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-   -   Solving in dimensionless form (http://www.cfd-online.com/Forums/phoenics/51496-solving-dimensionless-form.html)

ARAMESSH October 19, 2002 03:25

Solving in dimensionless form
 
Hi everybody, Is it possible solving of problems by PHOENICS in dimensionless form?

Rami October 20, 2002 04:12

Re: Solving in dimensionless form
 
Hi ARAMESSH,

"Is it possible solving of problems by PHOENICS in dimensionless form?"

Yes. Just non-dimensionalize everything consistently.

ARAMESSH October 20, 2002 13:44

Re: Solving in dimensionless form
 
Dear Rami , I wouid be grateful if you explain more. thanks a lot

Rami October 21, 2002 03:57

Re: Solving in dimensionless form
 
Hi ARAMESSH,

You should first put your equations in a nondimensional form. As a result you get the nondimensional groups (e.g., Reynolds, Mach etc.). You then input your problem to PHOENICS using these dimensionless parameters (e.g., if your reference length is the domain length in x-direction, then the corresponding input x-coordinate should be 1).

Having done so, your transport equations (e.g., mass, momentum, energy) should be put in a form consistent with the generic PHOENICS transport equation. You can then identify the source term and the exchange factors in your nondimensional set, and input the corresponding values (e.g., a nondimensional value of a volumetric heat source).

Consistency should be maintained throughout. For example, if you use perfect gas, and had selected the reference pressure and density, your reference temperature is consequently determined. Furthermore, the resulting equation of state in the nondimensional variables has the same form as the dimensional, with the gas constant equals 1. Since the specific heat ratio, gamma, is known (e.g. 1.4), then Cp is also determined to be gamma/(gamma-1) (i.e., equals 3.5 in the present example). Note also, that usually the reference pressure is also determined by the reference density and velocity.

I hope this helps to clarify my former posting.

Rami



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