Experimental lateral wall boundary layer behavior of a differentially rotating split-cylinder flow

Area of Science:

• Fluid dynamics
• Experimental physics
• Boundary layer theory

Background:

• Investigating fluid behavior in rotating systems is crucial for understanding complex phenomena.
• The cylindrical wall boundary layer is a fundamental area of study in fluid mechanics.

Purpose of the Study:

• To experimentally analyze the fluid dynamics within a closed cylinder split at the equator.
• To investigate the effects of differential rotation on the boundary layer.
• To compare experimental findings with theoretical and numerical models.

Main Methods:

• Experimental setup involving a closed cylinder divided into two rotating halves.
• Controlled variation of rotation frequencies between the cylinder halves.
• Observation and analysis of secondary flow, boundary layer structure, and wave phenomena.

Main Results:

• Solid-body rotation observed under exact corotation.
• A secondary flow restricted to the boundary layer generated by differential rotation.
• Identification of a "sandwich" structure characteristic of a Stewartson boundary layer.
• Observation of time-dependent waves near the cylindrical wall.
• Discovery of a global recirculation mode linked to symmetry breaking and potential precessing cylinder behavior.

Conclusions:

• Differential rotation in split cylinders generates a distinct secondary boundary layer flow.
• The experimental results align with theoretical models of Stewartson boundary layers.
• Observed wave dynamics and recirculation modes offer insights into complex fluid behaviors in rotating systems.