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On the core flow and turbulent boundary layer in a curved duct

Wilson, Phillip Lawrence; (2003) On the core flow and turbulent boundary layer in a curved duct. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Curved ducts for transporting fluids are commonplace in industry and nature and, whilst many previous studies have concentrated on viscous responses to curvature, there are configurations and/or occasions when the fluid flow is sufficiently rapid that an inviscid approximation is more appropriate. One such occasion is the rapid flow of compressed air through an ejector in a food-sorting machine, which occurs over a typical timescale of 3 milliseconds. The particulars of the current project are connected with the interests of a manufacturer of food-sorting machines, and consequently variations around a specific geometry are studied in this thesis. Using asymptotic analysis and computational techniques, the thesis first studies the steady inviscid response of the flow to the curvature of the duct. Part I concentrates on the core-flow response to the curvature, extending a recent study to include compressibility. Bulk properties of the flow are derived analytically, along with far-downstream predictions of the flow behaviour and the response close to sharp corners of the cross-section. These results are supported by weakly and fully non-linear computational solutions of the steady three-dimensional Euler equations. Part II then studies the growth and development of the turbulent boundary layer in a curved duct. It is observed that there is an apparent lack of experimental data for the level of curvature specified by the industrial application. Entry region analysis suggests the turbulent boundary layer velocities split into a component matching the core flow and a turbulent component. Solutions are found for the turbulent components in the entry region. Three downstream regimes of the major parameters are also identified and described. One, the quasi-straight regime, is studied in detail numerically and comparisons with experiments are made. Increasing curvature effects are discussed by means of the other two regimes.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: On the core flow and turbulent boundary layer in a curved duct
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Applied sciences; Turbulent flows
URI: https://discovery.ucl.ac.uk/id/eprint/10102399
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