A two-dimensional numerical Model has been developed to study wave breaking on a sloping beach. The basic elements of numerical Model are Reynolds Averaged Navier-Stokes (RANS) equations that describe the mean flow motion of a turbulent flow; a k turbulence closure Model that describes the turbulent transport and dissipation process; an efficient technique (VOF- Volume Of Fluid method) for tracking the free surface motion; and a new scheme developed by Lin and Liu (1999) for wave generation. Shoaling, breaking and overturning of solitary wave on a slope of 1/16 have been studied with the main emphasis on turbulence characteristics. Turbulence characteristics i.e., turbulence kinetic energy, k; turbulence dissipation rate, ; turbulence production, pr; turbulence eddy viscosity, vt; and their spatial distribution during the breaking process have been discussed in great details. Spatial distribution of turbulence characteristics and the order of magnitude have been found to be in agreement with existing experimental and numerical studies. The main characteristic of plunging breaking waves, the shoreward advective transport of turbulence, has also been investigated and numerically proved.

Sieve tray CFD Modeling with the assessment of k-£ Turbulence method and VOF framework has been considered in the current research work. Gas superficial fac- tor has been varied from 0.462 to 1.464 ((kg/m)0.5.s-1), while, the liquid flow rate changed from 17.8´10-3 (m3/s) to 6.94´10-3 (m3/s). Comparison between VOF and Eulerian methods proved that simulation error decreased from 16% to the only 2% for clear liquid height in different gas superficial factors. Moreover, this error was only 7% in comparison with 35% with the variation of liquid flow rates. These error values are obtainable when they are compared with the experimental data of Solari & Bell. Consequently, froth height has the good agreement with the mostly well known Colwell correlation. Interfacial area as the most important characteristic of the VOF has been investigated in this work and showed an increase from 0.18 m2 to 1 m2 with the increase of gas superficial factor to 1.464. The pressure profiles have also been investigated.

Numerical simulation of nonlinear waves is of prime importance. In this research the WISE 2DV numerical Model has been deployed. In the WISE Model Reynolds-averaged Navier-Stokes (RANS) equations have been solved using finite volume discretization and projection method. The method of volume of fluid for surface has been implemented in the Model. For implementation of VOF method, Youngs scheme has been utilized. In this scheme color function advection is based on piecewise linear interface reconstruction. The k-e Model is used for turbulence closure of RANS equations. For validation of the Model a short amplitude sloshing wave in a tank, regular wave in a flume and propagation of solitary wave have been simulated, and the results have been compared with analytical solutions, which show very good agreements. A non-linear short wave propagation has also been simulated, and predictions have been compared against experimental results, which confirms the Model ability in prediction of non-linear short waves.

Cavitation is the most important problem in the bottom outlets of dams because of high flow velocities. Due to flow velocities up to 30 m/s and negative pressures, remarkable damages occurred on the lining of these tunnels. In this paper, a numerical Model based on the finite volume method for fully three-dimensional (3D) using VOF Model in two-phase including air and water is applied. Validation of the work has been obtained by comparison with measurements of a laboratory Model, i.e., the pressure and velocity magnitudes are computed along the tunnel with error up to 20 percent. Cavitation index in flow direction have been estimated under different conditions of gate opening and shown critical situation (less than 0.25) at the downstream the gate. For aerated flow, the cavitation index were increased up to 6-7 times greater than the non-aerated flow and improved the flow conditions for cavitation occurrences.

Bottom outlet leaf gates are one of the most important structures which are used to control the flow for down steam requirements. Therefore, gate should be taken for an accurate design of such structures. The designers should check for any kind risk such as, cavitations, vibration or flow discharge through these outlet conduits. The investigations regarding the design of these structures usually fall into category of physical Modeling or numerical investigations. However, the physical Model studies are very expensive, and thus, numerical studies have attracted the attention of many investigators. In this paper Numerical studies based on Nabier-stokes equations were applied to predict the how domain pass a normal gate in a high pressure conduit. The Model uses SIMPLE Algorithm to solve the equations and the water surface profile is determined using VOF method witch has been successfully applied for free surface flow by many investigational. The results showed a reasonable agreement with those of experiments ti predict the pressure, velocity and water surface profile.

In the present study, volume of fluid method in Open FOAM open source CFD package will be extended to consider phase change phenomena due to condensation process. Both phases (liquid-vapor) are incompressible and immiscible. Vapor phase is assumed in saturated temperature. Interface between two phases is tracked with color function volume of fluid (CF-VOF) method. Surface Tension is taken into consideration by Continuous Surface Force (CSF) Model and mass transfer occurring along interface is considered by Lee mass transfer Model. Pressure-Velocity coupling will be solved with PISO algorithm in the collocated grid. This solver is validated with Stefan problem. In one dimensional Stefan problem, the desistance of interface motion from cold wall is compared with the analytical solution. Then condensate laminar liquid film flow over vertical plate is simulated in the presence of gravity. Numerical result shows calculated film thickness from numerical simulation is thinner than analytical solution. Also, it shows Nusselt number is a function of vapor specific heat which is neglected in existing correlations, therefore analytical solution and experimental correlation should be modified to consider this effect on the Nusselt Number.