Rotating flow

nasir.iitd · May 30, 2014, 03:02

I'm working with Ansys fluent 14.5(RANS-LES). My domain is a rotating cylinder and fluid flowing thru it. While setting cell zone shall I set frame motion with amount of angular rotation? Is wall motion is to be set? In setting inlet boundary shall I set axial, radial and tangential velocities values? There are two cases :1) Flow is entering the inlet of the domain at absolute velocity, 2)A rotating flow is entering the inlet of the domain. Is there anybody to help in these setting?
nasir.iitd

amin.z · May 31, 2014, 01:56

Quote:

Originally Posted by nasir.iitd

I'm working with Ansys fluent 14.5(RANS-LES). My domain is a rotating cylinder and fluid flowing thru it. While setting cell zone shall I set frame motion with amount of angular rotation? Is wall motion is to be set? In setting inlet boundary shall I set axial, radial and tangential velocities values? There are two cases :1) Flow is entering the inlet of the domain at absolute velocity, 2)A rotating flow is entering the inlet of the domain. Is there anybody to help in these setting?
nasir.iitd

Hello dear!
for frame motion you must define the rotation for the domains in cell zone! for rotary domains active frame motion and for stationary domain just define rotation axis!
then in the boundary condition for rotary wall select "stationary wall" and for non-rotary wall select "moving wall" & "absolute" then enter "0" for speed!

nasir.iitd · May 31, 2014, 05:43

Quote:

Originally Posted by amin.z

Hello dear!
for frame motion you must define the rotation for the domains in cell zone! for rotary domains active frame motion and for stationary domain just define rotation axis!
then in the boundary condition for rotary wall select "stationary wall" and for non-rotary wall select "moving wall" & "absolute" then enter "0" for speed!

Dear amin.z,
Thanks for the kind help. My complete domain is rotating. I've set the following BC.
In cell zone- Frame motion>amount of rotation in rad/s>specified rotational axis.
In velocity Inlet-Component>relative to cell zone>cylindrical coordinate>Axial velocity in m/s>Radial and tangential vel. set 0 m/s >angular vel.set 0 rad/s as frame motion is set.
In Outlet- Pressure outlet>gauge Pr. set 0 >normal to boundary>Radially equilibirium pr. distribution>back flow set to 0.
in wall>stationary wall (as the frame is rotating by default the is also rotating).
Is my settings o.k.? But KE decay profile, tangential vel.and radial vel. profiles are not as expected.
Need your further help please.

amin.z · June 1, 2014, 01:14

Quote:

Originally Posted by nasir.iitd

Dear amin.z,
Thanks for the kind help. My complete domain is rotating. I've set the following BC.
In cell zone- Frame motion>amount of rotation in rad/s>specified rotational axis.
In velocity Inlet-Component>relative to cell zone>cylindrical coordinate>Axial velocity in m/s>Radial and tangential vel. set 0 m/s >angular vel.set 0 rad/s as frame motion is set.
In Outlet- Pressure outlet>gauge Pr. set 0 >normal to boundary>Radially equilibirium pr. distribution>back flow set to 0.
in wall>stationary wall (as the frame is rotating by default the is also rotating).
Is my settings o.k.? But KE decay profile, tangential vel.and radial vel. profiles are not as expected.
Need your further help please.

Your boundary conditions appears to be true. But the velocity inlet! I can't fully understand your model and Maybe your problem is caused by the velocity inlet BC! can you explain more? or attach a snapshot or...?

nasir.iitd · June 1, 2014, 06:06

Dear Amin,
I'm attaching the snapshots of Velocity inlet and Pr. Outlet Bc for your understanding.
Nasiruddin.

Kokemoor · June 2, 2014, 12:22

As you have it set up, the flow enters with rotation. (It has no tangential velocity relative to the rotating cell zone.) If you mean for it to enter without rotation, you can change the Reference Fram field to Absolute in the velocity inlet specification.

nasir.iitd · June 2, 2014, 12:41

Thanks Kokemoor,
The cell zone is fluid and rotating.There could be two cases: 1)Fluid entering the inlet with rotation /swirl-It is required to set relative to cell zone in the reference frame field of velocity inlet specification and calculated value of tangential velocity is also to be set. 2)Fluid entering the inlet without rotation-In this case Reference frame field is to be changed to absolute. Am I correct?
Are the rest of BC settings O.K.? Is pr. at the outlet to be set?In my case y+ distance is 6.5 i.e. first grid point from wall lying in buffer layer and Re No. is above 50,000. Can LES run give reliable result?

May 30, 2014, 03:02	Rotating flow	#1
nasir.iitd Member SHEIKH NASIRUDDIN Join Date: Aug 2013 Location: DELHI Posts: 52 Rep Power: 12	I'm working with Ansys fluent 14.5(RANS-LES). My domain is a rotating cylinder and fluid flowing thru it. While setting cell zone shall I set frame motion with amount of angular rotation? Is wall motion is to be set? In setting inlet boundary shall I set axial, radial and tangential velocities values? There are two cases :1) Flow is entering the inlet of the domain at absolute velocity, 2)A rotating flow is entering the inlet of the domain. Is there anybody to help in these setting? nasir.iitd

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June 2, 2014, 12:22		#6
Kokemoor Senior Member Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 13	As you have it set up, the flow enters with rotation. (It has no tangential velocity relative to the rotating cell zone.) If you mean for it to enter without rotation, you can change the Reference Fram field to Absolute in the velocity inlet specification.

June 2, 2014, 12:41		#7
nasir.iitd Member SHEIKH NASIRUDDIN Join Date: Aug 2013 Location: DELHI Posts: 52 Rep Power: 12	Thanks Kokemoor, The cell zone is fluid and rotating.There could be two cases: 1)Fluid entering the inlet with rotation /swirl-It is required to set relative to cell zone in the reference frame field of velocity inlet specification and calculated value of tangential velocity is also to be set. 2)Fluid entering the inlet without rotation-In this case Reference frame field is to be changed to absolute. Am I correct? Are the rest of BC settings O.K.? Is pr. at the outlet to be set?In my case y+ distance is 6.5 i.e. first grid point from wall lying in buffer layer and Re No. is above 50,000. Can LES run give reliable result?