Thesis Defense - Veli Can Coşar (MSME)

Veli Can Coşar – B.Sc. Mechanical Engineering

Assoc. Prof. Özgür Ertunç – Advisor

Date: 28.12.2022

Time: 10:00

Location: AB2 G03

Investigation of Atomization of Droplets in Turbulent Flows

Assoc. Prof. Özgür Ertunç, Özyeğin University

Asst. Prof. Altuğ Başol, Özyeğin University

Prof. Dr. Kerem Pekkan, Koc University

Abstract:

Droplets are used in many important technologies, in the form of either single droplets or sprays. Examples include car engines, combustion chambers of jet engines, rocket engines, metal particle production, surface coatings, surface cooling, surface reactions, inhalation, inhalation, agricultural spraying, and inkjet printing technology. For example, in car, jet, and rocket engines, the droplets are exposed to strong turbulent flow, and they are divided into smaller pieces (atomization). It is very important to understand the relationship of atomization with the turbulence parameters for the development of relevant technologies and the creation of new technologies. The properties of the liquid, the speed of the droplet, and the characteristics of turbulence are effective in the atomization of the liquid drop in the turbulent gas environment. Due to the eddies in the flow, transient forces occur on the droplets. The droplet becomes unstable by the action of these forces and by the interaction of the inner viscous and surface tension forces. Factors related to atomization should be expressed in dimensionless numbers. For example, the Weber number of the droplet, the Reynolds number of the droplet, the Reynolds number of the turbulence, the Ohnesorge number, the ratio of the length scales of the turbulence (Kolmogorov, Taylor and Integral length scales) to the diameter of the drop, the ratio of the average drop size resulting from the atomization to the length scales of the turbulence and the ratio of the time of atomization to the time scales of turbulence are examples of the most important of these dimensionless parameters. In addition, the interaction between turbulence and droplet is only defined by the surface tension of the droplet, density, and dissipation rate of the flow around it. There should be more parameters as described as examples of dimensionless numbers.  To have a better understanding of the atomization process, an isotropic homogenous turbulent flow environment is prepared with a cubic-shaped wind tunnel. Due to avoid the effect of droplet coalescence and collapsing in the breakup process, one droplet is exposed to isotropic turbulence and its breakup is examined. The parameters of turbulent flow are changed within a systematically controlled by changing the speed or velocity profile of the propellers.

Bio:

Veli Can received his bachelor’s degree in Mechanical Engineering at Ozyegin University in 2019. He had worked on Ozu Rover, Electrobuggy (electric car), cooling of PV cells with PCM materials with Mr. Arık, different wind tunnels for creating Hurricane Ivan, and investigation of droplet breakup behavior in isotropic and homogenous turbulence with Mr. Ertunç. He is an M.Sc. Student in Ozyegin University under the supervision of Assist. Prof. Özgür Ertunç. He is studying turbulent flows, multiphase flows, droplet breakup and atomization.