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Minimal Valid Configuration

The smallest valid SimulationConfig JSON for mod-PATH3DU. Every required field is present; all optional fields are omitted or set to their simplest valid value.

Configuration

{
  "velocity_method": "Waterloo",
  "solver": "DormandPrince",
  "adaptive": {
    "tolerance": 1e-6,
    "safety": 0.9,
    "alpha": 0.2,
    "min_scale": 0.2,
    "max_scale": 5.0,
    "max_rejects": 10,
    "min_dt": 1e-10,
    "euler_dt": 1.0
  },
  "dispersion": {
    "method": "None"
  },
  "retardation_enabled": false,
  "capture": {
    "max_time": 365250.0,
    "max_steps": 1000000,
    "stagnation_velocity": 1e-12,
    "stagnation_limit": 100
  },
  "initial_dt": 1.0,
  "max_dt": 100.0,
  "direction": 1.0
}

Field Descriptions

Field Value Why
velocity_method "Waterloo" The only supported velocity interpolation method
solver "DormandPrince" Recommended default — adaptive 5th-order Runge-Kutta with good accuracy/cost ratio
direction 1.0 Forward tracking (in the direction of groundwater flow)
initial_dt 1.0 Initial time step size (days)
max_dt 100.0 Maximum allowed time step (days)
retardation_enabled false No retardation — particles move at pore velocity
adaptive (object) Adaptive step-size control parameters
dispersion {"method": "None"} No dispersion — purely advective tracking
capture (object) Termination criteria for particle tracking

Adaptive Stepping Parameters

Field Value Description
tolerance 1e-6 Local error tolerance for step acceptance
safety 0.9 Safety factor applied to predicted optimal step size
alpha 0.2 PI controller exponent for step-size scaling
min_scale 0.2 Minimum step-size scale factor (prevents drastic shrinkage)
max_scale 5.0 Maximum step-size scale factor (prevents drastic growth)
max_rejects 10 Maximum consecutive rejected steps before error
min_dt 1e-10 Absolute minimum time step (days)
euler_dt 1.0 Fixed step size used by the Euler solver

Capture (Termination) Parameters

Field Value Description
max_time 365250.0 Maximum tracking time — 1000 years in days
max_steps 1000000 Maximum number of integration steps
stagnation_velocity 1e-12 Velocity below which a particle is considered stagnant
stagnation_limit 100 Consecutive stagnant steps before termination

What This Config Does

Uses the DormandPrince adaptive solver for forward advective particle tracking with no dispersion and no retardation. Particles are tracked for up to 1000 years or 1,000,000 steps, whichever comes first. Stagnant particles (velocity below 10⁻¹² m/day for 100 consecutive steps) are terminated early.

Schema Validation

This configuration has been validated against mp3du_schema.json.

See Also