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Dual Theory of Decaying Turbulence. 2. Numerical Simulation and Continuum Limit
Version 1
: Received: 16 December 2023 / Approved: 18 December 2023 / Online: 19 December 2023 (09:40:22 CET)
Version 2 : Received: 19 December 2023 / Approved: 20 December 2023 / Online: 20 December 2023 (16:43:56 CET)
Version 3 : Received: 23 December 2023 / Approved: 25 December 2023 / Online: 26 December 2023 (10:00:43 CET)
Version 4 : Received: 26 December 2023 / Approved: 26 December 2023 / Online: 27 December 2023 (09:38:03 CET)
Version 5 : Received: 27 December 2023 / Approved: 27 December 2023 / Online: 27 December 2023 (12:38:44 CET)
Version 2 : Received: 19 December 2023 / Approved: 20 December 2023 / Online: 20 December 2023 (16:43:56 CET)
Version 3 : Received: 23 December 2023 / Approved: 25 December 2023 / Online: 26 December 2023 (10:00:43 CET)
Version 4 : Received: 26 December 2023 / Approved: 26 December 2023 / Online: 27 December 2023 (09:38:03 CET)
Version 5 : Received: 27 December 2023 / Approved: 27 December 2023 / Online: 27 December 2023 (12:38:44 CET)
How to cite: Migdal, A. Dual Theory of Decaying Turbulence. 2. Numerical Simulation and Continuum Limit. Preprints 2023, 2023121357. https://doi.org/10.20944/preprints202312.1357.v4 Migdal, A. Dual Theory of Decaying Turbulence. 2. Numerical Simulation and Continuum Limit. Preprints 2023, 2023121357. https://doi.org/10.20944/preprints202312.1357.v4
Abstract
This is the second paper in a cycle investigating the exact solution of loop equations in decaying turbulence. We perform numerical simulations of the Euler ensemble, suggested in the previous work, as a solution to the loop equations. We designed novel algorithms for simulation, which take a small amount of computer RAM so that only the CPU time grows linearly with the size of the system and its statistics. This algorithm allows us to simulate systems with billions of discontinuity points on our fractal curve, dual to the decaying turbulence. For the vorticity correlation function, we obtain \textbf{quantum fractal laws} with regime changes between universal discrete values of indexes. The traditional description of turbulence with fractal or multifractal scaling laws does not apply here. The measured conditional probabilities of fluctuating variables are smooth functions of the logarithm of scale, with statistical errors being negligible at our large number of random samples $T = 167,772,160$ with $N = 200,000,000$ points on a fractal curve. The quantum jumps arise from the analytical distribution of scaling variable $X = \frac{\cot^2(\pi p/q)}{q^2}$ where $\frac{p}{q}$ is a random fraction. This distribution is related to the totient summatory function and is a discontinuous function of $X$. In particular, the energy spectrum is a devil's staircase with tilted uneven steps with slopes between $-1$ and $-2.03$. The logarithmic derivative of energy decay $n(t)$ as a function of time is jumping down the stairs of universal levels between $1.50$ and $1.53$. The quantitative verification of this quantization would require more precise experimental data.
Keywords
turbulence; fractal; anomalous dissipation; fixed point; velocity circulation; numerical simulations; GPU; loop equations
Subject
Physical Sciences, Fluids and Plasmas Physics
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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