Novel Concepts for Active Load Alleviation
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Cited by 3 publications
References 34 publications
Active load alleviation can substantially contribute to decrease structural weight and emissions of future transport aircraft by limiting peak aerodynamic loads that the aircraft experiences during flight. Fluidic actuators, as part of active load alleviation systems, have the potential for faster and more complete gust load reduction. The performance of a dual slot circulation control airfoil for gust load alleviation is investigated experimentally on a supercritical airfoil model. The tests are conducted in a low-speed wind tunnel at a chord-based Reynolds number of $${\text{Re}}={\text{1.5}}\cdot {\text{10}}^{{\text{6}}}$$ Re = 1.5 · 10 6 and $${\it{M}}_{{\infty }}={\text {0.14}}$$ M ∞ = 0.14 . The model features an elliptical Coandă geometry integrated into the airfoil’s trailing edge to minimize cruise performance penalty, while still allowing for substantial load reduction. Blowing from a single slot, as well as simultaneously from pressure and suction side slots is tested over a range of blowing rates to assess the impact on load modification. Both steady and impulsive activation performance are evaluated based on surface pressure, integral load, and flow field measurements around the Coandă geometry. High control authority is found for upper and lower single slot blowing, with peak changes in lift coefficient of about $$\pm\,{0.33}$$ ± 0.33 and lift-to-equivalent-drag ratio change of up to 100. Similar peak lift changes and reduced equivalent drag are obtained by adding marginal ($$< 14\%$$ < 14 % of total) blowing from the opposite slot, which also reduces pitching moment changes for primary upper and marginal lower blowing. Impulsive jet activation exhibits load control authority comparable to steady actuation and sufficiently short onset times to counteract all gusts defined by certification documentation.
Active load alleviation can substantially contribute to decrease structural weight and emissions of future transport aircraft by limiting peak aerodynamic loads that the aircraft experiences during flight. Fluidic actuators, as part of active load alleviation systems, have the potential for faster and more complete gust load reduction. The performance of a dual slot circulation control airfoil for gust load alleviation is investigated experimentally on a supercritical airfoil model. The tests are conducted in a low-speed wind tunnel at a chord-based Reynolds number of $${\text{Re}}={\text{1.5}}\cdot {\text{10}}^{{\text{6}}}$$ Re = 1.5 · 10 6 and $${\it{M}}_{{\infty }}={\text {0.14}}$$ M ∞ = 0.14 . The model features an elliptical Coandă geometry integrated into the airfoil’s trailing edge to minimize cruise performance penalty, while still allowing for substantial load reduction. Blowing from a single slot, as well as simultaneously from pressure and suction side slots is tested over a range of blowing rates to assess the impact on load modification. Both steady and impulsive activation performance are evaluated based on surface pressure, integral load, and flow field measurements around the Coandă geometry. High control authority is found for upper and lower single slot blowing, with peak changes in lift coefficient of about $$\pm\,{0.33}$$ ± 0.33 and lift-to-equivalent-drag ratio change of up to 100. Similar peak lift changes and reduced equivalent drag are obtained by adding marginal ($$< 14\%$$ < 14 % of total) blowing from the opposite slot, which also reduces pitching moment changes for primary upper and marginal lower blowing. Impulsive jet activation exhibits load control authority comparable to steady actuation and sufficiently short onset times to counteract all gusts defined by certification documentation.
Unsteady nonlinear lifting line model for active gust load alleviation of airplanes
Active gust load alleviation is an important technology for designing future passenger airplanes to be lighter and thus more environmentally friendly. Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations are typically used to accurately calculate gust loads, but because of their high computational cost, they can only be performed at a few selected operating points. In simpler potential theory models, stall is neglected, resulting in loss of accuracy. In this paper, a low-order unsteady aerodynamics wing model is presented, which is able to represent well compressible flow with stall. Furthermore, the model offers the possibility to modularly incorporate actuators, which allows the design and evaluation of active load alleviation systems. The model is based on a conventional unsteady 2D airfoil model including a dynamic stall model. The dynamic stall model requires viscous steady coefficients, e.g. from 2D steady RANS computations. This 2D airfoil model is coupled with a 3D steady-state lifting line model. The model is applied to the LEISA research airplane and extensively validated with URANS results. It performs well in calculating gust loads with and without simultaneous flap deflections, and provides significantly more accurate results in the case of stall than when stall is neglected.
Studies of preview gust load alleviation [Formula: see text] and [Formula: see text] controllers via synthesis, simulation, wind tunnel tests, and test/simulation correlation are presented in this paper. University of Washington active aeroservoelastic wind tunnel model design, construction, and testing capabilities are used. The test article is a flexible half wing–body–tail model with active control surfaces of two ailerons and an elevator. The model moves in a combination of rigid-body and elastic motions. The commands of gust vanes are used both to generate gusts and to provide real-time preview gust encounter information. A discrete-time linear-time-invariant output feedback system is augmented with various preview lengths of information. The experimental results show that gust loads are reduced with gust preview information compared to feedback-only control and are halved with the fullest gust preview information compared to the open-loop case. The wind tunnel results validated the simulations and added insights to the performance of preview [Formula: see text] and [Formula: see text] control implementation. The closed-loop analysis quantified the margins and robustness of the systems and correlated with the time history of both simulations and experiments. This paper presents preview gust load alleviation robust control test results, not available so far, in a realistic experimental setting.
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