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-   -   Plot a graph of velocity (http://www.cfd-online.com/Forums/openfoam-solving/70974-plot-graph-velocity.html)

wanie December 11, 2009 01:07

Plot a graph of velocity
 
Hi!
I'm new to CFD. I am doing Human Tracheobronchial Airways Flow Model to identify the hotspots for particle deposition in the lungs.
I have a problem on how to plot a graph of velocity against time from our iteration in excel. I ask someone about this and he said that I must identify the main locations to extract velocity data (e.g: create point or surface) using FLUENT coordinate system. But I still do not understand this part and how to do it.
One more, there seems to be some problems with my iteration as it reads "turbulent viscosity limited to viscosity ratio of 1.000000e+005 in 62 cells". There might be some problems in my boundary conditions or conflict with my UDF code.

This is my parameter I set for boundary condition:-
1) Inlet- inlet velocity
-velocity magnitude = 1 m/s
-turbulent intensity = 1 %
-Hydraulic diameter = 0.2 m

2) Outlet- pressure outlet
-gauge pressure = 0
-backflow turbulent intensity = 1 %
-backflow hydraulic diameter = 0.2 m

3) Wall
-no slip condition
-roughness height = 0
-roughness constant = 0.5

and this is my C code for unsteady flow:-

#include "udf.h"

DEFINE_PROFILE(sin_inlet_velocity, thread, position)
{
real x[ND_ND]; /* Position vector */
real y;
face_t f;
real t = CURRENT_TIME; /* Current time of simulation */
begin_f_loop(f, thread) /* Loops over faces in thread */
{
F_CENTROID(x,f,thread); /* Gets centroid of face f */
y = x[1];

t=3;
F_PROFILE(f, thread, position) = 1.84*sin(1.0472*t); /* Profile 1 */

//else (t>=3)
//F_PROFILE(f, thread, position) = 1.84*sin(1.0472*t); /* Profile 2 */

}
end_f_loop(f, thread)

}


I really need someone to help me ASAP. Thanks...

Wanie:confused:

ata December 11, 2009 08:17

Plot a graph of velocity
 
Hi wanie
I think you make some mistake. this forum if for OpenFOAM not FLUENT and may be it is better for you to ask your question in other forum.
However for velocity do you want to monitor velocity at one point or line or surface?
About viscosity ratio limit, in limit (i think it is in define menu) increase max limit for this case. i.e. to 1e10.
May be it works.
Best regards

Ata

wanie December 11, 2009 11:21

many thanks to ata..

i hope your suggestion will work.

Thank you so much

wanie December 13, 2009 06:09

to ata,

yes, i want monitor velocity on a surface.
do you know how to do it?
can you please help me?
thanks...

wanie

ata December 14, 2009 07:58

Plot a graph of velocity Reply to Thread
 
Hi wanie
First if the surface that you want to monitor velocity on it does not exit create it. Do you know how? i.e. you can do this via iso-surface.
Second you must define an animation. If you do not how, tell me to explain it for you. Absolutely you can find it in users manual.
Regards

Ata

hamcer December 17, 2009 17:48

hello to all,
I wd like locate the points which their normal velocity are nul in order to locate the interfas surface between two phases (water and air), but, I can't find a relation between the coordinates points and the velocity vectors.
can any one help me.
Thanks in advance.


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