基于ICEM CFD对交叉管道流场网格划分方法的选择

网格的划分是实现数值仿真模拟最重要的一步,网格质量的好坏直接影响到整个数值模拟的结果,网格划分方法又是决定网格质量好坏的关键环节。为了提高ICEMCFD对交叉管道流场网格划分的质量,本文就某一垂直的交叉管道的网格剖分提出了三种方法,即分别用四面体网格、六面体网格和混合网格对交叉管道进行网格剖分,结果表明采用混合网格剖分的方法能达到理想的效果。     

船用散热器空气流动的数值模拟

基于标准k-ε湍流模型,分别采用正交六面体结构化网格与四面体非结构化网格进行网格划分,使用有限体积法对船用空气散热器内部腔室的流动进行数值计算,模拟散热器各个出口冷却气流的流动情况。比较发现,采用正交六面体结构化网格的计算结果的精度要高于四面体非结构化网格,其仿真更加逼近真实的流动状态。采用六面体网格划分进行数值模拟,发现气流在出口处所受到的喷管效应且气流的形态成直线,各出风口的出风量通过阶梯型设计处于均匀分布状态。     

SUBOFF潜艇回收AUV流场的数值计算

由于水下远距离传递信息困难,以及受自身携带能源的限制,水下无人航行器(AUV)需要通过母船回收进行能源补充与信息传递.为研究AUV水下回收时的复杂流场,本文基于STAR-CCM+软件,采用重叠网格技术对于潜艇回收AUV时的流场进行研究,分析了AUV在回收过程中受到的压力、流场中的漩涡和速度分布等水动力性能,为水下回收AUV提供了有益的参考.     

CFD动态网格技术在水下航行体非定常操纵运动预报中的应用研究

针对水下低速航行体非定常操纵运动中雷诺数及水动力系数随时间变化这一特点,文章采用基于动态网格技术的CFD数值方法对其进行运动模拟.通过对传统动态混合网格模型进行发展,提出了一种改进的动态混合网格模型,以此建立了非定常操纵运动数值预报方法.为验证所建立的数值预报方法对水下低速航行体操纵运动水动力的预报精度,并以带攻角均匀直航的滑行状态为研究对象,应用动网格技术对一典型水下低速航行体缩比模型主体及带附体的水动力进行了计算,结果与风洞模型试验结果吻合较好;文中进而将其应用于一水下滑翔机自航模非定常运动的预报,结果与试验符合较好,初步验证了动网格技术的应用能力和所建立的预报方法的有效性.文中的工作可以为水下航行体及其自航模非定常操纵运动的数值模拟提供基础.     

新型深吃水多立柱FDPSO变截面立柱涡激运动特性研究

文章采用FLUENT软件结合分离涡法对某新型深吃水多立柱FDPSO变截面立柱涡激运动特性开展了研究。将变截面立柱涡激振动系统简化为质量-弹簧-阻尼模型,引入雷诺平均应力模型求解不可压缩粘性Navier-Stokes方程,通过计算出流场作用于柱体的瞬时升力与阻力,并基于UDF程序求解运动微分方程同时运用动网格技术实现流场更新,实现了对变截面立柱涡激运动的数值模拟。对不同来流速度下变截面柱绕流和涡激运动特性进行了研究,分析了变截面柱阻力系数、升力系数、运动幅值和运动轨迹等,研究发现：在高雷诺数单柱绕流模拟中采用三维数值模型更具优势,变截面柱后方同一时间内可能有多个旋涡产生,旋涡之间相互影响,抑制了旋涡对柱体的升阻力作用;在折合速度6~9范围内,变截面柱未出现明显“锁定”现象;变截面柱涡激运动的横荡振幅峰值在Ur=4.5,约为1.2D;变截面柱流向平衡位置随着折合速度增加而增加;变截面柱运动轨迹出现了典型的“8”字形,但变截面柱的轨迹相对较紊乱。     

螺旋桨在均匀流场中的非定常水动力数值模拟

采用滑移网格技术,使用基于求解RANS方程的CFD软件数值模拟均匀流场中的螺旋桨非定常水动力性能.为了真正实现螺旋桨的旋转运动,在计算过程中采用定长多运动参考系模型计算出初始流场,再用滑移网格模型完成整个计算.数值计算得到的推力系数和转矩系数与实验结果吻合良好,验证了该方法应用于螺旋桨水动力性能研究的可行性.     

混合网格在滑行艇阻力数值模拟中的应用

为探讨适用于滑行艇全航速段数值模拟的网格划分方法,本文采用CFD技术研究了混合网格在滑行艇阻力数值模拟中的适用性,采用了不同数量的混合网格对滑行艇粘性绕流场进行了数值模拟,对阻力进行了计算,并且对比了不同网格数量对计算结果的影响,分析了其中的原因,得到了适用于滑行艇阻力数值计算的混合网格。在此基础上采用所得到的网格划分方式对滑行艇全航速段进行了数值模拟,并与实验结果进行了比较,两者吻合较好。     

三维圆柱体绕流数值模拟流场选择及网格划分

文章通过数值模拟结果确定适合的三维圆柱体绕流流场的尺寸,采用不同的计算流体力学(CFD)软件对有限元模型进行网格划分,对比网格划分质量的优劣,选择适合数值模拟的软件CFX。确定采用的网格形式为六面体网格(Hex8)以及流场不同部分网格的尺寸。圆柱绕流展向各截面平均压力系数沿周向无明显变化,脉动压力系数变化显著,绕流后的旋涡发放形式具有明显的三维特性的数值模拟结果验证了本文的流场选择和网格化分尺度的合理性。     

基于CFD(计算流体动力学)的两栖车绕流场模拟

利用计算流体动力学理论,对不计自由面的两栖车辆的粘性绕流场进行了数值模拟,重点介绍了关键的SST k-ω湍流模型和混合网格布置方法.计算结果基本与实验数据吻合,表明用数值模拟的方法对两栖车的车周流场与受力进行研究有很好的应用前景.     

基于重叠网格的重水潜器粘流数值模拟

文章结合一种密度大于水的新型潜器—重水潜器（Heavier-than-water AUV,简称 HTW）,采用 RANS 方法和重叠网格计算了该潜器的水动力性能和绕流流场。文中计算了不同攻角和漂角情况下重水潜器的阻力、升力及俯仰力矩,对其周围流场水动力学性能进行了分析,并通过流场的流动结构研究了受力随姿态变化的规律。文中将采用重叠网格方法的计算结果与 FLUENT 计算值以及风洞试验结果进行了比较,表明重叠网格方法可较好地模拟重水潜器的自由态绕流问题。该研究为该潜器的总体设计与运动控制提供了有价值的参考。     

Improving longitudinal motion prediction of hybrid monohulls with the viscous effect

A new method improves prediction of the motion of a hybrid monohull in regular waves. Stem section hydrodynamic coefficients of a hybrid monohull with harmonic oscillation were computed using the Reynolds Averaged Navier-Stokes Equations (RANSE). The governing equations were solved using the finite volume method. The VOF method was used for free surface treatment, and RNGК-ε turbulence model was employed in viscous flow calculation. The whole computational domain was divided into many blocks each with structured grids, and the dynamic process was treated with moving grids. Using a 2-D strip method and 2.5D theory with the correction hydrodynamic coefficients allows consideration of the viscous effect when predicting longitudinal motion of a hybrid monohull in regular waves. The method is effective at predicting motion of a hybrid monohull, showing that the viscous effect on a semi-submerged body cannot be ignored.     

粘流方法的螺旋桨尾流场数值分析(英文)

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.     

欠驱动自主水下航行器的镇定及跟踪

针对仅带有轴向推力及偏航力矩的欠驱动自主水下航行器（AUV）,研究了其在水平面内的轨迹跟踪及定点调节问题。基于Lyapunov直接法及串接一反步技术,通过采用一种带有动力学震荡器的跟踪误差变换,设计了一种统一的连续时变状态反馈控制律,并给出了参数自适应更新律以估计AUV的非线性阻力参数,使得AUV的位置及方向角的跟踪误差全局渐近收敛于零点左右的一个邻域内,该区域可以为任意小,并且,AUV的跟踪性能与外界干扰的大小无关。仿真结果证明所提出的方法是有效的。     

载人潜器阻力性能的数值计算和模型试验及船型优化

采用多块结构化网格对某载人潜器模型周围计算区域进行网格离散,采用Realizable k-ε湍流模型对潜器周围绕流场进行数值模拟.在船模拖曳水池中进行载人潜器模型不同艏向角和垂直上升及下潜航行时的阻力试验.将阻力的数值计算结果与试验值进行对比,两者的偏差在可接受范围内.考虑载人潜器主体的舯纵剖面的二维外形,用多岛遗传算法对其粘性流场的阻力数值计算结果进行船型的一体化优化,得到二维阻力最小的优化外形.将舯纵剖面外形的优化结果应用到三维载人潜器主体,比较优化前后的主体阻力.数值计算结果表明,载人潜器主体外形优化前后阻力的优化收效在30%以上.     

近壁面水动力干扰下的AUV运动控制研究

按自治式水下机器人(AUV)需要接近水下工作站并实现坐落的要求,依据平壁面对AUV水动力干扰的力学机理,建立了AUV在平壁面附近运动时的数学模型,并设计了五个自由度运动PID控制器.在海流影响下,通过系统仿真,实现了AUV的五自由度运动控制和准确坐落,仿真结果验证了控制策略的可行性.     

某型AUV运载器的定位方法与误差分析

传统AUV依靠水下惯性导航设备自主定位的方法无法实时进行水下信息感知和系统控制。水声定位是AUV定位导航技术的一个研究领域,可用于水下运动目标定位与导航、水下静止目标勘测等。本文分析阐述三种经典AUV定位方法,进一步研究AUV快速定位解算原理,论证影响AUV运载器在深海工作时产生的定位误差来源并进行仿真试验分析,最终将研究成果应用在目前现有某型AUV运载器上,实现自身水下定位、导航与远程遥控。     

Design and evaluation of a hierarchical control architecture for an autonomous underwater vehicle

This paper researches on a kind of control architecture for autonomous undelwater vehicle （AUV）. After describing the hybrid property of the AUV control system, we present the hierarchical AUV control architecture. The architecture is organized in three layers： mission layer, task layer and execution layer. State supervisor and task coordinator are two key modules handling discrete events, so we describe these two modules in detail. Finally, we carried out a series of tests to verify this architecture The test results show that the AUV can perform autonomous missions effectively and safely. We can conclude the control architecture is valid and practical.     

框架四叉树的自主水下航行器追踪动态目标研究(英文)

An autonomous underwater vehicle (AUV) must use an algorithm to plan its path to distant, mobile offshore objects. Because of the uneven distribution of obstacles in the real world, the efficiency of the algorithm decreases if the global environment is represented by regular grids with all of them at the highest resolution. The framed quadtree data structure is able to more efficiently represent the environment. When planning the path, the dynamic object is expressed instead as several static objects which are used by the path planner to update the path. By taking account of the characteristics of the framed quadtree, objects can be projected on the frame nodes to increase the precision of the path. Analysis and simulations showed the proposed planner could increase efficiency while improving the ability of the AUV to follow an object.     

开发水下机器人控制器的MDA/MBSE方法的实用专业化研究（英文）

The model-driven architecture(MDA)/model-based systems engineering(MBSE) approach, in combination with the real-time Unified Modeling Language(UML)/Systems Modeling Language(SysML), unscented Kalman filter(UKF) algorithm, and hybrid automata, are specialized to conveniently analyze, design, and implement controllers of autonomous underwater vehicles(AUVs). The dynamics and control structure of AUVs are adapted and integrated with the specialized features of the MDA/MBSE approach as follows. The computation-independent model is defined by the specification of a use case model together with the UKF algorithm and hybrid automata and is used in intensive requirement analysis. The platform-independent model(PIM) is then built by specializing the real-time UML/SysML's features, such as the main control capsules and their dynamic evolutions, which reflect the structures and behaviors of controllers. The detailed PIM is subsequently converted into the platform-specific model by using open-source platforms to quickly implement and deploy AUV controllers. The study ends with a trial trip and deployment results for a planar trajectory-tracking controller of a miniature AUV with a torpedo shape.     

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...