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附面层抽吸位置对翼型绕流分离控制的影响张旺龙;谭俊杰;陈志华;任登凤【摘要】为了深入研究抽吸作用位置对翼型绕流分离控制效果的影响,采用HLLC 格式和双时间步长LU-SGS隐式算法对二维可压N-S方程进行数值求解,数值模拟了雷诺数Re为6 000时,NACA0012翼型在上翼面抽吸控制下的翼型绕流流场.研究了抽吸区域位置对翼型流动分离和翼型气动性能的影响.结果表明:同一抽吸系数下,合理的抽吸位置是有效改善翼型气动性能的重要因素,并且不同抽吸位置的作用机制不同.对于以开式分离为特征的NACA0012翼型绕流,其合理抽吸区域位于翼型前缘分离区内.【期刊名称】《南京理工大学学报（自然科学版）》【年(卷),期】2013(037)005【总页数】6页(P710-715)【关键词】附面层;抽吸位置;翼型绕流;分离控制【作者】张旺龙;谭俊杰;陈志华;任登凤【作者单位】南京理工大学能源与动力工程学院,江苏南京210094;南京理工大学能源与动力工程学院,江苏南京210094;南京理工大学瞬态物理国家重点实验室,江苏南京210094;南京理工大学能源与动力工程学院,江苏南京210094【正文语种】中文【中图分类】V211.3低雷诺数下的绕翼型非定常流动研究在飞行器设计中有着重要作用[1]。
随着高空无人飞行器和微型飞行器的不断发展，高空低雷诺数条件下高升阻比翼型的气动设计问题日益凸显，深入研究并控制翼型在低雷诺数条件下广泛存在的层流附面层分离现象，是提高低雷诺数下飞行器性能的迫切需要。
在低雷诺数条件下，翼型绕流常常处于层流状态，其抵抗逆压梯度的能力较弱，容易产生分离等非定常现象，对翼型的升阻力等气动性能产生严重的影响。
针对这种情况，人们一直在寻求有效控制流动的方法，试图通过改变飞行器边界层的流动结构，以达到消涡、减阻和提高推进效率及飞行稳定性的目的。
而在翼型吸力面开孔形成缝隙多孔表面，通过抽吸方式吸除一部分低能流体，延迟逆压梯度发生，减小壁面处速度剖面的曲率，可以达到抑制边界层分离[2]，减少流动损失，实现对翼型流动控制的目的。
abaqus接触分析abaqus—接触分析(转)已有 264 次阅读2010-8-24 19:39 |1、塑性材料和接触面上都不能用C3D20R和C3D20单元，这可能是你收敛问题的主要原因。
如果需要得到应力，可以使用C3D8I (在所关心的部位要让单元角度尽量接近90度)，如果只关心应变和位移，可以使用C3D8R, 几何形状复杂时，可以使用C3D10M。
2、接触对中的slave surface应该是材料较软，网格较细的面。
3、接触面之间有微小的距离，定义接触时要设定“Adjust=位置误差限度”，此误差限度要大于接触面之间的距离，否则ABAQUS会认为两个面没有接触:*Contact Pair, interaction="SOIL PILE SIDE CONTACT", small sliding,adjust=0.2.4、定义tie时也应该设定类似的position tolerance: *Tie,name=ShaftBottom, adjust=yes, position tolerance=0.15、 msg文件中出现zero pivot说明ABAQUS无法自动解决过约束问题，例如在桩底部的最外一圈节点上即定义了tie，又定义了contact, 出现过约束。
解决方法是在选择tie或contact的slave surface时，将类型设为node region, 然后选择区域时不要包含这一圈节点(我附上的文件中没有做这样的修改)。
6、接触定义在哪个分析步取决于你模型的实际物理背景，如果从一开始两个面就是相接触的，就定义在initial或你的第一个分析步中;如果是后来才开始接触的，就定义在后面的分析步中。
边界条件也是这样。
7、我在前面上传的文件里用*CONTROL设了允许的迭代次数18，意思是18次迭代不收敛时，才减小时间增量步(ABAQUS默认的值是12)。
一般情况下不必设置此参数，如果在msg文件中看到opening和closure的数目不断减小(即迭代的趋势是收敛的)，但12次迭代仍不足以完全达到收敛，就可以用*CONTROL来增大允许的迭代次数。
钢质固定平台，是目前海上油（气）生产中应用最多的一种结构形式。
钢质固定平台中最多的是导管架式平台，主要由三大部分组成：导管架、桩和甲板组块[1]。
导管架式平台一般都是在陆地进行建造然后再装船拖运到海上安装。
装船方式有直接吊装上船、小车装船（Self-Propelled Modular Transporter，SPMT）和拖拉滑移上船三种方式[2]。
采用直接吊装上船法，一般甲板都是直立建造的，并在其顶部设置有吊点。
该方式在施工前要求平台建造方位与运输驳船靠码头时的方位协调一致，尽量减少起吊过程中浮吊的旋转，同时受吊装用驳船浮吊实际吊装能力限制[3]。
小车装船需考虑小车分组设计，而对于小车分组及布置问题，还没有详细的理论作为设计基础[4]，且目前工程上应用小车装船的主要是1000t左右的小型模块。
在工程实际应用中考虑到场地实际情况、平台的总重相对较大以及吊装用驳船浮吊实际吊装能力，结合经济成本，大部分平台均需采用拖拉滑移方式上船[5]。
由于平台拖拉滑移上船是一个过程，在此过程中要考虑到各种情况的出现，到目前为止关于平台拖拉滑移上船工况边界条件的模拟还没有一个统一的做法。
本文以四腿四桩甲板组块滑移装船为例，分别采用工程实际应用中较为普遍的3种方式模拟边界条件，并对计算结果加以对比，得出一些具有指导意义的建议。
1 边界条件模拟方法分析由美国Bentley公司开发研制的SACS（Structural Analysis Computer System）软件专门用于海洋结构工程的静动力结构分析[6]，目前国内外导管架式平台普遍采用该软件进行结构设计。
海洋平台组块码头滑移装船过程，是海洋工程施工作业过程中一个非常关键的组成部分，一旦出现事故，将造成无法估量的损失。
海洋平台上部组块的滑移装船工况计算是组块安装作业中的一个临时工况，在用SACS软件对该工况受力情况进行模拟时，边界条件一般采用设置GAP单元的形式。
组块的滑移装船主要是在码头驳船上的线性绞车牵引下组块连同滑靴一起滑移到驳船上事先设置好的滑道上，再由驳船将其运送到指定海域与导管架进行组对。
flow simulation边界条件在流体模拟中，边界条件是指在流场中确定流体流动特性的条件。
边界条件分为两大类：入口边界条件和出口边界条件。
入口边界条件用于确定流体进入流场的初始状态。
常见的入口边界条件有：1. 速度边界条件（Velocity boundary condition）：指定流体进入流场的速度分布。
2. 压力边界条件（Pressure boundary condition）：指定流体进入流场的压力分布。
3. 温度边界条件（Temperature boundary condition）：指定流体进入流场的温度分布。
4. 流量边界条件（Mass flow rate boundary condition）：指定流体进入流场的质量流量。
除了入口边界条件外，出口边界条件还用于确定流体离开流场时的特性。
常见的出口边界条件有：1. 压力出口边界条件（Pressure outlet boundary condition）：指定出口处的压力。
2. 流量出口边界条件（Mass flow outlet boundary condition）：指定出口处的流体质量流量。
3. 常压出口边界条件（Atmospheric pressure outlet boundary condition）：将出口处视为常压条件。
其他常见的边界条件还包括：1. 对称边界条件（Symmetry boundary condition）：假设流场对称，使流过对称边界时速度、压力等参数满足对称要求。
2. 壁面边界条件（Wall boundary condition）：指定流场与固体墙壁接触时的流动状态，通常要考虑壁面摩擦对流体的影响。
3. 切向旋转平均边界条件（Tangential average boundary condition）：常用于旋转机械中，用于对流场的切向部分进行平均处理。
4. 界面边界条件（Interface boundary condition）：用于模拟不同相流体之间的界面，常用于多相流动模拟中。
使用AnsysFluent进行流体力学仿真教程Chapter 1: Introduction to ANSYS FluentIn this chapter, we will provide an overview of ANSYS Fluent and explain its importance in the field of fluid dynamics simulation. ANSYS Fluent is a powerful computational fluid dynamics (CFD) software used for simulating and analyzing fluid flows. It enables engineers and scientists to study the behavior of fluids, predict their performance in various scenarios, and optimize the design of systems involving fluid flow.Chapter 2: Pre-ProcessingThe pre-processing stage involves preparing the geometry of the system and defining the desired fluid flow conditions. ANSYS Fluent provides a variety of tools to import and manipulate geometry files, such as creating boundaries, defining initial conditions, and specifying material properties. Additionally, it allows users to create a mesh grid that discretizes the computational domain into smaller elements for accurate simulations.Chapter 3: Boundary ConditionsBoundary conditions play a crucial role in defining the behavior of the fluid flow simulation. In this chapter, we will explain the different types of boundary conditions available in ANSYS Fluent, including velocity inlet, pressure outlet, wall, and symmetry. Each boundarycondition has specific input parameters that need to be defined, such as velocity magnitude, pressure, and temperature.Chapter 4: Solver SettingsThe solver settings determine the numerical methods used to solve the fluid flow equations in ANSYS Fluent. This chapter will introduce the various solver options available, including pressure-based and density-based solvers. It will also discuss the importance of convergence criteria and the influence of physical properties, such as turbulence models and turbulence intensity.Chapter 5: Post-ProcessingOnce the simulation is complete, post-processing is performed to analyze and visualize the results. In ANSYS Fluent, users have access to a range of post-processing tools, such as contour plots, vector plots, velocity profiles, and pressure distribution. This chapter will explain how to interpret these results to gain insights into the fluid flow behavior and make informed design decisions.Chapter 6: Advanced FeaturesIn this chapter, we will explore some of the advanced features of ANSYS Fluent that can enhance the accuracy and efficiency of fluid flow simulations. These include multiphase flow simulations, combustion modeling, heat transfer analysis, and turbulence modeling. We will provide step-by-step instructions on how to set up and run simulations using these advanced features.Chapter 7: Case StudiesTo further illustrate the capabilities of ANSYS Fluent, this chapter will present a series of case studies involving different fluid flow scenarios. These case studies will cover a range of applications, such as fluid flow in pipes, aerodynamics of a car, and natural convection in a room. Each case study will include the problem statement, simulation setup, and analysis of the results.Chapter 8: Troubleshooting and TipsANYS Fluent, like any software, can sometimes encounter issues or produce unexpected results. In this chapter, we will discuss common troubleshooting techniques and provide tips for optimizing simulation setup and improving simulation accuracy. This will include techniques for mesh refinement, convergence improvement, and understanding error messages.Conclusion:ANSYS Fluent is a powerful tool for conducting fluid dynamics simulations. In this tutorial, we have covered the fundamental aspectsof using ANSYS Fluent, including pre-processing, boundary conditions, solver settings, post-processing, advanced features, and troubleshooting. By following this tutorial, users can gain a solid foundation in conducting fluid flow simulations using ANSYS Fluent and leverageits capabilities to analyze and optimize fluid flow systems in various applications.。
Defining object boundary conditionsBoundary conditions are specified and enforced at nodes in the finite element mesh. The basic procedure for setting any boundary condition except Contact is the same:1.Select the appropriate condition type.2.Select the direction (where applicable).3.Select the nodes to which boundary conditions will be applied usingone of the selection tools in the lower left button bar.4.Apply the boundary conditions.The selected nodes will be highlighted. To apply the boundary conditions click the Generate BCC's button. Colored markers will highlight the nodes to which boundary conditions have been applied. To delete specific boundary conditions, select the start and end nodes, and click the Delete BCC's button. To delete all boundary conditions of the specified type and direction, click the Initialize BCC's button.Note : You can either select faces of the surface by using the surface patches feature or use the node button to select individual nodes.Deformation boundary conditionsVelocityVelocity of each node can be specified independently in the x and y directions (or x, y, and z directions in 3d). Velocity boundary conditions are normally set to zero for symmetry conditions (see section on symmetry in this manual), but may also be set to a specified non-zero value for processes such as drawing in which a workpiece is pulled through a die.ForceForce boundary conditions specify the force applied to the node by an external object. The force is specified in default units. For die stress analysis, the force that the die exerted on the workpiece can be reversed and interpolated onto the dies by using the interpolation function. Refer to the tutorial labs on die stress analysis for a detailed procedure for using force interpolation to perform die stress analysis.PressureThe pressure boundary conditions specifies a uniform, or linearly varying, force per unit area on the element faces connecting the specified nodes. Displacement and shrink fitA specified displacement can be specified in any direction for each node. This is frequently used for specifying shrink fit conditions between a die insert and a shrink ring. More information on this is available in the section on die stress analysis in this manual.MovementThe movement of nodes on an object can be specified. If the movement boundary condition is specified, object movement controls must also be specified.ContactThe Contact boundary condition displays interobject boundary contact conditions on a given object. The user should gain some experience with DEFORM before using this option. The contact conditions are stored in three components to represent the fact that there are three degrees of freedom for any given node.ThermalHeat exchange with the environmentThis boundary condition specifies that heat exchange between element faces bounded by these nodes and their environment should occur. The contact boundary condition determines whether exchange will occur to the ambient atmosphere or to a contacting object.Heat fluxSpecifies an energy flux per unit area over the face of the element bounded by the nodes. Units are energy/time/area.Nodal heatSpecifies a heat source at the given nodes. Units are energy/time. TemperatureSpecifies a fixed temperature at the given nodes.Heat Exchange windowsThis function allows the user to define heat exchange conditions for local areas on a body by use of three dimensional window. To use heat exchange windows, perform the following actions:1.Go to the Boundary Conditions window.2.Select the Thermal tab.3.Select the Heat exchange windows button.4.Note the tools in the lower left corner of the display windowchanges and the new heat exchange window that comes up.5.At this point, heat exchange windows can be defined using the toolsin the lower left corner of the display window. Each window has its ownlocal environmental temperature, convection coefficient and emissivity.See Figure for an example heat exchange window.6.You can define up to 20 independent windows by the method. If tworegions share the same space, the lower number window wins. Diffusion [DIF]Diffusion with the environmentSpecifies diffusion of the dominant atom through the boundary elements bordered by the indicated nodes. Environment dominant atom content and surface reaction rate are specified under the Simulation Controls, Processing Conditions menu. Environment content and reaction rate for various regions of the part may be modified by using diffusion windows.Fixed atom contentSpecifies a fixed dominant atom content at the given nodes.Atom fluxSpecifies a fixed dominant atom flux rate over the elements bordered by the indicated nodes.2.4.11. Contact boundary conditionsContact boundary conditions are applied to nodes of a slave object, and specify contact between those nodes and the surface of a master object (see master-slave relationships under the Interobject data section). If a node is specified to be in contact with a particular object, it will placed on the surface of that object. If this requires changing the position of that node, it will be changed as necessary. Contact boundary conditions are generated under the InterObject , Contact Boundary Conditions.It is for this reason that the user should be VERY careful with how contact is specified. If it is improperly used, the mesh may be damaged and very often remeshing cannot aid this situation since the AMG cannot interpret the users intentions.Contact boundary conditions can be displayed for a given object using the Objects, Boundary Conditions, Advanced Deformation BCC's icon.。
