Pitching moment

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

Drag reduction in aircraft model using elliptical winglet

Abstract: Aerodynamic characteristics for the aircraft model with NACA (National Advisory Committee for Aeronautics) wing No. 653-218 have been studied using subsonic wind tunnel of 1000 mm x 1000 mm rectangular test section and 2500 mm long of Aerodynamics Laboratory Faculty of Engineering (Universiti Putra Malaysia). Six components wind tunnel balance is used for measuring lift, drag and pitching moment. Tests are conducted on the aircraft model with and without winglet of two configurations at Reynolds numbers 1.7 x 10 5 , 2.1 x 10 5 , and 2.5 x 10 5 . Lift curve slope increases more with the addition of the elliptical winglet and at the same time the drag decreases more for the aircraft model with elliptical shaped winglet giving an edge over the aircraft model without winglet as far as Lift/Drag ratio for the elliptical winglet is considered. Elliptical winglet of configuration 2 (Winglet inclination 60 0 ) has, overall, the best performance, giving about 6% increase in lift curve

Three-dimensional vortex interactions with a stationary blade

Abstract: Surface pressure measurements were obtained during a three-dimensional vortex interaction with a NACA 0015 aerofoil. The upper and lower surfaces of the blade experienced different aerodynamic loads which appear to be controlled by the impact of the vortex axial core flow on the blade surface. On the upper surface of the blade, where the vortex core flow was away from the aerofoil, the interaction was characterised by the generation of a suction peak. On the lower surface, where the axial component was towards the blade, a pressure pulse developed and seemed to be influenced by the vortex approach angle. These features resulted in rapid changes in normal force and quarter chord pitching moment during the interaction. This impulsive loading of the blade may provide some explanation for sound generation and control degradation problems associated with the tail rotor of helicopters.

Transverse Vibration Response of a Super High-Speed Elevator under Air Disturbance

Abstract: For a super high-speed elevator running in a hoistway, it will encounter air flows at high speed. The transverse force and pitching moment generated by the air intensify the transverse vibration of...

Investigation of Rotor Blade Structural Dynamics and Modeling Based on Measured Airloads

Abstract: The work presented herein treats measured airloads from the UH-60A Airloads Program as prescribed external loads to calculate the resulting structural loads and motions of a rotor blade. Without the need to perform any aerodynamic computations, the coupled aeroelastic response problem is reduced to one involving only structural dynamics. The results, computed by RCAS and CAMRAD II, are compared against measured results and against each other for three representative test points. The results from the two codes mostly validate each other. Seven more test points, with responses computed by RCAS, to form thrust and airspeed sweeps are evaluated to better understand key issues. One such issue is an inability to consistently predict pushrod loads and torsion moments well, and this is found to be amplified at the two test points with the highest thrust coefficient. For these two test points, harmonic analysis reveals that the issue is due to excessive amounts of 5/rev response that stem from high levels of 5/rev pitching moment excitation. Another issue that concerns all test points is that the phase of the 1/rev blade flapping motion is not predicted well, which reflects the high sensitivity of this quantity that is developed due to having a first flap frequency of approximately 1/rev. Results also show that current force-velocity relationships, used in describing the lead-lag damper, are not satisfactory to consistently yield accurate inboard chordwise bending moment predictions. Overall, the investigation here, conducted with numerous test points, further confirms the methodology of prescribing measured airloads for assessing the structural dynamics capability of a computational tool.

Multi-Objective Topology Optimization of Wing Skeletons for Aeroelastic Membrane Structures

Abstract: This work considers the multi-objective aeroelastic optimization of a membrane micro air vehicle wing through topology optimization. The low aspect ratio wing is discretized into panels: a two material formulation on the wetted surface is used, where each panel can be membrane (wing skin) or carbon fiber (laminate reinforcement). An analytical sensitivity analysis of the aeroelastic system is used for the gradient-based optimization of aerodynamic objective functions. An explicit penalty is added, as needed, to force the structure to a 0-1 distribution. Pareto trade-off curves are constructed by considering convex combinations of two disparate lift, drag, or pitching moment-based objective functions. The general relationship between spatial stiffness distribution (wing topology) and aerodynamic performance is discussed, followed by the Pareto optimality of the computed designs over a series of baseline wing structures. The work concludes with an experimental validation of the superiority of select optimal...