Acceleration and pressure measurements during wave-structure interactions

This paper presents a particle image velocimetry (PIV) based measurement technique for flow acceleration. Based on the illumination of seeding particles three times over two frames and continuously tracking an individual particle over the three distinct illuminations, two velocity fields and a Lagrangian acceleration are obtained. Subsequently, the dynamic pressure can be calculated by integrating the Lagrangian acceleration through the Euler equation, provided that the fluid is incompressible and the flow is inviscid. The technique not only provides a method for acceleration measurement but also reduces the constraint on the time separation between adjacent illumination pulses imposed by the camera framing rate in a single pulsed triple-frame technique to a much shorter camera specific frame transfer time. Monte Carlo simulations are used to test the technique for a deep water wave.