Numerical Study on Flow Around Modern Ship Hulls with Rudder-Propeller Interactions

Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades,extensive studies were carried out on the flow around ship hull, it is still difficult to calculate the flow around the hull while considering propeller interaction. In this paper, the viscous flow around modern ship hulls is computed considering propeller action. In this analysis, the numerical investigation of flow around the ship is combined with propeller theory to simulate the hull-propeller interaction. Various longitudinal positions of the rudder are also analyzed to determine the effect of rudder position on propeller efficiency. First, a numerical study was performed around a bare hull using Shipflow computational fluid dynamics(CFD) code to determine free-surface wave elevation and resistance components.A zonal approach was applied to successively incorporate Bpotential flow solver^ in the region outside the boundary layer and wake, Bboundary layer solver^ in the thin boundary layer region near the ship hull, and BNavier-Stokes solver^in the wake region. Propeller open water characteristics were determined using an open-source MATLAB code Open Prop, which is based on the lifting line theory, for the moderately loaded propeller. The obtained open water test results were specified in the flow module of Shipflow for self-propulsion tests. The velocity field behind the ship was recalculated into an effective wake and given to the propeller code that calculates the propeller load. Once the load was known, it was transferred to the Reynolds-averaged Navier-Stokes(RANS) solver to simulate the propeller action. The interaction between the hull and propeller with different rudder positions was then predicted to improve the propulsive efficiency.

Propeller Torque Load and Propeller Shaft Torque Response Correlation During Ice-propeller Interaction

Ships use propulsion machinery systems to create directional thrust. Sailing in ice-covered waters involves the breaking of ice pieces and their submergence as the ship hull advances. Sometimes, submerged ice pieces interact with the propeller and cause irregular fluctuations of the torque load. As a result, the propeller and engine dynamics become imbalanced, and energy propagates through the propulsion machinery system until equilibrium is reached. In such imbalanced situations, the measured propeller shaft torque response is not equal to the propeller torque. Therefore, in this work, the overall system response is simulated under the ice-related torque load using the Bond graph model. The energy difference between the propeller and propeller shaft is estimated and related to their corresponding mechanical energy. Additionally, the mechanical energy is distributed among modes. Based on the distribution, kinetic and potential energy are important for the correlation between propeller torque and propeller shaft response.

A Numerical and Experimental Study on the Hull-Propeller Interaction of A Long Range Autonomous Underwater Vehicle

Range is an important factor to the design of autonomous underwater vehicles (AUVs), while drag reduction efforts are pursued, the investigation of body-propeller interaction is another vital consideration. We present a numerical and experimental study of the hull-propeller interaction for deeply submerged underwater vehicles, using a proportional-integral- derivative (PID) controller method to estimate self-propulsion point in CFD environment. The hydrodynamic performance of hull and propeller at the balance state when the AUV sails at a fixed depth is investigated, using steady RANS solver of Star-CCM+. The proposed steady RANS solver takes only hours to reach a reasonable solution. It is more time efficient than unsteady simulations which takes days or weeks, as well as huge consumption of computing resources. Explorer 1000, a long range AUV developed by Shenyang Institute of Automation, Chinese Academy of Sciences, was studied as an object, and self-propulsion point, thrust deduction, wake fraction and hull efficiency were analyzed by using the proposed RANS method. Behind-hull performance of the selected propeller MAU4-40, as well as the hull-propeller interaction, was obtained from the computed hydrodynamic forces. The numerical results are in good qualitative and quantitative agreement with the experimental results obtained in the Qiandao Lake of Zhejiang province, China.

CFD simulation of propeller and rudder performance when using additional thrust fins

To analyse a possible way to improve the propulsion performance of ships,the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted with additional thrust fins in the viscous flow field.The computational fluid dynamics software FLUENT was used to simulate the thrust and torque coefficient as a function of the advance coefficient of propeller and the thrust efficiency of additional thrust fins. The pressure and velocity flow behind the propeller was calculated. The geometrical nodes of the propeller were constituted by FORTRAN program and the NUMBS method was used to create a configuration of the propeller,which was then used by GAMMBIT to generate the calculation model. The thrust efficiency of fins was calculated as a function of the number of additional fins and the attack angles. The results of the calculations agree fairly well with experimental data,which shows that the viscous flow solution we present is useful in simulating the performance of propellers and rudders with additional fins.

Hydrodynamic Performance Analysis of Propeller-rudder System with the Rudder Parameters Changing

In order to study the effects of geometric parameters of the rudder on the hydrodynamic performance of the propeller-rudder system,the surface panel method is used to build the numerical model of the steady interaction between the propeller and rudder to analyze the relevant factors.The interaction between the propeller and rudder is considered through the induced velocities,which are circumferentially averaged,so the unsteady problem is translated to steady state.An iterative calculation method is used until the hydrodynamic performance converges.Firstly,the hydrodynamic performance of the chosen propeller-rudder system is calculated,and the comparison between the calculated results and the experimental data indicates that the calculation program is reliable.Then,the variable parameters of rudder are investigated,and the calculation results show that the propeller-rudder spacing has a negative relationship with the efficiency of the propeller-rudder system,and the rudder span has an optimal match range with the propeller diameter.Futhermore,the rudder chord and thickness both have a positive correlation with the hydrodynamic performance of the propeller-rudder system.

Numerical Evaluation of Rudder Performance Behind a Propeller in Bollard Pull Condition

Correct evaluation of rudder performance is a key issue in assessing ship maneuverability.This paper presents a simplified approach based on a viscous flow solver to address propeller and rudder interactions.Viscous flow solvers have been applied to this type of problems,but the large computational requests limit(or even prevent)their application at a preliminary ship design stage.Based on this idea,a simplified approach to include the propeller effect in front of the rudder is considered to speed up the solution.Based on the concept of body forces,this approach enables sufficiently fast computation for a preliminary ship design stage,therebymaintaining its reliability.To define the limitations of the proposed procedure,an extensive analysis of the simplified method is performed and the results are compared with experimental data presented in the literature.Initially,the reported results show the capability of the body-force approach to represent the inflow field to the rudder without the full description of the propeller,also with regard to the complex bollard pull condition.Consequently,the rudder forces are satisfactorily predicted at least with regard to the lift force.However,the drag force evaluation ismore problematic and causes higher discrepancies.Nevertheless,these discrepancies may be accepted due to their lower influence on the overall ship maneuverability performance.

Numerical Simulation of Transverse Jet Interaction with Rudders in Supersonic Free Stream for Simplified Missile

Numerical simulation is carried out for jets arranged at 7 different positions for the same model and compared with non-jet flows.The total and rudder force and moment amplification is calculated and analyzed by the pressure distribution on the surface and rudders of the simplified missile.Numerical results show that interactions take great effect on the configuration of the flow field around rudders and the pressure distribution on the missile surface.

Thrust Allocation Optimization in Dynamic Positioning Vessels with Main PropellerRudders

In order to deal with the chattering of rudder angle and the problem of non-convex attainable thrust regions,introduce the concept of dynamic attainable region for each thruster and rudder to limit the thruster rotational speed and the rudder angle,and decompose the thrust allocation optimization problem into several optimization sub-problems.The optimization sub-problems were solved by particle swarm optimization(PSO) algorithm.Simulation studies with comparisons on a model ship were carried out to illustrate the effectiveness of the proposed thrust allocation optimization method.

Dynamic Analysis of the Seafloor Pilot Miner Based on Single-Body Vehicle Model and Discretized Track-Terrain Interaction Model

In order to achieve the complex dynamic analysis of the self-propelled seafloor pilot miner moving on the seafloor of extremely cohesive soft soil and further to make it possible to integrate the miner system with some subsystems to form the complete integrated deep ocean mining pilot system and perform dynamic analysis, a new method for the dynamic modeling and analysis of the miner is proposed and developed in this paper, resulting in a simplified 3D single-body vehicle model with three translational and three rotational degrees of freedom, while the track-terrain interaction model is built by partitioning the track-terrain interface into discrete elements with parameterized force dements built on the theory of terramechanics acting on each discrete dement. To evaluate and verify the correctness and effectiveness of this new modeling and analysis method, typical comparative studies with regard to computational efficiency and solution accuracy are carried out between the traditional modeling method of building the tracked vehicle as a multi-body model and the new modeling method. In full consideration of the particMar structure design of the pilot miner, the special characteristics of the seafioor soil and the hydrodynamic force of near-seafloor currnt, the dynamic simulation analysis of the miner is performed and discussed, which can provide useful guidance and reference for the practical miner system in design and operation. This new method can not only realize the rapid dynamic simulation analysis of the miner but also make possible the integration and rapid dynamic analysis of the complete integrated deep ocean mining pilot system in further researches.

不同航速下螺旋桨对船舶操纵水动力的影响研究

通过数学模型进行船舶操纵性预报是常用的方法,以往的约束模试验通常仅在设计航速下进行,且MMG船舶操纵运动模型通常认为螺旋桨对船舶操纵水动力的影响可以忽略。但船舶在实际操纵运动的过程中航速会发生很大变化,螺旋桨对船舶操纵水动力的影响可能变得不可忽略,因此有必要开展相关船舶操纵水动力的研究。以KVLCC2为研究对象,对其裸船体、船-舵、船-桨和船-桨-舵系统分别进行不同航速下的约束模试验数值模拟,研究了不同航速下螺旋桨对船舶操纵水动力的影响。研究结果表明:螺旋桨对船舶操纵水动力的影响不可忽略,该影响随着船舶航速的减小而增大,但舵的存在会减弱其影响;螺旋桨对舵效有着较大影响,该影响随着船舶航速的减小也会明显增大。因此在进行船舶操纵性研究时,有必要进行非设计航速下的相关约束模试验。

船用复合材料螺旋桨稳态流固耦合尺度效应数值研究

为实现实尺度复合材料螺旋桨的流固耦合性能预报,针对船用复合材料螺旋桨在均匀流场中稳态流固耦合的尺度效应问题,本文基于Ansys Workbench建立了双向流固耦合算法,采用ACP模块对3种尺度的4381复合材料螺旋桨进行30°角铺层建模,分析了流固耦合下结构变形与敞水性能变化的尺度效应规律。研究结果表明:粘性力相对占比是刚性桨敞水性能尺度效应的主要因素;流固耦合最大变形比和螺距变形比均与缩尺比呈线性关系,因流体的附加刚度作用,最大变形比需在悬臂板挠度公式基础上作3%的修正;流固耦合后敞水性能的改变量与缩尺比呈线性关系,其尺度效应需在刚性桨敞水性能尺度效应关系上进一步作5%~7%的修正,修正量与复材桨压力中心区和桨叶的厚度均有一定关系。考虑流固耦合的复材桨尺度效应修正为不同尺度复材桨的数值计算和性能预报提供了有效参考。

非均匀伴流中复合材料螺旋桨非定常空化流固耦合研究

复合材料可改善螺旋桨空化性能及振动特性,在先进海洋推进装备领域备受关注。本文基于URANS计算复合材料螺旋桨外流场,应用FEM求解桨叶结构动态响应,并将水动力载荷及结构变形实时双向传递,建立复合材料螺旋桨非定常空化流固耦合数值计算方法。精细地模拟了桨叶经过高伴流区过程中叶梢空泡的演化;叶梢最大变形量随着叶梢空泡的初生、发展而逐渐增大,在梢涡空泡形成阶段达到最大值,然后随着空泡的溃灭而减小;揭示了复合材料的应用使螺旋桨推进效率得以提高、叶梢空化得以抑制的机理,即复合材料螺旋桨在空化水动力载荷作用下产生弯扭耦合变形,自适应地调整攻角以抑制空泡发展;对比了典型空化工况下复合材料与刚性金属螺旋桨空化水动力性能的区别;与刚性金属桨相比,复合材料螺旋桨的压力脉动峰值缓和,对非均匀伴流场的适应性更好。

冲击载荷下姿轨控贮箱流固耦合响应分析

含推进剂贮箱在高量级冲击载荷作用下会产生强烈的流固耦合振动,严重时可能引起结构破坏。为准确预示充液贮箱的冲击响应,揭示贮箱内流固耦合振动机理,采用光滑粒子流体动力学(SPH)方法与结构有限元方法,建立了充液贮箱耦合动力学模型,计算了不同载荷量级与充液比的贮箱加速度时程,并与实验结果进行对比。结果表明:高量级、高充液比下贮箱的加速度响应发生剧烈波动;就计算贮箱而言,满充液比下,载荷量级达到-3 dB时出现波动,峰值为5.33 g;0 dB载荷量级下,充液比达到75%时出现波动,峰值为7.82 g;0 dB载荷量级下满充液贮箱的波动最为剧烈,峰值计算值达到24.24 g,该值与实验结果对比,误差仅为2.78%。通过分析冲击过程中流体与结构的运动规律可知,冲击后加速度响应波动是由流体和贮箱壳体二者分离后产生的剧烈碰撞所引发。

基于流固耦合的AUV伴流对螺旋桨性能影响

自主式水下航行器(Autonomous Underwater Vehicle,AUV)螺旋桨的运转通常是在非均匀流场中,其中以AUV航行时产生的尾部伴流为主。为了分析尾部伴流对螺旋桨水动力及噪声的影响,首先利用P 4 119螺旋桨验证双向流固耦合数值模拟的可行性、准确性,其次建立AUV与B型图谱桨耦合模型,对比2种工况下螺旋桨动力性能与无空化噪声分布情况。结果表明,在AUV尾部不均匀的来流影响下,螺旋桨所需提供的推力和转矩有所提高,此增幅在最高时分别可以达到83.77%和50.50%;相较于1倍叶频时伴流对螺旋桨噪声的微弱影响,2倍和3倍叶频时螺旋桨噪声在各个监测点的声压级相较均匀来流衰减了20~50 dB,并且导致2倍叶频时螺旋桨噪声的分布呈现无规则形。

基于DEM-SPH流固耦合的冰区船舶快速性预报

船舶在冰区海域中航行会受到冰水环境阻力的影响,是冰区船舶快速性研究中的重要影响因素。为合理分析冰区船舶的快速性能,该文采用基于离散元(discrete element method,DEM)和光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)方法的流固耦合模型模拟船舶冰区航行过程,获得不同航速下的船舶阻力和推进力,进一步计算出螺旋桨的推力、扭矩以及定速航行所需的螺旋桨转速等参数。为研究船体结构、海冰与海水之间的流固耦合作用,文中通过SPH粒子与固定粒子边界相对运动的拟合项直接计算固体与流体之间的相互作用力,建立船体结构、海冰与海水耦合的DEM-SPH模型,并基于该模型分别对船舶在冰区的航行阻力和推进力进行模拟,通过拟合的方式匹配航行阻力和推进力,并考虑尾部流场导致的船体阻力增额,从而预报船舶在特定航速下实现自航所需的螺旋桨转速。此外,文中还模拟了DTMB 5415船模在浮冰区和层冰区中航行的阻力和不同螺旋桨转速下的推力,对船模在不同工况下实现特定航速航行所需的螺旋桨转速进行了预报。计算结果表明:DEM-SPH耦合模型对船-冰、桨-冰作用中的流固耦合过程模拟效果出色,可完整描述船体及尾部伴流场对海冰的拖曳作用;通过文中所述阻力-推力模拟算例及强制力的拟合分析,所形成的基于数值模拟方法的船舶自航下螺旋桨转速预报,可为进一步的试验验证和工程应用推广奠定基础。

对转舵桨水动力性能研究

对转舵桨兼有操纵性能良好和推进效率高的特点,在科考船、海洋工程船等船型上有一定数量的应用。该文采用改进的延迟分离涡模拟方法模拟了对转舵桨的敞水性能,并与模型试验结果进行对比分析,结果表明:设计工况推进单元的推力系数与转矩系数数值模拟误差在3%以内,满足工程精度要求。通过不同舵角下的敞水模型试验发现,舵角对前桨敞水性能影响较小,而对后桨影响较大,案例中约2.5°舵角时推进单元横向力为0。通过空泡模型试验,观察立柱对前桨梢涡形态的影响,发现前桨梢涡与后桨桨叶及后桨梢涡相遇使该位置的空泡现象显著增强。基于对转舵桨各部分相互影响关系,引入诱导速度修正系数,将对转舵桨的桨叶设计问题转化为给定来流条件的桨叶设计问题。

某全回转救助拖船船体结构振动分析

针对全回转救助拖船在螺旋桨最大转速时出现的船体结构振动问题,通过实船振动测试分析,判断引起船体结构振动的激励源来自艉部螺旋桨,而螺旋桨激励引起船体结构强迫振动和共振。在采取船艉结构加强,敷设阻尼减振材料的方法进行振动控制后,实船测试表明,船体结构振动速度最大降低7.23 mm/s。

嵌段型含氟中性聚合物键合剂的合成及应用

以丙烯腈、甲基丙烯酸甲酯、丙烯酸羟乙酯、甲基丙烯酸六氟丁酯为聚合单体,偶氮二异丁腈(AIBN)为引发剂,2–(2–氰基丙基)二硫代苯甲酸酯(CPDB)为链转移剂,通过控制加料顺序,采用可逆加成–断裂链转移(RAFT)活性自由基聚合工艺,一锅法制备了一种嵌段型含氟中性聚合物键合剂(LBA-311键合剂)。用核磁共振氢谱(^(1)H–NMR)、高效液相色谱(HPLC)、元素分析、凝胶渗透色谱(GPC)对所合成的中间产物及产品进行了结构表征与分析。结果表明,所合成的嵌段型含氟中性聚合物键合剂分子量和分子结构可控。与硝胺填料奥克托今(HMX)的界面作用研究表明LBA–311键合剂与HMX之间具有较好的浸润性和黏结强度。初步应用研究表明,LBA–311键合剂应用于叠氮高能固体推进剂配方中,使推进剂药柱常温拉伸强度和最大延伸率分别提高了51.9%和57.3%,具有较好的应用前景。

某平台供应船CPP舵桨装置应用

CPP舵桨是一种新型的可调螺距螺旋桨的Z型传动装置,螺旋桨的推力方向可在水平面内任意改变,且可实现其推力大小与其方向合理配合,改进了船舶传统推进装置结构形式,大幅提升了船舶的操纵性和灵活性,适用性强,市场应用前景广。文章以某57 m海上平台供应船的轴系布置与设计为例,阐述CPP全回转舵桨推进装置的结构特点、性能,以及其在海上平台的应用,并根据船舶布置要求对轴系布置进行优化设计,满足了海上平台供应船对机动性及操纵性的要求。

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

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.