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Stability and transition experiments are conducted in the Arizona State University Unsteady Wind Tunnel on a 45° swept airfoil. The pressure gradient is designed so that transition and stability are purely crossflow-dominated. Flow visualization and hot-wire measurements show that the development of the crossflow vortices is influenced by roughness near (not at) the attachment-line. Comparisons of transition location are made between a painted surface (distributed 9 μm peaks and valleys on the surface), a machine-polished surface (0.5 μm rms finish), and a hand-polished surface (0.25 μm rms finish). Then, isolated 6 - 9 μm roughness elements are placed near the attachment line on the airfoil surface under conditions of the final polish (0.25 μm rms). These elements amplify a centered stationary crossflow vortex and its neighbors, resulting in localized early transition. The diameter and height of these roughness elements are varied in a systematic manner.

Three-dimensional boundary-layer experiments are currently being conducted on a 45° swept wing in the Arizona State University Unsteady Wind Tunnel. Crossflow-dominated transition is produced via a model with contoured end liners to simulate infinite swept-wing flow. Fixed-wavelength stationary and travelling crossflow vortices are observed. The stationary vortex wavelengths vary with Reynolds number as predicted by linear-stability theory but with observed wavelengths which are about 25% smaller than theoretically predicted. The frequencies of the most-amplified moving waves are in agreement with linear-stability theory; travelling waves at higher frequencies than predicted are also observed. These higher-frequency waves may be harmonics of the primary crossflow waves generated by a parametric resonance phenomena. Boundary-layer profiles measured at several spanwise locations show streamwise disturbance profiles characteristic of the crossflow instability.

This paper investigates the utilization of Low Earth Orbit (LEO) satellites for vehicle localization and conducts a comparative analysis with traditional Global Navigation Satellite Systems (GNSS)-based methods. With the rise of LEO satellite constellations, such as Starlink, LEO-based vehicle localization may offer solutions to GNSS-related challenges. With a large number of satellites and short communication distance, the LEO-based method has great potential to improve accuracy, reduce warm-up time, and provide a robust localization solution for vehicle applications. In this paper, a dedicated LEO satellite simulator is presented, adaptable to various LEO constellations, making it relevant for evolving technologies beyond older LEO systems like Orbcomm or Iridium. The simulator includes satellite trajectory generation, observable satellite identification, and vehicle localization.