elements.catalog.sudden_area_change

elements.catalog.sudden_area_change(
    name='sac',
    cc=1.0,
    eps=None,
    l_up=0.0,
    l_down=0.0,
    end_correction=0.0,
)

Sudden area change: Borda-Carnot expansion, vena-contracta contraction.

Forward flow (small -> large) follows the Borda-Carnot momentum balance (separation at the step, mixing loss). Reverse flow (large -> small, a contraction) follows a vena-contracta total-pressure loss K_c * (1/2 rho u^2)_small with K_c = (1/cc - 1)^2, referenced to the downstream (small-port) dynamic head. The small/large sides are identified from the attached edge areas, so cc always acts on whichever direction is contracting.

Parameters

Name Type Description Default
name str Element label. 'sac'
cc float Vena-contracta contraction coefficient for the reverse (contracting) flow, in (0, 1]. cc = 1 (default) is the loss-free contraction: the reverse branch reduces to exact total-pressure continuity. Use a tabulated value for the geometry (e.g. ~0.62 for a sharp-edged contraction at a small area ratio; Weisbach / Idelchik). Forward (expanding) flow is unaffected by cc. The loss uses the incompressible 1/2 rho u^2 head, so it is accurate only to O(M^2); a dedicated contraction element resolving the vena- contracta state (exact at higher Mach) is planned. 1.0
eps float Optionally sharpens this element’s momentum<->contraction switch (see ElementSpec.eps); use a small value (e.g. 1e-6 * mdot_ref) when the flow is firmly one-directional and an accurate perturbation jump is wanted. None
l_up float Optional storage lengths [m] (default 0). A sudden change is geometrically thin (l_up = l_down = 0); supply end_correction for the entrained-mass inertance the step still carries. See :func:isentropic_area_change. 0.0
l_down float Optional storage lengths [m] (default 0). A sudden change is geometrically thin (l_up = l_down = 0); supply end_correction for the entrained-mass inertance the step still carries. See :func:isentropic_area_change. 0.0
end_correction float Optional storage lengths [m] (default 0). A sudden change is geometrically thin (l_up = l_down = 0); supply end_correction for the entrained-mass inertance the step still carries. See :func:isentropic_area_change. 0.0
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