On the Structure of General Weak Solutions of 3D Decaying Turbulence
Min Chul Lee
TL;DR
The paper addresses the temporal structure of general weak solutions to the 3D Navier–Stokes equations on the torus with no forcing, focusing on decaying turbulence. It introduces a simple criterion: a weak solution with monotone-decreasing kinetic energy in time satisfies the strong energy inequality, enabling a comprehensive time-behavior analysis without extra regularity assumptions. The main results establish an equivalence between monotone-energy variants and Leray–Hopf solutions via the differential energy equality, and then develop an order-theoretic framework (partial order, chains, Zorn's lemma) to classify energy evolution and identify potential singular times. This approach yields a structural understanding of energy decay and non-smooth evolution in 3D turbulence, offering a pathway to analyze whether and when singularities may occur in weak solutions.
Abstract
It is shown that a weak solution with monotone-decreasing kinetic energy satisfies the strong energy inequality. Using this criterion, we analyze the behavior with respect to time for all weak solutions without any further assumption on regularity.
