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Shuttlecock design and development
Published in Steve Haake, The Engineering of Sport, 2020
The pitching moment coefficients were not significantly different between the production models. In all cases the position of the aerodynamic centre is behind the centre of gravity (which gives the shuttlecock its stability during flight).
Static Aeroelasticity
Published in Rama B. Bhat, Principles of Aeroelasticity, 2018
The aerodynamic center is the point on the airfoil about which the aerodynamic moment is independent of angle of attack, α. The moment coefficient about this center does not vary with CL. This is located close to the one-quarter chord point for subsonic flow in an incompressible fluid. The aerodynamic center moves to the midchord point when the flow is entirely supersonic.
Fly-by-wire
Published in D.A. Bradley, N.C. Burd, D. Dawson, A.J. Loader, Mechatronics, 2018
D.A. Bradley, N.C. Burd, D. Dawson, A.J. Loader
In the world of combat aircraft, fly-by-wire techniques have allowed new control strategies to be developed and successfully implemented. An aircraft is normally designed to be naturally stable in flight; this is achieved by arranging for the aerodynamic centre – the point at which act the aerodynamic lift forces generated by the wing – to be behind its normal centre of gravity, as shown in Fig. 27.1a. A change in the direction of air flow causes a corresponding change in the aerodynamic force at the centre of pressure which tends to rotate the aircraft into the new flow direction, and this balance effect provides the aircraft with natural stability. A major disadvantage of this, however, is that the turning moment caused by the centre of pressure being behind that of the centre of gravity must be counterbalanced by a downward force on the tailplane, which causes a reduction in the overall lift and increases the drag of the aircraft.
Design of a nonlinear multi-input–multi-output sliding mode pitch angle and plunge controller for a 5MW wind turbine blade tip
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Ranjeet Agarwala, Robert A. Chin, Praveen Malali
Airfoils at each section were scaled and rotated by their chord lengths and values of angular twists. Various cross-sections were lofted and connected using inbuilt CAD modeling interpolation routines. Complete details of the airfoil, the associated data, and 3D modeling details were documented by Agarwala and Ro (2013). For a small section of the blade, the lift force and moment (Fung 2002; Hoogedoorn, Jacobs, and Beyene 2010; Singh and Yim 2003) are given in Equations (1) and (2). Because of geometric differences, the lift force at the aerodynamic center of any blade section results from a pressure difference between the upper and lower surface of the airfoil when the air flows across that airfoil section. The camber of the airfoil produces varying velocities at the top and bottom surface of the airfoil. The pressure difference when multiplied by the area of a section of the blade of length produces the lift force of dL. The lift coefficient is a nondimensional term that captures the geometry of the airfoil impacted by lift forces. Similarly, the aero-dynamic moment is computed by multiplying the vertical forces with the chord length. The moment coefficient is a nondimensional term that captures the geometry of the airfoil impacted by aero-dynamic moment.
Synthesis of landing dynamics on land-base high performance aircraft considering multi-variate landing conditions
Published in Mechanics Based Design of Structures and Machines, 2023
P. S. Suresh, Niranjan K. Sura, K. Shankar, G. Radhakrishnan
The EQM essentially contains the forces and moments contribution from LG, aerodynamics and thrust balanced by the translation and rotary inertia forces of aircraft. constitute the stability derivatives on aerodynamic lift, pitch and roll acting at the aerodynamic center which is at a distance ea away from CG of aircraft. Dynamic pressure q is represented as with lifting surface area as s, mean aerodynamic chord as and span as The aerodynamic forces and moments are obtained from linear perturbation theory represented in the form of Taylor series (Nelson 1998). represents the NLG forces transformed to the interface location on fuselage and similarly so, for other two MLG’s. Ft denote the engine thrust force acting at lt distance away from CG location of aircraft, interfaced using simple algorithm wherein thrust is varied according to landing event. The landing variables arrived using the multi-variate analysis as specified in Table 2 is set as initial conditions and the multi-variate landing response simulation is performed. Co-simulation consists of two step approach (i) Extraction of equilibrated force reaction time histories at LG interface location of airframe, the output obtained from the nonlinear landing dynamic response simulation considering airframe as rigid body (ii) Providing these input on to a flexible airframe Finite Element (FE), mathematically representing the modal characteristic of real aircraft and performing a transient dynamic simulation to obtain airframe flexible dynamic responses.
Modeling and analysis of vertical axis turbine with pitch adjusted by an eccentric guide
Published in International Journal of Green Energy, 2023
Jaqueline Diniz da Silva, Fabio Toshio Kanizawa
where the total area of influence of the turbine accounts for part of the length that is outside the radius R1, such as depicted in the right side of Figure 1 for γ = π/2 rad. In this study, it was considered that the pin A of Figure 1 was set at ¼ of the chord length, based on the conventional definition of aerodynamic center, as discussed by Houghton and Carpenter (2003), and consequently L = 4R3/3. Then, the power coefficient is given as follows: