Drop dispensing in a viscous outer liquid

The formation and detachment of Newtonian drops in viscous external liquids is investigated. A global analysis of two necking processes is presented in order to highlight the behavior of such thinning phenomena, when controlled either by inertia or by viscous effects. Moving detached droplets in an immiscible outer liquid were studied in terms of velocity and drop-travel distance. Theoretical predictions are proposed and compared with experimental data for the volume of the drop and for the subsequent dynamics that follow after detachment. Our investigations point out that the drop rapidly achieves constant velocity, the value of it being in a satisfactory agreement with the model. Both the influence of the flow rate and that of the material properties on drop volume are pursued

Unforced Rayleigh instability of an immersed liquid jet

Motivated by the occurrence of the injection of liquids in various technical processes, we study the capillary instability of a liquid jet surrounded by another liquid. The study focuses on the natural developing Rayleigh instability, hence without an imposed perturbation. We also point out the influence of viscosity on the main drop diameter, resulted after jet breakup, and on the breakup length itself. Modifications brought by a decrease of the capillary nozzle are also emphasized for a particular case

Unforced Rayleigh instability of an immersed liquid jet

Motivated by the occurrence of the injection of liquids in various technical processes, we study the capillary instability of a liquid jet surrounded by another liquid. The study focuses on the natural developing Rayleigh instability, hence without an imposed perturbation. We also point out the influence of viscosity on the main drop diameter, resulted after jet breakup, and on the breakup length itself. Modifications brought by a decrease of the capillary nozzle are also emphasized for a particular case

Coalescence Phenomenon of Immersed Jets

The present paper investigates the immersed jet behavior. Jets of water and water - glycerol mixtures are studied. Two jets are placed in contact. The jets collision creates flow patterns depending on velocity and liquid properties; the two jets can remain in contact, but separated (noncoalesced) for low flow rates, or coalesced in a single larger jet. The resulting jet can exhibit breakup. The breakup phenomenon of a single jet is investigated and breakup length is measured. The influence of the liquid properties on the phenomena evolution is evidenced by varying the concentration of glycerol in the glycerol - water solution

Up-conversion emission in transition metal and lanthanide co-doped systems: dimer sensitization revisited

Lanthanide (Ln) co-doped transition metal (TM) upconversion (UC) co-doped systems are being intensively investigated for their exciting applications in photonics, bioimaging, and luminescence thermometry. The presence of TM, such as Mo6 + /W6 +, Mn2 +, or Fe3 + determines significant changes in Ln UC emission, such as intensity enhancement, colour modulation, and even the alteration of the photon order. The current mechanism assumes a ground-state absorption/excited-state absorption (ESA/GSA) in TM-Yb dimer followed by direct energy transfer to Er/Tm excited states. We revisit this mechanism by addressing two issues that remain ignored: a dynamical approach to the investigation of the upconversion mechanism and the intrinsic chemical complexity of co-doped TM, Ln systems. To this aim, we employ a pulsed, excitation variable laser across a complete set of UC measurements, such as the emission and excitation spectra and emission decays and analyze multiple grains with transmission electron microscopy (TEM). In the Mo co-doped garnet, the results sustain the co-existence of Mo-free garnet and Mo oxide impurity. In this Mo oxide, the Er upconversion emission properties are fully explained by a relatively efficient sequential Yb to Er upconversion process, with no contribution from Yb-Mo dimer sensitization.ISSN:2045-232