Public Defense of Doctoral Thesis at the ETSI

Date: Thursday, July 2023.

Time: 10.00 am

Place: Professor Juan Larrañeta Room, Higher Technical School of Engineering of the University of Seville.

Doctoral student Paula García Geijo will publicly defend her doctoral thesis titled "Experimental and Theoretical Study about Drop Impact on Inclined Surfaces and Substrates with Different Roughness and Wettability", which has been directed by professors José Manuel Gordillo Arias de Saavedra and Guillame Riboux Acher of the Department of Aerospace Engineering and Fluid Mechanics of the Higher Technical School of Engineering of the University of Seville.

This thesis addresses three aspects related to the impact of droplets on smooth and rough surfaces, both hydrophilic and hydrophobic. The study of the impact of drops on solid substrates can be classified into: i) the analysis of the expansion, known as spreading, and subsequent retraction (if any), and ii) the determination of the critical speed from which the drop breaks up into smaller ones (a phenomenon called splashing).

Thus, after a brief introduction of the phenomena to be analyzed, the second chapter of this thesis will be dedicated to the study of the temporal evolution of the expansion of drops of low viscosity liquids upon impact on smooth and inclined surfaces, this process being totally similar to the impact of a drop forming an inclined path with respect to a horizontal solid substrate. In these situations, the expansion process develops asymmetries that had not been quantified to date.

The third and fourth chapters are related to each other. In them, an exhaustive analysis of the splashing process is carried out on rough surfaces, both hydrophilic and hydrophobic, and it is possible to construct a diagram that allows determining the speed of transition to the splash at atmospheric pressure depending on the material properties of the liquid, the angle of static contact, as well as the relative surface roughness. Therefore, this thesis provides a complete description of the transition to splash on generic surfaces that has a clear technological interest.