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-   -   VELOCITY INLET (http://www.cfd-online.com/Forums/fluent/30373-velocity-inlet.html)

Pravesh Kumar October 9, 2002 08:44

VELOCITY INLET
 
Hi I am totally confused with velocity inlet. My fluid is coming from the top and coordinate system is +X,+Y,+Z.I am doing it in 2D so Z will not come into picture . Then in velocity inlet panel I should put only velocity or should put it with negative sign As the flow is in -Y direction.

Joon October 9, 2002 09:37

Re: VELOCITY INLET
 
Put "-" if it is -Y direction.

Pravesh Kumar October 9, 2002 12:29

Re: VELOCITY INLET
 
hi If i am putting a -sign in velocity inlet panel then it is showing reverse flow and in vector plot it is showing that vectors are upward for flow of air .But it is not the case as air is coming from top. The boundary condition at top is velocity inlet and at bottom is pressure outlet.Without putting -sign it is coming from top. waiting..............................

Chris October 9, 2002 17:55

Re: VELOCITY INLET
 
Specify the velocity magnitude as a positive value normal to the boundary. Then you do not need to worry about direction.

Chetan Kadakia October 9, 2002 18:48

Re: VELOCITY INLET
 
If you use the direction and magnitude specifications, then you need to say Y velocity is of a negative value. If you are getting reverse flow on the inlet, maybe its the solution is not converged and accurate.

Do you have any obstructions near your inlet? Does your solution converge (if so tell us why you say it has converged).

Let us know what happens.

Good luck!


Pravesh Kumar October 10, 2002 03:53

Re: VELOCITY INLET
 
Dear

I am having granular particles particles inside the domain(say near inlet).But when i am giving negative value of velocity then it is showing Reversed flow in pressure outlet and not converging. While i am doing for positive value of velocity it is ok but it is showing negative magnitude of velocity. I just want this to be positive. Thanks!!

sunny October 10, 2002 22:38

Re: VELOCITY INLET
 
Hi all,

1. First, when you specify the boundary conditions, flow knows where to go. 2. When you specify velocity, specify it has a magnitude, +ve value. 3. How are you looking at your magnitude, it depends on the vector you created for the surface. I mean when you look at a surface monitor. Even if it shows a negative magnitude you know it is positive. 4. All that matters is not the colorful contours and the signs around, first try to understand the physics and try to frame the problem simply with BC'S. 5. HOPE IT WILL BE HELPFULL. sunny


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