Steady and Unsteady Maneuvering Forces and Moments on Slender Bodies

Forces and moments have been measured on slender bodies in both static angle conditions as well as rapid time-dependent large amplitude maneuvers with the Dynamic Pitch Plunge Roll (DyPPiR) apparatus.

Lateral and transversal forces as well as all three moments have been measured at static angles of attack and sideslip and unsteady pitch ramp maneuvers at a fixed point of rotation at the quarter length of the body. The two bodies are the DARPA Suboff generic submarine shape and a non-Body-of-Revolution scalene ellipsoid with a constant cross-section midbody.

An analytical two-mode equation has been shown to accurately describe the normal force and pitch moment as well as side force and yaw moment for the ellipsoid body. It is based on the observation that the center of pressure for the cross-flow contribution is at a fixed location. For the Suboff body, this assumption is invalid. Unsteady forces and moments can be measured to a very small magnitude of uncertainty and were found to differ from steady forces and moments at the time-instantaneous flow angle during the motion.