Hydrodynamics of Liquid Flow Through Screens and Screen-Type Static Mixers

Abstract

An approach for predicting the spatial variation of the energy dissipation rate downstream of a screen is proposed in this article. It is based on extending the use of the homogeneous and isotropic turbulence decay equation to the very thin anisotropic region adjacent to the screen. Whereas the decay exponent and origin were kept constant in conformity with other previous investigations, the decay coefficient was slightly altered. This approach was found to be capable of predicting the experimental energy dissipation data obtained using liquid flow through screens and screen-type static mixers reasonably well over a wide range of design and operating conditions.

Turbulently flowing liquid–liquid dispersions. Part I: Drop breakage and coalescence

“…The fact that the model predicts the experimental observations with high accuracy is an additional indication that the hydrodynamic model responsible for predicting the spatial variation of the energy dissipation rate [23] throughout the contactor works quite well and yields good estimates of ε since good agreements between simulations and experimental data are also to a large extent based on good predictions of the turbulent energy dissipation rate [3].…”

“…The hydrodynamic factors affecting the performance of screen type static mixers were recently analyzed by Azizi and Al Taweel [23] who proposed that the turbulence decay profile behind a grid be divided into two regions, a region of constant high energy dissipation rate prevalent over a certain distance downstream of the grid, and a region of fast decay where the homogenous isotropic turbulence decay equation applies. Using this representation for modeling the spatial variation of the energy dissipation rate (Fig.…”

“…Additional information concerning the values of these various parameters and the proposed approach for predicting the spatial variation of the energy dissipation rate downstream of a screen are reported elsewhere [23]. dispersed phase droplets (e.g.…”

The physics and sediment containment phenomenon of a silt screen

“…When the porosity was 33 % or more, the coefficient was found to be a function of the porosity. As suggested by Azizi and Taweel (2011), for screens with small porosity, high turbulent energy was generated downstream of the screens, and the turbulence dissipated relatively slowly.…”

“…is the decay coefficient, n is the decay exponent, x refers to the downstream location of interest,   Table 2.4 shows the suggested values of the coefficients in Equation 2.25 from published studies (adapted from Azizi and Taweel, 2011). In these studies, the screens were installed vertically in the water and normal to the approaching flow.…”