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-   -   Pressure Inlet Boundary Condition (http://www.cfd-online.com/Forums/fluent/50280-pressure-inlet-boundary-condition.html)

Prasad January 13, 2009 13:54

Pressure Inlet Boundary Condition
 
Hi everyone,

I'm trying to simulate the flow around a building. I'm not simulating the entire height of the building, but only a portion in the middle.The incoming flow has a velocity variation in the vertical direction (atmospheric boundary layer profile). Therefore, I need to run a 3-D simulation. Hope this helps

I'm using the velocity inlet & pressure outlet BC's for the sides of the domain, and pressure inlet BC for the top and the bottom. I've set the static pressure to be equal to zero (free stream condition) for the pressure outlet. Therefore, I set the total pressure for the pressure inlet to be equal to the dynamic pressure based on the incoming flow velocity.

However, I'm having trouble with the convergence. Also, the static pressure along the velocity inlet is not equal to zero, even though freestream conditions are present there. I'm not sure if I'm specifying something incorrectly.

Thanks in advance,

Prasad

Vijay January 13, 2009 21:20

Re: Pressure Inlet Boundary Condition
 
Yes your static pressure along at the velocity inlet will not be zero since you specified a velocity inlet on the sides. Depending up on your side entrance area it automatically calculates the total pressure where static is not zero.

Your static pressure is zero from top to bottom but what about the air coming from the sides.

Prasad January 14, 2009 01:15

Re: Pressure Inlet Boundary Condition
 
The velocity inlet & pressure outlet BC's are far away from the building, hence, free stream conditions are present. Hence, if I specify zero static pressure at the pressure outlet BC, shouldn't I get the same at the velocity inlet BC?

I've run cases with same configuration, except that instead of the pressure inlet BC, I had specified slip walls. In these cases, the static pressure at both the pressure outlet & velocity inlet was equal to zero. This is the reason why I'm unsure if I'm specifying something incorrectly with regards to the pressure inlet BC.

Thanks, Prasad

Vijay January 14, 2009 13:27

Re: Pressure Inlet Boundary Condition
 
I am also facing the similar kind of problem right now.

qm January 15, 2009 00:50

Re: Pressure Inlet Boundary Condition
 
hi, im simulating external flow (4.5m/s) over a thin trapezoidal flat plate. i'm using velocity inlet BCs for my inlet and top n bottom faces of domain, and pressure outlet for my outlet. these BCs were defined in GAMBIT b4 exporting the mesh to be read in FLUENT.

are my BCs acceptable? i can't achieve convergence. my iterations diverge after 80 iterations.

help!

Meng Wang January 22, 2009 21:58

Re: Pressure Inlet Boundary Condition
 
Hello Everyone,

I have an urgent question about the inlet boundary condition. Is it true that I have to set the inlet flow "direction". I tried pressure inlet and velocity inlet, and both of them require direction specification method. Is there any time of inlet condition that does not require direction? Thank you

immortality April 9, 2013 21:32

hi
whats the procedure of pressure inlet bc process in subsonic inlet?
Which variable is calculated by zero gradient (from internal field) and which is calculated?at some arrangment?
I have read the help but not grasp exactly.
Could anyone help?


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