Flight and Wind-Tunnel Tests of Closed-Loop Active Flow Control

Abstract

Closed-loop active flow control is applied in wind-tunnel tests to an industry-relevant civil aircraft half-model designed by Airbus and in full-scale free-flight experiments with a Stemme S10 glider. The focus of this contribution is on closed-loop control. Moreover, it is shown that our approach can be used for very different setups. For this, the modeling of the dynamic responses of the two systems and the synthesis of robust controllers are compared. For the highly three-dimensional wind-tunnel model, differential pressures are used as surrogate control variables as a correlation with the lift can be described by a lookup table. Two control inputs, pulsed blowing, and two output variables are exploited. In the glider study, with a profile that experiences a mostly two-dimensional flow, an approximate pressure gradient is used instead as a single output to avoid the necessity of such a lookup table. Active flow control is done again, exploiting pulsed blowing. For the controller synthesis, both in the single-input singleoutput and in the multivariable cases, the same approach is used, showing its versatility. In both setups, the closedloop controllers succeed in adjusting the control inputs such that changing reference signals are followed, and the influence of disturbances are attenuated. For the civil aircraft model, completely new landing scenarios can be proposed using the closed-loop controller. Nomenclatureactuation frequency, Hz F L = lift force, N Gjω = frequency response K = Controller _ m = mass flow, kg∕s p = pressure, Pa q = dynamic pressure, Pa Re c = Reynolds number with respect to c S = sensitivity T = complementary sensitivity u = control input, V u, u jet = amplitude of control input, V u ∞ = freestream velocity, m∕s x = nondimensional coordinate y 1 = model parameter, V∕m y 2 = model parameter, V W = weight δ F = flap angle, deg φ = phase, deg ω = angular frequency, rad∕s Subscripts i = model number ref = reference

Active Flow Control for an Outer Wing Model of a Take-off Transport Aircraft Configuration - A Numerical Study

“…Shmilovich and Yadlin 6 ) and in flight testing (e.g. King et al 7 ). However, the leading-edge unprotected wing extension including a wingtip device subject to local flow separation at high AoA at low speed flight, is another noticeable candidate for a flow control application and will be investigated in this work.…”

High Frequency Boundary Layer Actuation by Fluidic Oscillators at High Speed Test Conditions

“…Some concepts use sensor feedback for controllers, e.g. closed-loop designs like in the work of King et al [1]. Other applications are considered to be active if the actuator is switched on and off when needed, as outlined in the review paper by Niehuis and Mack [2].…”

Alleviating Unsteady Aerodynamic Loads with Closed-Loop Flow Control

“…A single pressure sensor was used to track the lift coefficient on a pitching wing [57]. King et al [27] evaluated four pressure signals in full-scale free-flight glider tests. Pfeiffer [3] used different combinations of four pressure sensors on a road vehicle model as surrogates for the drag, side force, and yaw moment coefficients.…”

“…AFC actuators can be designed with low observability. AFC may enable aircraft to execute maneuvers that are not possible with conventional control surfaces [27].…”