# Ansys - Boundary conditions for 2 cylinders and fluid

1. Feb 27, 2012

### nitinigam

ansys -- Boundary conditions for 2 cylinders and fluid

i want to do a analysis in ansys in which a cylinder will rotate about a axis which is out side of the cylinder and this cylinder is also rotating about its own axis. cylinder is half filled with liduid. i want to do the stress analysis or in more general structural analysis of cylinder

2. Feb 27, 2012

### Mech_Engineer

Re: ansys

I'm thinking the modeling of the fluid "sloshing" in the cylinder will be far more challenging than you realize. Calculating stresses based on cetripetal acceleration is relatively straightforward; calculating the net force (and stress) from a sloshing fluid will be a nightmare.

3. Feb 27, 2012

### nitinigam

Re: ansys

ok...thanks for the reply............can you suggest how i can proceed..what is the procedure to account for inertia load..

Last edited by a moderator: Feb 29, 2012
4. Feb 28, 2012

### nitinigam

Re: ansys

or suppose, i have made fluid part in this analysis as solid material then i rotate cylinder, and this fluid part simulteniously...to account for centriptal force........but how i will apply boundry condition.thats the problem.

5. Feb 29, 2012

### Mech_Engineer

Re: ansys

The problem would have to be solved in a linear dynamic solver where the mass is simply determined, and the solver solves for the centripetal acceleration and force. Still, I don't think approximating the fluid as a solid will be a very good one.

Last edited: Feb 29, 2012
6. Feb 29, 2012

### nitinigam

Re: ansys -- Boundary conditions for 2 cylinders and fluid

i think treating fluid as solid mass is quit justified as the fluid and cylindr is going to rotate about some other axis with very high RPM...all fluid will come in one half of the cylinder..if we neglect gravity...i have calculated that the fluid will make only 3degree of angle with verticle i mean if we take account for gravity...

can any1 suggest how to rotate a body with axix not passing through it............if i get this ans. i will be able to solve it....whole problem!

7. Feb 29, 2012

### Mech_Engineer

Re: ansys -- Boundary conditions for 2 cylinders and fluid

I'm having trouble visualizing what you're describing, but if what you're saying is the cylinder which has the fluid inside will be rotating about a remote point outside of the cylinder, then as long as the centripetal acceleration is significantly larger than gravity you're probably right that the fluid will all pool in one half of the cylinder. BUT, if the cylinder containing fluid is also rotating about its own axis, the problem gets about 1000 times harder.

So- where is your rotation axis (axes)?

8. Mar 1, 2012

### nitinigam

Re: ansys -- Boundary conditions for 2 cylinders and fluid

cylinder radius is arround 200 mm and this is to be rotated arround an axis which is half meter aways from axis of cylinder.........actualy i want to look structural stability of the cylinder when 3 loads 1st gravity, 2nd rotation of fluid which i will assume to be solid in cylinder 3rd when cylinder and fluid both will rotate about axis away from cylinder.............to approximately check weather it is going to yield or not..