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Updated: May 13, 2026
08:01
The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Effective diffusivity of passive scalars in rotating turbulence
P Rodriguez Imazio1, P D Mininni
1Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Cuidad Universitaria, Buenos Aires 1428, Argentina.
Summary
Rotation significantly reduces scalar diffusion perpendicular to the rotation axis in turbulent flows. This effect is predictable using mixing length arguments, except at low Schmidt numbers where molecular diffusion dominates.
Area of Science:
- Fluid Dynamics
- Turbulence
- Transport Phenomena
Background:
- Turbulent rotating flows are prevalent in geophysical and astrophysical systems.
- Understanding passive scalar transport is crucial for modeling phenomena like pollutant dispersion and heat transfer.
- The influence of rotation on turbulent diffusion coefficients requires detailed investigation.
Purpose of the Study:
- To compute turbulent transport coefficients for passive scalars in rotating flows.
- To investigate the effects of Rossby and Schmidt numbers on effective diffusion.
- To analyze the impact of rotation on scalar diffusivity parallel and perpendicular to the rotation axis.
Main Methods:
- Direct numerical simulations (DNS) were employed to model turbulent rotating flows.
- Effective diffusion coefficients were calculated by analyzing the time evolution of scalar concentration and flux.
- Parametric studies were conducted by varying Rossby and Schmidt numbers.
Main Results:
- Rotation was found to reduce scalar diffusivity in the direction perpendicular to the rotation axis.
- Effective perpendicular diffusion can be accurately estimated using mixing length arguments.
- Deviations from predictions occur at low Schmidt numbers, indicating increased significance of molecular diffusion.
Conclusions:
- Rotation plays a significant role in anisotropic turbulent scalar transport.
- The findings provide a basis for parameterizing turbulent diffusion in rotating systems.
- Low Schmidt numbers necessitate accounting for molecular diffusion effects in rotating turbulent flows.
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