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Pipe Flow of Suspensions Containing Bubbles

World Journal of Mechanics 2018年第10期8卷 417-429页

作者： Katharina Gladbach Antonio Delgado cornelia rauh Institute of Fluid Mechanics Friedrich-Alexander-University Erlangen-Nuremberg Erlangen Germany Institute of Food Technology and Food Chemistry Technical University Berlin Berlin Germany

The steady laminar pipe flow of a suspension with a gas volume fraction ∅≤0.5 and small or intermediate bubble deformations in long, and straight sections of a circular pipe is calculated. The calculations are based on the constitutive equation that was originally derived for dilute emulsions and further developed for concentrated suspensions containing bubbles. In contrast to the literature, an analytical procedure is used to determine the solution of a pipe flow more accurately. The results are presented and discussed with respect to the Reynolds number Re and capillary number Ca. If Ca 1, a bubble suspension has a parabolic velocity profile indicating a Newtonian rheology. If Ca ≈1, two regimes of flow are observed in agreement with the literature;that is, an inner plug flow where deformation rates are low and an outer flow where deformation rates are high. These results imply that, if Ca ∅?and that, if Ca ≥1, the opposite effect occurs;that is, the Reynolds number Re increases with increasing gas volume fraction.

关键词： Pipe Flow Suspension of Bubbles Constitutive Equation Capillary Number

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3D Thermo-Fluid Dynamic Simulations of High-Speed-Extruded Starch Based Products

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Open Journal of Fluid Dynamics 2014年第1期4卷 103-114页

作者： Alessandro Cubeddu cornelia rauh Antonio Delgado Department of Food Biotechnology and Food Process Engineering Faculty III—Process Science and Engineering Berlin Institute of Technology Berlin Germany Institute of Fluid Mechanics Technical Faculty University of Erlangen-Nuremberg Erlangen Germany

This paper aims to investigate a method to perform non-isothermal flow simulations in a complex geometry for generalised Newtonian fluids. For this purpose, 3D numerical simulations of starch based products are performed. The geometry of a co-rotating twin-screw extruder is considered. Process conditions concern high rotational speed (up to 1800 rpm), different flow rates (30, 40 and 60 kg/h) and water contents (22% and 36%), for a total of 54 simulations. To cope with the geometry complexity a Mesh Superposition Technique (MST) was adopted. The pseudoplastic behaviour of the fluid is taken into account by considering viscosity as function of shear rate (Ostwaldde Waele relationship) and temperature (Arrhenius law). Simulated temperature variations are compared with measurements at same process conditions for validation. Qualitative behaviour of temperature T and shear stress ?along the screw are analysed and comparisons of different process conditions are presented. By these simulations a database is formed to develop a process control strategy for novel extruder operating points in food technology.

关键词： High Speed Extrusion Non-Isothermal Numerical Simulation Ostwald-De Waele Model

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Numerical Simulation of Foaming Processes

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World Journal of Mechanics 2017年第11期7卷 297-322页

作者： Katharina Gladbach Antonio Delgado cornelia rauh Institute for Fluid Mechanics Friedrich-Alexander-University Erlangen-Nuremberg Erlangen Germany Institute for Food Technology and Food Chemistry Technical University Berlin Berlin Germany

The literature model studied in this article describes bubble formation and growth in a highly viscous polymer liquid with support of a gaseous matter dispersed under pressure before foaming. The foam growth is induced by the application of vacuum and mass transport of volatile components dissolved in the polymer liquid. Based on this literature model, aeration processes are calculated for intermediate viscosity and low viscosity biological systems, as they are of interest for biomatter foams, in particular for food foams in industrial processes. At the end of this article, the numerical results are presented and discussed.

关键词： Foaming Process Conservation Equations Finite Difference Method Convergence Analysis Reynolds Number Newtonian Liquids

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