Abstract
The effect of geometry on the flow around a cylinder in crossflow is investigated in this study. Three different stepped-diameter circular cylinders (SDCC s) with varying step heights are used. Extensive flow visualization using the oil-lampblack and smoke-wire techniques and near wake velocity measurements using a hotwire anemometer reveal complex secondary flows on and around the SDCC. Six vortices are observed in the horseshoe vortex system near the cylinder-endwall junction and six additional vortices are found in the step-induced vortex system on the step surface. Based on these experimental results, new secondary flow models are proposed. The step-induced vortices separate from the step surface at both sides and move toward the endwall, washing down the sides of the top/bottom larger diameter cylinders and interact with the separated shear layer and horseshoe vortices. In this process, they modify the near wake flow significantly: they produce an increase in velocity near the endwall region (below the step) and a decrease in velocity near the mid-span region, even altering the oscillatory behavior of the wake.
Original language | English (US) |
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Pages (from-to) | 36-47 |
Number of pages | 12 |
Journal | Applied Thermal Engineering |
Volume | 40 |
DOIs | |
State | Published - Jul 2012 |
Bibliographical note
Copyright:Copyright 2012 Elsevier B.V., All rights reserved.
Keywords
- Flow visualization
- Horseshoe vortex
- Secondary flow
- Stepped-diameter circular cylinder
- Uniform-diameter circular cylinder