Air resistance: cylindrical rotor in stator with air gap

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SUMMARY

The discussion focuses on the aerodynamic properties of a rotating cylinder acting as a rotor within a cylindrical housing, specifically analyzing the air gap of 0.5mm between the rotor and stator. The rotor, with a diameter of 150 mm, is expected to reach speeds of up to 25,000 rpm. Joep G.I. Taylor's research highlights the significance of Taylor vortices and the complexities of drag estimation due to the unstable nature of fluid flow in this configuration. Accurate predictions of aerodynamic losses necessitate empirical data tailored to the specific geometry and fluid dynamics involved.

PREREQUISITES
  • Understanding of fluid mechanics principles, particularly laminar and turbulent flow.
  • Familiarity with Taylor vortices and their impact on drag in rotating systems.
  • Knowledge of aerodynamic analysis techniques for rotating bodies.
  • Experience with empirical data collection and analysis in fluid dynamics.
NEXT STEPS
  • Research Taylor vortex formation and its implications on drag in rotating cylinders.
  • Explore empirical methods for measuring aerodynamic losses in electric motor configurations.
  • Study the effects of rotational speed on fluid behavior in confined spaces.
  • Investigate computational fluid dynamics (CFD) tools for simulating airflow in cylindrical geometries.
USEFUL FOR

Engineers, researchers, and students in the fields of fluid dynamics, mechanical engineering, and electric motor design will benefit from this discussion, particularly those focused on optimizing rotor-stator interactions and understanding aerodynamic losses.

Joep van de ven
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Hello,

I am currently doing research on the aerodynamic properties of a rotating cylinder in a cylindrical housing.
The cylinder represents a rotor in a electric motor. The air gap between rotor and stator is about 0.5mm.

I'm looking for a theoretical analysis and calculation on the aerodynamical losses in this setup. The rotor will reach speeds up to 25000 rpm

Approximated dimensions:

Rotor diameter: 150 mm
Stator internal diameter: 151 mm

Any help would be highly appreciated.

Kind regards,

Joep
 
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G.I. Taylor performed wide ranging and fundamental studies of this problem. While a fluid mechanics neophyte might be drawn to the laminar flow solution (which is trivial), the rotation of the inner surface leads to large centripetal accelerations of the inner layers of fluid, which unstably break away in structures called Taylor vortices (or taylor gortler structures). The drag is nothing I would care to estimate. In addition, of a myriad vortex structures which can semistably exist, there can be a switch between patterns leading to hysteresis in drag as a function of speed. So to be at all accurate, you really need empirical data relating to your specific geometry and fluid.
 
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I misspelled, that's Taylor Goertler
 

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