SIMPLIFIED ANALYSIS OF A PLUNGER-TYPE WAVEMAKER PERFORMANCE.

Abstract

Extending the theoretical work of Biesel, a study is made of a plunger-type wavemaker which uses a vertically-oscillating wedge. A simplified boundary condition is introduced on the contact surface between the wedge face and water. The first-order linearized hydrodynamic equations of motion are solved to obtain the velocity potential, which is composed of a wave part and a spatially transitory part. The wavemaker capability is analysed in terms of the ratio of the wave amplitude to the wedge stroke. The importance of the spatially ″transitory″ part (near field component) is discussed with regard to the role played by the inertia pressure, which is central to determining the hydrodynamic force on the wedge. Water surface elevations very near the wedge are computed for varying wedge immersions. The total hydrodynamic force on the wedge is obtained by integrating the hydrodynamic pressure over the wetted area of the wedge. A recommended range of wedge particulars is presented in view of the quality of generated waves and the force of the wedge. The hydrodynamic effects on the wavemaker performance seem to be well explained by considering the differing behaviors of the in-phase pressure and of the quadrature of inertia pressure with increasing water depth.