This paper reports the results of numerical study undertaken to investigate the effect of different impeller types and rotational speed on velocity field in mixing tank. The hydrodynamic of the flow in standard mixing tank generated by two impellers, Chemineer S-4 impeller (radial flow), Pitched Blade impeller (axial flow) is studied. Using ANSYS FLUENT v15.4. is used to solve the continuity and momentum equations incorporating the RNG K-ε turbulence model with the standard wall function available in Fluent. The multiple frames of reference (MFR) model is used for impeller modeling. The results show that the mixing performance of Chemineer impeller is better than the Pitched blade impeller at the same level of rotation speed. …………………………………………………………………………………………………….... IntroductionMixing tank is one of the techniques that used and play a significant role in industrial processes to homogenize the mixture of two or more fluids/solids by using rotating impeller. The better understanding of the fluids behavior in mixing vessel may improve the performance of impeller and the mixing process. The main aims of using mixing are to improve the mass and heat transfer and to generate a homogenized mixture to minimize the settling of the particles at the bottom of the tank. A summary of some recent published works in the literature is given below. Two models were used to determine the dissipation rate and its distribution in mixing vessel. Three dimensional simulations using the commercial CFD code FLENT 6.2.16 based on the Unsteady Reynolds Averaged NaiverStokes equations (URANS) model and Large Eddy simulation (LES) model was used.

The present study investigates the effect of jet mixing techniques performed with two types of coagulants (Aluminum sulfate hydrate [Al 2 (SO 4 ) 3 .16H 2 O] and Magnesium chloride MgCl 2 ) using the polyacrylamide PAM (C 3 H 5 ) n as flocculent aid, on the flocculation. The study include two parts, the first one is the numerical analysis using ANSYS Fluent and CFX program. The second part included the experimental work in which Kaolin particles used to simulate the suspensions in natural resource water. The results indicated that the mixing process using jet mixing tank system produce uniform semi spherical shape. The image analysis provided indications that the floc with manganese chloride are compacted and dense so that it can be more suitable for direct filtration procedure.