Under pressure: turbulent plumes in a uniform crossflow
File(s)
Accepted version
Author(s)
Jordan, Owen H
Rooney, Gabriel G
Devenish, Benjamin J
van Reeuwijk, Maarten
Type
Journal Article
Abstract
Direct numerical simulation is used to investigate the integral behaviour of buoyant plumes
subjected to a uniform crossflow that are infinitely lazy at the source. Neither a plume
trajectory defined by the centre of mass of the plume zc nor a trajectory defined by the
central streamline zU is aligned with the average streamlines inside the plume. Both zc
and zU are shown to correlate with field lines of the total buoyancy flux, which implies
that a model for the vertical turbulent buoyancy flux is required to faithfully predict the
plume angle. A study of the volume conservation equation shows that entrainment due to
incorporation of ambient fluid with non-zero velocity due to the increase in the surface
area (the Leibniz term) is the dominant entrainment mechanism in strong crossflows. The
data indicate that pressure differences between the top and bottom of the plume play a
leading role in the evolution of the horizontal and vertical momentum balances and are
crucial for appropriately modelling plume rise. By direct parameterisation of the vertical
buoyancy flux, the entrainment and the pressure, an integral plume model is developed
which is in good agreement with the simulations for sufficiently strong crossflow. A
perturbation expansion shows that the current model is an intermediate-range model valid
for downstream distances up to 100b–1000b, where b is the buoyancy length scale based
on the flow speed and plume buoyancy flux.
subjected to a uniform crossflow that are infinitely lazy at the source. Neither a plume
trajectory defined by the centre of mass of the plume zc nor a trajectory defined by the
central streamline zU is aligned with the average streamlines inside the plume. Both zc
and zU are shown to correlate with field lines of the total buoyancy flux, which implies
that a model for the vertical turbulent buoyancy flux is required to faithfully predict the
plume angle. A study of the volume conservation equation shows that entrainment due to
incorporation of ambient fluid with non-zero velocity due to the increase in the surface
area (the Leibniz term) is the dominant entrainment mechanism in strong crossflows. The
data indicate that pressure differences between the top and bottom of the plume play a
leading role in the evolution of the horizontal and vertical momentum balances and are
crucial for appropriately modelling plume rise. By direct parameterisation of the vertical
buoyancy flux, the entrainment and the pressure, an integral plume model is developed
which is in good agreement with the simulations for sufficiently strong crossflow. A
perturbation expansion shows that the current model is an intermediate-range model valid
for downstream distances up to 100b–1000b, where b is the buoyancy length scale based
on the flow speed and plume buoyancy flux.
Date Issued
2021-12-15
Date Acceptance
2021-11-04
Citation
Journal of Fluid Mechanics, 2021, 932
ISSN
0022-1120
Publisher
Cambridge University Press
Journal / Book Title
Journal of Fluid Mechanics
Volume
932
Copyright Statement
© The Author(s), 2021. Published by Cambridge University Press
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000730257000001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
plumes/thermals
turbulent mixing
LARGE-EDDY SIMULATIONS
BUOYANT PLUMES
ROUND JET
ENTRAINMENT
CONVECTION
LAMINAR
STEADY
MODELS
WIND
Publication Status
Published
Article Number
PII S0022112021010016