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Old   December 21, 2009, 13:17
Default Momentum source definition
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Good afternoon everybody,
I'm trying to model a part of my mesh as a pressure loss by means of the usage of the equation of the loss itself.
At this purpose, I have defined a subdomain.
As subdomain has have defined exactly the model part I have to model a pressure drop.
The way I wish to use for this drop specification is the following one:
Dp = a*v^2
Dp is the pressure difference between the entry and the exit of my subdomain
a is a constant

I wish to define an expression of thje previous equation... but without success....

Then, I'm trying to define it as follow
I open "Edit Subdomain"
I enable "Sources"
I enable "Momentum Source/Porous Loss Model"
I enable "General Momentum Source" in order to setup the x component as Zero, the y component as zero and to consider for the z component, the expression I should have been already defined.

How can I do?

Thanks in advance for helping me
Best Regards
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Old   December 21, 2009, 18:31
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When using General Momentum Sources you have not to define the expression of the pressure losses , just indicate the value of the source in the Z direction if it is uniform in the domain else you should write the expression of the source versus Z (ex : S=aZ+b).
Now, if you are interested by using this expression Dp = -a*v^2 you must use Directional Loss Model with these settings:

Streamwise Direction > X Component
Streamwise Direction > Y Component
Streamwise Direction > Z Component
Streamwise Loss > Option
Linear and Quadratic Coefs
Streamwise Loss > Quadratic Resistance Coefficient
Streamwise Loss > Quadratic Resistance Coefficient > Quadratic Coefficient

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