Pitching moment

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

Dynamic Load Control on a Finite Span Wind Turbine Blade Using Synthetic Jets

Abstract: The feasibility of active flow control to mitigate hysteresis loop due to a dynamically pitching finite span s809 blade was investigated experimentally at a Reynolds number of 220,000. Under normal operating conditions, hysteresis loop and tip vibrations exist, which with extended exposure would cause blade fatigue and eventually translate to a reduced lifetime of wind turbines. In this regard, active flow control via arrays of synthetic jet actuators was explored as a means to control flow separation over the finite span blade, which can lead to mitigation of these undesired unsteady loads. In the present work, a six-component load cell was used to measure the aerodynamic loading of lift, drag and pitching moment. Stereoscopic Particle Image Velocimetry (SPIV) measurements were also performed to understand the effects of synthetic jets on flow separation during dynamic pitch, and to correlate these effects to the forces and moment measurements. It was shown that active flow control could delay or minimize dynamic stall through the reduction of the hysteresis loop of the aerodynamic loads. This implies less unsteady aerodynamic loadings on the blade, which can potentially lead to prolonged life of wind turbines.

On the acoustic radiation of a pitching airfoil

Abstract: We examine the acoustic far field of a thin elastic airfoil, immersed in low-Mach non-uniform stream flow, and actuated by small-amplitude sinusoidal pitching motion. The near-field fluid-structure interaction problem is analyzed using potential thin-airfoil theory, combined with a discrete vortex model to describe the evolution of airfoil trailing edge wake. The leading order dipole-sound signature of the system is investigated using Powell-Howe acoustic analogy. Compared with a pitching rigid airfoil, the results demonstrate a two-fold effect of structure elasticity on airfoil acoustic field: at actuation frequencies close to the system least stable eigenfrequency, elasticity amplifies airfoil motion amplitude and associated sound levels; however, at frequencies distant from this eigenfrequency, structure elasticity acts to absorb system kinetic energy and reduce acoustic radiation. In the latter case, and with increasing pitching frequency ωp, a rigid-airfoil setup becomes significantly noisier than an...

Thrust Vector Control of an Upper-Stage Rocket with Multiple Propellant Slosh Modes

Abstract: The thrust vector control problem for an upper-stage rocket with propellant slosh dynamics is considered. The control inputs are defined by the gimbal deflection angle of a main engine and a pitching moment about the center of mass of the spacecraft. The rocket acceleration due to the main engine thrust is assumed to be large enough so that surface tension forces do not significantly affect the propellant motion during main engine burns. A multi-mass-spring model of the sloshing fuel is introduced to represent the prominent sloshing modes. A nonlinear feedback controller is designed to control the translational velocity vector and the attitude of the spacecraft, while suppressing the sloshing modes. The effectiveness of the controller is illustrated through a simulation example.