Abstract
Transonic buffet not only influences the structural integrity, handling quality and ride comfort, but also limits the flight envelope of transporters and airliners. To delay buffet onset and alleviate the buffet load, the effects of both steady and periodic tangential slot blowing are investigated. The results show that steady tangential blowing on the airfoil upper surface can postpone the buffet onset margin and evidently increase the lift coefficient at incidence angles near and above the buffet onset case of the clean airfoil. Under buffeting conditions of the clean airfoil, unsteady aerodynamic loads can be greatly suppressed by both steady and periodic blowing. The control effort is depicted as reduced wedge effect and weakened dynamic effect. The buffet mechanism includes (a) the feedback loop between the Kutta wave and the separation bubble under the shock foot, and (b) the interaction between the shear layer shed by the shockwave and Kutta waves. Under blowing conditions, the upstream creeping Kutta waves are prevented, and the intensity of the shear layer shed by the shockwave into separated flows is evidently reduced. Parametric studies show that the control effect is reduced as the blowing slot moves downstream, and steady blowing at 41% x/c is the most favorable control case.
Highlights
To save time and energy, high-speed flights are usually done by modern, large commercial aircraft, which always cruise between Mach 0.7 and 0.9 by employing supercritical wings [1,2,3]
Could delay buffet onset, andand an investigated numerically.ItItwas wasfound foundthat thatsteady steadytangential tangentialblowing blowing could delay buffet onset, an evident increase of the lift coefficient was discerned at incidence angles near and exceeding the buffet onset margin of the clean airfoil
In the investigation of buffet load alleviation, both steady and periodic tangential blowing with slots placed at three different chord-wise locations were tested evident increase of the lift coefficient was discerned at incidence angles near and exceeding the buffet onset margin of the clean airfoil
Summary
To save time and energy, high-speed flights are usually done by modern, large commercial aircraft, which always cruise between Mach 0.7 and 0.9 by employing supercritical wings [1,2,3]. Passive control techniques include suction slots on upper wing surfaces, vortex generators with inclined angles, three-dimensional bumps, and so on, while research on active controls includes trailing edge deflectors, flapping rudders, and so on. In the published literature on passive control studies, Thiede and Stanewsky [33] examined the impact of slots ejecting airflow normal to the upper surface of a supercritical airfoil They figured out that the typical normal shock is modified to be two shocks that form a “λ”, which notably decreases the total pressure loss and delays the boundary layer separation induced by the shockwave. Tian et al [14] tested the control effect of an upper trailing-edge flap (UTEF), and they pointed out that the UTEF prevents flow separation downstream of the shockwave, shifts the buffet boundary to higher angles of attack, and increases the lift coefficients. A tangential slot-blowing control method is investigated to test both steady and periodic blowing control effects based on numerical simulations
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