@misc{BarzantnyHamedeMajchrzyketal., author = {Barzantny, Marcel and Hamede, Mohammed Hussein and Majchrzyk, MichaƂ and Merbold, Sebastian and Egbers, Christoph and Kostowski, Wojciech}, title = {Experimental investigation of the flow characteristics driving the Ranque-Hilsch phenomenon}, series = {International journal of heat and mass transfer}, volume = {253}, journal = {International journal of heat and mass transfer}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0017-9310}, doi = {10.1016/j.ijheatmasstransfer.2025.127543}, pages = {1 -- 14}, abstract = {The Ranque-Hilsch vortex tube (RHVT) is a device that separates a pressurized inlet stream into two decompressed streams of different temperature, flowing to the so-called hot and cold outlets. In this study, the flow structures within the vortex tube were examined qualitatively. The examination considered both compressible and incompressible fluids, using pressurized air and water as working fluids. A parametric study was conducted, in which the fluid inlet pressure and the vortex tube length were varied. Three tubes, with the same diameter but differing lengths (100, 180, and 240 mm) were utilized. The flow inside the tube was investigated using a flow visualization technique, which was employed in a variety of configurations and setups contingent on the specific fluid conditions under examination. The visualization process required the use of aerosol injection in the case of air, and kalliroscope particles in the case of water investigation. The research enabled the visualization of the flow structure within the vortex tube, thereby significantly advancing the comprehension of the underlying physical processes. The findings of the experimental research demonstrated the existence of phenomena of considerable scientific value. The internal vortex and its spatial and temporal structure observed in the RHVT were consistent with literature data. This was achieved despite the so-far established consensus that this type of research is challenging and not entirely reliable. In the course of water-based investigation, the cavitation phenomenon was observed in the vicinity of the internal vortex. This discovery is likely to be the first of its kind and may contribute significantly to the advancement of research on the Ranque-Hilsch phenomenon.}, language = {en} } @misc{HamedeSliavinMotuzetal., author = {Hamede, Mohammed Hussein and Sliavin, Yaraslau and Motuz, Vasyl and Egbers, Christoph}, title = {The effect of flow initial conditions and geometry on the saturation of the thermo-electrohydrodynamic instability within microgravity conditions}, series = {Physics of fluids}, volume = {37}, journal = {Physics of fluids}, number = {9}, publisher = {AIP Publishing}, address = {College Park, Maryland}, doi = {10.1063/5.0287547}, pages = {1 -- 10}, abstract = {The present study investigates the thermo-electrohydrodynamic-induced convection in a dielectric fluid confined between two concentric differentially heated cylinders under microgravity conditions through experimental means. The experiments were conducted during parabolic flight campaigns. In the present study, our primary focus was on the saturation of perturbations induced by thermo-electrohydrodynamic instability. The effect of initial flow conditions on perturbation growth rates is examined when entering the microgravity phase. Furthermore, a series of experimental setups with varied lengths and aspect ratios were considered to investigate the impact of geometry on flow behavior. The present study quantitatively investigated the flow using particle image velocimetry in the meridional and radial-azimuthal planes. Furthermore, direct measurements were taken of the global response of the flow, in this case heat transfer, using a heat flux sensor attached to the outer cylinder wall.}, language = {en} }