Webinaire – Theoretical and numerical analysis of the evaporation of mono- and multicomponent single fuel droplets_ _Alejandro Millán-Merino, Eduardo Fernández-Tarrazo and __Mario Sánchez-Sanz

Mario SANCHEZ SANZ
mssanz@ing.uc3m.es

Associate Professor
Fluid Mechanics Research Group
Universidad Carlos III de Madrid

_Title: Theoretical and numerical analysis of the evaporation of mono- and multicomponent single fuel droplets_

_Alejandro Millán-Merino, Eduardo Fernández-Tarrazo and __Mario Sánchez-Sanz _

Single fuel droplet vaporization, with special attention to the case of ethanol, is considered in this study. First, we showed, using an order-of-magnitude analysis and detailed unsteady simulations, that the commonly used quasi-steady assumption is not suitable for an accurate description of the liquid phase during the evaporation process. Second, we demonstrated that an increase in the relative importance of radiation explains the departures of the evaporation rate from the d2-law observed experimentally when sufficiently large droplets – initial radius above 0.25 mm – evaporated in ambient temperatures around 800 K. The multicomponent formulation included here, in which the physical properties of both liquid and gas phases depend on the concentration of the different species involved, was validated by comparing our numerical results with experimental data of ethanol, _n_-heptane, ethanol-water and _n_-dodecane-_n_-hexadecane droplets available in the literature. Because of its technological relevance, we dedicated special attention to the effect of the droplet water content and ambient humidity on the evaporation time of ethanol droplets. Our computations showed higher vaporization rates with increasing ambient humidity as a consequence of the extra heat generated during the condensation of moisture on the droplet surface.

Webinaire FTC: Effect of free surface on the hydrodynamics of plates in cross-flow, Mr Sukruth Satheesh.

Effect of free surface on the hydrodynamics of plates in cross-flow
Cylinders and flat plates oriented normal to the flow are typical bluff bodies, characterized with large regions of separated flow and a significant pressure drag component. The study of forces generated by bluff bodies has been one of the oldest problems in fluid mechanics, studied initially using free streamline theory and the modified hodograph plane theory. These canonical bodies are also used extensively in several industrial sectors, ranging from oil & gas, transportation to energy. There is a good amount of literature on the interaction between cylinders and boundaries, but very little information is available related to the interaction between flat plates and deformable boundaries. This lack of information is even more apparent when plate aspect ratio is considered as well. With this in mind, this talk focuses on hydrodynamics of plates in cross-flow near the free surface over a range of aspect ratios, Reynolds numbers, and submergence depths. Later, a few strategies for drag control, namely structural flexibility and strategic porosity are also presented.