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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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Proceedings ArticleDOI
13 Aug 2012
TL;DR: In this paper, the feasibility of trimming an airplane using internal mass motion as moment generation mechanisms was investigated, where two internally moving masses were considered: mass moving laterally to generate rolling moment and mass moving longitudinally to generate pitching moment.
Abstract: This paper investigates the feasibility of trimming an airplane using internal mass motion as moment generation mechanisms. Two internally moving masses are considered: (i) mass moving laterally to generate rolling moment and (ii) mass moving longitudinally to generate pitching moment. These are to replace aileron and elevator, respectively. Various straightlevel ight conditions are considered to determine the trim conditions, particularly the masses and positions of the moving masses. For a small unmanned aerial vehicle, feasible level ight trim conditions are found using only the longitudinal moving mass, without the conventional aerodynamic control surface, elevator. Furthermore, endurance and range of for straight-level ight conditions are determined and compared with the aircraft with elevator.

16 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented a numerical simulation of an airfoil undergoing a deep dynamic stall employing a computational fluid dynamics code, where overset and polyhedral grid techniques were adopted to accurately simulate the flow field at high angles of attack.
Abstract: To consider stall flutter in the design procedure of a blade, accurate models of flow loading are needed. This paper first presents a numerical simulation of an airfoil undergoing a deep dynamic stall employing a computational fluid dynamics code. Overset and polyhedral grid techniques are adopted to accurately simulate the flow field at high angles of attack. Having validated the simulation, the occurrence of stall flutter over a pitching airfoil with an increase in amplitude and frequency of oscillations is examined. The results express that the amplitude of the lift and pitching moment depends on the amplitude of the forced oscillation and there are higher harmonics of the pitching moment compared to the forced oscillation frequency content, both indicating the nonlinearity of aerodynamic lift and pitching moment. Subsequently, a nonlinear reduced model of the dynamic stall is derived using a fuzzy inference system (FIS) and the adaptive network-based FIS (ANFIS). Due to the unsatisfactory results of modeling, especially at post-stall angles of attack, the Gram–Schmidt orthogonalization technique is used to construct a more complex structure of the input variables. The new higher-order input variables have been re-employed by FIS and ANFIS. The results show that excellent modeling is achieved by ANFIS between the new structure of the inputs and the corresponding aerodynamic coefficients using only 10% of input–output data. Having found an appropriate relation, the proposed reduced-order model could properly predict the aerodynamic response of the pitching airfoil at two reduced frequencies.

16 citations

Journal ArticleDOI
TL;DR: In this paper, a pneumatic system was used to deliver dry compressed air as jets for flow control at total pressures of up to 10 bar, and the results from the experiments were supported by three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) computations of the pitching airfoil with flow control using the DLR-TAU code.
Abstract: The experimental investigation of constant blowing air jets as fluidic control devices for helicopter dynamic stall control is described. A carbon fiber airfoil of constant OA209 cross section was fitted with a pneumatic system to deliver dry compressed air as jets for flow control at total pressures of up to 10 bar. The experiment used porthole jets of radius 1% chord, positioned at 10% chord and with spacing 6.7% chord. The positive dynamic stall control effects were demonstrated at Mach 0.3, 0.4, and 0.5 for deep dynamic stall test cases with the best test cases reducing the pitching moment peak after the main stall by 83% while increasing the mean lift over one pitching cycle by 30%. The conclusions from the experiments are supported by three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) computations of the pitching airfoil with flow control using the DLR-TAU code.

16 citations

Proceedings ArticleDOI
28 Jun 2010
TL;DR: In this article, a numerical framework is presented to simulate rigid and flexible flapping wings by coupling a Navier-Stokes solver to a geometrically nonlinear co-rotational structural solver.
Abstract: *† ‡ § A numerical framework is presented to simulate rigid and flexible flapping wings. The fluid-structure interaction is realized by coupling a Navier-Stokes solver to a geometrically nonlinear co-rotational structural solver. In the coupled fluid-structure interaction interface the aerodynamic loading and deformed wing surface are shared by two solvers within each time step. A remeshing method based on radial basis function is implemented to handle large deformations, preserve grid quality, and execute economically. Flexible flapping wing operating in both vacuum and air is considered to shed light on inertial and aerodynamic loading-induced shape deformation. Impacts of flapping isotropic wing with single degree of freedom rotation on aerodynamic force generation are presented for Re= 1.5×10 3 and k= 0.56. The results indicate: 1) the flexibility-induced pitching angle promotes thrust generation, and 2) the increase of wing velocity due to large bending motion enhances aerodynamic force by increasing pressure differences. For a wing of anisotropic mechanical properties, highly three-dimensional wing deformation is observed when the wing accelerates or decelerates in absent of aerodynamic loadings.

16 citations

ReportDOI
01 Sep 1972
TL;DR: In this paper, measurements were made of the unsteady normal force and pitching moment on an NACA 0012 airfoil model oscillated both sinusoidally and nonsinusoidally over a range of incidence angles, including a substantial penetration into stall.
Abstract: : Measurements were made of the unsteady normal force and pitching moment on an NACA 0012 airfoil model oscillated both sinusoidally and nonsinusoidally over a range of incidence angles, including a substantial penetration into stall. The sinusoidal normal force and pitching moment data were reduced and tabulated as functions of the angle of attack, the angular velocity parameter, and the angular acceleration parameter. This generalized form of the data was used to reconstruct the measured sinusoidal aerodynamic response of the model airfoil with excellent results. Additional correlations were made using nonsinusoidal pitch schedules which included periodic ramp changes in angle of attack and a flexured angular blade response to a one-per- rev sinusoidal incidence angle change typical of that for a helicopter blade. The agreement between predicted and measured normal force and moment loops was very good for the ramp motion.

16 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202353
202294
202168
202076
201983
201886