link.c File Reference

Legacy link configuration and hydraulic property calculations. More...

#include <string.h>
#include <stdlib.h>
#include <math.h>
#include "headers.h"
#include "inlet.h"

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Macros
#define	_CRT_SECURE_NO_DEPRECATE

Functions
int	link_readParams (int j, int type, int k, char *tok[], int ntoks)
	Reads parameters for a specific type of link from a tokenized line of input data.
int	link_readXsectParams (char *tok[], int ntoks)
	Reads a link's cross section parameters from a tokenized line of input data. Formats: Link Shape Geom1 Geom2 Geom3 Geom4 (Barrels Culvert) Link IRREGULAR TransectID Link STREET StreetID.
int	link_readLossParams (char *tok[], int ntoks)
	Reads local loss parameters for a link from a tokenized line of input data. Format: LinkID cInlet cOutlet cAvg FlapGate(YES/NO) SeepRate.
void	link_validate (int j)
	Validates a link's properties.
void	link_initState (int j)
	Initializes a link's state variables at start of simulation.
double	link_getInflow (int j)
	Finds total flow entering a link during current time step.
void	link_setOldHydState (int j)
	Replaces link's old hydraulic state values with current ones.
void	link_setOldQualState (int j)
	Replaces link's old water quality state values with current ones.
void	link_setTargetSetting (int j)
	Updates a link's target setting.
void	link_setSetting (int j, double tstep)
	Updates a link's setting as a result of a control action.
int	link_setFlapGate (int j, int n1, int n2, double q)
	Based on the sign of the flow, determines if a flap gate associated with the link should close or not.
void	link_getResults (int j, double f, float x[])
	Retrieves time-weighted average of old and new results for a link.
void	link_setOutfallDepth (int j)
	Sets depth at outfall node connected to link j.
double	link_getYcrit (int j, double q)
	Computes critical depth for given flow rate.
double	link_getYnorm (int j, double q)
	Computes normal depth for given flow rate.
double	link_getLength (int j)
	Finds true length of a link.
double	link_getVelocity (int j, double flow, double depth)
	Finds flow velocity given flow and depth.
double	link_getFroude (int j, double v, double y)
	Computes Froude Number for given velocity and flow depth.
double	link_getPower (int j)
	Computes power consumed by head loss (or head gain) of water flowing through a link.
double	link_getLossRate (int j, int routeModel, double q, double tstep)
	Computes rate at which flow volume is lost in a link due to evaporation and seepage.
char	link_getFullState (double a1, double a2, double aFull)
	Determines if a link is upstream, downstream or completely full.

Detailed Description

Legacy link configuration and hydraulic property calculations.

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com (OpenSWMM maintenance and extensions)

Copyright

Copyright (c) 2026 Caleb Buahin. OpenSWMM contributions only; original EPA SWMM credits are retained.

License

Apache-2.0 for OpenSWMM contributions; original EPA SWMM provenance is retained.

Macro Definition Documentation

_CRT_SECURE_NO_DEPRECATE

#define _CRT_SECURE_NO_DEPRECATE

Function Documentation

link_getFroude()

double link_getFroude	(	int	j,
		double	v,
		double	y )

Computes Froude Number for given velocity and flow depth.

Parameters

[in]	j	Link index.
[in]	v	Flow velocity (fps).
[in]	y	Flow depth (ft).

Returns

Froude Number.

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link_getFullState()

char link_getFullState	(	double	a1,
		double	a2,
		double	aFull )

Determines if a link is upstream, downstream or completely full.

Parameters

[in]	a1	Upstream link area (ft2).
[in]	a2	Downstream link area (ft2).
[in]	aFull	Area of full conduit.

Returns

Fullness state of a link.

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link_getInflow()

double link_getInflow

(

int

j

)

Finds total flow entering a link during current time step.

Parameters

[in]

j

Link index.

Returns

Link flow rate (cfs).

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link_getLength()

double link_getLength

(

int

j

)

Finds true length of a link.

Parameters

[in]

j

Link index.

Returns

Length (ft).

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link_getLossRate()

double link_getLossRate	(	int	j,
		int	routeModel,
		double	q,
		double	tstep )

Computes rate at which flow volume is lost in a link due to evaporation and seepage.

Parameters

[in]	j	Link index.
[in]	routeModel	Flow routing model type.
[in]	q	Flow rate (ft3/sec).
[in]	tstep	Time step (sec).

Returns

Uniform loss rate in link (ft3/sec).

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link_getPower()

double link_getPower

(

int

j

)

Computes power consumed by head loss (or head gain) of water flowing through a link.

Parameters

[in]

j

Link index.

Returns

Power consumed by link in kwatts.

link_getResults()

void link_getResults	(	int	j,
		double	f,
		float	x[] )

Retrieves time-weighted average of old and new results for a link.

Parameters

[in]	j	Link index.
[in]	f	Time weighting factor.
[out]	x	Array of weighted results.

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link_getVelocity()

double link_getVelocity	(	int	j,
		double	flow,
		double	depth )

Finds flow velocity given flow and depth.

Parameters

[in]	j	Link index.
[in]	flow	Link flow rate (cfs).
[in]	depth	Link flow depth (ft).

Returns

Flow velocity (fps).

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link_getYcrit()

double link_getYcrit	(	int	j,
		double	q )

Computes critical depth for given flow rate.

Parameters

[in]	j	Link index.
[in]	q	Link flow rate (cfs).

Returns

Critical depth (ft).

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link_getYnorm()

double link_getYnorm	(	int	j,
		double	q )

Computes normal depth for given flow rate.

Parameters

[in]	j	Link index.
[in]	q	Link flow rate (cfs).

Returns

Normal depth (ft).

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link_initState()

void link_initState

(

int

j

)

Initializes a link's state variables at start of simulation.

Parameters

[in]

j

Link index.

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link_readLossParams()

int link_readLossParams	(	char *	tok[],
		int	ntoks )

Reads local loss parameters for a link from a tokenized line of input data. Format: LinkID cInlet cOutlet cAvg FlapGate(YES/NO) SeepRate.

Parameters

	tok	Array of string tokens.
[in]	ntoks	Number of tokens.

Returns

An error code.

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link_readParams()

int link_readParams	(	int	j,
		int	type,
		int	k,
		char *	tok[],
		int	ntoks )

Reads parameters for a specific type of link from a tokenized line of input data.

Parameters

[in]	j	Link index.
[in]	type	Link type code.
[in]	k	Link type index.
	tok	Array of string tokens.
[in]	ntoks	Number of tokens.

Returns

An error code.

link_readXsectParams()

int link_readXsectParams	(	char *	tok[],
		int	ntoks )

Reads a link's cross section parameters from a tokenized line of input data. Formats: Link Shape Geom1 Geom2 Geom3 Geom4 (Barrels Culvert) Link IRREGULAR TransectID Link STREET StreetID.

Parameters

	tok	Array of string tokens.
[in]	ntoks	Number of tokens.

Returns

An error code.

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link_setFlapGate()

int link_setFlapGate	(	int	j,
		int	n1,
		int	n2,
		double	q )

Based on the sign of the flow, determines if a flap gate associated with the link should close or not.

Parameters

[in]	j	Link index.
[in]	n1	Index of node on upstream end of link.
[in]	n2	Index of node on downstream end of link.
[in]	q	Signed flow value (value and units don't matter).

Returns

TRUE if there is reverse flow through a flap gate associated with the link.

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link_setOldHydState()

void link_setOldHydState

(

int

j

)

Replaces link's old hydraulic state values with current ones.

Parameters

[in]

j

Link index.

link_setOldQualState()

void link_setOldQualState

(

int

j

)

Replaces link's old water quality state values with current ones.

Parameters

[in]

j

Link index.

link_setOutfallDepth()

void link_setOutfallDepth

(

int

j

)

Sets depth at outfall node connected to link j.

Parameters

[in]

j

Link index.

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link_setSetting()

void link_setSetting	(	int	j,
		double	tstep )

Updates a link's setting as a result of a control action.

Parameters

[in]	j	Link index.
[in]	tstep	Time step over which setting is adjusted.

link_setTargetSetting()

void link_setTargetSetting

(

int

j

)

Updates a link's target setting.

Parameters

[in]

j

Link index.

link_validate()

void link_validate

(

int

j

)

Validates a link's properties.

Parameters

[in]

j

Link index.

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