Pitching moment

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

Numerical Computations of Transonic Critical Aerodynamic Behavior

Abstract: The determination of aerodynamic coefficients by shell designers is a critical step in the development of any new projectile design. Of particular interest is the determination of the aerodynamic coefficients at transonic speeds. It is in this speed regime that the critical aerodynamic behavior occurs and a rapid change in the aerodynamic coefficients is observed. Three-dimensional, transonic, flowfield computations over projectiles have been made using an implicit, approximately factored, partially flux-split algorithm. A composite grid scheme has been used to provide the increased grid resolution needed for accurate numerical simulation of three-dimensional transonic flows. Details of the asymmetrically located shock waves on the projectiles have been determined. Computed surface pressures have been compared with experimental data and are found to be in good agreement. The pitching moment coefficient, determined from the computed flowfields, shows the critical aerodynamic behavior observed in free flights. I. Introduction T HE flight of projectiles covers a wide range of speeds. The accurate prediction of projectile aerodynamics at these speeds is of significant importance in the early design stage of a projectile. The critical aerodynamic behavior occurs in the transonic speed regime, 0.9

Study of the effects of wing sweep on the aerodynamic performance of a blended wing body aircraft

Abstract: This article presents a study of the effects of wing sweep on the aerodynamic performance of a blended wing body (BWB) aircraft that is based on an aerodynamically optimized design with a fixed planform and pitching moment constraint. Sixteen BWB geometries with varying wing sweep angles ranging from −40° (forward sweep) to 55° sweep were evaluated, while keeping the aerofoil profiles and twist distribution unchanged from the original optimized geometry. This gives some insight into the effects of one of the key planform design parameters.Numerical simulations were carried out using Euler solutions of the flow field with adaptive unstructured grids. Grid sensitivity studies were carried out, along with grid adaptation, on all geometries for solution accuracy. Results show that within 10° −55° sweep, there is significant variation in the lift-to-drag ratio (LID), whereas for sweep values from −40° to 10°, the L/D ratio remained relatively constant. To maintain the design lift for varying wing sweep...

Numerical methods and a computer program for subsonic and supersonic aerodynamic design and analysis of wings with attainable thrust considerations

Abstract: This paper describes methodology and an associated computer program for the design of wing lifting surfaces with attainable thrust taken into consideration. The approach is based on the determination of an optimum combination of a series of candidate surfaces rather than the more commonly used candidate loadings. Special leading-edge surfaces are selected to provide distributed leading-edge thrust forces which compensate for any failure to achieve the full theoretical leading-edge thrust, and a second series of general candidate surfaces is selected to minimize drag subject to constraints on the lift coefficient and, if desired, on the pitching moment coefficient. A primary purpose of the design approach is the introduction of attainable leading-edge thrust considerations so that relatively mild camber surfaces may be employed in the achievement of aerodynamic efficiencies comparable to those attainable if full theoretical leading-edge thrust could be achieved. The program provides an analysis as well as a design capability and is applicable to both subsonic and supersonic flow.

Ancillary aerodynamic structures for an unmanned aerial vehicle having ducted, coaxial counter-rotating rotors

Abstract: An unmanned aerial vehicle (UAV) (100) having a toroidal fuselage (120) and a rotor assembly (170) including counter-rotating rotors coaxially mounted with respect to the toroidal fuselage incorporates ancillary aerodynamic structures (18) having a cambered airfoil profile to provide a nose-down pitching moment to counteract the nose-up pitching moment generated by airflow over the toroidal fuselage during forward translational flight of the UAV. The ancillary aerodynamic structures are symmetrically mounted in combination with the lateral sides of the toroidal fuselage so that the centers of lift are located aftwardly of the fuselage axis of the toroidal fuselage in forward translational flight modes. In a first embodiment, the ancillary aerodynamic structures (18) are fixedly mounted in combination with the toroidal fuselage (10) at a predetermined angle of incidence. In a second embodiment, the ancillary aerodynamic structures (19) are rotatably mounted in combination with the toroidal fuselage (10') to provide variable incidence ancillary aerodynamic structures for the UAV.

Aerodynamic force data for a V-style ski jumping flight

Abstract: To determine the flight of a ski jumper it is essential to know what aerodynamic forces are acting on the ski jumper. However, few data on this are available, especially for a V-style ski jumping flight. We have measured the aerodynamic forces during the free flight phase for a V-style, as well as a parallel-style, ski jump by employing a full-size model in a wind tunnel. The aerodynamic force data, (drag, lift and pitching moment) were obtained to create an aerodynamic database. These forces are given in polynomial form as functions of the angle of attack, the body-ski (forward leaning) angle and the ski-opening (V-style) angle. Using the polynomial form database is a convenient way of obtaining the aerodynamic forces. Moreover, the wind tunnel was equipped with a ground effect plate to measure the aerodynamic forces during the landing phase. It was found that the difference between the lift with and without the ground effect plate increases with the ski-opening angle. The longitudinal stability in the pitching motion of a body-ski combination is also discussed on the basis of the pitching moment data. This indicates that a stable pitching oscillation of the body-ski combination may arise around an equilibrium point in the angle of attack, the trim angle of attack, during flight.