Lift Characteristics of Trapezoidal Fins

• Connor Waltman, Mechanical Engineering, University of Delaware

• Tyler Van Buren, Mechanical Engineering, University of Delaware

Movable control surfaces, such as fins, are critical to the stability, trajectory, and maneuverability of high-speed aerospace vehicles operating across diverse fluid mediums. While the fundamental aerodynamic mechanics of lift generation are well documented, optimizing the geometric parameters of these control surfaces for dynamic flight environments remains a highly complex engineering challenge. This computational fluid dynamics study systematically examines the effect of planform sweep angle on the aerodynamic control authority of trapezoidal fins. Sectional lift coefficients were computationally extracted at multiple spanwise stations for five distinct sweep angles (0°, 15°, 30°, 45°, and 57.75°). These simulations were conducted across a dynamic maneuver envelope with Angles of Attack (AoA) ranging from 0° to 15°, and fluid velocities spanning subsonic, transonic, and supersonic regimes (Mach 0.5 to 1.5). By integrating these local lift distributions, the total resultant lift force and spanwise center of pressure were calculated for each geometric configuration. The data demonstrates a consistent, near-linear degradation in total resultant lift force as the sweep angle increases. Crucially, normalizing these lift forces revealed that this aerodynamic penalty is universally geometric and remains entirely Mach-independent. Furthermore, the analysis highlighted that highly swept fins induce a strong spanwise inward migration of the center of pressure due to outboard flow separation. Ultimately, these findings dictate that sweep angle serves as a primary, scalable design lever for tuning control authority, allowing aerospace designers to precisely balance the necessary tradeoffs between raw lift generation, structural root bending moments, and dynamic stability in fin-stabilized launch vehicles.