Pitching moment

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

The Effect of Engine Location on the Aerodynamic Efficiency of a Flying-V Aircraft

Abstract: The Flying-V is a novel flying wing concept where the main lifting surface has been fully integrated with the passenger cabin. This study focuses on the effect of engine positioning on aerodynamic interference under regulatory and structural constraints. An initial benchmark for the lift-to-drag ratio is obtained from a baseline Flying-V configuration, and the influence of the x, y and z position, as well as engine orientation are subsequently analysed. An Euler solver on a three-dimensional, unstructured grid is used to model the flow at cruise condition: M = 0.85, h = 13, 000 m, α = 2.9 ◦, and a thrust per engine of 50 kN. The viscous drag contribution is computed using an empirical method. A total of forty different engine locations are tested under these conditions to build a surrogate model that predicts the aircraft’s lift-to-drag ratio based on the position of the engine. The results obtained show that misplacing the engine can lead to significant lift-to-drag ratio losses going as high as 55% when compared against the ideal integration configuration. A region behind the airframe’s trailing edge is identified where the interference losses due to the installation are minimized. At this location, engine installation causes a 10% penalty in aerodynamic efficiency, a minimum one-engine-inoperative yawing moment and a small thrust-induced pitching moment.

Method for determining aerodynamic parameters of model free flight tests

Abstract: A method for determining aerodynamic parameters of model free flight tests is used in model free flight tests including a wind tunnel free flight test, an atmospheric free flight test and the like. Under the situation that a model used in wind tunnel free flight or atmospheric free flight moves in a plane, the method of polynomial time is adopted to match the linear displacement of the centroid of the model in the horizontal direction and the vertical direction and the shooting recording observing value, changing along with time, of the angle of pitch of the model, then, the time-dependent changing rule of the linear displacement, the linear velocity and the linear acceleration of the centroid of the model and the angle displacement, the angle velocity and the angle acceleration of the angle of pitch is obtained, and accordingly the time-dependent changing rule of the resistance coefficient, the lift coefficient and the pitch moment coefficient in the process of model flying is obtained. The application conditions and the range of a data processing method of the model free flight tests are expanded, and the test recorded data can be processed in wide application conditions and ranges to obtain the aerodynamic parameters and the movement rule of the model.

Aerodynamics of porous airfoils and wings

Abstract: This paper presents novel wind tunnel test results on the aerodynamics of a symmetric thin porous airfoil and a porous rectangular half wing using a symmetric thin airfoil as its cross section, obtained by a six-component force balance. The variation of lift coefficient, drag coefficient, pitching moment, lift versus drag, the gradient of lift, and location of the aerodynamic center with respect to the angle of attack are presented as a function of the porosity. The data, where possible, are compared with the analytical results. The trend of the experimental results behaves in the same manner as the analytical solution. The measured drag coefficients of the airfoil and wing are also presented. The applicability of the standard equation relating the lift coefficient of a non-porous wing with that of a non-porous airfoil to the case of porous wings is verified by applying the equation to porous wings and validating the results using experimental data. Lift slope decreases as the porosity increases. The drag decreases at a low value of porosity and then increases as porosity increases. The standard equation for obtaining the lift coefficient of a wing from the lift coefficient of an airfoil is applicable and valid for porous wings and airfoils.

Transient air and surface contact vehicle

Abstract: A transient air and surface contact vehicle for transporting a person has a fuselage structure for carrying a person. A vehicle support extends from the structure and abuts a surface and thereby supports the vehicle at a predetermined distance above the surface. A buoyancy control device mounted on the structure and on the vehicle support provides for the buoyancy required to keep the vehicle afloat while stationary and at low speeds. At high speed the dynamic pressures generated at the bottom of the struts provide the supporting forces. A power source is mounted on the structure for moving the vehicle along the surface at the predetermined distance above the surface. A position control mounted on the structure produces a positive pitching moment to cause the vehicle to become airborne, a negative pitching moment to maintain the vehicle in surface-following contact with the surface and both moments to control the altitude of the vehicle when it is airborne. It is the pre-determined negative pitching moment that enables stable "open loop" pitch performance in the presence of high speeds and irregular surfaces.

Experimental evaluation of a flapping-wing aerodynamic model for MAV applications

Abstract: In the preliminary design phase of the bio-inspired flapping-wing MAV (micro air vehicle), it is necessary to predict the aerodynamic forces around the flapping-wing under flapping-wing motion at cruising flight. In this study, the efficient quasi-steady flapping-wing aerodynamic model for MAV application is explained and it is experimentally verified. The flapping-wing motion is decoupled to the plunging and pitching motion, and the plunging-pitching motion generator with load cell assembly is developed. The compensation of inertial forces from the measured lift and thrust is studied to measure the pure aerodynamic loads on the flapping-wing. Advanced ratio is introduced to evaluate the unsteadiness of the flow and to make an application range of flapping-wing aerodynamic model.