# Air resistance: cylindrical rotor in stator with air gap

• Joep van de ven
In summary, the conversation discusses the research being conducted on the aerodynamic properties of a rotating cylinder in a cylindrical housing, specifically in an electric motor. The desired outcome is a theoretical analysis and calculation of aerodynamic losses in this setup, where the rotor can reach speeds of up to 25000 rpm. Approximate dimensions of the rotor and stator are also provided. The mention of previous studies by G.I. Taylor reveals the complexity of the problem, as the rotation of the inner surface leads to unstable Taylor vortices and other vortex structures, making it difficult to estimate the drag without empirical data.
Joep van de ven
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

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.

Joep van de ven
I misspelled, that's Taylor Goertler

## 1. What is air resistance and how does it affect a cylindrical rotor in a stator with an air gap?

Air resistance, also known as drag, is a force that opposes the motion of an object through air. In the case of a cylindrical rotor in a stator with an air gap, air resistance can slow down the rotation of the rotor and decrease its efficiency.

## 2. How is air resistance calculated for a cylindrical rotor in a stator with an air gap?

The calculation of air resistance for a cylindrical rotor in a stator with an air gap involves factors such as the shape and size of the rotor, the air density, and the velocity of the rotor. It can be calculated using mathematical equations such as the drag equation or by conducting experiments.

## 3. What factors can affect the amount of air resistance experienced by a cylindrical rotor in a stator with an air gap?

The amount of air resistance experienced by a cylindrical rotor in a stator with an air gap can be affected by various factors such as the speed of the rotor, the shape and size of the rotor, the air density, and the surface roughness of the rotor and stator.

## 4. How can air resistance be minimized for a cylindrical rotor in a stator with an air gap?

To minimize air resistance for a cylindrical rotor in a stator with an air gap, the design of the rotor and stator can be optimized to reduce the drag force. This can include streamlining the shape of the rotor, reducing the air gap, and using materials with low surface roughness.

## 5. What are some real-world applications of understanding air resistance in a cylindrical rotor in a stator with an air gap?

Understanding air resistance in a cylindrical rotor in a stator with an air gap is crucial in the design and operation of various machines, such as electric motors, generators, and turbines. It is also important in the design of vehicles, aircraft, and wind turbines, where minimizing air resistance can increase efficiency and performance.