Rotary Eddy-Current Disc Brake: Torque vs RPM

This simulation models a rotary eddy-current (Foucault) disc brake — the contactless braking principle used in dynamometers and rotary brakes, distinct from a linear rail brake because every point of the spinning disc under the fixed magnet pole travels at a different linear speed. Braking torque is computed by numerically integrating a local force-velocity stress function, v(r) = ω·r, across the radius the pole footprint covers (Simpson's rule over 40 radial slices), rather than plugging a single velocity into one formula. Switch between copper, aluminum and steel discs, and adjust flux density and air gap, to see how each reshapes the torque curve and the spin-down time.