Learning Forum

[y.lin]

Hi, nI was advised that there is a UDF macro 'F_STORAGE_R_N3V(f,thread,SV_WALL_SHEAR)' to return a vector for each face on wall boundaries with components representing the shear stresses in xyz-directions and a macro F_P(f,thread) for the normal forces on surface. I checked the Fluent UDF manual but can't find any description on these two macros. May I get more details on it, such as the description, how to use it, and any examples to use them? nMany Thanks.nAnnen

[Rob]

We don't document all of the macros, and therefore can't give any further guidance on a public forum for those not in the manual. One hint, have a look for the header files as they tend to have comments in which might be useful (note, not all are commented and not all are useful!). n

[DrAmine]

Just do a quick search on this forum and you will find what we need (Though, we won't comment on any undocumented macro. Others can chime in)n

[YasserSelima]

I have never seen this macro but it actually agree with part of the documentation ... Under cell Macros, There is a Macro C_STORAGE_R ... and in one of the examples, there is a macro F_STORAGE_R .. both of them returns real values. It makes sense that the one returns vector will look a little different. nYou can test it and see if it works or not ... You can calculate the value of the shear stress using the strain macrosnAlso I believe there are similar macros for the face F_DUDX(f,t) for example ... although they are not documented. Try to calculate the shear stress on the wall using the two methods and print them in one line. Then you can make sure this works..nAnd I appreciate if you update us with what you find.n

[YasserSelima]

F_P(f,t) is available for pressure-based solver. n

[YasserSelima]

One thing I forgot to mention here ... There is an example that integrates the pressure on a surface in the manual .. In Dynamic mesh .. I believe CG Motion .. F_P(f,t) is used in this example.n

[DrAmine]

Edit: removed screenshot from Manual.n

[DrAmine]

F_STORAGE_R_N3V(f,thread,SV_WALL_SHEAR) does store the vector of wall shear stress. Is not documented in the manual as you highlighted. It returns a vector and provides with the wall stress on the facet f of wall thread thread.n