应用Fluent的UDF二次开发对某隧道安全通风进行设计(2)
Fluent拥有强大的数据处理能力，我们再通过UDF这个端口进行个性化的设置和特殊的模拟需要。这样我们就可以得到一组更加优化的数据。正如文中对数据的处理，定义计算速度为u=0.1*y*（0.001-y）/(0.0005*0.0005)和计算温度为u=0.8/y，提高计算结果的准确性。这样在以后的通风设计中我们可以根据火灾的环境条件，天气因素和人为作用来设计通风设计方案。
由此我们可以得出以下结论：因为 Fluent模拟和分析的流体流动是在理想状况下进行的，如果我们根据其计算结果进行隧道通风设计，那么设计方案将过于理想化。同时，我们也可知道相关源代码的编写有一定难度，没可能每次都进行编译计算。所以，我们采用一个折中的方法每次预留百分之五的余地，就是说在经由Fluent计算的到的基础上乘以0.95这个比例系数。
这样在以后的通风设计中我们的设计方案的安全性将大大提高。
关键词： 特长公路隧道；火灾；数值模拟；Fluent；UDF
Secondary Development of Fluent UDF for Ventilation Tunnel Safety Design
Tunnel ventilation system is essential for highway tunnel to keep a safe, healthy and comfortable. Because of unique structure of highway tunnel, the internal ventilation facilities do not have a reasonable design, the tunnel in the event of fire source, it will cause a lot of casualties and huge economic losses.
In this paper, the method of numerical simulation of fire in a highway tunnel ventilation and smoke were studied. Assumed that there are a fire accident of the long highway tunnel low line pipe occurs when it, the fire source is located in the middle of a tunnel length of 8.9km length of 7.5km at 50MW fire. Long Highway Tunnel in use during normal operation is generated when the traffic entering the tunnel piston wind ; when the tunnel is blocked or fire condition, the start of the tunnel jet fans for makeup air , exhaust port open simultaneously polluting gases inside the tunnel timely discharge. According to preliminary numerical simulation shows three exhaust port open fire and exhaust port spacing is 60m program is scheduled for the most reasonable option.
Fluent is special software to model and analysis of complex geometric area of the fluid flow and heat transfer phenomena. Fluent provides a flexible grid features that can support multiple grid. Users can freely choose to use structured or unstructured grids to divide complex geometric areas, such as support for the two-dimensional problem triangle meshes or quadrilateral mesh; support for the three-dimensional problem tetrahedron, hexahedron, Ling cones meshes; also supports hybrid grids. Users can also use the fluent mesh adaptive features provided in the solution process based on the results obtained to optimize the computer grid.
Although Fluent is powerful, it can not be directly fixed on the options set in the flue gas flow. In this paper UDF of Fluent programming can customize the inlet velocity and temperature curve, so that it can achieve the flue gas flow simulation, UDF is provided to the user as interface by fluent software. Use of UDF on the secondary development of Fluent is able to complete some problem out of the standard modules.
User-defined function, or UDF, is a user directed the program, which can dynamically connect to the fluent solver up to improve performance. User-defined functions written in C language use the DEFINE macro to define. UDF can be used in standard C language library can also be used Fluent Inc. Provides predefined macros by these predefined macros, you can get the data obtained Fluent solver.
UDF use can be interpreted as a function, or a compiled function. Explained UDF deal sounds simple, but there are some inadequate in source code and speed restrictions. Compile UDF executes rapidly, there is no source code restrictions, but is more cumbersome to set up and use. According to this design needs, we choose the way of compiling UDF to steady.