To our friend Ernie Tuck, in celebration of his multi-faceted talents. The velocity potentials of various unsteady point sources are derived in this paper for a two-layer fluid of finite depth. Two-layer fluids are often used to study effects of density stratification on hydrodynamics of marine systems. The sources here are restricted to the upper fluid layer and the potentials of the induced flows are given for the whole fluid domain. The velocity potentials of a transient source of arbitrary strength and in arbitrary three-dimensional motion are derived first. The potentials of a time-harmonic source without forward speed, and then with forward speed, are obtained from the transient source by specifying the appropriate source strength and motion. These potentials are fundamental to the analyses of various types of body motion in finite water depths under the influence of surface and interfacial waves. As a sample application, a numerical solution of the radiation and diffraction problem for a floating rectangular barge is presented. The results indicate that internal waves can have a strong effect on the motions of the floating barge over a wide range of incident-wave frequencies.Keywords Floating systems · Free-surface flow · Ship motion · Source function · Stratified fluid · Unsteady flow · Wave motion
BackgroundTwo-layer fluids are normally used to model certain types of density stratification in the ocean. Density stratification is quite common and is mainly caused by variation of salinity and water temperature with depth. Very often the change in density is confined within a thin pycnocline, above and below which, the water is well mixed, and the density is practically constant. For marine vehicles operating in this environment, a two-layer fluid is a good model to study the effects of density stratification on vehicle performance. In this paper, the density in each layer is taken as constant, and the fluid is assumed to be inviscid, incompressible and the flow irrotational. The pycnocline is assumed to be infinitesimally thin, and there is a density discontinuity across the interface between the upper and lower fluid
This paper presents the design of a prototype intersection collision warning system based on Vehicle Infrastructure Integration (VII). This system involves Roadside Equipment (RSE) at an intersection and several units of On-Board Equipment (OBE), each in a moving vehicle. When an equipped vehicle approaches the intersection, its OBE queries the remaining time before the light turns red from the RSE which is synchronised with the intersection signal. Combining its own speed and position, the OBE determines the likelihood of running the red light. In case of such a hazard, the OBE warns its driver and notifies other OBEs wirelessly.
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