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dirt_granular

Granular contact physics for DIRT: Hertz/Hooke normal contact, Mindlin tangential friction, rolling and twisting resistance, adhesion, rotational dynamics, and granular temperature output.

What it does

Core DEM physics for spherical particle simulations:

Normal contact: Hertz (nonlinear F_n ∝ δ^1.5, default) or Hooke (linear F_n ∝ δ), with viscoelastic damping
Tangential friction: Mindlin spring-history with Coulomb cap and viscous damping; per-contact spring rotated into the tangent plane each step
Rolling resistance: constant torque (default) or SDS spring-dashpot-slider
Twisting friction: constant torque (default) or SDS
Adhesion / cohesion: JKR (extended range), DMT (contact-only), or SJKR area-based cohesion
Rotational dynamics: quaternion velocity Verlet (I = 2/5 m r² for solid spheres)
Output: granular temperature (velocity fluctuation) time series

Overlap is guarded: pairs exceeding LARGE_OVERLAP_WARN_THRESHOLD warn (forces still computed, capped), and more than MAX_OVERLAP_WARNINGS per step aborts with an actionable message.

Key types

Item	Role
`GranularDefaultPlugins`	Default DEM granular plugin group (contact + rotation + insertion + temp)
`HertzMindlinContactPlugin`	Fused normal + tangential contact (primary code path)
`RotationalDynamicsPlugin`	Quaternion velocity Verlet for angular DOF
`GranularTempPlugin`	Granular temperature file output

Modules: contact (fused Hertz–Mindlin + Hooke), tangential (ContactHistoryStore), rotational, granular_temp.

TOML configuration

[[dem.materials]]
name = "glass"
youngs_modulus = 8.7e9      # Pa
poisson_ratio = 0.3
restitution = 0.95          # coeff. of restitution (0–1)
friction = 0.4              # sliding friction μ
rolling_friction = 0.1      # rolling friction μ_r
cohesion_energy = 0.0       # J/m² (SJKR, 0 = disabled)
surface_energy = 0.0        # J/m² (JKR/DMT, 0 = disabled)

[dem]
contact_model = "hertz"     # "hertz" (default) or "hooke"
adhesion_model = "jkr"      # "jkr" (default) or "dmt"
rolling_model = "constant"  # "constant" (default) or "sds"
twisting_model = "constant" # "constant" (default) or "sds"

Usage

use dirt_core::prelude::*;

let mut app = App::new();
app.add_plugins(CorePlugins).add_plugins(GranularDefaultPlugins);
app.start();

GranularDefaultPlugins adds per-atom material properties, particle insertion, velocity Verlet, Hertz–Mindlin contact, rotational dynamics, and granular temperature output. It does not include infrastructure plugins; pair it with CorePlugins for input, comm, domain, neighbor, run, and print.

Part of the DIRT workspace.

License