Stefan Puttinger

Investigation of droplet size distribution for liquid-liquid emulsions in Taylor-Couette flows

ABSTRACT In this paper, we investigate oil-in-water emulsions in a Taylor-Couette flow. A high-speed camera was employed to record the formation of those emulsions, and image processing was used to obtain the diameter of the droplets. No surfactants were added in order to study the pure effect of the fluid dynamical forces on the droplets. The results for three different oil-in-water emulsions show that the Sauter mean diameter considerably depends on the local shear rate and the material properties and that the droplet size distribution follows a log-normal distribution. We, therefore, propose to express the Sauter mean diameter normalized by Prandtl mixing length in terms of a correlation, which is based on the Kolmogorov turbulence theory. This correlation subsequently depends on the local shear rate and the material properties such as viscosity, density, and interfacial tension. The predictions of the correlation show fairly good agreement with the experimental measurement the Sauter mean diameter. Finally, comparing the predictions of the correlation to the data presented by Eskin et al. [Chem. Eng. Sci. 161 36–47; 2017] shows excellent agreement in the case, where the droplets are larger than the Kolmogorov length scale. GRAPHICAL ABSTRACT

A Glance on Turbulence Modelling in Simulating Bubble Stirred Ladle Flow

Bubble stirred ladle flow is studied by means of multiphase simulations. In this study the role of turbulence modelling is discussed. Numerical simulation results reveal that turbulence modelling is crucial for the prediction of both, local and macroscopic flow characteristics. Consequently, a thorough and experimentally substantiated turbulence modelling is indispensable for picturing metallurgical transport phenomena.ZusammenfassungGasblasen gerührte Pfannenströmungen werden mithilfe Mehrphasensimulationen untersucht. In dieser Studie wird insbesondere die Rolle der Turbulenzmodellierung diskutiert. Numerische Simulationsergebnisse zeigen, dass die Wahl des Turbulenzmodells für die Vorhersage des sowohl lokalen als auch makroskopischen Strömungsverhaltens entscheidend ist. Folglich ist eine gründliche und experimentell abgesicherte Turbulenzmodellierung für die Vorhersage von metallurgischen Transportphänomenen unverzichtbar.