Numerical simulation of electrically conducting jet flow in a straight duct under longitudinal homogeneous magnetic field. - In: Physics of fluids, ISSN 1089-7666, Bd. 31 (2019), 1, 014108, insges. 15 S.
Spatial evolution of electrically conducting jet flow at a supercritical Reynolds number, entering a duct filled with the liquid of the same physical properties, is studied by direct numerical simulations for the case of a streamwise uniform magnetic field. In contrast to the case of a transverse field, here the jet mean velocity does not interact with the streamwise field, and only the turbulent fluctuations of the flow are influenced and suppressed by the field. In this case, the jet saves its energy and has a tendency to spread at much larger distances. Therefore, one interesting and important property of this setup is the flow stabilization, i.e., transition to turbulence can be largely delayed due to the stabilizing effect of the magnetic field. This occurs in the presence of moderate magnetic fields. At strong magnetic fields, the second instability evolves-the jet profile becomes unsteady due to the traveling waves, which propagate along the jet while not interacting with the field. These traveling waves are generated by the interaction of secondary radial flows and magnetic field.
https://doi.org/10.1063/1.5062617
Mathematical modeling of friction stir welding considering dry and viscous friction. - In: Applied mathematical modelling, Bd. 67 (2019), S. 1-8
Corrigendum: Bd. 77 (2020), part 1, page 981
https://doi.org/10.1016/j.apm.2018.10.014
Thermocapillary convection during hydrogen evolution at microelectrodes. - In: Electrochimica acta, ISSN 1873-3859, Bd. 297 (2019), S. 929-940
The origin of strong electrolyte flow during water electrolysis is investigated, that arises at the interface between electrolyte and hydrogen bubbles evolving at microelectrodes. This Marangoni convection was unveiled only recently (Yang et al., PCCP, 2018, [1]) and is supposed to be driven by shear stress at the gas-liquid interface caused by thermal and concentration gradients. The present work firstly allows a quantification of the thermocapillary effect and discusses further contributions to the Marangoni convection which may arise also from the electrocapillary effect. Hydrogen gas bubbles were electrolytically generated at a horizontal Pt microelectrode in a 1MH2SO4 solution. Simultaneous measurements of the velocity and the temperature field of the electrolyte close to the bubble interface were performed by means of particle tracking velocimetry and luminescent lifetime imaging. Additionally, corresponding numerical simulations of the temperature distribution in the cell and the electrolyte flow resulting from thermocapillary stress only were performed. The results confirm significant Ohmic heating near the micro-electrode and a strong flow driven along the interface away from the microelectrode. The results further show an excellent match between simulation and experiment for both the velocity and the temperature field within the wedge-like electrolyte volume at the bubble foot close to the electrode, thus indicating the thermocapillary effect as the major driving mechanism of the convection. Further away from the microelectrode, but still below the bubble equator, however, quantitative differences between experiment and simulation appear in the velocity field, whereas the temperature gradient still matches well. Thus, additional effects must act on the interface, which are not yet included in the present simulation. The detailed discussion tends to rule out solution-based effects, generally referred to as solutal effects, whereas electrocapillary effects are likely to play a role. Finally, the thermocapillary effect is found to exert a force on the bubble which is retarding its departure from the electrode.
https://doi.org/10.1016/j.electacta.2018.11.187
Studies on the simultaneous measurement of velocity and temperature fields in Rayleigh-Bénard convection using thermochromic liquid crystals. - In: 5th International Conference on Experimental Fluid Mechanics, (2018), S. 62-68
https://doi.org/10.18726/2018_2
3D temperature and velocity measurements in microfluidics. - In: 5th International Conference on Experimental Fluid Mechanics, (2018), S. 518-523
https://doi.org/10.18726/2018_2
On the difficulties for reliable measurements of convection in large aspect ratio Rayleigh-Bénard cells. - In: 5th International Conference on Experimental Fluid Mechanics, (2018), S. 716-721
https://doi.org/10.18726/2018_2
Detection and measurement of bubbles in gas-liquid two-phase flow using magnetic fields. - In: Turbulence, heat and mass transfer 9, (2018), S. 401-404
Instrumentierung eines Prüfstandes für Batteriekühlanlagen elektrischer Stadtbusse :
Instrumentation of a battery thermal management system test bench for electric city busses. - In: Experimentelle Strömungsmechanik, 2018, Seite 38.1-38.6
Factors of influence on the image of thermochromic liquid crystals for simultaneous measurements of velocities and temperatures :
Einflussfaktoren auf die Abbildung thermochromer Flüssigkristalle zur simultanen Geschwindigkeits- und Temperaturmessung. - In: Experimentelle Strömungsmechanik, 2018, Seite 40.1-40.10
Influence of local parasitic near-wall flows in thermal storage tanks :
Einfluss lokaler parasitärer Wandschichtströmungen in thermischen Energiespeichern. - In: Experimentelle Strömungsmechanik, 2018, Seite 33.1-33.7