A two-dimensional computer model is developed to simulate free surface flow interaction with a moving body. The model is based on the cut-cell technique in a fixed-grid system. In this model, a body is approximated by the partial cell treatment (PCT), in which an irregular body is represented by the volumetric fraction of solid in Cartesian cells. The body motion is tracked by Lagrangian method whereas the fluid motion around the body is solved by Eulerian method. The concept of "locally relative stationary (LRS)" is introduced in this study. In the LRS method, a source term is added locally to the conventional continuity equation on body surfaces to take account of body motions, which subsequently affects the computational results of fluid pressure and flow velocity around the body. The LRS method is incorporated into an earlier Reynolds averaged Navier–Stokes (RANS) equations model developed by Lin and Liu [A numerical study of breaking waves in the surf zone. J Fluid Mech 1998; 359: 239-64]. The new model is capable of simulating generic turbulent free surface flows and their interaction with a moving body or multiple moving bodies. A series of numerical experiments have been conducted to verify the accuracy of the model for simulation of moving body interaction with a free surface flow. These tests include the generation of a solitary wave with the prescribed wave paddle movements, water exit and water impact and entry of a horizontal circular cylinder, fluid sloshing in a horizontally excited tank, and the acceleration/deceleration of an elliptical cylinder near a water surface. Excellent agreements are obtained when numerical results are compared to available analytical, experimental, and other numerical results. The model is a simple-to-implement computational tool for simulating a moving body in turbulent free surface flows.

This paper presents a numerical model for simulating wave interaction with porous structures. The model calculates the mean flow outside of porous structures based on the Reynolds averaged Navier-Stokes equations. The corresponding turbulence field is modeled by an improved k-e model. The flow in porous structures is described by the spatially averaged Navier-Stokes equations. The drag forces caused by the presence of a solid skeleton are modeled by the empirical linear and nonlinear frictional forms. The numerical model is first calibrated by simple experiments for flow passing through a porous dam with different porous media. Excellent agreements are obtained for the case using gravels with mean sizes of O (1cm) to O (10cm) as the materials for the porous dam. Reasonably good agreements are also obtained when small uniform glass beads with diameters of 3 mm are used. The calibrated numerical model is then employed to investigate the breaking wave overtopping a caisson breakwater, protected by a layer of armor units. Good agreements between numerical results and laboratory data are obtained in terms of both free surface displacement and overtopping rate. Different design scenarios are also studied numerically. The porous armor layer is effective in reducing the overtopping rate as well as in preventing the caisson breakwater from bottom scouring.

A three-dimensional numerical model is developed in this study to investigate the problem of wave–current–body interaction. The model solves the spatially averaged Navier–Stokes equations. Turbulence effects are modeled by a subgrid-scale (SGS) model using the concept of large eddy simulation (LES). The model is employed to study the wave–current interaction with a square cylinder that is mounted on the bottom and vertically pierces the free surface. The force analysis demonstrates that the presence of waves can reduce both the strength and frequency of vortex shedding induced by a uniform current due to the nonlinear wave–current interaction. The free surface elevation, strain rates of the mean flow, and eddy viscosity are found to closely correlate with the mechanism of vortex shedding. It is also shown that when the vortex shedding is neglected in the calculation such as by the potential flow approach, one may significantly underestimate the magnitude of in-line force. The energy spectral analysis reveals that there exist initiating, growing, and decaying regions for shedding vortices around the cylinder. In the vortex initiating region, both coherent and turbulent structures are nearly two-dimensional that become three-dimensional in the vortex growing region. The kinetic energy of both coherent and turbulent motions is dissipated in the vortex decaying region, within which the mean flow gradually returns back to two-dimensional.

For fast-degraded chemicals such as 1，3. dichloropropene(1，3-D)，their long persistent time in topsoils cannot be explained bv the ordinary first. order kinetics of biOdegradatiOn that iS commonly used in the simulation of chemical transport in soils. The Monod kinetics of biodegradatiOn，which iS usually defined as the mathematical relationship between the residual concentration of the growth. 1imiting substrate and the specific growth of degraders in laboratory reactors，was found to be responsible for the phenomenon of "decelerated biodegradatiOn". To take advantage of both the simplicity Of first. order kinetics in transport modeling and the realistic description Of Monod kinetics for a physical situation. a simplified method was used to represent Monod kinetics with the corresponding pseudo first. order kinetics. Pseudo first. order constants fitted with Monod kinetics were later substituted into the transport model. A satisfactory agreement between field measurement and simulated results using these constants was achieved.

This paper presents a combined experimental and numerical effort to study solitary wave runup and rundown on beaches. Both nonbreaking and breaking solitary waves are investigated. A two-dimensional numerical model that solves both mean flow and turbulence is employed in this study. For the nonbreaking solitary wave on a steep slope, numerical results of the present model are verified by experimental data and numerical results obtained from the boundary integral equation method model, in terms of both velocity distribution and free surface profiles. The characteristics of flow patterns during runup and rundown phases are discussed. The vertical variations of the horizontal velocity component are large at some instances, implying that the shallow water approximation may be inaccurate even for the nonbreaking wave runup and rundown. For the breaking solitary wave on a mild slope, numerical results of the present model are compared with experimental data for free surface displacements. The present model is found to be more accurate than the depthaveraged equations models. Using this numerical model, the mean velocity field and turbulence distribution under the breaking wave are discussed.