Engineering the Whirlwind

An analysis of atmospheric buoyancy vortices is made, suggesting they can be usefully analysed as heat engines, converting Convectively Available Potential Energy (CAPE) contained in a rising columnar core, into rotational kinetic energy. The cold reservoir of the heat engine is considered as being located at the point where the coherent vortex core breaks down into a turbulent plume. Vortex coherence at small diameters is found to depend on the suppression of turbulent mixing, arising from hydrodynamic stability and stable radial stratification of density in the vortex core, combined with sufficient lapse-rate divergence. Lapse-rate divergence describes a situation where the vortex core cools more slowly in rising than the surrounding atmosphere does. The height and temperature of the cold-reservoir of the heat-engine driving the vortex, are modelled as resulting from this behaviour. Experiments are reported that measure this suppression of turbulent mixing in laboratory vortices and compare it to predictions, based on published models based on non-dimensional numbers. Estimates of the behaviour of saturated vortices rising in open atmosphere are made, based on those measurements of the suppression of turbulent mixing, to estimate design parameters for a field demonstrator of the concept of a vortex station, which is envisaged as an installation capable of generating a tall artificial buoyancy vortex with high wind-speeds occurring at the ground.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2022

Author dc:creator

• Hawkes, Neil Andrew

Advisors dc:contributor.advisor

• Flay, Richard
• Cater, John

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/64090

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/64090