Gravity-Capillary Wave Dispersion

Phase & group velocity, minimum wave speed, and surface wave packet evolution

Fluid Parameters

Wave Packet

At k₀

c_p (m/s)
c_g (m/s)
λ (mm)
c_min (m/s)
k_min (1/m)
Regime

Dispersion relation:

ω²=(gk + σk³/ρ)·tanh(kh)

Phase velocity: c_p = ω/k

Group velocity: c_g = dω/dk

Minimum phase speed:

c_min = (4gσ/ρ)^(1/4)

k_min = (gρ/σ)^(1/2)

k ≪ k_min: gravity waves, c_g=c_p/2
k ≫ k_min: capillary waves, c_g=3c_p/2