Secondary currents and heat transfer in flow around a cylinder mounted in a narrow channel at subcritical Reynold numbers: LES and PIV

by Mr Egor Palkin (Paul Scherrer Institut)

Thursday 28 Jun 2018, 14:00 → 15:00 Europe/Zurich

OHSA/E13 (Paul Scherrer Institut)

We report on Large-Eddy Simulations (LES) and Particle Image Velocimetry (PIV) of flow around a short cylinder mounted in a narrow infinite plane channel at a series of Reynolds numbers (1000, 2000, 3750, 4000, 10 000) based on the bulk flow velocity and cylinder diameter. Ratio of the cylinder diameter D and channel height H is 2.5, these Re correspond to subcritical regime with laminar separation. While the front of the cylinder is featured by a set of typical horseshoe vortices, in the near wake we discover quasi-periodic low-frequency secondary motion in the form of a pair of counter-rotating vortices. For most of these Re the Karman vortex street remains the dominant pattern, but further downstream from the cylinder motion prevails that transports smaller-scale structure and associated momentum and heat across the narrow channel in the vertical direction are the secondary streamwise vortices, as also previously observed in slot jets. We focus on the impact of secondary flows on heat transfer in front of the cylinder intensified by the horseshoe vortices as well as in the near and far wake further downstream in the form of streamwise vortices. The report mostly follows upcoming THMT (Turbulence Heat and Mass Transfer) conference presentation and focused on LES simulations while uses PIV results for comparison.