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.

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.

Multi‑Crack Interaction and Influence on the Spherical Pressure Hull for a Deep‑Sea Manned Submersible

This study investigates the interaction and influence of surface cracks on the spherical pressure hull of a deep-sea manned submersible.The finite element model of the spherical hull is established,and a semi-elliptical surface crack is inserted in the welding toe of the spherical hull as the main crack.Considering the combined effect of external uniform pressure and welding residual stress at the weld toe,the stress intensity factor(SIF)is obtained based on the M-integral method.Inserting disturbing cracks at different positions on the spherical hull surface,the interaction and influence between multi-cracks are revealed by numerical calculation.The results show that the existence of the disturbing crack has a great influence on the stress intensity factor of the main crack,and the influence is different with the different location of disturbing crack.The study of the interaction of multiple cracks under different interference factors and the influence of disturbing cracks on the main crack can provide some reference for future engineering applications.

Analysis of structural behavior during collision event accounting for bow and side structure interaction

The main goal of this study was to investigate the effects of selected ship collision parameter values on the characteristics of the absorbed energy in several ship collision scenarios. Non-linear simulations were performed using a finite element method （FEM） to obtain virtual experiment data. In the present research, the size of the side damage from a collision phenomenon were measured and used to verify the numerical configuration together with the calculation results using an empirical equation. Parameters in the external dynamics of a ship collision such as the location of the contact point and velocity of the striking ship were taken into consideration. The internal energy and deformation size on the side structure were discussed further in a comparative study. The effects of the selected parameters on several structural behaviors, namely energy, force, and damage extent were also observed and evaluated in this section. Stiffener on side hull was found to contribute significantly into resistance capability of the target ship against penetration of the striking bow. Remarkable force during penetration was observed to occur when inner shell was crushed as certain velocity was applied in the striking bow.

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.

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.

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.

Numerical estimation of bank-propeller-hull interaction effect on ship manoeu-vring 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 availa- ble 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.

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。

超分子甲基肼凝胶燃料流变性能研究

流变性能研究是凝胶推进剂研究的一项重要内容,其结果可为推进剂的雾化、燃烧等性能研究提供基础。超分子甲基肼凝胶燃料内部以氢键等非共价相互作用力作为支点,形成网状结构,其流变性能与胶凝剂含量和温度条件密切相关。实验结果表明,胶凝剂含量越高,体系越稳定。胶凝剂质量分数为1.2%时,超分子甲基肼凝胶燃料可在得到最高的能量性能的同时保证稳定性。随着体系温度的升高,形成凝胶网络结构的氢键作用力会变弱,对分子的限制作用也会减弱。体现在流变性能上,就是随着温度的增加,体系黏度和剪切应力降低;在达到50℃时,超分子甲基肼凝胶燃料已处于凝胶-溶液转变的临界点。超分子甲基肼凝胶燃料还具有剪切恢复性,在经历10次剪切过程后,黏度仅有少量降低。

PBT推进剂中水氧扩散及键合作用的分子动力学模拟

采用分子动力学模拟方法,对H_(2)O和O_(2)在三氟化硼三乙醇胺络合物(T313)中的扩散行为进行模拟,并研究了叠氮聚醚聚氨酯(PU_(PBT))/T313/高氯酸铵(AP)复合体系在不同界面层间的结合能和界面间的相互作用机理。扩散模拟结果显示,随着温度升高,H_(2)O在T313中的扩散系数逐渐降低,O_(2)在T313中的扩散系数逐渐增大,呈现出相反的变化趋势,表明极性分子和非极性分子在键合剂膜层中的扩散现象有显著差异。PU_(PBT)加入键合剂T313后,与AP颗粒之间的结合将更加紧密。PU_(PBT)/T313体系的界面黏附能力主要由PU_(PBT)体系中的原子与T313中各原子之间的强范德华相互作用或氢键相互作用提供,而T313/AP体系的界面黏附能力主要由AP和PU_(PBT)体系中原子之间的强范德华相互作用提供。

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。

环肋布局对钛合金圆柱耐压壳内爆过程的影响研究

环肋圆柱壳是深潜器耐压结构的主要形式,但由于极限承载能力和振动特性的需求,存在不同的环肋布局形式。为探究环肋布局对钛合金圆柱耐压壳内爆的影响,基于任意拉格朗日欧拉方法开展数值研究。首先对比试验结果验证液-固-气三相流固耦合数值模型的准确性。然后分析3种环肋布局下圆柱耐压壳水下内爆过程中的结构动态响应、冲击波传播以及能量演化等特征。结果表明,环肋均布时,内爆中心由筒体中部向一端移动。而中部和端部加强时,内爆中心由环肋稀疏位置向密集位置移动,结构动能均存在显著的二次波峰现象。此外,中部加强能有效降低最大冲击波峰值。通过对环肋圆柱壳内爆响应特性的分析,对深海耐压结构的设计具有重要的工程意义。

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。

基于动刚度法的水面船舶桨-轴-船体耦合系统

为分析在低频段内船体两侧螺旋桨激励相位差对船体振动的影响,基于动刚度法建立水面船舶桨-轴-船体耦合系统的横向振动3梁耦合模型。将动刚度法的计算结果与有限元法进行对比,表明动刚度法具有良好的精度。分析桨-轴-船体耦合系统的垂向固有振动特性。在低频段内该系统主要表现为船体梁的振动,推进轴系对船体梁的固有特性影响较小。对左右双桨分别施加不同相位差的单位垂向简谐力,计算由各轴承位置输入至船体梁的功率流。结果表明,双桨激励相位差的增大会使输入至船体梁的功率流变小。因此,在对桨-轴-船体耦合系统的横向振动控制方面,应重点关注双桨激励相位差较大时的工况。

基于经验公式法的船舶螺旋桨脉动压力计算与软件开发

船体振动是船舶在航行过程中由于各种原因产生的振动,船上90%的振动源于螺旋桨的脉动压力,其可激起艉部振动、上层建筑振动和局部振动。特别是在螺旋桨上方区域,往往由螺旋桨脉动压力而激起局部结构共振或强迫振动,进而造成结构疲劳破坏或居住舒适度减小,因此减少螺旋桨脉动压力产生的振动很有必要。在螺旋桨设计初期,过于复杂的脉动压力计算方法便捷性不高,设计出1款能快速估算螺旋桨脉动压力的软件十分重要。该文基于QT平台和MATLAB软件混合编程,采用经验公式法,开发了1款船舶螺旋桨脉动压力快速估算软件,探讨了脉动压力的影响因素及其变化规律。结果表明:船舶剖面形状参数、船舶种类和螺旋桨转速对螺旋桨脉动压力影响较大。该项研究成果可为船舶减振降噪提供参考。

大侧斜弹性桨非空泡噪声特性研究

以某型七叶大侧斜螺旋桨为研究对象,视螺旋桨为弹性体,采用计算流体力学(Computational Fluid Dynamics,CFD)耦合有限元法(Finite Element Method,FEM)的双向流固耦合方法,计算螺旋桨水动力性能。通过现有试验数据及相关文献验证该数值方法的准确性。并基于时域下桨叶表面的脉动压力作为旋转偶极子声源,通过傅里叶变换及声学有限元软件LMS Virtual. Lab计算分析七叶大侧斜弹性桨的非空泡噪声特性。结果表明,在5~1 000 Hz频段内,弹性桨的辐射声压级大于刚性桨。桨叶低阶弹性振动容易被激发,产生共振。针对偶极子声源,桨叶轴向平面内,远场的声压指向性主要为“∞”形分布,并且轴向的声压级远大于盘面方向,更容易被敌方声纳探测。近水面会影响螺旋桨辐射声压级的大小,越接近水面,声压幅值越小,这一现象在远场点处更显著。此外,螺旋桨轴向两端的声压指向性受近水面影响呈现不对称分布。