Pitching moment

About: Pitching moment is a research topic. Over the lifetime, 3213 publications have been published within this topic receiving 38721 citations.

Limit-Cycle Oscillations of a Typical Airfoil in Transonic Flow

Abstract: Using an inviscid flow computational-fluid-dynamic model and a harmonic balance flow solver, a parametric investigation of how structural-inertial parameters and freestream Mach number of a transonic flow affect the limitcycle oscillation characteristics of a typical two-degree-of-freedom transonic airfoil configuration is presented. The computational efficiency of the harmonic balance aerodynamic model allows a much more thorough exploration of the parameter range than has been possible previously. Nomenclature a = nondimensional location of airfoil elastic axis, a = e/b b, c = semichord and chord, respectively ¯ cl, ¯ cm = nondimensional coefficients of lift and moment about elastic axis for simple harmonic motion e = location of airfoil elastic axis, measured positive aft of airfoil midchord h, ¯ h = airfoil plunge degree of freedom and its nondimensional amplitude, respectively; ¯ h is identical to h/b Iα = second moment of inertia about elastic axis L = aerodynamic lift Kh, Kα = airfoil plunge stiffness and torsional stiffness about elastic axis, respectively M = freestream Mach number Me.a. = aerodynamic moment about elastic axis m = airfoil sectional mass rα = radius of gyration of airfoil about elastic axis, r 2 α is identical to Iα/mb 2

A Multisegment Dynamic Model of Ski Jumping

Abstract: This paper presents a planar, four-segment, dynamic model for the flight mechanics of a ski jumper. The model consists of skis, legs, torso and head, and arms. Inputs include net joint torques that are used to vary the relative body configurations of the jumper during flight. The model also relies on aerodynamic data from previous wind tunnel tests that incorporate the effects of varying body configuration and orientation on lift, drag, and pitching moment. A symbolic manipulation program, “Macsyma,” is used to derive the equations of motion automatically. Experimental body segment orientation data during the flight phase are presented for three ski jumpers which show how jumpers of varying ability differ in flight and demonstrate the need for a more complex analytical model than that previously presented in the literature. Simulations are presented that qualitatively match the measured trajectory for a good jumper. The model can be used as a basis for the study of optimal jumper behavior in flight which ...

Dynamics of Slender Bodies Separating from Rectangular Cavities

Abstract: Vertical and pitching motions (two degrees of freedom) of a thin body of revolution separating from a rectangular cavity in a subsonic stream are investigated using combined asymptotic and numerical methods. The analysis is based on explicit analytical solutions for the lift force and pitching moment obtained in our previous studies. Body trajectory dependencies on initial conditions, body parameters, and freestream velocity are studied. The problem is divided into three phases of the motion. In phase 1, the body is inside the cavity. In phase 2, the body crosses the shear layer, and in phase 3, the body is outside the cavity. For phases 1 and 3, analytical solutions of the body dynamics are obtained for typical cases. This analysis provides insight into the separation process and identifies governing lumped nondimensional parameters relevant to the body dynamics as well providing a model that can provide quick, computationally non-intensive estimates of store separation with a personal computer. The role of the nondimensional parameters in the dynamic stability eigenvalues is identified and found particularly useful in this connection. These parameters implicitly contain the effect of the shear layer

Prediction of vortex breakdown and longitudinal characteristics of swept slender planforms

Abstract: A method is presented to predict high-angle-of-attack, longitudinal aerodynamic characteristics of slender wing planforms in incompressible e ow. A semiempirical approach is used to predict the location of vortex breakdown and its variation with incidence. Breakdown predictions are then coupled to vortex lift expressions based on the leading-edge suction analogy. A correction is used to account for the attenuation of vortex suction after vortex breakdown, allowing prediction of lift, drag, and pitching moment at high angles of attack. Comparisons are made with a variety of planforms, with encouraging agreement between theory and experiment being demonstrated.

Variable area, variable camber wing for aircraft

Abstract: A mechanism is provided for both extending the chord of a wing by more than seventy percent and for increasing the camber of the wing without creating the high pitching moment characteristics of conventional high lift wing systems. These advantageous capabilities are accomplished by constructing forward and aft wing sections which cover the wing box beam and form a high wing loading cruise flight wing. The sections can be extended and deflected to uncover the wing box beam and form a greatly increased area to lower the wing loading and an increased camber with low pitching moment to provide high lift for short take-off and landing.