2024-09-26 
Lithuanian Energy Institute, Breslaujos g. 3, Kaunas. 202-AK aud. Author, Institution: Justas Šereika, Lithuanian Energy Institute
Dissertation title: Investigation of the influence of active and passive control methods on the dynamics and structure of separated single-phase flow
Science area, field of science: Technological Sciences, Energetics and Power Engineering, T006.
Defense of the dissertation: 2024-09-26, 10:00 a.m., Lithuanian Energy Institute, 202-AK auditorium, Breslaujos st. 3, Kaunas, Lithuania.
Scientific Supervisors:
- Dr. Nerijus Pedišius (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering, T006)
September 2020 – February 2024 - Senior Researcher Dr. Paulius Vilkinis (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering, T006)
March 2024 – August 2024
Dissertation Defense Board of Energetics and Power Engineering Science Field:
- Chairperson – Assoc. Prof. Dr. Robertas Poškas (Kaunas University of Technology, Technological Sciences, Energetics and Power Engineering, T006);
- Prof. Dr. Algirdas Maknickas (Vilnius Gediminas Technical University, Technological Sciences, Mechanical Engineering, T009);
- Prof. Dr. Hab. Gintautas Miliauskas (Kaunas University of Technology, Technological Sciences, Energetics and Power Engineering, T006);
- Prof. Dr. Martin Obligado (Ecole Centrale de Lille, France Technological Sciences, Energetics and Power Engineering, T006);
- Assoc. Prof. Dr. Linas Paukštaitis (Kaunas University of Technology, Technological Sciences, Energetics and Power Engineering, T006).
The doctoral dissertation is available online J. Šereika el. dissertation (PDF) and at the Library of Kaunas University of Technology (Gedimino st. 50, Kaunas) and at Lithuanian Energy Institute (Breslaujos st. 3, Kaunas).
Annotation:
The need for knowledge on the separated flow dynamics and structure in channels with sudden cross-section changes is decided by wide practical application while designing various reactors, combustion, mixing, flow and meter measuring chambers. The problem is closely related to the flow control problems, where the influence of inlet, mixing and outlet conditions on mass and heat transfer processes must be solved. The main goal of this work is to investigate the flow controlled by pulsations, roughness elements and geometrical parameters using experimental and numerical methods, while identifying the parameters determining the recirculation zone dynamics and the separated flow structure in cavities. In this work, the advanced flow visualization methods (micro and macroPIV) applied in the experiments are combined with numerical modelling, allowing to simultaneously observe the average and instantaneous velocity distribution and determine the mechanism of changes in the flow structure and its influence on the mass transfer process efficiency. The research results and analysis presented in the dissertation complement the fundamental knowledge on flow control methods and their influence on the flow structure and the recirculation zone length variation regularities. The revealed regularities in the recirculation zone development during the pulsation cycle are linked to the separated flow average structure and allow to explain the behaviour of additional vortices. The influence of the pulsatile flow on turbulence intensity has been established, which reveals the origin of velocity fluctuations, while the established dependency of velocity distribution and pressure loss on the roughness elements configuration provides an opportunity to define the factors determining the efficiency of flow control.