Topic
Pitching moment
About: Pitching moment is a research topic. Over the lifetime, 3213 publications have been published within this topic receiving 38721 citations.
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TL;DR: In this article, a transient pulse technique is used to obtain harmonic forces from a time-marching solution of the complete unsteady transonic small-perturbation potential equation.
Abstract: A transient pulse technique is used to obtain harmonic forces from a time-marching solution of the complete unsteady transonic small-perturbation potential equation. The unsteady pressures and forces acting on a model of the NACA 64A010 conventional airfoil and the MBB A-3 supercritical airfoil over a range of Mach numbers are examined in detail. Flutter calculations at constant angle of attack show a similar flutter behavior for both airfoils, except for a boundary shift in Mach number associated with a corresponding Mach number shift in the unsteady aerodynamic forces. Differences in the static aeroelastic twist behavior for the two airfoils are significant. Nomenclature a = pitch axis location, referenced to midchord, in semichords b — semichord length c — chord length c/ = lift coefficient c/h = lift coefficient due to plunge c/ = lift coefficient due to pitch c^ = moment coefficient about c/4 cm — moment coefficient due to plunge cm = moment coefficient due to pitch Cp — pressure coefficient g — structural damping coefficient h — plunge displacement in semichords hj = plunge amplitude in semichord k — reduced frequency, bul V M — freestream Mach number m = airfoil mass per unit span ra — radius of gyration, referenced to pitch axis, in semichords
34 citations
TL;DR: A series of overset grids was generated in response to the Third AIAA CFD Drag Prediction Workshop (DPW-III) which preceded the 25th Applied Aerodynamics Conference in June 2006.
Abstract: A series of overset grids was generated in response to the Third AIAA CFD Drag Prediction Workshop (DPW-III) which preceded the 25th Applied Aerodynamics Conference in June 2006. DPW-III focused on accurate drag prediction for wing/body and wing-alone configurations. The grid series built for each configuration consists of a coarse, medium, fine, and extra-fine mesh. The medium mesh is first constructed using the current state of best practices for overset grid generation. The medium mesh is then coarsened and enhanced by applying a factor of 1.5 to each (I, J, K) dimension. The resulting set of parametrically equivalent grids increase in size by a factor of roughly 3.5 from one level to the next denser level. Computational fluid dynamics simulations were performed on the overset grids using two different Reynolds-averaged Navier-Stokes flow solvers: CFL3D and OVERFLOW. The results were postprocessed using Richardson extrapolation to approximate grid-converged values of lift, drag, pitching moment, and angle of attack at the design condition. This technique appears to work well if the solution does not contain large regions of separated flow (similar to that seen in the DLR-F6 results) and appropriate grid densities are selected. The extra-fine grid data helped to establish asymptotic grid convergence for both the OVERFLOW FX2B wing/body results and the OVERFLOW DPW-W1/W2 wing-alone results. More CFL3D data are needed to establish grid convergence trends. The medium grid was used beyond the grid convergence study by running each configuration at several angles of attack so drag polars and lift/pitching moment curves could be evaluated. The alpha sweep results are used to compare data across configurations as well as across flow solvers. With the exception of the wing/body drag polar, the two codes compare well qualitatively showing consistent incremental trends and similar wing pressure comparisons.
34 citations
10 Jun 2009
TL;DR: A modified nonlinear longitudinal model for an air-breathing hypersonic vehicle and the design of an L1 adaptive controller for it with guaranteed robustness and transient performance for system's input and output signals is presented.
Abstract: This paper presents a modified nonlinear longitudinal model for an air-breathing hypersonic vehicle and the design of an L 1 adaptive controller for it. It is assumed that the mid-fuselage is a rigid-body, while the aft-fuselage is linearly elastic, and a rigid all-movable elevator is fixed at the end of the aft-fuselage. In the resulting mathematical model, the pitching moment depends not only on the control surface position, but also on the rate and acceleration of the control surface motion. For compensation of the modeling uncertainties including the flexible dynamics, the L 1 adaptive control architecture is considered in this paper. It has a low-pass filter in the feedback loop allowing for arbitrarily fast adaptation with guaranteed robustness and transient performance for system's input and output signals. Simulation results demonstrate the benefits of the method.
34 citations
01 Sep 2018
TL;DR: In this article, a method is presented to model the incompressible, attached, unsteady lift and pitching moment acting on a thin three-dimensional wing in the time domain.
Abstract: A method is presented to model the incompressible, attached, unsteady lift and pitching moment acting on a thin three-dimensional wing in the time domain The model is based on the combination of Wagner theory and lifting line theory through the unsteady Kutta–Joukowski theorem The results are a set of closed-form linear ordinary differential equations that can be solved analytically or using a Runge–Kutta–Fehlberg algorithm The method is validated against numerical predictions from an unsteady vortex lattice method for rectangular and tapered wings undergoing step or oscillatory changes in plunge or pitch Further validation is demonstrated on an aeroelastic test case of a rigid rectangular finite wing with pitch and plunge degrees of freedom
33 citations
TL;DR: In this paper, a dimensionless parameter that quantifies the amount of aerodynamic damping for vehicle subjects to pitching oscillation is proposed, and two vehicle models with different stability characteristics were created to verify the parameter.
33 citations