ABSTRACT
This chapter examines the small amplitude wave theory for a monochromatic directional wavemaker existing in a large basin, such that the side and end walls have negligible influence. Accurate laboratory modelling of coastal and ocean processes requires the use of directional wavemakers, which can provide a realistic sea state in the model basin. The wavemakers will be of varying lengths and the diffractive end effects will be discussed for two conditions: the wavemaker is flanked by rigid walls and when it is free standing in the basin. The kinematic boundary condition at the wavemaker requires that the water motion at the wavemaker match that of the wavemaker. The results for a wavemaker of finite length are nearly analogous to waves passing through a breakwater gap of the same length. For distances several wavelengths from the wavemaker, a Fresnel approximation gives a good approximation to the exact solution and eliminates the need to evaluate the integrals of Hankel functions.
