Turbulence Scaling Laws from the Grade Equation: Kolmogorov Spectrum and Intermittency from Analyticity
Abstract
We derive the Kolmogorov energy spectrum \(E(k) \sim \varepsilon^{2/3} k^{-5/3}\) and anomalous intermittency corrections to the structure function exponents \(\zeta_p\) from the Grade Equation — a universal structural decomposition theorem for analytic dynamical systems. The derivation proceeds in three steps. First, we decompose the Navier-Stokes nonlinearity into grade-weighted spectral transfers and show that constant energy flux through the grade-2 (bilinear advection) channel, combined with the exponential grade suppression bound \(\|A^{(k)}\| \leq C_0/\rho^k\), recovers the Kolmogorov spectrum with an explicit expression for the Kolmogorov constant in terms of the analyticity radius \(\rho\). Second, we apply the Grade Product Theorem — which states that the product of grade-\(j\) and grade-\(k\) quantities is grade-\((j+k)\) — to the structure functions \(S_p(r) = \langle |\delta_r u|^p \rangle\) and derive the general scaling form \(\zeta_p = p/3 - \tau_G(p)\) where \(\tau_G(p)\) is determined by the spatial distribution of the local analyticity radius \(\rho(\mathbf{x})\). Third, we show that if \(\rho^{-1}(\mathbf{x})\) follows a log-Poisson distribution (as expected for a cascade process concentrated on codimension-2 vortex tubes), the Grade framework recovers the She-Leveque (1994) intermittency formula exactly. The theory makes three falsifiable predictions tested against direct numerical simulation data from the Johns Hopkins Turbulence Database (\(\mathrm{Re}_\lambda \approx 433\), \(1024^3\) grid via SciServer): (i) the local analyticity radius \(\delta(\mathbf{x})\) is measurable from DNS via spectral decay fitting — confirmed with 2,048,383 spatial measurements (\(\mathrm{CV} = 0.39\), R² = 0.98); (ii) the She-Leveque cascade parameter \(\beta\) converges to \(2/3\) with increasing cascade depth — confirmed by multi-scale profile likelihood on both \(-\delta(\mathbf{x})\) and \(\log\varepsilon_\ell(\mathbf{x})\) across five scale–resolution combinations, with \(\beta_{\rm SL} = 0.667\) bracketed between \(\beta_\delta = 0.622\) and \(\beta_\varepsilon = 0.689\) at \(1024^3\), \(\ell = 16\); and (iii) the structure function exponents \(\zeta_p\) match observed anomalous scaling — confirmed against 5 independent published datasets (\(\chi^2\)/dof = 0.05, zero free parameters).