CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

A circular cylinder in simple shear flow

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 6, 2021, 00:15
Default A circular cylinder in simple shear flow
  #1
New Member
 
Abbas ali
Join Date: Oct 2021
Posts: 2
Rep Power: 0
Ali_abbas is on a distinguished road
The motion of circular cylinder with density ratio 10 (density of cylinder =10* density of fluid) free to rotate about centre axis placed at the centreline of the fluid field with the upper and lower walls moving in opposite directions at velocity Uw /2 was studied for a wide range of Reynolds numbers.
I want to find variation of angular speed ω for the confinement ratio of H/a=4, where G is the shear rate (2Uw/H), a is the radius of the cylinder and H is the channel height, with Re=Ga2/ν.




i tried this dynamic mesh .
but my cylinder is not rotating.
can someone help how should i proceed it. do i need to use the udf for this
Attached Files
File Type: pdf problem statement_compressed.pdf (52.4 KB, 11 views)
Ali_abbas is offline   Reply With Quote

Old   October 7, 2021, 03:52
Default
  #2
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,754
Rep Power: 66
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
I have no idea what you would even use a UDF for, so no =)


I don't follow what is this cylinder. Is it just a circular region of fluid with a different density? Then you don't need a dynamic mesh. You just need to specify the proper intitial conditions.

If it's a solid cylinder, then I don't get why the cylinder has a density. You still wouldn't need a dynamic mesh. But you could model this with slip walls with 0 stress and find the fluid velocity near the wall.
LuckyTran is offline   Reply With Quote

Old   October 19, 2021, 07:28
Default
  #3
New Member
 
Abbas ali
Join Date: Oct 2021
Posts: 2
Rep Power: 0
Ali_abbas is on a distinguished road
It is solid cylinder. I want to know the angular velocity with which solid cylinder will rotate.
I used periodic beoundary condition between inlet and exit but then cylinder do not rotate.
When i used same pressure at inlet and outlet still cylinder do not rotate.
Upper and bottom wall are moving in +x and -x respectively with some velocity.
Do you suggest any method/boundary conditions by which cylinder can rotate
Ali_abbas is offline   Reply With Quote

Old   October 19, 2021, 12:39
Default
  #4
Senior Member
 
Lorenzo Galieti
Join Date: Mar 2018
Posts: 375
Rep Power: 12
LoGaL is on a distinguished road
I think the domain looks something like this

—————————-> V_wall


Cylinder O


<————————— -V_wall


So the shear layer should indeed promote the rotation of the cylinder. The density of the cylinder then has some effect on the moment of inertia

Having said that, no clue on how to solve this with fluent
LoGaL is offline   Reply With Quote

Old   October 19, 2021, 13:21
Default
  #5
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,754
Rep Power: 66
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
I mean the way to model this would be to set the wall rotation speed for the cylinder. Link it to a parameter and iterate it until the integrated wall shear stress is zero (kind of like in the old days when we used to iterate the pressure until the target flow rate is achieved). It still doesn't involve a dynamic mesh & I'm still confused where the density/inertia of the cylinder comes in for a steady problem. With that said, maybe that info wasn't even relevant in the first place, except to say that the cylinder is solid.


Having also said that, what is even being done in this simulation that we have no details about that is supposedly not rotating? All we have is a problem statement.
LuckyTran is offline   Reply With Quote

Old   October 19, 2021, 13:40
Default
  #6
Senior Member
 
Lorenzo Galieti
Join Date: Mar 2018
Posts: 375
Rep Power: 12
LoGaL is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
It still doesn't involve a dynamic mesh & I'm still confused where the density/inertia of the cylinder comes in for a steady problem.
Well, I kind of assumed that he wants to do unsteady with the cylinder initially at rest. If he wants steady, then no clue, at the end of the day it is not my thesis :P
LoGaL is offline   Reply With Quote

Old   October 19, 2021, 17:30
Default
  #7
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,754
Rep Power: 66
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
If this is an unsteady problem I would expect to see something (anything) concerning initial conditions.
LuckyTran is offline   Reply With Quote

Reply

Tags
ansys, cylinder, fluent, shear, simple


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
2D flow around a circular cylinder case with interFoam solver shuoxue OpenFOAM Running, Solving & CFD 2 January 14, 2020 14:23
Discrepancy in the Strouhal number of a flow past circular cylinder HectorRedal Main CFD Forum 13 April 6, 2017 19:20
flow around a circular cylinder with velocity inlet and outflow outlet shuoxue OpenFOAM 1 March 3, 2014 11:42
flow around a circular cylinder with velocity inlet and outflow outlet shuoxue OpenFOAM Running, Solving & CFD 0 November 2, 2013 05:32
2D flow around a circular cylinder case with interFoam solver shuoxue OpenFOAM Running, Solving & CFD 0 August 31, 2013 06:04


All times are GMT -4. The time now is 13:58.