Lecture on Turbulent and Laminar Flow

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• Sponsored by Cottonelle flushable wipes.

Introduction

• Chris Hadfield's involvement.
• Mention of Destin from Smarter Every Day's fascination with laminar flow.

Fluid Flow Types

Laminar Flow

• Particles move in parallel layers.
• Well-organized and predictable.
• Occurs at low flow rates.
• Example: Dye in a pipe remains in a steady stream at low speeds.

Turbulent Flow

• Unpredictable and chaotic.
• Sensitive to initial conditions.
• Described statistically due to complexity.
• Navier-Stokes equations govern turbulent flow but are hard to solve.
• Turbulent flow is common in daily life.

Characteristics of Turbulent Flow

• Unpredictability: Sensitively dependent on initial conditions.
• Chaotic Nature: Makes exact predictions difficult.
• Diffusiveness: Helps in mixing heat, momentum, etc.
• Dissipative: Requires a constant energy source.

Examples of Turbulent Flow

• Air in a room: ranging from micrometer to meters in scale.
• Cosmic examples: Sun's plasma, Jupiter's atmosphere, Orion Nebula.
• Earthly examples: Lungs, blood flow, weather systems.

Reynolds Number

• Dimensionless quantity determining flow type.
• High Reynolds numbers indicate turbulent flow.
• Dependent on velocity, fluid characteristics, and viscosity.

Boundary Layer

• Area near a surface where fluid velocity changes from zero to free stream.
• Laminar Boundary Layer: Less drag due to less interaction.
• Turbulent Boundary Layer: More drag, energy transfer.
• Induced by rough surfaces or design in aviation and sports.

Applications

Aviation

• Turbulent boundary layers prevent stall.
• Vortex generators on wings to maintain lift.

Golf Balls

• Dimples create turbulent boundary layers reducing drag.

Research and Adaptations

• Vortex shedding and energy harnessing.
• Fish using turbulence for efficient swimming.

Conclusion

• Turbulence is prevalent and essential in numerous applications.
• Offers deeper, richer dynamics compared to laminar flow.
• Turbulent flow's unpredictability adds complexity and interest.

Final Thoughts

• Acknowledgment of the importance and beauty of both laminar and turbulent flows.

Sponsored Experiment

• Comparison of flushability: baby wipes, paper towel, Cottonelle flushable wipes.
• Results show flushable wipes break down faster, reducing the risk of sewer clogs.

Note: The presentation also contained a segment filmed before the COVID outbreak.