An Experimental Setup to Characterize Boundary Layer Asymmetry on a Spinning Projectile Using Magnetic Resonance Velocimetry
Current CFD models fail to accurately predict boundary layer asymmetry on spin-stabilized projectiles, particularly in the transonic and subsonic flow regimes. Consequently, these models cannot accurately characterize the Magnus moment, a key component in aerodynamic behavior. This work seeks to capture boundary layer thickness asymmetry, an indicator of Magnus effects, around a spinning projectile using Magnetic Resonance Velocimetry (MRV). The MRV technique allows for collection of three-dimensional, non-intrusive, high-resolution velocity field measurements that can be used for comparison to and validation of current computational models. In this experiment, a modified M80 projectile was designed to thicken the hydrodynamic boundary layer for technique validation. The scaled projectile was mounted in a custom-designed test rig at a 2° nosedown angle of attack. The apparatus rotated the projectile at various spin rates in a constant flow of copper-sulfate solution. Initial results revealed azimuthal differences in boundary layer thickness for three different cases — no spin, nominal spin, and double spin — particularly in the tapered rear (boattail) region of the projectile. The introduction of spin shifted the boundary layer thickness in the spin direction resulting in lateral boundary layer asymmetry in the boattail region, a phenomenon that likely affects the stability of spin-stabilized projectiles.
Siegel, NW, Schlenker, AP, Sullivan, KD, Valdez, IL, Snow, CP, Benson, MJ, Van Poppel, BP, Elkins, CJ, & Rodebaugh, GP. "An Experimental Setup to Characterize Boundary Layer Asymmetry on a Spinning Projectile Using Magnetic Resonance Velocimetry." Proceedings of the ASME 2018 International Mechanical Engineering Congress and Exposition. Volume 7: Fluids Engineering. Pittsburgh, Pennsylvania, USA. November 9–15, 2018. V007T09A002. ASME. https://doi.org/10.1115/IMECE2018-87472