Real-time synthesis of the dynamic responses of floating bodies to waves for maritime simulators

A new implementation of the Fourier approach to synthesize spectral waves in real-time was recently published by the authors, based on an efficient GPU implementation and on a very flexible definition of the wave inputs. This paper presents an extension of the method to deal with the time-domain synthesis of frequency-domain responses of floating bodies, which can be calculated offline with a linear seakeeping solver. The frequency-domain responses are mapped from frequency/direction space to wavenumber space in order to match the same wave components used by the synthesis of the ocean surface, and they are transformed into time-domain responses by means of Inverse Discrete Fourier Transforms. Given the large number of elementary wave components required for a realistic visualization of the ocean surface, the synthesis of dynamic responses becomes computationally expensive and was implemented on GPUs relying on parallel reduction algorithms to speed up the summations. The performance of the GPU implementation was investigated, showing how the present method can synthesize multiple dynamic responses in real-time even when dealing with many elementary wave components. The physical accuracy of the technique proposed in the paper was assessed by simulating a virtual wave measurement buoy: the frequency-domain responses of the buoy were calculated with a linear seakeeping solver and then synthesized according to the proposed method. Then, the timeseries of buoy motions were used to reconstruct directional wave spectra, which proved to be in very good agreement with the wave spectra provided as inputs for the simulations.