[Aarthy Meena]

Hello,

I am Aarthy. Am a beginner to CFD and FLUENT.

I tried to simulate a 3D flow and heat transfer over a circular cylinder. But, I am getting very high drag coefficients. Kindly please help me resolve this. I tried using reynolds number 10.

Thank you.

[supersweet]

What does your fluid domain look like?

[Aarthy Meena]

Originally Posted by supersweet

What does your fluid domain look like?

Dear Super Sweet

I am simulating steady laminar 3D flow around a circular cylinder.

Diameter of cylinder (D) is 1.
Upstream length is 30D
Downstream length is 50D
Height above the cylinder is 30D
Gap below the cylinder is 30D
Boundary in Z direction are 30D away from the cylinder in positive direction.
Length of the cylinder is 30D in Z direction.
Working fluid is air.
Constant wall temperature boundary condition on the cylinder wall.
Top and bottom wall with slip condition (Shear stresses = 0) with ambient temperature.
Left side wall is taken as symmetry.
Right side wall with slip condition (Shear stresses = 0) with ambient temperature.

These are the details. Please share me your email ID. I will share my case and data files.

I am completely newbie to FLUENT. I can validate the drag and mean Nusselt number using a 2D flow. But I am getting very high drag coefficients in 3D flow.

I created mesh using ICEM CFD.

Thank you so much for trying to help me.


Right

[supersweet]

Thank you. And what are your boundary conditions?

[Aarthy Meena]

Originally Posted by supersweet

Thank you. And what are your boundary conditions?

Velocity inlet and pressure outlet. Inlet and outlet temperature is 300K.
Top and bottom walls are slip walls (Shear stress = 0), maintained at Constant temperature 300K.

One side wall is symmetry and the other side wall is slip wall(Shear stress = 0).

Cylinder is maintained at constant temperature = 350K.


These are my boundary conditions.

[supersweet]

Thanks. I am trying to recreate your simulation in my solver of choice. But, to fully do that I need to know what is your velocity inlet and pressure outlet. Also are your units in meter?

[Aarthy Meena]

Yes my units are in meter.

[supersweet]

And is your velocity at the inlet something like 0.0005 m/s assuming I did the Re=10 calculation correctly.

[Aarthy Meena]

It is 0.000146097m/S

[supersweet]

Thank you.

Ok,

For the face area I have an area of 0.785073 m^2
A force in the flow direction on this face of 1.85388 X 10^-8 N
A fluid density (@ T = 300 K) of 1.185
A Reynolds number of 277 (according to the scale information in the output file)

So, the Cd = (2*1.85388 X 10^-8 N)/(1.185*0.000146097^2*0.785073) = 1.867

This number is very close to the Cd provided on the graph at the Reynolds number.

I hope I have modeled your problem correctly and hope this helps you spot your problem. I may have not positioned the cylinder correctly in the direction of flow. Please check over everything and tell me what you think. Thanks.

[supersweet]

Looks like I modeled your problem the opposite way. Sorry, but I think this can still be useful to setup your problem correctly. Btw, do you have ANSYS CFX? I find it much more convenient to use.

[siancfd]

If you are getting good result in 2d and not getting the same in 3d, first you check your mesh and its quality.

with respect to your velocity try get get the appropriate y+.

for more information contact :
dimensiondesignanalysis@gmail.com

[Aarthy Meena]

Thank You Super sweet. I am trying to do it. I will write to you once I accomplish it. Thank you so much.