Infiltration.hpp

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// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2026 Caleb Buahin
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

 
#ifndef OPENSWMM_INFILTRATION_HPP
#define OPENSWMM_INFILTRATION_HPP
 
namespace openswmm {
 
struct SimulationOptions;
 
// ============================================================================
// Infiltration model type
// ============================================================================
 
enum class InfilModel : int {
    HORTON         = 0,
    MOD_HORTON     = 1,   
    GREEN_AMPT     = 2,
    MOD_GREEN_AMPT = 3,   
    CURVE_NUM      = 4,
    CONSTANT       = 5    
};
 
// ============================================================================
// Horton infiltration state (per subcatchment)
// ============================================================================
 
struct HortonState {
    double f0      = 0.0;   
    double fmin    = 0.0;   
    double decay   = 0.0;   
    double regen   = 0.0;   
    double Fmax    = 0.0;   
    double tp      = 0.0;   
    double Fe      = 0.0;   
    double Fmh     = 0.0;   
};
 
// ============================================================================
// Green-Ampt state (per subcatchment)
// ============================================================================
 
struct GreenAmptState {
    double S       = 0.0;   
    double Ks      = 0.0;   
    double IMDmax  = 0.0;   
    double IMD     = 0.0;   
    double F       = 0.0;   
    double Fu      = 0.0;   
    double Fumax   = 0.0;   
    double Lu      = 0.0;   
    double T       = 0.0;   
    bool   saturated = false; 
};
 
// ============================================================================
// SCS Curve Number state (per subcatchment)
// ============================================================================
 
struct CurveNumState {
    double Smax    = 0.0;   
    double S       = 0.0;   
    double Se      = 0.0;   
    double P       = 0.0;   
    double F       = 0.0;   
    double f       = 0.0;   
    double regen   = 0.0;   
    double T       = 0.0;   
    double Tmax    = 0.0;   
};
 
// ============================================================================
// Infiltration functions
// ============================================================================
 
namespace infil {
 
// The state structs above are declared at `openswmm` scope. Re-export them
// here so callers may also spell them `infil::HortonState` (the 2D adapter
// contract, src/engine/2d/infil/Infil2D.hpp, uses that qualification).
using ::openswmm::HortonState;
using ::openswmm::GreenAmptState;
using ::openswmm::CurveNumState;

double horton_getInfil(HortonState& state, double precip, double depth, double dt);

double modHorton_getInfil(HortonState& state, double precip, double depth, double dt);

double grnampt_getInfil(GreenAmptState& state, double precip, double depth, double dt,
                        InfilModel model_type = InfilModel::GREEN_AMPT);

double curvenum_getInfil(CurveNumState& state, double precip, double depth, double dt);

double constant_getInfil(double rate_ftsec, double precip, double depth, double dt);

void horton_init(HortonState& state, double f0, double fmin,
                 double decay, double regen, double Fmax,
                 const SimulationOptions& opts);

void grnampt_init(GreenAmptState& state, double S, double Ks, double IMD,
                  const SimulationOptions& opts);

void curvenum_init(CurveNumState& state, double CN, double regen);
 
} // namespace infil
} // namespace openswmm
 
#endif // OPENSWMM_INFILTRATION_HPP