Flow visualisation and fundamental aspects of two-dimensional turbulent plumes
type: CreativeWork
description: Understanding the behaviour of turbulent, buoyant plumes is fundamental to modelling a multitude of fluid dynamics problems, for example, indoor airflows. Specifically, this thesis focuses on the turbulent plumes which develop above sources which directly supply buoyancy, but zero momentum, to the fluid. Sources of this type are particularly relevant to modelling the convective flows driven by underfloor heating in rooms. Indeed this form of heating underpinned the interest of the financial sponsor of the research presented herein. Remarkably, whilst the subject of a considerable body of research, this work begins by uncovering the fact that the far-field plume that forms above a heated plate is not well modelled by existing plume theory. The principle means of flow visualisation employed in this research to observe these plumes is shadowgraphy. Perhaps surprisingly, much of the underpinning theory of this method has, to date, been restricted to the case where the flow field of interest is illuminated by collimated light (i.e. illuminating light rays are parallel to each other). This is despite the fact that practical light sources produce a beam of light which diverges. The turbulent convective flow in the vicinity of a uniformly heated semi-infinite plate is investigated experimentally and theoretically. Guided by bespoke experimental observations, governing equations representing the conservation of mass, momentum and energy for this geometry are posed. On making the Boussinesq assumption, it is demonstrated that a so-called `horizontal plume' grows linearly from the plate edge. It is shown that in this near-plate region the mean horizontal velocity and mean buoyancy scale proportionally and inverse proportionally to the cube root of the distance from the plate edge, respectively. A theoretical model for the far-field flow above a uniformly heated two-dimensional plate is developed by considering the merger of two 'horizontal plumes', which grow linearly from bot…
abstract: Understanding the behaviour of turbulent, buoyant plumes is fundamental to modelling a multitude of fluid dynamics problems, for example, indoor airflows. Specifically, this thesis focuses on the turbulent plumes which develop above sources which directly supply buoyancy, but zero momentum, to the fluid. Sources of this type are particularly relevant to modelling the convective flows driven by underfloor heating in rooms. Indeed this form of heating underpinned the interest of the financial sponsor of the research presented herein. Remarkably, whilst the subject of a considerable body of research, this work begins by uncovering the fact that the far-field plume that forms above a heated plate is not well modelled by existing plume theory. The principle means of flow visualisation employed in this research to observe these plumes is shadowgraphy. Perhaps surprisingly, much of the underpinning theory of this method has, to date, been restricted to the case where the flow field of interest is illuminated by collimated light (i.e. illuminating light rays are parallel to each other). This is despite the fact that practical light sources produce a beam of light which diverges. The turbulent convective flow in the vicinity of a uniformly heated semi-infinite plate is investigated experimentally and theoretically. Guided by bespoke experimental observations, governing equations representing the conservation of mass, momentum and energy for this geometry are posed. On making the Boussinesq assumption, it is demonstrated that a so-called `horizontal plume' grows linearly from the plate edge. It is shown that in this near-plate region the mean horizontal velocity and mean buoyancy scale proportionally and inverse proportionally to the cube root of the distance from the plate edge, respectively. A theoretical model for the far-field flow above a uniformly heated two-dimensional plate is developed by considering the merger of two 'horizontal plumes', which grow linearly from bot…
author: Webb, James
language: eng
keywords: Buoyancy, Plume, Shadowgraph, Turbulence
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/67eab12f-9b78-4673-bc1c-17ed61327e05/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2023-09-01
date modified: 2026-07-22T22:24:28Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.106971