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Time evolution of the eddy viscosity in two-dimensional navier-stokes flow
1Departamento de Matematica Aplicada, CMAUP, Universidade do Porto, Rua das Taipas 135, 4050 Porto, Portugal.
Summary
Navier-Stokes dynamics stabilizes negative eddy viscosity effects in 2D incompressible flows. Direct numerical simulations show initial negative eddy viscosity transitions to positive values before viscous relaxation.
Area of Science:
- Fluid dynamics
- Computational physics
Background:
- Eddy viscosity is a key concept in turbulence modeling.
- Understanding its time evolution is crucial for accurate simulations.
- Negative eddy viscosity presents a theoretical challenge.
Purpose of the Study:
- Analyze the time evolution of eddy viscosity in 2D incompressible Navier-Stokes flow.
- Investigate the impact of initial negative eddy viscosity.
- Determine if Navier-Stokes dynamics can stabilize negative eddy viscosity.
Main Methods:
- Direct numerical simulation (DNS) was employed.
- Focus on unforced 2D incompressible Navier-Stokes equations.
- Initial conditions featured isotropic and negative eddy viscosity.
Main Results:
- Demonstrated stabilization of negative eddy viscosity effects.
- Observed monotonic transition from negative to positive eddy viscosity.
- This transition occurs prior to viscous term relaxation.
Conclusions:
- Navier-Stokes dynamics inherently stabilizes negative eddy viscosity.
- The findings challenge previous assumptions about negative viscosity.
- Provides insights into turbulence behavior and modeling.