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Old   January 15, 2002, 10:10
Default Hello,I'm a newby
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Hello all, apologize for my poor english. Do somone know if is possible to have an outlet object whit the escape direction NOT normal to the outlet surface? Example: In a q1 file genereted bi vr editor, in grop 13 "boundary condition.." the object is described as:

PATCH(OBJ3 ,SOUTH,1,10,1,1,1,3,1,1) COVAL(OBJ3 ,P1 , 1.000E+00, 0.000E+00) COVAL(OBJ3 ,U1 , 0.000E+00, 1.000E+00) COVAL(OBJ3 ,V1 , 0.000E+00, 1.000E+00) COVAL(OBJ3 ,W1 , 0.000E+00, 0.000E+00) COVAL(OBJ3 ,TEM1, 0.000E+00, 0.000E+00)

the velocities in X and Y directions are 1 m/s the resultant velocity should be oblique with an inclination of 45 but when i visualize the result the vectors are perpendicular at the outlet surface. Do you Understand me? Please let me know. Fabio.
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Old   January 16, 2002, 20:38
Default Re: Hello,I'm a newby
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I understand your problem.

Are there any other objects in the domain that may be restricting the domain flow out of the outlet ?

Have you tried ?

1) Doing the saming thing with an inlet - this should show you what is going on better than an outlet.

The exhaust flow of an outlet may be different to what was specified by the domain as exhaust flows are affected by the objects in the domain, the domain size ... where as the inlet does not have these problems.

2) tryplacing an outlet in the middel of the domain. This also should help with your understanding of visulising of what is going on.

I have had similar problems myself and these are the steps I took to understanding what was going on.

I also tried increasing the velocities and making the x and y velocities an order of magnitude different to see the impact.

I hope this helps.

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Old   January 17, 2002, 10:27
Default thanks Leon.I'll try - no txt
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Thanks Leon
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Old   January 18, 2002, 08:23
Default Re: Hello,I'm a newby
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Dear Fabio

Try this

(a) Declare your outlet region as "user defined" object.

(b) Go to the "properties" and include into the "user patch":

1- For pressure: CO=fixflu and VAL="the outgoing mass flux" (you should know the outlet fluid density).

2- For velocities: CO=onlyms and VAL="their values, having into consideration the sign" (you use SOUTH type and then you should have a negative velocity value at V1).


(a) If you want an "open" bc. with pressure value 0.0, it is safer to use CO=1000*fixp instead of fixp (fixp=1.0).

(b) If you put CO=0.0 (as you have for velocities), then you eliminate the source term corresponding to the bc. for those variables. Consecuently, you could have an erroneous result or no outgoing flux.

(c) The condition you have for temperature is useless. You are adding a zero.


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