Jesse C Little

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Scholarly Contributions

Chapters

• Borgmann, D., Hosseinverdi, S., Little, J. C., & Fasel, H. F. (2020). Investigation of low-speed boundary-layer instability and transition using experiments, theory and DNS. In AIAA AVIATION Forum. American Institute of Aeronautics and Astronautics.
• Padmanabhan, S., Castro, M. J., Threadgill, J. A., & Little, J. C. (2020). Root Influence on the Unsteady Characteristics of Swept Impinging Oblique SBLIs. In AIAA SciTech Forum. American Institute of Aeronautics and Astronautics.

Journals/Publications

• Little, J. C., & Threadgill, J. A. (2022). Volumetric study of a turbulent boundary layer and swept impinging oblique SBLI at Mach 2.3. Experiments in Fluids, 63(9), 20. doi:10.1007/s00348-022-03433-6
• Padmanabhan, S., Maldonado, J. C., Threadgill, J., & Little, J. C. (2020). Experimental Study of Swept Impinging Oblique Shock/Boundary-Layer Interactions. AIAA Journal, 59(1), 140-149.
• Singh, A., & Little, J. (2020). A comparative study of Ac-dielectric barrier discharge versus Ns-dielectric barrier discharge plasma actuators in an incompressible turbulent mixing layer. Journal of Physics D: Applied Physics, 53(16), 164004.
• Singh, A., & Little, J. (2020). Parametric study of Ns-DBD plasma actuators in a turbulent mixing layer. Experiments in Fluids, 61(2), 36.
• Threadgill, J., & Little, J. C. (2020). An inviscid analysis of swept oblique shock reflections. Journal of Fluid Mechanics, 890, A22.
• Weingaertner, A., Tewes, P., & Little, J. C. (2020). Parallel vortex body interaction enabled by active flow control. Experiments in Fluids, 61(6), 137.
• Little, J. (2019). Localized Thermal Perturbations for Control of Turbulent Shear Flows. AIAA Journal, 57(2), 655-669.
• Little, J., Singh, A., Ashcraft, T., & Durasiewicz, C. (2019). Post-stall flow control using nanosecond pulse driven dielectric barrier discharge plasma actuators. Plasma Sources Science and Technology, 28(1), 014002.
• Otto, C., Tewes, P., Little, J. C., & Woszidlo, R. (2019). Comparison Between Fluidic Oscillators and Steady Jets for Separation Control. AIAA Journal, 57(12), 5220-5229.
• Gross, A., Agate, M., Little, J., & Fasel, H. F. (2018). Numerical Simulation of Plunging Wing Section at High Angles of Attack. AIAA Journal, 56(7), 2514-2527.
• Lehmann, R., Akins, D., & Little, J. (2016). Effects of Nanosecond Pulse Driven Plasma Actuators on Turbulent Shear Layers. AIAA Journal, 54(2), 637-651.
• Sangston, K., Little, J., Eric Lyall, M., & Sondergaard, R. (2016). Effect of Blade Profile Contouring on Endwall Flow Structure in a High-Lift Low-Pressure Turbine Cascade. Journal of Turbomachinery, 139(2), 021006-021006-11.
• Dawson, R. A., & Little, J. (2014). Effects of Pulse Polarity on Nanosecond Pulse Driven Dielectric Barrier Discharge Plasma Actuators. Journal of Applied Physics, 115(4), Article: 043306.
• Sangston, K., Little, J., Lyall, M. E., & Sondergaard, R. (2014). End Wall Loss Reduction of High Lift Low Pressure Turbine Airfoils Using Profile Contouring--Part II: Validation. Journal of Turbomachinery, 136(8), Article: 081006.
• Dawson, R. A., & Little, J. (2013). Effects of pulse polarity on nanosecond pulse driven dielectric barrier discharge plasma actuators. 43rd Fluid Dynamics Conference.
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  Abstract: Nanosecond pulse driven dielectric barrier discharge plasma actuators are studied in quiescent air using a power supply capable of negative and positive polarity waveforms. The effects of pulse amplitude, actuator length and dielectric thickness are also investigated. Schlieren images are used to estimate the relative heating effects for each polarity. Electrical measurements are acquired simultaneously. Negative polarity pulses develop slightly more per unit length energy for thin actuators while positive polarity is slightly higher for thicker actuators. In most cases, the difference in per unit length energy produced by positive and negative pulses on equivalent actuators is not outside the measurement uncertainty. Negative polarity pulses are found to produce a stronger pressure wave across the majority of the test matrix. Results indicate that the negative polarity pulse more efficiently couples electrical energy to the near surface gas as heat. This suggests negative polarity pulses may be preferred for flow control applications.
• Dawson, R., & Little, J. (2013). Characterization of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control. Journal of Applied Physics, 113(10).
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  Abstract: Positive polarity nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators are studied experimentally in quiescent atmosphere. Pulse energy and instantaneous pulse power (hereafter referred to as energy and power) are calculated using simultaneous voltage and current measurements. Electrical characteristics are evaluated as a function of peak voltage, pulse frequency, discharge length, and dielectric thickness. Schlieren imaging is used to provide a relative estimate of discharge energy that is coupled to the near surface gas as heat for the same parameters. Characteristics of the DBD load have a substantial effect on the individual voltage and current traces which are reflected in the energy and power values. Power is mainly dependent on actuator length which is inconsistent with schlieren data as expected. Higher per unit length energy indicates a stronger compression wave for a given actuator geometry, but this is not universally true across different actuators suggesting some constructions more efficiently couple energy to the gas. Energy and compression wave strength are linearly related. Higher pulse frequency produces higher energy but is primarily attributed to heating of the actuator and power supply components and not to an optimal discharge frequency. Both energy and wave strength increase as peak voltage to the power of approximately 3.5 over a substantial range similar to ac-DBD plasma actuators. © 2013 American Institute of Physics.
• Dawson, R., & Little, J. (2013). Parametric investigation of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control. 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013.
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  Abstract: This works builds on our previous nanosecond pulse dielectric barrier discharge (ns-DBD) plasma actuator studies by examining negative polarities. Experimental measurements are performed in quiescent atmosphere. Pulse energy is calculated using simultaneous voltage and current measurements. Electrical characteristics are evaluated as a function of peak voltage, pulse frequency, discharge length and dielectric thickness. Schlieren imaging is used to provide a relative measure of discharge energy that is coupled to the near surface gas as heat for the same parameters. Characteristics of the DBD load have a substantial effect on voltage and current traces, but frequency response remains flat for the majority of test conditions. Both energy and compression wave strength depend primarily on dielectric thickness and secondarily on actuator length. Both pulse energy and compression wave strength increase as peak voltage to the power of approximately 3.5 in the range surveyed. Results agree qualitatively with previous studies of ns-DBDs driven by positive polarity pulses. © 2013 by Jesse Little.
• Ely, R., & Little, J. (2013). Mixing layer excitation by dielectric barrier discharge plasma actuators. 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013.
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  Abstract: The response of an incompressible mixing layer excited near its origin from dielectric barrier discharge (DBD) plasma actuators is studied experimentally. Both alternating current (ac) and nanosecond (ns) pulse driven plasma are investigated in an effort to clarify the mechanisms associated with each technique as well as the more general physics associated with flow control via momentum-based versus thermal actuation. Ac-DBD plasma actuators, which function through electrohydrodynamic effects, are found to generate an increase in mixing layer momentum thickness that is strongly dependent on forcing frequency, amplitude, modulation waveform and actuation location. Results are qualitatively similar to previous archival literature on the topic employing oscillating flaps and sinusoidal signals. Ns-DBD plasma, which is believed to function through thermal effects, has only a slight influence on the mixing layer profile at similar forcing conditions. In the context of previous archival literature, these results suggest different scaling laws and physical mechanisms govern active control via ac-and ns-DBD plasma actuation and more generally, momentum versus thermal perturbations. © 2013 by Jesse Little. Published by the American Institute of Aeronautics and Astronautics, Inc.
• Ely, R., & Little, J. (2013). The mixing layer perturbed by dielectric barrier discharge. 43rd Fluid Dynamics Conference.
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  Abstract: The effects of dielectric barrier discharge (DBD) plasma actuators on a low-speed incompressible turbulent mixing layer are studied experimentally. Both alternating current (ac) and nanosecond (ns) pulse driven plasma are examined in an effort to elucidate the control mechanism for each actuator as well as the general physics governing momentum versus thermal perturbations. Boundary layer suction is employed to analyze the influence of initial conditions on each method. The efficacy of ac-DBD plasma actuators, which function through electrohydrodynamic effects, is found to be dependent on initial mixing layer conditions and frequency. Forcing waveform and amplitude also play a significant role, but are held constant here. Results qualitatively agree with previous literature employing mechanical flaps and sinusoidal waveforms showing the validity of the experiment. Ns-DBD plasma, which is believed to function via thermal effects, is found to produce a slight stabilizing effect that is accompanied by weak fluctuations of the most amplified frequency. The stabilization is unexpected and primarily dependent on the initial conditions and plasma on-time since the employed forcing frequencies behave similarly. These effects are only observed in burst mode forcing. No measureable changes are found using single pulse forcing. The ns-DBD generated pressure waves seem to have no effect on the mixing layer growth. In the context of past studies this suggests that the efficacy of ns-DBD plasma actuators, and likely thermal perturbations in general, is heavily dependent on the scale of energy deposition relative to the initial shear layer conditions. Accordingly, typical amplitude scaling arguments in flow control must be refined for energy deposition actuators.
• Adamovich, I. V., Little, J., Nishihara, M., Takashima, K., & Samimy, M. (2012). Nanosecond pulse surface discharges for high-speed flow control. 6th AIAA Flow Control Conference 2012.
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  Abstract: The paper provides an overview of recent progress in the use of surface dielectric barrier discharges sustained by repetitive, high-voltage, nanosecond duration pulses for high-speed flow control. Experimental studies of diffuse and filamentary surface nanosecond pulse discharges in quiescent air demonstrate that they generate compression waves, due to rapid localized heating produced in the plasma. Compression waves produced by individual discharge filaments have higher amplitude and higher speed compared with waves produced in a diffuse discharge. Unlike surface dielectric barrier discharges sustained by AC voltage waveforms, nanosecond pulse discharges transfer little momentum to quiescent air, suggesting that localized heating and subsequent compression wave formation is the dominant flow control mechanism. Flow separation control using a nanosecond pulse surface discharge plasma actuator on an airfoil leading edge is studied up to M=0.26, Re=1.15·106 (free stream flow velocity 93 m/s), over a wide range of angles of attack. At pre-stall angles of attack, the actuator acts as an active boundary layer trip. At post-stall angles of attack, strong flow perturbations generated by the actuator excite shear layer instabilities and generate coherent spanwise vortices. These coherent structures entrain freestream momentum, thereby reattaching the separated flow to the suction surface of the airfoil. Feasibility of supersonic flow control by low-temperature nanosecond pulse plasma actuators is demonstrated in Mach 5 air flow over a cylinder model. Strong perturbations of a bow shock standing in front of the model are produced by compression waves generated in the plasma. Interaction of the compression waves and the bow shock causes its displacement in the upstream direction, increasing shock stand-off distance by up to 25%. The effect of compression waves generated by nanosecond discharge pulses on shock stand-off distance is demonstrated for single-pulse and quasi-continuous actuator operation. A self-similar kinetic model is developed to analyze energy coupling to the plasma in a surface ionization wave discharge produced by a nanosecond voltage pulse. The model predicts key discharge parameters such as ionization wave speed and propagation distance, electric field, electron density, plasma layer thickness, and pulse energy coupled to the plasma, demonstrating good agreement with available experimental data and two-dimensional kinetic modeling calculations. The model allows an analytic solution and lends itself to incorporating into existing compressible flow codes, for in-depth analysis of the nanosecond discharge plasma flow control mechanism. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
• Dawson, R., & Little, J. (2012). Characterization of nanosecond pulse driven dielectric barrier discharge plasma actuators for aerodynamic flow control. 6th AIAA Flow Control Conference 2012.
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  Abstract: Nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators are studied experimentally in quiescent atmosphere. Per unit length peak energy and instantaneous peak power are calculated using simultaneous voltage and current measurements. Electrical characteristics are evaluated as a function of peak voltage, pulse frequency, discharge length and dielectric thickness. Schlieren imaging is used to provide a relative measure of discharge energy that is coupled to the near surface gas as heat for the same parameters. Characteristics of the DBD load have a substantial effect on the voltage and current traces which are reflected in the peak energy and peak power. Both peak energy and compression wave strength depend primarily on dielectric thickness and secondarily on actuator length although this is not universal in the case of energy necessitating examination of alternative calculation strategies. Peak power is mainly dependent on actuator length which is inconsistent with schlieren data as expected. Higher pulse frequency produces higher pulse energy, but is primarily attributed to heating of the actuator and power supply components. This effect is mainly observed for short actuators. Pulse energy increases as peak voltage to the power 3.5 similar to ac-DBD plasma actuators. A single data set from the center of the test matrix shows compression wave strength increases as voltage to the power 7.4 and energy to the power 1.9 in the range surveyed. © 2012 by Jesse Little.
• Little, J., Takashima, K., Nishihara, M., Adamovich, I., & Samimy, M. (2012). Separation control with nanosecond-pulse-driven dielectric barrier discharge plasma actuators. AIAA Journal, 50(2), 350-365.
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  Abstract: The efficacy of dielectric barrier discharge plasmas driven by high-voltage (∼16 kV) repetitive nanosecond pulses (∼60 ns full width at half-maximum) for flow separation control is investigated experimentally on an airfoil leading edge up to Re = 1 × 106 (62 m=s). Unlike alternating-current dielectric barrier discharges, the nanosecond-pulsedriven dielectric barrier discharge plasma actuator transfers very little momentum to the neutral air, but generates compression waves similar to localized arc-filament plasma actuators. A complex pattern of quasi-planar and spherical compression waves is observed in still air. Measurements suggest that some of these compression waves are generated by discharge filaments that remain fairly reproducible from pulse to pulse. The device performs as an active trip at high-Reynolds-number prestall angles of attack and provides perturbations that generate coherent spanwise vortices at poststall. These coherent structures entrain freestream momentum, thereby reattaching the normally separated flow to the suction surface of the airfoil. Coherent structures are identified at all tested frequencies, but values of F+c + 4-6 are most effective for control. Such devices, which are believed to function through thermal effects, could be an alternative to alternating-current dielectric barrier discharge plasmas, which rely on momentum addition. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
• Rethmel, C., Little, J., Takashima, K., Sinha, A., Adamovich, I., & Samimy, M. (2011). Flow separation control using nanosecond pulse driven DBD plasma actuators. International Journal of Flow Control, 3(4), 213-232.
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  Abstract: This work continues an ongoing effort aimed at development and use of dielectric barrier discharge (DBD) plasma actuators driven by repetitive nanosecond pulses for high Reynolds number aerodynamic flow control. These actuators are believed to influence the flow via a thermal mechanism which is fundamentally different from more commonly studied AC-DBD actuators. Leading edge separation control on an 8-inch chord NACA 0015 airfoil is demonstrated at various post-stall angles of attack for Mach numbers up to 0.26 (free stream velocity up to 93 m/s) and Reynolds numbers up to 1.15 X 106. The nanosecond (NS) pulse driven DBD is shown to extend the stall angle at low Reynolds numbers by functioning as an active trip. At post-stall angles of attack, the device is shown to excite shear layer instabilities and generate coherent spanwise vortices that transfer momentum from the freestream to the separated region, thus reattaching the flow. This is observed for all high Reynolds numbers and Mach numbers spanning the speed range of the subsonic tunnel used in this work. A comparison of leading edge separation control between NS-DBD and AC-DBD plasma actuation demonstrates the increased control authority of NS-DBD plasma at higher flow speeds. The NS-DBD actuator is also integrated into a feedback control system with a stagnation-line-sensing hot film. A simple on/off type controller is developed that operates based on a threshold of the power dissipated by the hot film. An extremum seeking controller is also investigated for dynamically varying Re. Several challenges typically associated with the integration of DBD plasma actuators into a feedback control system have been overcome. The most important of these is the demonstration of control authority at typical aircraft takeoff and landing Mach numbers.
• Little, J., & Samimy, M. (2010). Control of separation from the flap of a high-lift airfoil with DBD plasma actuation. 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition.
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  Abstract: The efficacy of a single dielectric barrier discharge (DBD) plasma actuator for controlling separation from the deflected flap of a high-lift airfoil is investigated between Reynolds numbers of 240,000 (15 m/s) and 750,000 (45 m/s). Calculated momentum coefficients for the DBD plasma actuator are approximately an order of magnitude lower than those usually employed for such studies yet control authority is still realized through amplification of natural vortex shedding from the flap shoulder that promotes momentum transfer between the freestream and separated region. The corresponding lift enhancement is found to be primarily due to increased circulation around the entire model rather than full reattachment to the deflected flap surface. As a whole, these findings compare favorably to studies on a similar high-lift platform using piezoelectric driven zero net mass flux actuation. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.
• Little, J., & Samimy, M. (2010). High-lift airfoil separation with dielectric barrier discharge plasma actuation. AIAA Journal, 48(12), 2884-2898.
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  Abstract: The efficacy of a single dielectric barrier discharge plasma actuator for controlling turbulent boundary-layer separation from the deflected flap of a high-lift airfoil is investigated between Reynolds numbers of 240,000 (15 m/s) and 750,000 (45 m/s). Momentum coefficients for the dielectric barrier discharge plasma actuator are approximately an order of magnitude lower than those usually employed for such studies, yet control authority is still realized through amplification of natural vortex shedding from the flap shoulder, which promotes momentum transfer between the freestream and separated region. This increases dynamic loading on the flap and further organizes turbulent fluctuations in the wake. The measured lift enhancement is primarily due to upstream effects from increased circulation around the entire model, rather than full reattachment to the deflected flap surface. Lift enhancement via instability amplification is found to be relatively insensitive to changes in angle of attack, provided that the separation location and underlying dynamics do not change. The modulation waveform used to excite low-frequency perturbations with a high-frequency plasma-carrier signal has a considerable effect on the actuator performance. Control authority decreases with increasing Reynolds number and flap deflection, highlighting the necessity for further improvement of plasma actuators for use in realistic takeoff and landing transport aircraft applications. These findings are compared to studies on a similar high-lift platform using piezoelectric-driven zero-net-mass flux actuation. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
• Little, J., Nishihara, M., Adamovich, I., & Samimy, M. (2010). High-lift airfoil trailing edge separation control using a single dielectric barrier discharge plasma actuator. Experiments in Fluids, 48(3), 521-537.
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  Abstract: Control of flow separation from the deflected flap of a high-lift airfoil up to Reynolds numbers of 240,000 (15 m/s) is explored using a single dielectric barrier discharge (DBD) plasma actuator near the flap shoulder. Results show that the plasma discharge can increase or reduce the size of the time-averaged separated region over the flap depending on the frequency of actuation. High-frequency actuation, referred to here as quasi-steady forcing, slightly delays separation while lengthening and flattening the separated region without drastically increasing the measured lift. The actuator is found to be most effective for increasing lift when operated in an unsteady fashion at the natural oscillation frequency of the trailing edge flow field. Results indicate that the primary control mechanism in this configuration is an enhancement of the natural vortex shedding that promotes further momentum transfer between the freestream and separated region. Based on these results, different modulation waveforms for creating unsteady DBD plasma-induced flows are investigated in an effort to improve control authority. Subsequent measurements show that modulation using duty cycles of 50-70% generates stronger velocity perturbations than sinusoidal modulation in quiescent conditions at the expense of an increased power requirement. Investigation of these modulation waveforms for trailing edge separation control similarly shows that additional increases in lift can be obtained. The dependence of these results on the actuator carrier and modulation frequencies is discussed in detail. © 2009 Springer-Verlag.
• Little, J., Takashima, K., Nishihara, M., Adamovich, I., & Samimy, M. (2010). High lift airfoil leading edge separation control with nanosecond pulse driven DBD plasma actuators. 5th Flow Control Conference.
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  Abstract: The efficacy of dielectric barrier discharge (DBD) plasmas driven by repetitive nanosecond (NS) pulses for flow separation control is investigated experimentally on an airfoil leading edge up to Re=1×106 (62 m/s). The NS pulse driven DBD plasma actuator (NS-DBD hereafter) transfers very little momentum to the neutral air, but generates compression waves similar to localized arc filament plasma actuators. Experimental results indicate that NS-DBD plasma performs as an active trip at pre-stall angles of attack and provides high amplitude perturbations that manipulate flow instabilities and generate coherent spanwise vortices at post-stall angles. These coherent structures entrain freestream momentum thereby reattaching the normally separated flow to the suction surface of the airfoil. Such devices which are believed to function through thermal effects could result in a significant improvement over AC-DBD plasmas that rely on momentum addition which limits their performance at high speeds. © 2010 by the authors.
• Little, J., Nishihara, M., Adamovich, I., & Samimy, M. (2009). Separation control from the flap of a high-lift airfoil using DBD plasma actuators. 47th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition.
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  Abstract: Control of separation from the deflected flap of a high-lift airfoil is explored using two asymmetric dielectric barrier discharge (DBD) plasma actuators straddling the flap shoulder for Reynolds numbers of 240,000 and 410,000. Actuators are found to be most effective when operated in an unsteady fashion at the natural oscillation frequency of the trailing edge flow field. The use of two actuators shows a significant improvement over one actuator by further decreasing the size of the time-averaged separation bubble on the flap while increasing the pressure fluctuations and velocity fluctuations over the flap and in the wake. Results indicate that the primary mechanism for reducing separation in this configuration is an enhancement of the natural vortex shedding that encourages momentum transfer between the freestream and separated region. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc.
• Malone, J., Debiasi, M., Little, J., & Samimy, M. (2009). Analysis of the spectral relationships of cavity tones in subsonic resonant cavity flows. Physics of Fluids, 21(5).
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  Abstract: 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 frequency over the Mach number range studied provide insight into the variation of the Rossiter mode parameters. The results also indicate that the empirical parameters in the Rossiter equation vary with Mach number for fixed cavity geometry. © 2009 American Institute of Physics.
• Yuan, X., Caraballo, E., Little, J., Debiasi, M., Serrani, A., Özbay, H., Myatt, J. H., & Samimy, M. (2009). Feedback control design for subsonic cavity flows. Applied and Computational Mathematics, 8(1), 70-91.
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  Abstract: A benchmark problem in active aerodynamic flow control, suppression of strong pressure oscillations induced by flow over a shallow cavity, is addressed in this paper. Proper orthogonal decomposition and Galerkin projection techniques are used to obtain a reduced-order model of the flow dynamics from experimental data. The model is made amenable to control design by means of a control separation technique, which makes the control input appear explicitly in the equations. A prediction model based on quadratic stochastic estimation correlates flow field data with surface pressure measurements, so that the latter can be used to reconstruct the state of the model in real time. The focus of this paper is on the controller design and implementation. A linear-quadratic optimal controller is designed on the basis of the reduced-order model to suppress the cavity flow resonance. To account for the limitation on the magnitude of the control signal imposed by the actuator, the control action is modified by a scaling factor, which plays the role of a bifurcation parameter for the closed-loop system. Experimental results, in qualitative agreement with the theoretical analysis, show that the controller achieves a significant attenuation of the resonant tone with a redistribution of the energy into other frequencies, and exhibits a certain degree of robustness when operating in off-design conditions.
• Little, J., Nishihara, M., Adamovich, I., & Samimy, M. (2008). Separation control from the flap of a high-lift airfoil using DBD plasma actuation. 4th AIAA Flow Control Conference.
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  Abstract: This work presents preliminary results of flow separation control from the flap of a high-lift airfoil using a single dielectric barrier discharge (DBD) plasma actuator. Control effectiveness is investigated for two actuator locations as well as various reduced frequencies, applied voltages and waveforms. Results show that a single DBD plasma actuator located at the flap shoulder can slightly increase or reduce the size of the time-averaged separation bubble over the flap depending on the frequency of actuation. This effectiveness is not improved by an increase in applied voltage or a change from a sinusoidal to positive sawtooth waveform for the cases examined. Spatial eigenmodes calculated from two-component PIV using POD show that a single DBD plasma actuator at the flap shoulder can have a significant effect on the structure of higher order modes. However the corresponding energy of these modes is low in comparison to the dominant modes in the wake. Copyright © 2008 by Jesse Little.
• Caraballo, E., Little, J., Debiasi, M., & Samimy, M. (2007). Development and implementation of an experimental-based reduced-order model for feedback control of subsonic cavity flows. Journal of Fluids Engineering, Transactions of the ASME, 129(7), 813-824.
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  Abstract: This work is focused on the development of a reduced-order model based on experimental data for the design of feedback control for subsonic cavity flows. The model is derived by applying the proper orthogonal decomposition (POD) in conjunction with the Galerkin projection of the Navier-Stokes equations onto the resulting spatial eigenfunctions. The experimental data consist of sets of 1000 simultaneous particle image velocimetry (PIV) images and surface pressure measurements taken in the Gas Dynamics and Turbulent Laboratory (GDTL) subsonic cavity flow facility at the Ohio State University. Models are derived for various individual flow conditions as well as for their combinations. The POD modes of the combined cases show some of the characteristics of the sets used. Flow reconstructions with 30 modes show good agreement with experimental PIV data. For control design, four modes capture the main features of the flow. The reduced-order model consists of a system of nonlinear ordinary differential equations for the modal amplitudes where the control input appears explicitly. Linear and quadratic stochastic estimation methods are used for real-time estimation of the modal amplitudes from real-time surface pressure measurements. Copyright © 2007 by ASME.
• Caraballo, E., Little, J., Debiasi, M., Serrani, A., & Samimy, M. (2007). Reduced order model for feedback control of cavity flow - The effects of control input separation. Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting, 19, 13578-13593.
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  Abstract: This work is focused on the development of a new control separation approach for reduced-order 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.
• Little, J., Debiasi, M., Caraballo, E., & Samimy, M. (2007). Effects of open-loop and closed-loop control on subsonic cavity flows. Physics of Fluids, 19(6).
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  Abstract: 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 behavior. In addition, the results reveal substantial differences between the effects of each type of open-loop and closed-loop control. © 2007 American Institute of Physics.
• Samimy, M., Debiasi, M., Caraballo, E., Serrani, A., Yuan, X., Little, J., & Myatt, J. H. (2007). Feedback control of subsonic cavity flows using reduced-order models. Journal of Fluid Mechanics, 579, 315-346.
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  Abstract: Development, experimental implementation, and the results of reduced-order model based feedback control of subsonic shallow cavity flows are presented and discussed. Particle image velocimetry (PIV) data and the proper orthogonal decomposition (POD) technique are used to extract the most energetic flow features or POD eigenmodes. The Galerkin projection of the Navier-Stokes equations onto these modes is used to derive a set of nonlinear ordinary differential equations, which govern the time evolution of the eigenmodes, for the controller design. Stochastic estimation is used to correlate surface pressure data with flow-field data and dynamic surface pressure measurements are used to estimate the state of the flow. Five sets of PIV snapshots of a Mach 0.3 cavity flow with a Reynolds number of 105 based on the cavity depth are used to derive five different reduced-order models for the controller design. One model uses only the snapshots from the baseline (unforced) flow while the other four models each use snapshots from the baseline flow combined with snapshots from an open-loop sinusoidal forcing case. Linear-quadratic optimal controllers based on these models are designed to reduce cavity flow resonance and are evaluated experimentally. The results obtained with feedback control show a significant attenuation of the resonant tone and a redistribution of the energy into other modes with smaller energy levels in both the flow and surface pressure spectra. This constitutes a significant improvement in comparison with the results obtained using open-loop forcing. These results affirm that reduced-order model based feedback control represents a formidable alternative to open-loop strategies in cavity flow control problems even in its current state of infancy. © Cambridge University Press 2007.
• Samimy, M., Debiasi, M., Caraballo, E., Serrani, A., Yuan, X., Little, J., & Myatt, J. H. (2007). Reduced-order model-based feedback control of subsonic cavity flows - An experimental approach. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 95, 211-229.
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  Abstract: The results of an ongoing research activity in the development and implementation of reduced-order model-based feedback control of subsonic cavity flows are presented and discussed. Particle image velocimetry data and the proper orthogonal decomposition technique are used to extract the most energetic flow features or POD eigenmodes. The Galerkin projection of the Navier-Stokes equations onto these modes is used to derive a set of ordinary nonlinear differential equations, which govern the time evolution of the modes, for the controller design. Stochastic estimation is used to correlate surface pressure data with flow field data and dynamic surface pressure measurements are used for real-time state estimation of the flow model. Three sets of PIV snapshots of a Mach 0.3 cavity flow were used to derive three reduced-order models for controller design: (1) snapshots from the baseline (no control) flow, (2) snapshots from an open-loop forced flow, and (3) combined snapshots from the cases 1 and 2. Linear-quadratic optimal controllers based on all three models were designed and tested experimentally. Real-time implementation shows a remarkable attenuation of the resonant tone and a redistribution of the energy into various modes with much lower energy levels. © 2007 Springer-Verlag Berlin Heidelberg.
• Caraballo, E., Little, J., Yuan, X., Debiasi, M., Serrani, A., & Samimy, M. (2006). Reduced-order modeling and control for subsonic cavity flows. Proceedings of the IEEE Conference on Decision and Control, 4603-4608.
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  Abstract: A benchmark problem in active aerodynamic flow control, suppression of pressure oscillations induced by flow over a shallow cavity, is used in this paper to present a comprehensive approach to reduced-order model based flow control. Proper orthogonal decomposition and Galerkin projection techniques are used to obtain a reduced-order model of the flow dynamics from experimental data. The model is made amenable to control design by means of a control separation technique. Quadratic stochastic estimation is used to correlate flow field data with surface pressure measurements to reconstruct the state of the model in real time. Experimental results show that a linear-quadratic controller designed on the basis of the reduced-order model achieves a significant attenuation of the resonant tone with a redistribution of the energy into other frequencies, and exhibits a certain degree of robustness when operating in off-design conditions. © 2006 IEEE.
• Caraballo, E., Yuan, X., Little, J., Debiasi, M., Serrani, A., Myatt, J. H., & Samimy, M. (2006). Further development of feedback control of cavity flow using experimental based reduced order model. Collection of Technical Papers - 44th AIAA Aerospace Sciences Meeting, 22, 16906-16917.
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  Abstract: In our recent work we presented preliminary results for subsonic cavity flow control using a reduced-order model based feedback control derived from experimental measurements. The model was developed using the Proper Orthogonal Decomposition of PIV images in conjunction with the Galerkin projection of the Navier-Stokes equations onto the resulting spatial eigenfunctions. A linear-quadratic optimal controller was designed to reduce cavity flow resonance by controlling the time coefficient and tested in the experiments. The stochastic estimation method was used for real-time estimation of the corresponding time coefficients from 4 dynamic surface pressure measurements. The results obtained showed that the controller was capable of reducing the cavity flow resonance at the design Mach 0.3 flow, as well as at other flows with slightly different Mach number. In the present work we present several improvements made to the method. The reduced order model was derived from a larger set of PIV measurements and we used 6 sensors for the stochastic estimation of the instantaneous time coefficients. The reduced order model so obtained shows a better convergence of the time coefficients. This combined with the 6-sensor estimation improves the control performance while using a scaling factor closer to the theoretically expected value. The controller also performed better in off design flow conditions.
• Debiasi, M., Little, J., Caraballo, E., Yuan, X., Serrani, A., Myatt, J. H., & Samimy, M. (2006). Influence of stochastic estimation on the control of subsonic cavity flow - A preliminary study. Collection of Technical Papers - 3rd AIAA Flow Control Conference, 2, 1181-1195.
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  Abstract: This work alms at understanding how the different elements involved in the feedback loop influence the overall control performance of a subsonic cavity flow based on reduced-order modeling. To this aim we compare preliminary and limited sets of experimental results obtained by modifying some relevant characteristics of the loop. Our results support the findings in the literature that use of quadratic stochastic estimation is preferable to the linear one for real-time update of the model parameters. They also seem to Indicate the merit of using more than one time sample of the pressure for performing the real-time update of the model through stochastic estimation. The effect of using two different sets of pressure signals for the stochastic estimation also corroborates previous findings indicating the need for optimizing the number and the placement of the sensors used in the feedback control loop. Finally we observed that the characteristics of the actuator can alter significantly the overall control effect by introducing in the feedback loop additional, undesirable frequency components that are not modeled and hence controlled. A compensator for the actuator is currently being designed that will alleviate this problem thus enabling a clearer understanding of the overall control technique.
• Little, J., Debiasi, M., & Samimy, M. (2006). Flow structure in controlled and baseline subsonic cavity flows. Collection of Technical Papers - 44th AIAA Aerospace Sciences Meeting, 8, 5697-5714.
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  Abstract: This work presents preliminary results of an experimental investigation of the flow structure and acoustic signature in controlled and baseline subsonic cavity flows. Qualitative and quantitative data are presented and analyzed in an effort to better understand and predict the behavior of the shear layer over the cavity in response to various open-loop actuation cases. Experiments confirm that self-sustained flow-acoustic coupling occurs only at frequencies supporting an integer phase relationship around the flow-acoustic loop. Based on the results, we also speculate that only when the flow-acoustic components at frequencies supporting resonance are time-invariant can the corresponding coupling produces strong acoustic tones. Otherwise the corresponding flow-acoustic couplings produce multi-mode like resonance with tonal switching. This behavior is irrespective of the coherent structures passage frequency in the shear layer. This work is part of a larger multidisciplinary effort in the development and understanding of active feedback flow control techniques (Samimy et al. 2004).
• Yan, P., Debiasi, M., Yuan, X., Little, J., Özbay, H., & Samimy, M. (2006). Experimental study of linear closed-loop control of subsonic cavity flow. AIAA Journal, 44(5), 929-938.
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  Abstract: A study is presented of the modeling and implementation of different concepts for linear feedback control of a single-mode resonance shallow cavity flow. When a physics-based linear model is used for cavity pressure oscillations-, an H∞ controller was designed and tested experimentally. It significantly reduced the main Rossiter mode for which it was designed, while leading to strong oscillations at other Rossiter modes. Other linear control methods such as Smith predictor controller and proportional integral derivative (PID) controller exhibited similar results. The ineffectiveness of using fixed linear models in the design of controllers for the cavity flows is discussed. A modification of the PID design produced a parallel-proportional with time-delay controller that remedied this problem by placing zeros at the frequencies corresponding to other resonance states. Interestingly, it was observed that introducing the same zero to the H∞ controller can also successfully avoid the strong oscillations at other Rossiter modes otherwise observed in the single-mode-based design. The parallel-proportional with time-delay controller was compared to a very effective open-loop method for reducing cavity resonance and exhibited superior robustness with respect to departure of the Mach number from the design conditions. An interpretation is presented for the physical mechanisms by which the open-loop forcing and the parallel-proportional with time-delay controllers reduce the cavity flow noise. The results support the idea that both controls induce in the system a rapid switching between modes competing for the available energy that can be extracted from the mean flow.
• Yuan, X., Caraballo, E., Debiasi, M., Little, J., Serrani, A., Özbay, H., & Samimy, M. (2006). Experimental results and bifurcation analysis on scaled feedback control for subsonic cavity flows. 14th Mediterranean Conference on Control and Automation, MED'06.
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  Abstract: In this paper, we present the latest results of our ongoing research activities in the development of reduced-order models based feedback control of subsonic cavity flows. The model was developed using the Proper Orthogonal Decomposition of Particle Image Velocimetry images in conjunction with the Galerkin projection of the Navier-Stokes equations onto the resulting spatial eigenfunctions. Stochastic Estimation method was used to obtain the state estimation of the Galerkin system from real time surface pressure measurements. A linear-quadratic optimal controller was designed to reduce cavity flow resonance and tested in the experiments. Real-time implementation shows a significant reduction of the sound pressure level within the cavity, with a remarkable attenuation of the resonant tone and a redistribution of the energy into various modes with lower energy levels. A mathematical analysis of the performance of the LQ control, in agreement with the experimental results, is presented and discussed.
• Samimy, M., Debiasi, M., Caraballo, E., Malone, J., Little, J., Özbay, H., Efe, M., Yan, P., Yuan, X., DeBonis, J., Myatt, J. H., & Camphouse, R. C. (2004). Exploring strategies for closed-loop cavity flow control. AIAA Paper, 4845-4860.
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  Abstract: One of the current three main thrust areas of the Collaborative Center of Control Science (CCCS) at The Ohio State University is feedback control of aerodynamic flows. Synergistic capabilities of the flow control team include all of the required multidisciplinary areas of flow simulations, low-dimensional and reduced-order modeling, controller design and experimental integration and implementation of the components along with actuators and sensors. The initial application chosen for study is closed-loop control of shallow subsonic cavity flows. We have made significant progress in the development of various components necessary for reduced-order model based control strategy, which will be presented and discussed in this paper. Stochastic estimation was used to show that surface pressure measurements along with the reduced-order model based on flow-field variables can be used for closed-loop control. Linear controllers such as H ∞. Smith predictor, and PID were implemented experimentally with various degrees of success. The results showed limitations of linear controllers for cavity flow with inherent nonlinear dynamics. Detailed experimental work further explored the physics and showed the highly non-linear nature of the cavity flow and the effects of forcing on the flow structure.

Proceedings Publications

• Little, J. C., Craig, S., Flood, J., Hader, C., Jouannais, L., Threadgill, J. A., Little, J. C., Craig, S., Flood, J., Hader, C., Jouannais, L., Threadgill, J. A., Little, J. C., Craig, S., Flood, J., Hader, C., Jouannais, L., & Threadgill, J. A. (2022, January). Fin-induced Shock Boundary Layer Interactions on a Flat Plate and Hollow Cylinder at Mach 5. In AIAA SCITECH 2022 Forum, 21.
• Little, J. C., Threadgill, J. A., & Padmanabhan, S. (2022, January). Flow Similarity in Swept Shock/Boundary Layer Interactions. In AIAA Scitech 2022 Forum, 18.
• Otto, C., Tewes, P., Little, J. C., & Woszidlo, R. (2019, January). Comparison of Various Fluidic Oscillators for Separation Control on a Wall-Mounted Hump. In AIAA SciTech Forum.
• Padmanabhan, S., Castro, M. J., Threadgill, J. A., & Little, J. C. (2019, January). Experimental Study of Swept Impinging Oblique Shock Boundary Layer Interaction. In AIAA SciTech Forum.
• Threadgill, J. A., Little, J. C., & Wernz, S. H. (2019, January). Transitional Shock Wave Boundary Layer Interactions on a Compression Ramp at Mach 4. In AIAA SciTech Forum.
• Agate, M., Pande, A., Little, J. C., Gross, A., & Fasel, H. F. (2018, January). Active Flow Control of the Laminar Separation Bubble on an Oscillating Airfoil Near Stall. In AIAA SciTech Forum.
• Doehrmann, A. C., Padmanabhan, S., Threadgill, J. A., & Little, J. C. (2018, January). Effect of Sweep on the Mean and Unsteady Structures of Impinging Shock/Boundary Layer Interactions. In AIAA SciTech Forum.
• Durasiewicz, C., Singh, A., & Little, J. C. (2018, January). A Comparative Flow Physics Study of Ns-DBD vs Ac-DBD Plasma Actuators for Transient Separation Control on a NACA 0012 Airfoil. In AIAA SciTech Forum.
• Genschow, K., Tewes, P., Little, J. C., & Wygnanski, I. J. (2018, January). A PIV Study of Baseline and Controlled Flow over a Highly Deflected Flap of a Generic Trapezoidal Wing. In AIAA SciTech Forum.
• Gross, A., Little, J. C., & Fasel, H. F. (2018, January). Numerical Investigation of Shock Wave Turbulent Boundary Layer Interactions. In AIAA SciTech Forum.
• Otto, C., Tewes, P., Little, J. C., & Woszidlo, R. (2018, January). Comparison of Fluidic Oscillators and Steady Jets for Separation Control on a Wall-Mounted Hump. In AIAA SciTech Forum.
• Stab, I., Threadgill, J. A., Little, J. C., & Wernz, S. H. (2018, January). Influence of Flat Plate Leading Edge Sweep and Boundary Layer State on Unswept Shock Boundary Layer Interaction. In AIAA SciTech Forum.
• Threadgill, J. A., & Little, J. C. (2018, June). Volumetric Study of a Turbulent Boundary Layer and Swept Impinging Oblique SBLI at Mach 2.3. In AIAA AVIATION Forum.
• Weingaertner, A., Tewes, P., & Little, J. C. (2018, June). Parallel Vortex Body Interaction Enabled by Active Flow Control. In AIAA AVIATION Forum.
• Agate, M., Little, J. C., Gross, A., & Fasel, H. F. (2017, January). Oscillatory Plunging Motion Applied to an Airfoil Near Stall. In AIAA SciTech Forum.
• Borgmann, D., Pande, A., Little, J. C., & Woszidlo, R. (2017, January). Experimental Study of Discrete Jet Forcing for Flow Separation Control on a Wall Mounted Hump. In AIAA SciTech Forum.
• Gross, A., Little, J. C., & Fasel, H. F. (2017, June). Numerical Simulation of Wing Section Undergoing Plunging Motions at High Angles of Attack. In AIAA AVIATION Forum.
• Singh, A., & Little, J. C. (2017, January). Parametric Investigation of Turbulent Mixing Layer Control using Ns-DBD Plasma Actuators. In AIAA SciTech Forum.
• Threadgill, J. A., Stab, I., Doehrmann, A., & Little, J. C. (2017, January). Three-Dimensional Flow Features of Swept Impinging Oblique Shock/Boundary-Layer Interactions. In AIAA SciTech Forum.
• Ashcraft, T., Decker, K., & Little, J. C. (2016, January). Control of Boundary Layer Separation and the Wake of an Airfoil using ns-DBD Plasma Actuators. In AIAA SciTech Forum.
• Endrikat, S., Roentsch, B., Little, J. C., Taubert, L., Farbos, d., Gutmark, E. J., & Wygnanski, I. J. (2016, January). Physics and Control of the Flow over a Generic Trapezoidal Wing Planform. In AIAA SciTech Forum.
• Gross, A., Little, J. C., & Fasel, H. F. (2016, June). Numerical Simulation of Wing Section Near Stall. In AIAA AVIATION Forum.
• Mertens, C., Pineda, S., Agate, M., Little, J. C., Gross, A., & Fasel, H. F. (2016, January). Effects of Structural Motion on the Aerodynamics of the X-56A Airfoil. In AIAA SciTech Forum.
• Röntsch, B., Taubert, L., Tewes, P., Little, J. C., & Wygnanski, I. J. (2016, June). Application of Active Flow Control to a Generic Low Aspect-Ratio Trapezoidal Wing for High Lift Generation. In AIAA AVIATION Forum.
• Singh, A., & Little, J. C. (2016). Active Control of a Turbulent Mixing Layer using Pulsed Laser and Pulsed Plasma. In AIAA SciTech Forum.
• Caraballo, E., Sullivan, T., & Little, J. (2014, June 16-20). Reduced Order Modeling of Flow Over a NACA 0015 Airfoil for Control Application. In 7th Flow Control Conference.
• Caraballo, E., Sullivan, T., You, R., & Little, J. (2014, January 13-17). Characterization of the Flow Field Over a NACA 0015 Airfoil Using Stochastic Estimation Based on Surface Pressure and Hot Film Measurements. In 52nd Aerospace Sciences Meeting.
• Hainsworth, J., Dawson, R., & Little, J. (2014, June 16-20). Experimental Study of Unswept and Swept Oblique Shock-turbulent Boundary Layer Interactions. In 32nd Applied Aerodynamics Conference.
• Lehmann, R., Little, J., & Akins, D. (2014, June 16-20). Effects of Ns-DBD Plasma Actuators on Turbulent Shear Layers. In 7th Flow Control Conference.

Presentations

• Borgmann, D., & Little, J. C. (2019, November). Experimental Study of Laminar Separation Bubbles with Active Flow Control. APS Division of Fluid Dynamics.
• Little, J. C., Agate, M., & Pande, A. (2019, November). Active flow control of the laminar separation bubble on a plunging airfoil near stall. APS Division of Fluid Dynamics.
• Maldonado, J., Padmanabhan, S., Threadgill, J., & Little, J. C. (2019, November). Root Influence on Swept Impinging Oblique Shock Boundary Layer Interactions. APS Division of Fluid Dynamics.
• Otto, C., Champion, B., Little, J. C., & Woszidlo, R. (2019, November). Flow Physics and Scaling for Discrete Jet Forcing on a Wall-Mounted Hump. APS Division of Fluid Dynamics.
• Padmanabhan, S., Maldonado, J. C., Threadgill, J., & Little, J. C. (2019, November). Mean and Unsteady Characteristics of Swept SBLIs. APS Division of Fluid Dynamics.
• Singh, A., & Little, J. C. (2019, November). Ac-DBD vs Ns-DBD Plasma Actuation on a Turbulent Mixing Layer. APS Division of Fluid Dynamics.
• Threadgill, J., & Little, J. C. (2019, November). Phase Analysis of Disturbances within Transitional Shock Boundary Layer Interactions. APS Division of Fluid Dynamics.
• Little, J. C. (2018, December). High-speed Wind Tunnels and the Hypersonics Initiative at the University of Arizona. U. Arizona Visit to OSD.
• Little, J. C. (2018, February). Hypersonic Research at the University of Arizona. MDA Workshop at U. Arizona.
• Little, J. C. (2018, July). Swept Impinging Oblique Shock Boundary Layer Interactions. AFOSR/ONR High Speed Aero Review Meeting.
• Little, J. C. (2018, May). Plasma Actuators for Aerodynamic Flow Control. AFC Workshop at ARDEC.
• Little, J. C. (2018, November). Swept Impinging Oblique Shock Boundary Layer Interactions. Boeing Seminar Series.
• Agate, M., Little, J., & Fasel, H. (2016, nov). "Effect of Oscillatory Plunging Motion on Airfoil Boundary Layer and Wake Behavior". APS Division of Fluid Dynamics Meeting Abstracts.
• Borgmann, D., Little, J., & Woszidlo, R. (2016, nov). "Spatially Distributed Forcing for Boundary Layer Separation Control on a Wall Mounted Hump". APS Division of Fluid Dynamics Meeting Abstracts.
• Durasiewicz, C., Castro Maldonado, J., & Little, J. (2016, nov). "Active Control of Airfoil Boundary Layer Separation and Wake using Ns-DBD Plasma Actuators". APS Division of Fluid Dynamics Meeting Abstracts.
• Fasel, H. F., Little, J. C., & Gross, A. (2016, June). Impact of Structural Motion on Separation and Separation Control: Integrated Investigation using Numerical Simulations, Theory, Wind-tunnel and Free-flight Experiments. AFOSR/ARO Review Meeting. Arlington, VA: AFOSR/ARO.
• Little, J. C. (2016, Dec). Experimental Study of Discrete Jet Forcing for Flow Separation Control on a Wall Mounted Hump. Boeing Seminar Series. Web: Boeing.
• Little, J. C. (2016, Feb). Nanosecond Pulse Surface Discharges for Control of Turbulent Shear Flows. TU Berlin Seminar. Berlin, Germany: TU Berlin.
• Little, J. C. (2016, Feb). Nanosecond Pulse Surface Discharges for Control of Turbulent Shear Flows. TU Delft Seminar. Delft, Netherlands: TU Delft.
• Little, J. C. (2016, July). Production, Analysis and Control of Vortical Wake-Airfoil Interactions: Harnessing the Unique Capabilities of Active Flow Control for Unsteady Aerodynamics Research. AFOSR/ARO Review Meeting. Arlington, VA: AFOSR/ARO.
• Little, J. C. (2016, Oct). Shock Boundary Layer Interaction: Current Status and Future Trends. Boeing Seminar Series. Web: Boeing.
• Little, J. C., Fasel, H. F., & Gross, A. (2016, June). Investigation of 3D Shock-Boundary Layer Interaction: A Combined Approach using Experiments, Numerical Simulations and Stability Analysis. AFOSR/ONR Review Meeting. Arlington, VA: AFOSR/ONR.
• Little, J., Threadgill, J., & Stab, I. (2016, nov). "Swept Impinging Oblique Shock/Boundary-Layer Interactions". APS Division of Fluid Dynamics Meeting Abstracts.
• Singh, A., & Little, J. (2016, nov). "Turbulent Mixing Layer Control using Ns-DBD Plasma Actuators". APS Division of Fluid Dynamics Meeting Abstracts.
• Stab, I., Threadgill, J., & Little, J. (2016, nov). "Influence of Mach Number and Incoming Boundary Layer on Shock Boundary Layer Interaction". APS Division of Fluid Dynamics Meeting Abstracts.
• Wygnanski, I., Little, J., Roentsch, B., & Endrikat, S. (2016, nov). "Active Flow Control on a Generic Trapezoidal Wing Planform". APS Division of Fluid Dynamics Meeting Abstracts.
• Little, J. C. (2014, February 8). Experimental Fluid Mechanics, Flow Physics and Flow Control. UAS Yuma Consortium Visit. UA, Tucson, AZ.
• Little, J. C. (2014, February 8). Presentation/wind tunnel tour. AME Advisory Board. UA, AME.
• Little, J. C. (2014, July 23). Plasma Actuators for Aerodynamic Flow Control. Naval Surface Warfare Center Carderock Division Seminar. Bethesda, MD.
• Little, J. C. (2014, September 9). Highlights of AME. ENGR 102. UA.