TYPE-E DOUBLE-ACTUATED WAVE-MAKERS

The Ploeg and Funke TYPE E double-actuated wavemaker has been calibrat ed at the CEPYC-CEDEX Laboratory in Madrid, Spain. TYPE E double-actua ted wavemakers are capable of operating as piston-only, hinged-only, o r simultaneously as both piston and hinged wavemakers. An eigenfunctio n expansion for the fluid motion generated by a generic planar wavemak er of variable-draft is used to describe the motion of double-actuated wavemakers. This generic solution appears to be more robust and easie r to apply in numerical codes than the ones that require the amplitude of the wavemaker stroke be specified at the still-water-level and tha t require the draft of the hinge to be forced to minus infinity in ord er to recover a piston wavemaker. The dimensionless transfer functions for the ratio of the wavemaker stroke to the wave amplitude are deriv ed by equating the total average power generated by both actuators to the energy flux in the propagating wave. The solution is not unique be cause both the ratio of the amplitude of the piston actuator to the am plitude of the hinge actuator and the relative phase angle between the motion of the two actuators are arbitrary. Experimental verifications of the theory are given for each actuator operating independently as well as for three ratios of the piston amplitude to hinge amplitude wh en the relative phase angle is zero. These calibrations indicate that TYPE E double-actuated wavemakers are perhaps the optimum wavemakers f or simulating double-peaked spectra such as the six parameter Ochi-Hub ble spectra where the hinge actuator is optimum for generating the hig her frequency components.