A beach wave has a velocity that can impart a significant pressure on a swimmer.
The velocity of a wave that is breaking onshore can be estimated from the wave height based on Froude's scale law.
velocity of the wave in meters per second =
= 25 * SQRT((height of the wave in meters) / 20)
A swimmer who is hit by a wave while on the shore bottom is exposed to a pressure that can be estimated from the wave velocity.
pressure in Newtons per square meter =
= 0.5 * 1000 * ((wave velocity in meters per second)^2)
where:
• 1000 is the density of seawater in kilograms per cubic meter.
• The area would be cross sectional area rather than body surface area. This can be estimated by height times width of the chest in meters.
A surfer would have additional kinetic energy imparted by forward velocity and any fall from height. The larger and heavier the person the greater the total energy that the person will be exposed to.
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