Pitching moment

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

Transonic Airfoil Design by Constrained Optimization

Abstract: A N aerodynamic design method is developed which cou- ples flow analysis and numerical optimization to find an airfoil shape with improved aerodynamic performance. The flow analysis code is based on the coupled Euler and bound- ary-layer equations in order to include the rotational, viscous physics of transonic flows. The numerical optimization pro- cess searches for the best feasible design for the specified design objective and design constraints. The method is dem- onstrated with several examples at transonic flow conditions. Contents The optimization process is performed with a commercially available constrained optimization tool.3 The sensitivity of the flow to the perturbation is calculated by finite differences. The effectiveness and efficiency of the design process are influenced by many factors: the number and the shape of the base functions, the number and the tolerance of the con- straints, the flow model and the grid used for flow analyses, and the flight condition at the design point. Design Demonstration The objective of the present design is to produce minimum drag at a specified transonic flight condition. Inequality con- straints are imposed on lift, pitching moment, and cross-sec- tional area of the optimized airfoil. The lift and the area of the optimized airfoil should not be smaller than those of the original airfoil, and the pitching moment should not increase in absolute value. Also imposed are side constraints which limit the magnitude of the design variables. Side constraints are important because a large geometry change can cause boundary-layer separation leading to a termination of the flow solver.

Morphing Airfoil Design for Minimum Aerodynamic Drag and Actuation Energy Including Aerodynamic Work

Abstract: Recently, there has been great interest in developing technologies that may enable a morphing aircraft. Such an aircraft can change shape in flight, which would make it possible to adjust the wing to the best possible shape for any flight condition encountered by the aircraft. However, there is an actuation cost associated with making these shape changes that must be included in the optimization process. A previous effort investigated a simple strain energy model to account for the actuation cost for a morphing airfoil, and a multiobjective optimization found tradeoff solutions between low-energy, high-drag and highenergy, low-drag morphing airfoils. Building upon the previous effort, the main purpose of this paper is to formulate the aerodynamic contribution to work on the morphing airfoil. This aerodynamic work term can be added to the strain energy model to compute the total energy required for changing the shape of a morphing airfoil. With this formulation, a beneficial contribution of aerodynamic work could reduce the morphing actuation energy from that associated solely with deformation of the aircraft structure, or an unfavorable contribution of aerodynamic work could increase the morphing actuation energy. Studies presented in this paper illustrate how the aerodynamic work is computed and how the aerodynamic work can be either beneficial or unfavorable. The effect of the morphing airfoil’s relative stiffness on the multi-objective solutions is also presented. Nomenclature i d C = Coefficient of drag at design condition i i l C = Coefficient of lift at design condition i m C = Coefficient of pitching moment f C = Coefficient of skin friction p C = Coefficient of pressure c = Airfoil chord length e K = Unit vector from State 1 to State 2 a f = Actuator force s f = Internal force in spring

Experimental investigation of high-pressure pulsed blowing for dynamic stall control

Abstract: Dynamic stall control using pulsed blowing is compared with control by constant blowing for an OA209 airfoil. Flow control was by blowing from 42 portholes, flush with the airfoil surface, of diameter 1 % chord positioned at 10 % chord and with separation 6.7 % chord. Light stall at Mach 0.3 could be fully suppressed by constant blowing, and for deep stall a pitching moment peak reduction of 65% was seen. For the jet configuration and test cases investigated in this paper, pulsed blowing at 100–500 Hz was found to be at best as effective as constant blowing with the same mass flux for the control of dynamic stall.

Hypersonic Flow Control Using Upstream Focused Energy Deposition

Abstract: A numerical study of centerline and off-centerline power deposition at a point upstream of a two-dimensional blunt body at Mach 6.5 at 30 km altitude are presented. The full Navier-Stokes equations are used. Wave drag, lift, and pitching moment are presented as a function of amount of power absorbed in the flow and absorption point location. It is shown that wave drag is considerably reduced. Modifications to the pressure distribution in the flow field due to the injected energy create lift and a pitching moment when the injection is off-centerline. This flow control concept may lead to effective ways to improve the performance and to stabilize and control hypersonic vehicles.