Synthetic aperture radar (SAR) images of ship wakes frequently exhibit long streaks. Some of the streaks are attributed to the Kelvin V-wave wake, and others are attributed to the turbulent and bright narrow V-wake. Ocean waves reduce the detectability of Kelvin wakes in SAR images. The SAR imaging of Kelvin wakes of two ships with different dimensions moving in rough sea is studied theoretically. The Kelvin wakes are simulated using the Michell theory. The random sea surface is simulated using the Pierson-Moskowitz type wave spectrum. The elevations of the points of the water surface and their velocities and accelerations are considered as a superposition of a ship's coherent waves and wind waves. A two-scale composite model and the velocity-bunching integral are used to simulate the intensity of SAR images of a disturbed sea surface with an embedded Kelvin wake. The fast discrete Radon transform is applied to detect the boundaries of the simulated Kelvin wakes. The probabilities of missing detections (PMD) and false alarms (PFA) are estimated numerically. The influence of ships, wind, and SAR parameters on PMD and PFA is discussed. It is illustrated that PMD/PFA strongly depend on the sea state. Index Terms-Probability of false alarms (PFA), probability of missing detections (PMD), Radon transform (RT), sea waves, ship wake, synthetic aperture radar (SAR).

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A linearized theory is presented for the dead-water phenomena. A two-layer fluid model of finite depth is assumed and the solutions for both the wave resistance, as well as the interface and free-surface disturbances, are obtained in terms of Green’s function. Numerical solutions are given for the case of a semi-submersible slender-body (prolate spheroid) moving steadily on the free-surface.

Despite the proliferation in coastal development world-wide little is known of the biological and ecological effects of man-made submerged habitats in coastal reefal environments. Such habitats, when able to move, offer unique environmental conditions, mainly in terms of hydrodynamic aspects. The current study tested whether floating habitats would develop unique communities in comparison to identical fixed ones, due to differences in current regime between the 2 types of habitat. We found significant differences in the hydrodynamic features associated with habitats of different motion capabilities, predominantly in mass-transfer rate, current velocity and shear stress. Floating installations had greater flow velocities and shear stress compared to fixed ones. We suggest that these hydrodynamic features determine the nature of the benthic communities on floating and fixed habitats, as the former revealed greater biomass and less chlorophyll content compared to the latter, while coral settlement was greater on the fixed installations, particularly near the seabed. The motion of floating artificial habitats increased the mass-transfer rate, as reflected by higher current velocities, and elevated the shear stress felt on their surfaces. These conditions encourage massive settlement of benthic macroinvertebrates and determine the community structure of floating artificial habitats in reefal environments.