Rayleigh–Bénard convection is a phenomenon that describes how ordered, often hexagonal patterns form in a fluid layer when it is heated from below and cooled from above. This setup creates a temperature gradient, and if the temperature difference is large enough, it causes the fluid to become unstable and start convective motion.
In this process, warmer, less dense fluid rises from the bottom, while cooler, denser fluid sinks from the top. This leads to the formation of convection cells—structured, repeating patterns of fluid circulation.
Key Aspects:
- Occurs when buoyancy overcomes viscous and thermal resistance.
- The onset of convection is determined by the Rayleigh number, which depends on temperature gradient, fluid properties, and layer thickness.
- Patterns typically take the shape of rolls, hexagons, or spirals, depending on conditions.
Examples:
- Boiling water in a pan may show these patterns before full turbulence sets in.
- Atmospheric convection and mantle convection in Earth’s interior can exhibit similar principles.
- Industrial processes involving heating fluids rely on understanding these convection patterns for uniform mixing or cooling.
Rayleigh–Bénard convection is a classic example of self-organization in fluid systems, helping scientists study transitions from order to chaos in thermally driven flows.