Three-dimensional instability in flow over a backward-facing step

Dwight Barkley

doi:10.1017/S002211200200232X

Three-dimensional instability in flow over a backward-facing step

2002-12-13

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DOI：10.1017/S002211200200232X

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Abstract

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Results are reported from a three-dimensional computational stability analysis of flow over a backward-facing step with an expansion ratio (outlet to inlet height) of 2 at Reynolds numbers between 450 and 1050. The analysis shows that the first absolute linear instability of the steady two-dimensional flow is a steady three-dimensional bifurcation at a critical Reynolds number of 748. The critical eigenmode is localized to the primary separation bubble and has a flat roll structure with a spanwise wavelength of 6.9 step heights. The system is further shown to be absolutely stable to two-dimensional perturbations up to a Reynolds number of 1500. Stability spectra and visualizations of the global modes of the system are presented for representative Reynolds numbers.

Keywords:

NAVIER-STOKES EQUATIONS

DIRECT NUMERICAL-SIMULATION

2-DIMENSIONAL FLOW

LAMINAR-FLOW

SEPARATION-BUBBLES

STABILITY ANALYSIS

COUETTE-FLOW

SHEAR-FLOW

MECHANISMS

TRANSITION

Three-dimensional instability in flow over a backward-facing step

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