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Eighth International Symposium on Turbulence and Shear Flow Phenomena
August, 28-30, 2013, Poitiers, Futuroscope, France

DOI: 10.1615/TSFP8

GENERALIZED PHASE AVERAGING OF EXPERIMENTAL SURFACE-MOUNTED BODY WAKE MEASUREMENTS: 3D COHERENT STRUCTURES & DYNAMICAL MODELS

pages 1-6
DOI: 10.1615/TSFP8.270
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Краткое описание

A six-dimensional model is proposed as a low-order representation of the vortex dynamics in the turbulent wake of a wall-mounted square-cross-section cylinder of height-to-width ratio h/d = 8 with one face normal to the flow at a nominal Reynolds number of 12,000. The wake flow is experimentally investigated for two oncoming turbulent boundary layers of thickness δ/d = 0.72 and 2.6 using simultaneous planar PIV and surface pressure measurements. A novel generalized phase averaging technique is used to determine global harmonic and shift modes, representing the shedding instability and low-frequency behaviour, respectively. The generalized phase average provides a parametrization of the phase as well as the oscillation amplitude and base flow drift. Using this technique, two distinct coherent structure topologies are found, depending on δ/d, distinguished by the topology of the stream/cross-streamwise vortical strands giving rise to half-ring and full-ring structures for the thinner and thicker boundary layer, respectively. A six-dimensional model is derived where the state of the system, f(a(t), ξ(t)), depends on the vector of mode amplitudes, a(t), and a stochastic term, ξ (t), simulating higher order contributions.

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