On the characterization of the boundary-layer flow on a rotating slender cone using PIV*

This work builds on previous investigations at KTH (e.g., Kato et al., 2019, PRF and Kato et al., 2021, JFM) on the development of boundary-layer instabilities and transition to turbulence on rotating cones in still fluid. There is still a limited understanding of the topology and evolution of instabilities in the slender cone case. Therefore, for this study, experiments were conducted on the setup (30-degree half-apex cone angle) presented by Kato et al (2021, JFM). The boundary-layer flow's topology and the instabilities that lead to transition are characterized using planar particle image velocimetry (PIV) for different rotational speeds. The time-average flow fields are compared to the corrected analytical solution proposed by Segalini and Camarri (2019, PRF) for rotating cones. In turn, the instantaneous velocity fields are analyzed in detail to characterize the topological evolution of the vortical structures presented in the classical flow visualizations by Kobayashi and Izumi (1983, JFM). In addition, the velocity measurements are supported by high-speed flow visualization.