Accession Number : AD0715110

Title :   On Resonance Instability for Finned Configurations Having Non-Linear Aerodynamic Properties.

Descriptive Note : Technical rept.,

Corporate Author : NAVAL WEAPONS LAB DAHLGREN VA

Personal Author(s) : Clare,Thomas A.

Report Date : OCT 1970

Pagination or Media Count : 51

Abstract : An approximate solution is presented for the angular motion, at and near resonance, of finned configurations (with small aerodynamic asymmetries) having non-linear aerodynamic properties. An extension of the 'Method of Slowly Varying Parameters' (or 'Averaging Method') is used to solve the simultaneous pitch and yaw equations of motion, in terms of 'amplitude-rate' equations, at the resonance point. Included in this analysis are the non-linear variations of the restoring, damping, and Magnus moments with angle of attack. Both transient and steady state solutions are obtained. A 'detuning' of the rolling velocity from its resonant value is performed to yield a solution in the critical near-resonant region. This result is shown to give rise to the well-known 'resonance jump' in the steady state case. Finally, allowing the detuning parameter to vary with time enables an examination of the non-linear catastrophic yaw problem in which both the rolling velocity and the roll orientation angle may vary with time. In this regard, the effects of a non-linear variation of the induced side moment with angle of attack are determined. The accuracy of these solutions is evaluated by comparison with exact numerical integrations of the equations of motion. (Author)

Descriptors :   (*FINS, AERODYNAMIC CHARACTERISTICS), AERODYNAMIC CONFIGURATIONS, PITCH(MOTION), YAW, EQUATIONS OF MOTION, ROLL, ANGLE OF ATTACK, APPROXIMATION(MATHEMATICS)

Subject Categories : Aerodynamics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE