Vibration Parameters
Particles
State
ρ packing: 0.00
Taps: 0
Phase: —
Chicago experiment (Knight et al. 1995) — packing fraction evolution under vertical vibration
When a granular column is subjected to vertical taps, the packing fraction ρ evolves logarithmically: ρ(t) = ρ∞ − Δρ / (1 + B·ln(1 + t/τ)) — the Chicago experiment (Knight 1995).
At low Γ (reversible regime), compaction is slow and memory-free. Above a threshold Γ*, behaviour becomes irreversible — the system explores new metastable states and compacts faster. This mirrors the "Kovacs effect" in glasses.
The boundary between reversible and irreversible branches (Nowak et al. 1998) shows hysteresis: raising then lowering Γ traces a different path, a signature of history-dependence in disordered systems.