Arrhenius slope E/R, kelvin: viscosity × e^(activation·(1/T − 1/eruption)).
Air temperature, kelvin.
Convective heat transfer to the air, W/(m²·K).
Crust tensile strain at which it cracks open (melt is cohesive up to 20 %).
Crust forms over this band above the solidus, kelvin.
Bulk density, kg/m³ (vesicular pāhoehoe ~2200, dense ʻaʻā ~2600). Sets the particle mass.
Effective thermal diffusivity between particles, m²/s (rock ~5e-7; larger stands in for sub-grid mixing).
Thermal emissivity of the surface.
Eruption (vent) temperature, kelvin.
Conductance of the contact with the ground, W/(m²·K).
Ground temperature, kelvin.
Specific heat, J/(kg·K).
Melt yield strength, Pa (Bingham). Lab melts show 10²–10³ Pa, flow margins (levees) 10³–10⁴ Pa: it stands in for the skin a real flow grows within seconds at its margins, which a particle Δx/2 thick cannot. It keeps lobes whole and thick instead of spreading into sheets thinner than the solver resolves (they would tear into particle rows).
Poisson's ratio.
Thermal skin, metres: how thick a layer of an exposed particle the surface loss cools. A particle is Δx/2 across, far thicker than the centimetres a real crust grows in the first minutes, so the surface particles cool as this skin.
Solidus, kelvin: fully crust at and below it.
Dynamic viscosity at the eruption temperature, Pa·s.
Viscosity cap, Pa·s: the stiffest melt the explicit solver resolves (it sets the time step, Δx²·ρ/(6·cap)).
Crust shear strength (von Mises), Pa.
Young's modulus, Pa: the volume response of the melt and the stiffness of the crust (softened for real time).
Parameters of the
lavamaterial (all live throughMPMSolver.set({ materials: { lava: {...} } })).