Instabilities of flows due to rotating disks: preface

There are many flows driven by the rotation of one, or more, disks, and this paper is concerned with the instabilities of such flows, and their laminar–turbulent transition. The original, and most studied, rotating-disk flow is the von Kármán swirling flow produced by an infinite rotating disk in an otherwise still fluid. This flow shares many stability characteristics with three-dimensional boundary layers of engineering interest over aerofoils; most notably, the cross-flow instability giving rise to stationary cross-flow vortices. Various basic flows produced by rotating disks, and their stability, are reviewed, and motivations for assembling this special issue dedicated to the instabilities of rotating-disk flows are presented. The papers appearing in this special issue are discussed and related to major research themes in the field, and to one-another.