# Rotating cylinder

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 December 5, 2004, 12:03 Rotating cylinder #1 Johnny Guest   Posts: n/a Hi, I am using flotran to simulate a 2-d model of a cylinder rotating in a flow field. With a fine mesh on the rotating cylinder in could take hours to input the VX and VY componants of each node, is there a simpler way or a macro that can input the values for me?? Any help is much appriciated..

 December 5, 2004, 16:53 Re: Rotating cylinder #2 Jim_Park Guest   Posts: n/a Are you actually doing Cartesian coordinates (x - y) or cylindrical (radial-angular)? Are you wanting to define velocity components as initial conditions for a transient or iterative solution? That is, every node on your mesh. Or are you defining velocities ot be used as boundary conditions on the boundary of your computational domain only? Is your problem specific to flotran and its input mechanism - or would you have the same problem if you were writing a fortran or c++ code to solve it?

 December 6, 2004, 05:01 Re: Rotating cylinder #3 Johnny Guest   Posts: n/a I can use either co-ordinate system although I believe cylindrical to be a better option. My domain is an annulus I want to define an x and y velocity componant for every node on the surface of the inner cirle. I believe if I use 360 nodes it will make the macro simpler.I have calculated the values of these componants for a speed of 100rpm and could input them individually,but this would take hours and would have to be repeated for any other speed i wish to investigate. This is specifically a flotran problem

 December 6, 2004, 11:46 Re: Rotating cylinder #4 Jim_Park Guest   Posts: n/a I don't know the nomenclature for flotran. If you're using cylindrical coordinates, I'd expect the velocities on the inner circle (the boundary conditions for that boundary) to be given as a radial and a cylindrical velocity component at each node node (not x and y components at each node). In fact, wouldn't the angular velocity on that boundary be the same at every node (the angular velocity in radians/sec x the radius of the inner boundary)? The radial velocity at the inner boundary might be a function of angle, depending on your particular problem. If it's stictly a flotran problem, this is as far as I can go. Surely they've made something like this easy?

 December 6, 2004, 12:44 Re: Rotating cylinder #5 Johnny Guest   Posts: n/a thanks for your help, but i dont think its possible to enter a velocity load in flotran as angular velocity. Another problem i have is finding lift and drag coefficents from the solution I think it has something to do with the pressure integral at the inner boundary?

 December 7, 2004, 10:55 Re: Rotating cylinder #6 MLD Guest   Posts: n/a You can try using FlexPDE. Free student copies available. www.pdesolutions.com

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