elements.catalog.choked_nozzle_outlet

elements.catalog.choked_nozzle_outlet(
    throat_area,
    back_pressure=None,
    name='outlet',
    perturbation_bc=None,
)

Compact choked-nozzle outlet of throat area throat_area lumped downstream.

Models a sonic (M=1) throat just beyond the outlet plane: the outflow is the critical mass flux for the interior stagnation state and the throat area, so the static pressure floats (the choked mass flow is set by the upstream total state, not a back-pressure). Because the nozzle is compact (lumped), the application plane stays subsonic (the sonic point is in the throat, not explicitly in the domain). Left at perturbation_bc=None the acoustic termination is the inherited linearization of the critical-mass-flux row, which is the compact choked-nozzle (Marble-Candel) reflection with its entropy -> acoustic coupling – no separately specified boundary condition needed.

Use it when the convergent section is acoustically compact; resolving the higher-Mach part of the contraction explicitly and lumping only the near-throat remainder makes the compact assumption progressively better. A choked throat is one-way, so this is an outflow-only boundary: it does not model ingestion (the critical mass flux is always positive, so the converged flow cannot reverse here).

This element asserts the nozzle is choked: it imposes the critical mass flux unconditionally (the mass flow scales with the interior total pressure and stays sonic-throat-consistent at any total pressure, i.e. there is no back-pressure to detect unchoking. throat_area must be smaller than the outlet edge area (a contraction; enforced at build time). If the nozzle may be unchoked at low pressure ratio, use :func:pressure_outlet instead – its emergent complementarity handles the choked/unchoked transition against a prescribed back-pressure.

Parameters

Name	Type	Description	Default
throat_area	float	Sonic-throat area A* [m^2] of the lumped nozzle (A* < A_outlet so the approach stays subsonic). Must be > 0.	required
back_pressure	float	Ambient (discharge) pressure [Pa] the nozzle exhausts into. Purely a diagnostic: no kernel reads it, but when given, the solve checks it against the throat’s critical (sonic) pressure at the converged state and warns if it is too high for the nozzle to choke (i.e. the compact choked-nozzle model would not apply). None (default) skips the check. See :meth:~nefes.shell.network.Solution.unchoked_nozzles.	None
name	str	Element label.	'outlet'
perturbation_bc	PerturbationBC	Acoustic termination; None inherits the linearized choked-nozzle reflection.	None