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1.
Bu-Geun Paik Jin Kim Young-Ha Park Ki-Sup Kim 《Journal of Marine Science and Technology》2007,12(2):72-82
The vortex structure of the wake behind a marine propeller was investigated in terms of loading variation by using particle
image velocimetry. One hundred and fifty instantaneous velocity fields were ensemble averaged to study the spatial evolution
of the wake and the behavior of the tip vortices in the region ranging from the trailing edge to one propeller diameter downstream.
The trailing vorticity was found to be related to the radial velocity jump, and the viscous wake was affected by the boundary
layers developed on the blade surfaces. A vortex identification method using the swirling strength was employed to extract
the location of the tip vortex. The loading on the blade made a clear difference to the contraction angles. Slipstream contraction
occurred in the very near wake region, and unstable oscillation occurred because of reduced interaction between the tip vortex
and the wake sheet behind the maximum contraction point for each loading condition. The maximum tangential velocity around
the tip vortex center revealed the average radius of its core, which was used for calculating the vortex strength. Additionally,
variation of the average radius of tip vortices with the change of blade loading was related to vortex tube stretching in
the wake region. The nearly constant vortex strength continued up to one diameter downstream for light loading and design
loading conditions. 相似文献
2.
The computational fluid dynamics(CFD) method is used to numerically simulate a propeller wake flow field in open water.A sub-domain hybrid mesh method was adopted in this paper.The computation domain was separated into two sub-domains,in which tetrahedral elements were used in the inner domain to match the complicated geometry of the propeller,while hexahedral elements were used in the outer domain.The mesh was locally refined on the propeller surface and near the wake flow field,and a size function was used to control the growth rate of the grid.Sections at different axial location were used to study the spatial evolution of the propeller wake in the region ranging from the disc to one propeller diameter(D) downstream.The numerical results show that the axial velocity fluctuates along the wake flow;radial velocity,which is closely related to vortices,attenuates strongly.The trailing vortices interact with the tip vortex at the blades’ trailing edge and then separate.The strength of the vortex shrinks rapidly,and the radius decreases 20% at one diameter downstream. 相似文献
3.
《船舶与海洋工程学报》2019,(4)
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. 相似文献
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The main purpose of this investigation was to demonstrate a useful application of the particle image velocimetry (PIV) method to analyze the complex flow characteristics around a ship. For a sample illustration, the KRISO 3600TEU container ship model was chosen. The flow structure in the stern and near-wake region of the model has been investigated experimentally in a circulating water channel. Instantaneous velocity fields measured by the PIV velocity field measurement technique have been ensemble-averaged to give details of flow structures such as the spatial distributions of the local mean velocity, vorticity, and turbulent kinetic energy. The free-stream velocity was fixed at U
o = 0.6m/s, and the corresponding Reynolds number based on the length between perpendiculars was about 9.0 × 105. The container ship model shows a complicated three-dimensional flow structure in the stern and near-wake regions. The PIV results clearly revealed the formation of large-scale bilge vortices in the stern region and their effect on the flow in the near-wake. The results shown here provide valuable information for hull form design and the validation of viscous ship flow codes and of turbulence models. 相似文献
6.
A laser Doppler velocimetry (LDV) phase sampling technique is developed and adopted for the analysis of the flow upstream
and behind a four-blade, highly skewed installed propeller in the case of a twin-screw ship model in a large circulating water
channel. The technique implemented allows the reconstruction of the 3D flow field as a function of propeller angle in transversal
planes located as close as possible to the blade trailing and leading edges. The main features of the propeller installation
are highlighted, as well as the strong and complex interaction of the propeller with the hull wake, especially in the brackets
region. The high level of detail and accuracy of the data acquired would be a powerful tool for the development and validation
of computational codes applied to this topic. 相似文献
7.
浅吃水肥大型船的尾部线型研究 总被引:1,自引:0,他引:1
从分析船舶尾部伴流场对船舶阻力推进,操纵及船体振动性能等影响的观点,研究尾部三维伴流场,介绍尾型与伴流场之间关系及非对称双尾鳍船型的形成。非对称双尾鳍船型与优选的常规双尾鳍船型模型的阻力,自航及伴流场等比较试验结果表明,非对称双尾鳍船具有两大优点,首先,该船型能在浆前方产生一个与外旋浆旋向相反的预旋流,在保持了优良阻力性能前提下可提高外旋浆推进效率8%,获得阻力,推进,操纵各性能间的最佳配合,第二,轴向伴流分布比较均匀,满足BSRA5项衡准指标,改善了螺旋浆工作的流场条件,减少了螺旋浆产生空泡及其诱导船体激振的危险,使节能与减振得到统一,最后还介绍了该船型首制船“宁安1号”的实船测试结果及其由船模试验预报实船性能的一致性。 相似文献
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9.
螺旋桨旋涡发放数值模拟 总被引:1,自引:0,他引:1
基于LS-DYNA软件和任意拉格朗日—欧拉(ALE)方法,建立螺旋桨与流体相互作用的有限元模型,数值计算螺旋桨固定桨叶在前方来流下的流体动力特性和结构力学性能,分析总结桨叶后方旋涡运动和桨叶内部应力变化的规律。结果表明,螺旋桨桨叶的不规则形状导致了桨叶后方旋涡的相互作用,桨叶单元所在位置的厚度以及该位置与约束位置的距离决定了单元应力的大小。数值模拟得出的结论对研究螺旋桨"唱音"现象有一定的参考价值。 相似文献
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This paper evaluates various computational methods used to compute propeller performance, hydrodynamic side force and bending moment applied to an azimuth propulsor propeller shaft in oblique inflow. The two non-viscous models used are the BEM method and the blade element momentum theory (BEMT). RANS calculations are used to compute the loads on the propeller and the nominal wake velocity from the thruster body to be used in the BEMT model. The effect of the ship hull is also considered in the calculation by implementing the measured nominal wake of a ship hull at different propeller azimuthal positions. All the models are compared and validated against the experimental results, and the discussions are presented. 相似文献
12.
The main objective of this paper is to develop an efficient numerical method which can predict the underwater acoustic field
and pressure fluctuation on a ship hull due to unsteady propeller sheet cavitation by linear acoustic theory. In addition,
the noise scattered from the ship hull and reflected from the free surface are included. Concerning the computation of the
acoustic field induced by unsteady sheet cavitation and forces of a marine propeller, a method is derived without making any
approximation about the distance function between the noise source and field point. Thus, this method can be used to predict
acoustic pressure at both far and near fields, and this is very important for the scattering problem because the ship hull
is located very close to the propeller. For the computation of the scattering problem, a more efficient and robust method
is derived in time domain, which can treat multi-frequency waves scattered from underwater obstacles. The acoustic fields
of a container ship radiated by the propeller and scattered from the ship hull with free surface is investigated in this paper.
The pressure fluctuations of low blade rate on the ship hull induced by the propeller are also computed by the present method
and are found to be similar to the results obtained by a panel method satisfying the Laplace equation for the points near
the propeller due to the small retarding time. However, for the points on the ship hull away from the propeller, the differences
of the results between two methods will increase. 相似文献
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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. 相似文献
15.
同时考虑自由液面、真实螺旋桨的旋转运动,在数值水池实现了船/桨整体流场的数值计算。在既定航速下,推力与船体阻力为螺旋桨转速的函数,通过变化转速得到自航点。文中数值计算得到的自航点与物理水池试验自航点吻合良好。根据数值自航试验结果,不仅可通过积分的方法计算伴流分数与推力减额分数,还可详细分析螺旋桨进流与桨叶的速度、压力分... 相似文献
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We studied the effects of the surface roughness and initial gap on the responses of vortex-induced vibration (VIV) of a circular cylinder near a stationary plane wall, employing numerical methods. The VIV response amplitudes, lock-in regions, hydrodynamic forces, VIV trajectories and flow fields for three different surface roughnesses and two different initial gaps were systematically compared. The results reveal that the reduced velocity range can be divided into three regions based on the VIV amplitude as pre-lock-in, lock-in, and post-lock-in regions. The width of the lock-in region is not sensitive to the variation of the roughness. The mean drag coefficient has a decreasing tendency with the increased roughness. For a small initial gap, the clockwise wall boundary layer vortices has coalesced with the clockwise vortices shed from the upper side of the cylinder, which further suppresses the shedding of the counter-clock wise vortices from the lower side of the cylinder. The vortex shedding flow pattern displays a weak 2S mode. However, for a large initial gap, there is no coalescing action operating in the wake region and hence most of the vortex shedding flow patterns show an asymmetric 2S mode. 相似文献
18.
本文给出了螺旋桨周围流场的预报方法及其数值计算结果。本方法以具有涡分布和源汇分布的升力面来构造螺旋桨对流场的状动。升力面取奖叶拱弧面。根据桨叶表面流动不穿透条件解出升力面奇点后,然后再求它们对流场的扰动。敞水螺旋桨的脉动速度计算结果与试验结果吻合良好。 相似文献
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运用计算流体力学方法对水下潜器系统中导管螺旋桨在水下潜器转艏运动中螺旋桨周围的水动力现象进行观察,对在这样的工况下导管螺旋桨周围流场特征、进速、诱导速度、推力沿盘面和桨叶径向的分布,以及螺旋桨所发出的推力与螺旋桨周围流场之间的关系进行观察。计算结果表明:在一定的螺旋桨转速条件下,进速越小,螺旋桨所发出的推力也越大;由于导管出口处激发出的梢泄涡作用,导致盘面后叶梢附近轴向诱导速度降低、压力增大,该处叶面与叶背之间的压差也随之增大;螺旋桨的推力沿桨叶径向的分布呈现出半径越大,所产生的推力也越大的特点。 相似文献