When
Thursday, October 29, 2026, at 4:00 p.m.
Addison Plummer
PhD Candidate
Department of Aerospace & Mechanical Engineering
University of Arizona
"Experimental Investigation of Transitional Hypersonic Fin-Induced Shock Boundary Layer Interactions"
AME S212 | Zoom link
Abstract: As hypersonic flight capabilities advance, shock boundary layer interactions (SBLIs) remain a critical concern due to their prevalence and effects on structural integrity, performance and control authority. While most SBLI research has focused on nominally two-dimensional geometries for simplicity, three- dimensional interactions, such as fin-induced SBLIs, are highly relevant to flight configurations. Boundary layer transition introduces additional complexities through modifications to the interaction structure, unsteadiness and heat transfer, yet research of these effects on the SBLI remains extremely limited. This seminar will discuss the investigation of a transitional, fin-induced SBLI through a parallel approach of ground-test experiments and flight-test analysis.
Ground-test experiments were conducted in the University of Arizona Ludwieg Tube (LT5) facility at Mach 4.8 using three experimental configurations. The incoming boundary layer spectral content was analyzed to assess changes in boundary layer state with Reynolds number. Infrared thermography and mean pressure measurements characterized the global SBLI structure, revealing downstream movement of separation and changes in the reattachment region with increasing Reynolds number. Unsteady pressure measurements identified coherent low-frequency dynamics associated with the separation shock foot and rear shock, while two-point statistical analyses suggested a cyclical expansion and contraction of the separation bubble for more transitional interactions.
Complementing the ground-test experiments, the German Aerospace Center (DLR) successfully launched the STORT sounding rocket, featuring a geometrically similar fin-cylinder configuration, from the Andøya Space launch site in northern Norway on 26 June 2022. The flight spanned a wide range of Reynolds numbers and hypersonic Mach numbers, including Mach 5 conditions comparable to those in LT5 and Mach 7 conditions investigated in DLR's H2K facility. The Mach 7 portion of the trajectory corresponded to the turbulent- to-laminar transition investigated in this work. The spatiotemporal evolution of the Mach 7 SBLI during transition was investigated by tracing the pressure fluctuations at a fixed sensor location throughout the aerodynamic roll cycles, effectively mapping the transition experienced by the sensor as time progressed. A statistical classification approach identified distinct SBLI topologies, highlighting changes in pressure near reattachment and two distinct transient responses within the developing laminar region.
Bio: Addison Plummer is a PhD candidate in aerospace engineering at the University of Arizona, where she conducts research in the High-speed Aerodynamics, Unsteadiness, and Flow Control (HAUC) Laboratory under the direction of James Threadgill. Plummer received her BS in aerospace engineering from the University of Arizona in 2022 and was awarded the National Defense Science and Engineering Graduate (NDSEG) Fellowship in 2023. Her ongoing research focuses on 3D shock boundary layer interactions.