elements.catalog.sudden_contraction

elements.catalog.sudden_contraction(cc=0.62, name='contraction', eps=None)

Sudden contraction that resolves the vena-contracta state (composite).

A flow contracting into a smaller pipe necks to a vena contracta of area cc * A2 just past the contraction plane, where the static pressure is at its minimum, then re-expands (with mixing loss) to fill the downstream pipe. The downstream area A2 is read off the attached outflow edge at build time (areas live on edges, never on elements). This composite resolves the neck explicitly – an :func:isentropic_area_change from the upstream area to the vena contracta, then a :func:sudden_area_change (Borda-Carnot) re-expansion to the downstream area – so the total-pressure loss and the minimum static pressure are exact at higher Mach.

This is the compressible upgrade to :func:sudden_area_change’s cc-loss, whose incompressible 1/2 rho u^2 head is accurate only to O(M^2). Read the vena-contracta state off the composite’s throat edge (solution.composite(name).throat_state).

Parameters

Name	Type	Description	Default
cc	float	Vena-contracta contraction coefficient in (0, 1] (default 0.62, a sharp-edged contraction; cc = 1 is the loss-free limit).	0.62
name	str	Display name.	'contraction'
eps	float	Sharpens the embedded Borda re-expansion switch (see :func:sudden_area_change).	None

Returns

Name	Type	Description
	CompositeElementSpec