流动的空泡长度大于氟碳涂层水翼。但随空化数降低,两者空泡长度逐渐接近,说明环氧涂层在片状空化阶段对空化的抑制作用逐渐增强;（3）σ=0.87时空化发展至云状空化阶段,空化流动伴随周期性的云状空泡的脱落,绕环氧涂层水翼的空化流动周期及无量纲空化面积均小于氟碳涂层水翼,说明涂层对空化的非定常变化也有一定的抑制作用,且环氧涂层强于氟碳涂层。     

用等压Kutta条件求解三维水翼和螺旋桨片空泡

由于空泡计算的复杂性,国内外以前计算螺旋桨空泡时大多采用的是Morino's Kutta条件,但严格来说,Morino's Kutta只适用二维问题,对三维水翼和螺旋桨空泡的计算会带来一定误差,而等压Kutta条件用Newton-Raphson迭代过程,确保在螺旋桨随边上下表面的压力相等,可以消除Mofino's Kuaa条件所带来的误差,提高空泡在梢部的预报精度.文中用等压Kutta条件预报了三维水翼和螺旋桨的片空泡,并将两种Kutta条件得到的计算结果同试验结果进行了比较.     

厚翼剖面的空泡特性研究

本文用奇点法解厚翼剖面局部空泡绕流问题。求解时精确考虑了空泡表面是一条流线的运动学边界条件,空泡表面压力为常数的动力学边界条件,以及水翼湿表面是一条流线的运动学边界条件,用迭代法求出了空泡表面的形状、压力分布等水动力特性,并与实验结果作了比较,得较好结果。     

振动翼推进性能计算及试验研究

采用非定常边界元法基于格林定理构建振动翼计算模型,讨论相关的构建过程、程序结构;采用时变尾涡面和时间步进法在时域中处理振动翼的尾涡存储效应,在尾涡面上应用等压Kutta条件并通过New-ton-Raphson法进行迭代求解,对在无限域中的振动翼水动力特性进行计算和研究;通过数值计算结果与试验数据对比,证实本方法的有效性。     

解三维水翼绕流的下潜涡环栅格法

在包含于机翼表面内的某次表面及尾涡面上分布法向偶极子,在翼面上满足物面边界条件,建立了解三维机翼绕流的下潜涡环栅格法.考虑到非线性的自由液面边界条件,用下潜涡环栅格法求解水翼绕流问题.通过算例验证了方法的正确性和程序的可靠性.本方法可用于水翼及水下安定翼和各种舵的水动力计算.     

Hydrodynamic response of a passive shape-adaptive composite hydrofoil

The primary objective of this paper is to present cavitation tunnel tests performed on an optimised shape-adaptive composite hydrofoil and compare the results to other composite hydrofoils. The optimised composite hydrofoil was designed based on prior literature and was manufactured using an optimised ply orientation schedule and a pre-twist. In the same experiment schedule a composite hydrofoil that has a ply orientation that is opposite to the optimised hydrofoil was also tested. In addition to the cavitation tunnel experiments, the paper also presents results predicted from FEA and CFD simulations for the optimised hydrofoil and compares the results from numerical methods to experiments. The results show that the optimised hydrofoil has an improved L/D ratio and a delayed stall phenomenon compared to other hydrofoils. Furthermore, due to the pre-twisted optimised geometry, the hydrofoil does not suffer from loss of lift at low angles of attack. The experimental results demonstrated the importance of characterising the performance of flexible shape-adaptive hydrofoils based on the actual velocity of the flow in addition to the conventional characterisation based on Reynold's number. Additional numerical simulations were performed to investigate the hydrofoils observed load dependant deformation behaviour. These results clearly show that for the same Reynold's number, the hydrofoil can have an appreciably different response if the flow velocity is different.     

基于HydroSTAR的水翼五体船耐波性优化研究

为改善五体船在空载及小摇荡时的耐波性,论文通过在五体船主船体和片体之间加装水翼构造水翼五体船,在此基础上借助耐波性通用软件HydroSTAR对不同水翼攻角水翼五体船及原五体船耐波性计算,并对相关耐波性指标进行对比分析,以此研究水翼五体船的攻角优化问题.通过对比研究发现,水翼五体船的纵摇幅值、横摇幅值及垂荡幅值明显低于五体船,且在低频波段NACA4415翼型水翼五体船最优攻角在10°左右.     

基于均相流输运模型的二维水翼空化模拟

基于均相流输运模型对NACA661-012型水翼进行了空化数值模拟,计算了不同空化数K和不同攻角α下的升力系数与阻力系数.从流场、压力场和边界层的变化分析了空化的产生发展对水翼升力和阻力的影响.当攻角α大于8°以后,空化流动的不稳定性增强,空泡呈现出周期性的生长溃灭,并伴有升力系数和阻力系数的周期性波动.计算结果与实验进行了对比,结果吻合较好.     

Numerical analysis of cavitating propeller and pressure fluctuation on ship stern using a simple surface panel method “SQCM”

This paper presents a calculation method for the pressure fluctuation induced by a cavitating propeller. This method consists of two steps: the first step is the calculation of propeller sheet cavitation, and the second step is the calculation of pressure fluctuation on the ship stern. It is for practicality that we divide the method into two steps but do not calculate these steps simultaneously. This method is based on a simple surface panel method “SQCM” which satisfies the Kutta condition easily. The SQCM consists of Hess and Smith type source panels on the propeller or cavity surface and discrete vortices on the camber surface according to Lan’s QCM (quasi-continuous vortex lattice method). In the first step, the cavity shape is solved by the boundary condition based on the free streamline theory. In order to get the accurate cavity shape near the tip of the propeller blade, the cross flow component is taken into consideration on the boundary condition. In the second step, we calculate the cavitating propeller and the hull surface flow simultaneously so as to calculate the pressure fluctuation including the interaction between the propeller and the hull. At that time, the cavity shape is changed at each time step using the calculated cavity shape gotten by the first step. Qualitative agreements are obtained between the calculated results and the experimental data regarding cavity shape, cavity volume and low order frequency components of the pressure fluctuation induced by the cavitating propeller.     

高速轻型穿浪双体船纵向运动改善措施研究

针对在改善高速轻型穿浪双体船(WPC)迎浪中波长与船长接近时纵向运动幅度较大的缺点,采用了理论计算与模型试验相结合的方法,对250 t级穿浪双体船开展了水翼改善纵向运动的理论和试验研究,分析了水翼形式、尺度和安装位置等对纵向运动的影响规律。数值计算和试验结果的比较表明,计及水翼—船体水动力干扰影响的切片理论可满足WPC加水翼后波浪中纵向运动计算的需要,但在纵向运动响应峰值处数值计算结果偏高。模型试验表明,250 t级WPC加装水翼后,迎浪纵摇和垂荡有义幅值可减少20%～30%。     

Cavitation passive control on immersed bodies

This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator (ACG). Cyclic processes, namely, growth and implosion of bubbles around an immersed body, are the main reasons for the destruction and erosion of the said body. This paper aims to create a condition in which the cavitation bubbles reach a steady-state situation and prevent the occurrence of the cyclic processes. For this purpose, the ACG is placed on the surface of an immersed body, in particular, the suction surface of a 2D hydrofoil. A simulation was performed with an implicit finite volume scheme based on a SIMPLE algorithm associated with the multiphase and cavitation model. The modified k-ε RNG turbulence model equipped with a modification of the turbulent viscosity was applied to overcome the turbulence closure problem. Numerical simulation of water flow over the hydrofoil equipped with the ACG shows that a low-pressure recirculation area is produced behind the ACG and artificially generates stationary cavitation bubbles. The location, shape, and size of this ACG are the crucial parameters in creating a proper control. Results show that the cavitation bubble is controlled well with a well-designed ACG.     

基于MSC.Patran的水翼升力求解方法研究

根据已有的水翼升力面理论计算方法及成果,对水翼模型进行部分简化,并借助MSC.Patran实现了水翼模型和流场计算域的参数化建模,设置边界和工况后,对水翼航行中的升力使用有限元法进行迭代求解。与已有规律和试验结果对比表明,使用参数化建模和有限元法可以计算出水翼的升力以及自由面的形变数据。不仅减少了手工劳动,而且预报了水翼的升力及分布。     

计及叶片载荷的双机对转式海流发电机系泊系统动力分析

本文设计了一种新型的双机对转式海流发电机并对其系泊系统与叶片载荷和直径关系进行模拟分析。首先将单机式海流发电机与已有研究进行对比验证其可靠性，然后在不改变系泊方式的前提下，设计出双机式结构，并通过分析机身位移和旋转比较两种系统的稳定性。为考虑叶片载荷对系泊系统影响，在Orcaflex中对不同精细程度的叶片进行建模，分别对比单一翼型/三翼型/九翼型的数值模拟结果。接着使用M-BEMT软件优化后的翼型参数，对比使用原始升阻力系数的三翼型发电机的模拟结果，同时将使用不同直径叶片的发电机系统进行对比，说明双机式发电机的稳定性更优，对海流发电机及其系泊系统的设计提供重要参考价值。     

基于翼剖面改型的空化抑制

为提高水翼抗空化的性能,对二维翼型的吸力面外形进行适当改造。首先通过数值计算对稳态无空化流场和稳态空化流场进行模拟,计算所得的吸力面压力系数与实验值吻合良好,验证了模型的可行性。在此基础上,采取基于阻碍回射流从而控制空化的思路,在翼型吸力面上设置微小方形凸起,并提出设置拱弧的新方案。通过对原翼型及两种改型的空化流场瞬态模拟,对比了不同时刻各模型气体体积分数云图所反映出的翼面空化程度差异。计算结果验证了阻流体对云状空化的抑制作用,同时表明设置拱弧阻流体的效果比方形阻流体好。     

二维水翼型空化流的数值计算(英文)

In order to predict the effects of cavitation on a hydrofoil, the state equations of the cavitation model were combined with a linear viscous turbulent method for mixed fluids in the computational fluid dynamics (CFD) software FLUENT to simulate steady cavitating flow. At a fixed attack angle, pressure distributions and volume fractions of vapor at different cavitation numbers were simulated, and the results on foil sections agreed well with experimental data. In addition, at the various cavitation numbers, the vapor fractions at different attack angles were also predicted. The vapor region moved towards the front of the airfoil and the length of the cavity grew with increased attack angle. The results show that this method of applying FLUENT to simulate cavitation is reliable.     

一种计算水翼水动力的三维面元法

本文用Rankine奇点面元法计算了深、浅水中三维水翼的定常升力绕流。水翼的厚度和升力效应分别以水翼表面分布的Rankine源和法向偶极子来模拟，在自由表面上也分布Rankine源，通过满足相应的边界条件和尾缘处的Kutta条件求出这些奇点强度。以在自由表面下作小攻角定常运动的水翼为例进行了计算，计算结果与试验结果和其他计算结果作了比较。