On how walls shape dissipation intermittency

TL;DR

This paper derives and verifies scaling laws for energy dissipation intermittency in wall-bounded turbulence, revealing boundary effects' influence and the transition from intermittent to bounded dissipation near walls.

Contribution

It introduces two fundamental Reynolds number scaling expressions for dissipation moments in wall-bounded flows, supported by direct numerical simulations.

Findings

Outer region dissipation follows universal power laws.

Near-wall dissipation follows a bounded defect law.

At high Reynolds numbers, dissipation vanishes away from walls.

Abstract

Intermittency of energy dissipation has long been studied via high-order moments in homogeneous and isotropic turbulence, but not much where the boundary effects are explicitly included. Here, we derive two fundamental Reynolds number scaling expressions for dissipation moments in wall-bounded flows -- one in the outer region where the boundary effects are weak and the other close to the walls where those effects are strong -- and support these expressions by direct numerical simulations. Dissipation moments in the outer region follow universal power laws with exponents linked to anomalous scaling of velocity structure functions. In contrast, moments near the wall follow a bounded defect law, leading to a finite asymptotic limit without intermittency. For very large Reynolds numbers, the outer proposal predicts vanishing dissipation compared to that on the wall, highlighting the need for solid boundaries in generating Onsager-type singularities.