where to define the prandtl number?

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 June 5, 2008, 22:56 where to define the prandtl number? #1 James Phone Guest   Posts: n/a Hi, everybody. I want to calculate thermal conductivity by using Prandtl number. But I am not sure where to define Pr. Only kinctic theroy option is present for the calculation of thermal conductivity. Give me a hand. Thanks.

 June 6, 2008, 05:29 Re: where to define the prandtl number? #2 Victor Guest   Posts: n/a Helo, You can't really define it in Fluent, it's a result of the configuration of your problem. Said you're looking for Pr = 100. c_p is specific heat of the fluid mi is the viscosity k the thermal conductivity. as you have, by the definition: Pr = c_p*mi/k You'll have just to set the proper c_p, mi and k to have 100 as a result for Pr. Like c_p = 1, mi = 100 and k = 1. But that is just too unreal as properties... I'd would take a real material - water, for example - and then adjust the properties slightly to approach the value of Pr you're looking for, like so you'll not have a fluid too away from reality. My best regards, Victor

 June 6, 2008, 08:56 Re: where to define the prandtl number? #3 Rakesh Jha Guest   Posts: n/a Engine oils can have Pr more than 100. Well said that the Pr is just a material properties nothing else. You can use the formula, Pr = (Dynamic viscosity * Specific heat capacity)/(Thermal conductivity). You can put the other three properties here and get thermal conductivity.

 June 6, 2008, 09:04 Re: where to define the prandtl number? #4 Rakesh Jha Guest   Posts: n/a You can put this formula in an user deined function and insert it Define -> Material -> User -Defined databse. go to drop down menu in thermal conductivity (where you saw the option kinetic theory) and opt for user defined. Hope this helps!

 June 12, 2008, 01:23 Re: where to define the prandtl number? #5 James Phone Guest   Posts: n/a Hi, I am modeling interface between two immiscible compressible fluids. But Fluent.Inc say only one compressible fluid can be defined when using its VOF slover. Then which code or software will meet my simulation?

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