CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

modification for rotating cylinder simulation

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   July 18, 2006, 06:03
Default modification for rotating cylinder simulation
Posts: n/a

i've run a 2d flow past a circular cylinder and the drag/recirculation values are quite good.

i tried to modify it to simulate a rotating/spinning cylinder. i believe i only need to change the boundary velocity and nothing else. is that so?

i tried to run the simulation for different angular velocities at Re=20. the velocity vector plots seem correct compaared to the published one. cd & the viscous lift force are quite good. however, the lift force due to pressure is always about 55-65% of the correct results.

i wonder what's wrong. Did i miss out something? is there any modification required at the post processing stage?

tks in advance
  Reply With Quote

Old   July 19, 2006, 12:01
Default Re: modification for rotating cylinder simulation
Posts: n/a
compare the pressure distribution on the surface with published data. also check on the locations of stagnation point and separation point.
  Reply With Quote

Old   July 21, 2006, 07:52
Default Re: modification for rotating cylinder simulation
Posts: n/a
If you want to perform a moving grid simulation first you have to decide what is the system of reference in which you are resolving the governing equations: 1) if you choose the absolute frame of reference you have to rotate the grid at each time step ----> moving grids (computationally expensive but simple to implement)

2) if you choose the relative frame of reference you have to introduce a grid velocity (which affects the convective fluxes) a source term which contains the centrifugal effects and a projection of the far-field conditions on the relative frame of reference (much more difficult to implement but more efficient).

I think you are missing something if you only "changed the boundary velocities".....

  Reply With Quote

Old   July 21, 2006, 14:24
Default Re: modification for rotating cylinder simulation
Posts: n/a
don't get confused by mar's comments, zonexo. your method is valid and the only reasonable thing to do for your case.

Mar, you're missing the fact that this case of structural motion is very simple, almost trivial: the cylinder is rotating about it's own center axis, such that the wall surface is displaced onto itself. It makes no sense to rotate or even deform the grid, since there's no change in the shape or position of the cylinder. Likewise, it would make no sense to use anything else than the absolute coordinate system. What doesn't work for the general motion or deformation is perfectly fine for this special case: All you need to do is to assign the appropriate boundary velocities, i.e. the vector product btw omega and radius, on the cylinder surface.
  Reply With Quote


Thread Tools
Display Modes

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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
flow over a cylinder urgent! kevin FLUENT 8 August 11, 2015 13:00
Boundary Conditions. Simulation cylinder. davidmd OpenFOAM Running, Solving & CFD 25 October 7, 2010 06:10
Turbulent steady flow around a circular cylinder Mirek Kabacinski FLUENT 0 July 23, 2003 18:40
3-D Contaminant Dispersal Simulation Apple L S Chan Main CFD Forum 1 December 23, 1998 11:06
Simulation of the Flow past a circular cylinder using STAR-CD M. S. GUEROUACHE Main CFD Forum 0 October 1, 1998 10:51

All times are GMT -4. The time now is 23:10.