基于流道倾角对喷水推进泵流道性能的影响研究

利用参数化方法设计了4种不同流道倾角的喷水推进泵椭圆形进水流道,并采用三维雷诺平均N-S方程和RNGκ-ε湍流模型对其流场和性能进行数值仿真.从流道的出流均匀性、流动分离方面来分析在保持进口速比不变,不同流道倾角时流道内流场的变化情况,为喷水推进器进水流道倾角的设计提供依据.计算结果表明:流道倾角对喷水推进泵水力性能和流场变化影响较大.在设定进速比的条件下,随着流道倾角的增大,喷水推进泵流道出口的流场均匀性变差,流道内部更容易发生流动分离现象,且在流道倾角为47°时的喷水推进泵在设计工况下的流场特性最差.     

水下喷水推进器工作特性分析

在充分研究固体燃料涡轮机和高速轴流泵的基础上,提出了应用于水下航行器的喷水推进系统。研究了设计工况时,航行器、轴流泵、发动机的运动学和动力学平衡关系;在定深工况下,分析喷嘴数目变化时航行器的稳定速度;以及不同喷嘴数目时,航行器的变深和变速特性。研究结果表明,喷水推进器能够实现水下航行器大航深、高航速的性能目标。研究结果对喷水推进水下航行器具有重要的参考价值。     

喷水推进器进口流道水动力性能分析

[目的]研究喷水推进器进口流道主参数对其性能的影响,为喷水推进器设计提供依据.[方法]基于STAR-CCM+商业软件,通过定常雷诺平均NS方程(RANS),数值模拟分析不同进速比(IVR)工况下喷水推进器进口流道轴线高度和进流角度对其水动力性能的影响,并根据国际拖曳水池会议(ITTC)的不确定度分析规程进行数值不确定度...     

基于CFD的喷水推进泵导叶三维反设计研究

导叶整流效果不佳是某喷水推进船未达到设计航速的一个重要原因.介绍基于三维理论的喷水推进泵导叶设计方法,叶片形状通过给定轴面轮廓和环量分布规律后经迭代计算得出.基于计算流体力学工具建立描述喷水推进泵内流场的数值模型,采用六面体网格划分计算域,选用SST湍流模型封闭雷诺时均方程.通过周向动能与轴向动能的比值来评估导叶的整流效果,分析喷口直径和导叶轴面形状对喷水推进泵性能的影响规律.结果表明:三维反设计方法和CFD可在喷水推进泵导叶设计中发挥重要作用,导叶经优化设计后可使喷水推进泵推力提高约5%.     

喷水推进混流泵流体动力性能的CFD研究

采用CFD方法研究KaMeWa公司的某型喷水推进混流泵的流体动力性能,并分析其内部流场特性。通过几何建模,将泵划分为进口、叶轮、导叶体和喷口四部分。分别采用结构化网格离散计算区域。应用k-ε和k-ω相结合的SST湍流模型封闭控制方程,采用全隐式多区域网格耦合求解。预报其功率、扬程、效率等特性,将泵功率的计算结果与该泵厂家试验数据进行比较,误差在2%以内。说明本研究采用的CFD方法预报该泵的流体动力性能真实可信。根据计算结果,对内流场的流线和叶片表面的压力分布做了详细分析。     

基于数值试验及实船试航的喷水推进器改型设计

采用基于雷诺时均法的SST湍流模型对"某轴流式喷水推进泵+进水流道+船体"系统进行数值计算,查找出了该喷水推进泵和进水流道设计存在的一些问题。依据该船体阻力、设计航速和主机功率等参数重新对该船喷水推进器进行选型,进而运用三元的方法对喷水推进泵进行设计,利用参数化设计的方法对流道进行设计。采用了数值试验的方法校核新设计的混流式喷水推进器流体动力性能,计算结果表明:新设计喷水推进泵和进水流道性能优异,并且能够较好地满足快速性指标。最后,对改进设计的喷水推进器进行了快速性预报和实船试航,试航结果表明新设计混流式喷水推进器推进航速超过设计航速9.4%,并且数值预报航速与试航结果误差为1.5%,这既验证了设计方法的有效性,也验证了所采用的数值模型的准确性。     

超高压喷射条件下非常态燃油的缸内燃烧排放特性研究

以改善大功率柴油机的燃烧与排放性能为目标,创新性地提出180 MPa 以上的超高燃油喷射压力。建立包括进气道和燃烧室在内的三维几何模型,利用 AVL FIRE 软件对仿真模型进行动网格划分,将燃油喷射系统的喷嘴内流场计算结果作为边界条件对燃烧过程进行仿真计算,分析燃油物性参数的变化以及喷嘴参数对柴油机燃烧排放性能的影响。结果表明：当燃油的物性参数发生变化之后,喷孔内部空化效应的增强有助于油束获得良好的初始破碎状态,雾化效果好,缸内燃烧过程进行得更加充分;当喷孔直径增大时,油滴初始湍动能增强,运动发展范围较大,喷油持续期短,后期排放物浓度小;随着喷射夹角增大,缸内燃油与空气混合得更加均匀,燃烧性能进一步提高。     

受渗流影响的冲积河道中圆型和矩形桥墩受腐蚀情况和流动特性比较（英文）

The present study examines scour geometry and turbulent flow characteristics around circular and oblong piers in alluvial channel with downward seepage. Experiments were conducted in plane sand bed of non-uniform sand under no seepage, 10% seepage and 15% seepage conditions. Scour depth at oblong pier is significantly lesser than the scour depth at circular one.However, the scour depth at both piers reduces with downward seepage. The measurements show that the velocity and Reynolds stresses are negative near the bed at upstream of piers where the strong reversal occurs. At downstream of oblong pier near the free surface, velocity and Reynolds stresses are less positive; whereas, they are negative at downstream of circular pier. The streamline shape of oblong pier leads to reduce the strength of wake vortices and consequently reversal flow at downstream of pier. With application of downward seepage turbulent kinetic energy is decreasing. The results show that the wake vortices at oblong pier are weaker than the wake vortices at circular pier. The strength of wake vortices diminishes with downward seepage.The Strouhal number is lesser for oblong pier and decreases with downward seepage for both oblong and circular piers.     

Comparison of Scour and Flow Characteristics Around Circular and Oblong Bridge Piers in Seepage Affected Alluvial Channels

The present study examines scour geometry and turbulent flow characteristics around circular and oblong piers in alluvial channel with downward seepage. Experiments were conducted in plane sand bed of non-uniform sand under no seepage, 10% seepage and 15% seepage conditions. Scour depth at oblong pier is significantly lesser than the scour depth at circular one. However, the scour depth at both piers reduces with downward seepage. The measurements show that the velocity and Reynolds stresses are negative near the bed at upstream of piers where the strong reversal occurs. At downstream of oblong pier near the free surface, velocity and Reynolds stresses are less positive; whereas, they are negative at downstream of circular pier. The streamline shape of oblong pier leads to reduce the strength of wake vortices and consequently reversal flow at downstream of pier. With application of downward seepage turbulent kinetic energy is decreasing. The results show that the wake vortices at oblong pier are weaker than the wake vortices at circular pier. The strength of wake vortices diminishes with downward seepage. The Strouhal number is lesser for oblong pier and decreases with downward seepage for both oblong and circular piers.     

具有向下渗漏特性的沙质渠道中串列桥墩绕流及冲刷特性试验研究（英文）

Experimental investigations have been carried out to study morpho-hydraulic characteristics such as scour geometry and turbulent flow properties around tandem piers in alluvial channels. Experiments were carried out in a plane sand bed with two circular piers of same diameter arranged in tandem manner under no seepage, 10% seepage and 20% seepage conditions. Downward seepage minimizes the scour depth around piers and restrains the development of scour depth with time. Strong reversal flow is found near the bed at upstream of piers and near free surface at downstream of piers where velocity and Reynolds shear stress are found to be negative which reduce in magnitude with downward seepage. The flow is more critical within the gap between two piers where velocity is lesser near free surface and gradually increasing towards bed. Quadrant analysis shows that contribution of each event to the total Reynolds shear stress increases with downward seepage. Sedimentation effect prevails within the scour hole whereas outside the scour hole erosive forces become more dominant. Reduced reversal flow at upstream of pier because of downward seepage results in decreasing higher order moments and turbulent kinetic energy. At downstream of piers, secondary currents are dominant due to wake vortices. Strouhal number decreases in case of seepage runs than no seepage condition.     

半潜式钻井平台风载荷CFD预报

在平台设计过程中,海洋平台受到的风载荷是稳性分析与结构设计需要考虑的重要因素。本文采用CFD技术,对某型半潜式钻井平台在作业工况下受到的风载荷进行了预报,分析了湍流模型、风速剖面形式、湍流强度分布等因素对半潜式钻井平台风载荷的影响。结果表明：不同湍流模型对海洋平台风载荷的预报偏差在2%以内,可以忽略湍流模型的影响;风速剖面对风载荷有较大影响,随着风速梯度的增加而增大;湍流强度分布对海洋平台风载荷的影响在6%以内。研究结论可为建立高精度的海洋平台风载荷数值预报方法提供技术支持。     

喷水推进泵空化性能数值模拟与试验验证

为研究喷水推进泵空化性能,采用计算流体力学(CFD)方法对自行设计的喷水推进泵内部空化流场进行了数值计算与分析。用六面体结构化网格对喷水推进泵的进流管道、叶轮、导叶体和出流管道进行网格划分;通过求解由SST湍流模型封闭的RANS方程计算得到喷水推进泵内部流场,计算得到的扬程、功率和效率特性曲线与试验结果吻合较好。文中还对多个流量的空化性能进行了数值预报,计算结果与试验数据在趋势上具有一致性;小流量工况的临界净正吸头与试验值误差较小,而大流量工况的临界净正吸头与试验值误差较大。研究结果表明:采用CFD方法预报喷水推进泵内部空化流场和空化性能是可行的,可作为喷水推进泵优化设计的有效途径。     

Verification and validation study of URANS simulations for an axial waterjet propelled large high-speed ship

The accurate prediction of waterjet propulsion using computational fluid dynamics (CFD) is of interest for performance analyses of existing waterjet designs as well as for improvement and design optimization of new waterjet propulsion systems for high-speed marine vehicles. The present work is performed for three main purposes: (1) to investigate the capability of a URANS flow solver, CFDSHIP-IOWA, for the accurate simulation of waterjet propelled ships, including waterjet–hull interactions; (2) to carry out detailed verification and validation (V&V) analysis; and (3) to identify optimization opportunities for intake duct shape design. A concentrated effort is applied to V&V work and performance analysis of waterjet propelled simulations which form the focus of this paper. The joint high speed sealift design (JHSS), which is a design concept for very large high-speed ships operating at transit speeds of at least 36 knots using four axial flow waterjets, is selected as the initial geometry for the current work and subsequent optimization study. For self-propelled simulations, the ship accelerates until the resistance equals the prescribed thrust and added tow force, and converges to the self propulsion point (SPP). Quantitative V&V studies are performed on both barehull and waterjet appended designs, with corresponding experimental fluid dynamics (EFD) data from 1/34 scale model testing. Uncertainty assessments are performed on iterative convergence and grid size. As a result, the total resistance coefficient for the barehull case and SPP for the waterjet propelled case are validated at the average uncertainty intervals of 7.0 and 1.1%D, respectively. Predictions of CFD computations capture the general trend of resistance over the speed range of 18–42 knots, and show reasonable agreement with EFD with average errors of 1.8 and 8.0%D for the barehull and waterjet cases, respectively. Furthermore, results show that URANS is able to accurately predict the major propulsion related features such as volume flow rate, inlet wake fraction, and net jet thrust with an accuracy of ~9%D. The flow feature details inside the duct and interference of the exit jets are qualitatively well-predicted as well. It is found that there are significant losses in inlet efficiency over the speed range; hence, one objective for subsequent optimization studies could be maximizing the inlet efficiency. Overall, the V&V work indicates that the present approach is an efficient tool for predicting the performance of waterjet propelled JHSS ships and paves the way for future optimization work. The main objective of the optimization will be reduction of powering requirements by increasing the inlet efficiency through modification of intake duct shape.     

Application of large eddy simulation in the performance study of wave blocker

The configuration and aerodynamic performance of the inlet system are important aspects in the process of installing a gas turbine on a naval vessel. Under the requirements, large eddy simulation （LES） is used to simulate the three-dimensional fluid flow in the wave blocker of a marine inlet filter. The Smagorinsky-Lilly sub-grid model was used to model motions of small-scale structures. During numerical simulation, the SIMPLE algorithm was applied. The central-differencing spatial discretization scheme and the second order accuracy finite difference for the temporal discretization were used. Simulation gives satisfactory distribution of the vorticity fields and turbulent kinetic energy. Compared with the k-ε turbulent model, the results of LES are better for the distribution of parameters. The results of experimental study in a small-scale wind tunnel indicate that numerical calculation has higher accuracy. Therefore, the methods used are worthy of reference and introduction for the design of an inlet system.     

水下潜器系统导管螺旋桨水动力特性及周围流场分布预报与分析

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。     

导边与随边设计对喷水推进泵性能的影响

采用相同的叶片轴面流线载荷分布和叶轮出口环量分布规律,改变导边与随边位置设计出多个喷水推进泵叶轮。基于雷诺时均的N-S方程、SST湍流模型和多重参考坐标系对叶轮内流场进行数值模拟,结果表明：导边向进口适度延伸可减小叶片进口边的载荷,利于提高空化性能,但效率有所降低;随边倾斜参数与叶轮出口的轴面速度分布和叶片表面的压力分布特性关联。     

泵喷水推进器分析与设计改进

通过CFD仿真技术获取了某快艇原载轴流式泵喷水推进器的性能,并通过经典计算发现原载轴流式喷水推进器的额定流量与快艇阻力特性不匹配,且其扬程远远低于期望值。新的泵喷水推进器主要从两个方面进行了改进：一是通过调整喷嘴出口口径使泵喷水推进器在最优效率点运行时正好符合快艇的阻力特性;二是提高泵喷水推进器的扬程使其满足能量平衡的需求。根据确定的参数设计了新的斜流式泵喷水推进器。通过CFD仿真表明斜流式泵喷水推进器达到了设计指标。试水试验表明配备新的泵喷水推进器后快艇达到了期望的要求。     

PIV velocity field measurements of flow around a KRISO 3600TEU container ship model

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.     

相继增压柴油机切换点进气涡流仿真对比研究

应用STAR-CD软件对相继增压柴油机切换点工况的进气过程进行了仿真对比研究,着重对只有主增压器工作（1TC）和两台增压器都工作(2TC)状况下的进气道和气缸内的速度场、压力场等进行了对比分析。计算结果表明：在整个进气过程中,1TC较2TC的湍动能最大提高率为38%,1TC较2TC的涡流比最大提高率为29%,有利于进一步的油气混合过程。     

Effects of bulbous bow on cross-flow vortex structures around a streamlined submersible body at intermediate pitch maneuver: A numerical investigation

A flow field around a streamlined body at an intermediate angle of incidence is dominated by cross-flow separation and vortical flow fields. The separated flow leads to a pair of vortices on the leeside of the body; therefore, it is essential to accurately determine this pair and estimate its size and location. This study utilizes the element-based finite volume method based on RANS equations to compute a 3D axisymmetric flow around a SUBOFF bare submarined hull. Cross-flow vortex structures are then numerically simulated and compared for a submarine with SUBOFF and DRDC STR bows. Computed results of pressure and shear stress distribution on the hull surface and the strength and locations of the vortex structures are presented at an intermediate incidence angle of 20°. A wind tunnel experiment is also conducted to experimentally visualize the vortex structures and measure their core locations. These experimental results are compared with the numerical data, and a good agreement is found.