Experimental Identification of Bistable Flow States on the Space Launch System at Liftoff Conditions

Le résumé fourni par la source

View Video Presentation: https://doi.org/10.2514/6.2022-3665.vid Time-averaged global force and moment measurements in wind tunnel tests can obscure complex flow dynamics, including bistability phenomena. This paper presents a detailed analysis into the potential cause of previously unobserved discrepancies among repeat runs during the 2021 14- by 22-Foot Subsonic Tunnel test of the Space Launch System. During the test, it was observed that liftoff configuration repeatability was not as strong as expected when compared to previous tests. These discrepancies occurred between wind azimuth angles of approximately 150 degrees and 220 degrees, as well as between 330 degrees and 30 degrees. After ruling out common confounding factors such as instrumentation hysteresis and temperature, it was hypothesized that the lack of repeatability was caused by the Coandă effect producing a bistable flow state at different locations between the cylindrical rocket centerbody and solid rocket boosters during the acquisition of data. Evidence to support this hypothesis is provided in this paper in the form of time-averaged force and moment coefficient data, time-dependent force and moment coefficient data, and still images from smoke flow and tuft flow visualization runs.

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