Effect of tank geometry on flow characteristics and energy consumption in mechanical mixing

¹ AGH University of Krakow, Faculty of Civil Engineering and Resource Management, Mickiewicza 30, 30-059 Kraków, Poland
² AGH University of Krakow, Faculty of Energy and Fuels, Mickiewicza 30, 30-059 Kraków, Poland

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 12 March 2026

Abstract

Mixing, understood as a process in which the mutual movement of particles within a given medium leads to homogeneity, is one of the most common processes used across various technologies and industries. It is used in pharmaceuticals, petrochemicals, metallurgy, mineral processing, the food industry and more. Substances in different states of matter and with varying physical or chemical properties can undergo mixing. Mixing may occur in single-phase, two-phase, or multiphase systems. The method used depends on the desired outcome and the required time scale. Additionally, the following factors must be considered: the geometry of the mixing tank, the viscosity of the mixed phases, temperature, fluid density, and the shape of the impeller. These parameters determine mixing efficiency and energy consumption. The optimal design of impeller geometry for tanks with simple and easy-to-manufacture shapes (e.g. cylindrical or cubic) continues to attract the interest of researchers. An alternative approach in modelling, particularly in turbulent flows, involves modifying the tank geometry by introducing baffles to stabilize the flow. The main objectives of this research is to characterise fluid flow and evaluate the energy consumption of mixing in a mechanically agitated cylindrical tank, both with and without baffles. The effect of baffle size on fluid flow and mixing, as well as the required agitator power, was also investigated. Mixing efficiency was evaluated using flow velocity from Particle Image Velocimetry and Computational Fluid Dynamics simulations, while the required power was determined form precise torque measurements. The experiments were conducted under variable hydrodynamic conditions for several impeller design. Results indicate that the presence of baffles affects the fluid flow characteristics inside the tank by altering the pumping efficiency (Qr) and the power number (Np), as well as mixing efficiency E