# translational periodicity - help!

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 February 20, 2012, 08:04 translational periodicity - help! #1 New Member   Alessandro Leonardi Join Date: Dec 2011 Posts: 2 Rep Power: 0 Sponsored Links Hi everybody! this is the first time I write in this forum, but I've been reading it for a while and I've always found very useful tips in it. For my thesis I'm trying to simulate the passage of a truck under an obstacle, so I split the mesh into two parts, a stationary top and a sliding part underneath, I made outlet and inlet periodic and I set the interface between the two parts as "periodic repeats" according to the scheme stator-rotor.The model is 2d and the turbulence model is Spalart-Allmaras. I would like to simulate the passage of the truck several times under the same obstacle, but when it gets to the left limit and reappears on the right, the solver does not converge and the results from this point have no meaning, since I see extremely high values of pressure and velocity. I don't know if I'm missing something or if I set the problem in the wrong way. I would be very grateful if you could help me! alex.leo stage_0.JPG stage_1.JPG stage_2.JPG

 February 21, 2012, 01:38 #2 Senior Member   Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 231 Rep Power: 11 Hi Alex, I want to know that why do you want to simulate truck again and again. Periodic does not make any sense. You could rather study a STEADY flow. As far as obstacle is concerned and if it is moving then you can use dynamic mesh option. A much easier (but a little tiring) approach would be to make 6 to 7 mesh each time making the obstacle at a new position. Run the cases on each mesh and see the results. Periodic will not work, you may specify velocity inlet and pressure outlet left and right respectively and symmetry on top and bottom surfaces.

 February 21, 2012, 06:18 #3 New Member   Alessandro Leonardi Join Date: Dec 2011 Posts: 2 Rep Power: 0 Hi Shamoon Jamshed, thank you for your answer! I want to simulate multiple trucks because I want to simulate the passage of a very long line of trucks under an obstacle. That's the reason why I wanted to use periodicity with a moving mesh for the truck, it seemed to me an efficient way to do this. If you confirm to me that periodic repeats will not work as I supposed then I will try another option.

 February 21, 2012, 09:26 #4 Senior Member   Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 231 Rep Power: 11 In that case you need to model only two trucks and take periodic on left and right boundaries.

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