一种非连续流场的数值模拟方法的提出和应用

A numerical simulation method of discontinuous flow field proposed and applied

在计算流体力学(CFD)的瞬态模拟中,流场的连续性是一个重要的先决条件。然而,连续的流场在某些条件下会被分离,例如从阀门打开到重新关闭的过程。现有的方法通常会留下一个狭窄的空隙来近似完全关闭的状态,这将引入一个偏差。为了解决这个问题,文中提出了一种全关闭的数值模拟(Full Closing Numerical Simulation,FCNS)方法来解决非连续流场(Discontinuous Flow Field,DFF)和连续流场(Continuous Flow Field,CFF)之间的数值模拟问题。该方法应用MATLAB作为服务器会话与Fluent通信,以自动调用Fluent的文件并自动执行基于文本的用户界面(Text-based User Interface,TUI)命令。径向基函数(Radial Basis Function,RBF)被用来构建流场变量与网格节点坐标之间的关系,从而实现从DFF到CFF的数据传输。当物理量达到设定值时,通过在MATLAB程序、Scheme语言和用户自定义函数(UDF)之间传递变量,实现瞬态计算的自动停止。基于这种方法,对一个闸阀的二维模型进行了动网格的瞬态模拟,模拟了阀门从开启到关闭的过程,通过这种方法得到了阀门内的速度分布和压力分布,使用FCNS方法使从DFF到CFF的动态数值模拟成为可能。

In transient simulations of Computational Fluid Dynamics(CFD),the continuity of the flow field is an important prerequisite.However,continuous flows can be separated under certain conditions,such as the process from valve opening to reclosure.The existing method usually leaves a narrow gap to approximate the full closing status,which will introduce a deviation.To address this issue,a full closing numerical simulation method(FCNS)is developed to solve the problem of simulation between Discontinuous Flow Field(DFF)and Continuous Flow Field(CFF).The MATLAB program has been used to communicate with Fluent as a server session to call the files of Fluent and automatically execute Text-based User Interface(TUI)commands.The Radial Basis Function(RBF)is used to construct the relationship between the variables of flow field and the coordinates of mesh nodes,which can achieve the data transmission from a DFF to CFF.Automatic stopping of transient calculations is realized by passing variables among MATLAB program,Scheme language,and user-defined functions(UDF)when a physical quantity reaches a set value.Based on this method,a transient simulation of a 2-D model of a gate valve with a dynamic mesh was performed to simulate the process of the valve from opening to closing,and the velocity distribution and pressure distribution inside the valve were obtained by this method,the flow characteristics through the valve are obtained by using this method.This paper makes it possible to use FCNS for understanding dynamic characteristics from DFF to CFF.