Fluent UDF介绍.ppt

Fluent Incorporated 10, Cavendish Court Lebanon, NH 03766 Presentation Outline Introduction to UDFs Introduction to C Programming Writing and Using UDFs Examples Conclusion Why Build UDFs? Standard interface can not be programmed to anticipate all needs Customization of boundary conditions, source terms, reaction rates (volume and surface), properties Solution Initialization Adjust functions (once per iteration) Solve for User Defined Scalars Modify Dispersed Phase Model parameters Many more... Limitations Not all solution variables or solver models can be accessed by UDFs Example: Cannot change specific heat (would require additional solver capabilities) FLUENT5 is a Major Advance UDF’s in FLUENT/UNS 4.2 and RAMPANT could be used to model User defined source terms User defined profiles (Boundary Conditions) User defined properties User defined reaction rates UDF’s in FLUENT 5.0 can be used to model all of the above and Interpreted and compiled code User defined scalars Initialization, adjust, wall-heat-flux functions Various DPM parameters Interpreted vs. Compiled Code Interpreter - It is a large program and sits in the computer’s memory Executes code on a “line by line” basis instantaneously Advantages - does not need a separate compiler Disadvantage - slow and takes up space in memory Compiler - Code is translated “once” into machine language (object modules) Efficient way to run UDF’s: Uses Makefiles Creates “shared libraries” linked with the rest of the solver Overcomes interpreter limitations e.g. mixed mode arithmetic, structure references etc. A Brief Introduction to ‘C’ C functions C data types Pointers and arrays Expressions and statements C arithmetic and logical operators Control flow C preprocessor directives The Basic Form of a C Function Recap of Basic Form All C statements must end with a semicolon (;) Comments are delineated by the character sequence /* ... */ comments can be placed anywhere in a C listing use comments liberally to document your