# Roughness

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 September 9, 2004, 07:00 Roughness #1 TJ Guest   Posts: n/a Hello, How can I prescribe loglaw condition for a blockage when I have a fully rough atmospheric profile specified at the inlet? Thanks in advance

 September 10, 2004, 05:21 Re: Roughness #2 Mick Hughes Guest   Posts: n/a Hello, I dont understand what your inlet profile has to do with specifying wall conditions on any blockages inside your domain? I guess I have completely misunderstood? However I'll just say the following as it might help. Phoenics calculates wall boundary conditions on solid blockages by default if EGWF=T in your Q1. The wall roughness can be set by the parameter WALLA, and the type of boundary condition applied by default is the Loglaw. The type of boundary condition can be changed by setting the variable WALLCO. Hope this helps

 September 10, 2004, 08:47 Re: Roughness #3 tj Guest   Posts: n/a Thanks for the help Mick and sorry for being unclear in my problem description. You see in order for me to prescribe the correct inlet profile I must set WALLA = the surface friction lenght Zo (in my profile equation), this is a global roughness height and is thus applied to all other surfaces in the domain. To try and combat this I have done the following; WALLA=0.0 WALLCO=GRND2 EGWF=T I've created a patch for the floor level PATCH (GROUND1,LWALL,...) COVAL (GROUND1,V1,GRND5,0.000000E+00) COVAL (GROUND1,KE,GRND5,GRND5) COVAL (GROUND1,EP,GRND5,GRND5) SPEDAT(SET,ROUGHNESS,GROUND1,R,Zo) I was hoping that this prescribes a fully rough condition at the floor and the LogLaw to all other surfaces, but it seems that I am getting an incorrect solution when I do this. Can you see from this what I am doing wrong? Thanks very much Mick

 September 13, 2004, 03:11 Re: Roughness #4 Volker Guest   Posts: n/a Hi, one may use the following for the ground boundary condition (example, one patch with Z0=0.4): PATCH(r01038,SWALL,89,113,1,1,200,200,1,lstep) coval(r01038,U1,grnd5,0) coval(r01038,V1,grnd5,0) coval(r01038,W1,grnd5,0) COVAL(r01038,EP,GRND5,GRND5) COVAL(r01038,KE,GRND5,GRND5) SPEDAT(SET,ROUGHNESS,r01038,R,0.4) Hope this helps regards Volker