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ISSN Online: 2379-1748

ISBN Flash Drive: 978-1-56700-469-4

ISBN Online: 978-1-56700-470-0

Second Thermal and Fluids Engineering Conference
April, 2-5, 2017, Las Vegas, NV, USA

DRAG REDUCTION IN TURBULENT CHANNEL FLOW WITH TWO-TIERED SUPERHYDROPHOBIC WALLS

Get access (open in a dialog) pages 1429-1442
DOI: 10.1615/TFEC2017.bev.018117

Abstract

Drag reduction measurements are made in a channel with micro-structured superhydrophobic walls in combination with larger scale turbulence reducing riblets. Pressure drop and PIV measurements across surfaces exhibiting superhydrophobicity, riblets, and hybrid surfaces with both drag reducing mechanisms are presented. Micro-ribs etched in silicon and coated with Teflon provide superhydrophobicity. Larger scale riblets are deposited every 200 microns and extend nearly 100 microns above the ribs effectively dampening spanwise turbulence. PIV measurements are used to explore velocity and shear stress profiles where one channel wall is composed of a structured test surface and the other is smooth. These profiles allow estimation of friction factors and overall drag reduction. Reynolds numbers ranging from 3.5 × 103 to 2.3 × 104 are explored. A modest drag reduction was observed for the riblet only surfaces but the hybrid surfaces composed of both micro-ribs and riblets show the greatest drag reduction.