Help with torque calculation of underwater rotating disk?

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SUMMARY

The discussion focuses on calculating the torque required to rotate a 150mm diameter disk, 10mm thick, at a constant speed of 100rpm while submerged in water. The setup includes a circular ring with specific dimensions and weighs approximately 1kg. The participants emphasize the necessity of simulations to obtain accurate torque estimates due to the influence of the rotating disk on the water level. They suggest that while rough estimates can be made, precise calculations without simulation tools will be problematic.

PREREQUISITES
  • Understanding of torque calculations in fluid dynamics
  • Familiarity with simulation software for fluid dynamics
  • Knowledge of DC motor specifications and selection criteria
  • Basic principles of rotational motion and forces
NEXT STEPS
  • Research software packages for fluid dynamics simulations, such as ANSYS Fluent or COMSOL Multiphysics
  • Learn about torque calculation methods for submerged objects in fluids
  • Investigate DC motor specifications relevant to rotating systems
  • Explore the effects of water/air boundaries on submerged rotating bodies
USEFUL FOR

Mechanical engineers, fluid dynamics researchers, and hobbyists involved in designing rotating systems in aquatic environments will benefit from this discussion.

IamDev
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Hello Guys,

I have a disk of diameter of 150mm and thickness of 10mm which is rotating at the constant speed of 100rpm. The disk is inside water which is approximately 4-5 cm below the surface. Disk is horizontal (parallel to the water surface). Disk is attached with the shaft of the motor. At the upper surface of the disk there is a circular ring of outside diameter of 80mm and inside diameter of 70mm and height is 20mm.
I need to calculate the torque required to rotate this whole setup at 100rpm.
The weight of this setup is approximately about 1kg and the water is still at the surface.
 
In general, those things need simulations to get some numerical estimates. The water level will get influenced by the rotating disk, so you have to consider the water/air boundary as well. There are software packages that can model it, but expect some work to get the simulations running.
 
Is it possible to calculate required torque if we consider that water level will be constant during the whole process?
 
It is possible to get some estimates, but I think without a simulation all those estimates will be problematic.
 
Okay, I have a disk of 8 cm radius and 4 cm thickness and I have to rotate the disk at constant speed of 100 rpm. I need to buy a DC motor to rotate the disk but I am unable to short out the specification of DC motor. Can you help me please?
 
Well, it is possible to get some order of magnitude estimate. Do you have a sketch of the setup? How large is the water basin? What is below the disk?
 

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