Author(s)

M.W. Collins

Abstract

The concepts of filtering and decomposition as applied to the analysis and modelling of turbulent flows are reviewed, starting from the seminal work of Reynolds. The problems arising from the use of finite spatial or time filters are discussed, and the recent approach based on the concepts of scale-similarity and multi-level filtering are presented. Finally, the possible extension of these ideas to finite time filtering is considered, with a view to developing turbulence models for time-dependent flows; a simple two-dimensional direct simulation of a turbulent free convective flow is used as an example. 1 Introduction Dating from the time of Professor Osborne Reynolds's inspired a

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