Pitching moment

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

6 Development of Micro Air Vehicles with in-Flight Adaptive Wing

Abstract: A = aspect ratio (b2/S) b = wing span CD = drag coefficient = D/(0.5ρV 2S) CL = lift coefficient = L/(0.5ρV 2S) CL max = maximum lift coefficient CLα = lift-curve slope, 1/deg CM = pitching-moment coefficient about quarter-chord point of the root chord, = M/(0.5ρV 2S c) c0 = root chord measured along the longitudinal axis of the wing c = mean aerodynamic chord measured along the longitudinal axis D = drag force d = position of the maximum reflex hi = height of the maximum inverse camber hz = camber height at z cross section in spanwise direction h0 = camber height at the root of the wing L = lift force M = pitching moment about quarter-chord point of the root chord m = mass Re = mean-aerodynamic-chord Reynolds number S = wing planform area TP = thrust force

Aeroelasticity of the PrandtlPlane: Body Freedom Flutter, Freeplay, and Limit Cycle Oscillation

Abstract: Aeroelasticity of PrandtlPlane configurations is a yet unexplored field. The overconstrained structural system and the mutual aerodynamic interference of the wings enhance the complexity of the aeroelastic response. In this work the aeroelastic behavior of several models based on wing system of 250-seat PrandtlPlane design is studied. When an aluminum version of the structure is considered, flutter is associated with a coalescence of the first two elastic modes, the first being characterized by a classic upward bending of both wings, and the second one being associated with an out-of-phase bending of the two wings and tilting of the lateral joint. Analyses show that energy is injected in the structure mainly at the tip of the front wing, close to the aileron. Effects of freeplay of mobile surfaces are evaluated, showing how, in some cases, an increase in the flutter speed is observed. When flutter analyses are repeated considering the configuration free to pitch and plunge, flutter speed does increase due to a particular interaction between rigid-body pitching and elastic modes. Several of the above findings are demonstrated on more detailed structural models considering also the local stiffness distribution, and taking also into consideration compressibility effects. When composite materials are employed, flutter issues are completely overcome.

A general method for determining the aerodynamic characteristics of fan-in-wing configurations. volume 1. theory and application

Abstract: : A general method is presented for the determination of aerodynamic characteristics of fan-in-wing configurations by means of incompressible potential-flow theory. The method is applicable to wings, flapped or unflapped, and to a wide variety of other potential-flow boundary-value problems. Arbitrary wing and inlet geometry, fan inflow distribution, thrust vectoring, angle of attack, angle of yaw, and flight speeds from hover through transition can be treated. The theoretical model is completely three dimensional, with no linearization of boundary conditions. The calculated results include pressure distributions, lift, induced drag and side force, pitching moment, rolling moment and yawing moment. The numerical potential-flow solution is obtained with source and vortex distributions on the boundary surfaces. The representation is composed of small, constant-strength source sheet panels distributed over the exterior wing surfaces, internal vortex filaments which emanate from the wing trailing edge to provide circulation and to produce the trailing vortex sheet, and a vortex lattice across the fan face and along the periphery of the fan efflux. Source and vortex strengths are obtained by satisfying boundary conditions at discrete points on the boundary surfaces. Velocities and surface pressures are calculated from the induced effects of the source and vortex distributions. Internal fan loads, based on pressure and momentum relations across the fan and an assumed fan exit flow distribution, are added to integrated wing surface pressures to determine total forces and moments on a fan-in-wing configuration. The method was programmed for use with a high- speed digital computer.

Modeling and Closed Loop Flight Testing of a Fixed Wing Micro Air Vehicle

Abstract: This paper presents the nonlinear six degrees of freedom dynamic modeling of a fixed wing micro air vehicle. The static derivatives of the micro air vehicle are obtained through the wind tunnel testing. The propeller effects on the lift, drag, pitching moment and side force are quantified through wind tunnel testing. The dynamic derivatives are obtained through empirical relations available in the literature. The trim conditions are computed for a straight and constant altitude flight condition. The linearized longitudinal and lateral state space models are obtained about trim conditions. The variations in short period mode, phugoid mode, Dutch roll mode, roll subsidence mode and spiral mode with respect to different trim operating conditions is presented. A stabilizing static output feedback controller is designed using the obtained model. Successful closed loop flight trials are conducted with the static output feedback controller.