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Surface switching statistics of rotating fluid: Disk-rim gap effects.
1Laboratory for Flow Control, Hokkaido University, N13W8, Sapporo 060-8628, Japan.
Physical Review. E
|May 17, 2017
Summary
Internal noise significantly alters fluid free surface dynamics in rotating vessels. A small gap change causes frequent shape switching between turbulent and laminar states, shifting critical flow conditions.
Area of Science:
- Fluid dynamics
- Nonlinear dynamics
- Surface physics
Background:
- The free surface of fluids in rotating cylindrical vessels exhibits complex, irregular shape switching.
- Internal noise sources can influence the stability and dynamics of fluid interfaces.
Purpose of the Study:
- To investigate the impact of internal noise on the irregular shape switching of a fluid's free surface in a rotating cylindrical vessel.
- To analyze the physical mechanisms behind noise-induced transitions between different flow states.
Main Methods:
- Experimental observation of fluid free surface behavior under controlled rotation speeds.
- Mathematical modeling based on surface height fluctuation measurements, incorporating a noise term.
- Analysis of flow characteristics within the disk-rim gap as a noise source.
Main Results:
- A slight increase in the disk-rim gap ( < 3% of disk radius) induced significant changes in surface dynamics.
- Frequent surface descending events were observed, connecting nonaxisymmetric (turbulent) and axisymmetric (laminar) shapes.
- A shift in the critical Reynolds number, defining characteristic flow states, was detected.
Conclusions:
- The disk-rim gap acts as a crucial noise source, influencing the fluid free surface's switching behavior.
- Internal noise plays a key role in the transitions between laminar and turbulent flow states in this system.
- Understanding noise-induced dynamics is essential for predicting and controlling fluid behavior in rotating systems.
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