Active Cancellation of Tollmien-Schlichting Instabilities in Compressible Flows Using Closed-Loop Control

Engert, Marcus; Pätzold, Andreas; Becker, Ralf; Nitsche, W.

doi:10.1007/978-1-4020-6858-4_37

Cited by 18 publications

(10 citation statements)

References 5 publications

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“…This rise is attributed to the effect of the cycleto-cycle variation in the stagnation point position increasing as the distance between the sensor and stagnation point increases. Engert and Nitsche (2008) suggest that the Tollmien-Schlichting frequencies relevant to transition at this Mach and Reynolds number are all over 2 kHz, so we cannot be detecting them with the data analysis used. For the detection of transition on a pitching airfoil, the hot-film data can be analysed as suggested in Richter et al (2014).…”

Section: Transition Detection For a Pitching Airfoilmentioning

confidence: 89%

Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

Gardner

Richter

2015

Exp Fluids

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the power required. Additionally the transition affects the resistance of components to boundary layer separation.As seen in Fig. 1 on the example of a flat plate, the boundary layer is characterised by a laminar part near the leading edge which has low turbulence and wall shear stress. At some point, turbulence in the boundary layer is no longer damped, and the turbulence increases along a "transition region" until the boundary layer is fully turbulent. Compared to the laminar region, the turbulent region has higher recovery temperature, wall heat flux, wall shear stress, and higher RMS values of wall static pressure, Pitot pressure and heat flux (Schlichting and Gersten 2006). These characteristics can be used to detect transition, and the detection of boundary layer transition can be performed by a large number of methods (Nitsche and Brunn 2006), most of which work for transition positions which are invariant with time or quasi-steady with regard to the surface temperature distribution, for example: --Skin friction measurements by piezoelectric sensors (Nitsche and Brunn 2006) or oil films for steady flows (Tanner and Blows 1976) or unsteady flows (Schülein 2014). --Measurements of the transition position by sublimation (Velkoff et al. 1971) or China-clay (Richards and Burstall 1945). --Measurements of the wall recovery temperature by thermocouples, temperature-sensitive paint, temperaturesensitive liquid crystals or infrared cameras (Peake et al. 1977). --Measurements of the wall heat transfer by thermocouples, infrared cameras, or direct measurements by hotfilm anemometers (Schultz and Jones 1973). --Measurements of the boundary layer velocity profile by hot-wire anemometers, Pitot tube or PIV (Nitsche and Brunn 2006).Abstract A method of boundary layer transition measurement is presented for wind tunnel models instrumented with surface pressure taps. The measurement relies on taking a number of theoretically identical measurements at different times and then analysing the standard deviation of the pressures. Due to the slight unsteady movement of the transition position, a peak in the standard deviation of pressure σ C P peak is found at the transition position, and this is correlated with measurements of the transition position with an infrared camera and hot-film anemometers. In contrast to microphone measurements, it is shown that the transition detection works for data which have been low-pass filtered with a cut-off of 1 Hz. The application to static and dynamic transition measurements on static and periodically pitching helicopter rotor blade airfoils at Mach 0.3-0.5 is demonstrated.

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Section: Transition Detection For a Pitching Airfoilmentioning

confidence: 89%

Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

Gardner

Richter

2015

Exp Fluids

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“…Figure 8(a) shows that these sensor locations result in controllers that reduce the cost (Eq. (14)) to less than 2% of the uncontrolled cost when applied to both the model and the full system (DNS). It is clear that any sensor position upstream of the actuator results in the same good performance.…”

Section: A Original Actuators and Sensorsmentioning

confidence: 99%

Feedback control of instabilities in the two-dimensional Blasius boundary layer: The role of sensors and actuators

et al. 2013

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We analyze the effects of different types and positions of actuators and sensors on controllers’ performance and robustness in the linearized 2D Blasius boundary layer. The investigation is carried out using direct numerical simulations (DNS). To facilitate controller design, we find reduced-order models from the DNS data using a system identification procedure called the Eigensystem Realization Algorithm. Due to the highly convective nature of the boundary layer and corresponding time delays, the relative position of the actuator and sensor has a strong influence on the closed-loop dynamics. We address this issue by considering two different configurations. When the sensor is upstream of the actuator, corresponding to disturbance-feedforward control, good performance is observed, as in previous work. However, feedforward control can be degraded by additional disturbances or uncertainties in the plant model, and we demonstrate this. We then examine feedback controllers in which the sensor is a short distance downstream of the actuator. Sensors farther downstream of the actuator cause inherent time delays that limit achievable performance. The performance of the resulting feedback controllers depends strongly on the form of actuation introduced, the quantities sensed, and the observability of the structures deformed by the controller's action. These aspects are addressed by varying the spatial distribution of actuator and sensor. We find an actuator-sensor pair that is well-suited for feedback control, and demonstrate that it has good performance and robustness, even in the presence of unmodeled disturbances.

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“…Sturzebecher & Nitsche [14] also investigated a spanwise and a cascaded sensor-actuator arrangement. The promising singleactuator approach was verified in free-flight experiments by Peltzer et al [15], which will be presented in §3a, as well as in high-speed wind-tunnel applications by Engert et al [16], presented in §3b. The next evolutionary step from a cascaded system to a streamwise extended actuation subsequently led to a distributed and wall-integrated configuration [17].…”

Section: Introductionmentioning

confidence: 79%

On active control of laminar–turbulent transition on two-dimensional wings

Erdmann

Pätzold

Engert

et al. 2011

Phil. Trans. R. Soc. A.

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This paper gives an overview of drag reduction on aerofoils by means of active control of Tollmien-Schlichting (TS) waves. Wind-tunnel experiments at Mach numbers of up to M x = 0.42 and model Reynolds numbers of up to Re c = 2 × 10 6 , as well as in-flight experiments on a wing glove at Mach numbers of M < 0.1 and at a Reynolds number of Re c = 2.4 × 10 6 , are presented. Surface hot wires were used to detect the linearly growing TS waves in the transitional boundary layer. Different types of voice-coil-and piezo-driven membrane actuators, as well as active-wall actuators, located between the reference and error sensors, were demonstrated to be effective in introducing counterwaves into the boundary layer to cancel the travelling TS waves. A control algorithm based on the filtered-x least mean square (FxLMS) approach was employed for inflight and high-speed wind-tunnel experiments. A model-predictive control algorithm was tested in low-speed experiments on an active-wall actuator system. For the in-flight experiments, a reduction of up to 12 dB (75% TS amplitude) was accomplished in the TS frequency range between 200 and 600 Hz. A significant reduction of up to 20 dB (90% TS amplitude) in the flow disturbance amplitude was achieved in high-speed wind-tunnel experiments in the fundamental TS frequency range between 3 and 8 kHz. A downstream shift of the laminar-turbulent transition of up to seven TS wavelengths is presented. The cascaded sensor-actuator arrangement given by Sturzebecher & Nitsche in 2003 for lowspeed wind-tunnel experiments was able to shift the transition Dx = 240 mm (18% x/c) downstream by a TS amplitude reduction of 96 per cent (30 dB). By using an active-wall actuator, which is much shorter than the cascaded system, a transition delay of seven TS wavelengths (16 dB TS amplitude reduction) was reached.

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Active Cancellation of Tollmien-Schlichting Instabilities in Compressible Flows Using Closed-Loop Control

Cited by 18 publications

References 5 publications

Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

Feedback control of instabilities in the two-dimensional Blasius boundary layer: The role of sensors and actuators

On active control of laminar–turbulent transition on two-dimensional wings

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