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 infil_factor = 1.0,
                        double recovery_factor = 1.0);

double curvenum_getInfil(CurveNumState& state, double precip, double depth, double dt,
                         double recovery_factor = 1.0);

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