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Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods
Published on: April 23, 2018
Interacting vortices and spin-up in two-dimensional turbulence
J B Taylor1, Matthias Borchardt, Per Helander
1Radwinter, Wallingford, OX10 9EJ, UK.
Physical Review Letters
|April 28, 2009
Summary
Two-dimensional turbulence in simulations can spontaneously gain angular momentum, a phenomenon termed "spin-up." Statistical models reveal two equilibrium states, one with zero angular momentum and another with non-zero momentum despite zero net vorticity.
Area of Science:
- Fluid dynamics
- Statistical mechanics
- Turbulence theory
Background:
- The phenomenon of "spin-up," the spontaneous acquisition of angular momentum by a turbulent two-dimensional fluid in a rigid container, was observed in simulations.
- Understanding the underlying mechanisms of spin-up is crucial for comprehending complex fluid behaviors.
Purpose of the Study:
- To interpret the "spin-up" phenomenon using statistical models of two-dimensional turbulence.
- To investigate the existence of distinct statistical equilibria in bounded systems with zero net vorticity.
Main Methods:
- Statistical modeling of two-dimensional turbulence.
- Analysis of systems with zero net vorticity in bounded domains.
- Comparison of theoretical predictions with simulation results.
Main Results:
- Two distinct statistical equilibria were identified in bounded systems with zero net vorticity.
- One equilibrium state possesses zero angular momentum, while the other exhibits non-zero angular momentum despite vanishing circulation.
- The probability of these equilibria is highly sensitive to boundary shape and weakly dependent on energy.
Conclusions:
- The "spin-up" phenomenon can be explained by the existence of a statistical equilibrium with non-zero angular momentum.
- Theoretical predictions for angular momentum in the second equilibrium state align well with high Reynolds number simulation findings.
- Boundary geometry plays a critical role in determining the prevalence of different statistical equilibria in turbulent systems.
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