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-   -   3D Circular Cylinder..please help (http://www.cfd-online.com/Forums/fluent/37787-3d-circular-cylinder-please-help.html)

Endee September 4, 2005 12:36

3D Circular Cylinder..please help
 
I am trying to validate 3D LES results for flow over a 1-4 circular cylinder in Fluent. Problem is that for a known experimental data (e.g.,Re=1.5e5), How should I specify my Velocity Inlet conditions (and how to get corresponding numerical equivalence of above experimental data). I am drawing a circular domain of 30 times dia of cylinder. Re= (rho*Vel*Dia)/meu Now if i take the dimensional domain as 30 meters with dia of cylinder as 1 meter, Re is 1.5e5, rho is 1.225, and meu is 1.7894e-5......it gives the corresponding velocity from above formula as ... Vel=2.191/dia = 2.191 m/sec (isnt too less?) if i decrease my domain with dia as .001 m, the Vel=2.191/.001 which is very high... So which velocity should i take ? Is it must to go for non-dimensional? if yes then how in Fluent?


Masood September 4, 2005 14:57

Re: 3D Circular Cylinder..please help
 
hi calculate velocity in the scale u r working from the exprimental data. by using reynolds no(as reynolds no is same fr diffrent sizes not the velocity) . the compare the velocities calculated by FLUENT (as the model in fluent is in the scale u r working). did i made my point??.


Endee September 5, 2005 07:45

Re: 3D Circular Cylinder..please help
 
hi, Still problem is not clear....we cant implement the Re straight away... okay say in lab we used a cylinder of 1 inch (25.4 mm) at a Re of 1e5. in CFD what should be the corresponding inlet velocity? Do you mean there is no correction for experimental and numerical data? Comments plz?


Masood September 5, 2005 15:46

Re: 3D Circular Cylinder..please help
 
hi as i remeber in cylinder in cross flow Re = (vel * Dia.)/ kinematic viscosity

so u can get velocity from here and apply it as inlet condition of CFD problem.



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