Fluent + flow past cylinder at Re=40

m.vegad · April 12, 2013, 05:49

I am extending study of flow over circular cylinder for Re=40, considering heat transfer along with fluid flow.

I am solving non dimensional form of steady, 2-D energy equation with constant fluid property and no heat generation, along with the mass and momentum conservation in 2-D

The boundary condition that i have specified is:

Cylinder: Wall at constant temperature at value of 1.0
Inlet: Constant velocity at constant temperature at value of 0.0
exit: outlet
Top and bottom horizontal surface: wall, adiabatic

I have not switched on the gravity.... (am no considering natural convection)

The trouble is that when i run the simulation .... it gives a message:

Value of temperature limited to 1.0 in the fluid zone!!!
The residual curve for energy equation is flat!

Can someone help what this is??

Far · April 13, 2013, 06:50

Do you have some particular experimental setup in your mind? How do you specify boundary conditions and what parameters you are trying to match?

m.vegad · April 14, 2013, 17:12

I am actually trying to ultimately solve flow of fluid around a heated cylinder...

The problem is that when i try and simulate for non dimensional equations using Fluent for the following parameters:

Pr=5.6, Re=10, Gr=0

there is problem when i initialize the solution...the message that i get is...

Temperature limited to 1.0 in fluid zone!!!

However when i use the DIMENSIONAL values of density, viscosity, specific heat and thermal conductivity along with the diameter value and input velocity (for Re=10) then i get the solution!!

Can you help and tell where the problem is???

Far · April 18, 2013, 07:42

any update?

m.vegad · April 22, 2013, 00:38

Actually when i am solving for NON DIMENSIONAL form of governing equation.... the way i have defined non dim temperature... the value is ZERO at the inlet....

Fluent has something that they call as FLOOR and CEILING values set for the parameter... its there in SOLVE menu....

One has to set the FLOOR value to zero.... (DEFAULT is one)... then things work out.

alimea · January 9, 2018, 01:34

Hi all
I want to solve the flow around the cylinder in viscoelastic fluid. At first I did it for Newtonian fluid in Re= 10 , 40 , 100 and for viscoelastic fluid in Re= 10 , 100 and obtained exact results. But when I change the Re to 40 for viscoelastic fluid, it became diverged!
I changed many parameters of solution:
urf = from 0.1 to 0.9 --> diverged!
corunt Nu. = from 0.1 to 0.9 --> diverged!
changing the kind and size of mesh --> diverged!
changing the kind and size of mesh --> diverged!
increasing the number of solving pressure correction Eqn from 2 to 20 --> diverged!
decreasing the min residuals to 1e-8 --> diverged!
changing discretization schemes of div terms: Gauss linear (central), Gauss upwind(1st), Gauss upwind(2nd), limitedLinear , QUICK --> diverged!

But I have done some ways to solve that:
1- I saw in this page that sb proposed to the other that decrease the residuals to 1e-19 !! I did it and my solution became converged! I can't analyze that! Is it possible?
2- In the other way I increased the number of solving pressure correction Eqn to 20, decreasing the min residuals to 1e-8
3- setting the time step to 0.001 instead of setting Cr=0.3

Now I don't know that my results are reliable or not!
Could you please tell me what happend that these solutions are appropriate for solve it?

Thanks

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April 12, 2013, 05:49		#21
m.vegad New Member Mitesh Vegad Join Date: Apr 2013 Posts: 18 Rep Power: 13	I am extending study of flow over circular cylinder for Re=40, considering heat transfer along with fluid flow. I am solving non dimensional form of steady, 2-D energy equation with constant fluid property and no heat generation, along with the mass and momentum conservation in 2-D The boundary condition that i have specified is: Cylinder: Wall at constant temperature at value of 1.0 Inlet: Constant velocity at constant temperature at value of 0.0 exit: outlet Top and bottom horizontal surface: wall, adiabatic I have not switched on the gravity.... (am no considering natural convection) The trouble is that when i run the simulation .... it gives a message: Value of temperature limited to 1.0 in the fluid zone!!! The residual curve for energy equation is flat! Can someone help what this is??

April 13, 2013, 06:50		#22
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Do you have some particular experimental setup in your mind? How do you specify boundary conditions and what parameters you are trying to match?

April 14, 2013, 17:12		#23
m.vegad New Member Mitesh Vegad Join Date: Apr 2013 Posts: 18 Rep Power: 13	I am actually trying to ultimately solve flow of fluid around a heated cylinder... The problem is that when i try and simulate for non dimensional equations using Fluent for the following parameters: Pr=5.6, Re=10, Gr=0 there is problem when i initialize the solution...the message that i get is... Temperature limited to 1.0 in fluid zone!!! However when i use the DIMENSIONAL values of density, viscosity, specific heat and thermal conductivity along with the diameter value and input velocity (for Re=10) then i get the solution!! Can you help and tell where the problem is???

April 18, 2013, 07:42		#24
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	any update?

April 22, 2013, 00:38		#25
m.vegad New Member Mitesh Vegad Join Date: Apr 2013 Posts: 18 Rep Power: 13	Actually when i am solving for NON DIMENSIONAL form of governing equation.... the way i have defined non dim temperature... the value is ZERO at the inlet.... Fluent has something that they call as FLOOR and CEILING values set for the parameter... its there in SOLVE menu.... One has to set the FLOOR value to zero.... (DEFAULT is one)... then things work out.

January 9, 2018, 01:34		#26
alimea Senior Member A. Min Join Date: Mar 2015 Posts: 308 Rep Power: 12	Hi all I want to solve the flow around the cylinder in viscoelastic fluid. At first I did it for Newtonian fluid in Re= 10 , 40 , 100 and for viscoelastic fluid in Re= 10 , 100 and obtained exact results. But when I change the Re to 40 for viscoelastic fluid, it became diverged! I changed many parameters of solution: urf = from 0.1 to 0.9 --> diverged! corunt Nu. = from 0.1 to 0.9 --> diverged! changing the kind and size of mesh --> diverged! changing the kind and size of mesh --> diverged! increasing the number of solving pressure correction Eqn from 2 to 20 --> diverged! decreasing the min residuals to 1e-8 --> diverged! changing discretization schemes of div terms: Gauss linear (central), Gauss upwind(1st), Gauss upwind(2nd), limitedLinear , QUICK --> diverged! But I have done some ways to solve that: 1- I saw in this page that sb proposed to the other that decrease the residuals to 1e-19 !! I did it and my solution became converged! I can't analyze that! Is it possible? 2- In the other way I increased the number of solving pressure correction Eqn to 20, decreasing the min residuals to 1e-8 3- setting the time step to 0.001 instead of setting Cr=0.3 Now I don't know that my results are reliable or not! Could you please tell me what happend that these solutions are appropriate for solve it? Thanks