Flow over curved backward-facing step

Semi-confined flows

Underlying Flow Regime 3-31

Description

Introduction

This test case focuses on the incipient separation occuring on a curved backward facing step, illustrated by visualization of the LES results in Fig. \ref{fig:baseline_vorticity}. The results were obtained using highly-resoved LES. The primary focus of this case is on the details of the separation process and the properties of the separated region, including reattachment. Results are reported and analysed in two journal papers \cite{lardeau2011interaction,bentaleb2012large} and only the main elements of those papers, pertinent to use and analyse the data provided, are reported here. This geometry shows particular features of separation from gently-curved surfaces: the separation process is highly unsteady in time and space; turbulence is highly non-local in character; the mean reverse-flow region is thin and highly elongated; no part of the flow is reversed at all times; the level of production is extremely high following separation, resulting in massive departures from turbulence-energy equilibrium, very high anisotropy and a trend towards one-component turbulence in the separated shear layer. The LES results constitute a valuable data set for benchmarking model solutions and investigating statistical turbulence-closure proposals.

Review of UFR studies and choice of test case

Provide a brief review of past studies of this UFR which have included test case comparisons of experimental measurements with CFD results. Identify your chosen study (or studies) on which the document will focus. State the test-case underlying the study and briefly explain how well this represents the UFR? Give reasons for this choice (e.g a well constructed test case, a recognised international comparison exercise, accurate measurements, good quality control, a rich variety of turbulence or physical models assessed etc.) . If possible, the study should be taken from established data bases. Indicate whether of not the experiments have been designed for the purpose of CFD validation (desirable but not mandatory)?

Contributed by: Sylvain Lardeau — CD-adapco