Royce C. Pokela’s research while affiliated with Florida State University and other places

A combined experimental and numerical study was conducted on a generic projectile configuration with low-aspect-ratio fins. The main objectives of this study were to characterize the aerodynamic behavior and validate numerical simulations for a range of Mach numbers (0.4–4) to facilitate an understanding of major flow features such as forebody and fin-generated shock waves, crossflow shear layer vortex, and fin vortex interactions. Measurements included forces and moments, surface oil flow visualization, and high-speed shadowgraph imaging. Numerical simulations were performed using the CFD++ solver. The results showed an excellent match between the experimental and numerical force and moment data. Pressure contours obtained using numerical simulations were integrated to obtain the contributions of individual components toward the total normal force on the body. Flow visualization results show a few complex and interesting flow features, such as shear layer roll-up, crossflow and fin tip vortex interactions, and shock-wave–boundary-layer interactions. The effects of vortex strength and location were analyzed to determine their contributions to the overall forces on the model. The database generated will be very useful for further validation of the numerical tool and a better understanding of vortex-dominated supersonic flows.

View Video Presentation: https://doi.org/10.2514/6.2022-0702.vid An experimental investigation involving force and moment measurements, high-speed shadowgraphy, and surface oil flow visualization was conducted to characterize the effects of longitudinal protrusions on the aerodynamic performance of a previously studied, generic axisymmetric body. Five protrusion configurations with varying ramp angles and widths were tested and compared to the generic body. Experimentation took place at the Florida State University Polysonic Wind Tunnel at Mach 2 and Mach 4 at a variety of angles of incidence and roll orientations. Quantitative results showed that increases in drag at zero incidence were in line with expectations based on the increase in axial cross-sectional area added by each protrusion configuration. It was shown that normal force, drag, and center of pressure location at angle of incidence were highly dependent on roll orientation. Control surface effectiveness was shown to be largely unchanged. Qualitative flow visualization highlighted changes to the flow-field that corresponded well with the quantitative results. Some interesting flow features were observed as well that will likely inspire additional testing in the future.

View Video Presentation: https://doi.org/10.2514/6.2021-2607.vid An experimental study involving force and moment measurements, high-speed shadowgraphy, and surface oil flow visualization was conducted on a generic axisymmetric projectile configuration with low aspect-ratio fins at the Florida State University Polysonic Wind Tunnel. The main objectives of this study were to validate numerical simulations and generate an aerodynamic database for a range of Mach numbers (0.4 to 4) and control surface deflections. Results showed an excellent match between the experimental and numerical data for the baseline configuration. Surface oil flow visualization and shadowgraph images showed a few complex and interesting flow features such as body vortex and fin interactions, shock-shock, and shock-boundary layer interactions. Control surfaces were very effective for pitch and roll control at all Mach numbers and control deflections tested. The database generated will be very useful for further validation of the numerical tool and the design of control laws.

The basic aerodynamic characteristics and control surface effectiveness of three axisymmetric projectile configurations were studied experimentally at supersonic speeds. The test configurations included a previously studied generic body with fins and augmented versions with cropped delta wings and split canards. Measurements were carried out at Mach 2 and 4 at the Florida State University Polysonic Wind Tunnel (PSWT). Control surface deflections investigated in this study included 20◦ tail fin deflections and 10◦ rear canard deflections. Flow visualization techniques using high speed shadowgraphy and surface oil flow were carried out to study the complex fluid dynamic flow features. Results indicate that the delta wing model was able to significantly improve the lift to drag ratio when compared to the baseline model. The split canard model was able to display slightly enhanced maneuverability than the baseline model with only tail fins, with a minimal addition to drag as compared to the baseline model. There is an evidence of forebody and control surface vortex interactions, which needs to be further investigated in the future.