Vortex cloud flow modelling of cylinders in orbital motion at low Reynolds numbers and comparisons with some published grid-based CFD predictions

Lewis, R. Ivan (2007) Vortex cloud flow modelling of cylinders in orbital motion at low Reynolds numbers and comparisons with some published grid-based CFD predictions. JOURNAL OF COMPUTATIONAL AND APPLIED MECHANICS, 8 (2). pp. 149-161. ISSN 1586-2070

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Abstract

Cylinders in elliptical orbital motion at low Reynolds numbers (Re) have been fairly extensively researched by grid-based Computational Fluid Dynamic (CFD) methods, revealing discontinuous behaviour of the root mean square (rms) lift coefficient from positive to negative values for low transverse amplitudes and orbital periodicity close to the Strouhal number for the fixed cylinder. Following published grid-based analyses, this paper studies a few flows for Re values of 130, 160 and 180 with orbital periodicity set at 85 % of the Strouhal frequency. The orbital amplitude in the mainstream flow direction Ax is fixed at 0.3 of the cylinder diameter, while the transverse amplitude is varied over the range 0 < Ay < 0.3. A brief outline of the vortex cloud analysis is first given followed by a presentation of predicted lift and drag coefficients for this range of flow conditions plus selected flow patterns for regions of main interest. While the detailed predicted CLmean results are not identical to the published grid-based analysis, similar proneness to this switching phenomenon is found to occur. The flow mechanism underlying this is shown to be that of vortex pair formation in the downstream wake and is illustrated by predicted vortex-cloud patterns.

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