The Ninth International Symposium on Turbulence and Shear Flow Phenomena (TSFP-9; http://tsfp9.org/index.html) was held in Melbourne, Australia, from 30 June to 3 July 2015, hosted by the University of Melbourne. It was part of the series of biennial TSFP Symposia, which are a principal venue for reporting and disseminating recent and ongoing research on turbulence and shear flow phenomena. Its Organising Committee consisted of Stavros Tavoularis (University of Ottawa, Chair), Rainer Friedrich (Technische Universität München), Arne Johansson (Royal Institute of Technology – KTH), Lex Smits (Princeton University), Hyung Jin Sung (Korea Advanced Institute of Science and Technology – KAIST) and Ivan Marusic (University of Melbourne – Chair of the Local Organising Committee).
TSFP-9 participants reported new discoveries and developments on turbulence and shear flow phenomena using direct numerical simulations (DNS), large eddy simulations (LES), turbulence closures and experimental approaches. Particular emphasis was given to the following topics: instability and transition to turbulence; advanced techniques for turbulence measurements; modelling and simulation of complex flows; turbulence and heat/mass transfer control; turbulence in reacting and multiphase systems; plasma and MHD turbulence; noise generation and fluid-structure interaction; biological, biomedical and clinical flows; and environmental, geophysical and compressible turbulence. The TSFP-9 program included 5 invited lectures, 180 oral presentations and 51 poster presentations. All contributed presentations underwent review by at least three expert reviewers as well as the Organising Committee. The full Proceedings of TSFP-9 and those of all previous TSFP may be accessed at http://www.tsfp-conference.org/proceedings.html.
A select group of TSFP-9 papers were invited for inclusion in this special issue. The submissions were expanded and revised versions of the papers in the TSFP-9 Proceedings and went through a full review process by the Journal of Turbulence, with the accepted ones appearing in different issues of the journal according to JofT policies. The present special issue is a collation of nine papers originating in TSFP-9 but enriched with new material and expanded in content and scope. These papers cover diverse fundamental and applied topics on turbulence and shear flow phenomena, including the following: an alternative to subgrid-scale modelling in LES (Cadieux and Domaradzki); measurements of scalar dispersion by coherent structures in a shear flow (Vanderwel and Tavoularis); DNS of unstably stratified turbulence, with emphasis on the anisotropy of its structure (Gréa, Burlot, Godeferd, Griffond, Soulard and Cambon); DNS of secondary flows over surfaces with spanwise variations of slip (Stroh, Hasegawa, Kriegseis and Frohnapfel); a numerical analysis of early stages of transition to turbulence in plane Poiseuille flow (Zammert and Eckhardt); LES of turbulent boundary layers with localised blowing (Kametani, Fukagata, Örlü and Schlatter); tomographic PIV studies of swirling jets (Markovich, Dulin, Abdurakipov, Kozinkin, Tokarev and Hanjalić); LES of the effects of in-nozzle flow on a turbulent spray jet (Hélie, Khan and Gorokhovski); and an analytical comparative study of skin friction over compliant walls with different material properties (Luhar, Sharma and McKeon).