A CFD code has been developed to describe the salt solution density current, which propagates three-dimensionally in deep ambient water. The height and width of the dense layer are two dominated length scales in a 3-D structure of the density current. In experimental efforts, it is common to measure the height and width of this current via its brightness. Although there are analytical relations to calculate the current height in a two-dimensional flow, these relations cannot be used to identify the width and height of a 3-D density current, due to the existence of two unknown parameters. In the present model, the height and width of the dense layer are obtained by using the boundary layer concept. Also, a comparison is made between depth averaged and characteristic variables. Then, the computed velocity and concentration profiles are compared with the experimental data and the results show good agreement between them. In this work, the ENTRAINMENT coefficient was also calculated using depth-averaged parameters and compared with the experimental data. The result has the same trend as the Ellison and Turner experiments. Present results show that the boundary layer concept can be useful in identifying the height and width of a 3-D density current.

In pumping installations, fluid transient computations are necessary to achieve safety, efficiency and economy in design and operation. In some systems, where air content and air ENTRAINMENT exist, such computations become highly inaccurate when constant wave speed is assumed. In this paper, a numerical model and a computational procedure have been developed to investigate the effects of air ENTRAINMENT on the pressure transient in pumping systems. Free gas in the fluid and cavitations at the fluid vapour pressure were modeled in the form of variable wave speed model, which was numerically solved by the method of characteristics. This model was tested for the case of pump trips due to power failures. The pressure transient results obtained by this variable wave speed model were analyzed and compared with those results obtained by constant wave speed p10deland with the experimental results of other investigators.

Experimental and numerical investigation of multihole gasoline direct injection (GDI) sprays at high injection pressure and temperature are performed. The primary objective of this study is to analyse the role of gas ENTRAINMENT and spray plume interactions on the global spray parameters like spray tip penetration, spray angles and atomization. Three-hole 90° spray cone angle and six-hole 60° spray cone angle injectors are used for current work to examine the effect of the geometry of the injector on the spray interactions. The numerical results from Reynolds Average Navier Stokes (RANS) simulations show a reasonable comparison to experiments. The simulations provide further insight to the gas ENTRAINMENT process highlights the fact that a stagnation plane is formed inside the spray cone which basically governs the semi collapse of spray that in turn affects the spray direction and cone angle.

An overview of removal and re-ENTRAINMENT of particles in turbulent flows is presented. The procedure for the direct numerical simulation (DNS) of the Navier-Stokes equation via a pseudospectral method for simulating the instantaneous fluid velocity field is described. Particle removal mechanisms in turbulent flows in a duct are examined and effects of the near-wall coherent eddy on the particle detachment and removal are discussed. The particle equation of motion, including the hydrodynamic drag and lift, as well as the Brownian and gravitational forces, are used in the analysis. The simulation results show that large size particles move away roughly perpendicular to the wall due to the action of the shear lift force. Small particles, however, follow the upward flows formed by the near wall eddies in the low speed streak regions. Thus, turbulent near wall eddies play an important role in small particle resuspension, while the lift force is an important factor for re-ENTRAINMENT of large particles. The results also suggest that small particles primarily move away from the wall in the low speed streaks, while larger particles are mostly removed in the high-speed streaks.