Functions
	solver (ni, nr, ii, ir)

	builder_scene (**kw)

	raw_scene ()

	net_force (s, steps=300)

	check (cond, msg)

Variables
	N

	R

	MU

	DT

int	OMEGA = 1e-3

	KI_I

	KI_R

float	x0 = 0.5 * N + 0.3

tuple	CEN = (x0, x0, x0)

bool	ok = True

	s = solver(*builder_scene(ang_vel=[0, 0, OMEGA]))

	c = np.asarray(s.instance_center(0))

	ang_vel

	center

float	RP = 8.0

	F0 = net_force(s)

	Fp = net_force(s)

int	U = OMEGA * RP

	Ft = net_force(s)

	rel = np.linalg.norm(F0) / np.linalg.norm(Fp)

Detailed Description

Centre of rotation: NaN follows the body, any finite point pins -- the world origin included.

Semantics gated (§7 item 3):
  (a) builder default (NaN) -> centre = the translation, instance_center_pinned False;
  (b) builder center=(0,0,0) -> PINNED at the world origin (the case zero-as-unset made impossible);
  (c) raw array with zeros -> legacy 'follows the body' (every shipped page);
  (d) set_instance_motion(center=...) -> pinned, and it STAYS pinned when the body is moved by
      set_instance_transform (the old float comparison re-tracked it whenever the body passed
      through its own pin).
Physics gated: a sphere spinning about a point a distance R_p from its centre translates at
U = |w x R_p| at that instant, so its net reaction force must match the drag of the same sphere
towed at U through the same box (Stokes, advection off); a sphere spinning about its OWN centre
has no net force beyond the discretisation asymmetry of an off-lattice sphere (< 1% of the pivot force).

Usage: PYTHONPATH=<flow build>:<core geom build> python centre_of_rotation_gate.py

Function Documentation

◆ solver()

centre_of_rotation_gate.solver	(	ni,
		nr,
		ii,
		ir
	)

Definition at line 29 of file centre_of_rotation_gate.py.

◆ builder_scene()

centre_of_rotation_gate.builder_scene ( ** kw )

Definition at line 41 of file centre_of_rotation_gate.py.

◆ raw_scene()

centre_of_rotation_gate.raw_scene ( )

Definition at line 48 of file centre_of_rotation_gate.py.

◆ net_force()

centre_of_rotation_gate.net_force	(	s,
		steps = `300`
	)

Definition at line 57 of file centre_of_rotation_gate.py.

◆ check()

centre_of_rotation_gate.check	(	cond,
		msg
	)

Definition at line 65 of file centre_of_rotation_gate.py.

Variable Documentation

◆ N

centre_of_rotation_gate.N

Definition at line 21 of file centre_of_rotation_gate.py.

◆ R

centre_of_rotation_gate.R

Definition at line 21 of file centre_of_rotation_gate.py.

◆ MU

centre_of_rotation_gate.MU

Definition at line 22 of file centre_of_rotation_gate.py.

◆ DT

centre_of_rotation_gate.DT

Definition at line 22 of file centre_of_rotation_gate.py.

◆ OMEGA

int centre_of_rotation_gate.OMEGA = 1e-3

Definition at line 23 of file centre_of_rotation_gate.py.

◆ KI_I

centre_of_rotation_gate.KI_I

Definition at line 24 of file centre_of_rotation_gate.py.

◆ KI_R

centre_of_rotation_gate.KI_R

Definition at line 24 of file centre_of_rotation_gate.py.

◆ x0

float centre_of_rotation_gate.x0 = 0.5 * N + 0.3

Definition at line 25 of file centre_of_rotation_gate.py.

◆ CEN

tuple centre_of_rotation_gate.CEN = (x0, x0, x0)

Definition at line 26 of file centre_of_rotation_gate.py.

◆ ok

bool centre_of_rotation_gate.ok = True

Definition at line 64 of file centre_of_rotation_gate.py.

◆ s

centre_of_rotation_gate.s = solver(*builder_scene(ang_vel=[0, 0, OMEGA]))

Definition at line 71 of file centre_of_rotation_gate.py.

◆ c

centre_of_rotation_gate.c = np.asarray(s.instance_center(0))

Definition at line 72 of file centre_of_rotation_gate.py.

◆ ang_vel

centre_of_rotation_gate.ang_vel

Definition at line 80 of file centre_of_rotation_gate.py.

◆ center

centre_of_rotation_gate.center

Definition at line 85 of file centre_of_rotation_gate.py.

◆ RP

float centre_of_rotation_gate.RP = 8.0

Definition at line 91 of file centre_of_rotation_gate.py.

◆ F0

centre_of_rotation_gate.F0 = net_force(s)

Definition at line 93 of file centre_of_rotation_gate.py.

◆ Fp

centre_of_rotation_gate.Fp = net_force(s)

Definition at line 95 of file centre_of_rotation_gate.py.

◆ U

int centre_of_rotation_gate.U = OMEGA * RP

Definition at line 96 of file centre_of_rotation_gate.py.

◆ Ft

centre_of_rotation_gate.Ft = net_force(s)

Definition at line 98 of file centre_of_rotation_gate.py.

◆ rel

centre_of_rotation_gate.rel = np.linalg.norm(F0) / np.linalg.norm(Fp)

Definition at line 103 of file centre_of_rotation_gate.py.

Functions

Variables