New developments in understanding interfacial processes in turbulent flows

Abstract

Interfaces, across which fluid and flow properties change significantly, are a ubiquitous feature of most turbulent flows and are present within jets, plumes, homogeneous turbulence, oceans and planetary atmospheres. Even when the interfaces occupy a small volume fraction of the entire flow, they largely control processes such as entrainment and dissipation and can act as barriers to transport. This Theme Issue brings together some of the leading recent developments on interfaces in turbulence, drawing in many methodologies, such as experiments, direct number simulations, inverse methods and analytical modelling.

Kelvin‐Helmholtz Billow Interactions and Instabilities in the Mesosphere Over the Andes Lidar Observatory: 1. Observations

“…Despite its importance throughout the atmosphere and in other fluids, a quantitative understanding of turbulence and its generation has eluded scientists for many years (Eames & Flor, 2011). While turbulence theory has advanced greatly since the 1941 work of Kolmogorov translated in Kolmogorov et al (1991), and idealized geophysical sources are now well known (Thorpe, 1987(Thorpe, , 2005Nappo, 2013;Fritts et al, 2017), the character and evolutions of instabilities accounting for laminar to turbulent flow transitions in more general geophysical flows are diverse, and largely without significant quantitative observational guidance.…”

Tracking normal fluid flow in He II with unsupervised machine learning

“…1 The demonstration was performed in a quiescent environment (i.e., one with very little fluid motion) of an enclosed glass bulb. Acquisition of such images taken during flow around objects is expected to provide data to test and validate theoretical 2 and computer models that describe the development, intensity, and internal structure of turbulent flow beyond simple systems (e.g., flow over a smooth flat plate). 3 Especially important are data with good spatial resolution of three dimensional (3D) velocity vector fields acquired simultaneously over a field of view with size well in excess of the object using a technique that minimizes perturbations to flow.…”

Quantum Turbulent Structure in Light

“…Despite far predating nearly all other open problems in both mathematics and physics, a complete theory of fluid turbulence remains elusive, and represents one of the greatest open problems of either discipline [1]. Though the problem of turbulence in classical fluids was treated with modern sophistication by Kolmogorov in the decade before [2,3], it was not until 1955 that Feynman, who called turbulence the most important unsolved problem of classical physics [4], gave the problem a truly modern flavor by merging it with quantum mechanics [5].…”