Sinclair, A., 2014. FlowRider: a Lagrangian float to measure 3-D dynamics of plunging breakers in the surf zone.

A very small and low-cost Lagrangian Float, the FlowRider, was developed to measure three-dimensional (3-D) free-surface accelerations and dynamics of plunging breakers and is described here. The FlowRider is equipped with a microelectromechanical systems inertial measurement unit, small enough to be deployed by one person in a laboratory wave tank or the surf zone, and is durable in both deployment environments. Free-surface accelerations of plunging breakers were measured by the FlowRider during a field experiment at Waimea Bay, Oahu, Hawaii. For wave heights greater than 0.3 m, the data clearly show when the FlowRider travels in a wave, is in free fall, and impacts the water surface below. Maximum free-surface accelerations measured exceed 8 g. The FlowRider represents a novel, low-cost instrument solution to obtain in situ measurements of 3-D dynamics of plunging breakers.