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The importance is given for the efficient design of offshore structures which should include economic and safety concerns. The properties of wind-generated (main) surface waves and currents are recognized to play a vital role during design of offshore structures such as windmills, fixed and floating structures. This study looks into the mechanisms of metocean forces, acting on these structures near the continental shelf region of Malaysia. At present, near offshore Malaysia, there is no real behaviour model available for currents and the interaction between waves and current. The free surface flow and rigid body interaction with structural issues of offshore structures such as fatigue, corrosion, and marine growth are also not researched in this region before. Therefore, current and wave-current models need to be developed using the finite volume method. Physics of these forces need to be determined and their free surface flow motions require the development of a framework. Fluid-structure interaction (FSI) is used to model the interfaces such as air-fluid (free surface) and fluid-structure (rigid-body). A Free-surface rigid body problem fully coupled finite volume model is a preferred method. Six degree of freedom of motion equations are used to define the rigid body. This paper is based on literature review and the expected results due to the effects of wind on wave and currents and the mechanics of current are highlighted along with the seasonal effects of the current. To deal with the moving rigid body and the fluid domain interface an interface-tracking method is used. [ABSTRACT FROM AUTHOR]

Coastal dispersal of sewage effluent from the Tarumi Sewage Treatment Plant located in Osaka Bay, Japan, was investigated with a quadruple-nested high-resolution ROMS model coupled with a 3-D passive tracer model. The study area is quite famous for seaweed farming in the nation, which has been claimed considerably affected by the effluent from the plant, particularly in fall when the seaweed spores are most vulnerable to contamination that counteracts their favorable growth and productivity. We applied the model to three different discharge scenarios to explore possible optimal operations that could reduce the influences. If the discharged volume rate is simply decreased at ~16.7% relative to the baseline case that represents the actual operation, the effluent accumulating in the farm is reduced at ~25.4% showing a significant nonlinearity. A tracer flux analysis demonstrated that the transient component accounting for fluctuating tides and eddies dominates over the time-averaged linear contribution to the effluent accumulation in the cross-shore effluent transport to the farm. By contrast, in the along-shore direction, the linear component leads to increased influx near the surface at the western transect of the farm, while the transient component is more essential to the overall reduction of the incoming tracer flux to the farm. On the other hand, density adjustment of the effluent for suppressing surfacing of buoyant effluent plume released from the bottom-mounted diffusers does not work well as expected, because pronounced far-field dilution takes over the near-source dilution affected by the density adjustment. [ABSTRACT FROM AUTHOR]

Niida River, Fukushima, Japan, is well known to be a source of highly contaminated suspended radiocesium to the ocean, which is originated from the Fukushima Dai-ichi Nuclear Power Plant during the accidental leakage occurred in March 2011. We examined the oceanic dispersal and inventories of the sediments and suspended radiocesium in the ocean floor derived from Niida River, using a quadruple nested JCOPE2-ROMS 3D circulation model in a very high resolution configuration, coupled with a 3D multi-class sediment transport model, the iRIC-Nays 2DH river sediment model, the SWAN spectral wave model, and a static radiocesium absorption model. A particular attention was paid to the storm and subsequent flood event associated with Typhoon 201326 (Wipha) passed off the Fukushima Coast in October 2013, which provoked an enormous amount of precipitation, and subsequent riverine freshwater discharge and sediment fluxes to the ocean. With a guide of several in situ observed data, we carried out a quantitative assessment of the accumulation and erosion of the sediments and resultant suspended radiocesium distribution around the river mouth and nearshore areas along the Fukushima Coast. [ABSTRACT FROM AUTHOR]

A high-resolution, high-precision downscaling oceanic circulation model for the Southern China Sea (SCS) was developed based on the Regional Oceanic Modeling System (ROMS) at a lateral resolution of 5 km, initialized and forced by the HYbrid Coordinate Ocean Model (HYCOM) global reanalysis product. A multi-year reanalysis was conducted with the HYCOM-ROMS system that properly accounts for wind stress and heat budget at surface, freshwater influences from the atmosphere and major rivers, and tidal variability. Prospective applications of the system include assessments of oceanic dispersal of wastewater, quantification of marine ecosystem network, analyses of micro plastic transport and its coastal accumulation, etc. In prior to applied studies, we extensively investigated the validity and performance of the developed system. We found that it successfully reproduced primary dynamics of the SCS in many aspects such as the transient Kuroshio path in the south of Taiwan prominently affecting the circulation of the northern SCS through the Luzon Strait. The North Equatorial Current (NEC) drifting near Bismarck Archipelago, New Guinea, sporadically intrudes into the Indonesian water and adjacent seas to invoke bifurcating northward and westward currents. This intrusion promotes the northwestward mass transport into the Celebes Sea and further into the Sulu Sea, and then enters the SCS through the Palawan Strait. [ABSTRACT FROM AUTHOR]

This paper theoretically examines weakly nonlinear propagation of plane progressive waves in an initially quiescent compressible liquid containing many spherical microbubbles. Waves propagate with a large phase velocity exceeding the speed of sound in a pure water, which is induced by the incorporation of compressibility of the liquid phase. For simplicity, the wave dissipation owing to viscosity in the gas phase and heat conduction in the gas and liquid phases are ignored, and the wave dissipation is thereby owing to the liquid viscosity and liquid compressibility. The set of governing equations for bubbly flows is composed of conservation equations of mass and momentum for gas and liquid phases, the equations of motion describing radial oscillations of a representative bubble, and the equation of state for both phases. By using the method of multiple scales and the determination of size of three nondimensional parameters, i.e., the bubble radius versus wavelength, wave frequency versus eigenfrequency of single bubble oscillations, and wave propagation speed versus sound speed in pure liquid in terms of small but finite wave amplitude (i.e., perturbation), we can derive a nonlinear wave equation describing the wave behavior at a far field. [ABSTRACT FROM AUTHOR]