Classes
class	LagrangianSolver

class	RwptDispersion
	Persistent particle field + the per-substep exchange operator. More...

class	SegmentStore

struct	SpeciesRowLayout
	The segment store's species-row layout, computed in ONE place. More...

Functions
SpeciesRowLayout	rowLayout (const SimulationContext &ctx)
	The single source of truth for the row layout. Reserved rows are appended after the pollutants in a fixed order (age, then temperature) so an index means the same thing everywhere.

std::uint64_t	rwpt_hash (std::uint64_t z)
	Mix one unsigned64-bit deterministic random key.

double	rwpt_uniform (std::uint64_t seed, std::uint64_t link, std::uint64_t stepc, std::uint64_t particle, std::uint64_t draw)
	Uniform in (0,1), keyed. `draw` distinguishes multiple draws per particle.

double	rwpt_normal (std::uint64_t seed, std::uint64_t link, std::uint64_t stepc, std::uint64_t particle, std::uint64_t draw)
	Standard normal (Box–Muller on two keyed uniforms).

double	rwpt_u_dev (double eta, double ubar, double ustar, bool turbulent)
	Velocity DEVIATION u(η) − ū. Turbulent: log-law; laminar: parabola.

double	rwpt_d_eta (double eta, double h, double ustar, bool turbulent)
	Vertical diffusivity in η-units (D_t/h²), and its η-gradient (the Itô drift). Turbulent: Rouse parabola κ·u*·h·η(1−η); laminar: molecular.

double	rwpt_d_eta_grad (double eta, double h, double ustar, bool turbulent)
	Evaluate coordinate diffusivity gradient used as stochastic drift.

double	rwpt_hyd_radius (double area, double depth, double diam, bool circular)
	Hydraulic radius: exact for CIRCULAR from flow area, ≈ depth otherwise (wide-channel v1 approximation, recorded).

Variables
constexpr double	kTinyFlow = 1.0e-8
	cfs; below this a link moves nothing

constexpr int	kRwptParticlesPerLink = 2000

constexpr double	kKappa = 0.41
	von Kármán

constexpr double	kNuWater = 1.05e-5
	kinematic viscosity, ft²/s

constexpr double	kDm = 1.3454e-8
	molecular diffusivity, ft²/s

constexpr double	kEtaMin = 1.0e-3
	log-law floor

constexpr double	kReTurb = 2000.0

constexpr int	kMaxSegmentsPerLink = 100

constexpr double	kMergeAtol = 1.0e-6

constexpr double	kMergeRtol = 1.0e-4

Function Documentation

◆ rowLayout()

SpeciesRowLayout openswmm::lard::rowLayout ( const SimulationContext & ctx )

inline

The single source of truth for the row layout. Reserved rows are appended after the pollutants in a fixed order (age, then temperature) so an index means the same thing everywhere.

Resolve the carried network1D row order for the LARD owner.

Parameters

[in] ctx Stable transport class policy and active legacy-reaction profile.

Returns: Pollutants first, optional age seconds, temperature degC, then enabled native MSX species; absent row selectors=-1, ns is total. No state/clock change, allocation or shape preparation.

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◆ rwpt_d_eta()

double openswmm::lard::rwpt_d_eta	(	double	eta,
		double	h,
		double	ustar,
		bool	turbulent )

inline

Vertical diffusivity in η-units (D_t/h²), and its η-gradient (the Itô drift). Turbulent: Rouse parabola κ·u*·h·η(1−η); laminar: molecular.

Evaluate diffusivity in the dimensionless vertical particle coordinate.

Parameters

[in]	eta	Dimensionless particle ordinate, caller supplies0..1 for physical profile.
[in]	h	Finite positive water depth ft; no zero guard.
[in]	ustar	Finite nonnegative friction speed ft/s.
[in]	turbulent	True selects shear profile, false molecular laminar profile.

Returns: Inverse-seconds diffusivity: laminar molecular Dm/h², turbulent kappa*ustar*clamp(eta,0,1)*(1-clamp(eta,0,1))/h.

Note: Pure/no allocation; no generic sign/finite/dry-depth validation.

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◆ rwpt_d_eta_grad()

double openswmm::lard::rwpt_d_eta_grad	(	double	eta,
		double	h,
		double	ustar,
		bool	turbulent )

inline

Evaluate coordinate diffusivity gradient used as stochastic drift.

Parameters

[in]	eta	Dimensionless particle ordinate, caller supplies0..1 for physical profile.
[in]	h	Finite positive water depth ft; no zero guard.
[in]	ustar	Finite nonnegative friction speed ft/s.
[in]	turbulent	True selects shear profile, false molecular laminar profile.

Returns: 0 for laminar, otherwise kappa*ustar*(1-2*eta)/h in inverse seconds; eta is not clamped here.

Note: Pure/no allocation; no generic sign/finite/dry-depth validation.

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◆ rwpt_hash()

std::uint64_t openswmm::lard::rwpt_hash ( std::uint64_t z )

inline

Mix one unsigned64-bit deterministic random key.

Parameters

[in] z Counter/key input, unsigned overflow intentionally wraps modulo2^64.

Returns: SplitMix-style mixed key; pure, allocation-free, independent of shared random state.

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◆ rwpt_hyd_radius()

double openswmm::lard::rwpt_hyd_radius	(	double	area,
		double	depth,
		double	diam,
		bool	circular )

inline

Hydraulic radius: exact for CIRCULAR from flow area, ≈ depth otherwise (wide-channel v1 approximation, recorded).

Estimate hydraulic radius for the RWPT turbulence calculation.

Parameters

[in]	area	Unused area argument retained for geometry-call symmetry; circle area is recomputed.
[in]	depth	Water depth ft; noncircular/invalid-circle fallback max(depth,0).
[in]	diam	Positive circular full diameter ft when circular is true.
[in]	circular	True selects circular-segment wetted geometry.

Returns: Radius ft from circle area/perimeter after clamped acos argument; tiny angle/perimeter uses depth fallback. No finite geometry repair, allocation or state mutation.

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◆ rwpt_normal()

double openswmm::lard::rwpt_normal	(	std::uint64_t	seed,
		std::uint64_t	link,
		std::uint64_t	stepc,
		std::uint64_t	particle,
		std::uint64_t	draw )

inline

Standard normal (Box–Muller on two keyed uniforms).

Generate a deterministic Box-Muller normal variate from adjacent uniform draws.

Parameters

[in]	seed	Reproducibility seed, no global generator state.
[in]	link	Stable native link identity key.
[in]	stepc	Accepted quality-step counter; repeat tuple reproduces sample.
[in]	particle	Zero-based particle key; particle*8+draw wraps unsigned arithmetic.
[in]	draw	Draw stream key (draw+1 also used by normal).

Returns: Standard normal sample using draws draw and draw+1; no cached paired variate.

Note: Pure/no allocation or model mutation; counter tuple design, not call order, controls reproducibility.

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◆ rwpt_u_dev()

double openswmm::lard::rwpt_u_dev	(	double	eta,
		double	ubar,
		double	ustar,
		bool	turbulent )

inline

Velocity DEVIATION u(η) − ū. Turbulent: log-law; laminar: parabola.

Evaluate longitudinal particle velocity relative to cross-sectional mean.

Parameters

[in]	eta	Dimensionless ordinate, normally0..1; turbulent log floors at1e-3.
[in]	ubar	Mean positive speed ft/s used by laminar profile.
[in]	ustar	Friction speed ft/s used by turbulent log profile.
[in]	turbulent	True selects log-law, false parabolic laminar deviation.

Returns: Velocity deviation ft/s, not absolute velocity. No finite/range repair outside log floor, allocation or state mutation.

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◆ rwpt_uniform()

double openswmm::lard::rwpt_uniform	(	std::uint64_t	seed,
		std::uint64_t	link,
		std::uint64_t	stepc,
		std::uint64_t	particle,
		std::uint64_t	draw )

inline

Uniform in (0,1), keyed. draw distinguishes multiple draws per particle.

Generate a deterministic counter-keyed pseudorandom uniform variate.

Parameters

[in]	seed	Reproducibility seed, no global generator state.
[in]	link	Stable native link identity key.
[in]	stepc	Accepted quality-step counter; repeat tuple reproduces sample.
[in]	particle	Zero-based particle key; particle*8+draw wraps unsigned arithmetic.
[in]	draw	Draw stream key (draw+1 also used by normal).

Returns: Nominal open-unit variate from53 key bits with half-unit offset; final floating rounding can reach1.

Note: Pure/no allocation or model mutation; counter tuple design, not call order, controls reproducibility.

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Variable Documentation

◆ kDm

double openswmm::lard::kDm = 1.3454e-8

constexpr

molecular diffusivity, ft²/s

◆ kEtaMin

double openswmm::lard::kEtaMin = 1.0e-3

constexpr

log-law floor

◆ kKappa

double openswmm::lard::kKappa = 0.41

constexpr

von Kármán

◆ kMaxSegmentsPerLink

int openswmm::lard::kMaxSegmentsPerLink = 100

constexpr

EPANET-style cap on segments per link (strategy §4.1 default; the [OPTIONS] MAX_SEGMENTS_PER_LINK override arrives with X3).

◆ kMergeAtol

double openswmm::lard::kMergeAtol = 1.0e-6

constexpr

Merge tolerance for a released segment against the current front segment (strategy §4.5): merge when |dC| <= atol + rtol·|C_front| for EVERY species. Plug-flow stretches then collapse to one segment — the dominant constant-factor win in EPANET's LTD.

◆ kMergeRtol

double openswmm::lard::kMergeRtol = 1.0e-4

constexpr

◆ kNuWater

double openswmm::lard::kNuWater = 1.05e-5

constexpr

kinematic viscosity, ft²/s

◆ kReTurb

double openswmm::lard::kReTurb = 2000.0

constexpr

◆ kRwptParticlesPerLink

int openswmm::lard::kRwptParticlesPerLink = 2000

constexpr

◆ kTinyFlow

double openswmm::lard::kTinyFlow = 1.0e-8

constexpr

cfs; below this a link moves nothing

Classes

Functions

Variables

Function Documentation

◆ rowLayout()

◆ rwpt_d_eta()

◆ rwpt_d_eta_grad()

◆ rwpt_hash()

◆ rwpt_hyd_radius()

◆ rwpt_normal()

◆ rwpt_u_dev()

◆ rwpt_uniform()

Variable Documentation

◆ kDm

◆ kEtaMin

◆ kKappa

◆ kMaxSegmentsPerLink

◆ kMergeAtol

◆ kMergeRtol

◆ kNuWater

◆ kReTurb

◆ kRwptParticlesPerLink

◆ kTinyFlow