@ferret/physics-rotor

bladeCp function

function bladeCp(r: BladeRotor, rho: number, U: number, lambda: number): number

The power coefficient of a blade rotor at the tip-speed ratio λ in a wind U: what the lumped mode is fitted to.

packages/physics-rotor/src/loads.ts:108

bladeLoads function

function bladeLoads(r: BladeRotor, rho: number, U: number, omega: number): BladeLoads

Blade-element and momentum theory at one station of the blades: the flow U along the axis and the speed ω give the angle of attack; the lift and drag turn into the torque and the thrust; the induced flow (a, a′) from momentum theory is iterated with the tip loss, so the power can never pass the Betz limit. Positive torque turns the rotor the way ω does (a turbine); a propeller (pitched past the inflow angle) gives negative torque and negative thrust. For the thrust sign U is taken as its magnitude: the caller turns the force to the flow.

packages/physics-rotor/src/loads.ts:68

fitLumped function

function fitLumped(r: BladeRotor, rho = 1.225, U = 8): { cpMax: number; peak: number }

Fit the lumped curve (cpCurve: a parabola with its peak at peak, height cpMax) to the element model by sweeping the tip-speed ratio.

packages/physics-rotor/src/loads.ts:114

frameOf function

function frameOf(axis: Vec3, up: Vec3): { a: Vec3; u: Vec3; t: Vec3 }

The in-plane frame of a rotor: radial reference u, the direction t = a × u that a positive turn moves towards.

packages/physics-rotor/src/loads.ts:124

plateForce function

function plateForce(W: Vec3, n: Vec3, rho: number, A: number, polar?: Polar): Vec3

The force of a flat plate of area A and unit normal n in a flow W relative to it (the fluid's velocity minus the plate's): drag along W, lift across it on the side the plate is hit from. At right angles it is the drag of a plate facing the flow; edge-on it is skin friction only.

packages/physics-rotor/src/loads.ts:37

polarAt function

function polarAt(p: Polar | undefined, alpha: number): { cl: number; cd: number }

Lift and drag coefficients at the angle of attack α (rad, any value): attached up to the stall, then falling to zero lift at 90°; the plate is symmetric.

packages/physics-rotor/src/loads.ts:21

rotors function

function rotors(): RotorsCapability

packages/physics-rotor/src/index.ts:124

strokePose function

function strokePose(o: OarStroke, time: number): StrokePose

packages/physics-rotor/src/stroke.ts:40

validateRotor function

function validateRotor(d: unknown, path = 'rotor'): string[]

packages/physics-rotor/src/index.ts:81

windAvailable function

function windAvailable: (rho: number, radius: number, U: number) => number

Power available in the wind through the disc, W.

packages/physics-rotor/src/loads.ts:105

BladeLoads interface

interface BladeLoads

packages/physics-rotor/src/loads.ts:60

BladeRotor interface

interface BladeRotor

packages/physics-rotor/src/loads.ts:49

BladeSpec interface

interface BladeSpec

The blade kind of actuator: a plate in a medium. area, normal (the body's frame) and a polar; the force comes from the plate's velocity against the local flow. The profile drives the plate's stroke, not the force: stroke: { dir, speed } moves the plate relative to the body at speed × profile (an oar sweeping through the water), so the same stroke gives less against the current.

packages/physics-rotor/src/index.ts:374

OarStroke interface

interface OarStroke

The stroke of an oar: where the blade is, and how the plate faces, at a point of the cycle. The oar pivots at the oarlock (pivot, the body's frame); the blade is at the end of reach (from the pivot, at the middle of the sweep) turned about axis by an angle that goes arc[0] to arc[1] in the drive (a share drive of the cycle) and back in the recovery. In the recovery the blade is lifted out of the water along the axis by up to lift metres and the plate turns edge-on (feathered), so the same stroke pulls in the water and slips through the air. Immersion is not a number here: the force is read from the medium at the blade's place, so the lift decides it.

packages/physics-rotor/src/stroke.ts:10

Polar interface

interface Polar

Pure load models of the plan and the blade kind of 3.2: no host, no world, so they are tested against the analytic values and reused by the capability and by anything that wants the numbers (a tool, a game's own rotor).

packages/physics-rotor/src/loads.ts:7

RotorDef interface

interface RotorDef

packages/physics-rotor/src/index.ts:19

RotorsCapability interface

interface RotorsCapability extends Capability

packages/physics-rotor/src/index.ts:64

RotorState interface

interface RotorState

packages/physics-rotor/src/index.ts:54

StrokePose interface

interface StrokePose

packages/physics-rotor/src/stroke.ts:24

RotorElementKind type

type RotorElementKind = 'blade' | 'paddle' | 'bucket'

rotors. N blades, paddles or buckets around an axis, on a body or on a drivetrain shaft, summed into one torque (and a force) each step without a body per element:

  blade   blade-element and momentum theory in the local flow (windmill sails, wind turbine, propeller, fan), or a lumped curve fitted to it
  paddle  the drag of the immersed part of flat paddles in the local water (undershot wheel, paddle steamer)
  bucket  the weight of the water in buckets filled at one angle and emptied at another (overshot wheel)

Also here: the blade kind of actuator, a plate in a medium whose stroke is driven by the profile (an oar).

packages/physics-rotor/src/index.ts:18