Iribarren number
In fluid dynamics, the Iribarren number or Iribarren parameter – also known as the surf similarity parameter and breaker parameter – is a dimensionless parameter used to model several effects of (breaking) surface gravity waves on beaches and coastal structures. The parameter is named after the Spanish engineer Ramón Iribarren Cavanillas (1900–1967), who introduced it to describe the occurrence of wave breaking on sloping beaches. For instance, the Iribarren number is used to describe breaking wave types on beaches; or wave run-up on – and reflection by – beaches, breakwaters and dikes. Definition. The Iribarren number which is often denoted as  Ir or "ξ" – is defined as: where "ξ" is the Iribarren number, formula_3 is the angle of the seaward slope of a structure, "H" is the wave height, "L" is the deep-water wavelength, "T" is the period and "g" is the gravitational acceleration. Depending on the application, different definitions of "H" and "T" are used, for example: for periodic waves the wave height "H" at deep water or the breaking wave height "H" at the edge of the surf zone. Or, for random waves, the significant wave height "H" at a certain location. Breaker types. The type of breaking  wave – spilling, plunging, collapsing or surging – depends on the Iribarren number. According to , for periodic waves propagating on a plane beach, two possible choices for the Iribarren number are: where "H" is the offshore wave height in deep water, and "H" is the value of the wave height at the break point (where the waves start to break). Then the breaker types dependence on the Iribarren number (either "ξ" or "ξ") is approximately: