Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session M23: Flow Control V: Actuators II |
Hide Abstracts |
Chair: Thomas Corke, University of Notre Dame Room: 326 |
Tuesday, November 22, 2011 8:00AM - 8:13AM |
M23.00001: Supersonic Jet Noise Reduction Ephraim Gutmark, Nick Heeb, Junhui Liu, Kailas Kailasanath Three noise reduction technologies have been examined experimentally as they have been applied to overexpanded, perfectly expanded and underexpanded supersonic jets from convergent-divergent nozzles. The technologies include chevrons, fluidic injection and fluidically enhanced chevrons. The flowfield was measured by shadowgraph and particle image velocimetry (PIV). The acoustics were measured by near and far-field microphone. Chevrons were shown to reduce or eliminate screech, reduce broadband shock associated noise and reduce mixing noise. Fluidic injection was shown to reduce screech, reduce broadband shock associated noise and mixing noise. It also shifts the shock-associated noise peaks to higher frequency and generates increased high frequency noise as chevrons do. The fluidic injection produces the same reduction near x/D = 10 at mid frequencies and the same increase in high frequencies near the nozzle as chevrons. Both noise reduction techniques reduce the size of the large scale structures and so both reduce BBSN by the same mechanism. The principal difference between chevrons and fluidic injection is that for constant injection mass flow the effectiveness of fluidic injection increases with decreasing values of M$_{j}$ while for chevrons the trend is reversed. [Preview Abstract] |
Tuesday, November 22, 2011 8:13AM - 8:26AM |
M23.00002: Towards Feedback Control of Bypass Transition Using Plasma Actuators Ronald Hanson, Philippe Lavoie, Kyle Bade, Ahmed Naguib Feedback flow control is applied to the transient-growth instability occurring in a Blasius boundary layer for the purpose of delaying bypass transition. The control signal is based on empirical modelling of the input/output flow response. The latter is obtained for both the main disturbance, generated by a roughness element array, as well as the control disturbance, introduced using a spanwise array of plasma actuators. Specifically, the targeted disturbance is characterized with streamwise velocity measurements in cross-flow planes in conjunction with streamwise-wall-shear-stress measurements over two fundamental spanwise disturbance wavelengths, downstream of the actuator location. Correlations between spanwise profiles of the streamwise strear stress and the measured disturbance velocity profiles are used to specify the control signal supplied to the actuators in conjunction with input/output model of the flow response to plasma actuation. The aim of this study is to minimize the residual disturbance energy in a closed-loop framework. [Preview Abstract] |
Tuesday, November 22, 2011 8:26AM - 8:39AM |
M23.00003: The effect of orifice shape on synthetic jet efficiency Barton Smith, David Nani Many studies have demonstrated that synthetic jets can be sensitive to the cavity or orifice shape. In most cases, the performance of the jet with different configurations is compared for fixed driver input voltage or fixed driver displacement. Neither of these quantities accurately reflect the efficiency of the actuator. A sharp inside edge of a synthetic jet orifice can result in separated flow and increased momentum flux (due to the decreased flow area) for a fixed driver displacement. This can lead one to believe that efficiency has been improved, when, in fact, much more power was required for the driver. Similarly, altering the driving waveform from a sinusoid has been reported to improve efficiency. Acoustic power, which is the time-average of volume flow rate through the orifice multiplied by the driving pressure, accurately accounts for the amount of power required to drive the actuator. In this study, we study the efficiency of a round synthetic jet actuator as a function of the radius of the inside of the orifice. Simultaneous PIV at the jet exit and cavity pressure measurements are used to compute the acoustic power required to drive the actuator. The resultant momentum flux of the jet is used as a measure of strength of the jet. Results are obtained for a range of Reynolds numbers and displacement amplitudes. Not surprisingly, it is found that rounding the inside of the orifice improves the efficiency of a synthetic jet. [Preview Abstract] |
Tuesday, November 22, 2011 8:39AM - 8:52AM |
M23.00004: A Parametric Study of Plasma Vortex Generators for Active Flow Control Michael Wicks, Eras Noel, Flint Thomas, Thomas Corke The performance of plasma streamwise vortex generators (PSVG) based on a dielectric barrier discharge is characterized experimentally. A PSVG array is flush mounted on a turbulent boundary layer development plate, which allows control of the flow conditions upstream. The performance of the PSVG is characterized by nonintrusive flow field measurements utilizing both LDV and PIV. The primary metric for characterizing the performance of the PSVG is the magnitude of streamwise vorticity produced. Through a series of experiments the influence of applied voltage, length of surface electrode, inter-electrode spacing, electrode geometry, yaw angle to the oncoming flow and Reynolds number on PSVG performance is documented. The results are compared to passive vortex generators under comparable flow conditions. [Preview Abstract] |
Tuesday, November 22, 2011 8:52AM - 9:05AM |
M23.00005: Flow-field characterization of DBD plasma actuators as discrete roughness elements for laminar flow control S.A. Craig, R.A. Humble, J.W. Hofferth, W.S. Saric For many years there has been an evolving interest in controlling boundary layer transition on swept-wings. With an appropriate distribution of spanwise-periodic discrete roughness elements (DRE), subcritical wavelengths can be excited which supersede the growth of the most-amplified wavelength, thereby delaying the crossflow-dominated laminar-turbulent transition. To elucidate the physics of annular DBD plasma actuators for potential use as DRE and facilitate effective design, they are studied under quiescent flow conditions using particle image velocimetry a photomultiplier tube (PMT) and a high-speed camera. A complex flow-field is generated by a single aperture that describes a three-dimensional torus accompanied by a downward, wall-normal jet region. The flow-field is sensitive to aperture size and applied voltage. For arrayed actuators, the tori contract dramatically due to the interaction with vortices from adjacent apertures. A PMT in conjunction with a high-speed camera were used to observe the light intensity from the bulk plasma at high temporal resolution and visualize the individual discharge events. [Preview Abstract] |
Tuesday, November 22, 2011 9:05AM - 9:18AM |
M23.00006: Active Control of Jet Noise Using High Resolution TRPIV Part 1: POD Analysis Zachary Berger, Stanislav Kostka, Kerwin Low, Matt Berry, Sivaram Gogineni, Mark N. Glauser In the current investigation, we seek to develop advanced flow control techniques for a high speed compressible jet, of nozzle diameter 2''. Using hydrodynamic pressure and 10kHz time-resolved PIV in the near-field, as well as acoustic pressure in the far-field, we implement various techniques to further our understanding of this complex flow field. This work focuses on the near-field velocity measurements for the Mach 0.6 and 0.85 jet. The current 2-component PIV setup allows analysis of the streamwise (r-z) plane of the jet with a 1.5D window. The area of interest is x/D = 3-6 (region of the collapse of the potential core), where there are many potential noise sources propagating to the far-field. In-depth POD analyses will be performed in order to correlate the time-dependent POD coefficients with the pressure signals and develop advanced strategies for closed-loop flow control. For the Mach 0.6 case, at a streamwise location of x/D = 3-4.5, a favorable convergence rate of the spatial eigenvalues can be seen from 1000 snapshots; 45{\%} energy from 20 modes. [Preview Abstract] |
Tuesday, November 22, 2011 9:18AM - 9:31AM |
M23.00007: Active Control of Jet Noise Using High Resolution TRPIV Part 2: Velocity-Pressure-Acoustic Correlations Kerwin Low, Stanislav Kostka, Zachary Berger, Matthew Berry, Sivaram Gogineni, Mark Glauser We investigate the pressure, velocity and acoustic field of a transonic jet. Test conditions comprise a 2 inch nozzle, analyzing two flow speeds, Mach 0.6 and 0.85, with open loop control explored for the Mach 0.6 case. We make simultaneous measurements of the near-field pressure and far-field acoustics at 40 kHz, alongside 10 kHz time resolved PIV measurements in the r-z plane. Cross correlations are performed exploring how both the near-field Fourier filtered pressure and low dimensional POD modes relate to the far-field acoustics. Of interest are those signatures witch exhibit the strongest correlation with far-field, and subsequently how these structures can be controlled. The goal is to investigate how flow-induced perturbations, via synthetic jet actuators, of the developing shear layer might bring insight into how one may alter the flow such that the far-field acoustic signature is mitigated. The TR-PIV measurements will prove to be a powerful tool in being able to track the propagation of physical structures for both the controlled and uncontrolled jet. [Preview Abstract] |
Tuesday, November 22, 2011 9:31AM - 9:44AM |
M23.00008: Active Flow Control on a Low Aspect Ratio Finite Cylinder Edward DeMauro, Chia Min Leong, Michael Amitay Oftentimes, flow control about bluff bodies is investigated using quasi-2D shapes that ignore end effects, whereas real world objects are finite and thus exhibit significant three-dimensional flow fields. Therefore, synthetic-jets-based active flow control was studied on a finite cylinder of low aspect ratio (AR = 3), which incorporates large-scale end effects that must be taken into consideration. Surface pressure measurements indicated that the flow field was significantly modified by the activation of the synthetic jet actuators, when compared to the unforced case. Even with a small momentum input, the synthetic jets induce a large spanwise effect (i.e., along the cylinder span). This large scale alteration of the flow field was confirmed visually using time-averaged stereoscopic PIV measurements in the near wake, showing significant wake narrowing and vectoring, along with changes to vorticity concentrations and turbulent quantities. [Preview Abstract] |
Tuesday, November 22, 2011 9:44AM - 9:57AM |
M23.00009: Separation Control on Generic ROBIN Rotorcraft Fuselage Using Plasma Actuators Dustin Coleman Active flow control, in the form of dielectric barrier discharge (DBD) plasma actuators, is applied to a NASA ROBIN mod7 generic rotorcraft fuselage model. The control objective is reduce the massive 3-D flow separation occurring over the aft ramp section of the fuselage, thereby improving the vehicle flight characteristics. The plasma actuation methods investigated include: plasma streamwise vortex generators (PSVGs), as well as steady and unsteady spanwise actuation, combined with passive geometric modifications to the ramp section. Experiments were conducted at freestream Mach and Reynolds numbers of $M_{\infty} = 0.12$ and Re$_L = 2.65 \times 10^6$, respectively. Aerodynamic loads from each technique were quantified by means of 3-component force balance measurements (drag, lift, and pitching moment), a 128 count static pressure array, and time-resolved PIV wake surveys. Results are compared with previous studies that utilized active flow control in the form of pulsed jets and combustion actuators. [Preview Abstract] |
Tuesday, November 22, 2011 9:57AM - 10:10AM |
M23.00010: ABSTRACT WITHDRAWN |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700