共查询到19条相似文献，搜索用时 156 毫秒
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为改善船舶推进和海洋工程动力定位的性能,我们对可调螺距螺旋桨进行了多方面研究。已完成了盘面比为0.35、0.50和0.65的JDC三叶可调螺距螺旋桨系列的试验研究。获得了JDC系列全部试验结果。敞水试验数据按盘面比、初始螺距比、进速系数,转角、进速系数,初始螺距比及其相应的转角、进速系数三种组合进行多元回归分析,给出敞水曲线及其相应的多项式的系数和幂。水动力转叶力矩试验数据在不同盘面比时,按初始螺距比、转角、进速系数进行多元回归,给出水动力转叶力矩系数曲线及相应的多项式的系数和幂,离心力转叶力矩系数的计算值,在不同盘面比时按设计螺距比、转角进行多元回归,给出离心力转叶力矩系数曲线及其相应的多项式的系数和幂。最后给出各盘面比的B~(1/2)_p-δ图谱,供设计使用。 相似文献
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基于重叠网格模型,通过非定常RANS数值模拟与结果分析,研究了块状冰的尺寸、轴向运动和冰桨位置对螺旋桨水动力性能的影响。选用切割体网格绘制整体静止计算域的背景网格,之后结合棱柱层网格绘制螺旋桨子计算域和冰块子计算域的重叠网格,不同的计算域之间通过两者的重叠区域进行数据传递和插值。计算结果显示,当冰块固定在桨前时,螺旋桨产生的非定常推力和扭矩均以叶频为基频进行周期性变化,而且两者的时间平均值和振幅主要受冰块在螺旋桨盘面内的轴向投影面积、冰桨轴向位置和冰桨水平位置的影响;当冰块在桨前沿轴向匀速靠近螺旋桨时,冰桨轴向距离逐渐变小,冰桨周向相对位置发生周期性的变化,使得推力和扭矩两者均以叶频振荡,而且两者的时间平均值和振幅均随着冰桨轴向距离减小而增加。 相似文献
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《海洋技术学报》2014,(2)
文中针对一款配置4个螺旋桨且五自由度运动可控的微型缆控水下观测机器人进行了推进动力性能分析,采用流体力学方法计算了螺旋桨推力和扭矩,以及机器人的总体运动阻力和运动效率等关键动力参数。该水下机器人利用水平配置的螺旋桨推进器可实现前后移动和横向转弯,利用两个V型配置螺旋桨推进器可完成垂向、横向和横滚运动。文章首先对单个螺旋桨转速分别为3 000 rpm,4 000 rpm,5 000 rpm时进行了水动力学分析,计算了不同转速下对应的前向推力和阻力扭矩,拟合了转速-推力和转速-扭矩曲线;其次,对水下机器人整体模型在前向、横向和垂向三个方向上进行了水动力学计算,分析了机器人的整体运动阻力,拟合了机器人的速度-阻力曲线;然后,对应比较螺旋桨的转速-推力曲线和机器人的速度-阻力曲线,大致得出不同螺旋桨转速下机器人的推进速度,明确螺旋桨转速与机器人运动速度的对应关系,为螺旋桨水动力分析确定入口速度;最终,根据螺旋桨入口速度,重新计算螺旋桨水动力,绘制了转速-推力和转速-扭矩曲线,并确定机器人的推进效率,得出了螺旋桨转动和水下机器人整体运动的关键动力参数。 相似文献
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潜艇指挥台围壳对阻力和伴流场影响数值研究 总被引：2，自引：0，他引：2
采用Reynolds平均Navier-Stokes(RANS)方法计算潜艇三维粘性流场,分析潜艇指挥台围壳对潜艇水动力性能的影响.采用全附体SUBOFF模型验证了CFD方法,通过将螺旋桨盘面处的实效伴流场、艇体表面压力分布以及模型总阻力的模拟结果与Taylor船池的实验结果进行对比.比较结果显示CFD计算结果与实验数据具有很好的一致性,表明CFD方法可以用于潜艇指挥台围壳设计的水动力计算.通过数值计算研究指挥台围壳的高度和在艇上的分布位置对其后方的流场、螺旋桨盘面处的伴流场和阻力的影响. 相似文献
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当船舶在冰区航行时,螺旋桨会与海冰相互碰撞并导致桨叶的变形和损坏,进而影响船舶的航行安全。为研究海冰与螺旋桨的相互作用过程,采用离散元(DEM)—有限元(FEM)耦合方法构建海冰—螺旋桨切削模型。海冰和螺旋桨模型分别采用具有黏结—破碎特性的球体离散单元和8节点六面体有限单元构造。基于该DEM-FEM耦合模型讨论了不同切削深度下,螺旋桨所承受冰载荷的特点和规律;最后,研究了螺旋桨切削海冰过程中进速系数、推力系数、扭矩系数之间的对应关系,并讨论了海冰—螺旋桨相互作用过程中冰压力、Mises应力和变形的分布特点。以上研究可为寒区船舶安全航行和螺旋桨设计提供有益的参考。 相似文献
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船舶螺旋桨尾流场的数值分析 总被引：16，自引：1，他引：16
利用基于速度势的低阶面元法计算船舶螺旋桨的尾流场。采用计算较为简捷的关于扰动速度势的基本积分微分方程，并采用双曲面形状的面凶以消除面元间的缝隙。Newton-Raphson迭代过程被用来在桨叶随边满足压力Kutta条件，使桨叶面上表面的压力在随边有良好的一致性。在计算面元的影响系数时，应用了Morino导出的解析计算公式，加快了数值计算的速度。从解面元法的基本积分方程得到的偶极强度和源汇强度，直接求得尾流场的速度分布。 相似文献
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针对十万吨级深远海养殖工船在波浪中的阻力和运动响应开展了船模试验与模拟计算,并对其最小推进功率进行了校核。以试验流体力学（EFD）模型试验与模型尺度计算流体力学（CFD）模拟计算的结果进行对比作为方法验证,将实尺度CFD模拟计算的结果直接用于最小推进功率的校核。结果显示,EFD模型试验结果与模型尺度CFD计算结果误差在10%左右,计算精度满足工程要求。在规定的恶劣海况下该船型波浪增阻占总阻力的比例最高可达56.3%,螺旋桨转矩可达最大转矩的63.9%。等级2简化评估法得到的最小推进功率为等级1线评估法给出的最小功率线值的58.9%。研究表明实尺度CFD模拟计算可直接用于船舶最小推进功率的校核,此深远海养殖工船使用等级2简化评估方法进行校核更容易满足规范要求,其最小推进功率应不小于6 833 kW。 相似文献
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The paper analyzes the effect which prescribed errors in the cross-shore boundary conditions for a computational domain along a beach have on the flow field predicted inside the domain. This problem is relevant because errors in boundary conditions are unavoidable when modeling limited domains of a nearshore region. For simplicity, we consider a longshore uniform plane beach with monochromatic, obliquely incident waves, and assume depth uniform currents. It is then studied analytically and numerically how small perturbations of the boundary conditions along both upstream and downstream cross-shore boundaries spread inside the computational domain. It is found that the errors at the upstream cross-shore boundary tend to spread over a long distance downstream of the boundary, while the influence of the errors in the downstream boundary condition is limited to the adjacent upstream area of the computational domain. Both the numerical and analytical solutions show that the errors introduced at the upstream boundary decay exponentially in the surf zone at a rate proportional to the bottom friction. A simple formula is developed to estimate the influence distance of the upstream errors. If we consider the mismatch in the volume flux at the upstream boundary, the error merely redistributes in the cross-shore direction to conserve volume. In the case of excessive flux or velocity specified at the cross-shore boundaries, a circulation cell tends to appear in the offshore region where the errors caused by the boundary mismatch increase with the cross-shore width of the model domain. 相似文献
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A numerical study on the acoustic radiation of a propeller interacting with non-uniform inflow has been conducted. Real geometry of a marine propeller DTMB 4118 is used in the calculation, and sliding mesh technique is adopted to deal with the rotational motion of the propeller. The performance of the DES (Detached Eddy Simulation) approach at capturing the unsteady forces and moments on the propeller is compared with experiment. Far-field sound radiation is predicted by the formation 1A developed by Farassat, an integral solution of FW-H (Ffowcs Williams-Hawkings) equation in time domain. The sound pressure and directivity patterns of the propeller operating in two specific velocity distributions are discussed. 相似文献
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A numerical study on the acoustic radiation of a propeller interacting with non-uniform inflow has been conducted.Real geometry of a marine propeller DTMB 4118 is used in the calculation,and sliding mesh technique is adopted to deal with the rotational motion of the propeller.The performance of the DES(Detached Eddy Simulation) approach at capturing the unsteady forces and moments on the propeller is compared with experiment.Far-field sound radiation is predicted by the formation 1A developed by Farassat,an integral solution of FW-H(Ffowcs Williams-Hawkings) equation in time domain.The sound pressure and directivity patterns of the propeller operating in two specific velocity distributions are discussed. 相似文献
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In this study, the flow around the pod unit is analysed and the performance characteristics of the propeller on the pod are investigated. The main objective of the present work is to further improve the original numerical method developed before for the prediction of performance of podded propellers and to further validate the earlier developed numerical model with a specific emphasis on the hydrodynamic interaction amongst the propulsor components. While in the earlier numerical method, the axial induced velocities by pod and strut parts were included into the calculations on the propeller disc plane, in the present method the tangential induced velocities on the propeller disc plane are included in the calculations as well. The flow domain around the podded propeller is mainly divided into three parts; the axisymmetric pod part, the strut part and the propeller part. While the pod and strut parts are modelled by a low-order boundary element method (BEM), the propeller is represented by a vortex lattice method (VLM). Coupling of the BEM and the VLM is carried out in an iterative manner to incorporate the effect of the pod on the propeller, and vice versa. The present numerical method is applied to two different podded propellers with zero yaw angles in order to compare the results with those of experimental measurements. The present numerical method is also validated in the case of 15° of yaw angle for a podded propulsor. The effect of pod and strut on the propeller and vice versa are discussed. 相似文献
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Surface Piercing Propellers (SPP) show high efficiency at high advance speeds. Regarding operational conditions, this kind of propellers generate an air layer when entering the water due to the rotation of the propeller; this phenomenon is called ventilation. The ventilation phenomenon divided into some mechanism with respect to air cavity length on the propeller surface; among them are partially ventilation mechanism and fully ventilation mechanism which has great importance. In this study, using numerical simulation, we have investigated ventilation patterns and also the performance of a five-blade SPP propeller (SPP 5.74) at immersion ratio of 33, 40, 50and 70% respectively. We used Sliding Mesh Technique for modeling. Also, we applied the volume of fluid method to simulate the open surface pattern. To validate numerical results, the four-blade propeller, 841-B was simulated, and then the results of thrust and torque coefficients compared with Olofsson experimental results and validated accordingly. The findings indicate that the maximum value for thrust and torque coefficient would occur at immersion ratio of 70% and the maximum propeller efficiency occurs at immersion ratio of 33% and advance coefficient of 1.1; Moreover, the critical advance coefficient (at the partially and the fully ventilation boundary) increases by a reduction in immersion ratio, so that critical advance coefficients are 0.6 and 0.76, respectively at immersion ratios of 70 and 33%. Meanwhile, as advance coefficient increases, length of ventilation zone will decrease, and consequently the propeller will be laid on partial ventilation zone. 相似文献
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Accurate propeller shaft speed controllers can be designed by using nonlinear control theory and feedback from the axial water velocity in the propeller disc. In this paper, an output feedback controller is derived, reconstructing the axial flow velocity from vehicle speed measurements, using a three-state model of propeller shaft speed, forward (surge) speed of the vehicle, and the axial flow velocity. Lyapunov stability theory is used to prove that a nonlinear observer combined with an output feedback integral controller provide exponential stability. The output feedback controller compensates for variations in thrust due to time variations in advance speed. This is a major problem when applying conventional vehicle-propeller control systems. The proposed controller is simulated for an underwater vehicle equipped with a single propeller. The simulations demonstrate that the axial water velocity can be estimated with good accuracy. In addition, the output feedback integral controller shows superior performance and robustness compared to a conventional shaft speed controller 相似文献
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In this study, non-cavitating and cavitating flow around the benchmark DTMB 4119 model propeller are solved using both viscous and potential based solvers. Cavitating and non-cavitating propeller radiated noises are then predicted by using a hybrid method in which RANS(Reynolds-averaged Navier-Stokes) and FWH(Ffowcs Williams Hawkings) equations are solved together in open water conditions. Sheet cavitation on the propeller blades is modelled by using a VOF(Volume of Fiuld) method equipped with Schnerr-Sauer cavitation model.Nevertheless, tip vortex cavitation noise is estimated by using two different semi-empirical techniques, namely Tip Vortex Index(TVI, based on potential flow theory) and Tip Vortex Contribution(TVC). As the reference distance between noise source and receiver is not defined in open water case for TVI technique, one of the outputs of this study is to propose a reference distance for TVI technique by coupling two semi-empirical techniques and ITTC distance normalization. At the defined distance, the starting point of the tip vortex cavitation is determined for different advance ratios and cavitation numbers using potential flow solver. Also, it is examined that whether the hybrid method and potential flow solver give the same noise results at the inception point of tip vortex cavitation.Results show that TVI method based on potential flow theory is reliable and can practically be used to replace the hybrid method(RANS with FWH approach) when tip vortex cavitation starts. 相似文献
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The hydrodynamic characteristics of a marine propeller operating in oblique inflow are investigated by using CFD method. Two propellers with different geometries are selected as the study subjects. RANS simulation is carried out for the propellers working at a wide range of advance coefficients and incidence angles. The effects of axial inflow and lateral inflow are demonstrated with the hydrodynamic force on the propeller under different working conditions. Based on the obtained flow field details, the hydrodynamic mechanism of propeller operating in oblique inflow is analyzed further. The trailing vortex wake of propeller is highly affected by the lateral inflow, resulting in the deflected development path and the circumferentially non-uniform structure, as well as the enhanced axial velocity in slipstream. Different flow patterns are observed on the propeller blade with the variation of circumferential position. Combined with the computed hydrodynamic forces and pressure distribution on propeller, the mechanism resulting in the increase of propulsive loads and the generation of propeller side force is explored. Finally, a systematic analysis is carried out for the propulsive loads and propeller side force as a function of axial and lateral advance coefficients. The major terms that play a dominant role in the modeling of propulsive loads and propeller side force are determined through the sensitivity analysis. This study provides a deeper insight into the hydrodynamic characteristics of propeller operating in oblique inflow, which is useful to the investigation of propeller performance during ship maneuvers. 相似文献