Two Novel Free Surface Measurement Techniques Developed at DTMB

Capacitance wave probes have been traditionally used at DTMB for measuring the wave heights in the Kelvin wake of towed surface ship models. Two new wave height measurement systems have recently been developed at DTMB: a laser wave height probe, using a linear array of charged couple devices, and a surface sensing mechanical probe. These devices represent improvements to the capacitance probes in the form of reduced and/or eliminated susceptibility to contamination and increased frequency response. In this paper, the physics of operation of the measurement systems and design considerations for their optimization will be discussed. Measurements of the free surface in a regular wave field, and for longitudinal wavecuts with a ship-model, over a wide Froude number range, have been made. Based on experimental results, evaluations of the various attributes and shortcomings of each type of probe will be made.