Ansys - Boundary conditions for 2 cylinders and fluid

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Discussion Overview

The discussion revolves around the analysis of a rotating cylinder containing fluid, focusing on boundary conditions in Ansys for stress and structural analysis. Participants explore the complexities of modeling fluid dynamics, particularly the effects of sloshing and centripetal forces, as well as the challenges of applying appropriate boundary conditions in simulations.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses the intention to analyze a rotating cylinder that is half-filled with liquid and seeks to perform stress analysis.
  • Another participant warns that modeling the fluid's sloshing behavior will be significantly more complex than calculating stresses from centripetal acceleration alone.
  • A participant requests guidance on how to account for inertia loads in their analysis.
  • There is a suggestion to treat the fluid as a solid material to simplify the analysis, raising questions about how to apply boundary conditions in this scenario.
  • One participant proposes that using a linear dynamic solver could help determine mass and solve for centripetal acceleration and force, but doubts the validity of approximating the fluid as solid.
  • Another participant argues that treating the fluid as a solid is justified under high RPM conditions, noting that the fluid will pool in one half of the cylinder if gravity is neglected.
  • Concerns are raised about the complexity of the problem when considering both the rotation of the fluid and the cylinder about different axes.
  • A participant specifies the dimensions of the cylinder and the distance of the rotation axis from the cylinder, indicating a desire to evaluate structural stability under multiple loads.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of approximating the fluid as a solid and the complexity of modeling the system. There is no consensus on the best approach to apply boundary conditions or the overall methodology for the analysis.

Contextual Notes

Participants highlight the challenges of accurately modeling fluid dynamics, particularly in relation to sloshing and centripetal forces, and the implications of neglecting gravity in their calculations. The discussion reflects a range of assumptions and conditions that may affect the analysis.

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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
 
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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.
 


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


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.
 
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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 vertical 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!
 


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)?
 


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..
 

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