Ocean Wave Spectrum Estimation Using Wave Buoy Analogy

Abstract The application of digital twin technology, which combines real-world measurement data with a digital model of the ship, is gaining attention in the field of structural integrity management. Considering the limited number of sensors that can be installed on a ship, the incorporation of a digital twin concept, which combines measurement data with the ship’s digital design model, can play a crucial role in ensuring structural integrity management. This study presents a methodology to estimate local responses at locations where measurements are not available, utilizing both measurement and design data. To estimate the response at unmeasured locations, the directional wave spectrum was first estimated using the least square method, minimizing the error between the estimated response spectrum and the measured response spectrum. In this process, the measured spectrum is obtained by filtering and Fourier transforming the measured time series acquired from the sensor. And the estimated spectrum was obtained through the product of the directional wave spectrum and the Response Amplitude Operator (RAO), followed by integration. And B-spline was introduced to represent the directional wave spectrum. To validate the methodology, artificially generated pseudo-measurement data using wave spectrum and RAO of 13,000 TEU container ship was employed. Subsequently, the directional wave spectrum was estimated using pseudo-measurement data, and the estimated directional wave spectrum, along with the Response Amplitude Operator (RAO), was utilized to estimate the response spectrum.