Marco Debiasi

Effects of open-loop and closed-loop control on subsonic cavity flows

This work presents an experimental investigation of the effects of open- and closed-loop control techniques on the flow structure and surface pressure signature in subsonic cavity flows. The cases include the uncontrolled (baseline) Mach 0.30 flow over a shallow cavity of aspect ratio 4 with Reynolds number based on the cavity depth of 105, and four actively controlled flows. The controlled cases include open-loop at two discrete frequencies and two closed-loop cases: parallel proportional with time delay and reduced-order model-based linear quadratic. Measurements and analyses include particle image velocimetry, spectra and spectrograms of surface pressure and velocity fluctuations, flow visualization, and proper orthogonal decomposition. Data are presented and analyzed in an effort to better understand the behavior of the cavity flow in response to a variety of actuation cases. Results show that both open- and closed-loop control have significant effects on the flow dynamics and surface pressure behavio...

Analysis of the spectral relationships of cavity tones in subsonic resonant cavity flows

The understanding of the self-sustained flow-acoustic coupling mechanism in flows over shallow rectangular cavities is of great interest owing to its various practical applications. The ability to understand and predict the resonant frequencies in such flows has recently been advanced through contributions from signal processing theory and by viewing the Rossiter tones as the product of an amplitude modulation process between a fundamental aeroacoustic loop frequency (fa) and a modulating lower frequency. The results obtained using this approach applied to detailed and high-quality spectral data of shallow cavity flow over the Mach number range of 0.20–0.65 are presented and discussed. The new approach, while not a predictive technique, is used to clearly identify all the tones (Rossiter modes, their harmonics, and harmonics of fa) observed in the pressure spectra and to show relationships between the tones. The asymptotic growth with Mach number of fa and the small-step changes of the modulating lower fr...

An electronically tunable duct silencer using dielectric elastomer actuators

A duct silencer with tunable acoustic characteristics is presented in this paper. Dielectric elastomer, a smart material with lightweight, high elastic energy density and large deformation under high direct current/alternating current voltages, was used to fabricate this duct silencer. The acoustic performances and tunable mechanisms of this duct silencer were experimentally investigated. It was found that all the resonance peaks of this duct silencer could be adjusted using external control signals without any additional mechanical part. The physics of the tunable mechanism is further discussed based on the electro-mechanical interactions using finite element analysis. The present promising results also provide insight into the appropriateness of the duct silencer for possible use as next generation acoustic treatment device to replace the traditional acoustic treatment.

Hybrid Design and Performance Tests of a Hovering Insect-inspired Flapping-wing Micro Aerial Vehicle

Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles (FW-MAVs). This paper presents a hybrid design of flapping wing and fixed wing, which combines two flapping wings and two fixed wings to take advantage of the double wing clap-and-fling effect for high thrust production, and utilizes the fixed wings as the stabilizing surfaces for inherently stable hovering flight. Force measurement shows that the effect of wing clap-and-fling significantly enhances the cycle-averaged vertical thrust up to 44.82% at 12.4 Hz. The effect of ventral wing clap-and-fling due to presence of fixed wings produces about 11% increase of thrust-to-power ratio, and the insect-inspired FW-MAV can produce enough cycle-averaged vertical thrust of 14.76 g for lift-off at 10 Hz, and 24 g at maximum frequency of 12.4 Hz. Power measurement indicates that the power consumed for aerodynamic forces and wing inertia, and power loss due to gearbox friction and mechanism inertia was about 80% and 20% of the total input power, respectively. The proposed insect-inspired FW-MAV could endure three-minute flight, and demonstrate a good flight performance in terms of vertical take-off, hovering, and control with an onboard 3.7 V-70 mAh LiPo battery and control system.

Deformation of the Upper and Lower Surfaces of an Airfoil by Macro Fiber Composite Actuators

In this follow-on study, macro fiber composite actuators were used to change the shape of the upper and lower surfaces of an airfoil model with geometry close to that of a NACA 0014. In the design discussed, these thin and light piezoelectric actuators are bonded to the inside and become an integral part of the skin of the upper and lower surfaces of the airfoil. Still-air and wind-tunnel measurements in different flow regimes were performed to assess the characteristics of the static changes of the shape of the airfoil. The results obtained can be used to design a wing with morphing surfaces for improving its aerodynamics, for maneuvering without ailerons, and/or for active control of the flow over the wing.

Shape Change of the Upper Surface of an Airfoil by Macro Fiber Composite Actuators

Macro fiber composite actuators are used to displace inward or outward the upper surface of a NACA 4415 airfoil model. In the design discussed, these thin and light piezoelectric actuators are bonded to the inside and become an integral part of the skin of the upper-surface. Still-air and wind-tunnel measurements in different flow regimes were performed to assess the characteristics of static changes of the shape of the upper surface. The results obtained can be used to design a wing with morphing upper surfaces for improved aerodynamics, for maneuvering without ailerons, or for active control of the flow over the wing.

Acoustic characteristics of a dielectric elastomer absorber.

The present paper is devoted to study the acoustic characteristics of a dielectric elastomer (DE) absorber, which has a wide variety of potential applications as a novel actuator technology. DE, a lightweight and high elastic energy density smart material, can produce a large deformation under high DC/AC voltages. These excellent characteristics can be used to improve the present typical noise control systems. The performance of using this new soft-controlled-material is experimentally investigated. It is found that the voltage on the DE could tune the resonance frequencies of DE absorber thus it could absorb broadband noise. The results also provide insight into the appropriateness of the absorber for possible use as an active noise control system for replacing the traditional acoustic treatment.

Reduced Order Model for Feedback Control of Cavity Flow - the Effects of Control Input Separation

This work is focused on the development of a new control separation approach for reducedorder model based feedback control and its implementation in subsonic cavity flows. The model is derived by applying Proper Orthogonal Decomposition in conjunction with Galerkin projection of the Navier-Stokes equations onto the resulting spatial eigenfunctions. The new method adds the effect of the control input as an additional set of basis. The model is derived for the baseline and a forced flow condition. When the new model was tested numerically, the new separation method showed noticeable changes when the control input was introduced into the system. A feedback controller based on the LQR methodology was designed and tested experimentally in the GDTL subsonic cavity flow facility of The Ohio State University. For control design, 4 modes were sufficient to capture the main features of the cavity flow. While experimental result showed that the new separation approach has similar effect on the flow behavior as our previous approach, we believe that the new methodology is a more suitable procedure for deriving control-oriented models. Furthermore, the new model does not require identification of the control input region in the data used to derive the reduced order model, which is not possible in many flow control applications.

Deformation of The Upper Surface of An Airfoil By Macro Fiber Composite Actuators

In this follow-on study, macro fiber composite actuators are used to change the shape of the upper surface of an airfoil model with geometry close to that of the NACA 4415 type. In the design discussed, these thin and light piezoelectric actuators are bonded to the inside and become an integral part of the skin of the upper surface of the airfoil. The model used in this study incorporates some structural changes that allow a smoother shaping of the surface closer to the leading edge of the airfoil. Still-air and wind-tunnel measurements in different flow regimes are performed to assess the characteristics of the deformation of the upper surface. The results obtained can be used to design a wing with morphing upper surface for improved aerodynamics, for maneuvering without ailerons, and/or for active control of the flow over the wing.

An insect-inspired flapping wing micro air vehicle with double wing clap-fling effects and capability of sustained hovering

We present our recent flying insect-inspired Flapping-Wing Micro Air Vehicle (FW-MAV) capable of hovering flight which we have recently achieved. The FW-MAV has wing span of 22 cm (wing tip-to-wing tip), weighs about 16.6 grams with onboard integration of radio control system including a radio receiver, an electronic speed control (ESC) for brushless motor, three servos for attitude flight controls of roll, pitch, and yaw, and a single cell lithium-polymer (LiPo) battery (3.7 V). The proposed gear box enables the FW-MAV to use one DC brushless motor to synchronously drive four wings and take advantage of the double clap-and-fling effects during one flapping cycle. Moreover, passive wing rotation is utilized to simplify the design, in addition to passive stabilizing surfaces for flight stability. Powered by a single cell LiPo battery (3.7 V), the FW-MAV flaps at 13.7 Hz and produces an average vertical force or thrust of about 28 grams, which is sufficient for take-off and hovering flight. Finally, free flight tests in terms of vertical take-off, hovering, and manual attitude control flight have been conducted to verify the performance of the FW-MAV.