Bulletin of the American Physical Society
2006 59th Annual Meeting of the APS Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida
Session BL: Turbulent Shear Layers I |
Hide Abstracts |
Chair: Mark Glauser, Syracuse University Room: Tampa Marriott Waterside Hotel and Marina Meeting Room 8 |
Sunday, November 19, 2006 11:00AM - 11:13AM |
BL.00001: Flow Control and Dynamical System Development on the Axisymmetric Jet. Jeremy Pinier, Mark Glauser Synthetic jet actuators are used to manipulate the developing shear layer of a high-speed jet and ultimately reduce the perceived far-field sound. In developing closed-loop flow control strategies, a dynamical model of the flow's sound producing region is needed and the effect of the actuation on the flow field measured. In this aim, Dual-Time Stereoscopic PIV (DT-SPIV) measurements in the cross-flow plane are made at downstream positions from 6 to 10 jet diameters, where sound production was shown to be most intense. DT-SPIV consists of taking two Stereo PIV measurements at the same location lagged by a small time, which enables access to the acceleration field. This is necessary in the development of low-order dynamical systems based on experimental data. The effect of the synthetic jet actuation on the flow is measured and incorporated explicitly in the dynamical model for further implementation of advanced flow control. Simultaneously, the far-field sound is measured using an array of 6 microphones to assess the efficiency of the actuators and quantify the correlation between the sound producing region's dynamics and the far-field sound. [Preview Abstract] |
Sunday, November 19, 2006 11:13AM - 11:26AM |
BL.00002: Downstream Evolution of the Near Field Pressure Sources in a High Speed Jet Joseph Hall, Jeremy Pinier, Andre Hall, Mark Glauser To better explore the noise producing features of a high speed jet, measurements of the near field pressure around the periphery of a Mach 0.85 jet are combined with simultaneous measurements of the far-field acoustic pressure to quantify the azimuthal nature of the acoustic pressure sources in jet. Results indicate that the near field pressure is low dimensional and dominated by both azimuthal modes 0 and 1. Only azimuthal mode 0, however, is well correlated with the acoustic far field suggesting that, from a time-averaged perspective, the most efficient near field pressure source is axisymmetric. Using a streamwise microphone array in conjunction with azimuthal filtering, the streamwise evolution of the axisymmetric pressure source is examined, including the convection speed and streamwise growth and decay of the sources in the jet. [Preview Abstract] |
Sunday, November 19, 2006 11:26AM - 11:39AM |
BL.00003: LES of compressible piloted round Jet. Holger Foysi, Sutanu Sarkar The mixing efficiency in low Mach number compressible jets is studied using large eddy simulations. A highly accurate compressible flow solver in cylindrical coordinates has been developed with the ability to simulate flames with infinitely fast chemistry or with a reduced chemical mechanism. Using configurations similar to those of the Sandia Flames, jets up to density ratios of 7 and non-premixed turbulent diffusion flames are simulated. The influence of the density ratio and finite rate chemistry on the mixing process is investigated. The behavior of the jet half width, center-line velocity decay as well as various turbulent quantities are reported. [Preview Abstract] |
Sunday, November 19, 2006 11:39AM - 11:52AM |
BL.00004: Effect of Zero Net-mass Flux Actuators on an Axisymmetric Jet. Carlos Perez, Thomas Boineau, Jeremy Pinier, Mark Glauser In this investigation, piezoelectric driven zero net-mass flux jets, also known as synthetic jets, are used as actuators on an axisymmetric jet with the goal of reducing the latter's far-field noise. A total of six actuators placed on the circumference of the axisymmetric subsonic jet are controlled independently so that each can produce a determined flow output with the ultimate goal of incorporating them in a closed-loop control scheme. The far-field sound, both with and without actuation, is recorded by an array of 6 microphones located at 90, 75, 60, 45, 30 and 15 degrees with respect to the jet centerline axis and positioned at 75 jet diameters from the nozzle exit. In order to better understand the effect of the actuation, stereoscopic PIV is performed perpendicularly to the jet flow at multiple downstream positions. The progress in the effort of understanding the effect of the synthetic jet actuators on the high-speed jet and its far-field sound is discussed. [Preview Abstract] |
Sunday, November 19, 2006 11:52AM - 12:05PM |
BL.00005: Experimental Study of Turbulent Impinging Jets of Dilute Polymer Solutions Ricardo Mejia-Alvarez, Kenneth Christensen Turbulent impinging jets play an important role in a variety of technologically-relevant applications, including cooling, heating and drying operations, drilling and mixing. Many of these applications take advantage of the enhanced of heat transfer commonly observed near the impingement surface where complex vortex interactions are known to exist. Dilute polymer solutions have been observed to stabilize free jets but their impact on further heat-transfer efficiency in the impinging-jet configuration has not been adequately addressed. To this end, the impact of dilute polymer solutions on the structure of turbulent impinging jets is being studied using particle-image velocimetry. Measurements are made for both plain water and dilute polymer solutions ($<100$\,ppm) at comparable Reynolds numbers for various nozzle-to-plate spacings. Instantaneous velocity fields are analyzed to uncover structural modifications imposed by the presence of polymer, particularly in the impingement zone. Turbulence statistics are also computed to assess the overall impact of dilute polymer solutions on this complex turbulent flow. These measurements will be followed by simultaneous velocity--temperature measurements to deduce the impact of dilute polymer solutions on heat transfer in the impingement zone. [Preview Abstract] |
Sunday, November 19, 2006 12:05PM - 12:18PM |
BL.00006: Velocity Field of Isolated Turbulent Puffs Elham Ghaem-Maghami, Hamid Johari The velocity field of isolated turbulent puffs was investigated by the PIV technique. Particular attention was paid to the entrainment pattern of isolated puffs. Puffs were generated by injecting seeded air through a 5 mm diameter nozzle into a flow chamber with a weak co-flow. Puffs with a Reynolds number of 5,000 were examined in the range of 35 -- 75 diameters downstream of the nozzle. The injection time was varied in order to assess the effect of injection volume and impulse on the puff structure. The results indicate that as the injection volume increased, puffs elongated in the axial direction. The largest mean and fluctuating velocities were within the central portion of the puff. The maximum turbulent shear stress within the puff was as much as 2.5 times the steady jet value. The vorticity field showed the presence of vorticity throughout the puff volume. The ratio of volume flow rate at the puff center to the steady jet volume flux at the same location was largest for the smallest injection volume. The majority of entrainment into the puff occurs below the puff center while the puff cap pushes out into surrounding fluid. [Preview Abstract] |
Sunday, November 19, 2006 12:18PM - 12:31PM |
BL.00007: High Reynolds Number Wake of a Body of Revolution with Application to Submarine Wakes Juan Jimenez, Alexander Smits Wake characterization studies over a DARPA SUBOFF submarine model have been conducted in the Princeton University¹s High Reynolds Number Test Facility. The Reynolds Numbers based on model length ranged between $10^6$ and approximately $10^8$, and the wake of the model was studied at locations 3 to 15 diameters downstream. The model was supported by a streamlined strut that was formed by the extension of the sail appendage with no other appendages attached to the body. Mean velocity, turbulence intensities, and spectra information are presented. [Preview Abstract] |
Sunday, November 19, 2006 12:31PM - 12:44PM |
BL.00008: Turbulent Characteristics of Wake Flows of Various Bridge Sections Roi Gurka, Gregory Kopp, Emanuela Palombi Deck geometry is one of the crucial factors that influence the flow characteristics and aeroelastic response of long-bridges. The wake flow patterns of bridge sections become increasingly important when exploring the interaction between the wind and the structure, as designs are becoming longer and lighter. PIV measurements involving flow around elongated cylinders, of various geometries, have been carried out in an open channel wind tunnel. The measurements were performed in the wake region and at the trailing edge. The cylinders tested have an elongation ratio of 7 with leading and trailing edge of distinct rectangular, triangular geometry. The cross-section of the fourth cylinder resembles to the design of the existing storebaelt bridge, found in Denmark. Reynolds stress profiles are presented along with normal stresses in the streamwise-normal plane at the wake region. Auto-correlation functions, as well as the spanwise vorticity are calculated and compared for the different geometries. The relationship that exists between the presence of a vortex street and its influence to the surrounding turbulent activity is demonstrated through these results. Orthogonal decomposition of the data sheds light on the dominant flow structures and on coherent motion interactions. The presented modes reveal the role of the strain field coupled with the vorticity in the wake region. [Preview Abstract] |
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