Droplets dynamics

The simulations were also performed under same conditions as the case of Fig. 10 but for higher impact velocities. The simulated-droplet dynamics and heat-transfer rate at the solid surface at different impact velocities are given in Ge and Fan (2005). 

The final consideration for the droplet dynamics comes from the momentum equation applied to a single droplet, as illustrated in Figure 12.5 ... 

The solution of the gas flow and temperature fields in the nearnozzle region (as described in the previous subsection), along with process parameters, thermophysical properties, and atomizer geometry parameters, were used as inputs for this liquid metal breakup model to calculate the liquid film and sheet characteristics, primary and secondary breakup, as well as droplet dynamics and cooling. The trajectories and temperatures of droplets were calculated until the onset of secondary breakup, the onset of solidification, or the attainment of the computational domain boundary. This procedure was repeated for all droplet size classes. Finally, the droplets were numerically sieved and the droplet size distribution was determined. 

RD.I. Eletcher and D.I. Horsup Droplet Dynamics in Water-in-Oil Microemulsions and Macroemulsions Stabilized by Non-Ionic Surfactants. J. Chem. Soc. Earaday Trans. I 88, 855 (1992). 

As discussed earlier, the particle/droplet dynamics can be significantly modified by timing the fuel injection to be in- or out-of-phase with the large-scale vortex structures. To explore if timed fuel injection could alter the stability characteristics, the flow was forced at the quarter-wave mode of the inlet and droplet injection was timed to be in- or out-of-phase with the forcing. Results from these simulations show that the pressure fluctuations at the quarter-wave mode of the inlet can indeed be amplified or attenuated depending on the phasing of the droplet injection. 

The behaviour of droplets, as a whole, is a complex area of interest to researchers in a variety of fields, such as combustion, aerosol science and spray technology, to mention a few. Recently, Frohn and Roth have written about many aspects of droplet dynamics and the reader is referred to their book as a good introduction to the subject. However, from an inkjet point of view the researcher is primarily interested in the behaviour of droplets on the substrate, from the moment when the droplet lands to the droplet s end-state. In the first instance, the researcher strives to ensure that droplets land in their specified locations and remain there. Then, they try to control the droplets behaviour in order to obtain the desired morphology. The aim of this chapter is to discuss the lifetime of inkjet-produced droplets from the moment of their impact with the substrate to the moment when the final feature is obtained, which is typically by evaporation of the droplet s carrier solvent or by the solidification of said solvent. 

The population balance approach is employed for the description of droplet dynamics in various flow fields. A significant advantage of the method is that a vehicle is provided to include the details of the breakage and coalescence processes in terms of the physical parameters and conditions of operation. A predictive multidimensional particle distribution theory is at hand which, in the case of well-defined droplet processes, can be employed for a priori prediction of the form and the magnitude of the particle size distribution. The physical parameters which affect the form... 

It is observed, even in the partial solution to the problem, that realistic models of the droplet coalescence and breakage processes as discussed in Section V,D,2 have yet to be employed. A parallel development has occurred. The work is currently at the point where the realistic model of the droplet dynamics can be applied to the pertinent problems of extent of reaction and solute depletion in dispersions. The success of this effort would permit the researcher and designer to predict dispersed-phase reactor performance from fundamental properties of the dispersion, operation conditions of the vessel, and knowledge of the intrinsic kinetics. 

Venter, A., Sojka, P.E., and Cooks, R.G., Droplet dynamics and ionization mechanisms in desorption electrospray ionization mass spectrometry, Anal. Chem., 78(24), 8549, 2006. 

Fletcher, P.D.I. and Horsup, D.I. (1992) Droplet dynamics in water-in-oil microemulsions and macroemulsions stabilized by non-ionic surfactants - correlation of measured rates with monolayer bending elasticity. /. Chem. Soc. Faraday Trans., 88, 855-864. 

Smirnov Your approach of using water droplets in cold flow to mimic the droplet dynamics in reacting flow will not be accurate. 

S. Q. Zhou, R. K. Shah, and K. A. Tagavi, Advances in Film Condensation including Surface Tension Effect in Extended Surface Passages, in Fundamentals of Bubble and Droplet Dynamics Phase Change and Two-Phase Flow, E. Ulucakli (ed.), ASME HTD-Vol. 342, pp. 173-185,1997. 

Jia, W. and H.-H. Qiu (2003). Experimental investigation of droplet dynamics and heat transfer in spray cooling. Experimental Thermal and Fluid Science 27(7) 829-838. 

Ikeda, Y., Nakajima, T., and Kurihara, N. (1997) Size-classified droplet dynamics and its slip velocity variation of air-assist injectra- spray. SAE Papta 970632. 

Droplet deformation and collision are also important features in the intermediate regime. In addition, in the intermediate region, the droplet loading could be severe. The variations in the local liquid-phase volume fraction also become important and should be considered in order to capture the droplet dynamics correctly. A robust algorithm capable of addressing all numerical issues related to spray modeling is necessary. 

Droplet dynamics are usually simulated using a Lagrangian point-particle model. It is assumed that (1) the density of the droplets is much greater than that of the carrier... 

P. S. Grant, B. Cantor, L. Katgerman Modelling of droplet dynamic and thermal histories during spray forming - I. Individual droplet behaviour, Acta Metall. Mater. 41, 3097-3108... 

Cristini, V., Tan, Y. C. (2004). Theory and numerical simulation of droplet dynamics in complex flows-a review. Lab on a Chip, 4, 257-264. 

Droplet-Based Lab-on-Chip Devices Droplet Dynamics in Microchaimels Droplet Evaporation... 

Droplet dynamics in microchannels refer to the description of motion and deformation of droplets in capillaries or conduits of hydraulic diameters of the orders of microns. 

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