Turbulent Energy Cascade

GOY shell model of turbulence — energy cascades from large scales to small, revealing Kolmogorov's k⁻⁵/³ spectrum.

Shell Model (GOY)

GOY coupling:
u̇ₙ = ik_n(u*_{n+1}u*_{n+2}
− δu*_{n-1}u*_{n+1}/2
− (1-δ)u*_{n-1}u*_{n-2}/4)
− νk²_n u_n + F δ_{n,n₀}
Total E: 0.00
Dissipation ε: 0.00
K41 slope: -1.67
Inertial shells: 0
Re_λ ≈ 0
Kolmogorov 1941 (K41): Energy injected at large scales (low k) cascades to small scales through an inertial range where E(k) = C_K ε^{2/3} k^{−5/3} (Kolmogorov spectrum, shown as dashed line). Dissipation occurs at Kolmogorov scale η=(ν³/ε)^{1/4}. GOY/Sabra shell model: Simplified 1D model retaining energy/helicity conservation. Shell n has wavenumber k_n = k₀·2ⁿ. Intermittency: Real turbulence deviates slightly — anomalous scaling exponents ζ_p ≠ p/3 for structure functions. She-Leveque (1994) prediction: ζ_p = p/9 + 2[1−(2/3)^{p/3}].