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October 15, 2009, 17:13 
Variable nondimensional CFX

#1 
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Juan Lorenzo
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I want to compare the results obtained in the CFX with another study but in this, they standardized the continuity and the NavierStokes equations it is possible to make nondiemnsional the equations in the CFX???
I understand that using one cell I can work the equations that I create I pleasure. what I want to know if the variables of the program (the continuity and the NavierStokes equations) can be standardized (nonadimensional) and since it becomes? if the answer is negative as I compare a study of simulation in CFX with another nondimensional? 

October 15, 2009, 18:41 

#2 
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Glenn Horrocks
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CFX is a dimensional solver. As long as you give it a consistent set of input units to work in then it is fine. You can define a unit system which is nondimensional if you like.
Obviously you can compare a dimensional and nondimensional solution. The nondimensional result can be made dimensional by assuming a length, time and any other necessary scales and scaling the results to give a dimensional result. Alternately you can nondimensionalise the CFX result. Either is fine. 

October 15, 2009, 22:18 

#3 
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Juan Lorenzo
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As I can nondimensionalise the cfx result? I must establish to unit nondimensional system which is before the simulation or after finished the simulation I can pass nondimensionale the result?


October 18, 2009, 07:07 

#4 
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Glenn Horrocks
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No, you can use the same nondimensional system (eg U*=U/Uref where U* is the non dimensional velocity, U is the dimensional velcoity and Uref is the reference velocity) used to define to define the nondimensional system in the first place to the CFX results.


October 18, 2009, 10:50 

#5  
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Juan Lorenzo
Join Date: Jul 2009
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thanks Glenn... understand.
Now, already like establishing my nondimensional system, but like I can cause that the CFX recognizes my nondimensional variables to me. I explain myself: Quote:
Velocity u (nondimensional) = Velocity u/Free Stream. Velocity u = Velocity that calculates the CFX Free Stream = Velocity of reference (I define) Q: Since I do so that the CFX works with my new variable (nondimensional Velocity or) instead of velocity u? reading HELP CFX consegui this: (Example) EXPRESSIONS: Re = 4.29E6 [] Bel = 60 [m s^1] L=1.044 [m] Visc=areaAve (density) @in*Vel*L/Re PROPERTIES: Option = Ideal Gas Molar Mass = 2.896E1 [kg kmol^1] Dynamic Viscosity = Visc Specific Heat Capacity = 1.E3 [J kg^1 K^1] Thermal Conductivity = 2.52E2 [W m^1 K^1] In theory it could make this but parameters like the Velocity u, v, w or distance x, y, z or density where not to look for them to change them by my expressions nondimensional. I would want to settle down this nondimensional system this way: Velocity u (nondimensional) = Velocity u/Free Stream. Velocity v (nondimensional) = Velocity v/Free Stream. Velocity w (nondimensional) = Velocity w/Free Stream. X (nondimensional) = X/Diam. Y (nondimensional) = Y/Diam. Z (nondimensional) = Z/Diam. t (nondimensional) = (t*Free Stream) /Diam. same question, since I do so that the CFX works with my new variables and not with which it has by defect? excuses by my English… are very bad 

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