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how to input Presure Inlet ,with angles

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Old   July 7, 2005, 03:18
Default how to input Presure Inlet ,with angles
  #1
Anju
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Hellooo Evryyy one,

How to input pressure boundary conditions with angles? I mean i know the flow angles in x, y and z direction.i want to input this with total pressure as inlet.

Thanx in advance Anjali
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Old   July 7, 2005, 08:45
Default Re: how to input Presure Inlet ,with angles
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Jason
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In the pressure Inlet... Change the "Direction Specification Method" from "Normal to Boundary" to "Direction Vector". If you know the flow angles, you can calculate the vector components.

Good luck, Jason
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Old   July 8, 2005, 09:04
Default Re: how to input Presure Inlet ,with angles
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Anjali
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Hi jason, than for u r response,

i am Struggling to calculate the components in 3D.In 2D the components would be sin and cos. I haven't got any idea how to calculate in 3D?

I really appreciate if you could throw some light on this

Cheeerrsss Anju
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Old   July 8, 2005, 10:43
Default Re: how to input Presure Inlet ,with angles
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Jason
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If I'm not mistaken, what you have is the coordinate direction angles (sometimes referred to as alpha, beta, and gamma). Where alpha is the incidence angle between the x axis and your vector, beta is the y axis and your vector, and gamma is the z axis and your vector... so the vector components are:

x=cos(alpha) y=cos(beta) z=cos(gamma)

To see this, imagine a plane that goes through the axis of interest, and your direction vector. I'm going to use the x-axis as my example. A point along a plane can be defined by two coordinates... I'm already along the x-axis in one direction, so I will call the other direction y'. Also notice that since my plane is going through the vector and the x-axis, my alpha angle lies directly on this plane, so the x-component of the vector is cos(alpha), and the y' component of the vector is sin(alpha). The y' component is useless though. To see the y and z components, do the same thing where you cut a plane through the axis of interest and the vector.

Hope this is clear enough, Jason
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Old   July 8, 2005, 18:27
Default Re: how to input Presure Inlet ,with angles
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Mehdi Ghoddosy
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Dear Anjali:

You know that pressure is a sclalar an can not have a direction. So, You can not define direction using this boundary condition. You have to use velocity inlet in the case. Also, Janson is discussing about turbulent energy production and disspaton direction not pressure.

Best Regards Mehdi Ghoddosy
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Old   July 9, 2005, 02:59
Default Re: how to input Presure Inlet ,with angles
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Anjali
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Dear Jason and Mehdi,

thanx a lot for your response

cheerrsss

Anjali
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