A wake can refer to several distinct but related concepts in physics, transport and culture. Most commonly, it denotes the disturbed flow left behind a moving object — such as the patterned water behind a boat or the airflow behind an aircraft wing. The word also names a social practice: a vigil or gathering held around the time of a death. Other uses of the term appear in sports, engineering and popular language.
Fluid-dynamic wakes
In fluid dynamics, a wake is the region of disturbed fluid downstream of an object moving through a liquid or gas. Characteristic features include separated flow, vortices and turbulence; under steady conditions a repeating pattern of vortices (a Kármán vortex street) may form behind bluff bodies. The structure and intensity of a wake depend on factors such as object shape, size, speed and the fluid's viscosity and density.
Practical effects and examples
- Ships and boats produce surface wakes that can erode shorelines, affect moored vessels and create hazards for small craft and swimmers.
- Wakeboarding and wakesurfing intentionally use a vessel's wake for sport: the crest and trough provide a moving ramp and push for tricks.
- Animals exploit wakes: schools of fish and flocks of birds gain energy savings by positioning themselves in the flow created by others.
Aviation and wake turbulence
Aircraft generate strong trailing vortices at their wingtips, producing wake turbulence that can persist behind a landing or departing plane. These vortices create hazardous rolling moments for following aircraft, so air traffic control enforces separation minima and specific procedures to reduce risk. Wake turbulence is an important operational constraint at busy airports.
Funeral wake and cultural meaning
As a social custom, a wake is a vigil or gathering held before or after a funeral. Historically it came from watching over the deceased and keeping a wakeful vigil; today it functions as a time for mourners to view the body in some traditions, offer condolences, share memories and provide mutual support. Customs vary widely by culture and religion.
Other usages and notable facts
The term appears in other contexts: in accelerator physics a "wakefield" describes electromagnetic fields trailing a particle bunch, and in everyday speech "wake" may appear in compound forms (for example, "wake word" in voice interfaces). Despite differing domains, these uses share the core idea of an effect or presence left behind by an initiating event or object.