Rayleigh-Bénard Onset

Convection cell formation at critical Rayleigh number Ra_c = 1708

Fluid Parameters

Ra = 1708
Ra_c = 1708
Ra/Ra_c = 1.00
Amplitude ∝ √(Ra−Ra_c)
Convection: onset
Ra = gαΔTd³/(νκ)
Ra < 1708: conduction only
Ra = 1708: onset (critical)
Ra > 1708: convection rolls

Color = temperature
Arrows = velocity field
Opt. roll ratio: λ/d ≈ 2.016