Abstract:
Harnessing atmospheric buoyancy offers a promising avenue for generating carbon-neutral electricity and is fuelling a growing interest in renewable energy. This study focuses on the numerical investigation of atmospheric buoyancy vortices, examining their behaviour and their relevance to the Atmospheric Vortex Engine (AVE) concept.
A laboratory and an atmospheric-scale model are examined using Reynolds–Averaged
Navier–Stokes (RANS) and Large Eddy Simulation (LES) methods. The numerical
model shows good agreement with experimental and analytical data at the laboratory
scale. The laboratory scale numerical model demonstrates consistent trends
with experimental observations and aligns well with analytical models published in
the literature.
Computational efficiency is achieved in the atmospheric scale model by incorporating
body forces to represent the vanes and turbine. The atmospheric-scale study
reveals the presence of vortex wandering, particularly further away from the ground
and the heat source.
The turbine model investigated the effects of changing the torque coefficient (Ct )
on the vortex dynamics. For torque coefficients Ct ≤ 1.2 a negative vertical velocity
occurred, which characterises the occurrence of a vortex breakdown. The study also
investigated the impact of design parameters, such as increasing turbine height and
heat source temperature. Increasing the turbine height by a factor of two led to a
roughly 50% increase in torque while raising the heat source temperature resulted in
an ≈ 148% increase.
Cross wind conditions of 0.5 m/s, 1 m/s, and 2 m/s were introduced and caused
the vortex core to tilt and displacement away from the heat source centre. Pressure
variations generated high-pressure regions upstream of the vanes and low-pressure
regions downstream of the vanes.
In conclusion, this study provides valuable insights into atmospheric buoyancy
vortices. The numerical model accurately captures vortex behaviours, including vortex
breakdown and wandering. The proposed turbine model offers insights into the
impact of turbines on vortex structure. It is hoped that these findings will contribute
to the development of AVE technology and numerical modelling in atmospheric science.