Aerodynamic Asymmetry Research Articles

A Comparison of Barley, Oats, Sorghum and Wheat in the Production of the Fatty Liver and Kidney Syndrome

In this paper, the effect of aerodynamic asymmetries on the flutter characteristics of turbomachinery blades is investigated. Specifically, the present method is used to study the effect of leading edge blending in loaded and unloaded rotors. The unsteady aerodynamic response of the blades to self-excited vibrations is modeled using a harmonic balance method, which allows one to model the entire wheel using complex periodic boundary conditions and a computational grid spanning a single sector (symmetry group). This reduces the computational and memory requirements dramatically compared to similar time-accurate analyses. It is shown that alternate blending degrades the stability of a loaded rotor whereas it improves the stability of an unloaded rotor. On the other hand, when blends are spaced five blades apart their effect is less pronounced.

An exploratory study of the roll behavior of ablating cones

and d) are zero at roll rate. 3) Small trim angles of attack (fr < 0.25°), which can be produced by principal axis inclination angles of similar magnitude, may seriously degrade the performance of re-entry vehicles that have mass asymmetries. 4) Effects of inertia asymmetries on the angular and rolling motions of ballistic re-entry vehicles may be misinterpreted as the effects of mass and aerodynamic asymmetries.

An analytical technique for studying the anomalous roll behavior of re-entry vehicles

Anomalous roll behavior of a spinning re-entry vehicle is examined in detail for the case of a vehicle having a simple compound asymmetry consisting of a lateral center-of-gravity offset combined with an aerodynamic trim angle of attack. The analysis is made utilizing a fast analytical roll response program developed from the linearized equations of motion of a spinning vehicle. The results show that persistent roll resonance is obtained at first resonance with the minimum aerodynamic asymmetry if the asymmetry creates a trim force that lies in-plane with the center-of-gravity offset. A criterion is developed which defines this minimum in-plane aerodynamic asymmetry for the special case of a constant flightpath entry into an exponential atmosphere with constant aerodynamic coefficients. A suggested method of treating Mach-number-dependent aerodynamic coefficients is also presented. Selected six-degree-of-freedom trajectory calculations are used to verify important analytical results.

Impact dispersion due to mass and aerodynamic asymmetries.

a,b = semi-major and semi-minor axes of ellipse, ft CA = axial force coefficient Cm0} Cn0 = asymmetric moment coefficients about the y and z axes, respectively . = normal force coefficient slope, = reference diameter for coefficients, ft = resultant force normal to centerline, Ib Fz = forces in directions of y and z axes, respectively, Ib = acceleration of gravity, ft/sec = altitude, ft = impulse, Ib-sec = roll moment of inertia, slug-ft = roll rate, rad/sec = ambient pressure, lb/ft = dynamic pressure, lb/ft = reference area for aerodynamic coefficients, ft = temperature, °R = time, sec = velocity, ft/sec = weight, Ib = total trim angle of attack at p = 0, deg == flight path angle, deg static margin of stability, ft; x* = Ax/d center-of-gravity off set along y axis, ft ; y*~Ay/d angle defining a fixed direction relative to FO, rad resultant change in direction of V, rad $ = angle defining the direction of F relative to FG, rad ^ = angle defining the direction of F relative to the y axis, rad

Effects on roll rate of mass and aerodynamic asymmetries for ballistic re-entry bodies

Symmetrical ballistic-type re-entry bodies have been observed to exhibit erratic roll behavior during flight. This unpredicted behavior can have adverse effects on performance by producing excessive loads and dispersion. To explain the observed phenomena, roll characteristics produced by several types of mass and aerodynamic asymmetries were determined by numerical solution of the equations of motion and by a simplified analytical solution. The asymmetries considered included lateral displacement of the center of gravity and center of pressure, inclination of the principal longitudinal axis to the body geometrical center line, unequal pitch and yaw moment of inertia about the principal axes, and asymmetric aerodynamic moments. All types of asymmetries, except for the inclination of the principal axis, produced significant roll torque, and various combinations of these asymmetries produced roll-rate histories similar to those observed on flight records.