CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

Shaking a Can under changing gravity

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

LinkBack Thread Tools Display Modes
Old   April 22, 2005, 21:18
Default Shaking a Can under changing gravity
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
  Reply With Quote

Old   April 24, 2005, 04:56
Default Re: Shaking a Can under changing gravity
Mehdi Ghoddosy
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
  Reply With Quote

Old   April 24, 2005, 12:12
Default Re: Shaking a Can under changing gravity
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

  Reply With Quote

Old   April 26, 2005, 03:49
Default Re: Shaking a Can under changing gravity
edi ghirardi
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.

  Reply With Quote

Old   April 27, 2005, 21:05
Default Re: Shaking a Can under changing gravity
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
  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
How to simulate spatial changing gravity force lakeat OpenFOAM Running, Solving & CFD 0 June 8, 2011 15:46
how to consider gravity in CFX shrimp CFX 4 September 8, 2008 20:41
changing gravity vector direction using UDF Nico FLUENT 0 September 7, 2006 12:00
variation of gravity with time rajani FLUENT 0 February 16, 2005 03:45
On gravity modelling... Drona CFX 7 November 22, 2001 11:28

All times are GMT -4. The time now is 14:41.