Inlet.hpp File Reference

Street inlet capture efficiency — FHWA HEC-22. More...

#include <cstdint>
#include <vector>

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Classes
struct	openswmm::inlet::Geom
	Street / channel geometry seen by one inlet, in INTERNAL units. More...
struct	openswmm::inlet::Design
	One inlet design in INTERNAL units (legacy TInletDesign, inlet.c:66-74). More...
struct	openswmm::inlet::UsageParams
	The per-placement half of one usage row (legacy TInlet fields). More...
struct	openswmm::inlet::InletSoA
class	openswmm::inlet::InletSolver

Namespaces
namespace	openswmm
namespace	openswmm::inlet

Enumerations
enum class	openswmm::inlet::InletType : int {   openswmm::inlet::GRATE = 0 ,   openswmm::inlet::CURB = 1 ,   openswmm::inlet::COMBO = 2 ,   openswmm::inlet::SLOTTED = 3 ,   openswmm::inlet::DROP_GRATE = 4 ,   openswmm::inlet::DROP_CURB = 5 ,   openswmm::inlet::CUSTOM = 6 }
enum class	openswmm::inlet::GrateType : int {   openswmm::inlet::P_BAR_50 = 0 ,   openswmm::inlet::P_BAR_50x100 = 1 ,   openswmm::inlet::P_BAR_30 = 2 ,   openswmm::inlet::CURVED_VANE = 3 ,   openswmm::inlet::TILT_BAR_45 = 4 ,   openswmm::inlet::TILT_BAR_30 = 5 ,   openswmm::inlet::RETICULINE = 6 ,   openswmm::inlet::GENERIC = 7 }
	Legacy enum GrateType (inlet.c:124-127). More...
enum class	openswmm::inlet::Placement : int {   openswmm::inlet::AUTOMATIC = 0 ,   openswmm::inlet::ON_GRADE = 1 ,   openswmm::inlet::ON_SAG = 2 }
enum class	openswmm::inlet::ThroatAngle : int {   openswmm::inlet::HORIZONTAL = 0 ,   openswmm::inlet::INCLINED = 1 ,   openswmm::inlet::VERTICAL = 2 }
	Legacy enum ThroatAngleType (inlet.c:131) — InletStore::curb_throat. More...
enum class	openswmm::inlet::CurveKind : int {   openswmm::inlet::UNRESOLVED = 0 ,   openswmm::inlet::DIVERSION = 1 ,   openswmm::inlet::RATING = 2 }
	InletStore::curve_kind codes for a CUSTOM design. More...

Functions
double	openswmm::inlet::getEo (double sr, double ts, double w)
	Compute the depressed-gutter flow ratio using HEC-22 Eq4-4.
double	openswmm::inlet::getFlowSpread (const Geom &g, double Q)
	Compute approach flow spread with crown limiting and depressed-gutter iteration.
double	openswmm::inlet::getGutterFlowRatio (const Geom &g, double w)
	Compute the fraction of street flow above a selected gutter width.
double	openswmm::inlet::getGutterAreaRatio (const Geom &g, double grate_width, double area)
	Compute the grate-width correction to depressed-gutter intercepted flow.
double	openswmm::inlet::getSplashOverVelocity (int grate_type, double grate_length)
	Evaluate the standard grate splash-over velocity polynomial.
double	openswmm::inlet::getGrateInletCapture (const Design &d, Geom &g, double Q)
	Compute one on-grade grate's frontal and side capture.
double	openswmm::inlet::getCurbInletCapture (const Geom &g, double Q, double opening_length)
	Compute on-grade curb-opening capture from equivalent cross slope.
double	openswmm::inlet::getOnGradeInletCapture (const Design &d, Geom &g, double Q, double depth)
	Compute a single on-grade inlet or combination sweeper/grate capture.
double	openswmm::inlet::getOnGradeCapturedFlow (const Design &d, const UsageParams &u, Geom &g, double q, double depth)
	Compute series inlet capture across the current street sides.
void	openswmm::inlet::findOnSagGrateFlows (const Design &d, const Geom &g, double depth, double *weir_flow, double *orifice_flow)
	Compute the active grate weir or orifice contribution for one sag inlet.
void	openswmm::inlet::findOnSagCurbFlows (const Design &d, const Geom &g, double depth, double opening_length, double *weir_flow, double *orifice_flow)
	Compute sag curb-opening weir/orifice contributions with transition blending.
double	openswmm::inlet::getCurbOrificeFlow (double flow_depth, double opening_height, double opening_length, int throat_angle)
	Compute sag curb-opening orifice flow using throat-adjusted head.
double	openswmm::inlet::getOnSagSlottedFlow (const Design &d, double depth)
	Compute one sag slotted-drain weir or orifice capacity.
double	openswmm::inlet::getOnSagInletCapture (const Design &d, const Geom &g, double depth)
	Combine one sag inlet's grate, sweeper and curb-orifice contributions.
double	openswmm::inlet::getOnSagCapturedFlow (const Design &d, const UsageParams &u, const Geom &g, double depth, int nsides_prev)
	Scale sag capacity using usage factors and legacy carried-over street sides.
double	openswmm::inlet::getCustomCapturedFlow (const UsageParams &u, const Geom &g, const Table &curve, int curve_kind, double q, double depth, double ucf_flow, double ucf_len)
	Compute custom inlet capture from authored diversion or rating curves.
double	openswmm::inlet::getInletArea (const Design &d, const UsageParams &u)
	Compute the usage's effective open inlet area for backflow weighting.

Variables
constexpr double	openswmm::inlet::MIN_RUNOFF_FLOW = 0.001
	Legacy MIN_RUNOFF_FLOW (consts.h:203) — cfs.
constexpr double	openswmm::inlet::INLET_FUDGE = 0.0001
	Legacy FUDGE (consts.h:272).
constexpr double	openswmm::inlet::INLET_BIG = 1.0e10
	Legacy BIG (consts.h:118).

Detailed Description

Street inlet capture efficiency — FHWA HEC-22.

Inlet types: GRATE, CURB, COMBO, SLOTTED, DROP_GRATE, DROP_CURB, CUSTOM. On-grade capture uses splash-over velocity and frontal / side flow fractions (HEC-22 Eq. 4-16 … 4-24); on-sag capture uses the weir ↔ orifice transition (Eq. 4-26 … 4-33).

Two host kinds share one kernel and one statistics block (plans/INLET_JUNCTION_IMPLEMENTATION_PLAN_2026-09-05.md §2.1):

• conduit-attribute usage — [INLET_USAGE], host = a STREET conduit, bypass node = that conduit's downstream node;
• inlet junction — [INLET_JUNCTIONS], host = the node itself, approach flow from the attached street conduit(s).

The pure kernel functions below are transliterations of the legacy file-scope routines and carry the HEC-22 equation numbers; they take their state through openswmm::inlet::Geom / openswmm::inlet::Design / openswmm::inlet::UsageParams instead of legacy's module-level shared variables, so they are directly unit-testable.

Note

Legacy reference: src/legacy/engine/inlet.c

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com

Copyright

Copyright (c) 2026 Caleb Buahin. All rights reserved.

License

Apache-2.0