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1、CF中实现阀从完全关闭到打开这里将会破解他们是如何在CFX中实现阀从完全关闭到打开的过程，解除ansys在技术上的一些锁死。原文作者的原话如下： 当流体模型包括几何运动例如转子压缩机，齿轮泵，血液泵或者内燃机就要求网格的运动。运动网格的策略涵盖了每个可以想得到的运动。特别是在流固耦合计算中涉及固体在流体中的大变形和大位移运动，ANSYS CFX结合ICEMCFD实现外部网格重构功能，用来模拟特别复杂构型的动网格问题并不会产生坏的网格单元，这种运动可以是指定规律的运动，比如汽缸的活门运动事件，也可以是通过求解刚体六自由度运动的结果，配合ANSYS CFX的多构型模拟，可以方便处理活塞封闭和边界接
2、触计算。而且，对于螺杆泵、齿轮泵这种特殊的泵体运动，ANSYS CFX开发了独特的浸入固体方法不需要任何网格变形或重构，采用施加动量源项的方法来模拟固体在流体中的任意运动。基于以上两种动网格策略，用户可以方便地解决任意复杂的动网格问题。这是CFX 12新增的动网格功能。这里我想描述一下Multi-Configuration and Remeshing 的功能。下面是一个带弹簧的活塞1自由度运动，当压力大于弹簧力时，活塞上移，活塞一开始处于封闭状态的，这也是目前CFD网格技术的瓶颈，但是CFX12 在处理这种问题上独辟蹊径，采用多构型和网格重划分结合的办法有效解决这一难题。 下面我们会开始模拟这
3、个过程。在CFD中无法模拟阀由完全关闭到开启的过程，因为这个过程需要由面网格拉伸出体网格才可以实现，在CFX中我们可以通过Multi-Configuration来实现这个过程，而阀一旦开启后，剩下的即可通过remeshing功能来不断改善网格轻松模拟出来。 我们需要准备2套网格和2个ICEM的rpl文件，2套网格分别用于阀关闭和开启2种模拟，而2个rpl文件用来进行结果网格和非结果网格的remeshing。具体如下： 首先是阀完全关闭的模拟，使用的网格如下： 我们可以看出网格的inlet和outlet不在一个域内，这样在求解时会有孤立区域，求解自动停止，所以我们需要设定在求解过程中允许存在孤立
4、区域： 关闭时的具体定义： 瞬态分析： 在阀受到的力大于设定值时，阀门开启，转入unstated分析： 阀门开启后： 在阀的开度非常小时，对模型划分非结构网格将会很困难，所以在开度非常小时，我们使用结构网格进行模拟，开度达到我们设定的值时，转用非结构网格进行模拟。 动网格设置，这里只是做个基础的说明，可以通过wall distant参数让网格变形更均匀。 阀的运动： 进行结构网格和非结构网格的remeshing 调用ICEM进行网格的重构： 结果： ANSYS Tutorial: Workbench CFX Remesh By using a parameterized geometry an
5、d mesh in Workbench a script can be used to re-mesh a geometry based on conditions set in CFX. In this simple example the rotor seen in the figure below will deform the mesh until the value of orthogonally-based quality will trigger remeshing of the domain. Setting up the Workbench project A new wor
6、kbench project containing a geometry and mesh system is needed. Set the parameters you wish to modify in the remeshing process. In this case the rotational angle of the rotor will be changed according to the mesh deformation specified in CFX. Note/change the parameter names of the desired parameters
7、 as they are needed in the coupling between CFX and Workbench. Save and close the Workbench project. If kept open, the remeshing will fail. CFX configuration Several Expressions are needed in order to both move the mesh in CFX and to calculate the parameters needed in Workbench. The green highlighte
8、d expressions in the below figure are related to mesh motion and the red calculates the remeshing angle. In this case we specify a rotational speed of 90 degrees/second. A constant time increment, deltaT, is also defined and used as the simulation timestep. The new x- and y-coordinates xnew and ynew
9、 are used in the mesh deformation found in the domain tab. Remeshing The remeshing is performed by relating monitor expressions in CFX to parameter names in Workbench. In this case we want to create a monitor point called “Angle” the same as in the Workbench project. Under Basic Settings in Solver C
10、ontrol check the Interrupt Control button and enter the condition you wish to set for remeshing. In this case we dont allow an Orthogonality Angle smaller than 10 degrees. Under Configurations, insert a new configurations and under the Remeshing tab enter the remesh commands. The Activation Conditio
11、n is the one from Interrupt Control and the location should be the entire mesh. The External Command performs the remeshing in Workbench using a .wbjn remesh script. The replacement file should be the mesh file in the project directory. External Command: C:Program FilesANSYS Incv130FrameworkbinWin64
12、runwb2.bat -B -R C:WB_Remesh.wbjn. Replacement File: C:dp0globalMECHSYS.mshdb When solving the case the solution is interrupted and remeshed when the element quality is too degraded. If one wishes to run the simulation again the angle parameter in workbench needs to be reset to the original value, otherwise the last angle used in the previous simulation will be used.
