a question about usrscalar in cfx4.4

August 22, 2003, 05:00

I added a usr scalar and the program gives me an error message in .fo file:
:>MODEL BOUNDARY CONDITIONS ***> ERROR THE FLUID HAS A VERY HIGH LAMINAR PRANDTL NUMBER FOR SCALAR 1.

YOU WILL NEED TO SET THE LOGLAYER CONSTANT AND THICKNESS YOURSELF THE FORMULA RECOMMENDED BY THE MANUAL IS NOT SUITABLE IF ALL WALLS HAVE ZERO FLUX THEN THE SOLUTION IS INDEPENDENT OF THE VALUES CHOSEN THE CFX-4 SOLVER HAS BEEN STOPPED BY SUBROUTINE SPEC1 what is the possible reason about this?Thanks

September 12, 2003, 23:23

Bill,

CFX-4 calculates a wall Prandtl number based on the Jayetellique (sp?) correllation. It only has an affect if you have a scalar flux condition at the wall boundaries (i.e. disolving or adsorbing walls). You can over-ride this with a Log layer constant and thickness of say 1 in the command language. This will bypass the error message and, as long as there's no scalar flux at the walls, there should be no affect on the solution.

Jeff

September 19, 2003, 04:48

thank you,jeff

August 22, 2003, 05:00	a question about usrscalar in cfx4.4	#1
bill Guest Posts: n/a	I added a usr scalar and the program gives me an error message in .fo file: :>MODEL BOUNDARY CONDITIONS ***> ERROR THE FLUID HAS A VERY HIGH LAMINAR PRANDTL NUMBER FOR SCALAR 1. YOU WILL NEED TO SET THE LOGLAYER CONSTANT AND THICKNESS YOURSELF THE FORMULA RECOMMENDED BY THE MANUAL IS NOT SUITABLE IF ALL WALLS HAVE ZERO FLUX THEN THE SOLUTION IS INDEPENDENT OF THE VALUES CHOSEN THE CFX-4 SOLVER HAS BEEN STOPPED BY SUBROUTINE SPEC1 what is the possible reason about this?Thanks

September 12, 2003, 23:23	Re: a question about usrscalar in cfx4.4	#2
jeff Guest Posts: n/a	Bill, CFX-4 calculates a wall Prandtl number based on the Jayetellique (sp?) correllation. It only has an affect if you have a scalar flux condition at the wall boundaries (i.e. disolving or adsorbing walls). You can over-ride this with a Log layer constant and thickness of say 1 in the command language. This will bypass the error message and, as long as there's no scalar flux at the walls, there should be no affect on the solution. Jeff

September 19, 2003, 04:48	Re: a question about usrscalar in cfx4.4	#3
bill Guest Posts: n/a	thank you,jeff

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