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Old   September 19, 2013, 05:10
Exclamation boundary layer development in gambit
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maaz ahmad
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i am working on wind effects on high rise building..i have to develop boundary layer along the wall on computational domain and building as well...gambit is showing message..initialization failed...with error code 1...i am unable to resolve this..kindly help me...
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Old   September 19, 2013, 06:16
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Maxime Perelli
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more info please, with pictures
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Old   September 20, 2013, 02:25
Default kindly help me out...
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hi max..
i have to develop boundary layer on the ground and building surface..i am attaching pics here,, kindly look into it.. and help me ..out..thanx
whole computational domain.jpg

computational domain from different angles.jpg

high rise building.jpg
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Old   September 20, 2013, 02:33
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then pick surfaces of ground and building...
take care of first cell's height.
If you give an exotic value, then the BL propagation may fail
http://aerojet.engr.ucdavis.edu/gamb..._blayer_create
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Old   September 21, 2013, 04:19
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max thanx for your response...i have changed the geometry of computational domain to resolve the error..
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Old   September 23, 2013, 04:33
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max.. can you tell me about the aspect ratio for boundary layer ....
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Old   September 23, 2013, 04:49
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http://aerojet.engr.ucdavis.edu/gamb...spec_algorithm
with aspect ratio algorithm, you don't have fixed first cell' s height.
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Old   September 24, 2013, 00:32
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no dear the thing i wanna ask is that when we examine the mesh and in the option of quality type we click aspect ratio , then what is the range of this value that is best suited for a mesh.
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Old   September 24, 2013, 02:34
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from Help: "However, a general rule of thumb is to avoid aspect ratios in excess of 5:1. " --> http://aerojet.engr.ucdavis.edu/flue...ug/node155.htm

I would simply load the mesh in the solver and run a check mesh
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Old   September 27, 2013, 03:51
Default problem in udf for velocity proflie
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/************************************************** *********************

vprofile.c UDF for specifying steady-state velocity profile boundary condition

************************************************** **********************/ #include "udf.h"

DEFINE_PROFILE(inlet_x_velocity, thread, position)
{
real x[ND_ND]; /* this will hold the position vector */
real y; face_t f;

begin_f_loop(f, thread) { F_CENTROID(x,f,thread); y = x[1];
(
F_PROFILE(f, thread, position) = (10 + y/12.5)*cos(5.0/180.*3.1415927); }
end_f_loop(f, thread) }

DEFINE_PROFILE(inlet_y_velocity, thread, position)
{
/* insert your own code here*/
}




max....in this udf while defining
F_PROFILE(f, thread, position) = (10 + y/12.5)*cos(5.0/180.*3.1415927);

can we use log formula also, if yes then please explain it for me.....
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Old   September 27, 2013, 05:05
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Quote:
Originally Posted by maaz View Post
/************************************************** *********************

vprofile.c UDF for specifying steady-state velocity profile boundary condition

************************************************** **********************/ #include "udf.h"

DEFINE_PROFILE(inlet_x_velocity, thread, position)
{
real x[ND_ND]; /* this will hold the position vector */
real y; face_t f;

begin_f_loop(f, thread) { F_CENTROID(x,f,thread); y = x[1];
(
F_PROFILE(f, thread, position) = (10 + y/12.5)*cos(5.0/180.*3.1415927); }
end_f_loop(f, thread) }

DEFINE_PROFILE(inlet_y_velocity, thread, position)
{
/* insert your own code here*/
}




max....in this udf while defining
F_PROFILE(f, thread, position) = (10 + y/12.5)*cos(5.0/180.*3.1415927);

can we use log formula also, if yes then please explain it for me.....
Hi maaz,
see attached picture from udf manual.

Daniele
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File Type: png log.png (43.3 KB, 8 views)
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