Abstract
An experimental method for the determination of the pitch damping moment coefficient sum Cmq+Cmα˙ in a wind tunnel at transonic and low supersonic Mach numbers is developed. With support interference being a major issue for dynamic tests at these velocities, a minimum interference wire suspension approach is used. The motion of the wind tunnel model is restricted to a single-degree of freedom pitching oscillation through the geometry of the support system. A statistical evaluation procedure allows the simultaneous evaluation of multiple tests to increase confidence in the results. The influence of the wires as well as nonlinear effects are accounted for. The method is validated in an extensive test series at Mach numbers ranging from 0.6 to 2.0. Two reference missile models—the Basic Finner and the Army-Navy Spinner Rocket (ANSR)—are used. The results agree very well with CFD calculations throughout the transonic range. In comparison to free-flight tests the accuracy is significantly improved and result uncertainties are reduced by an order of magnitude.
Highlights
The pitch damping moment coefficient sum Cmq + Cmαis a major factor for a projectile’s dynamic stability in flight [1]
The present study aims to develop a method for the experimental determination of Cmq + Cmαthat is suitable for slender bodies such as missile configurations, and can be used in a wind tunnel with a limited cross-section at transonic speeds
Overall 263 wind-on tests have been conducted with the Basic Finner reference model
Summary
The pitch damping moment coefficient sum Cmq + Cmαis a major factor for a projectile’s dynamic stability in flight [1]. Its knowledge early on in the design process is advantageous with regard to flight behavior and control system design. This is true for flight at transonic Mach numbers where aerodynamic forces and moments can undergo significant changes for small velocity deviations. Various methods for its experimental determination in a wind tunnel setup have been developed [4,5], but are often not well suited for testing projectile configurations at transonic Mach numbers. The main reason for this is support interferences due to the combination of small model sizes and the larger sting support necessary for the dynamic tests, which result in large measurement uncertainties. Methods like the forced-oscillation technique [8] that use a traditional sting support depend on the availability of a sufficiently large wind tunnel
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