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Streamline and turbulent flow
Intermediate
Smooth layers versus chaotic eddies.
In streamline (laminar) flow, layers slide smoothly along fixed paths; in turbulent flow velocity fluctuates chaotically and mixes the fluid. High speed or large size leads to turbulence.
Smoke from a candle goes up smoothly then breaks into eddies.
Turbulence increases drag.
In more detail
In streamline flow, fluid particles follow smooth paths without mixing. Turbulent flow is irregular and chaotic, with eddies and rapid mixing.
Real-world uses
- Aircraft wings aim for smooth flow to reduce drag.
- Mixing of pollutants in rivers depends on turbulence.
- A smoke trail from a candle rises smoothly at first and then breaks into swirling eddies, showing the change from laminar to turbulent flow.
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Frequently asked questions
What causes turbulence?
High speed, large size and low viscosity, which together give a high Reynolds number.
Is smooth flow always better?
For drag reduction yes, but for mixing, turbulence is often desirable.
What makes flow turbulent?
High speed, large size and low viscosity make flow break into eddies, which is measured by the Reynolds number.
Related topics in Fluids & Elasticity
Stability of floating bodies · Hydrometer · Fluid dynamics · Equation of continuity · Bernoulli's principle · Applications of Bernoulli