Shallow Water Wave Celerity
Calculate the celerity of a wave in shallow water, c = √(g·h), from the water depth h (m) and gravity g. The result, in m/s, is the propagation speed when the depth is much smaller than the wavelength — a situation in which the wave 'feels' the bottom and its speed depends only on depth, no longer on the period. This is why waves refract as they approach the coast (the deeper part travels faster) and why tsunamis travel at hundreds of km/h in the deep ocean and slow down (piling up energy) as they reach the coast. Enter the water depth.
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Shallow water celerity
When a wave reaches shallow water (a depth much smaller than the wavelength), something changes radically: the wave begins to 'feel' the bottom, and its speed stops depending on the period and comes to depend only on the depth: c = √(g·h). The shallower the water, the slower the wave. This simple formula explains dramatic phenomena. Refraction: since the part of the wave in deeper water travels faster than the part in shallower water, the wave front bends, tending to line up parallel to the coast — which is why waves almost always arrive nearly head-on to the beach, even when they come in at oblique angles. Tsunamis: in the deep ocean (h ~4000 m), a tsunami travels at c = √(9.81 × 4000) ≈ 200 m/s (700 km/h!), as fast as a jet aircraft, yet only a few tens of centimetres high — imperceptible to ships; on reaching the shallow coast it slows down sharply, and with energy conserved, the wave piles up in height and can reach tens of metres. The focusing of energy on headlands and in bays, and wave breaking. The formula c = √(gh) is the basis of coastal hydrodynamics and of tsunami and storm-surge inundation modelling. Enter the water depth.
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Deep Water Wave Celerity
Calculate the celerity (phase velocity) of an ocean wave in deep water, c = g·T ÷ (2π), from the period T (s) and gravity g. The result, in m/s, is the speed at which the wave crest propagates. In deep water, longer-period waves travel faster — a phenomenon called dispersion, which makes long-period swell reach the coast before the short waves generated by the same storm. The celerity is half the group velocity (at which energy travels) in deep water. It is a base concept of wave hydrodynamics. Enter the wave period.
Ocean Wavelength
Calculate the wavelength of an ocean wave in deep water, L = g·T² ÷ (2π), from the wave period T (s) and gravity g (9.81 m/s²). The result, in meters, is the distance between two successive crests — in deep water, it depends only on the period. Long-period waves (swell from distant storms) have much larger wavelengths than local wind waves. The wavelength sets the depth at which the wave 'feels' the bottom (about L/2), starts to refract and shoal until it breaks. It is a fundamental parameter of linear wave theory and coastal engineering. Enter the wave period.
Wave Group Velocity
Calculate the group velocity of an ocean wave in deep water, c_g = g·T ÷ (4π), from the period T (s). The result, in m/s, is the speed at which the wave energy (and the 'envelope' of a wave group) propagates — exactly half the celerity (phase velocity) in deep water. This difference explains a curious phenomenon: within a wave group, individual crests appear at the rear, advance through the group (faster than it) and disappear at the front. The group velocity is what matters for energy transport and predicting swell arrival at the coast. Enter the wave period.
Wave Energy
Calculate the energy density of an ocean wave, E = (1 ÷ 8)·ρ·g·H², from the water density ρ (kg/m³, ~1025 for seawater), gravity g and the wave height H (m). The result, in J/m² (energy per surface area), is the sum of the wave's kinetic and potential energy — proportional to the square of the height, so large waves carry far more energy. It is the basis for calculating wave energy generation potential and the impact on coastal structures and beach erosion. Enter the water density and the wave height.
Wave Steepness
Calculate the steepness of a wave, s = H ÷ L, dividing the wave height H by the wavelength L. The dimensionless result is the relative steepness of the wave — the taller it is for its length, the steeper. Steepness has a physical limit: deep-water waves break when s exceeds about 1/7 (0.143), as the crest becomes unstable (120° angle). Young storm waves are steep; swell that travels long distances is gentle (low steepness). Steepness governs wave stability, breaking and vessel comfort. Enter the wave height and wavelength.
Wave Period
Calculate the period of a wave, T = 1 ÷ f, from the frequency f (Hz). The result, in seconds, is the time between two successive crests passing a fixed point — one of the most important properties of an ocean wave. The period determines the wavelength and celerity (in deep water), the depth at which the wave interacts with the bottom, and classifies the sea state: local wind waves have short periods (3-8 s), while swell from distant storms has long periods (10-20 s), travels faster and penetrates deeper. The period is measured by buoys and used in wave forecasting. Enter the wave frequency.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.