Abstract
This study numerically investigates the propagation characteristics of hazardous noxious substances (HNSs) spilled from transport ships and suggests the metal model for predicting the HNS propagation velocity varied with the current velocity and HNS density. The commercial computational fluid dynamics (CFD) code ANSYS FLUENT (V. 17.2) was used for two-dimensional simulation based on the Reynolds-averaged Navier–Stokes (RANS) equation together with the standard k–ε model. The scalar transport equation was also solved to estimate the spatial and transient behaviors of HNS. The main parameters to analyze the near-field propagation characteristics of HNSs spilled from the ship were layer thickness, HNS concentration, and propagation velocity. It was found that advection becomes more dominant in propagating an HNS layer that becomes thinner as the current velocity increases. When the current velocity increased beyond a certain level (~0.75 m/s), the mixing effect made the HNS layer less dense but thicker. Consequently, lower-density HNS causes increased HNS concentrations at sea level. As the current velocity increased, the concentration distribution became homogeneous regardless of HNS density. In particular, the second-order response surface model provided for three variables on the basis of the numerical results for 15 cases with the use of the general least-squares regression method, showing a good fit. This model would be useful in estimating the propagation velocity of HNS spilled from a ship.
Highlights
Hazardous and noxious substances (HNSs) are widely known as liquid and mixed-liquid substances that can have harmful effects on the marine environment [1]
If an HNS-related accident occurs in a port or on a ship, harmful substances are diffused in the vicinity of the ships in different ways depending on the type of spill material [2]
It is difficult to cope with HNS accidents because of the high risk associated with various HNSs with bioaccumulative, biodegradable, toxic, and explosive characteristics [3,4,5,6,7,8]
Summary
Hazardous and noxious substances (HNSs) are widely known as liquid and mixed-liquid substances that can have harmful effects on the marine environment [1]. Janeiro et al [12] suggested a prediction model of oil-spill trajectory, which was coupled with hydrodynamics, oil transport, and a weathering model They focused mainly on the validation of the developed model by comparison with the observed data from oil spills in the Tuscany Archipelago region. The main purpose of this far-field analysis is to show the bulk motion of a spilled substance based on acquired data of winds and sea currents This approach fails to intrinsically examine the near-field propagation characteristics in the vicinity of the transport ship because it treats such a finite region near the ship as a point source, numerically. This is because the highest risk scenario is generally considered in handling HNS accidents in the sea Under this limitation, the two-dimensional analysis seems to be suitable for analyzing the propagation characteristics because of the very high. The HNS layer thickness, averaged HNS concentration at sea level, and average propagation velocity were predicted for different current velocities and HNS densities
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