# Shaking a Can under changing gravity

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 April 22, 2005, 21:18 Shaking a Can under changing gravity #1 Optixxx Guest   Posts: n/a ************************************************** ** Hi Community I have a special problem and maybe someone might help me and(or) write me a UDF. I have a Can with fluid domain inside and further is heated up from outside in a process. Additional the Can is now shaked to increase heat transfer and "forced convection" Question: I have the acceleration function a= w^2*sin(w*t) w(omega)= 17.6 1/s f.e so under gravity-panel: y-direction a = 9.81 m/s^2 x-direction: a=17.6^2*sin(17.6*t) I found nothing in the input-box for ...(t), so for unsteady calculation a udf is needed. Can someone write that short case Found nothing in help or search.Would be happy abou any help Thy Optixxx

 April 24, 2005, 04:56 Re: Shaking a Can under changing gravity #2 Mehdi Ghoddosy Guest   Posts: n/a Dear kenischi: Have your read fluent tutorial no. 15 for using VOF model. It would ontain usefull information for your case. I can send you the case file if needed. regards

 April 24, 2005, 12:12 Re: Shaking a Can under changing gravity #3 Optixxx Guest   Posts: n/a ************************************************* Thx Medi for help Yes in case of domain splitting liquid/gas you are right, because the can has also a headspace of air which canīt be neglegted. So the VOF model is needed, additional the heat equation. But for moving walls you can only set constant velocity numbers and that isnīt the case. The can is shaked translational (like a piston over a crankshaft)with changing velocities and accerelation over time. So the wall is accerlerated and then liquid and gas too. Therefore iīm sure, this can only be done with an udf, that calculates acceleration every time step, because we have a(t)=....sin(wt). Btw w (omega) is the rotational velocity of the crankshaft. So i need the udf for wall acceleration in wall panel Has anyone some further ideas Thx anyway Optixxx

 April 26, 2005, 03:49 Re: Shaking a Can under changing gravity #4 edi ghirardi Guest   Posts: n/a You can effectively change the values of gravity components during flow time via an udf or a scheme file. I personally use the second choice. Let me know if you are interested in it. Advantages: you don't need to compile or interpret it. Disadvantage: you have to write an input file that fluent have to read any time step. Edi.

 April 27, 2005, 21:05 Re: Shaking a Can under changing gravity #5 Optixxx Guest   Posts: n/a ********************************* Thx Edi for your advice, but i donīt need changing accerleration or velocities in define/conditions, because only the Can get that, inside the Can Fluent calculates swapping over viscosity. The liquid isnīt affected. So i need the wall-panel. Also i can calculate changing velocities over time for the wall, but under moving wall i normally able to set constant speed Any hints how i can changing velosity, maybe UDF thx Optixxx

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