Wind_wave - Wikiparency

# Wind wave Wind waves are generated by wind blowing over water, and how big they get depends on three things: how hard the wind blows, how long it blows for, and how far it blows across open water — the fetch. Run out of any one and the sea stops growing, which is why a gale on [[Lake_Superior]] never builds the swell a moderate wind builds across an [[Ocean_current|ocean]]. ## Microsim — p5.js Sidecar: `Wind_wave.p5.js` · route leaf: `microsim/p5js/Wind_wave__20260910T0400Z`. Built to the Betterfire Standard v0 (single `ARTICLE` constant, HUD title and Wikitube URL, control hints, parameter readout and equation). | Control | Does | |---------|------| | `wind slider` | wind speed | | `fetch slider` | distance the wind blows over water | | `[d]` | deep water / shallow water | *What to watch:* Raise wind and fetch and the spectrum's peak grows and slides to longer periods. Watch the orbital circles under the surface shrink with depth — and flatten when you make the water shallow. ## A spectrum, not a wave A real sea is not one wave but a superposition of many periods travelling in slightly different directions, described by a wave spectrum — the same [[Fourier_analysis|spectral]] description used in [[Signal_processing]]. Long waves travel faster than short ones in deep water, so a distant storm's energy sorts itself out on the way and arrives as clean, long-period swell days later. That dispersion is what makes surf forecasting possible: measure the arriving period and you know how far away and how long ago the storm was. ## Deep and shallow In deep water a wave's speed depends on its wavelength and the water barely notices the bottom; particle orbits are circles that shrink with depth, decaying much as [[Vorticity]] does in a [[Boundary_layer]]. Once depth falls below about half a wavelength, the bottom takes over, orbits flatten to ellipses, and speed depends on depth alone — the shallow-water regime that governs [[Tsunami|tsunamis]], shoaling and breaking. Steepness sets the limit: push a wave past roughly one in seven and it breaks, which is where [[Langmuir_circulation]] and surface [[Turbulence]] get their energy. **Reads with:** *Introduction to Physical Oceanography (Robert H. Stewart, 2008)* — [OTL record](https://open.umn.edu/opentextbooks/textbooks/introduction-to-physical-oceanography) · [download](https://github.com/introocean/introocean-en/releases/tag/v20200229) · CC BY-NC-SA. Section 7 of the [[PORTAL_Thury_Hydrodynamics_Apex_Spine|Apex Spine]] book shelf. **On the spine:** [[Tsunami]] · [[Langmuir_circulation]] · [[Fourier_analysis]] · [[Tide]] · [[WT!Thury_Hydrodynamics_Compendium]].  **Part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]]** — main article for section 34, *Waves and tides*. Related sections: [[Hydropower]] · [[Geophysical_fluid_dynamics]] · [[Lake_Superior]].   **Microsim — three.js (Wikitube framework):** *Wind wave* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/thury/Wind_wave.html" data-title="Wind wave"></div> *Built from `MICROSIM_GUIDE/specs/sims/Wind_wave.json`; part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]] set.*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Wind_wave) : [Wikitube](https://en.wikitube.io/wiki/Wind_wave) ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_WT!Thury_Hydrodynamics_Compendium]], [[PORTAL_Physics]]. --- *Book-section wave · 2026-09-10 · article + p5 microsim shipped together.*