A 3D CFD numerical study of the bubble generation process into a bubble Tjunction generator and its comparison with experimental data: Part I

This work presents a 3D numerical study of the bubble generation process into a bubble generator obtained with the commercial Computational Fluid Dynamics solver ANSYS Fluent v15.0.7, and its comparison with experimental data reproducing the same conditions. The bubble generator is formed by two perpendicular capillaries in which liquid and gas are injected at perpendicular directions into a 1 mm internal diameter capillary T-junction with a total length of 10 mm. The fluids used in experiments and CFD simulations are air and water, both of them considered incompressible and isothermal, at a room temperature of 25º. A total of 23 different cases are studied for different injection conditions, and results between numerical simulations and experiments are compared. In this first part of the analysis, we focus on the flow pattern regimes and the dynamics of the bubble generation process. In addition to the new numerical simulations presented here, a new model has been used to predict the bubble generation frequency and tested with both experimental and numerical data. Results on bubble generation frequency are also presented by means of the non-dimensional Strouhal number. Same types of patterns, bubble and slug flow regimes, are obtained in simulations and experiments. In order to perform an exhaustive validation and comparison of numerical simulations with experimental data, several parameters have been selected: bubble velocity, volumetric void fraction, bubble generation frequency, Strouhal number and bubble equivalent diameter. Numerical simulations agree qualitatively, but not always quantitatively, with experimental results.Peer ReviewedPostprint (published version

Influence of contact angle boundary condition on CFD simulation of T-Junction

“This is a post-peer-review, pre-copyedit version of an article published in Microgravity Science and Technology. The final authenticated version is available online at: https://doi.org/10.1007/s12217-018-9605-x ”.In this work, we study the influence of the contact angle boundary condition on 3D CFD simulations of the bubble generation process occurring in a capillary T-junction. Numerical simulations have been performed with the commercial Computational Fluid Dynamics solver ANSYS Fluent v15.0.7. Experimental results serve as a reference to validate numerical results for four independent parameters: the bubble generation frequency, volume, velocity and length. CFD simulations accurately reproduce experimental results both from qualitative and quantitative points of view. Numerical results are very sensitive to the gas-liquid-wall contact angle boundary conditions, confirming that this is a fundamental parameter to obtain accurate CFD results for simulations of this kind of problems.Peer ReviewedPostprint (published version

Studies on lanthanide shift reagents

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Arrival trade-offs considering total flight and passenger delays and fairness

This paper studies trade-offs between flight and passenger delays and fairness when assigning delay pre-tactically (on-ground at origin airport) due to reduced airport capacity. The paper also defines and analyses efficiency-fairness trade- offs. The optimisation model is based on the ground holding problem and uses various objective functions: total delay for flights (considering reactionary delay), total delay for passengers (considering outbound connections), and deviation from a Ration By Schedule solution (to get a measure of the fairness of the solution). The scenario considered takes place at Paris Charles de Gaulle airport, a busy European hub airport, and includes realistic values of traffic