On the Wave Spectrum Selection in Ocean Wave Scene Simulation of the Maritime Simulator

Abstract

AbstractThe Phillips spectrum is widely used in the real-time scene simulation of ocean waves. Structural analysis has shown the Phillips spectrum to be an instantaneous spatial spectrum. Its frequency spectrum agrees with the spectrum form raised by Neumann, and is close to the P-M spectrum. Its directional distribution function is in the form recommended by the International Towing Tank Conference. However, the Phillips spectrum has two problems in application. First, neither the value nor the calculation method of the spectral constant A is given. Second, the height above ocean surface of the spectral wind speed is not provided. The spectral constant A is calculated on the hypothesis that the wave energy per unit area of the Phillips spectrum equals that of the P-M spectrum, and the height is specified with reference to the P-M spectrum. Apart from the Phillips spectrum, other spectrum should be considered, so we use the JONSWAP-Poisson spectrum. The spectrum has the JONSWAP spectrum as its frequency spectrum, and its distribution function is the Poisson form. The two spectra are applied for ocean wave scene simulation. A comparison of the simulation results of the two spectra shows that wind speed and fetch length can affect the shape of the generated ocean wave. The simulated ocean waves of the Phillips spectrum can reflect the wind speed and direction influence on the wave, but they cannot reflect the fetch length effect. The simulated waves of the JONSWAP-Poisson spectrum can embody the effect of the wind speed, wind direction, and fetch length on the wave. The frame rates of the two spectra are equal. To sum up, for wave spectrum selection of wave scene simulation in the maritime simulator, the wind parameter of the spectrum should contain the wind speed, wind direction, and fetch length, and the wave generated by the spectrum should be in (-(,(] of the wind direction. Thus, the JONSWAP-Poisson spectrum is more suitable than the Phillips spectrum. The method has been used in the maritime simulator.Keywordsocean wave scene simulationocean wave spectrumdirectional distribution functionwind speedfetch length