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| Departamento de Ingeniería Civil | |
| División de Recursos Hídricos y Medio Ambiente |
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Field, Experimental and numerical study on mixing processes and internal waves in Coriolis affected lakes Principal investigator: Yarko Niño Project funded by the Chilean National Science and Technology Fund, FONDECYT (Project Nº 1080617) Years: 2008-2010 This research focuses on the hydrodynamics
of stratified lakes such as those of the lake district in south central
Chile, some of them large enough as to be affected by rotation of the
Earth. Meteorological forcing of these systems include wind and heat exchange
with the atmosphere. Lake eutrophication is a consequence of high nutrients
input loads. The hydrodynamics is the main agent affecting the distribution
of these nutrients in the lake and therefore, meteorological forcing of
the physics may have a major effect on the biochemistry and, ultimately,
on the water quality of the system. Knowledge and tools to predict such
physical, biochemical and ecological responses are urgently needed, globally
and particularly in Chile, for authorities to be able to manage natural
resources in a sustainable way. This research aims at studying i) Coriolis
effects on wind mixing, taking into account both the interaction between
Ekman layer development and vertical diffusion of turbulent kinetic energy,
and the evolution of internal waves affected by rotation; and ii) Penetrative
convection, taking into account both the atmospheric and lake conditions
that would trigger the phenomenon, and on the amount of mixing induced
by buoyant plumes. Both basic research and the in-situ study of the hydrodynamics
of Lake Villarrica are considered as strategies to advance knowledge and
develop tools for the analysis of stratified lakes, combining field, laboratory
and mathematical/numerical approaches. Field evidence will be gathered
to analyze the effect of circulation and internal waves induced by the
interplay between Coriolis and strong wind, the mixing thus induced, and
the evolution of the hydrodynamics of the system once the wind recedes.
The experimental studies will be carefully designed to reproduce, at a
laboratory scale, different aspects of the hydrodynamics observed in the
lake. The interplay between wind and Coriolis forces will be explored
with the help of a rotating table and a tank equipped with a conveyor
belt (to simulate wind induced shear). Convection generated by surface
cooling will be studied with the help of a stratified tank with a variable
boundary temperature imposed by means of automatic control. Furthermore,
a numerical model capable of simulating the complex response of a stratified
lake to meteorological forcing is being developed. This is a multilayer
model, such that governing equations of flow, and mass and heat transport
are vertically averaged within each layer. A finite-volume numerical scheme
capable of accurately capturing fronts and surface and internal linear
and non-linear waves, considering hydrostatic and non-hydrostatic pressure
terms, is applied.
Selected Publications: Niño, Y., Ojeda, D. and Davies, P. (2008) Numerical modeling of mixing processes in Ekman layer. Second International Symposium on Shallow Flows, Hong-Kong, China.
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