三维被动摆动水翼对波浪滑翔机推进动力的性能研究

针对水翼在波浪滑翔机运动中对本体产生的推进动力的预报问题,利用CFD分析软件Star-CCM+中的平面运动机构(PMM)模块,对水翼翼板在波浪滑翔机主体随浪升沉过程中产生的升沉和绕自身旋转轴被动摆动的耦合运动过程进行三维模拟。通过对运动过程中水翼产生的推进动力进行分析,探究水翼的波浪参数(波高、周期)和结构参数(展弦比)等对水翼推进性能的影响。研究发现,在相同波高下,水翼摆动角速度与波浪周期成反比;水翼的前向平均推力系数与周期的平方成反比、与波高值近似成二次项比例关系;展弦比增加可以增大翼板的平均推力系数,但增加幅度不大。     

湍流进流诱发的二维水翼振动噪声特性研究

为研究螺旋桨流噪声,以螺旋桨的基本构型单位二维翼型为研究对象,研究其在不同工况下的振动噪声规律。以Lighthill声类比理论为基础,应用计算流体力学软件CFX和声学仿真软件LMS Virtual Lab分别模拟在不同工况下翼型的流场和声场分布。取翼型非定常脉动力作为声源,然后采用边界元方法分别求解翼型流噪声和振动噪声。结果表明,噪声水平随速度和翼型攻角的变化呈现较为明显的规律;相比考虑翼型振动时的振动噪声,忽略翼型振动影响的情况下流噪声水平偏大。     

应用DES方法模拟非定常空泡流动

在水下运动的水翼表面的局部低压区会形成空泡,而空泡具有随时间变化的非定常特性.采用DES(dettached eddy simulation)方法模拟绕水翼空泡流动的非定常特性.模拟了空泡的发生、发展、破灭、脱落的非定常过程,获得了空泡的发展、演变过程中水翼升力、阻力随时间变化的情况.模拟结果表明,空泡流动表现出明显的周期性特征;水翼的升力、阻力的周期性波动表现出同步变化的特征.将模拟结果与实验数据对比显示该方法可以准确地模拟空泡流动.     

EXPERIMENTAL AND NUMERICAL STUDY FOR HYDRODYNAMIC CHARACTERISTICS OF AN OSCILLATING HYDROFOIL

The present article reports the experimental Particle Image Velocimetry （PIV） investigation and the corresponding numerical simulation results about the water flow over the oscillating hydrofoil and its unsteady dynamic characters. The experimental study focuses on the effect of mean angles of attack. The comparison between the PIV results and numerical prediction about the flow field using Fluent well demonstrates the capability of CFD on the simulation of the water flow around the pitching hydrofoil. The numerical results indicate that the forced oscillating frequencies have evident effects on the flow separation and vortex shedding. The simulations about the hydrodynamic drag and lift coefficients were also performed.     

Computational Cavitation Flows at Inception and Light Stages on an Axial-Flow Pump Blade and in a Cage-Guided Control Valve

Cavitation flows induced around an axial-flow pump blade and inside a high pressure cage-type valve are simu-lated by a two-dimensional unsteady Navier-Stokes analysis with the simplest treatment of bubble dynamics.Thefluid is assumed as a continuum of homogeneous dispersed mixture of water and vapor nuclei.The analysis isaimed to capture transient stages with high amplitude pressure change during the birth and collapse of the bubbleespecially at the stage of cavitation inception.By the pump blade analysis,in which the field pressure is moderate,cavitation number of the inception and locations of developed cavitation are found to agree with experimental re-suits in a wide flow range between high incidence and negative incidence.In the valve flow analysis,in which thewater pressure of 5MPa is reduced to 2MPa,pressure change responding to the bubble collapse between the vaporpressure lower than 1 KPa and the extreme pressure of higher than 10~4 KPa is captured through a stable computa-tion.Location of the inception bubble and pressure force to the valve plug is found agree well with the respectiveexperimental features.     

豪华高速游艇水上“飞行”：C形水翼托船体出水面

斯洛文尼亚的轮机工程师研发了这种船,形容这是“一款超安静、环保的船只”。“它的无噪音电动机和零排放,使得它能在湖泊、河流、海洋和生态环保区（大部分汽艇和水上摩托艇不允许在这些地方航行）任意驰骋。它无噪音、不会激起大浪、无排放。”     

带耗散格林函数源面板法水翼数值模拟

探索水翼与流体之间相互作用下的复杂流场内部机制,对水翼的研究与发展具有重要的意义.利用带耗散的源格林函数的源面板方法,数值模拟均匀势流下的二维对称水翼的表面压力与自由面波高.数值模拟结果表明,在带攻角的情况下,水翼上表面压力低于下表面压力,水翼产生向上的升力作用;取较大的耗散数进行数值模拟,水翼的自由面波高呈现明显变小的趋势;随着Froude数的增大,圆柱体自由面的波长也随之增大.     

HYDRAULIC CHARACTERISTICS OF WATER-WINGS FOR THE MIDDLE-PIER OF A DISCHARGE TUNNEL

1. INTRODUCTION In the design of a discharge tunnel with high water head and large flow, it is important to study the cavitation and the energy dissipation, such as the prevention of cavitation for slots of various gates [1-4], the effects of entrained ai…     

NUMERICAL SIMULATIONS OF 2D PERIODIC UNSTEADY CAVITATING FLOWS

1. INTRODUCTION Cavitation is a natural phenomenon especially existing in liquids. A cavitating flow generally involves a large number of vapor structures such as bubbles or vortices which are convecting downstream. When they reach high pressure zones, th…     

二维兴波水翼水动力预报的涡分布法

本文用奇点面分布法预报二维自由面边界下水翼的水动力特性。采用线性化的自由面边界条件。水翼表面划分为若干单元，每个单元上布置线性分布的涡，并在其中点满足Ｎｅｕｍａｎｎ型物面边界条件。与试验结果比较表明，计算结果是合理的，本计算方法能显示二维兴波水翼水动力特性与Ｆｒｏｕｄｅ数，相对浸深和攻角的关系。