Calculation of loads caused by waves in offshore and shore structures is a recurrent practice in coastal engineering. To this purpose, accurate wave kinematics prediction is essential, especially at the free surface where velocities and accelerations are the largest. For regular waves the Stream Function Wave Theory is widely accepted and used. For irregular waves a Local Fourier approximation method exists. Such methodology is focused on exactly satisfy the free surface boundary conditions in a moving local window through a Local Fourier approximation of the velocity potential.

The Local Fourier approximation method is implemented in MatLab and tested against both stream function waves and laboratory experiments of irregular waves. Analysis of the results shows perfect agreement with predictions from Stream Function Wave Theory and with laboratory measurements.