Pitching moment

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

Low-speed aerodynamic characteristics of a highly swept, untwisted uncambered arrow wing

Abstract: An investigation was conducted in the Langley 4- by 7-Meter Tunnel to provide a detailed study of wing pressure distributions and forces and moments acting on a highly swept arrow-wing model at low Mach numbers (0.25). A limited investigation of the effect of spoilers at several locations was also conducted. Analysis of the pressure data shows that for the configuration with undeflected leading edges, vortex separation occurs on the outboard wing panel for angles of attack on the order of only 3 deg, whereas conventional leading-edge separation occurs at a nondimensional semispan station of 0.654 for the same incidence angle. The pressure data further show that vortex separation exists at wing stations more inboard for angles of attack on the order of 7 deg and that these vortices move inboard and forward with increasing angle of attack. The force and moment data show the expected nonlinear increments in lift and pitching moment and the increased drag associated with the vortex separation. The pressure data and corresponding force and moment data confirm that deflecting the entire wing leading edge uniformly to 30 deg is effective in forestalling the onset of flow separation to angles of attack greater than 8.6 deg; however, the inboard portion of the leading edge is overdeflected. The investigation further identifies the contribution of the trailing-edge flap deflection to the leading-edge upwash fields.

Dynamic Stall of an Oscillating Airfoil in Turbulent Flow Using Time Dependent Navier-Stokes Solver

Abstract: The unsteady compressible Reynolds time averaged Navier-Stokes equations which include an algebraic turbulence model have been applied to an oscillating airfoil in turbulent flow. The governing equations are written in conservation form in a body fitted coordinate system and solved using an Alternating Direction Implicit (ADI) procedure. Results are presented for turbulent flow about NACA 0012 and the ONERA-CAMBRE airfoils whose incidence oscillate from 0 degree to 20 degrees. The effects of reduced frequency and leading edge camber on the normal force and pitching moment coefficients are analyzed and qualitatively good agreement has been obtained with experimental data.

Analysis of Twin Turboprop Aircraft Whirl-Flutter Stability Boundaries

Abstract: a = distance from propeller to engine attachment, m Bhh = modal damping matrix cmq = aerodynamic derivative (pitching moment due to pitching) cm = aerodynamic derivative (pitching moment due to yaw angle) cnr = aerodynamic derivative (yawing moment due to yawing) cn = aerodynamic derivative (yawing moment due to pitch angle) cyq = aerodynamic derivative (side force due to pitching) cy = aerodynamic derivative (side force due to pitch angle) cy = aerodynamic derivative (side force due to yaw angle) czr = aerodynamic derivative (vertical force due to yawing) cz = aerodynamic derivative (vertical force due to pitch angle) cz = aerodynamic derivative (vertical force due to yaw angle) D = structural damping matrix D = aerodynamic damping matrix DP = propeller diameter, m FP = propeller disc area, m 2 fFL = flutter frequency, Hz fH = natural frequency of engine’s lateral vibrations, Hz fHdnws = natural frequency of engine’s lateral vibrations including downwash effect, Hz fV = natural frequency of engine’s vertical vibrations, Hz fVdnws = natural frequency of engine’s vertical vibrations including downwash effect, Hz f0 = natural frequency (in general), Hz G = gyroscopic matrix g = total artificial damping of vibrating system H = flight altitude, m HISA = flight altitude according to the International Standard Atmosphere, m Im = imaginary part Jx = mass moment of inertia about x axis, kg m Jy = mass moment of inertia about y axis, kg m Jz = mass moment of inertia about z axis, kg m j = imaginary unit K = structural stiffness matrix K = aerodynamic stiffness matrix KH = rotational stiffness of engine attachment in yaw (used for optimization), N m=rad Khh = modal stiffness matrix KV = rotational stiffness of engine attachment in pitch (used for optimization), N m=rad K = rotational stiffness of engine attachment in pitch, N m=rad K = rotational stiffness of engine attachment in yaw, N m=rad k = reduced frequency M = mass matrix MD = design maximum Mach number Mhh = modal mass matrix MY;P = aerodynamic moment around lateral axis—in propeller disc plane, N m MZ;P = aerodynamic moment around vertical axis—in propeller disc plane, N m mFUEL = fuel loading, % PY = propeller aerodynamic force in lateral direction at propeller disc plane, N PZ = propeller aerodynamic force in vertical direction at propeller disc plane, N p = eigenvalue Qhh = complex aerodynamic matrix q1 = flow dynamic pressure, Pa R = propeller diameter, m Re = real part t = time, s VD = design maximum speed, m s 1 VFL = flutter speed, m s 1 VTAS = flight speed (true airspeed), m s 1 V1 = flight speed, m s 1 w1 = downwash in vertical plane induced by aerodynamic forces, m s 1 w2 = downwash in horizontal plane induced by aerodynamic forces, m s 1 X = deflected x axis of propeller rotation x = undeflected x axis, x-direction distance, m ~ x = intermediate axis xi = design variable Y = deflected y axis y = undeflected y axis, y-direction distance, m Z = deflected z axis Received 2 February 2011; revision received 28 February 2012; accepted for publication 8May 2012. Copyright © 2012 byAeronautical Research and Test Institute, Prague. Published by theAmerican Institute ofAeronautics and Astronautics, Inc., with permission. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0021-8669/12 and $10.00 in correspondence with the CCC. Senior Scientist, Strength of Structures Department, Beranovych 130. Associate Fellow AIAA. JOURNAL OF AIRCRAFT Vol. 49, No. 6, November–December 2012

Assessment of an Unstructured-Grid Method for Predicting Aerodynamic Performance of Jet Flaps

Abstract: The application of a Computational Fluid Dynamics tool to a jet flap control effector on an elliptical airfoil-section wing was investigated. The study utilized the Tetrahedral Unstructured Software System developed at NASA Langley Research Center. The Reynolds-averaged Navier-Stokes flow solver code used was USM3D. The CFD-based jet flap simulations were compared to experimental results from a wind tunnel test conducted at the NASA Langley Transonic Dynamics Tunnel. The wind tunnel model consisted of a six percent thick elliptical airfoil with a modified trailing edge. The jet flap was located at 95% chord and exited at 90 degrees to the lower surface. The experimental model was designed to promote two-dimensional flow across the wing. It was found that the CFD simulation had to model the three-dimensional geometry of the experiment in order to obtain good agreement. Tests were performed at two Mach numbers at several different jet momentum coefficients. In order to be consistent with the experimental method, the CFD lift and pitching moment values were determined by integrating the pressures over the wing.

Dual strain gage balance system for measuring light loads

Abstract: A dual strain gage balance system for measuring normal and axial forces and pitching moment of a metric airfoil model imparted by aerodynamic loads applied to the airfoil model during wind tunnel testing includes a pair of non-metric panels being rigidly connected to and extending towards each other from opposite sides of the wind tunnel, and a pair of strain gage balances, each connected to one of the non-metric panels and to one of the opposite ends of the metric airfoil model for mounting the metric airfoil model between the pair of non-metric panels. Each strain gage balance has a first measuring section for mounting a first strain gage bridge for measuring normal force and pitching moment and a second measuring section for mounting a second strain gage bridge for measuring axial force.