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Zero absolute vorticity: insight from experiments in rotating laminar plane Couette flow
Alexandre Suryadi1, Antonio Segalini1, P Henrik Alfredsson1
1Linné FLOW Centre, KTH Mechanics, SE-100 44 Stockholm, Sweden.
Summary
In rotating channel flows, absolute vorticity approaches zero in the center. This study experimentally demonstrates this phenomenon in laminar Couette flow, explaining its persistence across flow states.
Area of Science:
- Fluid dynamics
- Turbulence research
- Rotational flow phenomena
Background:
- Turbulent channel flows with system rotation exhibit a tendency for absolute vorticity to approach zero in the central region.
- This phenomenon, observed experimentally and numerically, lacks a comprehensive theoretical explanation.
Purpose of the Study:
- To experimentally investigate the behavior of absolute vorticity in rotating channel flows.
- To provide a theoretical explanation for the observed tendency of absolute vorticity to approach zero.
Main Methods:
- Experimental study of three-dimensional laminar structures in plane Couette flow under anticyclonic system rotation.
- Analysis of absolute vorticity and local Richardson number under varying rotation rates.
Main Results:
- Three-dimensional laminar structures under sufficient anticyclonic rotation lead to absolute vorticity approaching zero.
- This condition is equivalent to a local Richardson number near zero, typically indicating stability.
- Kelvin's circulation theorem provides a basis for explaining the constancy of absolute vorticity.
Conclusions:
- The study experimentally validates the zero absolute vorticity phenomenon in rotating channel flows.
- A theoretical framework based on Kelvin's circulation theorem is proposed to explain the observation.
- The findings bridge the understanding between turbulent and laminar rotating flow regimes.
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