带扭曲舵船舶自航因子数值预报

为研究扭曲舵的节能效果,以标准船模KVLCC2为对象,设计了合适的扭曲舵,进行基于CFD方法的实船自航因子预报。该文首先以带常规舵的船模为对象进行了船-舵模型阻力试验、螺旋桨模型敞水试验和船-桨-舵模型自航试验数值模拟,通过数值结果与试验结果的对比,验证了数值方法的有效性。然后根据螺旋桨尾部流场设计扭曲舵,进行了带扭曲舵的船-舵模型阻力试验和船-桨-舵模型自航试验数值模拟,基于数值模拟结果,分析得到了实船自航因子,并将其与带普通舵的实船自航因子进行比较;结果表明,所设计的扭曲舵可以较好地提高螺旋桨推进效率,使相同航速下的螺旋桨转速降低,达到期望的节能效果。     

基于CFD方法的船/桨/舵干扰数值模拟

船/桨/舵相互干扰研究在传统船型优化设计和新船型的开发中具有重要意义。应用计算流体力学(CFD)方法对带桨的KCS集装箱船及带桨和舵的KVLCC2油船非稳态粘流场进行了数值模拟,其中船桨舵干扰计算分别采用动量源法、MRF法和滑移网格法,分析研究了各方法及其结果的异同。研究表明不同模拟计算方法均能合理预报出船/桨/舵相互干扰相互作用下速度场和压力场分布等详细流场信息,可用于计算船体阻力、表面压力和桨盘面伴流等。通过这种详细的数值模拟研究,可以更好地理解复杂流动干扰现象。     

水下航行体流场拓扑分析和流动声源辨识

该文对SUBOFF潜艇模型的流场、等效声源场和流体动力声场进行了数值模拟。首先应用CFD软件FLUENT,基于大涡模拟方法计算了高雷诺数下SUBOFF模型绕流场;然后应用自编的流动结构拓扑分析计算程序,基于临界点和特征方程共轭复数解判据,对涡流场拓扑结构做出了显示和分析;最后应用声学软件ACTRAN,基于CFD/CHA多步骤混合方法,模拟了等效声源场和声场。     

基于RANS方程的舟桥水阻力预报

本文采用RANS方程及VOF模型计算绕舟桥的自由表面粘性流动。计算中使用RNGκ-ε湍流模型结合非平衡壁面函数，自由液面的确定采用几何重建方法。讨论了数值计算中网格质量、时间步长对阻力预报结果的影响。计算结果与实验值的比较显示，只要合理地划分网格并选择恰当的控制参数，数值计算方法可以辅助实验方法，用于舟桥水动力性能的预报。     

限制水域内船-桨-舵一体螺旋桨轴承力数值研究

为了探究浅水及岸壁效应影响下船-桨-舵一体自航时螺旋桨的轴承力,该文通过求解RANS方程,采用计算流体力学商业软件STAR-CCM+,对船-桨-舵一体在限制水域内自航进行了数值模拟。采用滑移网格技术来模拟螺旋桨的旋转,首先对船-舵一体阻力和船-桨-舵一体自航进行了验证,证明了数值和网格划分方法的可行性;然后对无限水域以及不同的受限水域四个工况进行了螺旋桨非定常轴承力的数值模拟。研究表明:随着水深和船-岸距离的同时减小,推力系数K_(Tx)和扭矩系数K_(Qx)均逐渐增大,非定常轴承力系数各分量随时间周期性变化;各系数在频域上脉动频率相同,其中K_(T x)和K_(Qy)的频率脉动峰值波动最大。此外,BPF、2BPF和3BPF脉动幅值随着水深和船-岸距离的减小呈现出不同的变化规律。     

AU5-65螺旋桨紧急倒车工况流场与涡流噪声数值模拟研究

该文利用大涡模拟(LES)与FW-H声学类比方法对AU5-65螺旋桨第一象限(前进正车)和第三象限(紧急倒车)下的流场与涡流噪声进行了数值模拟研究。在规范的网格收敛性分析和亚格子涡模型影响性分析的基础上，采用1 063万网格与SL亚格子涡模型，首先对螺旋桨敞水第一和第三象限不同进速下的流场与水动力性能展开了计算分析，并通过相关试验数据校验了计算方法的可靠性，将不同工况与不同进速系数下的瞬态流场、桨叶切面压力和涡旋结构演化等结果进行了对比分析；在此基础上，结合FW-H方程对AU5-65桨敞水正车前进与紧急倒车时涡流噪声频谱进行了计算分析，探讨了紧急倒车工况下的螺旋桨涡流噪声幅值与频率特征。研究结果表明，该文建立的数值计算方法适用于螺旋桨紧急倒车工况下的流动与噪声模拟。     

基于VOF模型的团山子溢流坝数值模拟

本文介绍了VOF 模型,结合k-ε紊流模型,利用Fluent软件数值求解了带自由水面的二维水流流动问题。以团山子水利枢纽为例,计算了溢流坝内水流流动特性,并将计算结果与实验数据进行对比,结果表明计算值与实测值吻合较好,说明VOF 模型能够精确地跟踪自由表面,可利用数值模拟对泄水建筑物设计方案比选,结合模型试验的方法,研究其水力特性。     

基于CFD技术的导管螺旋桨自动优化设计技术研究

该文开发了一种基于定常计算的导管螺旋桨自动优化设计技术.该方法综合了导管桨桨叶、导管及桨毂的几何生成、网格自动划分、优化算法和CFD分析等技术,有助于将螺旋桨理论计算推广到设计阶段.文中采用该方法计算某导管螺旋桨的改造,并与试验结果进行了比较,验证了其效果.计算结果显示,优化后的导管桨可以提供更高的推力和效率.     

小水线面双体船后螺旋桨非定常力特性研究

螺旋桨作为船舶主要振源,其非定常性能的研究对于船舶噪声和振动的控制意义重大。该文采用滑移网格技术,基于分离涡模拟方法(DES),对带首尾鳍船桨一体模型开展了螺旋桨非定常力的数值计算,研究了小水线面双体船后螺旋桨的非定常力特性,并通过与试验结果的对比考察了数值计算方法的精度。计算结果表明,螺旋桨受到的三向力和力矩均有明显的叶频特性,其中推力脉动幅值和水平弯矩脉动幅值较大;此外,分析得出了脉动压力和脉动压力幅值在船体表面局部范围内的分布规律,并将多个测点的脉动压力一阶和二阶叶频幅值与试验测量值对比,其中一阶叶频结果与试验值吻合良好。     

动态PMM实验的数值模拟及线性导数获取方法

PMM (Planar Motion Mechanism)是一种可以较为全面分析水面水下航行体水动力导数的实验机构。该文基于非定常RANS方程和Realizedk-ε湍流模式,并结合重叠网格技术对SUBOFF潜艇动态PMM实验中的纯首摇运动进行数值模拟,获取纯首摇运动中的水动力,并根据多工况结果进行过原点线性拟合处理,获取水动力线性导数。重点针对文献中PMM运动的数值模拟在线性导数的处理方法上存在的问题,详细给出获取线性导数的途径,并提出PMM运动的数值模拟在研究水下低速作业潜器水动力特性方面的优势。     

Numerical simulation of hull/propeller interaction of submarine in submergence and near surface conditions简

Hull/propeller interaction is of great importance for powering performance prediction. The features of hull/propeller interaction of a submarine model with a high-skew five blade propeller in submergence and near surface conditions are numerically simulated. The effect of propeller rotation is simulated by the sliding mesh technique. Free surface is captured by the volume of fluid （VOF） method. Computed results including resistance, thrust, torque and self-propulsion factor are compared with experimental data. It shows fairly good agreement. The resistance and wave pattern of the model at different depths of submergence are computed. And the thrust, torque and self-propulsion factor of the model in submergence and near surface condition are compared to analyze the effect of free surface on self-propulsion performance. The results indicate that free surface has more influence on resistance than that on self-propulsion factors.     

Numerical prediction of effective wake field for a submarine based on a hybrid approach and an RBF interpolation

A hybrid approach coupled with a surface panel method for the propeller and a Reynolds averaged Navier-Stokes(RANS) model for the hull with the propeller body forces are presented for predicting the self-propulsion performance and the effective wake field of underwater vehicles. To achieve a high accuracy and simplicity, a radial basis function(RBF) based approach is proposed for mapping the force field from the blade surface panels to the RANS model. The effective wake field is evaluated in two ways, i.e., by extrapolation from the flat planes upstream of the propeller disk, and by direct computation in a curved surface upstream of and parallel to the blade leading edges. The hull-propeller system of a real propeller geometry is further simulated with the sliding mesh model to numerically verify the hybrid approach. Numerical simulations are conducted for the fully appended SUBOFF submarine model. The high accuracy of the RBF-based interpolation scheme is confirmed, and the effective wake fraction predicted by the hybrid approach is found consistent with that obtained by the sliding mesh model. The effective wake fractions predicted by the two methods are, respectively, 4.6% and 3% larger than the nominal one.     

Numerical estimation of bank-propeller-hull interaction effect on ship manoeuvring using CFD method

This paper presents a numerical investigation of ship manoeuvring under the combined effect of bank and propeller. The incompressible turbulent flow with free surface around the self-propelled hull form is simulated using a commercial CFD software(ANSYS-FLUENT). In order to estimate the influence of the bank-propeller effect on the hydrodynamic forces acting on the ship, volume forces representing the propeller are added to Navier-Stokes equations. The numerical simulations are carried out using the equivalent of experiment conditions. The validation of the CFD model is performed by comparing the numerical results to the available experimental data. For this investigation, the impact of Ship-Bank distance and ship speed on the bank effect are tested with and without propeller. An additional parameter concerning the advance ratio of the propeller is also tested.     

An integral calculation approach for numerical simulation of cavitating flow around a marine propeller behind the ship hull

In this paper, the unsteady cavitating turbulent flow around a marine propeller is simulated based on the unsteady Reynolds averaged Navier-Stokes(URANS) with emphasis on the hull-propeller interaction by an integral calculation approach, which means the propeller and hull are treated as a whole when the cavitating flow is calculated. The whole calculational domain is split to an inner rotating domain containing a propeller and an outer domain containing a hull. And the two split sections are connected together in ANSYS CFX by using the GGI interfaces and the transient rotor stator frame change/mixing model. The alternate rotation model is employed for the advection term in the momentum equations in order to reduce the numerical error. Comparison of predictions with measurements shows that the propeller thrust coefficient can be predicted satisfactorily. The unsteady cavitating flow around the propeller behind the ship hull wake shows quasi-periodic features including cavity inception, growth and shrinking. These features are effectively reproduced in the simulations which compare well to available experimental data. In addition, significant pressure fluctuations on the ship hull surface induced by the unsteady propeller cavitation are compared with experimental data at monitoring points on the hull surface. The predicted amplitudes of the first components corresponding to the first blade passing frequencies match well with the experimental data. The maximum error between the predictions and the experimental data for the pressure pulsations is around 8%, which is acceptable in most engineering applications.     

基于CFD的船-舵水动力干扰数值研究

该文采用基于RANS方程求解的CFD方法,对匀速直航的船-舵系统的黏性绕流场进行数值模拟,计算了不同船速和不同舵角下的船-舵水动力干扰系数,计算中忽略了自由面兴波及螺旋桨的影响。文中以KVLCC1船、舵模型为研究对象,首先将数值计算的船舶水动力及船-舵水动力干扰系数结果与模型试验数据进行比较,验证了所采用数值方法的有效性;随后,对船-舵系统、裸船体和敞水舵分别进行计算,通过水动力计算结果的比较以及流场分析,对船-舵水动力相互作用进行了数值研究。     

The method to control the submarine horseshoe vortex by breaking the vortex core

The quality of the inflow across the propeller is closely related with the hydrodynamic performance and the noise characteristics of the propeller. For a submarine, with a horseshoe vortex generated at the junction of the main body and the appendages, the submarine wake is dominated by a kind of highly non-uniform flow field, which has an adverse effect on the performance of the submarine propeller. In order to control the horseshoe vortex and improve the quality of the submarine wake, the flow field around a submarine model is simulated by the detached eddies simulation （DES） method, and the vortex configuration is displayed using the second invariant of the velocity derivative tensor. The state and the transition process of the horseshoe vortex are analyzed, then a modified method to break the vortex core by a vortex baffle is proposed. The flow numerical simulation is carried out to study the effect of this method. Numerical simulations show that, with the breakdown of the vortex core, many unstable vortices are shed and the energy of the horseshoe vortex is dissipated quickly, and the uniformity of the submarine wake is improved. The submarine wake test in a wind tunnel has verified the effect of the method to control the horseshoe vortex. The vortex baffle can improve the wake uniformity in cases of high Reynolds numbers as well, and it does not have adverse effects on the maneuverability and the speed ability of the submarine.     

NUMERICAL SIMULATION AND EXPERIMENTAL STUDY OF THE NEW METHOD OF HORSESHOE VORTEX CONTROL

The horseshoe vortex generated around the sail-body junction of a submarine has an important influence on the uniformity of the submarine wake at the propeller disc. In this article, the horseshoe vortex is simulated by the Detached Eddy Simulation (DES) method, and a new method to control the horseshoe vortex by vortex control baffler is proposed. The numerical simulation shows that a kind of attached vortex, with the rotation direction opposite to that of horseshoe vortex, is generated by the vortex control baffler. With the attached vortex, the strength of the horseshoe vortex is significantly reduced. The wind tunnel experiment on a submarine model is carried out, and the axial velocities at the propeller disc of the submarine with and without vortex control baffler are measured by a hot wire anemometer system. It is shown from the experimental results that the vortex control baffler can enhance the uniformity of the wake at the propeller disc, which helps to improve the propeller performance. The engineering applicability of the vortex control baffler is discussed.     

NUMERICAL PREDICTION OF PROPELLER EXCITED ACOUSTIC RESPONSE OF SUBMARINE STRUCTURE BASED ON CFD,FEM AND BEM

A mesh-less Refined Integral Algorithm (RIA) of Boundary Element Method (BEM) is proposed to accurately solve the Helmholtz Integral Equation (HIE).The convergence behavior and the practicability of the method are validated.Computational Fluid Dynamics (CFD),Finite Element Method (FEM) and RIA are used to predict the propeller excited underwater noise of the submarine hull structure.Firstly the propeller and submarine’s flows are independently validated,then the self propulsion of the "submarine+propeller" system is simulated via CFD and the balanced point of the system is determined as well as the self propulsion factors.Secondly,the transient response of the "submarine+ propeller" system is analyzed at the balanced point,and the propeller thrust and torque excitations are calculated.Thirdly the thrust and the torque excitations of the propeller are loaded on the submarine,respectively,to calculate the acoustic response,and the sound power and the main peak frequencies are obtained.Results show that:(1) the thrust mainly excites the submarine axial mode and the high frequency area appears at the two conical-type ends,while the torque mainly excites the circumferential mode and the high frequency area appears at the broadside of the cylindrical section,but with rather smaller sound power and radiation efficiency than the former,(2) the main sound source appears at BPF and 2BPF and comes from the harmonic propeller excitations.So,the main attention should be paid on the thrust excitation control for the sound reduction of the propeller excited submarine structure.