Simulating the Behavior of Rotating Fluids: CFD vs ALE

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SUMMARY

This discussion focuses on simulating the behavior of rotating fluids, specifically comparing Computational Fluid Dynamics (CFD) and Arbitrary Lagrangian-Eulerian (ALE) methods. It highlights the complexities involved when a basin of fluid is rotated, emphasizing the interplay between gravitational and centrifugal forces, and how tilting the basin introduces torque that affects fluid equilibrium. The conversation underscores that the outcome depends significantly on whether the flow is turbulent or laminar, impacting the fluid's angular momentum and settling behavior.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with Computational Fluid Dynamics (CFD) software
  • Knowledge of Arbitrary Lagrangian-Eulerian (ALE) methods
  • Concepts of angular momentum and torque in fluid systems
NEXT STEPS
  • Research the differences between CFD and ALE simulation techniques
  • Explore software options for CFD simulations, such as ANSYS Fluent or OpenFOAM
  • Study the effects of turbulent versus laminar flow on fluid behavior
  • Investigate methods for applying torque in fluid simulations
USEFUL FOR

Fluid dynamics researchers, engineers working with rotating systems, and simulation specialists interested in advanced fluid behavior modeling.

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If I were to rotate a basin of fluid at a given angular speed, I would have two acceleration components.. one gravity and one centrifugal. What would happen if I added gravity to both components of acceleration (from tilting the basin). The fluid should move to one side correct? But, what if I just speed the basin up? Would the fluid even itself out at an equilibrium point?

Thanks!
 
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Two acceleration components on what? The fluid?

The fluid in this drum has a body force due to gravity and also shear forces from friction with the wall of the basin. The relative strength of these two forces will dictate how the fluid settles in equilibrium. When the basin is level and spinning, the fluid has some steady-state angular momentum. This angular momentum will be conserved in the fluid until some torque acts on it. When you tilt the basin you are applying a torque, but this is applied at the boundary of the fluid and not the whole fluid. The result is a big mess where the outer parts of the fluid continue to rotate with the tilted basin, but the inner parts rotate as they did before.

Basically it's a very complicated question, and even the qualitative answer depends on the details of the experiment (i.e. turbulent v laminar flow).
 
mikeph said:
Two acceleration components on what? The fluid?

The fluid in this drum has a body force due to gravity and also shear forces from friction with the wall of the basin. The relative strength of these two forces will dictate how the fluid settles in equilibrium. When the basin is level and spinning, the fluid has some steady-state angular momentum. This angular momentum will be conserved in the fluid until some torque acts on it. When you tilt the basin you are applying a torque, but this is applied at the boundary of the fluid and not the whole fluid. The result is a big mess where the outer parts of the fluid continue to rotate with the tilted basin, but the inner parts rotate as they did before.

Basically it's a very complicated question, and even the qualitative answer depends on the details of the experiment (i.e. turbulent v laminar flow).

Thank you mike.

Do you know of a good way to simulate this behavior (CFD versus ALE) [by chance]?
 

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