Extraction of coherent structures using direct numerical simulation in 3D turbulent flows and its effects on chemotaxis
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Description
A numerical study of chemotaxis in 3D turbulence is presented here. Direct Numerical
Simulation were used to calculate the nutrient uptake for both motile and non-motile bacterial
species and by applying the dynamical systems theory the effect of flow topology on the
variability of chemotaxis is analyzed. It is done by injecting a highly localized patch of nutrient
in the turbulent flow, and analyzing the evolution of reaction associated with the observed
high and low stretching regions. The Gaussian nutrient patch is released at different locations
and the corresponding nutrient uptake is obtained. The variable stretching characteristics of
the flow is depicted by Lagrangian Coherent Structures and the roles they play in affecting the
uptake are analyzed. The Lagrangian Coherent Structures are quantified by the Finite Time
Lyapunov Exponents which is a measure of the average stretching experienced by the flow in
finite time. It is found that in high stretching regions, the motile bacteria are attracted to the
nutrient patch very quickly, but also dispersed quickly; whereas in low stretching regions the
bacteria respond slower towards the nutrient patch. However the total uptake is intricately
determined by stretching history. These reaction characteristics are reflected in the several
realizations of simulations. This helps in understanding turbulence intensity and how it affects
the uptake of the nutrient.
Simulation were used to calculate the nutrient uptake for both motile and non-motile bacterial
species and by applying the dynamical systems theory the effect of flow topology on the
variability of chemotaxis is analyzed. It is done by injecting a highly localized patch of nutrient
in the turbulent flow, and analyzing the evolution of reaction associated with the observed
high and low stretching regions. The Gaussian nutrient patch is released at different locations
and the corresponding nutrient uptake is obtained. The variable stretching characteristics of
the flow is depicted by Lagrangian Coherent Structures and the roles they play in affecting the
uptake are analyzed. The Lagrangian Coherent Structures are quantified by the Finite Time
Lyapunov Exponents which is a measure of the average stretching experienced by the flow in
finite time. It is found that in high stretching regions, the motile bacteria are attracted to the
nutrient patch very quickly, but also dispersed quickly; whereas in low stretching regions the
bacteria respond slower towards the nutrient patch. However the total uptake is intricately
determined by stretching history. These reaction characteristics are reflected in the several
realizations of simulations. This helps in understanding turbulence intensity and how it affects
the uptake of the nutrient.