Pitching moment

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

Particle image velocimetry investigation of flow over unsteady airfoil with trailing-edge strip

Abstract: The flow over a flapped NACA 0012 airfoil, oscillated slightly through the static-stall angle, was investigated by using particle image velocimetry, and was supplemented by surface pressure and dynamic-load measurements. A significant increase in the dynamic lift force and nose-down pitching moment was observed. The most pronounced flow phenomenon was the formation and detachment of an energetic leading-edge vortex compared to the no-flapped airfoil. The details of the underlying physical mechanisms responsible for the various light-stall flow processes were provided via the instantaneous velocity and vorticity fields measurements. In contrast to the Gurney flap, the inverted trailing-edge strip led to an improved negative damping while a reduced lift force. The addition of an inverted strip always led to the appearance of a Karman-type vortex shedding street immediately downstream of the strip over the entire oscillation cycle.

Wind Tunnel Experiments and CFD Analysis of Blended Wing Body (BWB) Unmanned Aerial Vehicle (UAV) at Mach 0.1 and Mach 0.3

Abstract: This paper discusses the aerodynamics behavior of a baseline design of a Blended Wing Body (BWB) aircraft developed at MARA University of Technology (UiTM). Two methods of analysis are presented, i.e. Steady-state, three- dimensional Computational Fluid Dynamics (CFD) of the BWB at Mach 0.3 and Wind Tunnel experiments on 1/6 scaled half model of the BWB at Mach 0.1. In both methods of analysis, Lift Coefficient (CL), Drag Coefficient (CD) and Pitching Moment Coefficient (CM) are measured and compared at respective Mach numbers with respect to variation of angle of attack. Pressure contours and Mach number contours are plotted and the turbulence area is predicted, both extracted from CFD analysis. Visualization using mini tuft during wind tunnel tests is also executed to complete the analysis where the stall progression patterns can be clearly observed. The presented BWB UAV design here has achieved an unprecedented capability in terms of sustainability of flight at high angle of attack, low parasite drag coefficient and decent maximum lift coefficient. Some recommendations for future improvement of the BWB are given.

The Dynamics of Separation Control on a Rapidly Actuated Flap

Abstract: Unsteady aerodynamic loads on a NACA 0021 airfoil during rapid flap deflections were investigated. Typical dynamic stall effects like an overshoot in lift, drag, and pitching moment have been observed. Flap deflection angle and speed were varied while the angle of attack remained constant at = 0 . To prevent stall and accompanying detrimental behavior, fluidic actuators generating discrete sweeping jets were integrated into the simple flap of the airfoil. Initial experiments at various angles of incidence but constant flap deflections proved that these actuators can prevent flow separation, increase lift, and decrease the drag of the airfoil. Dynamic tests revealed that sweeping jet actuators can also eliminate dynamic stall effects. A significant gain in lift and a substantial reduction in drag were achieved within a short period of time, even for high flap deflection angles of 30 .

Experimental investigation of air jets to control shock-induced dynamic stall

Abstract: This paper shows experimental results for dynamic stall control on a dynamically pitching OA209 airfoil at Mach 0.5, with Reynolds numbers 1.9 × 106 and 0.85 × 106 . The control was by supersonic constant blowing on the suction side of the airfoil. Dry compressed air was blown normal to the airfoil chord, from portholes at 10% chord, with diameter 1% chord. At both Reynolds numbers, the OA209 without blowing experienced shock-induced stall with a hysteresis in lift and pitching moment around the static values, rather than the overshoot in forces typically associated with a dynamic stall vortex. The forces and the stall control were primarily functions of the maximum angle of attack, with full control of stall possible for maximum angles of attack of 14◦ and less. The higher Reynolds number required relatively more blowing (higher Cq , Cμ ) to control the dynamic stall. Drag was reduced for separated flow, but the energy required in compressed air to achieve this was more than the savings in drag, and no cases were found in which flow control resulted in a reduction in total power used. Increasing the jet spacing resulted in equivalent flow control with less air use. Jets spaced at 20% chord and mass flux ratio Cq = 0.004 (momentum ratio Cμ = 0.016) resulted in a reduction of the pitching moment peak by 60%. The flow control with air jets was uncritical regarding the aerodynamic damping.

Waverider Aerodynamics and Preliminary Design for Two-Stage-to-Orbit Missions, Part 2

Abstract: Osculating cones waveriders are evaluated for future reusable space transportation systems An integrated design program hasbeen developed by theInstitute of AircraftDesign and Structure Mechanics, which simulates the iterative design process including the main interactions between the involved disciplines Starting points are the dee nition of the design task (range, payload to orbit, mission and orbit proe le, etc )and a generic waverider shape with its aerodynamic characteristics The design program contains the geometric sizing of the aircraft shape, a realistic engine model with bookkeeping, aerodynamic load calculations, structure mass estimation with a e nite element method, thermal protection design, and a e ight-path simulation with trim control The predesign investigations focus on the design of a two-stage-to-orbit aerospace plane with a waverider-based e rst stage performing a cruise e ight from Europe to the equator with an orbiter transferring a maximum payload of 7 tons to a low Earth orbit The comparison with a conventional hypersonic cone guration indicates that it should be possible to fule ll the dee ned mission with 35% less fuel and an 11% lower takeoff weight These results underline the potential of the waverider concept Nomenclature FX, FZ = forces in longitudinal and vertical direction L D = lift over drag ratio, aerodynamic efe ciency M = pitching moment n = load factor S = wing reference area, m 2 V = maximum total aircraft volume, m 3