Experimental analysis of cylindrical wave fields

In a previous theoretical paper submitted to EWTEC, the authors showed that the wave energy converter (WEC) wave field can be accurately and analytically represented by cylindrical linear waves with the appropriate coefficients. In that paper, the coefficients were found computationally using the boundary-element method software, WAMIT. For the present paper, experiments were conducted in the newly refurbished University of Edinburgh Curved Wave Tank to determine the same cylindrical coefficients for progressive waves. The experiments employed two body geometries, an attenuator consisting of a horizontal pitching cylinder, and a terminator made up of a bottom-hinged flap. An array of 59 wave gauges was arranged in a circle-spoke pattern, where the circle of wave gauges was necessary for deriving the cylindrical coefficients, and the spokes, which extended radially further afield, were used for validation. Both the scattered and the radiated waves of the bodies were examined at three frequencies. High-order harmonics were present in a number of the wave fields, and tank reflections were problematic. Despite this, the linear analytical wave field, whose coefficients were found experimentally, agrees well with the experimentally measured linear wave field at points other than those used to derive the coefficients. The results serve to validate linear wave theory as it relates to the wave field and reinforce the concept that these waves can be used to compute WEC performance and wave farm interactions and impacts.