Persian Panemone Windmill Simulator

Panemone Windmill

Wind speed 9 m/s

Wall shielding 75%

Load resistance 50%

Blade count 6

Rotor speed

–

Net torque

–

Shaft power

–

Grinding rate

–

⚠ Stalled — load resistance exceeds the wall's net drag torque at this wind speed.

How it works

A panemone is a vertical-axis drag-type windmill: paddle blades ring a vertical shaft, and a stone or reed wall wraps around one half of the rotor, leaving a gap on the windward side. Wind pushes hard on blades exposed through the gap but is blocked from reaching the blades on the sheltered side, so the two halves feel unequal drag and the shaft turns — no gears, no yaw mechanism, no need to face the rotor into the wind at all.

F(θ) = ½·ρ·Cd·A·v² · (1 − shield · visible(θ))
τ_net = Σ F(θᵢ)·r − τ_load
ω(t+dt) = ω(t) + (τ_net / I)·dt

Wind speed — raises drag force on every exposed blade quadratically; doubling wind speed roughly quadruples available torque.
Wall shielding — how completely the wall cancels drag on the return-side blades; a poorly built wall (low %) lets wind push back on both sides and the rotor stalls even in a gale.
Load resistance — the grinding or pumping work the shaft must fight; too much load for the available torque stalls the rotor entirely.
Blade count — more blades catch more wind per revolution but each is thinner in this model, so torque scales sub-linearly while drag losses rise — there is a sweet spot, not a monotonic gain.

Real-world relevance: this exact asymmetric-shielding trick — 4th–7th century Sistan, Iran — let millers grind grain and lift irrigation water directly off a vertical shaft for over a thousand years, without the carpentry needed to turn a horizontal-axis mill into the wind.

Exposed blade (driving) Shielded blade Wind flow

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