Characterizing the Mechanics of Dynamic Flow Separation on Accelerating Bodies
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Authors
Guo, Pengming
Date
Type
thesis
Language
eng
Keyword
Dynamic flow separation , Three-dimensional flow
Alternative Title
Abstract
Flow separation is present in many flows in nature and engineering. Separation is the cause of wake and stall, which increases drag and decreases the performance in many technical applications. However, examples in nature such as fish swimming or bird flight show high efficiency despite or maybe because of the induced separation. Therefore, this thesis strives to understand dynamic flow separation mechanisms in both two-dimensional and three-dimensional flows. The flows around a two-dimensional model (SD7003 foil) and a three-dimensional model (6:1 prolate spheroid) are investigated to gather insights on dynamic flow separation with an increasing degree of complexity. In particular, the influence of roughness, Reynolds number, incidence angle and acceleration magnitude is characterized. Pressure measurements and scanning stereoscopic Particle Image Velocimetry system are applied to reveal the instantaneous pressure distributions and capture the evolution of three-dimensional crossflow separation. First, the two-dimensional flow over an accelerating SD7003 foil is used to study the effects of roughness on dynamic flow separation. A biomimetic shark skin is attached and its effects on the boundary layer development are discussed. The local roughness may trigger an interaction with large-scale structures in the boundary layer for effective control. For three-dimensional flows, the interplay between pressure and crossflow structures on an inclined prolate spheroid is investigated at subcritical Reynolds numbers. The evolution of the dynamic crossflow structures is examined in relation to the acceleration magnitude and incidence angle. A high degree of 3D reorientation of crossflow vorticity is observed at larger incidence angles. The movement of the separation line is related to the vanishing of circumferential pressure gradients. Furthermore, short-lived memory effects of the flow regarding the acceleration are discussed and it is shown that the open crossflow approaches a steady state rather quickly.
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.