Pitching moment

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

Kinematic and Aerodynamic Response of Locusts in Sideslip

Abstract: Effects of the sideslip angle on the wing kinematics and the aerodynamic forces and moments generated by the locusts were investigated in a low-speed wind tunnel. Three live locusts (Schistocerca americana) were tested at tunnel speeds of 0, 2, and 4 m/s at three body angles of attack (0°, 3°, and 7°) and three sideslip angles (0°, −10°, and −20°). A sensitive custom-built microbalance was used to measure the forces and moments. The balance was synchronized with high-speed video system recording the wing kinematics. It was observed that the nose down pitching moment increases with the angle of attack increase. This is an indication of active and/or passive mechanisms restoring the body orientation in the vertical plane and providing pitch stability of locusts. The side airflow generates a large side force and positive rolling moment. In response to the oncoming side wind, the locust executes larger-amplitude flapping motion on the windward wings. Changes in kinematic parameters of locust wings are similar...

Experimental Investigation of the Aeroelastic Behavior of a Laminar Airfoil in Transonic Flow

Abstract: The unsteady flow around an oscillating CAST 10-2 airfoil model was investigated at Mach numbers relevant for cruise flight of transport aircraft. Unsteady pressure sensors and hot-film anemometry were used to characterize the unsteady flow and the laminar-turbulent transition on the airfoil. Results are presented for subsonic and transonic Mach numbers focusing at the transonic regime at M = 0.750. Thereby steady measurements serve as a starting point to gain a better understanding of flow physics. Transition positions, pressure distributions and the resulting lift coefficients are discussed and provide a deeper insight in the nonlinearity of the lift polar. Unsteady hot-film signals are discussed for one period and reveal a temporal asymmetry of the flow state and of the integral values lift and moment coefficient. Derivatives from these coefficients as functions of reduced frequency and amplitude are presented.

Phugoid Approximation for Conventional Airplanes

Abstract: An improved closed-form approximation for phugoid motion in conventional airplanes is presented. Although several closed-form approximations for phugoid motion are currently available and widely used, none of these approximations accurately predict all of the fundamental characteristics of phugoid motion. The new approximation accounts for changes in angle of attack as well as the effects of pitch stability and pitch damping. The total phugoid damping is shown to depend on pitch damping aswell as aircraftdrag. In addition, thissolution pointsout another important contribution to phugoid damping called phase damping. It is shown that the phase-damping contribution to the real component of the phugoid eigenvalue is always positive and tends to reduce the total phugoid damping. Under certain conditions this phase damping can cause the phugoid mode to become divergent. Nomenclature Aw = planform area of the wing CD = total drag coefe cient CDp = parasitic drag coefe cient CD,a = change in drag coefe cient with angle of attack CL = lift coefe cient CL,a = change in lift coefe cient with angle of attack CM = pitching moment coefe cient CM,a = change in pitching moment coefe cient with angle of attack CM,$ = change in pitching moment coefe cient with dimensionless pitching rate ¯ c = mean chord length e = Oswald efe ciency factor FT = thrust force g = acceleration of gravity Iyy = pitching moment of inertia in body-e xed coordinates m = aircraft mass RA = aspect ratio Rd = phugoid pitch-damping ratio Rg = dimensionless gravitational acceleration RM = dimensionless change in pitching moment with axial velocity RM,a = dimensionless change in pitching moment with angle of attack RM,$ = dimensionless change in pitching moment with pitching rate Rp = phugoid phase-divergence ratio Rs = phugoid stability ratio Rx = dimensionless change in axial force with axial velocity Rxa = complex amplitude Rxc = complex coefe cient Rxp = complex phase Rx,a = dimensionless change in axial force with angle of attack Rz = dimensionless change in normal force with axial velocity Rza = complex amplitude Rzc = complex coefe cient Rzp = complex phase Rz,a = dimensionless change in normal force with angle of attack

Practical formulas towards distortional buckling failure analysis for steel-concrete composite beams

Abstract: Summary As the most predominant type of failure for steel–concrete composite beams (SCCBs) in negative moment area, distortional buckling is significantly impacted by the interaction effect between the applied loading and the torsional–lateral restraint stiffness of the bottom flange, which is termed as loading–restraint interaction here for short. Recently, a modified elastic foundation beam method capable of considering the interaction effect properly was proposed to calculate critical buckling moment for SCCBs under negative uniform moment. As a sequel to such development, a functional relationship between two dimensionless auxiliary parameters (i.e. equivalent slenderness ratio and equivalent moment coefficient) is discovered in this study. On the basis of the close association between the pair of dimensionless parameters, empirical formulas are derived in a remarkably simply explicit form to evaluate the critical buckling moment for SCCBs under negative uniform moment or moment gradient. These formulas are simple, user-friendly and of practical use. Compared with conventional approaches without considering the loading–restraint interaction effect, the practical approach developed in this paper can achieve higher accuracy and is more easy-implemented. The study lays a foundation for determining the ultimate bearing capacity of SCCBs considering moment gradient effect rapidly. Copyright © 2016 John Wiley & Sons, Ltd.