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A Numerical Investigation of the Onset of Flow Separation in Round-edge Diverging Tees

[+] Author and Article Information
Foo Kok

Department of Aeronautics and Astronautics University of Southampton, Southampton, SO17 1BJ, UK
f.kok@soton.ac.uk

Roy Myose

Department of Aerospace Engineering Wichita State University, Wichita, Kansas, 67260-0044, USA
roy.myose@wichita.edu

Klaus A. Hoffmann

Department of Aerospace Engineering Wichita State University, Wichita, Kansas, 67260-0044, USA
klaus.hoffmann@wichita.edu

1Corresponding author.

ASME doi:10.1115/1.4038087 History: Received December 12, 2016; Revised September 14, 2017

Abstract

The onset condition of flow separation in diverging tee junctions was investigated numerically. Flow separation and recirculation at the proximal region of a bypass graft can contribute to early-phase graft failure in aortocoronary bypass surgery. Rounding the inlet edge of the branch reduces the likelihood of flow separation and recirculation. The recirculating zone at the upstream end of the branch is fully eliminated when a threshold value of mass flow rate ratio is reached. The corresponding flow characteristics obtained from diverging tees with a diameter ratio ≤ 0.2 and a radius of curvature ≤ 0.25 for Reynolds number ≤ 1817 indicate that an increasing flow rate ratio induces an exponential decrease in the recirculation length. An increase in the diameter ratio and Reynolds number increases both the onset condition of the flow separation and the recirculation length at the upstream end of the branch. However, a decrease in the diameter ratio reduces the onset condition of separation more effectively than the reduction of the radius of curvature at the junction.

Copyright (c) 2017 by ASME
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