Hideo Kawarada

Numerical simulation of spilled oil by fictitious domain method

Pollution due to spilled oil presents serious natural environment issues. In order to take effective measures against such accidents, the knowledge of behavior of oil in such accidents is urgently required. Although its behavior both offshore and in the surfzone is important, this paper concentrates on the latter problem. A flow field of seawater and spilled oil above and under the beach is simulated numerically in this study. This research effort adopts the Cross model as a constitutive equation for spilled oil. Oil adhesion properties are taken into consideration through a friction type boundary condition prescribed on the surface of spilled oil. Flow equations for respective fluids and boundary conditions between them are unified into a single flow equation to construct a numerical model. The fictitious domain method plays an important role in the unification procedure. Computation becomes rather simple due to unification of equations.

Mathematical study of trade-off relations in logistics systems

This paper presents a mathematical model of trade-off relations arising in third party logistics using Pareto optimal solutions for multi-objective optimization problems. The model defines an optimal set of distribution costs and service levels constituting a trade-off relation. An analogy to the concept of the indifference curve in the field of economics is discussed. Numerical experiments for a simplified problem are performed, demonstrating an increasing process of the utility of logistics.

Demand Forecasting Method Based on Stochastic Processes and Its Validation Using Real-World Data

Demand forecasting problems frequently arise in logistics and supply chain management. The Newsboy Problem is one such problem. In this paper, we present an improved solution method using application of the Black–Scholes model incorporating stochastic processes used in financial engineering for option pricing. Through numerical experiments using real-world data, the proposed model is demonstrated to be effective.

Unified model for wave breaking action and internal flow in a tidal flat

What kind of correlation exists between waves on the beach and tidal flat ecosystems? This chapter clarifies the above problem using mathematical science. Concretely, we simulate phenomena involved in the problem by building a mathematical model.

Theoretical study of oil pollution

We discussed effects of waves on a tidal flat ecosystem in Chap. 3 and understood remarkable works of nature in the neighborhood of the margin. In this chapter, we analyze what effects the intervention of oil gives to the harmonious relation between waves and tidal flat ecosystems.

Oil pollution: human damage on hydraulic regime and benthic communities in tidal flat ecosystems

Waves and tides are two major driving forces to supply seawater into sandy beach and tidal flat sediments. Contrary to the role of waves on seawater infiltration, tides are major force than waves for oil penetration into sediments as shown in Chapter 4. This chapter deals with infiltration of stranded oils into tidal flat sediments and its effects on seawater infiltration.

What is tidal flat

Wave and current energies are important factors in determining the physicochemical and biological conditions in coastal ecosystem. Sandy beach develops in the area of very high physical energies facing open ocean where coarse grained sands make beach and sediments are completely oxidized. On the other hand, tidal flat develops under sluggish currents in river mouth and semi-enclosed coastal area where finer particles are trapped in the flat and sediments show strong reducing conditions sometimes to sediment surface.

Oil pollution: human damages on hydraulic regime in sandy beach ecosystems

Various anthropogenic pollutants ultimately threaten coastal areas. One of the most significant anthropogenic pollution is oil pollution. It is estimated that 1.7- 8.8 X 106 tons of petroleum hydrocarbon are released into marine environment annually (Natural Research Council, 1985). Oil enters marine environment in many ways like natural seeps, refinery emission, ship cleaning operations and accidental spills. In particular, tanker accidents that may result in the release of relatively large amount of oils near sensitive coastal environments are of great concern. For example, the Amoco Cadiz discharged 0.2 X 106 tons of Kuwait crude oil into the waters along the Brittany coast in March 1978; the Exxon Valdez released 0.04 X 106 tons of Alaskan North Slope crude oil into Prince William Sound in March 1989. A part of the spilled oil into sea has drifted to the coastal area. About 30% of the Amoco Cadiz spilled oil contaminated 320 km of coastline. In case of the Exxon Valdez, about 50% of the spilled oil stranded on 2,000 km of shorelines along the Gulf of Alaska (Swannell et al., 1996; Wolfe et al., 1994; Vandermeulen et al., 1979).

Decomposition mechanism of spilled oil by bacteria

The unified model formulations developed in Chapters 3 and 5 make it possible to clarify mechanisms of oil decomposition by adding crucial devices to them; this has not been experimentally clarified yet. Multi-phase flow formulation with decomposition contributes to this study. Main components of decomposed materials by bacteria are water, soluble components, and carbon oxides. We deal with the case in which oil decomposes into water. A characteristic of this case is appearance of a jump boundary condition for normal component of velocity at the decomposition surface between oil and water, which is based on density difference between them.

Methodologies for theoretical studies

In this chapter, we explain the fundamental methodologies for theoretical studies stated in Chaps. 3, 5, 7 and 8, which correspond to facilities utilized in experimental studies in Chaps. 1,2,4 and 6. These methodologies consist of a mathematical part and a numerical one, which have been developed by the authors to promote the studies concerned. These methodologies are combined to obtain fruitful results in the computer which can be observed in the form of the many figures included in this book. They have contributed to deeper understanding of remarkable works of nature at environmental margins.