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    Eddy diffusivity of particles in turbulent flow in rough channels
    (Elsevier Sci Ltd, 2002) Altunbas, A; Kelbaliyev, G; Ceylan, K
    The eddy diffusivity coefficient of particles depends on the flow characteristics and on the physical properties of the particles. Experimental data and theoretical considerations suggest that the ratio of the eddy diffusion coefficient of particles (D-TP) to the eddy diffusion coefficient of fluid (D-T) is dependent mainly on the friction velocity of fluid (U-*), the sedimentation velocity of the particles (V-s), the Reynolds number (Re) of the flow and also the relative roughness of channel.(epsilon/D). It is shown here that this relation among these parameters may be represented as D-TP/D-T = mu(R) proportional to (U-*(m)/V-S)(n), where m and n are empirical constants. Some new empirical relationships are proposed for the eddy diffusion coefficient of particles in the turbulent flow in vertical or horizontal channels. The results compare favorably with experimental data from the literature. (C) 2002 Elsevier Science Ltd. All rights reserved.
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    A new model for estimation of drag force in the flow of Newtonian fluids around rigid or deformable particles
    (Elsevier Science Sa, 2001) Ceylan, K; Altunbas, A; Kelbaliyev, G
    A number of relationships are given in the literature for estimation of the drag coefficients; however, most of these are applicable only for a narrow range of Reynolds number (Re). Some new empirical relationships are proposed in this study to estimate the drag coefficients in the flow of Newtonian liquids around the solid spherical or cylindrical particles and the deformable particles. An approximation series approach is used to develop these empirical relationships. It is shown that the proposed relationships can be applicable for the solid spherical or cylindrical particles in the range of 0.1 > Re > 10(6), and for the deformable particles (drops and bubbles) in the range of 0.1 > Re > 10(4). The predicted coefficients are in a good agreement with the experimental data given in the literature. (C) 2001 Elsevier Science B.V. All rights reserved.