# Angle of Repose Digital Twin — Simulator Diagnostic Report

## PASSED — FULL EXPERIMENT UNLOCKED

Completed in 376.8 seconds. These diagnostics check measurement mathematics, amount normalization, shared-material rules, gravity-only release, settling, resolution, and valid pile geometry.

## Scientific basis

The UCF angle measurements are not used by these diagnostics and cannot tune the physics. They are revealed only in the final comparison report after research trials are saved. The acceptance bands come from published dry-granular behavior: glass-bead repose is commonly reported in the low-to-mid 20s and largely independent of bead size, while dry quartz sand varies from the high 20s into the 30s with particle shape, packing, moisture, and measurement method. Passing means the simulator is internally coherent and scientifically plausible; it does not guarantee agreement with the UCF study.

References: Higashi & Sumita (2009); Sunday et al. (2020).

## Measurement mathematics

Known synthetic angle | Measured | Status
--- | --- | ---
15.0° | 15.02° | PASS
20.0° | 20.01° | PASS
25.0° | 24.98° | PASS
30.0° | 29.95° | PASS
35.0° | 35.17° | PASS
40.0° | 40.04° | PASS

## Model invariants

Check | Evidence | Status
--- | --- | ---
Equal one-cup solid volume | 0.250000 normalized units in every one-cup condition | PASS
Two cups means exactly twice the amount | 1000 particles and 0.500000 volume units | PASS
One shared quartz contact model | All four quartz conditions use identical contact properties | PASS
One shared glass contact model | One-cup and two-cup beads use identical contact properties | PASS
Gravity-only release | Every planned particle begins with zero horizontal launch velocity | PASS
Quartz size-class consistency | Shared quartz model should vary moderately, not become four different materials | PASS
Glass amount independence | Doubling material amount must not redefine the bead material angle | PASS

## Headless physics pilots

Condition | Angle | Settled | Particle layers | X/Y difference | Status
--- | --- | --- | --- | --- | ---
Unsieved Quartz Sand | 33.92° | YES | 5.0 | 0.12° | PASS
Quartz 125-250 um | 36.13° | YES | 6.1 | 1.59° | PASS
Quartz 250-500 um | 37.66° | YES | 5.9 | 2.13° | PASS
Quartz >500 um | 36.53° | YES | 5.7 | 1.79° | PASS
Glass Beads - 1 Cup | 22.23° | YES | 4.1 | 0.10° | PASS
Glass Beads - 2 Cups | 27.46° | YES | 6.0 | 0.03° | PASS