Summary

Cylindrical reservoirs under rotary motion are widely used in several industries, such as chemical and petrochemical, metallurgical, pharmaceutical, food and even for wastewater treatment. In some of these technological areas, the development of new products and materials commonly comprises mixing processes, which take advantage of rotary motion to reduce non-uniformities in terms of composition, temperature and other properties. However, the complexity of the resulting flow field implies that most of the research related to this area is only intended to the establishment of empirical correlations for specific applications. In fact, the lack of a detailed physical understanding of these flows turns the design of optimal systems and products into a very difficult task. This paper presents the results of numerical simulations of turbulent flow in a cylindrical container under alternating rotary motion, with a triangular propeller attached to the bottom surface. Experimental results are also obtained to supplement the study and to validate the numerical model. The main physical phenomena involved are analyzed, with reference to the influence of operating variables (geometry, rotation speed and level of liquid) upon important parameters of the mixing processes, such as flow velocity field, turbulence kinetic energy, flow shear strain and resistive torque. It is observed that the reservoir with four bumps on the bottom surface generates the greatest flow velocities. Although the geometry with two bumps provides the highest turbulence levels, it is found to return the lowest resistive torque. Moreover, it is confirmed that higher angular speeds increase flow velocity, turbulence, shear rate and also the required torque to induce the flow. Finally, the present study shows that there exists an optimal fluid level for the mixing process.

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