Regarding tranport values in lid driven cavity

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##### Question

Good morning sir,

Recently i started using openfoam, i have watched lid driven cavity simulation problem, for the same problem i changed time step to 2000 and higher values, still it is not convergent. Also i changed the methods,schemes and increased my mesh up to 100 but it is not convergent!

1) for which time step, the tutorial is convergent ?

2) what is the fluid used in that problem ? How can it be 0.01? How to take the value of kinematic viscosity ?

3) your case is Re = 10, suppose for Re = 100, how to take d,V and viscosity for the fluid air i need ?

i did like this , d=0.1m, v=1, accordingly viscosity =0.001?

my doubt is viscosity cannot be constant in case of air, for different temperatures different viscosities? please tell me how to take viscosity? Is my approach is correct?

4) Finally please tell me how to d,v and kinematic viscosity values ? For what time step and values it is convergent.

Thank you.

Recently i started using openfoam, i have watched lid driven cavity simulation problem, for the same problem i changed time step to 2000 and higher values, still it is not convergent. Also i changed the methods,schemes and increased my mesh up to 100 but it is not convergent!

1) for which time step, the tutorial is convergent ?

2) what is the fluid used in that problem ? How can it be 0.01? How to take the value of kinematic viscosity ?

3) your case is Re = 10, suppose for Re = 100, how to take d,V and viscosity for the fluid air i need ?

i did like this , d=0.1m, v=1, accordingly viscosity =0.001?

my doubt is viscosity cannot be constant in case of air, for different temperatures different viscosities? please tell me how to take viscosity? Is my approach is correct?

4) Finally please tell me how to d,v and kinematic viscosity values ? For what time step and values it is convergent.

Thank you.

OpenFOAM Simulating-flow-in-a-Lid-Driven-Cavity 10-11 min 30-40 sec

__Answers:__

Hi Nathan,

1. Since icoFoam is a transient solver the solver will keeps running. You have to check the residual values. If it reaches say 10^-5 you can stop the iterations manually. The solver won't stop and report solution is converged unlike the steady state solver. Probably you can try use residual plot to have a clear view of the residues with number of iterations.

2. The kinematic viscosity has been fixed based on Reynold's number and not on thermodynamic property of the fluid. Re = (velocity*characteristic length)/(Kinematic viscosity). Re = 10. V= 1 m/s and d = 0.1 m. Which gives the kinematic viscosity to be 0.01.

3. Since we are calculating property based on Reynold's number the viscosity is independent of thermodynamic property of the fluid used.

Regards,

Sathish

1. Since icoFoam is a transient solver the solver will keeps running. You have to check the residual values. If it reaches say 10^-5 you can stop the iterations manually. The solver won't stop and report solution is converged unlike the steady state solver. Probably you can try use residual plot to have a clear view of the residues with number of iterations.

2. The kinematic viscosity has been fixed based on Reynold's number and not on thermodynamic property of the fluid. Re = (velocity*characteristic length)/(Kinematic viscosity). Re = 10. V= 1 m/s and d = 0.1 m. Which gives the kinematic viscosity to be 0.01.

3. Since we are calculating property based on Reynold's number the viscosity is independent of thermodynamic property of the fluid used.

Regards,

Sathish

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