MEchanics GAthering –MEGA- Seminar: What Rocket Turbopumps and Rabbits Have in Common: Logistic Dynamics in Inducer Cavitation Instabilities

Abstract: Cavitation instabilities in liquid rocket turbopump inducers—especially local types—have long been a persistent challenge, manifesting in various forms depending on the operating conditions. Despite extensive studies, their physical mechanisms have remained elusive. In this talk, the blade-to-blade interaction, which is the effect of one blade's cavity on the flow field encountered by the following blade, is newly proposed as a unified physical mechansim underlying these various instabilities. Examination of the flow field under these instabilities reveals that this interaction exhibits nonlinear behavior analogous to the logistic map popularized by Robert May's demographic model. Such nonlinearity leads to bifurcations in the cavity response, where local interactions among adjacent blades evolve into annulus-wide instability patterns. Further analysis shows that the emergence and transition of these instability modes can be interpreted within the same framework that governs bifurcation in the logistic map, providing an example of the physical and (Mitchell Feigenbaum's) mathematical universality of nonlinear dynamical system.
 

Bio: Youngkuk Yoon is a Visiting Research Fellow at the University of Cambridge and a Senior Researcher at the AI Institute, Seoul National University. He received his B.S. and Ph.D. degrees in Mechanical Engineering from Seoul National University. His current research interests cover aerodynamics in gas turbine engines and sustainable aviation.