Public Defense of Doctoral Thesis at the ETSI

Date: Thursday, July 2023.

Time: 10:00 AM

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

Doctoral candidate Paula García Geijo will publicly defend her doctoral thesis entitled "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 droplet impact on solid substrates can be classified into: i) the analysis of expansion, known as spreading, and subsequent retraction (if any), and ii) the determination of the critical velocity at which the droplet breaks down into smaller droplets (a phenomenon called splashing).

Thus, after a brief introduction to 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 low-viscosity liquid droplets upon impact on smooth, inclined surfaces. This process is entirely similar to the impact of a droplet following an inclined trajectory with respect to a horizontal solid substrate. In these situations, the expansion process develops asymmetries that have not been quantified to date.

Chapters three and four are interrelated. They present a comprehensive analysis of the splashing process on rough surfaces, both hydrophilic and hydrophobic, and construct a diagram that allows the determination of the splash transition velocity at atmospheric pressure as a function of the liquid's material properties, the static contact angle, and the relative surface roughness. Therefore, this thesis provides a complete description of the splash transition on generic surfaces, which is of clear technological interest.