Science.gov

Sample records for aiaa flow control

  1. Flow Control and Measurement in Electric Propulsion Systems: Towards an AIAA Reference Standard

    NASA Technical Reports Server (NTRS)

    Snyder, John Steven; Baldwin, Jeff; Frieman, Jason D.; Walker, Mitchell L. R.; Hicks, Nathan S.; Polzin, Kurt A.; Singleton, James T.

    2013-01-01

    Accurate control and measurement of propellant flow to a thruster is one of the most basic and fundamental requirements for operation of electric propulsion systems, whether they be in the laboratory or on flight spacecraft. Hence, it is important for the electric propulsion community to have a common understanding of typical methods for flow control and measurement. This paper addresses the topic of propellant flow primarily for the gaseous propellant systems which have dominated laboratory research and flight application over the last few decades, although other types of systems are also briefly discussed. While most flight systems have employed a type of pressure-fed flow restrictor for flow control, both thermal-based and pressure-based mass flow controllers are routinely used in laboratories. Fundamentals and theory of operation of these types of controllers are presented, along with sources of uncertainty associated with their use. Methods of calibration and recommendations for calibration processes are presented. Finally, details of uncertainty calculations are presented for some common calibration methods and for the linear fits to calibration data that are commonly used.

  2. Flow Control and Measurement in Electric Propulsion Systems: Towards an AIAA Reference Standard

    NASA Technical Reports Server (NTRS)

    Snyder, John Steven; Baldwin, Jeff; Frieman, Jason D.; Walker, Mitchell L. R.; Hicks, Nathan S.; Polzin, Kurt A.; Singleton, James T.

    2013-01-01

    Accurate control and measurement of propellant flow to a thruster is one of the most basic and fundamental requirements for operation of electric propulsion systems, whether they be in the laboratory or on flight spacecraft. Hence, it is important for the electric propulsion community to have a common understanding of typical methods for flow control and measurement. This paper addresses the topic of propellant flow primarily for the gaseous propellant systems which have dominated laboratory research and flight application over the last few decades, although other types of systems are also briefly discussed. While most flight systems have employed a type of pressure-fed flow restrictor for flow control, both thermal-based and pressure-based mass flow controllers are routinely used in laboratories. Fundamentals and theory of operation of these types of controllers are presented, along with sources of uncertainty associated with their use. Methods of calibration and recommendations for calibration processes are presented. Finally, details of uncertainty calculations are presented for some common calibration methods and for the linear fits to calibration data that are commonly used.

  3. Contributions to the AIAA Guidance, Navigation and Control Conference

    NASA Technical Reports Server (NTRS)

    Campbell, S. D. (Editor)

    2002-01-01

    This report contains six papers presented by the Lincoln Laboratory Air Traffic Control Systems Group at the American Institute of Aeronautics & Astronautics (AIAA) Guidance, Navigation and Control (GNC) conference on 6-9 August 2001 in Montreal, Canada. The work reported was sponsored by the NASA Advanced Air Transportation Technologies (AATT) program and the FAA Free Flight Phase 1 (FFP1) program. The papers are based on studies completed at Lincoln Laboratory in collaboration with staff at NASA Ames Research Center. These papers were presented in the Air Traffic Automation Session of the conference and fall into three major areas: Traffic Analysis & Benefits Studies, Weather/Automation Integration and Surface Surveillance. In the first area, a paper by Andrews & Robinson presents an analysis of the efficiency of runway operations at Dallas/Ft. Worth using a tool called PARO, and a paper by Welch, Andrews & Robinson presents a delay benefit results for the Final Approach Spacing Tool (FAST). In the second area, a paper by Campbell, et al describes a new weather distribution systems for the Center/TRACON Automation System (CTAS) that allows ingestion of multiple weather sources, and a paper by Vandevenne, Lloyd & Hogaboom describes the use of the NOAA Eta model as a backup wind data source for CTAS. Also in this area, a paper by Murphy & Campbell presents initial steps towards integrating weather impacted routes into FAST. In the third area, a paper by Welch, Bussolari and Atkins presents an initial operational concept for using surface surveillance to reduce taxi delays.

  4. An aircraft model for the AIAA controls design challenge

    NASA Technical Reports Server (NTRS)

    Brumbaugh, Randal W.

    1991-01-01

    A generic, state-of-the-art, high-performance aircraft model, including detailed, full-envelope, nonlinear aerodynamics, and full-envelope thrust and first-order engine response data is described. While this model was primarily developed Controls Design Challenge, the availability of such a model provides a common focus for research in aeronautical control theory and methodology. An implementation of this model using the FORTRAN computer language, associated routines furnished with the aircraft model, and techniques for interfacing these routines to external procedures is also described. Figures showing vehicle geometry, surfaces, and sign conventions are included.

  5. Integrated Flight Control and Flow Control Using Synthetic Jet Arrays (Postprint)

    DTIC Science & Technology

    2006-08-01

    A.E., Anders, S.G., Parekh, D.E. and Glezer, A., “Active Flow Control on the Stingray UAV: Transient Behavior,” AIAA Paper 2003-4001, 33rd AIAA Fluid...Dynamics Conference, Orlando, FL, June 2003. 13. Amitay, M., Washburn, A. E., Anders, S. G. and Parekh, D. E., “Active Flow Control on the Stingray

  6. Reactive Flow Control of Delta Wing Vortex (Postprint)

    DTIC Science & Technology

    2006-08-01

    2Amitay, M., Washburn, A.E., Anders, S.G., Parekh, D.E., and Glezer, A., “Active Flow Control on the Stingray UAV: Transient Behavior,” AIAA Paper 2003...on the Stingray Uninhabited Air Vehicle: Transient Behavior,” AIAA Journal, Vol. 42. No. 11, Nov. 2004, pp. 2205-2215. 4 Bevacqua, T., Best, E

  7. Space and Missile Systems Center Tailoring: Tailoring Instructions for AIAA-S-120-2006

    DTIC Science & Technology

    2013-01-02

    space system have been included properly. 4.4.3.4 Customer-Furnished Equipment ( CFE ) The contractor’s mass properties records should have a separate...tabulation of all CFE . 4.5 Documentation Use AIAA-S-120-2006 for all paragraphs except as noted below. 20 4.5.1 Mass Properties Control Plan A

  8. Development and Application of Energetic Actuators for Shear and Vortex Dominated Flow Control

    DTIC Science & Technology

    2014-03-06

    et al. 2008). Although the effect of steady control has been significant in most applications, research has also demonstrated that pulsing the jets ...in a Mach 1.9 and 2.33 flowfield (Samimy et al. 2007 and Caraballo et al. 2009). Pulsed - 10 plasma jets (Webb et al. 2013) have been...AIAA Paper 1026, 2003. 27. McManus, K., and Magill, J., “Separation Control in Incompressible and Compressible Flows using Pulsed Jets ,” AIAA Paper

  9. Global Instability and Control of Low-Pressure Turbine Flows

    DTIC Science & Technology

    2006-03-31

    at moderate Reynolds numbers. Congreso de M~todos Num~ricos en Ingenieria 2005, July 4-7, 2005, Granada, Spain, 2005. Barkley, D. and Henderson, R. D...Methodos Numericos in Ingenieria 2005, Granada Y 3 rd Symposium on Global Flow Instability and Control September 2005 Crete, Greece. * AIAA San

  10. Study and Control of Flow Past Disk, and Circular and Rectangular Cylinders Aligned in the Flow

    NASA Technical Reports Server (NTRS)

    Higuchi, Hiroshi

    2010-01-01

    Methodology similar to that used for our closed-loop control of Separation over NACA 0012 Airfoil (Pinier et al, AIAA Journal 2007) Synthetic Jet Actuators, Miniature Pressure Transducers Split POD with and without Actuations Flow state estimation from Pressure signature

  11. Flow Control and Measurement in Electric Propulsion Systems: Towards an AIAA Reference Standard

    DTIC Science & Technology

    2013-10-01

    Linear Induction Pump for Fission Surface Power, NASA/TP-2010-216430, NASA-MSFC, May 2010. 6. Polzin, K.A., T.E. Markusic, B.J. Stanojev, C. Dodson, and...calculations are presented for some common calibration methods and for the linear fits to calibration data that are commonly used. Nomenclature a...once a year in a procedure that defines accuracy and linearity . Instrument manufacturers generally can provide calibration servicing. Due to the

  12. Flow Control for Supersonic Inlet Applications

    DTIC Science & Technology

    2014-06-10

    1221-1233, May 2013 3. Loth, E., Titchener, N., Babinsky, H., Povinelli , L., “Canonical NSBLI Flows Relevant to External Compression Inlets”, AIAA J...Tennessee, Jan. 9-12, 2012 7. Loth, E.L., Titchener, N., Babinsky, H., Povinelli , L.A., “A Canonical Normal SBLI Flow Relevant to External

  13. AIAA designates Stennis as historic aerospace site

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Picured (left to right) American Institute of Aeronautics and Astronautics (AIAA) representative David Throckmorton presents a plaque designating NASA's John C. Stennis Space Center as a historical aerospace site during an April 10 ceremony. Joining Throckmorton for the presentation were AIAA Greater New Orleans Chapter Chair Mark Hughes, Stennis Space Center Director Bob Cabana and Pratt & Whitney Rocketdyne Vice President John Plowden.

  14. AIAA designates Stennis as historic aerospace site

    NASA Image and Video Library

    2008-04-10

    Picured (left to right) American Institute of Aeronautics and Astronautics (AIAA) representative David Throckmorton presents a plaque designating NASA's John C. Stennis Space Center as a historical aerospace site during an April 10 ceremony. Joining Throckmorton for the presentation were AIAA Greater New Orleans Chapter Chair Mark Hughes, Stennis Space Center Director Bob Cabana and Pratt & Whitney Rocketdyne Vice President John Plowden.

  15. Statistical Analysis of the AIAA Drag Prediction Workshop CFD Solutions

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.; Hemsch, Michael J.

    2007-01-01

    The first AIAA Drag Prediction Workshop (DPW), held in June 2001, evaluated the results from an extensive N-version test of a collection of Reynolds-Averaged Navier-Stokes CFD codes. The code-to-code scatter was more than an order of magnitude larger than desired for design and experimental validation of cruise conditions for a subsonic transport configuration. The second AIAA Drag Prediction Workshop, held in June 2003, emphasized the determination of installed pylon-nacelle drag increments and grid refinement studies. The code-to-code scatter was significantly reduced compared to the first DPW, but still larger than desired. However, grid refinement studies showed no significant improvement in code-to-code scatter with increasing grid refinement. The third AIAA Drag Prediction Workshop, held in June 2006, focused on the determination of installed side-of-body fairing drag increments and grid refinement studies for clean attached flow on wing alone configurations and for separated flow on the DLR-F6 subsonic transport model. This report compares the transonic cruise prediction results of the second and third workshops using statistical analysis.

  16. Flow Control

    DTIC Science & Technology

    2013-04-08

    capture the asymmetric vortex dynamics . These methods were validated by time and fre- quency domain methods . The measurements and modeling methods ...and are time invariant. Protrusions or intrusions will be added along the body’s geometry to induce some type of flow change . These methods yield only...The lag time or presence of non- minimum phase are difficult issues to decouple in the dynamics so further analysis techniques are necessary. 86

  17. AIAA Survivability Technical Committee Draft

    NASA Technical Reports Server (NTRS)

    Shipman, Jim; Williamson, Joel

    1997-01-01

    A relatively new area of interest in aerospace systems survivability is the growing threat of spacecraft penetration by orbital debris. Orbital debris, or "space junk", is composed of the man-made remnants of non-functioning spacecraft still orbiting the Earth. NASA estimates that there are currently over 100,000 orbital debris particles 1 centimeter in diameter or larger that cannot be tracked by existing radar, with the population growing at approximately 4% per year in low earth orbits. With an average velocity of over 8.7 km/sec, these projectiles can penetrate and disable many vulnerable spacecraft systems. Since the likelihood of spacecraft penetration increases with spacecraft surface area, large spacecraft (such as the International Space Station) and communication satellite fleets (such as Iridium) have begun to adopt survivability enhancement strategies similar to those employed by combat aircraft. Collision avoidance maneuvers are commonly practiced by the Space Shuttle and are planned by the International Space Station to decrease their susceptibility to impact by trackable orbital debris; likewise, improved shielding, internal equipment placement, and improved crew operations following penetration can reduce the vulnerability of spacecraft to loss following orbital debris impact. Computer simulations such as the Manned Spacecraft and Crew Survivability (MSCSurv) program at the NASA-Marshall Space Flight Center have recently been developed to quantify and reduce the likelihood of crew or spacecraft loss following orbital debris penetration. The AIAA Survivability Technical Committee is working to enable the transfer of military-developed survivability technologies to help the aerospace industry cope with this growing threat.

  18. Dynamic power flow controllers

    DOEpatents

    Divan, Deepakraj M.; Prasai, Anish

    2017-03-07

    Dynamic power flow controllers are provided. A dynamic power flow controller may comprise a transformer and a power converter. The power converter is subject to low voltage stresses and not floated at line voltage. In addition, the power converter is rated at a fraction of the total power controlled. A dynamic power flow controller controls both the real and the reactive power flow between two AC sources having the same frequency. A dynamic power flow controller inserts a voltage with controllable magnitude and phase between two AC sources; thereby effecting control of active and reactive power flows between two AC sources.

  19. Intelligent Flow Control Valve

    NASA Technical Reports Server (NTRS)

    Kelley, Anthony R (Inventor)

    2015-01-01

    The present invention is an intelligent flow control valve which may be inserted into the flow coming out of a pipe and activated to provide a method to stop, measure, and meter flow coming from the open or possibly broken pipe. The intelligent flow control valve may be used to stop the flow while repairs are made. Once repairs have been made, the valve may be removed or used as a control valve to meter the amount of flow from inside the pipe. With the addition of instrumentation, the valve may also be used as a variable area flow meter and flow controller programmed based upon flowing conditions. With robotic additions, the valve may be configured to crawl into a desired pipe location, anchor itself, and activate flow control or metering remotely.

  20. Gas Flow Controller

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The Mass Flowmeter is a device used to measure flow of oxygen in spacecraft's life support system. Tylan Corporation's Mass Flow Controller's major application is accurate control of reactive gases-- such as hydrogen, phosphine and silane as they are diffused at extremely high temperatures into silicon wafers. Wafers are ultimately cut up into integrated circuits or "chips" for electronic products. Precise process control afforded by the Mass Flow Controller makes it possible to produce circuit chips of greater performance at lower cost.

  1. Dynamics and Control of Turbulent Shear Flows

    DTIC Science & Technology

    1989-05-01

    Significant Results A. Mathematical theory of channel flows. This is a joint research with Professor J. G. Heywood of the University of British Columbia. We...supported by URI contract). J. G. Heywood , Professor, University of British Columbia, consultant. I I I I I I I I I I I 37 Ii I AIAA-88-0134 l The...VISCOUS FLOW PAST PLANE DOMAINS WITH I NIONCOMPACT BOUNDARIES I gJ. G. Heywood Department of Mathematics 3 University of British Columbia I 3 S. S

  2. Microelectromechanical flow control apparatus

    DOEpatents

    Okandan, Murat [NE Albuquerque, NM

    2009-06-02

    A microelectromechanical (MEM) flow control apparatus is disclosed which includes a fluid channel formed on a substrate from a first layer of a nonconducting material (e.g. silicon nitride). A first electrode is provided on the first layer of the nonconducting material outside the flow channel; and a second electrode is located on a second layer of the nonconducting material above the first layer. A voltage applied between the first and second electrodes deforms the fluid channel to increase its cross-sectional size and thereby increase a flow of a fluid through the channel. In certain embodiments of the present invention, the fluid flow can be decreased or stopped by applying a voltage between the first electrode and the substrate. A peristaltic pumping of the fluid through the channel is also possible when the voltage is applied in turn between a plurality of first electrodes and the substrate. A MEM flow control assembly can also be formed by providing one or more MEM flow control devices on a common substrate together with a submicron filter. The MEM flow control assembly can optionally include a plurality of pressure sensors for monitoring fluid pressure and determining flow rates through the assembly.

  3. MHD Flow Control

    DTIC Science & Technology

    2006-09-01

    tested is a model to simulate the hypersonic intake configuration. The corresponding photo is presented in Fig. 49. 75 i I I I I I I Figure 49. The third... hypersonic air stream within the propulsion system inlet. The extra benefit of this proposed Project is the experimental facility to be used for experimental...plasma aerodynamics, and in particular, MHD control of external and internal flows. The MHD control of the external hypersonic flow over the simplest

  4. Tank depletion flow controller

    DOEpatents

    Georgeson, Melvin A.

    1976-10-26

    A flow control system includes two bubbler tubes installed at different levels within a tank containing such as radioactive liquid. As the tank is depleted, a differential pressure transmitter monitors pressure differences imparted by the two bubbler tubes at a remote, shielded location during uniform time intervals. At the end of each uniform interval, balance pots containing a dense liquid are valved together to equalize the pressures. The resulting sawtooth-shaped signal generated by the differential pressure transmitter is compared with a second sawtooth signal representing the desired flow rate during each time interval. Variations in the two signals are employed by a control instrument to regulate flow rate.

  5. Duct Flow Control System.

    DTIC Science & Technology

    is ejected under pressure tangentially of local duct surfaces through Coanda affected slots at the trailing edge of the duct from which only the...channel passages in order to modify the flow stream through the duct so as to perform certain functions such as thrust control and steerage control effects enhancing vehicle maneuverability.

  6. Optimal Flow Control Design

    NASA Technical Reports Server (NTRS)

    Allan, Brian; Owens, Lewis

    2010-01-01

    In support of the Blended-Wing-Body aircraft concept, a new flow control hybrid vane/jet design has been developed for use in a boundary-layer-ingesting (BLI) offset inlet in transonic flows. This inlet flow control is designed to minimize the engine fan-face distortion levels and the first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. This concept represents a potentially enabling technology for quieter and more environmentally friendly transport aircraft. An optimum vane design was found by minimizing the engine fan-face distortion, DC60, and the first five Fourier harmonic half amplitudes, while maximizing the total pressure recovery. The optimal vane design was then used in a BLI inlet wind tunnel experiment at NASA Langley's 0.3-meter transonic cryogenic tunnel. The experimental results demonstrated an 80-percent decrease in DPCPavg, the reduction in the circumferential distortion levels, at an inlet mass flow rate corresponding to the middle of the operational range at the cruise condition. Even though the vanes were designed at a single inlet mass flow rate, they performed very well over the entire inlet mass flow range tested in the wind tunnel experiment with the addition of a small amount of jet flow control. While the circumferential distortion was decreased, the radial distortion on the outer rings at the aerodynamic interface plane (AIP) increased. This was a result of the large boundary layer being distributed from the bottom of the AIP in the baseline case to the outer edges of the AIP when using the vortex generator (VG) vane flow control. Experimental results, as already mentioned, showed an 80-percent reduction of DPCPavg, the circumferential distortion level at the engine fan-face. The hybrid approach leverages strengths of vane and jet flow control devices, increasing inlet performance over a broader operational range with significant reduction in mass flow requirements. Minimal distortion level requirements

  7. Aircraft Laminar Flow Control

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.

    1998-01-01

    Aircraft laminar flow control (LFC) from the 1930's through the 1990's is reviewed and the current status of the technology is assessed. Examples are provided to demonstrate the benefits of LFC for subsonic and supersonic aircraft. Early studies related to the laminar boundary-layer flow physics, manufacturing tolerances for laminar flow, and insect-contamination avoidance are discussed. LFC concept studies in wind-tunnel and flight experiments are the major focus of the paper. LFC design tools are briefly outlined for completeness.

  8. Shaped Recess Flow Control

    NASA Technical Reports Server (NTRS)

    Shyam, Vikram (Inventor); Poinsatte, Philip (Inventor); Thurman, Douglas (Inventor)

    2017-01-01

    One or more embodiments of techniques or systems for shaped recess flow control are provided herein. A shaped recess or cavity can be formed on a surface associated with fluid flow. The shaped recess can be configured to create or induce fluid effects, temperature effects, or shedding effects that interact with a free stream or other structures. The shaped recess can be formed at an angle to a free stream flow and may be substantially "V" shaped. The shaped recess can be coupled with a cooling channel, for example. The shaped recess can be upstream or downstream from a cooling channel and aligned in a variety of manners. Due to the fluid effects, shedding effects, and temperature effects created by a shaped recess, lift-off or separation of cooling jets of cooling channels can be mitigated, thereby enhancing film cooling effectiveness.

  9. Flow Control Technology

    DTIC Science & Technology

    2010-07-01

    downstream of the propeller system. Figure 16 and Figure 17 show the ADV used by Huxley and Hartman [5] as well as a flow diagram for their...Max 17° Figure 23: Power Coefficient of Asymmetric Test Trials vs. Sinusoid pitch schedule. The aim of the work by Huxley and Hartman [5] was...Fagley, Ph.D. candidate, worked with Cadets Thiago Huxley and Christopher Hartman on a feedback controlled cycloidal wave energy converter in

  10. Fundamental Physics and Practical Applications of Electromagnetic Local Flow Control in High Speed Flows

    DTIC Science & Technology

    2010-04-05

    equation turbulence model of Spalart and Allmaras .21 with density corrections of Catris and Aupoix,22 is used JUS the baseline RANS model. The DES...29, No. 6, Dec. 2008. pp. 1638-1649. 21. Spalart , P. R., and Alhnaras. S.R.. "A One-Equation Turbulence Model For Aerodynamic Flows," AIAA Paper No...Figure’ 1 taken from Reference 10. However, these steady simulations are quite unable to accurately simulate unsteady turbulent mixing. A more involved

  11. Controllability of flow turbulence.

    PubMed

    Guan, Shuguang; Wei, G W; Lai, C-H

    2004-06-01

    In this paper, we study the controllability of real-world flow turbulence governed by the two-dimensional Navier-Stokes equations, using strategies developed in chaos control. A case of control/synchronization of turbulent dynamics is observed when only one component of the velocity field vector is unidirectionally coupled to a target state, while the other component is uncoupled. Unlike previous results, it is shown that the dynamics of the whole velocity field cannot be completely controlled/synchronized to the target, even in the limit of long time and strong coupling strength. It is further revealed that the controlled component of the velocity field can be fully controlled/synchronized to the target, but the other component, which is not directly coupled to the target, can only be partially controlled/synchronized to the target. By extending an auxiliary method to distributed dynamic systems, the partial synchronization of two turbulent orbits in the present study can be categorized in the domain of generalized synchronization of spatiotemporal dynamics.

  12. Vortex generator for flow control

    NASA Technical Reports Server (NTRS)

    Collins, Jr., Earl R. (Inventor); Marner, Wilbur J. (Inventor); Rohatgi, Naresh K. (Inventor)

    1989-01-01

    Fluidics flow control of a multiphase supply using a cylindrical chamber is achieved by introducing the supply flow radially into the chamber. The supply flow exits through a port in the center at the chamber. A control fluid is then introduced tangentially about 90.degree. upstream from the supply port. A second control fluid port may be added about 90.degree. upstream from the first control fluid port, but preferably two sets of supply and control ports are added with like ports diametrically opposite each other. The control fluid flows against the circular wall of the control chamber, which introduces a vortex in the flow of the supply flow that decays into a spiral path to the exit port in the center of the chamber. The control flow rate may thus be used to control the spiral path, and therefore the supply flow rate through the exit port.

  13. Wellhead flow control devices

    SciTech Connect

    McLean, D.K.

    1981-09-15

    A wellhead flow control device includes a main flow control valve and associated packings designed for operation under extreme conditions associated with the pumping of high viscosity asphaltic crude wherein the formation includes toxic gases. The formation is produced using steam flooding techniques. The main valve seat and the associated valve closure, consisting of a reciprocating ram and packing plug, are coaxial with the pump polished rod. The valve seat icludes tapered walls defining a shoulder which partially confronts the ram plug. The ram plug is formed of a compressible material formed to the shape of the valve seat. The packing plug is retained on the end of the ram by axial tie rods and a retaining ring. The ring may engage the valve seat shoulder to effect axial compression of the packing plug between the retaining ring and ram face, with consequent radial expansion into the sealing engagement. The ram is reciprocated axially, either manually or hydraulically relative to the ram body. A packing gland, suitable to seal against toxic gases, is provided between the ram and valve body. A rod packing, at the upper end of the ram, includes a primary adjustable packing gland for sealing between the ram and the reciprocating polished rod. 41 claims.

  14. AIAA spacecraft GN&C interface standards initiative: Overview

    NASA Technical Reports Server (NTRS)

    Challoner, A. Dorian

    1995-01-01

    The American Institute of Aeronautics and Astronautics (AIAA) has undertaken an important standards initiative in the area of spacecraft guidance, navigation, and control (GN&C) subsystem interfaces. The objective of this effort is to establish standards that will promote interchangeability of major GN&C components, thus enabling substantially lower spacecraft development costs. Although initiated by developers of conventional spacecraft GN&C, it is anticipated that interface standards will also be of value in reducing the development costs of micro-engineered spacecraft. The standardization targets are specifically limited to interfaces only, including information (i.e. data and signal), power, mechanical, thermal, and environmental interfaces between various GN&C components and between GN&C subsystems and other subsystems. The current emphasis is on information interfaces between various hardware elements (e.g., between star trackers and flight computers). The poster presentation will briefly describe the program, including the mechanics and schedule, and will publicize the technical products as they exist at the time of the conference. In particular, the rationale for the adoption of the AS1773 fiber-optic serial data bus and the status of data interface standards at the application layer will be presented.

  15. AIAA spacecraft GN&C interface standards initiative: Overview

    NASA Technical Reports Server (NTRS)

    Challoner, A. Dorian

    1995-01-01

    The American Institute of Aeronautics and Astronautics (AIAA) has undertaken an important standards initiative in the area of spacecraft guidance, navigation, and control (GN&C) subsystem interfaces. The objective of this effort is to establish standards that will promote interchangeability of major GN&C components, thus enabling substantially lower spacecraft development costs. Although initiated by developers of conventional spacecraft GN&C, it is anticipated that interface standards will also be of value in reducing the development costs of micro-engineered spacecraft. The standardization targets are specifically limited to interfaces only, including information (i.e. data and signal), power, mechanical, thermal, and environmental interfaces between various GN&C components and between GN&C subsystems and other subsystems. The current emphasis is on information interfaces between various hardware elements (e.g., between star trackers and flight computers). The poster presentation will briefly describe the program, including the mechanics and schedule, and will publicize the technical products as they exist at the time of the conference. In particular, the rationale for the adoption of the AS1773 fiber-optic serial data bus and the status of data interface standards at the application layer will be presented.

  16. Statistical Analysis of CFD Solutions from the Third AIAA Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.; Hemsch, Michael J.

    2007-01-01

    The first AIAA Drag Prediction Workshop, held in June 2001, evaluated the results from an extensive N-version test of a collection of Reynolds-Averaged Navier-Stokes CFD codes. The code-to-code scatter was more than an order of magnitude larger than desired for design and experimental validation of cruise conditions for a subsonic transport configuration. The second AIAA Drag Prediction Workshop, held in June 2003, emphasized the determination of installed pylon-nacelle drag increments and grid refinement studies. The code-to-code scatter was significantly reduced compared to the first DPW, but still larger than desired. However, grid refinement studies showed no significant improvement in code-to-code scatter with increasing grid refinement. The third Drag Prediction Workshop focused on the determination of installed side-of-body fairing drag increments and grid refinement studies for clean attached flow on wing alone configurations and for separated flow on the DLR-F6 subsonic transport model. This work evaluated the effect of grid refinement on the code-to-code scatter for the clean attached flow test cases and the separated flow test cases.

  17. Administrator Bolden Speaks at AIAA and WIA Luncheon

    NASA Image and Video Library

    2009-12-09

    NASA Administrator Charles Bolden speaks during a luncheon co-hosted by the American Institute of Aeronautics and Astronautics (AIAA) and Women In Aerospace (WIA) Wednesday, Dec., 9, 2009 at the Ritz-Carlton in Arlington, Va. Photo Credit: (NASA/Bill Ingalls)

  18. Supersonic laminar flow control research

    NASA Technical Reports Server (NTRS)

    Lo, C. F.

    1994-01-01

    The objective of the research is to understand supersonic laminar flow stability, transition and active control. Some prediction techniques will be developed or modified to analyze laminar stability. The effects of supersonic laminar flow with distributed heating and cooling on active control will be studied. The primary tasks of the research applying to the NASA/Ames POC and LFSWT's nozzle design with laminar flow control are as follows: (1) supersonic laminar boundary layer stability and transition prediction; (2) effects of heating and cooling for supersonic laminar flow control; and (3) POC and LFSWT nozzle design with heating and cooling effects combining wall contour and length changes.

  19. Flow Interactions and Control

    DTIC Science & Technology

    2013-03-04

    0 0.1 0.2 0.3 F H T A T H F H average duration of active turbulence fraction of time taken by hibernation Onset of DR average duration of... hibernation Laminar flow Turbulent flow Upper branch ECS Low-drag excursions- hibernation Turbulent bursts Basin boundary: • lower-branch

  20. Supersonic Laminar Flow Control Research

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Wiberg, Clark G.

    1996-01-01

    The objective of this research is to understand supersonic laminar flow stability, transition and active control. Some prediction techniques will be developed or modified to analyze laminar flow stability. The effects of distributed heating and cooling as an active boundary layer control technique will be studied. The primary tasks of the research apply to the NASA/Ames PoC and LFSWT's nozzle design with laminar flow control and are listed as follows: Predictions of supersonic laminar boundary layer stability and transition; Effects of wall heating and cooling on supersonic laminar flow control on a flat plate; Performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths; Effects of a conducted-vs-pulse wall temperature distribution for the LFSWT; and Application of wall heating and/or cooling to laminar boundary layer and flow separation control of airfoils and investigation of related active control techniques.

  1. Supersonic laminar flow control research

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.

    1994-01-01

    The objective of the research is to understand supersonic laminar flow stability, transition, and active control. Some prediction techniques will be developed or modified to analyze laminar flow stability. The effects of supersonic laminar flow with distributed heating and cooling on active control will be studied. The primary tasks of the research applying to the NASA/Ames Proof of Concept (POC) Supersonic Wind Tunnel and Laminar Flow Supersonic Wind Tunnel (LFSWT) nozzle design with laminar flow control are as follows: (1) predictions of supersonic laminar boundary layer stability and transition, (2) effects of wall heating and cooling for supersonic laminar flow control, and (3) performance evaluation of POC and LFSWT nozzles design with wall heating and cooling effects applying at different locations and various length.

  2. Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Park, Michael A.; Nemec, Marian

    2017-01-01

    A summary is provided for the Second AIAA Sonic Boom Workshop held 8-9 January 2017 in conjunction with AIAA SciTech 2017. The workshop used three required models of increasing complexity: an axisymmetric body, a wing body, and a complete configuration with flow-through nacelle. An optional complete configuration with propulsion boundary conditions is also provided. These models are designed with similar nearfield signatures to isolate geometry and shock/expansion interaction effects. Eleven international participant groups submitted nearfield signatures with forces, pitching moment, and iterative convergence norms. Statistics and grid convergence of these nearfield signatures are presented. These submissions are propagated to the ground, and noise levels are computed. This allows the grid convergence and the statistical distribution of a noise level to be computed. While progress is documented since the first workshop, improvement to the analysis methods for a possible subsequent workshop are provided. The complete configuration with flow-through nacelle showed the most dramatic improvement between the two workshops. The current workshop cases are more relevant to vehicles with lower loudness and have the potential for lower annoyance than the first workshop cases. The models for this workshop with quieter ground noise levels than the first workshop exposed weaknesses in analysis, particularly in convective discretization.

  3. Supersonic laminar flow control research

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Wiberg, Clark G.

    1995-01-01

    The objective is to understand supersonic laminar flow stability, transition, and active control. Some prediction techniques will be developed or modified to analyze laminar flow stability. The effects of distributed heating and cooling as an active boundary layer control technique will be studied. The primary tasks of the research apply to the NASA/Ames Proof of Concept (PoC) and Laminar Flow Supersonic Wind Tunnel's (LFSWT's) nozzle design with laminar flow control and are listed as follows: (1) predictions of supersonic laminar boundary layer stability and transition, (2) effects of wall heating and cooling on supersonic laminar flow control, (3) performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths, and (4) effects of a conducted versus pulse wall temperature distribution for the LFSWT.

  4. One-Dimensional Ablation with Pyrolysis Gas Flow Using a Full Newton's Method and Finite Control Volume Procedure

    NASA Technical Reports Server (NTRS)

    Amar, Adam J.; Blackwell, Ben F.; Edwards, Jack R.

    2007-01-01

    The development and verification of a one-dimensional material thermal response code with ablation is presented. The implicit time integrator, control volume finite element spatial discretization, and Newton's method for nonlinear iteration on the entire system of residual equations have been implemented and verified for the thermochemical ablation of internally decomposing materials. This study is a continuation of the work presented in "One-Dimensional Ablation with Pyrolysis Gas Flow Using a Full Newton's Method and Finite Control Volume Procedure" (AIAA-2006-2910), which described the derivation, implementation, and verification of the constant density solid energy equation terms and boundary conditions. The present study extends the model to decomposing materials including decomposition kinetics, pyrolysis gas flow through the porous char layer, and a mixture (solid and gas) energy equation. Verification results are presented for the thermochemical ablation of a carbon-phenolic ablator which involves the solution of the entire system of governing equations.

  5. Transmission series power flow control

    SciTech Connect

    Nelson, R.J.; Bian, J.; Williams, S.L.

    1994-12-31

    This paper presents the characteristics of two gate turn-off (GTO) thyristor voltage-sourced inverter-based series power flow control devices, namely the Series Power Flow Controller (SPFC) and the Unified Power Flow Controller (UPFC). These devices represent series extensions of the STATCON, an inverter-based shunt device developed under a tailored collaboration by EPRI, TVA and the Westinghouse Science and Technology Center, which will soon be placed in service on the TVA 161kV transmission system for transmission voltage control. Operation of the SPFC and UPFC is illustrated through the use of easily-constructed circle diagrams on the P-Q plane. The circle diagrams provide the transmission planning engineer with a simple means to assess the performance of these devices on the transmission system. A concluding example illustrates that the UPFC provides a level of power flow control which is unattainable with more conventional devices.

  6. Summary and Statistical Analysis of the First AIAA Sonic Boom Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Park, Michael A.; Morgenstern, John M.

    2014-01-01

    A summary is provided for the First AIAA Sonic Boom Workshop held 11 January 2014 in conjunction with AIAA SciTech 2014. Near-field pressure signatures extracted from computational fluid dynamics solutions are gathered from nineteen participants representing three countries for the two required cases, an axisymmetric body and simple delta wing body. Structured multiblock, unstructured mixed-element, unstructured tetrahedral, overset, and Cartesian cut-cell methods are used by the participants. Participants provided signatures computed on participant generated and solution adapted grids. Signatures are also provided for a series of uniformly refined workshop provided grids. These submissions are propagated to the ground and loudness measures are computed. This allows the grid convergence of a loudness measure and a validation metric (dfference norm between computed and wind tunnel measured near-field signatures) to be studied for the first time. Statistical analysis is also presented for these measures. An optional configuration includes fuselage, wing, tail, flow-through nacelles, and blade sting. This full configuration exhibits more variation in eleven submissions than the sixty submissions provided for each required case. Recommendations are provided for potential improvements to the analysis methods and a possible subsequent workshop.

  7. Application of Exactly Linearized Error Transport Equations to AIAA CFD Prediction Workshops

    NASA Technical Reports Server (NTRS)

    Derlaga, Joseph M.; Park, Michael A.; Rallabhandi, Sriram

    2017-01-01

    The computational fluid dynamics (CFD) prediction workshops sponsored by the AIAA have created invaluable opportunities in which to discuss the predictive capabilities of CFD in areas in which it has struggled, e.g., cruise drag, high-lift, and sonic boom pre diction. While there are many factors that contribute to disagreement between simulated and experimental results, such as modeling or discretization error, quantifying the errors contained in a simulation is important for those who make decisions based on the computational results. The linearized error transport equations (ETE) combined with a truncation error estimate is a method to quantify one source of errors. The ETE are implemented with a complex-step method to provide an exact linearization with minimal source code modifications to CFD and multidisciplinary analysis methods. The equivalency of adjoint and linearized ETE functional error correction is demonstrated. Uniformly refined grids from a series of AIAA prediction workshops demonstrate the utility of ETE for multidisciplinary analysis with a connection between estimated discretization error and (resolved or under-resolved) flow features.

  8. Workshop report for the AIAA 6th Aeroacoustics Conference

    NASA Astrophysics Data System (ADS)

    Tam, C. K. W.

    1981-12-01

    Summaries are given of the workshops conducted at the AIAA 6th Aeroacoustics Conference, each summary having been prepared 9y the workshop chairman. The six workshops are: jet noise, duct acoustics, turbomachinery noise, aircraft interior noise, airframe and propulsive lift noise, and propeller and helicopter noise. It is noted that the primary purpose of the workshops is to provide a forum where new ideas and concepts can be openly discussed and controversies freely debated.

  9. Supersonic laminar flow control research

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Wiberg, Clark G.

    1995-01-01

    The objective of this research is to understand supersonic laminar flow stability, transition and active control. Some prediction techniques will be developed or modified to analyze laminar flow stability. The effects of distributed heating and cooling as an active boundary layer control technique will be studied. The primary tasks of the research apply to the NASA/Ames PoC and LFSWT's nozzle design with laminar flow control and are listed as follows: (1) predictions of supersonic laminar boundary layer stability and transition; (2) effects of wall heating and cooling on supersonic laminar flow control; (3) performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths; and (4) effects of a conducted -vs- pulse wall temperature distribution for the LFSWT.

  10. Supersonic Laminar Flow Control Research

    NASA Technical Reports Server (NTRS)

    Lo, C. F.; Wiberg, Clark G.

    1996-01-01

    The objective of this research is to understand supersonic laminar flow stability, transition and active control. Some prediction techniques are developed or modified to analyze laminar flow stability. The effects of distributed heating and cooling as an active boundary layer control technique are studied. The primary tasks of the research apply to the NASA/Ames Proof-of-Concept (PoC) and the Laminar Flow Supersonic Wind Tunnel's (LFSWT's) nozzle design with laminar flow control and are listed as follows: (1) Predictions of supersonic laminar boundary layer stability and transition; (2) Effects of wall heating and cooling on supersonic laminar flow control on a flat plate; (3) Performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths; (4) Effects of a conducted -vs- pulse wall temperature distribution for the LFSWT; and (5) Application of wall heating and/or cooling to laminar boundary layer and flow separation control of airfoils and investigation of related active control techniques.

  11. Actuators for Active Flow Control

    NASA Astrophysics Data System (ADS)

    Cattafesta, Louis N., III; Sheplak, Mark

    2011-01-01

    Actuators are transducers that convert an electrical signal to a desired physical quantity. Active flow control actuators modify a flow by providing an electronically controllable disturbance. The field of active flow control has witnessed explosive growth in the variety of actuators, which is a testament to both the importance and challenges associated with actuator design. This review provides a framework for the discussion of actuator specifications, characteristics, selection, design, and classification for aeronautical applications. Actuator fundamentals are discussed, and various popular actuator types used in low-to-moderate speed flows are then described, including fluidic, moving object/surface, and plasma actuators. We attempt to highlight the strengths and inevitable drawbacks of each and highlight potential future research directions.

  12. Transmission series power flow control

    SciTech Connect

    Nelson, R.J.; Bian, J.; Williams, S.L.

    1995-01-01

    This paper presents the characteristics of two gate turn-off (GTO) thyristor voltage-sourced inverter based series power flow control devices, namely the Series Power Flow Controller (SPFC) and the Unified Power Flow Controller (UPFC). These devices represent series extensions of the STATCON, an inverter-based shunt device developed under a tailored collaboration by EPRI, TVA and the Westinghouse Science and Technology Center, which will soon be placed in service on the TVA 161kV transmission system for transmission voltage control. Operation of the SPFC and UPFC is illustrated through the use of easily-constructed circle diagrams on the P-Q plane. The circle diagrams provide the transmission planning engineer with a simple means to assess the performance of these devices on the transmission system. A concluding example illustrates that the UPFC provides a level of power now control which is unattainable with more conventional devices.

  13. Biomimetic Flow Control

    NASA Technical Reports Server (NTRS)

    Anders, John B.

    2000-01-01

    Biologic flight has undoubtedly intrigued man for thousands of years, yet it has been only the last 100 years or so that any serious challenge has been mounted to the pre-eminence of birds. Although present-day large-scale aircraft are now clearly able to fly higher, faster and farther than any bird or insect, it is obvious that these biological creatures have a mastery of low Reynolds number, unsteady flows that is unrivaled by man-made systems. This paper suggests that biological flight should be examined for mechanisms that may apply to engineered flight systems, especially in the emerging field of small-scale, uninhabited aerial vehicles (UAV). This paper discusses the kinematics and aerodynamics of bird and insect flight, including some aspects of unsteady aerodynamics. The dynamics of flapping wing flight is briefly examined, including gait selection, flapping frequency and amplitude selection, as well as wing planform and angle-of-attack dynamics. Unsteady aerodynamic mechanisms as practiced by small birds and insects are reviewed. Drag reduction morphologies of birds and marine animals are discussed and fruitful areas of research are suggested.

  14. Pressure compensated flow control valve

    DOEpatents

    Minteer, Daniel J.

    1999-01-01

    The invention is an air flow control valve which is capable of maintaining a constant flow at the outlet despite changes in the inlet or outlet pressure. The device consists of a shell assembly with an inlet chamber and outlet chamber separated by a separation plate. The chambers are connected by an orifice. Also located within the inlet chamber is a port controller assembly. The port controller assembly consists of a differential pressure plate and port cap affixed thereon. The cap is able to slide in and out of the orifice separating the inlet and outlet chambers. When the pressure differential is sufficient, the differential pressure plate rises or falls to maintain a constant air flow. Movement of the port controller assembly does not require the use of seals, diaphragms, tight tolerances, bushings, bearings, hinges, guides, or lubricants.

  15. Overview of Laminar Flow Control

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.

    1998-01-01

    The history of Laminar Flow Control (LFC) from the 1930s through the 1990s is reviewed and the current status of the technology is assessed. Early studies related to the natural laminar boundary-layer flow physics, manufacturing tolerances for laminar flow, and insect-contamination avoidance are discussed. Although most of this publication is about slot-, porous-, and perforated-suction LFC concept studies in wind tunnel and flight experiments, some mention is made of thermal LFC. Theoretical and computational tools to describe the LFC aerodynamics are included for completeness.

  16. Hybrid laminar flow control study

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Hybrid laminar flow control (HLFC) in which leading edge suction is used in conjunction with wing pressure distribution tailoring to postpone boundary layer transition and reduce friction drag was examined. Airfoil design characteristics required for laminar flow control (LFC) were determined. The aerodynamic design of the HLFC wing for a 178 passenger commercial turbofan transport was developed, and a drag was estimated. Systems changes required to install HLFC were defined, and weights and fuel economy were estimated. The potential for 9% fuel reduction for a 3926-km (2120-nmi) mission is identified.

  17. Supersonic laminar-flow control

    NASA Technical Reports Server (NTRS)

    Bushnell, Dennis M.; Malik, Mujeeb R.

    1987-01-01

    Detailed, up to date systems studies of the application of laminar flow control (LFC) to various supersonic missions and/or vehicles, both civilian and military, are not yet available. However, various first order looks at the benefits are summarized. The bottom line is that laminar flow control may allow development of a viable second generation SST. This follows from a combination of reduced fuel, structure, and insulation weight permitting operation at higher altitudes, thereby lowering sonic boom along with improving performance. The long stage lengths associated with the emerging economic importance of the Pacific Basin are creating a serious and renewed requirement for such a vehicle. Supersonic LFC techniques are discussed.

  18. Overview and Summary of the Second AIAA High Lift Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.; Slotnick, Jeffrey P.

    2014-01-01

    The second AIAA CFD High-Lift Prediction Workshop was held in San Diego, California, in June 2013. The goals of the workshop continued in the tradition of the first high-lift workshop: to assess the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in landing/takeoff (high-lift) configurations. This workshop analyzed the flow over the DLR-F11 model in landing configuration at two different Reynolds numbers. Twenty-six participants submitted a total of 48 data sets of CFD results. A variety of grid systems (both structured and unstructured) were used. Trends due to grid density and Reynolds number were analyzed, and effects of support brackets were also included. This paper analyzes the combined results from all workshop participants. Comparisons with experimental data are made. A statistical summary of the CFD results is also included.

  19. Plans and Example Results for the 2nd AIAA Aeroelastic Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Heeg, Jennifer; Chwalowski, Pawel; Schuster, David M.; Raveh, Daniella; Jirasek, Adam; Dalenbring, Mats

    2015-01-01

    This paper summarizes the plans for the second AIAA Aeroelastic Prediction Workshop. The workshop is designed to assess the state-of-the-art of computational methods for predicting unsteady flow fields and aeroelastic response. The goals are to provide an impartial forum to evaluate the effectiveness of existing computer codes and modeling techniques, and to identify computational and experimental areas needing additional research and development. This paper provides guidelines and instructions for participants including the computational aerodynamic model, the structural dynamic properties, the experimental comparison data and the expected output data from simulations. The Benchmark Supercritical Wing (BSCW) has been chosen as the configuration for this workshop. The analyses to be performed will include aeroelastic flutter solutions of the wing mounted on a pitch-and-plunge apparatus.

  20. LAVA Simulations for the AIAA Sonic Boom Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Housman, Jeffrey A.; Sozer, Emre; Moini-Yekta , Shayan; Kiris, Cetin C.

    2014-01-01

    Computational simulations using the Launch Ascent and Vehicle Aerodynamics (LAVA) framework are presented for the First AIAA Sonic Boom Prediction Workshop test cases. The framework is utilized with both structured overset and unstructured meshing approaches. The three workshop test cases include an axisymmetric body, a Delta Wing-Body model, and a complete low-boom supersonic transport concept. Solution sensitivity to mesh type and sizing, and several numerical convective flux discretization choices are presented and discussed. Favorable comparison between the computational simulations and experimental data of nearand mid-field pressure signatures were obtained.

  1. Valve for controlling solids flow

    DOEpatents

    Staiger, M. Daniel

    1985-01-01

    A valve for controlling the flow of solids comprises a vessel having an overflow point, an inlet line for discharging solids into the vessel positioned within the vessel such that the inlet line's discharge point is lower than the vessel's overflow point, and apparatus for introducing a fluidizing fluid into the vessel. The fluidizing fluid fluidizes the solids within the vessel so that they overflow at the vessel's overflow point. For the removal of nuclear waste product the vessel may be placed within a sealed container having a bottom connected transport line for transporting the solids to storage or other sites. The rate of solids flow is controlled by the flow rate of the fluidizing fluid and by V-notch weirs of different sizes spaced about the top of the vessel.

  2. Valve for controlling solids flow

    DOEpatents

    Staiger, M.D.

    1982-09-29

    A valve for controlling the flow of solids comprises a vessel having an overflow point, an inlet line for discharging solids into the vessel positioned within the vessel such that the inlet line's discharge point is lower than the vessel's overflow point, and means for introducing a fluidizing fluid into the vessel. The fluidizing fluid fluidizes the solids within the vessel so that they overflow at the vessel's overflow point. For the removal of nuclear waste product the vessel may be placed within a sealed container having a bottom connected transport line for transporting the solids to storage or other sites. The rate of solids flow is controlled by the flow rate of the fluidizing fluid and by V-notch weirs of different sizes spaced about the top of the vessel.

  3. Physics of forebody flow control

    NASA Technical Reports Server (NTRS)

    Font, Gabriel I.

    1993-01-01

    Performance in the high angle of attack regime is required by many different types of aircraft. Military aircraft, such as fighters, utilize flight in this regime to improve maneuverability. Civilian aircraft, such as supersonic or hypersonic transports, will also need to operate in this regime during take off and landing, due to their small highly swept wings. Flight at high angles of attack is problematic due to the vortices being created on the nose of the aircraft. The vortices tend to become asymmetric and produce side forces. At the same time, the rudders are less effective because they are becoming immersed in the flow separating from the wings and fuselage. Consequently, the side force produced by the vortices on the nose tend to destabilize the aircraft. This situation may be corrected through the use of a forebody flow control system such as tangential slot blowing. In this concept, a jet is blown from the nose in an effort to alter the flow field around the nose and diminish the destabilizing side force. Alternately, the jet may be used to create a side force which could be used to augment the rudders. This would allow the size of the rudders to be decreased which would, in turn, diminish the cruise drag. Therefore, the use of a tangential slot blowing system has the potential for improving both the maneuver performance and the cruise performance of an aircraft. The present study was conducted to explore the physics of forebody flow control. The study consisted of two major thrusts: (1) exploration of forebody flow control with tangential slot blowing; (2) investigation of flow and field response to a general perturbation.

  4. Ferroelectric Fluid Flow Control Valve

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

  5. CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999. Pt. 2

    NASA Technical Reports Server (NTRS)

    Whitlow, Jr., Woodrow (Editor); Todd, Emily N. (Editor)

    1999-01-01

    The proceedings of a workshop sponsored by the Confederation of European Aerospace Societies (CEAS), the American Institute of Aeronautics and Astronautics (AIAA), the National Aeronautics and Space Administration (NASA), Washington, D.C., and the Institute for Computer Applications in Science and Engineering (ICASE), Hampton, Virginia, and held in Williamsburg, Virginia June 22-25, 1999 represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft.

  6. Multiverse data-flow control.

    PubMed

    Schindler, Benjamin; Waser, Jürgen; Ribičić, Hrvoje; Fuchs, Raphael; Peikert, Ronald

    2013-06-01

    In this paper, we present a data-flow system which supports comparative analysis of time-dependent data and interactive simulation steering. The system creates data on-the-fly to allow for the exploration of different parameters and the investigation of multiple scenarios. Existing data-flow architectures provide no generic approach to handle modules that perform complex temporal processing such as particle tracing or statistical analysis over time. Moreover, there is no solution to create and manage module data, which is associated with alternative scenarios. Our solution is based on generic data-flow algorithms to automate this process, enabling elaborate data-flow procedures, such as simulation, temporal integration or data aggregation over many time steps in many worlds. To hide the complexity from the user, we extend the World Lines interaction techniques to control the novel data-flow architecture. The concept of multiple, special-purpose cursors is introduced to let users intuitively navigate through time and alternative scenarios. Users specify only what they want to see, the decision which data are required is handled automatically. The concepts are explained by taking the example of the simulation and analysis of material transport in levee-breach scenarios. To strengthen the general applicability, we demonstrate the investigation of vortices in an offline-simulated dam-break data set.

  7. Cruise control for segmented flow.

    PubMed

    Abolhasani, Milad; Singh, Mayank; Kumacheva, Eugenia; Günther, Axel

    2012-11-21

    Capitalizing on the benefits of microscale segmented flows, e.g., enhanced mixing and reduced sample dispersion, so far requires specialist training and accommodating a few experimental inconveniences. For instance, microscale gas-liquid flows in many current setups take at least 10 min to stabilize and iterative manual adjustments are needed to achieve or maintain desired mixing or residence times. Here, we report a cruise control strategy that overcomes these limitations and allows microscale gas-liquid (bubble) and liquid-liquid (droplet) flow conditions to be rapidly "adjusted" and maintained. Using this strategy we consistently establish bubble and droplet flows with dispersed phase (plug) velocities of 5-300 mm s(-1), plug lengths of 0.6-5 mm and continuous phase (slug) lengths of 0.5-3 mm. The mixing times (1-5 s), mass transfer times (33-250 ms) and residence times (3-300 s) can therefore be directly imposed by dynamically controlling the supply of the dispersed and the continuous liquids either from external pumps or from local pressurized reservoirs. In the latter case, no chip-external pumps, liquid-perfused tubes or valves are necessary while unwanted dead volumes are significantly reduced.

  8. Control of submersible vortex flows

    NASA Technical Reports Server (NTRS)

    Bushnell, D. M.; Donaldson, C. D.

    1990-01-01

    Vortex flows produced by submersibles typically unfavorably influence key figures of merit such as acoustic and nonacoustic stealth, control effectiveness/maneuverability, and propulsor efficiency/body drag. Sources of such organized, primarily longitudinal, vorticity include the basic body (nose and sides) and appendages (both base/intersection and tip regions) such as the fairwater, dive planes, rear control surfaces, and propulsor stators/tips. Two fundamentally different vortex control approaches are available: (1) deintensification of the amplitude and/or organization of the vortex during its initiation process; and (2) downstream vortex disablement. Vortex control techniques applicable to the initiation region (deintensification approach) include transverse pressure gradient minimization via altered body cross section, appendage dillets, fillets, and sweep, and various appendage tip and spanload treatment along with the use of active controls to minimize control surface size and motions. Vortex disablement can be accomplished either via use of control vortices (which can also be used to steer the vortices off-board), direct unwinding, inducement of vortex bursting, or segmentation/tailoring for enhanced dissipation. Submersible-applicable vortex control technology is also included derived from various aeronautical applications such as mitigation of the wing wake vortex hazard and flight aircraft maneuverability at high angle of attack as well as the status of vortex effects upon, and mitigation of, nonlinear control forces on submersibles. Specific suggestions for submersible-applicable vortex control techniques are presented.

  9. AIAA Educator Academy: The Space Weather Balloon Module

    NASA Astrophysics Data System (ADS)

    Longmier, B.; Henriquez, E.; Bering, E. A.; Slagle, E.

    2013-12-01

    Educator Academy is a K-12 STEM curriculum developed by the STEM K-12 Outreach Committee of the American Institute of Aeronautics and Astronautics (AIAA). Consisting of three independent curriculum modules, K-12 students participate in inquiry-based science and engineering challenges to improve critical thinking skills and enhance problem solving skills. The Space Weather Balloon Curriculum Module is designed for students in grades 9-12. Throughout this module, students learn and refine physics concepts as well as experimental research skills. Students participate in project-based learning that is experimental in nature. Students are engaged with the world around them as they collaborate to launch a high altitude balloon equipped with HD cameras.The program leaders launch high altitude weather balloons in collaboration with schools and students to teach physics concepts, experimental research skills, and to make space exploration accessible to students. A weather balloon lifts a specially designed payload package that is composed of HD cameras, GPS tracking devices, and other science equipment. The payload is constructed and attached to the balloon by the students with low-cost materials. The balloon and payload are launched with FAA clearance from a site chosen based on wind patterns and predicted landing locations. The balloon ascends over 2 hours to a maximum altitude of 100,000 feet where it bursts and allows the payload to slowly descend using a built-in parachute. The payload is located using the GPS device. In April 2012, the Space Weather Balloon team conducted a prototype field campaign near Fairbanks Alaska, sending several student-built experiments to an altitude of 30km, underneath several strong auroral displays. To better assist teachers in implementing one or more of these Curriculum Modules, teacher workshops are held to give teachers a hands-on look at how this curriculum is used in the classroom. And, to provide further support, teachers are each

  10. AIAA Educator Academy: Enriching STEM Education for K-12 Students

    NASA Astrophysics Data System (ADS)

    Slagle, E.; Bering, E. A.; Longmier, B. W.; Henriquez, E.; Milnes, T.; Wiedorn, P.; Bacon, L.

    2012-12-01

    Educator Academy is a K-12 STEM curriculum developed by the STEM K-12 Outreach Committee of the American Institute of Aeronautics and Astronautics (AIAA). Consisting of three independent curriculum modules, K-12 students participate in inquiry-based engineering challenges to improve critical thinking skills and enhance problem solving skills. The Mars Rover Celebration Curriculum Module is designed for students in grades 3-8. Throughout this module, students learn about Mars and the solar system. Working with given design criteria, students work in teams to do basic research about Mars that will determine the operational objectives and structural features of their rover. Then, students participate in the design and construction of a model of a mock-up Mars Rover to carry out a specific science mission on the surface of Mars. At the end of this project, students have the opportunity to participate in a regional capstone event where students share their rover designs and what they have learned. The Electric Cargo Plan Curriculum Module is designed for students in grades 6-12. Throughout this module, students learn about aerodynamics and the four forces of flight. Working individually or in teams, students design and construct an electrically-powered model aircraft to fly a tethered flight of at least one lap without cargo, followed by a second tethered flight of one lap carrying as much cargo as possible. At the end of this project, students have the opportunity to participate in a regional capstone event where students share what they have learned and compete with their different cargo plane designs. The Space Weather Balloon Curriculum Module is designed for students in grades 9-12. Throughout this module, students learn and refine physics concepts as well as experimental research skills. Students participate in project-based learning that is experimental in nature. Students are engaged with the world around them as they collaborate to launch a high altitude

  11. Model-Based Feedback Control of Cavity Resonance: An Experimental and Computational Approach

    DTIC Science & Technology

    2006-07-24

    cavity flow control as well as for other closed-loop flow control applications. Theo - retical models are presented for temporally developing shear layers...smoothening. J. Sound Vib., 253(4):807-831, 2002. [52] L. S. Ukeiley, M. K. Ponton, J. S. Seiner, and B. Jansen . Suppression of pressure loads in cavity flows...AIAA Paper 2002-0661, 2002. [53] L. S. Ukeiley, M. K. Ponton, J. S. Seiner, and B. Jansen . Suppression of pressure loads in resonating cavities

  12. External and Turbomachinery Flow Control Working Group

    NASA Technical Reports Server (NTRS)

    Ahmadi, G.; Alstrom, B.; Colonius, T.; Dannenhoffer, J.; Glauser, M.; Helenbrook, B.; Higuchi, H.; Hodson, H.; Jha, R.; Kabiri, P.; LaGraff, J.; Low,K.; McKeon, B.; Morrison, J.; Obcid, S.; Orbaker, A.; Samimy, M.; Schmit, R.; Seifert, A.; Seume, J.; Shahabi, A.; Shea, P.; Ukeiley, L.; Wallace, R.

    2010-01-01

    Broad Flow Control Issues: a) Understanding flow physics. b) Specific control objective(s). c) Actuation. d) Sensors. e) Integrated active flow control system. f) Development of design tools (CFD, reduced order models, controller design, understanding and utilizing instabilities and other mechanisms, e.g., streamwise vorticity).

  13. Bio-mimetic Flow Control

    NASA Astrophysics Data System (ADS)

    Choi, Haecheon

    2009-11-01

    Bio-mimetic engineering or bio-mimetics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology (from Wikipedia). The concept itself is old, but successful developments have been made recently, especially in the research field of flow control. The objective of flow control based on the bio-mimetic approach is to develop novel concepts for reducing drag, increasing lift and enhancing aerodynamic performance. For skin friction reduction, a few ideas have been suggested such as the riblet from shark, compliant surface from dolphin, microbubble injection and multiple front-body curvature from penguin, and V-shaped protrusion from sailfish. For form drag reduction, several new attempts have been also made recently. Examples include the V-shaped spanwise grooves from saguaro cactus, overall shape of box fish, longitudinal grooves on scallop shell, bill of swordfish, hooked comb on owl wing, trailing-edge protrusion on dragonfly wing, and fillet. For the enhancement of aerodynamic performance, focuses have been made on the birds, fish and insects: e.g., double layered feather of landing bird, leading-edge serration of humpback-whale flipper, pectoral fin of flying fish, long tail on swallowtail-butterfly wing, wing flapping motion of dragonfly, and alula in birds. Living animals adapt their bodies to better performance in multi purposes, but engineering requires single purpose in most cases. Therefore, bio-mimetic approaches often produce excellent results more than expected. However, they are sometimes based on people's wrong understanding of nature and produce unwanted results. Successes and failures from bio-mimetic approaches in flow control will be discussed in the presentation.

  14. Flow Control Using Neural Networks

    DTIC Science & Technology

    2007-11-02

    FEB 93 - 31 DEC 96 4. TITLE AND SUBTITLE 5 . FUNDING NUMBERS FLOW CONTROL USING NEURAL NETWORKS F49620-93-1-0135 61102F 6. AUTHOR(S) 2307/BS THORWALD...OFFICE OF SCIENTIFIC RESEARCH (AFOSRO AGENCY REPORT NUMBER 110 DUNCAN AVENUE, ROOM B115 BOLLING AFB DC 20332- 8050 11. SUPPLEMENTARY NOTES 12a...signals. Figure 5 shows a time series for an actuator that performs a ramp motion in the streamwise direction over about 1 % of the TS period and remains

  15. Mechanobiological oscillators control lymph flow

    PubMed Central

    Kunert, Christian; Baish, James W.; Liao, Shan; Padera, Timothy P.; Munn, Lance L.

    2015-01-01

    The ability of cells to sense and respond to physical forces has been recognized for decades, but researchers are only beginning to appreciate the fundamental importance of mechanical signals in biology. At the larger scale, there has been increased interest in the collective organization of cells and their ability to produce complex, “emergent” behaviors. Often, these complex behaviors result in tissue-level control mechanisms that manifest as biological oscillators, such as observed in fireflies, heartbeats, and circadian rhythms. In many cases, these complex, collective behaviors are controlled—at least in part—by physical forces imposed on the tissue or created by the cells. Here, we use mathematical simulations to show that two complementary mechanobiological oscillators are sufficient to control fluid transport in the lymphatic system: Ca2+-mediated contractions can be triggered by vessel stretch, whereas nitric oxide produced in response to the resulting fluid shear stress causes the lymphatic vessel to relax locally. Our model predicts that the Ca2+ and NO levels alternate spatiotemporally, establishing complementary feedback loops, and that the resulting phasic contractions drive lymph flow. We show that this mechanism is self-regulating and robust over a range of fluid pressure environments, allowing the lymphatic vessels to provide pumping when needed but remain open when flow can be driven by tissue pressure or gravity. Our simulations accurately reproduce the responses to pressure challenges and signaling pathway manipulations observed experimentally, providing an integrated conceptual framework for lymphatic function. PMID:26283382

  16. Observations on CFD Verification and Validation from the AIAA Drag Prediction Workshops

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.; Kleb, Bil; Vassberg, John C.

    2014-01-01

    The authors provide observations from the AIAA Drag Prediction Workshops that have spanned over a decade and from a recent validation experiment at NASA Langley. These workshops provide an assessment of the predictive capability of forces and moments, focused on drag, for transonic transports. It is very difficult to manage the consistency of results in a workshop setting to perform verification and validation at the scientific level, but it may be sufficient to assess it at the level of practice. Observations thus far: 1) due to simplifications in the workshop test cases, wind tunnel data are not necessarily the “correct” results that CFD should match, 2) an average of core CFD data are not necessarily a better estimate of the true solution as it is merely an average of other solutions and has many coupled sources of variation, 3) outlier solutions should be investigated and understood, and 4) the DPW series does not have the systematic build up and definition on both the computational and experimental side that is required for detailed verification and validation. Several observations regarding the importance of the grid, effects of physical modeling, benefits of open forums, and guidance for validation experiments are discussed. The increased variation in results when predicting regions of flow separation and increased variation due to interaction effects, e.g., fuselage and horizontal tail, point out the need for validation data sets for these important flow phenomena. Experiences with a recent validation experiment at NASA Langley are included to provide guidance on validation experiments.

  17. Comparison of NTF Experimental Data with CFD Predictions from the Third AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Vassberg, John C.; Tinoco, Edward N.; Mani, Mori; Levy, David; Zickuhr, Tom; Mavriplis, Dimitri J.; Wahls, Richard A.; Morrison, Joseph H.; Brodersen, Olaf P.; Eisfeld, Bernhard; Murayama, Mitsuhiro

    2008-01-01

    Recently acquired experimental data for the DLR-F6 wing-body transonic transport con figuration from the National Transonic Facility (NTF) are compared with the database of computational fluid dynamics (CFD) predictions generated for the Third AIAA CFD Drag Prediction Workshop (DPW-III). The NTF data were collected after the DPW-III, which was conducted with blind test cases. These data include both absolute drag levels and increments associated with this wing-body geometry. The baseline DLR-F6 wing-body geometry is also augmented with a side-of-body fairing which eliminates the flow separation in this juncture region. A comparison between computed and experimentally observed sizes of the side-of-body flow-separation bubble is included. The CFD results for the drag polars and separation bubble sizes are computed on grids which represent current engineering best practices for drag predictions. In addition to these data, a more rigorous attempt to predict absolute drag at the design point is provided. Here, a series of three grid densities are utilized to establish an asymptotic trend of computed drag with respect to grid convergence. This trend is then extrapolated to estimate a grid-converged absolute drag level.

  18. Improved Flow-Controlling Vortex Generator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.; Marner, Wilbur J.; Rohatgi, Naresh K.

    1989-01-01

    Symmetrical tangential streams control flow of radial primary streams. Vortex generator uses small secondary stream of fluid to control normally-larger primary stream. Improved version of vortex generator described in "Variable Control Port for Fluidic Control Device," (NPO-16603). Secondary, or control, flows entering tangentially through diametrically opposite ports set up swirling motion restraining primary flow. Pressure of secondary fluid in relation to primary fluid controlling factor. Like valve, vortex generator varies rate of flow of primary fluid from maximum value down to zero. When properly designed, requires low pressure differential between primary and secondary streams and expends relatively small amount of secondary fluid.

  19. Summary of the Fourth AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Vassberg, John C.; Tinoco, Edward N.; Mani, Mori; Rider, Ben; Zickuhr, Tom; Levy, David W.; Brodersen, Olaf P.; Eisfeld, Bernhard; Crippa, Simone; Wahls, Richard A.; hide

    2010-01-01

    Results from the Fourth AIAA Drag Prediction Workshop (DPW-IV) are summarized. The workshop focused on the prediction of both absolute and differential drag levels for wing-body and wing-body-horizontal-tail configurations that are representative of transonic transport air- craft. Numerical calculations are performed using industry-relevant test cases that include lift- specific flight conditions, trimmed drag polars, downwash variations, dragrises and Reynolds- number effects. Drag, lift and pitching moment predictions from numerous Reynolds-Averaged Navier-Stokes computational fluid dynamics methods are presented. Solutions are performed on structured, unstructured and hybrid grid systems. The structured-grid sets include point- matched multi-block meshes and over-set grid systems. The unstructured and hybrid grid sets are comprised of tetrahedral, pyramid, prismatic, and hexahedral elements. Effort is made to provide a high-quality and parametrically consistent family of grids for each grid type about each configuration under study. The wing-body-horizontal families are comprised of a coarse, medium and fine grid; an optional extra-fine grid augments several of the grid families. These mesh sequences are utilized to determine asymptotic grid-convergence characteristics of the solution sets, and to estimate grid-converged absolute drag levels of the wing-body-horizontal configuration using Richardson extrapolation.

  20. Status of the AIAA Modeling and Simulation Format Standard

    NASA Technical Reports Server (NTRS)

    Jackson, E. Bruce; Hildreth, Bruce L.

    2008-01-01

    The current draft AIAA Standard for flight simulation models represents an on-going effort to improve the productivity of practitioners of the art of digital flight simulation (one of the original digital computer applications). This initial release provides the capability for the efficient representation and exchange of an aerodynamic model in full fidelity; the DAVE-ML format can be easily imported (with development of site-specific import tools) in an unambiguous way with automatic verification. An attractive feature of the standard is the ability to coexist with existing legacy software or tools. The draft Standard is currently limited in scope to static elements of dynamic flight simulations; however, these static elements represent the bulk of typical flight simulation mathematical models. It is already seeing application within U.S. and Australian government agencies in an effort to improve productivity and reduce model rehosting overhead. An existing tool allows import of DAVE-ML models into a popular simulation modeling and analysis tool, and other community-contributed tools and libraries can simplify the use of DAVE-ML compliant models at compile- or run-time of high-fidelity flight simulation.

  1. Power flow control using quadrature boosters

    NASA Astrophysics Data System (ADS)

    Sadanandan, Sandeep N.

    A power system that can be controlled within security constraints would be an advantage to power planners and real-time operators. Controlling flows can lessen reliability issues such as thermal limit violations, power stability problems, and/or voltage stability conditions. Control of flows can also mitigate market issues by reducing congestion on some lines and rerouting power to less loaded lines or onto preferable paths. In the traditional control of power flows, phase shifters are often used. More advanced methods include using Flexible AC Transmission System (FACTS) Controllers. Some examples include Thyristor Controlled Series Capacitors, Synchronous Series Static Compensators, and Unified Power Flow Controllers. Quadrature Boosters (QBs) have similar structures to phase-shifters, but allow for higher voltage magnitude during real power flow control. In comparison with other FACTS controllers QBs are not as complex and not as expensive. The present study proposes to use QBs to control power flows on a power system. With the inclusion of QBs, real power flows can be controlled to desired scheduled values. In this thesis, the linearized power flow equations used for power flow analysis were modified for the control problem. This included modifying the Jacobian matrix, the power error vector, and calculating the voltage injected by the quadrature booster for the scheduled real power flow. Two scenarios were examined using the proposed power flow control method. First, the power flow in a line in a 5-bus system was modified with a QB using the method developed in this thesis. Simulation was carried out using Matlab. Second, the method was applied to a 30-bus system and then to a 118-bus system using several QBs. In all the cases, the calculated values of the QB voltages led to desired power flows in the designated line.

  2. Valve for controlling solids flow

    DOEpatents

    Feldman, David K.

    1980-01-01

    A fluidized solids control valve is disclosed that is particularly well adapted for use with a flow of coal or char that includes both large particles and fines. The particles may or may not be fluidized at various times during the operation. The valve includes a tubular body that terminates in a valve seat covered by a normally closed closure plate. The valve body at the seat and the closure plate is provided with aligned longitudinal slots that receive a pivotally supported key plate. The key plate is positionable by an operator in inserted, intermediate and retracted positions respecting the longitudinal slot in the valve body. The key plate normally closes the slot within the closure plate but is shaped and aligned obliquely to the longitudinal slot within the valve body to provide progressively increasing slot openings between the inserted and retracted positions. Transfer members are provided between the operator, key plate and closure plate to move the closure plate into an open position only when the key plate is retracted from the longitudinal slot within the valve body.

  3. Development report, mass flow controller PN 5716068

    NASA Technical Reports Server (NTRS)

    Taylor, W.

    1972-01-01

    The design, development, and manufacture of an all mechanical mass flow controller are discussed. A test program was conducted using inert gas as the test medium. The unit controlled the pressure within plus of minus one percent. An analytical method is presented for relating the control pressure error with error in mass flow.

  4. Cart3D Simulations for the First AIAA Sonic Boom Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Aftosmis, Michael J.; Nemec, Marian

    2014-01-01

    Simulation results for the First AIAA Sonic Boom Prediction Workshop (LBW1) are presented using an inviscid, embedded-boundary Cartesian mesh method. The method employs adjoint-based error estimation and adaptive meshing to automatically determine resolution requirements of the computational domain. Results are presented for both mandatory and optional test cases. These include an axisymmetric body of revolution, a 69deg delta wing model and a complete model of the Lockheed N+2 supersonic tri-jet with V-tail and flow through nacelles. In addition to formal mesh refinement studies and examination of the adjoint-based error estimates, mesh convergence is assessed by presenting simulation results for meshes at several resolutions which are comparable in size to the unstructured grids distributed by the workshop organizers. Data provided includes both the pressure signals required by the workshop and information on code performance in both memory and processing time. Various enhanced techniques offering improved simulation efficiency will be demonstrated and discussed.

  5. Wind-US Code Contributions to the First AIAA Shock Boundary Layer Interaction Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Georgiadis, Nicholas J.; Vyas, Manan A.; Yoder, Dennis A.

    2013-01-01

    This report discusses the computations of a set of shock wave/turbulent boundary layer interaction (SWTBLI) test cases using the Wind-US code, as part of the 2010 American Institute of Aeronautics and Astronautics (AIAA) shock/boundary layer interaction workshop. The experiments involve supersonic flows in wind tunnels with a shock generator that directs an oblique shock wave toward the boundary layer along one of the walls of the wind tunnel. The Wind-US calculations utilized structured grid computations performed in Reynolds-averaged Navier-Stokes mode. Four turbulence models were investigated: the Spalart-Allmaras one-equation model, the Menter Baseline and Shear Stress Transport k-omega two-equation models, and an explicit algebraic stress k-omega formulation. Effects of grid resolution and upwinding scheme were also considered. The results from the CFD calculations are compared to particle image velocimetry (PIV) data from the experiments. As expected, turbulence model effects dominated the accuracy of the solutions with upwinding scheme selection indicating minimal effects.

  6. Local Control of Blood Flow

    ERIC Educational Resources Information Center

    Clifford, Philip S.

    2011-01-01

    Organ blood flow is determined by perfusion pressure and vasomotor tone in the resistance vessels of the organ. Local factors that regulate vasomotor tone include myogenic and metabolic autoregulation, flow-mediated and conducted responses, and vasoactive substances released from red blood cells. The relative importance of each of these factors…

  7. Local Control of Blood Flow

    ERIC Educational Resources Information Center

    Clifford, Philip S.

    2011-01-01

    Organ blood flow is determined by perfusion pressure and vasomotor tone in the resistance vessels of the organ. Local factors that regulate vasomotor tone include myogenic and metabolic autoregulation, flow-mediated and conducted responses, and vasoactive substances released from red blood cells. The relative importance of each of these factors…

  8. CFD Modeling for Active Flow Control

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.

    2001-01-01

    This presentation describes current work under UEET Active Flow Control CFD Research Tool Development. The goal of this work is to develop computational tools for inlet active flow control design. This year s objectives were to perform CFD simulations of fully gridded vane vortex generators, micro-vortex genera- tors, and synthetic jets, and to compare flowfield results with wind tunnel tests of simple geometries with flow control devices. Comparisons are shown for a single micro-vortex generator on a flat plate, and for flow over an expansion ramp with sidewall effects. Vortex core location, pressure gradient and oil flow patterns are compared between experiment and computation. This work lays the groundwork for evaluating simplified modeling of arrays of devices, and provides the opportunity to test simple flow control device/sensor/ control loop interaction.

  9. Successes and Challenges for Flow Control Simulations

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2008-01-01

    A survey is made of recent computations published for synthetic jet flow control cases from a CFD workshop held in 2004. The three workshop cases were originally chosen to represent different aspects of flow control physics: nominally 2-D synthetic jet into quiescent air, 3-D circular synthetic jet into turbulent boundarylayer crossflow, and nominally 2-D flow-control (both steady suction and oscillatory zero-net-mass-flow) for separation control on a simple wall-mounted aerodynamic hump shape. The purpose of this survey is to summarize the progress as related to these workshop cases, particularly noting successes and remaining challenges for computational methods. It is hoped that this summary will also by extension serve as an overview of the state-of-the-art of CFD for these types of flow-controlled flow fields in general.

  10. Successes and Challenges for Flow Control Simulations

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2008-01-01

    A survey is made of recent computations published for synthetic jet flow control cases from a CFD workshop held in 2004. The three workshop cases were originally chosen to represent different aspects of flow control physics: nominally 2-D synthetic jet into quiescent air, 3-D circular synthetic jet into turbulent boundary-layer crossflow, and nominally 2-D flow-control (both steady suction and oscillatory zero-net-mass-flow) for separation control on a simple wall-mounted aerodynamic hump shape. The purpose of this survey is to summarize the progress as related to these workshop cases, particularly noting successes and remaining challenges for computational methods. It is hoped that this summary will also by extension serve as an overview of the state-of-the-art of CFD for these types of flow-controlled flow fields in general.

  11. On the Flow Physics of Effectively Controlled Open Cavity Flows

    DTIC Science & Technology

    2013-05-01

    effective in supersonic free stream conditions. To achieve this goal several advancements in our understanding of active control methodologies, as well as...achieve the goal of using adaptive control at supersonic free stream Mach numbers, one needs to better understand the flow physics of the actuator flow...following section we will detail applications of this to open cavities with both supersonic and subsonic free stream conditions. 2.1 Supersonic

  12. Supersonic Flow Control by Magnetic Field

    DTIC Science & Technology

    2005-12-01

    control over supersonic flows in supersonic intakes . Experimental and numerical investigations focuses on the basic aspects of MHD interaction taking into...transport, shock-waves dynamics, boundary layers on the intake walls, massive flow separation within the scram-jet flow pass. Recent results of...that a global change of intake flow structure might be achieved with local ( in time and space ) MHD impact. Other aspect is supposed to be

  13. Status and outlook of flow separation control

    NASA Technical Reports Server (NTRS)

    Gad-El-hak, Mohamed; Bushnell, Dennis M.

    1991-01-01

    Under certain conditions, wall-bounded flows separate. To improve the performance of natural or man-made flow systems, it may be beneficial to delay or advance this detachment process. The present article reviews the status and outlook of separation control for both steady and unsteady flows. Both passive and active techniques to prevent or to provoke flow detachment are considered and suggestions are made for further research.

  14. Active Control of Jet Engine Inlet Flows

    DTIC Science & Technology

    2007-03-31

    Department at Texas A&M University. The other CFD package employed was Gambit and Fluent , a commercial grid generation and flow solution code currently...Locations F 4t Figure 48: Streamlines Produced by the UNS3D) Flow Solver Showing Second Bend Vortex Formation 49 Gambit and Fluent Grid Generation The use of... Fluent and an in-house code in order to predict the flow characteristics as well as estimate the effects of flow control. Experiments run using the

  15. Application of Fast Optical Tomography to Flow Tubes

    DTIC Science & Technology

    2007-11-02

    electro-optics, quantum electronics, solid-state lasers , optical propagation and communications; microwave semiconductor devices, microwave /millimeter...34Application of Tomography in 3-D Transonic Flows, AIAA-87-1374, AIAA 19th Fluid Dynamics, Plasma Dynamics and Laser Conference, Honolulu, Hawaii...thermomechanics, gas kinetics and radiation; cw and pulsed chemical and excimer laser development including chemical kinetics, spectroscopy, optical

  16. Approximate Controllability Results for Linear Viscoelastic Flows

    NASA Astrophysics Data System (ADS)

    Chowdhury, Shirshendu; Mitra, Debanjana; Ramaswamy, Mythily; Renardy, Michael

    2017-09-01

    We consider linear viscoelastic flow of a multimode Maxwell or Jeffreys fluid in a bounded domain with smooth boundary, with a distributed control in the momentum equation. We establish results on approximate and exact controllability.

  17. Energy conservation with automatic flow control valves

    SciTech Connect

    Phillips, D.

    1984-12-01

    Automatic flow control valves are offered in a wide range of sizes starting at 1/2 in. with flow rates of 0.5 gpm and up. They are also provided with materials and end connections to meet virtually any fan-coil system requirement. Among these are copper sweat type valves; ductile iron threaded valves; male/female threaded brass valves; and combination flow control/ball valves with union ends.

  18. Hydrodynamic Flow Control in Marine Mammals

    DTIC Science & Technology

    2008-05-06

    Hydrodynamic flow control in marine mammals Frank E. Fish,1,* Laurens E. Howle† and Mark M. Murray§ Department of Biology, West Chester University...the flow of water around the body dictates the performance of marine mammals in the aquatic environment. Morphological specializations of marine mammals ...and maneuverability. The morphological features of marine mammals for flow control can be utilized in the biomimetic design of engineered structures

  19. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2006-01-01

    This paper gives an overview of a research study conducted in support of the small-scale demonstration of an active flow control system for a boundary-layer-ingesting (BLI) inlet. The effectiveness of active flow control in reducing engine inlet circumferential distortion was assessed using a 2.5% scale model of a 35% boundary-layer-ingesting flush-mounted, offset, diffusing inlet. This experiment was conducted in the NASA Langley 0.3-meter Transonic Cryogenic Tunnel at flight Mach numbers with a model inlet specifically designed for this type of testing. High mass flow actuators controlled the flow through distributed control jets providing the active flow control. A vortex generator point design configuration was also tested for comparison purposes and to provide a means to examine a hybrid vortex generator and control jets configuration. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion and pressure recovery were determined by 40 total pressure measurements on 8 rake arms each separated by 45 degrees and were located at the aerodynamic interface plane. The test matrix was limited to a maximum free-stream Mach number of 0.85 with scaled mass flows through the inlet for that condition. The data show that the flow control jets alone can reduce circumferential distortion (DPCP(sub avg)) from 0.055 to about 0.015 using about 2.5% of inlet mass flow. The vortex generators also reduced the circumferential distortion from 0.055 to 0.010 near the inlet mass flow design point. Lower inlet mass flow settings with the vortex generator configuration produced higher distortion levels that were reduced to acceptable levels using a hybrid vortex generator/control jets configuration that required less than 1% of the inlet mass flow.

  20. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2006-01-01

    This paper gives an overview of a research study conducted in support of the small-scale demonstration of an active flow control system for a boundary-layer-ingesting (BLI) inlet. The effectiveness of active flow control in reducing engine inlet circumferential distortion was assessed using a 2.5% scale model of a 35% boundary-layer-ingesting flush-mounted, offset, diffusing inlet. This experiment was conducted in the NASA Langley 0.3-meter Transonic Cryogenic Tunnel at flight Mach numbers with a model inlet specifically designed for this type of testing. High mass flow actuators controlled the flow through distributed control jets providing the active flow control. A vortex generator point design configuration was also tested for comparison purposes and to provide a means to examine a hybrid vortex generator and control jets configuration. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion and pressure recovery were determined by 40 total pressure measurements on 8 rake arms each separated by 45 degrees and were located at the aerodynamic interface plane. The test matrix was limited to a maximum free-stream Mach number of 0.85 with scaled mass flows through the inlet for that condition. The data show that the flow control jets alone can reduce circumferential distortion (DPCPavg) from 0.055 to about 0.015 using about 2.5% of inlet mass flow. The vortex generators also reduced the circumferential distortion from 0.055 to 0.010 near the inlet mass flow design point. Lower inlet mass flow settings with the vortex generator configuration produced higher distortion levels that were reduced to acceptable levels using a hybrid vortex generator/control jets configuration that required less than 1% of the inlet mass flow.

  1. Electrokinetic Flow Control and Propulsion for MAVs

    DTIC Science & Technology

    2007-11-02

    Vehicle (pdf) Electroaerodynamic Coanda Effect – Cylinder Wake Flow Control Experiments to Active Cylinder Wake Flow Control Using Electric Field Actuators...flow separation at the leading edge - Compact geometry (low aspect-ratio below 2) gives rise to strong 3D effects Nonlinear lift characteristics and...Additional Electrode Pair at Trailing Edge has Effect of Jet Flap. - Lift Enhancement at alpha = 19° is 127% - Drag Coefficient decreases by 18% Increase of

  2. Flow Control Over Sharp-Edged Wings

    DTIC Science & Technology

    2007-07-01

    each jet. A constant average mass flow of air was supplied to the jet using a closed-loop servo valve . Their data indicated that maximum lift...and screw angles of 90 and 45 degrees respectively. High-speed flow control valves were used to control the pulsed flow to each jet individually. The...leading edge contained three jet nozzles; however only two were used. The valve open-and-close cycle was manipulated using a computer function

  3. Serpentine Geometry Plasma Actuators for Flow Control

    DTIC Science & Technology

    2013-08-23

    Serpentine geometry plasma actuators for flow control Mark Riherd and Subrata Roy Citation: J. Appl. Phys. 114, 083303 (2013); doi: 10.1063...DATES COVERED 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Serpentine geometry plasma actuators for flow control 5a. CONTRACT NUMBER 5b...unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Serpentine geometry plasma actuators for flow

  4. Flow Control in a Compact Inlet

    NASA Astrophysics Data System (ADS)

    Vaccaro, John C.

    2011-12-01

    An experimental investigation of flow control, via various control jets actuators, was undertaken to eliminate separation and secondary flows in a compact inlet. The compact inlet studied was highly aggressive with a length-to-diameter ratio of 1.5. A brand new facility was designed and built to enable various actuation methodologies as well as multiple measurement techniques. Techniques included static surface pressure, total pressure, and stereoscopic particle image velocimetry. Experimental data were supplemented with numerical simulations courtesy of Prof. Kenneth Jansen, Dr. Onkar Sahni, and Yi Chen. The baseline flow field was found to be dominated by two massive separations and secondary flow structures. These secondary structures were present at the aerodynamic interface plane in the form of two counter-rotating vortices inducing upwash along centerline. A dominant shedding frequency of 350 Hz was measured both at the aerodynamic interface plane and along the lower surface of the inlet. Flow control experiments started utilizing a pair of control jets placed in streamwise locations where flow was found to separate. Tests were performed for a range of inlet Mach numbers from 0.2 to 0.44. Steady and unsteady static pressure measurements along the upper and lower walls of the duct were performed for various combinations of actuation. The parameters that were tested include the control jets momentum coefficient, their blowing ratio, the actuation frequency, as well as different combinations of jets. It was shown that using mass flux ratio as a criterion to define flow control is not sufficient, and one needs to provide both the momentum coefficient and the blowing ratio to quantify the flow control performance. A detailed study was undertaken on controlling the upstream separation point for an inlet Mach number of 0.44. Similar to the baseline flow field, the flow field associated with the activation of a two-dimensional control jet actuator was dominated by

  5. Subsonic Flows through S-Ducts with Flow Control

    NASA Astrophysics Data System (ADS)

    Chen, Yi

    An inlet duct of an aircraft connects the air intake mounted on the fuselage to the engine within the aircraft body. The ideal outflow quality of the duct is steady, uniform and of high total pressure. Recently compact S-shaped inlet ducts are drawing more attention in the design of UAVs with short propulsion system. Compact ducts usually involve strong streamwise adverse pressure gradient and transverse secondary flow, leading to large-scale harmful vortical structures in the outflow. To improve the outflow quality modern flow control techniques have to be applied. Before designing successful flow control methods a solid understanding of the baseline flow field with the duct is crucial. In this work the fundamental mechanism of how the three dimensional flow topology evolves when the relevant parameters such as the duct geometry and boundary layer thickness are varied, is studied carefully. Two distinct secondary-flow patterns are identified. For the first time the sensitivity of the flow topology to the inflow boundary layer thickness in long ducts is clearly addressed. The interaction between the transverse motion induced by the transverse pressure gradient and the streamwise separation is revealed as the crucial reason for the various flow patterns existing in short ducts. A non-symmetric flow pattern is identified for the first time in both experiments and simulations in short ducts in which the intensity of the streamwise separation and the transverse invasion are in the same order of magnitude. A theory of energy accumulation and solution bifurcation is used to give a reasonable explanation for this non-symmetry. After gaining the knowledge of where and how the harmful vortical structures are generated several flow control techniques are tested to achieve a better outflow quality. The analysis of the flow control cases also provides a deeper insight into the behavior of the three-dimensional flow within the ducts. The conventional separation control method

  6. Cylinder Flow Control Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Kozlov, Alexey; Thomas, Flint

    2007-11-01

    In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. Two optimized quartz dielectric plasma actuators mounted on the cylinder surface utilizing an improved saw-tooth waveform high-voltage generator allowed flow control at Reynolds number approaching supercritical. Using either steady or unsteady actuation, it is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. PIV based flow fields and wake velocity profiles obtained with hot-wire anemometry show large reductions in vortex shedding, wake width and turbulence intensity.

  7. Integrated soft sensor model for flow control.

    PubMed

    Aijälä, G; Lumley, D

    2006-01-01

    Tighter discharge permits often require wastewater treatment plants to maximize utilization of available facilities in order to cost-effectively reach these goals. Important aspects are minimizing internal disturbances and using available information in a smart way to improve plant performance. In this study, flow control throughout a large highly automated wastewater treatment plant (WWTP) was implemented in order to reduce internal disturbances and to provide a firm foundation for more advanced process control. A modular flow control system was constructed based on existing instrumentation and soft sensor flow models. Modules were constructed for every unit process in water treatment and integrated into a plant-wide model. The flow control system is used to automatically control recirculation flows and bypass flows at the plant. The system was also successful in making accurate flow estimations at points in the plant where it is not possible to have conventional flow meter instrumentation. The system provides fault detection for physical flow measuring devices. The module construction allows easy adaptation for new unit processes added to the treatment plant.

  8. Power flow control using distributed saturable reactors

    DOEpatents

    Dimitrovski, Aleksandar D.

    2016-02-13

    A magnetic amplifier includes a saturable core having a plurality of legs. Control windings wound around separate legs are spaced apart from each other and connected in series in an anti-symmetric relation. The control windings are configured in such a way that a biasing magnetic flux arising from a control current flowing through one of the plurality of control windings is substantially equal to the biasing magnetic flux flowing into a second of the plurality of control windings. The flow of the control current through each of the plurality of control windings changes the reactance of the saturable core reactor by driving those portions of the saturable core that convey the biasing magnetic flux in the saturable core into saturation. The phasing of the control winding limits a voltage induced in the plurality of control windings caused by a magnetic flux passing around a portion of the saturable core.

  9. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2008-01-01

    An experimental study was conducted to provide the first demonstration of an active flow control system for a flush-mounted inlet with significant boundary-layer-ingestion in transonic flow conditions. The effectiveness of the flow control in reducing the circumferential distortion at the engine fan-face location was assessed using a 2.5%-scale model of a boundary-layer-ingesting offset diffusing inlet. The inlet was flush mounted to the tunnel wall and ingested a large boundary layer with a boundary-layer-to-inlet height ratio of 35%. Different jet distribution patterns and jet mass flow rates were used in the inlet to control distortion. A vane configuration was also tested. Finally a hybrid vane/jet configuration was tested leveraging strengths of both types of devices. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow rates through the duct and the flow control actuators. The distortion and pressure recovery were measured at the aerodynamic interface plane. The data show that control jets and vanes reduce circumferential distortion to acceptable levels. The point-design vane configuration produced higher distortion levels at off-design settings. The hybrid vane/jet flow control configuration reduced the off-design distortion levels to acceptable ones and used less than 0.5% of the inlet mass flow to supply the jets.

  10. Transitioning Active Flow Control to Applications

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.; Horta, Lucas G.; Chen, Fang-Jenq

    1999-01-01

    Active Flow Control Programs at NASA, the U.S. Air Force, and DARPA have been initiated with the goals of obtaining revolutionary advances in aerodynamic performance and maneuvering compared to conventional approaches. These programs envision the use of actuators, sensors, and controllers on applications such as aircraft wings/tails, engine nacelles, internal ducts, nozzles, projectiles, weapons bays, and hydrodynamic vehicles. Anticipated benefits of flow control include reduced weight, part count, and operating cost and reduced fuel burn (and emissions), noise and enhanced safety if the sensors serve a dual role of flow control and health monitoring. To get from the bench-top or laboratory test to adaptive distributed control systems on realistic applications, reliable validated design tools are needed in addition to sub- and large-scale wind-tunnel and flight experiments. This paper will focus on the development of tools for active flow control applications.

  11. Investigation of propellant flow control system

    NASA Technical Reports Server (NTRS)

    Liebman, A. A.

    1973-01-01

    Mechanical, electromechanical, and fluidic concepts were studied as propellant flow control system for oxygen/hydrogen attitude control thrusters. A mechanical flow controller was designed, fabricated, and tested with hydrogen, oxygen, and nitrogen over a range of inlet pressures and temperatures. Results of these tests are presented along with a discussion of a flight-weight design. Also presented are recommendations for further design and development. A detailed coverage of the fluidics investigation is included.

  12. Flow Control in a Transonic Diffuser

    NASA Astrophysics Data System (ADS)

    Gartner, Jeremy; Amitay, Michael

    2014-11-01

    In some airplanes such as fighter jets and UAV, short inlet ducts replace the more conventional ducts due to their shorter length. However, these ducts are associated with low length-to-diameter ratio and low aspect ratio and, thus, experience massive separation and the presence of secondary flow structures. These flow phenomena are undesirable as they lead to pressure losses and distortion at the Aerodynamic Interface Plane (AIP), where the engine face is located. It causes the engine to perform with a lower efficiency as it would with a straight duct diffuser. Different flow control techniques were studied on the short inlet duct, with the goal to reattach the flow and minimize the distortions at the AIP. Due to the complex interaction between the separation and the secondary flow structures, the necessity to understand the flow mechanisms, and how to control them at a more fundamental level, a new transonic diffuser with an upper ramp and a straight floor was designed and built. The objective of this project is to explore the effectiveness of different flow control techniques in a high subsonic (up to Mach 0.8) diffuser, so that the quasi two-dimensional separation and the formation of secondary flow structure can be isolated using a canonical flow field. Supported by Northrop Grumman.

  13. Controlling Gas-Flow Mass Ratios

    NASA Technical Reports Server (NTRS)

    Morris, Brian G.

    1990-01-01

    Proposed system automatically controls proportions of gases flowing in supply lines. Conceived for control of oxidizer-to-fuel ratio in new gaseous-propellant rocket engines. Gas-flow control system measures temperatures and pressures at various points. From data, calculates control voltages for electronic pressure regulators for oxygen and hydrogen. System includes commercially available components. Applicable to control of mass ratios in such gaseous industrial processes as chemical-vapor depostion of semiconductor materials and in automotive engines operating on compressed natural gas.

  14. Controlling Gas-Flow Mass Ratios

    NASA Technical Reports Server (NTRS)

    Morris, Brian G.

    1990-01-01

    Proposed system automatically controls proportions of gases flowing in supply lines. Conceived for control of oxidizer-to-fuel ratio in new gaseous-propellant rocket engines. Gas-flow control system measures temperatures and pressures at various points. From data, calculates control voltages for electronic pressure regulators for oxygen and hydrogen. System includes commercially available components. Applicable to control of mass ratios in such gaseous industrial processes as chemical-vapor depostion of semiconductor materials and in automotive engines operating on compressed natural gas.

  15. Magnetic Amplifier for Power Flow Control

    SciTech Connect

    2012-02-24

    GENI Project: ORNL is developing an electromagnet-based, amplifier-like device that will allow for complete control over the flow of power within the electric grid. To date, complete control of power flow within the grid has been prohibitively expensive. ORNL’s controller could provide a reliable, cost-effective solution to this problem. The team is combining two types of pre-existing technologies to assist in flow control, culminating in a prototype iron-based magnetic amplifier. Ordinarily, such a device would require expensive superconductive wire, but the magnetic iron core of ORNL’s device could serve as a low-cost alternative that is equally adept at regulating power flow.

  16. Optimal feedback control of turbulent channel flow

    NASA Technical Reports Server (NTRS)

    Bewley, Thomas; Choi, Haecheon; Temam, Roger; Moin, Parviz

    1993-01-01

    Feedback control equations were developed and tested for computing wall normal control velocities to control turbulent flow in a channel with the objective of reducing drag. The technique used is the minimization of a 'cost functional' which is constructed to represent some balance of the drag integrated over the wall and the net control effort. A distribution of wall velocities is found which minimizes this cost functional some time shortly in the future based on current observations of the flow near the wall. Preliminary direct numerical simulations of the scheme applied to turbulent channel flow indicates it provides approximately 17 percent drag reduction. The mechanism apparent when the scheme is applied to a simplified flow situation is also discussed.

  17. High precision high flow range control valve

    DOEpatents

    McCray, John A.

    1999-01-01

    A fluid control valve is described having a valve housing having first and second valve housing openings for the ingress and egress of fluid through the control valve. Disposed within a void formed by the control valve is a sleeve having at least one sleeve opening to permit the flow of fluid therethrough. A flow restricter travels within the sleeve to progressively block off the sleeve opening and thereby control flow. A fluid passageway is formed between the first valve housing opening and the outer surface of the sleeve. A second fluid passageway is formed between the inside of the sleeve and the second valve housing opening. Neither fluid passageway contains more than one 90.degree. turn. In the preferred embodiment only one of the two fluid passageways contains a 90.degree. turn. In another embodiment, the control valve housing is bifurcated by a control surface having control surface opening disposed therethrough. A flow restricter is in slidable contact with the control surface to restrict flow of fluid through the control surface openings.

  18. High precision high flow range control valve

    DOEpatents

    McCray, J.A.

    1999-07-13

    A fluid control valve is described having a valve housing having first and second valve housing openings for the ingress and egress of fluid through the control valve. Disposed within a void formed by the control valve is a sleeve having at least one sleeve opening to permit the flow of fluid therethrough. A flow restricter travels within the sleeve to progressively block off the sleeve opening and thereby control flow. A fluid passageway is formed between the first valve housing opening and the outer surface of the sleeve. A second fluid passageway is formed between the inside of the sleeve and the second valve housing opening. Neither fluid passageway contains more than one 90 [degree] turn. In the preferred embodiment only one of the two fluid passageways contains a 90[degree] turn. In another embodiment, the control valve housing is bifurcated by a control surface having control surface opening disposed therethrough. A flow restricter is in slidable contact with the control surface to restrict flow of fluid through the control surface openings. 12 figs.

  19. Computational Simulations of Convergent Nozzles for the AIAA 1st Propulsion Aerodynamics Workshop

    NASA Technical Reports Server (NTRS)

    Dippold, Vance F., III

    2014-01-01

    Computational Fluid Dynamics (CFD) simulations were completed for a series of convergent nozzles in participation of the American Institute of Aeronautics and Astronautics (AIAA) 1st Propulsion Aerodynamics Workshop. The simulations were performed using the Wind-US flow solver. Discharge and thrust coefficients were computed for four axisymmetric nozzles with nozzle pressure ratios (NPR) ranging from 1.4 to 7.0. The computed discharge coefficients showed excellent agreement with available experimental data; the computed thrust coefficients captured trends observed in the experimental data, but over-predicted the thrust coefficient by 0.25 to 1.0 percent. Sonic lines were computed for cases with NPR >= 2.0 and agreed well with experimental data for NPR >= 2.5. Simulations were also performed for a 25 deg. conic nozzle bifurcated by a flat plate at NPR = 4.0. The jet plume shock structure was compared with and without the splitter plate to the experimental data. The Wind-US simulations predicted the shock structure well, though lack of grid resolution in the plume reduced the sharpness of the shock waves. Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations and Detached Eddy Simulations (DES) were performed at NPR = 1.6 for the 25 deg conic nozzle with splitter plate. The simulations predicted vortex shedding from the trailing edge of the splitter plate. However, the vortices of URANS and DES solutions appeared to dissipate earlier than observed experimentally. It is believed that a lack of grid resolution in the region of the vortex shedding may have caused the vortices to break down too soon

  20. Active Flow Control Stator With Coanda Surface

    NASA Technical Reports Server (NTRS)

    Guendogdu; Vorreiter; Seume

    2010-01-01

    Active Flow Control increases the permissible aerodynamic loading. Curved surface near the trailing edge ("Coanda surface"): a) increases turning -> higher pressure ratio. b) controls boundary layer separation -> increased surge margin. Objective: Reduce the number of vanes or compressor stages. Constraints: 1. In a real compressor, the vane must still function entirely without blowing. 2. Maintain the flow exit angle of the reference stator despite the resulting increase in stator loading.

  1. Value for controlling flow of cryogenic fluid

    DOEpatents

    Knapp, Philip A.

    1996-01-01

    A valve is provided for accurately controlling the flow of cryogenic fluids such as liquid nitrogen. The valve comprises a combination of disc and needle valves affixed to a valve stem in such a manner that the disc and needle are free to rotate about the stem, but are constrained in lateral and vertical movements. This arrangement provides accurate and precise fluid flow control and positive fluid isolation.

  2. Controllability of flow-conservation networks

    NASA Astrophysics Data System (ADS)

    Zhao, Chen; Zeng, An; Jiang, Rui; Yuan, Zhengzhong; Wang, Wen-Xu

    2017-07-01

    The ultimate goal of exploring complex networks is to control them. As such, controllability of complex networks has been intensively investigated. Despite recent advances in studying the impact of a network's topology on its controllability, a comprehensive understanding of the synergistic impact of network topology and dynamics on controllability is still lacking. Here, we explore the controllability of flow-conservation networks, trying to identify the minimal number of driver nodes that can guide the network to any desirable state. We develop a method to analyze the controllability on flow-conservation networks based on exact controllability theory, transforming the original analysis on adjacency matrix to Laplacian matrix. With this framework, we systematically investigate the impact of some key factors of networks, including link density, link directionality, and link polarity, on the controllability of these networks. We also obtain the analytical equations by investigating the network's structural properties approximatively and design the efficient tools. Finally, we consider some real networks with flow dynamics, finding that their controllability is significantly different from that predicted by only considering the topology. These findings deepen our understanding of network controllability with flow-conservation dynamics and provide a general framework to incorporate real dynamics in the analysis of network controllability.

  3. Control of Mixing and Reactive Flow Processes

    NASA Technical Reports Server (NTRS)

    Karagozian, A. R.

    1999-01-01

    The interdisciplinary field of reactive flow control is one that holds a great deal of promise for the optimization of complex phenomena occurring in many practical systems, ranging from automobile and gas turbine engines to environmental thermal destruction systems. The fundamental underpinnings of combustion control, however, require a detailed level of understanding of complex reactive flow phenomena, and, in the case of closed-loop active control, require the ability to sense (monitor) and actuate (manipulate) flow processes in a spatially distributed manner in "near real time". Hence the ultimate growth and success of the field of reactive flow control is intimately linked: 1) to advances in the understanding, simulation, and model reduction for complex reactive flows, 2) to the development of experimental diagnostic techniques, in particular, to the development of physically robust sensors, and 3) to the development of a framework or frameworks for generation of closed loop control algorithms suitable for unsteady, nonlinear reactive flow systems. The present paper seeks to outline the potential benefits and technical challenges that exist for mixing and combustion control in fundamental as well as practical systems and to identify promising research directions that could help meet these challenges.

  4. Control of Mixing and Reactive Flow Processes

    NASA Technical Reports Server (NTRS)

    Karagozian, A. R.

    1999-01-01

    The interdisciplinary field of reactive flow control is one that holds a great deal of promise for the optimization of complex phenomena occurring in many practical systems, ranging from automobile and gas turbine engines to environmental thermal destruction systems. The fundamental underpinnings of combustion control, however, require a detailed level of understanding of complex reactive flow phenomena, and, in the case of closed-loop active control, require the ability to sense (monitor) and actuate (manipulate) flow processes in a spatially distributed manner in "near real time". Hence the ultimate growth and success of the field of reactive flow control is intimately linked: 1) to advances in the understanding, simulation, and model reduction for complex reactive flows, 2) to the development of experimental diagnostic techniques, in particular, to the development of physically robust sensors, and 3) to the development of a framework or frameworks for generation of closed loop control algorithms suitable for unsteady, nonlinear reactive flow systems. The present paper seeks to outline the potential benefits and technical challenges that exist for mixing and combustion control in fundamental as well as practical systems and to identify promising research directions that could help meet these challenges.

  5. Cavity flow control using a rod in cross flow

    NASA Astrophysics Data System (ADS)

    Sarpotdar, Shekhar

    For a variety of aerodynamic conditions and geometric configurations fluid structure interactions give rise to a reverberant field. This phenomenon, referred to as resonant acoustics, has practical importance due to its undesirable effects such as noise, structural loading, and unsteady flow field. Several flow control technologies exist but they lose efficacy at off-design conditions. With the focus on expanding their operating envelope, the present work investigates the physics of the flow control using a combination of detailed experimental measurements and theoretical analysis. The model resonant acoustic flow problem that we chose for our study is cavity tones, i.e., the high intensity acoustic tones produced by high speed air moving over rectangular cavity. The flow control actuator is a rod in cross flow, i.e., a thin horizontal rod placed upstream of the cavity. In the present work, a detailed experimental study has been undertaken to characterize the acoustics, mean velocity field as well as the pressure perturbation field both inside and outside of the cavity. Control cases with contrasting suppression results are chosen to illustrate important aspects of the mean flow field. To investigate whether the cylinder, through its wake, changes the stability characteristics of the shear layer that develops over the cavity, stability analysis of the shear layer is undertaken. First, stability of artificial velocity profiles that are prototypical of the experimentally measured velocity profiles is investigated; in order to determine what parameters of the velocity profiles influence the stability of the shear layer the most. Next stability of experimentally measured velocity profiles is evaluated to calculate integrated growth rates along the length of the cavity. Mean velocity data is also used to elucidate the shear layer lift off mechanism of the rod. Both integrated growth range and shear layer lift off data are compared with the acoustic suppression results

  6. Monitoring And Controlling Hydroponic Flow

    NASA Technical Reports Server (NTRS)

    Dreschel, Thomas W.

    1992-01-01

    Pressure-monitoring and -controlling apparatus maintains slight suction required on nutrient solution in apparatus described in "Tubular Membrane Plant-Growth Unit" (KSC-11375), while overcoming gravity effects on operation of system on Earth. Suction helps to hold solution in tubular membrane.

  7. Guiding principles for vortex flow controls

    NASA Technical Reports Server (NTRS)

    Wu, J. Z.; Wu, J. M.

    1991-01-01

    In the practice of vortex flow controls, the most important factor is that the persistency and obstinacy of a concentrated vortex depend on its stability and dissipation. In this paper, the modern nonlinear stability theory for circulation-preserving flows is summarized, and the dissipation for general viscous flows is analyzed in terms of the evolution of total enstrophy. These analyses provide a theoretical base for understanding relevant physics of vortex flows, and lead to some guiding principles and methods for their controls. Case studies taken from various theoretical and/or experimental works of vortex controls, due to the present authors as well as others, confirm the feasibility of the recommended principles and methods.

  8. Method and apparatus for controlling fluid flow

    DOEpatents

    Miller, J.R.

    1980-06-27

    A method and apparatus for precisely controlling the rate (and hence amount) of fluid flow are given. The controlled flow rate is finely adjustable, can be extremely small (on the order of microliter-atmospheres per second), can be adjusted to zero (flow stopped), and is stable to better than 1% with time. The dead volume of the valve can be made arbitrarily small, in fact essentially zero. The valve employs no wearing mechanical parts (including springs, stems, or seals). The valve is finely adjustable, has a flow rate dynamic range of many decades, can be made compatible with any fluid, and is suitable for incorporation into an open or closed loop servo-control system.

  9. Flow around a semicircular cylinder with passive flow control mechanisms

    NASA Astrophysics Data System (ADS)

    Hamed, A. M.; Vega, J.; Liu, B.; Chamorro, L. P.

    2017-03-01

    Wind tunnel experiments were performed to study the effect of passive flow control strategies on the wake and drag of a semicircular cylinder of infinite aspect ratio. High-resolution planar particle image velocimetry was used to obtain flow statistics around the semicircular cylinder at Reynolds number Re≈ 3.2× 10^4 based on the cylinder diameter. The control mechanisms under consideration include rigid flaps of various lengths placed at the edges of the structure and a small slot along the symmetry plane of the cylinder. Mean velocity fields reveal the distinctive effects of each passive mechanism on the flow, such as velocity recovery, size of the recirculation bubble and location of the reattachment point. The distributions of turbulence kinetic energy and kinematic shear stress show the modulation of each passive control mechanism on the wake, including the onset and location of the maximum turbulence levels. Instantaneous and mean fields of swirling strength further highlight the role of the passive mechanisms in the vortex dynamics. Drag coefficient for the various cases was estimated indirectly from the flow measurements using a momentum balance. This approach shows that long flaps and slot were able to reduce drag with respect to the base case. The rigid flaps with length coincident with the diameter of the cylinder offered the best performance with drag reduction of ˜25%.

  10. A Content Analysis of AIAA/ITEA/ITEEA Conference Special Interest Sessions: 1978-2014

    ERIC Educational Resources Information Center

    Reed, Philip A.; LaPorte, James E.

    2015-01-01

    Associations routinely hold annual conferences to aid with professional development and actively promote the ideals of their membership and the profession they represent. The American Industrial Arts Association (AIAA) was created in 1939 and has held an annual conference the past 76 years to further these goals (Starkweather, 1995). Throughout…

  11. AIAA Employment Workshops (September 1, 1970-December 31, 1971). Volume III, Workshop Handbook.

    ERIC Educational Resources Information Center

    American Inst. of Aeronautics and Astronautics, New York, NY.

    In response to growing unemployment among professional personnel in the aerospace industry, a series of 175 workshops were conducted by the American Institute of Aeronautics and Astronautics (AIAA) in 43 cities. Nearly 15,000 unemployed engineers and scientists attended the workshops and reviewed job counseling and placement services from…

  12. AIAA Employment Workshops (September 1, 1970-December 31, 1971). Volume 1, Final Report.

    ERIC Educational Resources Information Center

    American Inst. of Aeronautics and Astronautics, New York, NY.

    In response to growing unemployment among professional personnel in the aerospace industry, a series of 175 workshops were conducted by the American Institute of Aeronautics and Astronautics (AIAA) in 43 cities. Nearly 15,000 unemployed engineers and scientists attended the workshops and reviewed job counseling and placement services from…

  13. Variable flow control for a nuclear reactor control rod

    DOEpatents

    Carleton, Richard D.; Bhattacharyya, Ajay

    1978-01-01

    A variable flow control for a control rod assembly of a nuclear reactor that depends on turbulent friction though an annulus. The annulus is formed by a piston attached to the control rod drive shaft and a housing or sleeve fitted to the enclosure housing the control rod. As the nuclear fuel is burned up and the need exists for increased reactivity, the control rods are withdrawn, which increases the length of the annulus and decreases the rate of coolant flow through the control rod assembly.

  14. Organization's Orderly Interest Exploration: Inception, Development and Insights of AIAA's Topics Database

    NASA Technical Reports Server (NTRS)

    Marshall, Jospeh R.; Morris, Allan T.

    2007-01-01

    Since 2003, AIAA's Computer Systems and Software Systems Technical Committees (TCs) have developed a database that aids technical committee management to map technical topics to their members. This Topics/Interest (T/I) database grew out of a collection of charts and spreadsheets maintained by the TCs. Since its inception, the tool has evolved into a multi-dimensional database whose dimensions include the importance, interest and expertise of TC members and whether or not a member and/or a TC is actively involved with the topic. In 2005, the database was expanded to include the TCs in AIAA s Information Systems Group and then expanded further to include all AIAA TCs. It was field tested at an AIAA Technical Activities Committee (TAC) Workshop in early 2006 through live access by over 80 users. Through the use of the topics database, TC and program committee (PC) members can accomplish relevant tasks such as: to identify topic experts (for Aerospace America articles or external contacts), to determine the interest of its members, to identify overlapping topics between diverse TCs and PCs, to guide new member drives and to reveal emerging topics. This paper will describe the origins, inception, initial development, field test and current version of the tool as well as elucidate the benefits and insights gained by using the database to aid the management of various TC functions. Suggestions will be provided to guide future development of the database for the purpose of providing dynamics and system level benefits to AIAA that currently do not exist in any technical organization.

  15. Innovative Flow Control Concepts for Drag Reduction

    NASA Technical Reports Server (NTRS)

    Lin, John C.; Whalen, Edward A.; Eppink, Jenna L.; Siochi, Emilie J.; Alexander, Michael G.; Andino, Marlyn Y.

    2016-01-01

    This paper highlights the technology development of two flow control concepts for aircraft drag reduction. The NASA Environmentally Responsible Aviation (ERA) project worked with Boeing to demonstrate these two concepts on a specially outfitted Boeing 757 ecoDemonstrator during the spring of 2015. The first flow control concept used Active Flow Control (AFC) to delay flow separation on a highly deflected rudder and increase the side force that it generates. This may enable a smaller vertical tail to provide the control authority needed in the event of an engine failure during takeoff and landing, while still operating in a conventional manner over the rest of the flight envelope. Thirty-one sweeping jet AFC actuators were installed and successfully flight-tested on the vertical tail of the 757 ecoDemonstrator. Pilot feedback, flow cone visualization, and analysis of the flight test data confirmed that the AFC is effective, as a smoother flight and enhanced rudder control authority were reported. The second flow control concept is the Insect Accretion Mitigation (IAM) innovation where surfaces were engineered to mitigate insect residue adhesion on a wing's leading edge. This is necessary because something as small as an insect residue on the leading edge of a laminar flow wing design can cause turbulent wedges that interrupt laminar flow, resulting in an increase in drag and fuel use. Several non-stick coatings were developed by NASA and applied to panels that were mounted on the leading edge of the wing of the 757 ecoDemonstrator. The performance of the coated surfaces was measured and validated by the reduction in the number of bug adhesions relative to uncoated control panels flown simultaneously. Both flow control concepts (i.e., sweeping jet actuators and non-stick coatings) for drag reduction were the culmination of several years of development, from wind tunnel tests to flight tests, and produced valuable data for the advancement of modern aircraft designs

  16. Recent developments in DBD plasma flow control

    NASA Astrophysics Data System (ADS)

    Wang, Jin-Jun; Choi, Kwing-So; Feng, Li-Hao; Jukes, Timothy N.; Whalley, Richard D.

    2013-10-01

    Flow control using DBD (dielectric-barrier-discharge) plasma actuators is a relatively new, but rapidly expanding area of research. There are a number of review papers available on this subject, but few discuss on their latest developments. The purpose of the present article is to “fill the gap” by reviewing the recent trend of plasma actuator design and to summarise aerodynamic control techniques. Here, we review new plasma actuators, such as plasma synthetic jet actuators, plasma spark jet actuators, three-dimensional plasma actuators and plasma vortex generators, which can induce three-dimensional flows away from the wall. We also review the starting vortex that leads to formation of a plasma wall jet. This is an important subject not only for a better understanding of the flow induced by DBD plasma actuators, but also as a database that can be used to calibrate the numerical models for plasma flow control. Design of DBD plasma actuators to obtain turbulent skin-friction reduction is shown and the modifications to near-wall turbulence structures are summarised. Novel applications of DBD plasma actuators for aerodynamic control are then discussed, including pitch and roll control, plasma jet vectoring, circulation control and plasma flap, showing a potential of DBD plasma actuators for replacing movable, aircraft control surfaces. Finally, vortex shedding control techniques by a number of different plasma actuators are surveyed.

  17. Linear control of oscillator and amplifier flows*

    NASA Astrophysics Data System (ADS)

    Schmid, Peter J.; Sipp, Denis

    2016-08-01

    Linear control applied to fluid systems near an equilibrium point has important applications for many flows of industrial or fundamental interest. In this article we give an exposition of tools and approaches for the design of control strategies for globally stable or unstable flows. For unstable oscillator flows a feedback configuration and a model-based approach is proposed, while for stable noise-amplifier flows a feedforward setup and an approach based on system identification is advocated. Model reduction and robustness issues are addressed for the oscillator case; statistical learning techniques are emphasized for the amplifier case. Effective suppression of global and convective instabilities could be demonstrated for either case, even though the system-identification approach results in a superior robustness to off-design conditions.

  18. Bluff Body Flow Control Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Thomas, Flint

    2005-11-01

    In this study, the use of single dielectric barrier discharge plasma actuators for the control of bluff body flow separation is investigated. In particular, surface mounted plasma actuators are used to reduce both drag and unsteady vortex shedding from circular cylinders in cross-flow. It is demonstrated that the plasma-induced surface blowing gives rise to a local Coanda effect that promotes the maintenance of flow attachment. Large reductions in vortex shedding and drag are demonstrated for Reynolds numbers ˜ 10^410^5. Both steady and unsteady plasma-induced surface blowing is explored. Results are presented from experiments involving both two and four surface mounted actuators.

  19. Control of Flow Separation Using Adaptive Airfoils

    NASA Technical Reports Server (NTRS)

    Chandrasekhara, M. S.; Wilder, M. C.; Carr, L. W.; Davis, Sanford S. (Technical Monitor)

    1996-01-01

    A novel way of controlling flow separation is reported. The approach involves using an adaptive airfoil geometry that changes its leading edge shape to adjust to the instantaneous flow at high angles of attack such that the flow over it remains attached. In particular, a baseline NACA 0012 airfoil, whose leading edge curvature could be changed dynamically by 400% was tested under quasi-steady compressible flow conditions. A mechanical drive system was used to produce a rounded leading edge to reduce the strong local flow acceleration around its nose and thus reduce the strong adverse pressure gradient that follows such a rapid acceleration. Tests in steady flow showed that at M = 0.3, the flow separated at about 14 deg. angle of attack for the NACA 0012 profile but could be kept attached up to an angle of about 18 deg by changing the nose curvature. No significant hysteresis effects were observed; the flow could be made to reattach from its separated state at high angles by changing the leading edge curvature.

  20. RETROFITTING CONTROL FACILITIES FOR WET-WEATHER FLOW CONTROL

    EPA Science Inventory

    Available technologies were evaluated to demonstrate the feasibility and cost effectiveness of retrofitting existing facilities to handle wet-weather flow (WWF). Cost/benefit relationships were compared to construction of new conventional control and treatment facilities. Desktop...

  1. Variable Frequency Diverter Actuation for Flow Control

    NASA Technical Reports Server (NTRS)

    Culley, Dennis E.

    2006-01-01

    The design and development of an actively controlled fluidic actuator for flow control applications is explored. The basic device, with one input and two output channels, takes advantage of the Coanda effect to force a fluid jet to adhere to one of two axi-symmetric surfaces. The resultant flow is bi-stable, producing a constant flow from one output channel, until a disturbance force applied at the control point causes the flow to switch to the alternate output channel. By properly applying active control the output flows can be manipulated to provide a high degree of modulation over a wide and variable range of frequency and duty cycle. In this study the momentary operative force is applied by small, high speed isolation valves of which several different types are examined. The active fluidic diverter actuator is shown to work in several configurations including that in which the operator valves are referenced to atmosphere as well as to a source common with the power stream.

  2. Method for controlling coolant flow in airfoil, flow control structure and airfoil incorporating the same

    DOEpatents

    Itzel, Gary Michael; Devine, II, Robert Henry; Chopra, Sanjay; Toornman, Thomas Nelson

    2003-07-08

    A coolant flow control structure is provided to channel cooling media flow to the fillet region defined at the transition between the wall of a nozzle vane and a wall of a nozzle segment, for cooling the fillet region. In an exemplary embodiment, the flow control structure defines a gap with the fillet region to achieve the required heat transfer coefficients in this region to meet part life requirements.

  3. Summary of Data from the Sixth AIAA CFD Drag Prediction Workshop: CRM Cases 2 to 5

    NASA Technical Reports Server (NTRS)

    Tinoco, Edward N.; Brodersen, Olaf P.; Keye, Stefan; Laflin, Kelly R.; Feltrop, Edward; Vassberg, John C.; Mani, Mori; Rider, Ben; Wahls, Richard A.; Morrison, Joseph H.; hide

    2017-01-01

    Results from the Sixth AIAA CFD Drag Prediction Workshop Common Research Model Cases 2 to 5 are presented. As with past workshops, numerical calculations are performed using industry-relevant geometry, methodology, and test cases. Cases 2 to 5 focused on force/moment and pressure predictions for the NASA Common Research Model wing-body and wing-body-nacelle-pylon configurations, including Case 2 - a grid refinement study and nacelle-pylon drag increment prediction study; Case 3 - an angle-of-attack buffet study; Case 4 - an optional wing-body grid adaption study; and Case 5 - an optional wing-body coupled aero-structural simulation. The Common Research Model geometry differed from previous workshops in that it was deformed to the appropriate static aeroelastic twist and deflection at each specified angle-of-attack. The grid refinement study used a common set of overset and unstructured grids, as well as user created Multiblock structured, unstructured, and Cartesian based grids. For the supplied common grids, six levels of refinement were created resulting in grids ranging from 7x10(exp 6) to 208x10(exp 6) cells. This study (Case 2) showed further reduced scatter from previous workshops, and very good prediction of the nacelle-pylon drag increment. Case 3 studied buffet onset at M=0.85 using the Medium grid (20 to 40x10(exp 6) nodes) from the above described sequence. The prescribed alpha sweep used finely spaced intervals through the zone where wing separation was expected to begin. Although the use of the prescribed aeroelastic twist and deflection at each angle-of-attack greatly improved the wing pressure distribution agreement with test data, many solutions still exhibited premature flow separation. The remaining solutions exhibited a significant spread of lift and pitching moment at each angle-of-attack, much of which can be attributed to excessive aft pressure loading and shock location variation. Four Case 4 grid adaption solutions were submitted. Starting

  4. Coordinated Control of Cross-Flow Turbines

    NASA Astrophysics Data System (ADS)

    Strom, Benjamin; Brunton, Steven; Polagye, Brian

    2016-11-01

    Cross-flow turbines, also known as vertical-axis turbines, have several advantages over axial-flow turbines for a number of applications including urban wind power, high-density arrays, and marine or fluvial currents. By controlling the angular velocity applied to the turbine as a function of angular blade position, we have demonstrated a 79 percent increase in cross-flow turbine efficiency over constant-velocity control. This strategy uses the downhill simplex method to optimize control parameter profiles during operation of a model turbine in a recirculating water flume. This optimization method is extended to a set of two turbines, where the blade motions and position of the downstream turbine are optimized to beneficially interact with the coherent structures in the wake of the upstream turbine. This control scheme has the potential to enable high-density arrays of cross-flow turbines to operate at cost-effective efficiency. Turbine wake and force measurements are analyzed for insight into the effect of a coordinated control strategy.

  5. Declarative flow control for distributed instrumentation

    SciTech Connect

    Parvin, Bahram; Taylor, John; Fontenay, Gerald; Callahan, Daniel

    2001-06-01

    We have developed a 'microscopy channel' to advertise a unique set of on-line scientific instruments and to let users join a particular session, perform an experiment, collaborate with other users, and collect data for further analysis. The channel is a collaborative problem solving environment (CPSE) that allows for both synchronous and asynchronous collaboration, as well as flow control for enhanced scalability. The flow control is a declarative feature that enhances software functionality at the experimental scale. Our testbed includes several unique electron and optical microscopes with applications ranging from material science to cell biology. We have built a system that leverages current commercial CORBA services, Web Servers, and flow control specifications to meet diverse requirements for microscopy and experimental protocols. In this context, we have defined and enhanced Instrument Services (IS), Exchange Services (ES), Computational Services (CS), and Declarative Services (DS) that sit on top of CORBA and its enabling services (naming, trading, security, and notification) IS provides a layer of abstraction for controlling any type of microscope. ES provides a common set of utilities for information management and transaction. CS provides the analytical capabilities needed for online microscopy. DS provides mechanisms for flow control for improving the dynamic behavior of the system.

  6. Magnetically actuated microvalve for active flow control

    NASA Astrophysics Data System (ADS)

    Olivier, Ducloux; Abdelkrim, Talbi; Yves, Deblock; Leticia, Gimeno; Nicolas, Tiercelin; Philippe, Pernod; Vladimir, Preobrazhensky; Alain, Merlen

    2006-04-01

    The reattachment of separated air flows can be actively controlled by blowing oscillatory air jets in the boundary layer, through submillimetric holes situated near the separation edge. To achieve such pulsed jets, a high flow rate, high actuation frequency microvalve was designed, fabricated and characterized. The microvalve is fed by a pressurized source of air, and its inner channel is alternatively pinched by a PDMS polymer membrane, modulating the air flow which is addressed towards the separated surface. Magnetostatic actuation was chosen for its high stress, high displacement, and remote actuation capabilities. The actuation consists in coupling an inductive driving coil and a NdFeB permanent magnet situated on the PDMS flexible membrane. Characterization of the resonance frequency, and vibration amplitude are achieved by interferometric means. The output flow is characterized using strioscopy visualization and hot wire anemometry methods. The design and fabrication process of the microsystem, and the results of these characterizations are presented in this paper.

  7. Model Reduction for Flow Analysis and Control

    NASA Astrophysics Data System (ADS)

    Rowley, Clarence W.; Dawson, Scott T. M.

    2017-01-01

    Advances in experimental techniques and the ever-increasing fidelity of numerical simulations have led to an abundance of data describing fluid flows. This review discusses a range of techniques for analyzing such data, with the aim of extracting simplified models that capture the essential features of these flows, in order to gain insight into the flow physics, and potentially identify mechanisms for controlling these flows. We review well-developed techniques, such as proper orthogonal decomposition and Galerkin projection, and discuss more recent techniques developed for linear systems, such as balanced truncation and dynamic mode decomposition (DMD). We then discuss some of the methods available for nonlinear systems, with particular attention to the Koopman operator, an infinite-dimensional linear operator that completely characterizes the dynamics of a nonlinear system and provides an extension of DMD to nonlinear systems.

  8. Experimental and Numerical Investigation of Controlled, Small-Scale Motions in a Turbulent Shear Layer

    DTIC Science & Technology

    2007-06-01

    Control of Supersonic Impinging Jet Flows using Microjets . AIAA Journal. 41(7):1347-1355, 2001. [9] M.J. Stanek, G. Raman, V. Kibens, J.A. Ross, J. Odedra...synthetic jet actuators [4]. The previous investigations have demonstrated that high-frequency actuation has a profound impact on evolution of free ...public release, distribution unlimited 13. SUPPLEMENTARY NOTES Third International Symposium on Integrating CFD and Experiments in Aerodynamics, June 20

  9. Fuel cell with internal flow control

    DOEpatents

    Haltiner, Jr., Karl J.; Venkiteswaran, Arun [Karnataka, IN

    2012-06-12

    A fuel cell stack is provided with a plurality of fuel cell cassettes where each fuel cell cassette has a fuel cell with an anode and cathode. The fuel cell stack includes an anode supply chimney for supplying fuel to the anode of each fuel cell cassette, an anode return chimney for removing anode exhaust from the anode of each fuel cell cassette, a cathode supply chimney for supplying oxidant to the cathode of each fuel cell cassette, and a cathode return chimney for removing cathode exhaust from the cathode of each fuel cell cassette. A first fuel cell cassette includes a flow control member disposed between the anode supply chimney and the anode return chimney or between the cathode supply chimney and the cathode return chimney such that the flow control member provides a flow restriction different from at least one other fuel cell cassettes.

  10. PRIMING THE PUMP AND CONTROLLING THE FLOW.

    ERIC Educational Resources Information Center

    BUCHAN, VIVIAN

    THE BEGINNING WRITER NEEDS BOTH ENCOURAGEMENT AND DIRECTION. ONCE A STUDENT, NONVERBAL OR FLUENT, HAS EXPRESSED AN OPINION, SIGNIFICANT OR TRIVIAL, THE PUMP CAN BE PRIMED BY ASKING HIM "WHY," AND HIS FLOW OF "BECAUSES" CAN BE CONTROLLED BY CHANNELING THEM INTO A SIMPLE PATTERN. THE NONVERBAL STUDENT IS ENCOURAGED TO WRITE WHEN HE LEARNS THAT A…

  11. Closed Loop Control and Turbulent Flows

    DTIC Science & Technology

    2005-10-01

    first described in some detail by Ingard [8], but re-discovered, developed, and applied to problems in flow control by Glezer and co-workers [19, 20... Ingard . On the theory and design of acoustic resonators. J. Acoustical Soc. of America, 25(6):1037-1060, 1953. [9] J. Kim, P. Moin, and R. Moser

  12. Active Flow Control with Thermoacoustic Actuators

    DTIC Science & Technology

    2014-01-31

    dielectric barrier discharge ( DBD ) plasma actuators [4], or combustion powered actuators [5]. Compared to passive flow control techniques, such as vortex...space nor adding significant weight, which is similar to how DBD plasma actuators can be installed. 3 The sound generation mechanism, known as

  13. Control of microorganisms in flowing nutrient solutions

    NASA Astrophysics Data System (ADS)

    Evans, R. D.

    1994-11-01

    Controlling microorganisms in flowing nutrient solutions involves different techniques when targeting the nutrient solution, hardware surfaces in contact with the solution, or the active root zone. This review presents basic principles and applications of a number of treatment techniques, including disinfection by chemicals, ultrafiltration, ultrasonics, and heat treatment, with emphasis on UV irradiation and ozone treatment. Procedures for control of specific pathogens by nutrient solution conditioning also are reviewed.

  14. Control of microorganisms in flowing nutrient solutions.

    PubMed

    Evans, R D

    1994-11-01

    Controlling microorganisms in flowing nutrient solutions involves different techniques when targeting the nutrient solution, hardware surfaces in contact with the solution, or the active root zone. This review presents basic principles and applications of a number of treatment techniques, including disinfection by chemicals, ultrafiltration, ultrasonics, and heat treatment, with emphasis on UV irradiation and ozone treatment. Procedures for control of specific pathogens by nutrient solution conditioning also are reviewed.

  15. Active flow control of subsonic flow in an adverse pressure gradient using synthetic jets and passive micro flow control devices

    NASA Astrophysics Data System (ADS)

    Denn, Michael E.

    Several recent studies have shown the advantages of active and/or passive flow control devices for boundary layer flow modification. Many current and future proposed air vehicles have very short or offset diffusers in order to save vehicle weight and create more optimal vehicle/engine integration. Such short coupled diffusers generally result in boundary layer separation and loss of pressure recovery which reduces engine performance and in some cases may cause engine stall. Deployment of flow control devices can alleviate this problem to a large extent; however, almost all active flow control devices have some energy penalty associated with their inclusion. One potential low penalty approach for enhancing the diffuser performance is to combine the passive flow control elements such as micro-ramps with active flow control devices such as synthetic jets to achieve higher control authority. The goal of this dissertation is twofold. The first objective is to assess the ability of CFD with URANS turbulence models to accurately capture the effects of the synthetic jets and micro-ramps on boundary layer flow. This is accomplished by performing numerical simulations replicating several experimental test cases conducted at Georgia Institute of Technology under the NASA funded Inlet Flow Control and Prediction Technologies Program, and comparing the simulation results with experimental data. The second objective is to run an expanded CFD matrix of numerical simulations by varying various geometric and other flow control parameters of micro-ramps and synthetic jets to determine how passive and active control devices interact with each other in increasing and/or decreasing the control authority and determine their influence on modification of boundary layer flow. The boundary layer shape factor is used as a figure of merit for determining the boundary layer flow quality/modification and its tendency towards separation. It is found by a large number of numerical experiments and

  16. Statistical Analysis of CFD Solutions from the 6th AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Derlaga, Joseph M.; Morrison, Joseph H.

    2017-01-01

    A graphical framework is used for statistical analysis of the results from an extensive N- version test of a collection of Reynolds-averaged Navier-Stokes computational uid dynam- ics codes. The solutions were obtained by code developers and users from North America, Europe, Asia, and South America using both common and custom grid sequencees as well as multiple turbulence models for the June 2016 6th AIAA CFD Drag Prediction Workshop sponsored by the AIAA Applied Aerodynamics Technical Committee. The aerodynamic con guration for this workshop was the Common Research Model subsonic transport wing- body previously used for both the 4th and 5th Drag Prediction Workshops. This work continues the statistical analysis begun in the earlier workshops and compares the results from the grid convergence study of the most recent workshop with previous workshops.

  17. Optimal Actuator Dimensions for Flow Control

    NASA Astrophysics Data System (ADS)

    Hofmann, L. M.; Haritonidis, J. H.; Herbert, Th.

    1996-11-01

    By using a local source, we produce wave trains and wave packets that develop in a strongly unstable laminar boundary layer. Computer simulations and wind-tunnel experiments show that these disturbances can be attenuated by a membrane actuator via wave superposition. Using DNS, we optimize actuators to generate specific single mode disturbances. This optimization is important for the integration of multiple actuators into an array which cancels more general, in particular natural disturbances. We investigate actuators in continuous sinusoidal motion to determine dimensions which most accurately reproduce the streamwise velocity profiles of naturally occuring disturbances and generate the largest streamwise velocity perturbations downstream of the actuator. The computational results are compared with experimental data. This comparison validates the computational design procedure for efficient actuators which is essential for the implementation of our ``smart wall'' concept^1 to delay transition in laminar boundary layers. ^1 X. Fan, L. M. Hofmann, Th. Herbert, AIAA 93-3273, 1993 ^ Supported by AFOSR Contract F49620-93-1-0135.

  18. Rotatable non-circular forebody flow controller

    NASA Technical Reports Server (NTRS)

    Moskovitz, Cary A. (Inventor)

    1991-01-01

    The invention is a rotatable, non-circular forebody flow controller. The apparatus comprises a small geometric device located at a nose of a forebody of an aircraft and a non-circular cross-sectional area that extends toward the apex of the aircraft. The device is symmetrical about a reference plane and preferably attaches to an axle which in turn attaches to a rotating motor. The motor rotates the device about an axis of rotation. Preferably, a control unit connected to an aircraft flight control computer signals to the rotating motor the proper rotational positioning of the geometric device.

  19. Nuclear engine flow reactivity shim control

    DOEpatents

    Walsh, J.M.

    1973-12-11

    A nuclear engine control system is provided which automatically compensates for reactor reactivity uncertainties at the start of life and reactivity losses due to core corrosion during the reactor life in gas-cooled reactors. The coolant gas flow is varied automatically by means of specially provided control apparatus so that the reactor control drums maintain a predetermined steady state position throughout the reactor life. This permits the reactor to be designed for a constant drum position and results in a desirable, relatively flat temperature profile across the core. (Official Gazette)

  20. Assessment of the Draft AIAA S-119 Flight Dynamic Model Exchange Standard

    NASA Technical Reports Server (NTRS)

    Jackson, E. Bruce; Murri, Daniel G.; Hill, Melissa A.; Jessick, Matthew V.; Penn, John M.; Hasan, David A.; Crues, Edwin Z.; Falck, Robert D.; McCarthy, Thomas G.; Vuong, Nghia; Zimmerman, Curtis

    2011-01-01

    An assessment of a draft AIAA standard for flight dynamics model exchange, ANSI/AIAA S-119-2011, was conducted on behalf of NASA by a team from the NASA Engineering and Safety Center. The assessment included adding the capability of importing standard models into real-time simulation facilities at several NASA Centers as well as into analysis simulation tools. All participants were successful at importing two example models into their respective simulation frameworks by using existing software libraries or by writing new import tools. Deficiencies in the libraries and format documentation were identified and fixed; suggestions for improvements to the standard were provided to the AIAA. An innovative tool to generate C code directly from such a model was developed. Performance of the software libraries compared favorably with compiled code. As a result of this assessment, several NASA Centers can now import standard models directly into their simulations. NASA is considering adopting the now-published S-119 standard as an internal recommended practice.

  1. Active shear flow control for improved combustion

    NASA Astrophysics Data System (ADS)

    Gutmark, E.; Parr, T. P.; Hanson-Parr, D. M.; Schadow, K. C.

    1990-01-01

    The acoustical and fluid dynamic facets of an excited premixed flame were studied experimentally to evaluate possibilities for development of a stabilizing closed-loop control system. The flame was analyzed as a nonlinear system which includes different subcomponents: acoustics, fluid dynamics, and chemical reaction. Identification of the acoustical and fluid dynamics subsystems is done by analyzing the transfer function, which was obtained by driving the system with both white-noise and a frequency-sweeping sine-wave. The features obtained by this analysis are compared to results of flow visualization and hot-wire flow-field and spectral measurements. The acoustical subsystem is determined by the resonant acoustic modes of the settling chamber. These modes are subsequently filtered and amplified by the flow shear layer, whose instability characteristics are dominated by the preferred mode frequency.

  2. Adaptive wing and flow control technology

    NASA Astrophysics Data System (ADS)

    Stanewsky, E.

    2001-10-01

    The development of the boundary layer and the interaction of the boundary layer with the outer “inviscid” flow field, exacerbated at high speed by the occurrence of shock waves, essentially determine the performance boundaries of high-speed flight. Furthermore, flight and freestream conditions may change considerably during an aircraft mission while the aircraft itself is only designed for multiple but fixed design points thus impairing overall performance. Consequently, flow and boundary layer control and adaptive wing technology may have revolutionary new benefits for take-off, landing and cruise operating conditions for many aircraft by enabling real-time effective geometry optimization relative to the flight conditions. In this paper we will consider various conventional and novel means of boundary layer and flow control applied to moderate-to-large aspect ratio wings, delta wings and bodies with the specific objectives of drag reduction, lift enhancement, separation suppression and the improvement of air-vehicle control effectiveness. In addition, adaptive wing concepts of varying complexity and corresponding aerodynamic performance gains will be discussed, also giving some examples of possible structural realizations. Furthermore, penalties associated with the implementation of control and adaptation mechanisms into actual aircraft will be addressed. Note that the present contribution is rather application oriented.

  3. Accurate, reliable control of process gases by mass flow controllers

    SciTech Connect

    Hardy, J.; McKnight, T.

    1997-02-01

    The thermal mass flow controller, or MFC, has become an instrument of choice for the monitoring and controlling of process gas flow throughout the materials processing industry. These MFCs are used on CVD processes, etching tools, and furnaces and, within the semiconductor industry, are used on 70% of the processing tools. Reliability and accuracy are major concerns for the users of the MFCs. Calibration and characterization technologies for the development and implementation of mass flow devices are described. A test facility is available to industry and universities to test and develop gas floe sensors and controllers and evaluate their performance related to environmental effects, reliability, reproducibility, and accuracy. Additional work has been conducted in the area of accuracy. A gravimetric calibrator was invented that allows flow sensors to be calibrated in corrosive, reactive gases to an accuracy of 0.3% of reading, at least an order of magnitude better than previously possible. Although MFCs are typically specified with accuracies of 1% of full scale, MFCs may often be implemented with unwarranted confidence due to the conventional use of surrogate gas factors. Surrogate gas factors are corrections applied to process flow indications when an MFC has been calibrated on a laboratory-safe surrogate gas, but is actually used on a toxic, or corrosive process gas. Previous studies have indicated that the use of these factors may cause process flow errors of typically 10%, but possibly as great as 40% of full scale. This paper will present possible sources of error in MFC process gas flow monitoring and control, and will present an overview of corrective measures which may be implemented with MFC use to significantly reduce these sources of error.

  4. Summary of the Third AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Vassberg, John C.; Tinoco, Edward N.; Mani, Mori; Brodersen, Olaf P.; Eisfeld, Bernhard; Wahls, Richard A.; Morrison, Joseph H.; Zickuhr, Tom; Laflin, Kelly R.; Mavriplis, DImitri J.

    2007-01-01

    The workshop focused on the prediction of both absolute and differential drag levels for wing-body and wing-al;one configurations of that are representative of transonic transport aircraft. The baseline DLR-F6 wing-body geometry, previously utilized in DPW-II, is also augmented with a side-body fairing to help reduce the complexity of the flow physics in the wing-body juncture region. In addition, two new wing-alone geometries have been developed for the DPW-II. Numerical calculations are performed using industry-relevant test cases that include lift-specific and fixed-alpha flight conditions, as well as full drag polars. Drag, lift, and pitching moment predictions from previous Reynolds-Averaged Navier-Stokes computational fluid Dynamics Methods are presented, focused on fully-turbulent flows. Solutions are performed on structured, unstructured, and hybrid grid systems. The structured grid sets include point-matched multi-block meshes and over-set grid systems. The unstructured and hybrid grid sets are comprised of tetrahedral, pyramid, and prismatic elements. Effort was made to provide a high-quality and parametrically consistent family of grids for each grid type about each configuration under study. The wing-body families are comprised of a coarse, medium, and fine grid, while the wing-alone families also include an extra-fine mesh. These mesh sequences are utilized to help determine how the provided flow solutions fair with respect to asymptotic grid convergence, and are used to estimate an absolute drag of each configuration.

  5. Control of Spatially Inhomogeneous Shear Flows

    DTIC Science & Technology

    2009-11-27

    control approach, that minimises an objective function which measures the perturbation energy , was formulated where the Orr- Sommerfeld and Squire...hydrodynamic stability analysis by considering a finite-time horizon over which energy amplification, driven by a specific input (disturbances/actuator) and...layers subject to free-stream turbulence. Int. J. Heat Fluid Flow, 29(3):841–855, 2008. [14] B. Moore. Principal component analysis in linear systems

  6. Control of jet flow mixing and stabilization

    NASA Astrophysics Data System (ADS)

    Yuan, Chih-Chung

    This dissertation examines the effect of feedback controllers on mixing and stabilization of unstable two-dimensional jet flows. The mixing enhancement control law uses a pair of actuators at the jet nozzle exit acting on the shear layers near the corners by blowing and subtracting fluid in an anti-symmetric fashion with a zero net mass flux. The sensor measures the pressure difference across the nozzle diameter and is either located at downstream or at the nozzle exit with time delay. If the length/time scale is long enough and the feedback gain is sufficiently large, this control strategy will provide a constant vortex generation pattern that successfully improves mixing. The evolution of a passive scalar and mixing of particles with mass in jet flows are visualized and quantified. Probability Density Functions based on the particle/scalar distribution are constructed as measures of mixing. The stabilization control law employs filaments with distributed sensors and actuators in the jet flow. The sensors measure the local pressure difference across nozzle diameter and the actuators act as a reaction body force in the normal direction. The instability is damped with sufficiently large feedback gain. The Reynolds numbers of jet flows studied are 100 and 150 that are in the transient range. The results are obtained by means of Direct Numerical Simulation. The Navier-Stokes equations are spatially discretized by second order finite-difference method and advanced in time using a fractional step technique with a hybrid Runge-Kutta/Crank-Nicolson time discretization. This hybrid technique is developed to gain a larger time step while numerical stability is maintained. Stretched and staggered grids are used in both stream-wise and normal directions. The simulation results are validated by comparison with previous works and through self-similar analysis.

  7. Recent Progress in Biomimetic Flow Control

    DTIC Science & Technology

    2014-09-19

    paper, two types of flow control devices were examined: (1) devices attached or added to wing surfaces for high aerodynamic performance; (2) smart...and wing -surface devices, and they successfully enhanced the aerodynamic performance and/or reduced the drag force. Since the animal locomotion...governs the functioning of organ- isms. The work of engineers links the biological discoveries and conjectures to the analysis of mechanism by testing

  8. Laminar flow control flight experiment design

    NASA Astrophysics Data System (ADS)

    Tucker, Aaron Alexander

    Demonstration of spanwise-periodic discrete roughness element laminar flow control (DRE LFC) technology at operationally relevant flight regimes requires extremely stable flow conditions in flight. A balance must be struck between the capabilities of the host aircraft and the scientific apparatus. A safe, effective, and efficient flight experiment is described to meet the test objectives, a flight test technique is designed to gather research-quality data, flight characteristics are analyzed for data compatibility, and an experiment is designed for data collection and analysis. The objective is to demonstrate DRE effects in a flight environment relevant to transport-category aircraft: [0.67 -- 0.75] Mach number and [17.0M -- 27.5M] Reynolds number. Within this envelope, flight conditions are determined which meet evaluation criteria for minimum lift coefficient and crossflow transition location. The angle of attack data band is determined, and the natural laminar flow characteristics are evaluated. Finally, DRE LFC technology is demonstrated in the angle of attack data band at the specified flight conditions. Within the angle of attack data band, a test angle of attack must be maintained with a tolerance of +/- 0.1° for 15 seconds. A flight test technique is developed that precisely controls angle of attack. Lateral-directional stability characteristics of the host aircraft are exploited to manipulate the position of flight controls near the wing glove. Directional control inputs are applied in conjunction with lateral control inputs to achieve the desired flow conditions. The data are statistically analyzed in a split-plot factorial that produces a system response model in six variables: angle of attack, Mach number, Reynolds number, DRE height, DRE spacing, and the surface roughness of the leading edge. Predictions on aircraft performance are modeled to enable planning tools for efficient flight research while still producing statistically rigorous flight data

  9. Investigations of Fluid-Structure-Coupling and Turbulence Model Effects on the DLR Results of the Fifth AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Keye, Stefan; Togiti, Vamish; Eisfeld, Bernhard; Brodersen, Olaf P.; Rivers, Melissa B.

    2013-01-01

    The accurate calculation of aerodynamic forces and moments is of significant importance during the design phase of an aircraft. Reynolds-averaged Navier-Stokes (RANS) based Computational Fluid Dynamics (CFD) has been strongly developed over the last two decades regarding robustness, efficiency, and capabilities for aerodynamically complex configurations. Incremental aerodynamic coefficients of different designs can be calculated with an acceptable reliability at the cruise design point of transonic aircraft for non-separated flows. But regarding absolute values as well as increments at off-design significant challenges still exist to compute aerodynamic data and the underlying flow physics with the accuracy required. In addition to drag, pitching moments are difficult to predict because small deviations of the pressure distributions, e.g. due to neglecting wing bending and twisting caused by the aerodynamic loads can result in large discrepancies compared to experimental data. Flow separations that start to develop at off-design conditions, e.g. in corner-flows, at trailing edges, or shock induced, can have a strong impact on the predictions of aerodynamic coefficients too. Based on these challenges faced by the CFD community a working group of the AIAA Applied Aerodynamics Technical Committee initiated in 2001 the CFD Drag Prediction Workshop (DPW) series resulting in five international workshops. The results of the participants and the committee are summarized in more than 120 papers. The latest, fifth workshop took place in June 2012 in conjunction with the 30th AIAA Applied Aerodynamics Conference. The results in this paper will evaluate the influence of static aeroelastic wing deformations onto pressure distributions and overall aerodynamic coefficients based on the NASA finite element structural model and the common grids.

  10. Shallow flow vortex formation and control

    NASA Astrophysics Data System (ADS)

    Fu, Haojun

    Vortical structures in shallow flow past a vertical cylinder are addressed in this investigation. A cinema technique of digital particle image velocimetry (DPIV) provided quantitative representations of the wholefield flow patterns in both instantaneous and averaged forms. Techniques for passive and active control of these vortices, and their influence on the loading of the bed, were explored. In a fully-developed, laminar shallow flow, the unstable structure in the near-wake of the cylinder correlates with the horseshoe (necklace) vortex system about the upstream surface of the cylinder. A coherent varicose mode of vortex formation is observed in the near-wake, even though the classical large-scale vortex shedding is suppressed due to bed friction effects. It is also demonstrated that when the near-wake is stable at a sufficiently low value of Reynolds number, applications of external perturbations lead to destabilization of the wake. Classes of small-scale three-dimensional structures arise in a fully-turbulent shallow flow past a surface-piercing cylinder. A prevalent feature is an upward moving jet-like flow from the bed surface, through the center of the developing quasi-two-dimensional primary vortex, at a location in the very near-wake of the cylinder. Passive control via base-bleed through a narrow streamwise slot leads to substantially delay/attenuation of vortex formation in the near-wake. The large-scale near-wake structure is recoverable through combined positive-active control, in the form of rotational perturbations in the presence of small magnitude base bleed. These alterations of the near-wake structure occur in conjunction with modifications of the streamline topology and Reynolds stress at the bed, as well as the shallow approach flow. Active control via rotational perturbations of the cylinder at the most unstable shear-layer frequency promotes well-defined vortical structures in the separating shearlayer, which contribute to the earlier

  11. Wake flow control using a dynamically controlled wind turbine

    NASA Astrophysics Data System (ADS)

    Castillo, Ricardo; Wang, Yeqin; Pol, Suhas; Swift, Andy; Hussain, Fazle; Westergaard, Carsten; Texas Tech University Team

    2016-11-01

    A wind tunnel based "Hyper Accelerated Wind Farm Kinematic-Control Simulator" (HAWKS) is being built at Texas Tech University to emulate controlled wind turbine flow physics. The HAWKS model turbine has pitch, yaw and speed control which is operated in real model time, similar to that of an equivalent full scale turbine. Also, similar to that of a full scale wind turbine, the controls are developed in a Matlab Simulink environment. The current diagnostic system consists of power, rotor position, rotor speed measurements and PIV wake characterization with four cameras. The setup allows up to 7D downstream of the rotor to be mapped. The purpose of HAWKS is to simulate control strategies at turnaround times much faster than CFD and full scale testing. The fundamental building blocks of the simulator have been tested, and demonstrate wake steering for both static and dynamic turbine actuation. Parameters which have been studied are yaw, rotor speed and combinations hereof. The measured wake deflections for static yaw cases are in agreement with previously reported research implying general applicability of the HAWKS platform for the purpose of manipulating the wake. In this presentation the general results will be introduced followed by an analysis of the wake turbulence and coherent structures when comparing static and dynamic flow cases. The outcome of such studies could ultimately support effective wind farm wake flow control strategies. Texas Emerging Technology Fund (ETF).

  12. Electromechanically Actuated Valve for Controlling Flow Rate

    NASA Technical Reports Server (NTRS)

    Patterson, Paul

    2007-01-01

    A proposed valve for controlling the rate of flow of a fluid would include an electric-motor-driven ball-screw mechanism for adjusting the seating element of the valve to any position between fully closed and fully open. The motor would be of a type that can be electronically controlled to rotate to a specified angular position and to rotate at a specified rate, and the ball screw would enable accurate linear positioning of the seating element as a function of angular position of the motor. Hence, the proposed valve would enable fine electronic control of the rate of flow and the rate of change of flow. The uniqueness of this valve lies in a high degree of integration of the actuation mechanism with the flow-control components into a single, relatively compact unit. A notable feature of this integration is that in addition to being a major part of the actuation mechanism, the ball screw would also be a flow-control component: the ball screw would be hollow so as to contain part of the main flow passage, and one end of the ball screw would be the main seating valve element. The relationships among the components of the valve are best understood by reference to the figure, which presents meridional cross sections of the valve in the fully closed and fully open positions. The motor would be supported by a bracket bolted to the valve body. By means of gears or pulleys and a timing belt, motor drive would be transmitted to a sleeve that would rotate on bearings in the valve body. A ball nut inside the sleeve would be made to rotate with the sleeve by use of a key. The ball screw would pass through and engage the ball nut. A key would prevent rotation of the ball screw in the valve body while allowing the ball screw to translate axially when driven by the ball nut. The outer surface of the ball screw would be threaded only in a mid-length region: the end regions of the outer surface of the ball screw would be polished so that they could act as dynamic sealing surfaces

  13. Microbial electricity generation via microfluidic flow control.

    PubMed

    Li, Zhiqiang; Zhang, Ying; LeDuc, Philip R; Gregory, Kelvin B

    2011-09-01

    Next generation battery technology is rapidly evolving to meet the demand for higher power densities and smaller footprints through novel catalysts and battery architecture. We present a µ-scale, biological fuel cell which utilizes microbial electricity generation enabled by microfluidic flow control to produce power. The new fuel cell, the smallest of its kind, with a total volume of 0.3 µL, produces scalable and controllable electrical energy from organic matter which is sustained through microbial respiration and laminar flow separation of the electrolytes. Electrical currents are dependent on specific biofilm formation on the anode, the concentration of electron donor, and a diffusion-limited flow regime. A maximum current density of 18.40 ± 3.48 mA m(-2) (92 ± 17 A m(-3)) was produced by Geobacter sulfurreducens, and 25.42 mA m(-2) (127 A m(-3)) by Shewanella oneidensis. The µ-scale biological fuel cell introduces the necessary small size and fuel flexibility for applications in vivo and in situ sensors which may be remotely deployed and self-powered.

  14. Flow-controlled magnetic particle manipulation

    SciTech Connect

    Grate, Jay W; Bruckner-Lea, Cynthia J; Holman, David A

    2011-02-22

    Inventive methods and apparatus are useful for collecting magnetic materials in one or more magnetic fields and resuspending the particles into a dispersion medium, and optionally repeating collection/resuspension one or more times in the same or a different medium, by controlling the direction and rate of fluid flow through a fluid flow path. The methods provide for contacting derivatized particles with test samples and reagents, removal of excess reagent, washing of magnetic material, and resuspension for analysis, among other uses. The methods are applicable to a wide variety of chemical and biological materials that are susceptible to magnetic labeling, including, for example, cells, viruses, oligonucleotides, proteins, hormones, receptor-ligand complexes, environmental contaminants and the like.

  15. Active Flow Control Strategies Using Surface Pressure Measurements

    NASA Technical Reports Server (NTRS)

    Kumar, Vikas; Alvi, Farrukh S.

    2010-01-01

    Evaluate the efficacy of Microjets Can we eliminate/minimize flow separation? Is the flow unsteadiness reduced? Guidelines for an active control Search for an appropriate sensor. Examine for means to develop a flow model for identifying the state of flow over the surface Guidelines toward future development of a Simple and Robust control methodology

  16. Active Flow Control Activities at NASA Langley

    NASA Technical Reports Server (NTRS)

    Anders, Scott G.; Sellers, William L., III; Washburn, Anthony E.

    2004-01-01

    NASA Langley continues to aggressively investigate the potential advantages of active flow control over more traditional aerodynamic techniques. This paper provides an update to a previous paper and describes both the progress in the various research areas and the significant changes in the NASA research programs. The goals of the topics presented are focused on advancing the state of knowledge and understanding of controllable fundamental mechanisms in fluids as well as to address engineering challenges. An organizational view of current research activities at NASA Langley in active flow control as supported by several projects is presented. On-center research as well as NASA Langley funded contracts and grants are discussed at a relatively high level. The products of this research are to be demonstrated either in bench-top experiments, wind-tunnel investigations, or in flight as part of the fundamental NASA R&D program and then transferred to more applied research programs within NASA, DOD, and U.S. industry.

  17. Standardization, Calibration, and Control in Flow Cytometry.

    PubMed

    Wang, Lili; Hoffman, Robert A

    2017-01-05

    Because flow cytometers are designed to measure particle characteristics, particles are the most common materials used to calibrate, control, and standardize the instruments. Definitions and cautions are provided for common terms to alert the reader to critical distinctions in meaning. This unit presents extensive background on particle types and cautions and describes practical aspects of methods to standardize and calibrate instruments. Procedures are provided to characterize performance in terms of optical alignment, fluorescence and light scatter resolution, and sensitivity. Finally, suggestions follow for analyzing particles used for calibration. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

  18. Design Considerations for Laminar Flow Control Aircraft

    NASA Technical Reports Server (NTRS)

    Sturgeon, R. F.; Bennett, J. A.

    1976-01-01

    A study was conducted to investigate major design considerations involved in the application of laminar flow control to the wings and empennage of long range subsonic transport aircraft compatible with initial operation in 1985. For commercial transports with a design mission range of 10,186 km (5500 n mil) and a payload of 200 passengers, parametric configuration analyses were conducted to evaluate the effect of aircraft performance, operational, and geometric parameters on fuel efficiency. Study results indicate that major design goals for aircraft optimization include maximization of aspect ratio and wing loading and minimization of wing sweep consistent with wing volume and airport performance requirements.

  19. Thermoregulatory control of finger blood flow

    NASA Technical Reports Server (NTRS)

    Wenger, C. B.; Roberts, M. F.; Nadel, E. R.; Stolwijk, J. A. J.

    1975-01-01

    In the present experiment, exercise was used to vary internal temperature and ambient air heat control was used to vary skin temperature. Finger temperature was fixed at about 35.7 C. Esophageal temperature was measured with a thermocouple at the level of the left atrium, and mean skin temperature was calculated from a weighted mean of thermocouple temperatures at different skin sites. Finger blood flow was measured by electrocapacitance plethysmography. An equation in these quantities is given which accounts for the data garnered.

  20. Thermoregulatory control of finger blood flow

    NASA Technical Reports Server (NTRS)

    Wenger, C. B.; Roberts, M. F.; Nadel, E. R.; Stolwijk, J. A. J.

    1975-01-01

    In the present experiment, exercise was used to vary internal temperature and ambient air heat control was used to vary skin temperature. Finger temperature was fixed at about 35.7 C. Esophageal temperature was measured with a thermocouple at the level of the left atrium, and mean skin temperature was calculated from a weighted mean of thermocouple temperatures at different skin sites. Finger blood flow was measured by electrocapacitance plethysmography. An equation in these quantities is given which accounts for the data garnered.

  1. Stratigraphic control of flow and transport characteristics.

    PubMed

    Edington, Dwaine; Poeter, Eileen

    2007-01-01

    Ground water flow and travel time are dependent on stratigraphic architecture, which is governed by competing processes that control the spatial and temporal distribution of accommodation and sediment supply. Accommodation is the amount of space in which sediment may accumulate as defined by the difference between the energy gradient and the topographic surface. The temporal and spatial distribution of accommodation is affected by processes that change the distribution of energy (e.g., sea level or subsidence). Fluvial stratigraphic units, generated by FLUVSIM (a stratigraphic simulator based on accommodation and sediment supply), with varying magnitudes and causes of accommodation, were incorporated into a hydraulic regime using MODFLOW (a ground water flow simulator), and particles were tracked using MODPATH (a particle-tracking algorithm). These experiments illustrate that the dominant type of accommodation process influences the degree of continuity of stratigraphic units and thus affects ground water flow and transport. When the hydraulic gradient is parallel to the axis of the fluvial system in the depositional environment, shorter travel times occur in low-total accommodation environments and longer travel times in high-total accommodation environments. Given the same total accommodation, travel times are longer when sea-level change is the dominant process than those in systems dominated by subsidence.

  2. Horizontal mantle flow controls subduction dynamics.

    PubMed

    Ficini, E; Dal Zilio, L; Doglioni, C; Gerya, T V

    2017-08-08

    It is generally accepted that subduction is driven by downgoing-plate negative buoyancy. Yet plate age -the main control on buoyancy- exhibits little correlation with most of the present-day subduction velocities and slab dips. "West"-directed subduction zones are on average steeper (~65°) than "East"-directed (~27°). Also, a "westerly"-directed net rotation of the lithosphere relative to the mantle has been detected in the hotspot reference frame. Thus, the existence of an "easterly"-directed horizontal mantle wind could explain this subduction asymmetry, favouring steepening or lifting of slab dip angles. Here we test this hypothesis using high-resolution two-dimensional numerical thermomechanical models of oceanic plate subduction interacting with a mantle flow. Results show that when subduction polarity is opposite to that of the mantle flow, the descending slab dips subvertically and the hinge retreats, thus leading to the development of a back-arc basin. In contrast, concordance between mantle flow and subduction polarity results in shallow dipping subduction, hinge advance and pronounced topography of the overriding plate, regardless of their age-dependent negative buoyancy. Our results are consistent with seismicity data and tomographic images of subduction zones. Thus, our models may explain why subduction asymmetry is a common feature of convergent margins on Earth.

  3. Distributed Power Flow Control: Distributed Power Flow Control using Smart Wires for Energy Routing

    SciTech Connect

    2012-04-24

    GENI Project: Smart Wire Grid is developing a solution for controlling power flow within the electric grid to better manage unused and overall transmission capacity. The 300,000 miles of high-voltage transmission line in the U.S. today are congested and inefficient, with only around 50% of all transmission capacity utilized at any given time. Increased consumer demand should be met in part with more efficient and an economical power flow. Smart Wire Grid’s devices clamp onto existing transmission lines and control the flow of power within—much like how internet routers help allocate bandwidth throughout the web. Smart wires could support greater use of renewable energy by providing more consistent control over how that energy is routed within the grid on a real-time basis. This would lessen the concerns surrounding the grid’s inability to effectively store intermittent energy from renewables for later use.

  4. Contribution to "AIAA Aerospace Year in Review" article

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Downey, J. Patton

    2012-01-01

    The NASA Marshall Space Flight Center Microgravity Science Program is dedicated to promoting our understanding of materials processing by conducting relevant experiments in the microgravity environment and supporting related modeling efforts with the intent of improving ground-based practices. Currently funded investigations include research on dopant distribution and defect formation in semiconductors, microstructural development and transitions in dendritic casting alloys, coarsening phenomena, competition between thermal and kinetic phase formation, and the formation of glassy vs. crystalline material. NASA Microgravity Materials Science Principle Investigators are selected for funding either through a proposal in response to a NASA Research Announcement or by collaborating on a team that has successfully proposed to a foreign space agency research announcement. In the latter case, a US investigator can then apply to NASA for funding through an unsolicited proposal. The International Space Station (ISS) facilities used for the experimental investigations are provided primarily by partnering with foreign agencies and often US investigators are working as a part of a larger team studying a specific area of materials science. Facilities for conducting experiments aboard the ISS include the European Space Agency (ESA) Low Gradient Facility (LGF) and the Solidification and Quench (SQF) modular inserts to the Materials Research Rack/Materials Science Laboratory and are primarily used for controlled solidification studies. The French Space Agency (CNES) provided DECLIC facility allows direct observation of morphological development in transparent materials that solidify analogously to metals. The ESA provided Electro ]Magnetic Levitator (EML) is designed to levitate, melt and then cool samples in order to determine material properties, study nucleation behavior, and document phase transitions. Finally, the Microgravity Science Glovebox (MSG) serves as a onboard

  5. Supersonic cavity flow control using plasma actuators

    NASA Astrophysics Data System (ADS)

    Webb, Nathan; Omari, Dennis; Samimy, Mo

    2015-11-01

    Flow over cavities with a length to depth ratio of order 1 undergo so called ``Rossiter'' resonance for certain combinations of free stream Mach number, upstream boundary layer characteristics, and cavity length. This is caused by the amplification of natural perturbations in the cavity shear layer by the Kelvin-Helmholtz instability. The amplified perturbations in the shear layer grow and roll up into large-scale structures, which interact with the trailing edge of the cavity. This interaction produces acoustic waves that travel upstream and further perturb the shear layer. If the timing/phase is correct, a feedback loop is formed. Artificial perturbations can be used to alter the resonance condition and thus the flow characteristics. In the past we used Localized Arc Filament Plasma Actuators (LAFPAs) to perturb the shear layer of a subsonic cavity and demonstrated significant control authority to suppress or excite resonance. This work seeks to examine control authority of the LAFPAs in the supersonic regime. Experiments conducted with a supersonic cavity demonstrated the LAFPAs retain the ability to suppress or excite resonance. The ability to either excite or suppress resonance, as needed, is required in some applications. Supported by AFRL.

  6. Access control mechanism of wireless gateway based on open flow

    NASA Astrophysics Data System (ADS)

    Peng, Rong; Ding, Lei

    2017-08-01

    In order to realize the access control of wireless gateway and improve the access control of wireless gateway devices, an access control mechanism of SDN architecture which is based on Open vSwitch is proposed. The mechanism utilizes the features of the controller--centralized control and programmable. Controller send access control flow table based on the business logic. Open vSwitch helps achieve a specific access control strategy based on the flow table.

  7. Summary of Propagation Cases of the Second AIAA Sonic Boom Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Rallabhandi, Sriram; Loubeau, Alexandra

    2017-01-01

    A summary is provided for the propagation portion of the second AIAA Sonic Boom Workshop held January 8, 2017 in conjunction with the AIAA SciTech 2017 conference. Near-field pressure waveforms for two cases were supplied and ground signatures at multiple azimuthal angles as well as their corresponding loudness metrics were requested from 10 participants, representing 3 countries. Each case had some required runs, as well as some optional runs. The required cases included atmospheric profiles with measured data including winds, using Radiosonde balloon data at multiple geographically spread locations, while the optional cases included temperature and pressure profiles from the US Standard atmosphere. The humidity profiles provided for the optional cases were taken from ANSI guidance, as the authors were unaware of an accepted standard at the time the cases were released to the participants. Participants provided ground signatures along with the requested data, including some loudness metrics using their best practices, which included lossy as well as lossless schemes. All the participants' submissions, for each case, are compared and discussed. Noise or loudness measures are calculated and detailed comparisons and statistical analyses are performed and presented. It has been observed that the variation in the loudness measures and spread between participants' submissions increased as the computation proceeded from under-track locations towards the lateral cut-off. Lessons learned during this workshop are discussed and recommendations are made for potential improvements and possible subsequent workshops as we collectively attempt to refine our analysis methods.

  8. Toward a laminar-flow-control transport

    NASA Technical Reports Server (NTRS)

    Sturgeon, R. F.

    1978-01-01

    Analyses were conducted to define a practical design for an advanced technology laminar flow control (LRC) transport for initial passenger operation in the early 1990's. Mission requirements, appropriate design criteria, and level of technology for the study aircraft were defined. The characteristics of the selected configuration were established, aircraft and LFC subsystems compatible with the mission requirements were defined, and the aircraft was evaluated in terms of fuel efficiency. A wing design integrating the LFC ducting and metering system into advanced composite wing structure was developed, manufacturing procedures for the surface panel design were established, and environmental and structural testing of surface panel components were conducted. Test results revealed a requirement for relatively minor changes in the manufacturing procedures employed, but have shown the general compatibility of both the selected design and the use of composite materials with the requirements of LFC wing surface panels.

  9. Laminar flow control SPF/08 feasibility demonstration

    NASA Technical Reports Server (NTRS)

    Ecklund, R. C.; Williams, N. R.

    1981-01-01

    The feasibility of applying superplastic forming/diffusion bonding (SPF/DB) technology to laminar flow control (LFC) system concepts was demonstrated. Procedures were developed to produce smooth, flat titanium panels, using thin -0.016 inch sheets, meeting LFC surface smoothness requirements. Two large panels 28 x 28 inches were fabricated as final demonstration articles. The first was flat on the top and bottom sides demonstrating the capability of the tooling and the forming and diffusion bonding procedures to produce flat, defect free surfaces. The second panel was configurated for LFC porous panel treatment by forming channels with dimpled projections on the top side. The projections were machined away leaving holes extending into the panel. A perforated titanium sheet was adhesively bonded over this surface to complete the LFC demonstration panel. The final surface was considered flat enough to meet LFC requirements for a jet transport aircraft in cruising flight.

  10. Synchronization trigger control system for flow visualization

    NASA Technical Reports Server (NTRS)

    Chun, K. S.

    1987-01-01

    The use of cinematography or holographic interferometry for dynamic flow visualization in an internal combustion engine requires a control device that globally synchronizes camera and light source timing at a predefined shaft encoder angle. The device is capable of 0.35 deg resolution for rotational speeds of up to 73 240 rpm. This was achieved by implementing the shaft encoder signal addressed look-up table (LUT) and appropriate latches. The developed digital signal processing technique achieves 25 nsec of high speed triggering angle detection by using direct parallel bit comparison of the shaft encoder digital code with a simulated angle reference code, instead of using angle value comparison which involves more complicated computation steps. In order to establish synchronization to an AC reference signal whose magnitude is variant with the rotating speed, a dynamic peak followup synchronization technique has been devised. This method scrutinizes the reference signal and provides the right timing within 40 nsec. Two application examples are described.

  11. Laminar flow control perforated wing panel development

    NASA Technical Reports Server (NTRS)

    Fischler, J. E.

    1986-01-01

    Many structural concepts for a wing leading edge laminar flow control hybrid panel were analytically investigated. After many small, medium, and large tests, the selected design was verified. New analytic methods were developed to combine porous titanium sheet bonded to a substructure of fiberglass and carbon/epoxy cloth. At -65 and +160 F test conditions, the critical bond of the porous titanium to the composite failed at lower than anticipated test loads. New cure cycles, design improvements, and test improvements significantly improved the strength and reduced the deflections from thermal and lateral loadings. The wave tolerance limits for turbulence were not exceeded. Consideration of the beam column midbay deflections from the combinations of the axial and lateral loadings and thermal bowing at -65 F, room temperature, and +160 F were included. Many lap shear tests were performed at several cure cycles. Results indicate that sufficient verification was obtained to fabricate a demonstration vehicle.

  12. Adjustable flow rate controller for polymer solutions

    DOEpatents

    Jackson, Kenneth M.

    1981-01-01

    An adjustable device for controlling the flow rate of polymer solutions which results in only little shearing of the polymer molecules, said device comprising an inlet manifold, an outlet manifold, a plurality of tubes capable of providing communication between said inlet and outlet manifolds, said tubes each having an internal diameter that is smaller than that of the inlet manifold and large enough to insure that viscosity of the polymer solution passing through each said tube will not be reduced more than about 25 percent, and a valve associated with each tube, said valve being capable of opening or closing communication in that tube between the inlet and outlet manifolds, each said valve when fully open having a diameter that is substantially at least as great as that of the tube with which it is associated.

  13. Jet vortex generators for turbulent flow separation control

    NASA Technical Reports Server (NTRS)

    Selby, G.; Lin, J.; Howard, F.

    1990-01-01

    A parametric study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow separation control can be accomplished with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).

  14. Jet vortex generators for turbulent flow separation control

    NASA Technical Reports Server (NTRS)

    Selby, Gregory; Lin, J.; Howard, F.

    1990-01-01

    A parametric study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low speed turbulent flow over a two dimensional rearward-facing ramp. Results indicate that flow separation control can be accomplished with the level of control achieved being a function of jet speed, jet orientation (with respect to the free stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).

  15. Dissipative control of energy flow in interconnected systems

    NASA Technical Reports Server (NTRS)

    Kishimoto, Y.; Bernstein, D. S.; Hall, S. R.

    1993-01-01

    Dissipative energy flow controllers are designed for interconnected modal subsystems. Active feedback controllers for vibration suppression are then viewed as either an additional subsystem or a dissipative coupling. These controllers, which are designed by the LQG positive real control approach, maximize energy flow from a specified modal subsystem.

  16. Control performance standards based load-frequency controller considering redox flow batteries coordinate with interline power flow controller

    NASA Astrophysics Data System (ADS)

    Chidambaram, I. A.; Paramasivam, B.

    2012-12-01

    This paper proposes a sophisticate application of redox flow batteries (RFB) coordinate with Interline Power Flow Controller (IPFC) for the improvement of Load Frequency Control (LFC) of a multiple units two- area power system. The Interline Power Flow Controller is to stabilize the frequency oscillations of the inter-area mode in the interconnected power system by the dynamic control of tie-line power flow. The redox flow batteries, which are not aged to the frequent charging and discharging, have a quick response and outstanding function during overload conditions. In addition to leveling load, the battery is advantageous for secondary control in the power system and maintenance of power quality of distributes power resources. The Bacterial Foraging Optimization (BFO) algorithm is use to optimize the parameters of the cost functions for designing the integral controller. Compliance with North American Electric Reliability Council (NERC) standards for Load Frequency Control has also been establishes in this work. Simulation studies reveal that the RFB coordinate with IPFC units has greater potential for improving the system dynamic performance.

  17. Sensor Development for Active Flow Control

    NASA Technical Reports Server (NTRS)

    Kahng, Seun K.; Gorton, Susan A.; Mau, Johnney C.; Soto, Hector L.; Hernandez, Corey D.

    2001-01-01

    Presented are the developmental efforts for MEMS sensors for a closed-loop active flow control in a low-speed wind tunnel evaluation. The MEMS sensors are designed in-house and fabricated out of house, and the shear sensors are a thermal type that are collocated with temperature and pressure sensors on a flexible polyimide sheet, which conforms to surfaces of a simple curvature. A total of 6 sensors are located within a 1.5 by 3 mm area as a cluster with each sensor being 300 pm square. The thickness of this sensor cluster is 75 pm. Outputs from the shear sensors have been compared with respect to those of the Preston tube for evaluation of the sensors on a flat plate. Pressure sensors are the absolute type and have recorded pressure measurements within 0.05 percent of the tunnel ESP pressure sensor readings. The sensors and signal conditioning electronics have been tested on both a flat plate and a ramp in Langley s 15-Inch Low-Turbulence Tunnel. The system configuration and control PC is configured with LabView, where calibration constants are stored for desired compensation and correction. The preliminary test results are presented within.

  18. Insect vision: controlling actions through optic flow.

    PubMed

    Collett, Thomas S

    2002-09-17

    Insects depend upon optic flow to supply much of their information about the three-dimensional structure of the world. Many insects use translational flow to measure the distance of objects from themselves. A recent study has provided new insights into the way Drosophila use optic flow to pick out a close target to approach.

  19. Self-regulating flow control device

    DOEpatents

    Humphreys, Duane A.

    1984-01-01

    A variable, self-regulating valve having a hydraulic loss coefficient proportional to a positive exponential power of the flow rate. The device includes two objects in a flow channel and structure which assures that the distance between the two objects is an increasing function of the flow rate. The range of spacing between the objects is such that the hydraulic resistance of the valve is an increasing function of the distance between the two objects so that the desired hydraulic loss coefficient as a function of flow rate is obtained without variation in the flow area.

  20. Flow Control Device Evaluation for an Internal Flow with an Adverse Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Jenkins, Luther N.; Gorton, Susan Althoff; Anders, Scott G.

    2002-01-01

    The effectiveness of several active and passive devices to control flow in an adverse pressure gradient with secondary flows present was evaluated in the 15 Inch Low Speed Tunnel at NASA Langley Research Center. In this study, passive micro vortex generators, micro bumps, and piezoelectric synthetic jets were evaluated for their flow control characteristics using surface static pressures, flow visualization, and 3D Stereo Digital Particle Image Velocimetry. Data also were acquired for synthetic jet actuators in a zero flow environment. It was found that the micro vortex generator is very effective in controlling the flow environment for an adverse pressure gradient, even in the presence of secondary vortical flow. The mechanism by which the control is effected is a re-energization of the boundary layer through flow mixing. The piezoelectric synthetic jet actuators must have sufficient velocity output to produce strong longitudinal vortices if they are to be effective for flow control. The output of these devices in a laboratory or zero flow environment will be different than the output in a flow environment. In this investigation, the output was higher in the flow environment, but the stroke cycle in the flow did not indicate a positive inflow into the synthetic jet.

  1. Synthetic Capillaries to Control Microscopic Blood Flow

    PubMed Central

    Sarveswaran, K.; Kurz, V.; Dong, Z.; Tanaka, T.; Penny, S.; Timp, G.

    2016-01-01

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using “live cell lithography”(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision—no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100–1000 cells, organized hierarchically to express a predictable function. PMID:26905751

  2. Synthetic Capillaries to Control Microscopic Blood Flow

    NASA Astrophysics Data System (ADS)

    Sarveswaran, K.; Kurz, V.; Dong, Z.; Tanaka, T.; Penny, S.; Timp, G.

    2016-02-01

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using “live cell lithography”(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision—no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100-1000 cells, organized hierarchically to express a predictable function.

  3. Synthetic Capillaries to Control Microscopic Blood Flow.

    PubMed

    Sarveswaran, K; Kurz, V; Dong, Z; Tanaka, T; Penny, S; Timp, G

    2016-02-24

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using "live cell lithography"(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision-no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100-1000 cells, organized hierarchically to express a predictable function.

  4. Review of hybrid laminar flow control systems

    NASA Astrophysics Data System (ADS)

    Krishnan, K. S. G.; Bertram, O.; Seibel, O.

    2017-08-01

    The aeronautic community always strived for fuel efficient aircraft and presently, the need for ecofriendly aircraft is even more, especially with the tremendous growth of air traffic and growing environmental concerns. Some of the important drivers for such interests include high fuel prices, less emissions requirements, need for more environment friendly aircraft to lessen the global warming effects. Hybrid laminar flow control (HLFC) technology is promising and offers possibility to achieve these goals. This technology was researched for decades for its application in transport aircraft, and it has achieved a new level of maturity towards integration and safety and maintenance aspects. This paper aims to give an overview of HLFC systems research and associated flight tests in the past years both in the US and in Europe. The review makes it possible to distinguish between the successful approaches and the less successful or outdated approaches in HLFC research. Furthermore, the technology status shall try to produce first estimations regarding the mass, power consumption and performance of HLFC systems as well as estimations regarding maintenance requirements and possible subsystem definitions.

  5. SparkJet Actuators for Flow Control

    DTIC Science & Technology

    2007-03-01

    DISTRIBUTION I AVAILABILITY STATEMENT Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Effective manipulation of a flow field can lead to a number of significant...demonstrated the ability to produce a synthetic jet with high exhaust velocities, and hence holds the promise of manipulating high-speed flows without...for advanced high-speed flight vehicles. Effective manipulation of a flow field can lead to a number of significant benefits to aerospace vehicle

  6. Input/Output operations for hybrid data-flow/control-flow systems

    SciTech Connect

    Evripidou, P.; Gaudiot, J.L.

    1991-12-31

    Hybrid data-flow/control-flow system combine the advantages of the data-flow model: functionality and tolerance to communication and memory latencies with the efficient instruction scheduling of the control-flow model. The absence of global state in such hybrid multiprocessors and multiprocessors in general renders the implementation of state tasks such as Input/Output operations very difficult to implement. A distributed file-pointer scheme for incorporations I/O operations onto the data-flow model has been developed. A dependency detection algorithm detects and classify cases of potential access conflicts. A conflict resolution data-flow graph is then created which at execution time safely distributes file-pointers to the I/O actors. This scheme has also been implemented on a hybrid a data-flow control-flow multiprocessor: the Decoupled Data-Driven Multiprocessor with Variable Resolution Actors.

  7. Switch Box For Controlling Flows Of Four Gases

    NASA Technical Reports Server (NTRS)

    Wishard, James R.; Lamb, James L.

    1995-01-01

    Switch box designed for use in simultaneously controlling flows of as many as four out of total of six available gases into semiconductor-processing chamber. Contains switches, relays, logic circuitry, display devices, and other circuitry for connecting each of as many as four gas controllers to any one of as many as six available mass-flow controllers. Front panel of switch box apprises technician of statuses of flows of various gases.

  8. Statistical Analysis of CFD Solutions from the Fourth AIAA Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.

    2010-01-01

    A graphical framework is used for statistical analysis of the results from an extensive N-version test of a collection of Reynolds-averaged Navier-Stokes computational fluid dynamics codes. The solutions were obtained by code developers and users from the U.S., Europe, Asia, and Russia using a variety of grid systems and turbulence models for the June 2009 4th Drag Prediction Workshop sponsored by the AIAA Applied Aerodynamics Technical Committee. The aerodynamic configuration for this workshop was a new subsonic transport model, the Common Research Model, designed using a modern approach for the wing and included a horizontal tail. The fourth workshop focused on the prediction of both absolute and incremental drag levels for wing-body and wing-body-horizontal tail configurations. This work continues the statistical analysis begun in the earlier workshops and compares the results from the grid convergence study of the most recent workshop with earlier workshops using the statistical framework.

  9. Summary of the First AIAA CFD High Lift Prediction Workshop (invited)

    NASA Technical Reports Server (NTRS)

    Rumsey, C. L.; Long, M.; Stuever, R. A.; Wayman, T. R.

    2011-01-01

    The 1st AIAA CFD High Lift Prediction Workshop was held in Chicago in June 2010. The goals of the workshop included an assessment of the numerical prediction capability of current-generation CFD technology/ codes for swept, medium/high-aspect ratio wings in landing/take-off (high lift) configurations. 21 participants from 8 countries and 18 organizations, submitted a total of 39 datasets of CFD results. A variety of grid systems (both structured and unstructured) were used. Trends due to flap angle were analyzed, and effects of grid family, grid density, solver, and turbulence model were addressed. Some participants also assessed the effects of support brackets used to attach the flap and slat to the main wing. This invited paper describes the combined results from all workshop participants. Comparisons with experimental data are made. A statistical summary of the CFD results is also included.

  10. Statistical Analysis of CFD Solutions From the Fifth AIAA Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.

    2013-01-01

    A graphical framework is used for statistical analysis of the results from an extensive N-version test of a collection of Reynolds-averaged Navier-Stokes computational fluid dynamics codes. The solutions were obtained by code developers and users from North America, Europe, Asia, and South America using a common grid sequence and multiple turbulence models for the June 2012 fifth Drag Prediction Workshop sponsored by the AIAA Applied Aerodynamics Technical Committee. The aerodynamic configuration for this workshop was the Common Research Model subsonic transport wing-body previously used for the 4th Drag Prediction Workshop. This work continues the statistical analysis begun in the earlier workshops and compares the results from the grid convergence study of the most recent workshop with previous workshops.

  11. CFL3D Contribution to the AIAA Supersonic Shock Boundary Layer Interaction Workshop

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.

    2010-01-01

    This paper documents the CFL3D contribution to the AIAA Supersonic Shock Boundary Layer Interaction Workshop, held in Orlando, Florida in January 2010. CFL3D is a Reynolds-averaged Navier-Stokes code. Four shock boundary layer interaction cases are computed using a one-equation turbulence model widely used for other aerodynamic problems of interest. Two of the cases have experimental data available at the workshop, and two of the cases do not. The effect of grid, flux scheme, and thin-layer approximation are investigated. Comparisons are made to the available experimental data. All four cases exhibit strong three-dimensional behavior in and near the interaction regions, resulting from influences of the tunnel side-walls.

  12. An approach to versatile highly-uniform MOVPE growth: the flow controlled stagnation point flow reactor

    NASA Astrophysics Data System (ADS)

    Kondo, Makoto; Kuramata, Akito; Fujii, Takuya; Anayama, Chikashi; Okazaki, Jiro; Sekiguchi, Hiroshi; Tanahashi, Toshiyuki; Yamazaki, Susumu; Nakajima, Kazuo

    1992-11-01

    We present an approach to versatile highly-uniform MOVPE growth using the controlled stagnation point flow reactor. Our approach for uniform growth involves two concepts: (1) realizing the stagnation point flow condition in a vertical reactor configuration and (2) introducing a method for versatile flow-field control using the flow-controlled multiple gas-injector technique. The versatility of the flow-control technique was investigated by evaluating how radial deposition rate uniformity is affected by variation in several hydrodynamic and reactor configuration factors: the inlet flow rate, operating pressure, susceptor temperature, susceptor rotation speed, and the inlet and susceptor separation. We confirmed that a spatially uniform deposition rate can be obtained over a wide range of hydrodynamic and configuration parameters, demonstrating that the flow-control technique can provide a stable stagnation point flow field. Even when the ideal stagnation point flow-field is disturbed, for example, by high temperature susceptor heating, it could be completely compensated by adjusting the flow rate ratio for multiple injectors, showing our technique's ability to control flow-fields. By using this technique, we obtained excellent uniformities in both layer thickness and alloy composition for two important materials - GaInAsP and AlGaInP - in the same reactor.

  13. Unified power flow controller: Modeling, stability analysis, control strategy and control system design

    NASA Astrophysics Data System (ADS)

    Sreenivasachar, Kannan

    2001-07-01

    Unified power flow controller (UPFC) has been the most versatile Flexible AC Transmission System (FACTS) device due to its ability to control real and reactive power flow on transmission lines while controlling the voltage of the bus to which it is connected. UPFC being a multi-variable power system controller it is necessary to analyze its effect on power system operation. To study the performance of the UPFC in damping power oscillations using PSCAD-EMTDC software, a de-coupled control system has been designed for the shunt inverter to control the UPFC bus voltage and the DC link capacitor voltage. The series inverter of a UPFC controls the real power flow in the transmission line. One problem associated with using a high gain PI controller (used to achieve fast control of transmission line real power flow) for the series inverter of a UPFC to control the real power flow in a transmission line is the presence of low damping. This problem is solved in this research by using a fuzzy controller. A method to model a fuzzy controller in PSCAD-EMTDC software has also been described. Further, in order to facilitate proper operation between the series and the shunt inverter control system, a new real power coordination controller has been developed and its performance was evaluated. The other problem concerning the operation of a UPFC is with respect to transmission line reactive power flow control. Step changes to transmission line reactive power references have significant impact on the UPFC bus voltage. To reduce the adverse effect of step changes in transmission line reactive power references on the UPFC bus voltage, a new reactive power coordination controller has been designed. Transient response studies have been conducted using PSCAD-EMTDC software to show the improvement in power oscillation damping with UPFC. These simulations include the real and reactive power coordination controllers. Finally, a new control strategy has been proposed for UPFC. In this

  14. Boundary-layer-ingesting inlet flow control system

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R. (Inventor); Allan, Brian G. (Inventor)

    2010-01-01

    A system for reducing distortion at the aerodynamic interface plane of a boundary-layer-ingesting inlet using a combination of active and passive flow control devices is disclosed. Active flow control jets and vortex generating vanes are used in combination to reduce distortion across a range of inlet operating conditions. Together, the vortex generating vanes can reduce most of the inlet distortion and the active flow control jets can be used at a significantly reduced control jet mass flow rate to make sure the inlet distortion stays low as the inlet mass flow rate varies. Overall inlet distortion, measured and described as average SAE circumferential distortion descriptor, was maintained at a value of 0.02 or less. Advantageous arrangements and orientations of the active flow control jets and the vortex generating vanes were developed using computational fluid dynamics simulations and wind tunnel experimentations.

  15. Control of turbulent mixing in hypersonic flow

    NASA Astrophysics Data System (ADS)

    Nishioka, Michio

    1990-10-01

    The conventional engines for present supersonic aircrafts have a drawback in the subsonic flights: they generate strong shock waves, increase total pressure losses, dissociate gases due to increased temperature, and substantially decrease fuel burning efficiencies. When the gases are burned in the supersonic flow, duration times of gases in the combustion chamber become too short. The development of a new technology is required to mix rapidly fuel (hydrogen) and oxygen in the supersonic flow and burn them in time. Flow instability of the initial turbulent flow structure in the hypersonic shear layer is simulated as fuel injection, and the after flow (Mach number of 2.5) is analyzed using the linear stability theory and is studied on the amplified disturbances. The growth of this supersonic disturbance is observed using the Schlieren method. The method for additional mixing of gases is studied to accelerate disturbances.

  16. Light-controlled flows in active fluids

    NASA Astrophysics Data System (ADS)

    Dervaux, Julien; Capellazzi Resta, Marina; Brunet, Philippe

    2017-03-01

    Many photosynthetic microorganisms are able to detect light and move towards optimal intensities. This ability, known as phototaxis, plays a major role in ecology by affecting natural phytoplankton mass transfers, and has important applications in bioreactor and artificial micro-swimmers technologies. Here we show that this property can be exploited to generate macroscopic fluid flows using a localized light source directed towards shallow suspensions of phototactic microorganisms. Within the intensity range of positive phototaxis, algae accumulate beneath the excitation light, where collective effects lead to the emergence of radially symmetric convective flows. These flows can thus be used as hydrodynamic tweezers to manipulate small floating objects. At high cell density and layer depth, we uncover a new kind of instability, wherein the viscous torque exerted by self-generated fluid flows on the swimmers induces the formation of travelling waves. A model coupling fluid flow, cell concentration and orientation finely reproduces the experimental data.

  17. Advanced stability analysis for laminar flow control

    NASA Technical Reports Server (NTRS)

    Orszag, S. A.

    1981-01-01

    Five classes of problems are addressed: (1) the extension of the SALLY stability analysis code to the full eighth order compressible stability equations for three dimensional boundary layer; (2) a comparison of methods for prediction of transition using SALLY for incompressible flows; (3) a study of instability and transition in rotating disk flows in which the effects of Coriolis forces and streamline curvature are included; (4) a new linear three dimensional instability mechanism that predicts Reynolds numbers for transition to turbulence in planar shear flows in good agreement with experiment; and (5) a study of the stability of finite amplitude disturbances in axisymmetric pipe flow showing the stability of this flow to all nonlinear axisymmetric disturbances.

  18. Topographic Controls on Landslide and Debris-Flow Mobility

    NASA Astrophysics Data System (ADS)

    McCoy, S. W.; Pettitt, S.

    2014-12-01

    Regardless of whether a granular flow initiates from failure and liquefaction of a shallow landslide or from overland flow that entrains sediment to form a debris flow, the resulting flow poses hazards to downslope communities. Understanding controls on granular-flow mobility is critical for accurate hazard prediction. The topographic form of granular-flow paths can vary significantly across different steeplands and is one of the few flow-path properties that can be readily altered by engineered control structures such as closed-type check dams. We use grain-scale numerical modeling (discrete element method simulations) of free-surface, gravity-driven granular flows to investigate how different topographic profiles with the same mean slope and total relief can produce notable differences in flow mobility due to strong nonlinearities inherent to granular-flow dynamics. We describe how varying the profile shape from planar, to convex up, to concave up, as well how varying the number, size, and location of check dams along a flow path, changes flow velocity, thickness, discharge, energy dissipation, impact force and runout distance. Our preliminary results highlight an important path dependence for this nonlinear system, show that caution should be used when predicting flow dynamics from path-averaged properties, and provide some mechanics-based guidance for engineering control structures.

  19. Thaw flow control for liquid heat transport systems

    DOEpatents

    Kirpich, Aaron S.

    1989-01-01

    In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.

  20. The art and science of flow control - case studies using flow visualization methods

    NASA Astrophysics Data System (ADS)

    Alvi, F. S.; Cattafesta, L. N., III

    2010-04-01

    Active flow control (AFC) has been the focus of significant research in the last decade. This is mainly due to the potentially substantial benefits it affords. AFC applications range from the subsonic to the supersonic (and beyond) regime for both internal and external flows. These applications are wide and varied, such as controlling flow transition and separation over various external components of the aircraft to active management of separation and flow distortion in engine components and over turbine and compressor blades. High-speed AFC applications include control of flow oscillations in cavity flows, supersonic jet screech, impinging jets, and jet-noise control. In this paper we review some of our recent applications of AFC through a number of case studies that illustrate the typical benefits as well as limitations of present AFC methods. The case studies include subsonic and supersonic canonical flowfields such as separation control over airfoils, control of supersonic cavity flows and impinging jets. In addition, properties of zero-net mass-flux (ZNMF) actuators are also discussed as they represent one of the most widely studied actuators used for AFC. In keeping with the theme of this special issue, the flowfield properties and their response to actuation are examined through the use of various qualitative and quantitative flow visualization methods, such as smoke, shadowgraph, schlieren, planar-laser scattering, and Particle image velocimetry (PIV). The results presented here clearly illustrate the merits of using flow visualization to gain significant insight into the flow and its response to AFC.

  1. Development of Advanced Casing Treatments for Flow Control

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Tsung, Fu-Lin

    2001-01-01

    Under the Base R&T and Ultra Efficient Engine Technology programs, the NASA-Goddard Space Flight Center Compressor Branch is investigating flow control strategies required to increase the loading and efficiency of core compressors while maintaining current levels of operability. Flow-control strategies being studied include advanced casing treatments, wall jet injection, and blade-tip injection for compressor stability enhancement, directed jets for surface boundary layer control, and vortex-generating devices. The use of computational fluid dynamics (CFD) simulations to assess the effectiveness of flow-control devices and to guide their design is a key element in this research. CFD simulations serve to screen potential flow-control concepts at a lower cost than executing physical experiments in turbomachinery facilities. CFD simulations also provide guidance in designing physical experiments for those flow control concepts, which appear promising.

  2. Insect behaviour: controlling flight altitude with optic flow.

    PubMed

    Webb, Barbara

    2007-02-20

    Insects can smoothly control their height while flying by adjusting lift to maintain a set-point in the ventral optic flow. The efficacy of this simple flight-control mechanism has been demonstrated using a robot helicopter.

  3. A Novel Approach to Adaptive Flow Separation Control

    DTIC Science & Technology

    2016-09-03

    net prediction signal (dotted curve) to adjust to match the measured signal (solid curve) even when the flow conditions change. SBMPC is then...A second series of PIV measurements of the same duration was collected to characterize the controlled flow . Contours of streamwise velocity V_x are...SECURITY CLASSIFICATION OF: Due to their practical import, flow control problems have attracted increasing attention. This research specifically

  4. Pressurized tundish for controlling a continuous flow of molten metal

    DOEpatents

    Lewis, T.W.; Hamill, P.E. Jr.; Ozgu, M.R.; Padfield, R.C.; Rego, D.N.; Brita, G.P.

    1990-07-24

    A pressurized tundish for controlling a continuous flow of molten metal is characterized by having a pair of principal compartments, one being essentially unpressurized and receiving molten metal introduced thereto, and the other being adapted for maintaining a controlled gaseous pressure over the surface of the fluid metal therein, whereby, by controlling the pressure within the pressurized chamber, metal exiting from the tundish is made to flow continually and at a controlled rate. 1 fig.

  5. Pressurized tundish for controlling a continuous flow of molten metal

    DOEpatents

    Lewis, Thomas W.; Hamill, Jr., Paul E.; Ozgu, Mustafa R.; Padfield, Ralph C.; Rego, Donovan N.; Brita, Guido P.

    1990-01-01

    A pressurized tundish for controlling a continous flow of molten metal characterized by having a pair of principal compartments, one being essentially unpressurized and receiving molten metal introduced thereto, and the other being adapted for maintaining a controlled gaseous pressure over the surface of the fluid metal therein, whereby, by controlling the pressure within the pressurized chamber, metal exiting from the tundish is made to flow continually and at a controlled rate.

  6. Characterizing cryogenic propellant flow behavior through a cavitating venturi in comparison to alternative flow control mechanisms

    NASA Astrophysics Data System (ADS)

    Ingle, Marjorie Adele

    The work detailed is an investigation of the use of a cavitating venturi as both a flow control and metering device. This was achieved through the combination of actual experimentation and numerical modeling of the fluid behavior of both liquid water and liquid methane as it passes through the test article designed, developed, and validated here within this study. The discharge coefficient of the cavitating venturi was determined through weigh flow calibration testing to determine an average mass flow rate. Turbine flow meter flow rate readings were used as a point of comparison and the discharge coefficient was computed. The discharge coefficient was then implemented into the Bernoulli Equation along with experimental pressure and temperature data to again calculate mass flow rate through the cavitating venturi. The agreement of the venturi flow rate data to that of the turbine flow meter effectively established its applicability as a passive flow control and metering feature. A preliminary CFD cavitation model was developed and validated for cavitating water flow regimes using ANSYS FLUENT. Agreement between mass flow rates obtained from the model to experimental data for cavitating water flow indicates that deviations in results for liquid methane analysis from experimental results could simply be the result of insufficiently defined fluid characteristics in the ANSYS FLUENT materials database. SEM surface roughness analysis of a secondary test article indicated that the default average surface roughness for steel in ANSYS FLUENT was reasonable. In addition, the methodology could be further applied to future duty life studies for the cavitating venturi flow meter.

  7. MAG-GATE System for Molten metal Flow Control

    SciTech Connect

    Richard D. Nathenson, P.E.

    2004-05-15

    The need for improved active flow control has been recognized as part of the Steel Industry Technology Roadmap. Under TRP 9808 for the American Iron and Steel Institute and the Department of Energy, Concept Engineering Group Inc. has developed MAG-GATE{trademark}, an electromagnetic system for active molten metal flow control. Two hot steel tests were successfully conducted in 2003 at the Whemco Foundry Division, Midland, PA. Approximately 110,000 pounds of 0.2% carbon steel were poured through the device subject to electromagnetic flow control. Excellent agreement between predicted and actual flow control was found. A survey of the molten metal flow control practices at 100 continuous casters in North America was also conducted in 2003. This report summarizes the results of the development program to date. Preliminary designs are described for the next step of a beta test at an operating billet/bloom or slab caster.

  8. Active control of Boundary Layer Separation & Flow Distortion in Adverse Pressure Gradient Flows via Supersonic Microjets

    NASA Technical Reports Server (NTRS)

    Alvi, Farrukh S.; Gorton, Susan (Technical Monitor)

    2005-01-01

    Inlets to aircraft propulsion systems must supply flow to the compressor with minimal pressure loss, flow distortion or unsteadiness. Flow separation in internal flows such as inlets and ducts in aircraft propulsion systems and external flows such as over aircraft wings, is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control this flow separation. In particular, the use of supersonic microjets as a means of controlling boundary layer separation was explored. The geometry used for the early part of this study was a simple diverging Stratford ramp, equipped with arrays of supersonic microjets. Initial results, based on the mean surface pressure distribution, surface flow visualization and Planar Laser Scattering (PLS) indicated a reverse flow region. We implemented supersonic microjets to control this separation and flow visualization results appeared to suggest that microjets have a favorable effect, at least to a certain extent. However, the details of the separated flow field were difficult to determine based on surface pressure distribution, surface flow patterns and PLS alone. It was also difficult to clearly determine the exact influence of the supersonic microjets on this flow. In the latter part of this study, the properties of this flow-field and the effect of supersonic microjets on its behavior were investigated in further detail using 2-component (planar) Particle Image Velocimetry (PIV). The results clearly show that the activation of microjets eliminated flow separation and resulted in a significant increase in the momentum of the fluid near the ramp surface. Also notable is the fact that the gain in momentum due to the elimination of flow separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very

  9. The study of multiphase flow control during odor reproduction

    NASA Astrophysics Data System (ADS)

    Luo, Dehan; Yu, Hao; Fan, Danjun; He, Meiqiu

    2014-04-01

    Odor reproduction, is the use of the chemical composition of the basic components of odor recipe, according to a certain proportion, to control the flow of the various components, which make them sufficiently blended to achieve reproduction. In this paper, reproducing method is to find the corresponding liquid flavor, and then based on chemical flavor recipes, using flowmeters to control the chemical composition of the liquid flavor ratio. In the proportional control, the liquid chemical composition is very likely to be volatile, so that the proportional control is multiphase flow control. Measurement of the flow control will directly affect the odor reproducible results. Using electronic nose to obtain reproducible odor data, and then use pattern recognition algorithm to determine reproducible results. The experimental results can be achieved on the process of odor components multiphase flow proportional control parameter adjustment.

  10. Stability of Flow around a Cylinder in Plane Poiseuille Flow

    NASA Astrophysics Data System (ADS)

    Dou, Hua-Shu; Ben, An-Qing; Fluid Mechanics Research Team

    2013-11-01

    Simulation of Navier-Stokes equations is carried out to study the stability of flow around a cylinder in plane Poiseuille flow. The energy gradient method is employed to analyze the mechanism of instability of cylinder wake. The ratio of the channel width to the cylinder diameter is 30, and the Reynolds number based on the cylinder diameter and incoming centerline velocity is 26 and 100, respectively. The incoming flow is given as being laminar. It is found that the instability of the cylinder wake, starting near the front stagnation point upstream. The recirculation zone behind the cylinder has no effect on the stability of the wake. In the wake behind the recirculation zone, the flow stability is controlled by the energy gradient in the shear layer along the two sides of the wake. At high Re, the energy gradient of averaged flow in the channel interacts with the wake vortex, strengthening the wake vortex structure. Due to the large ratio of the channel width to the cylinder diameter, the disturbance caused by the cylinder mainly occurs in the vicinity of the centerline and has little effect on the flow near the wall. The velocity profile on the two sides of the cylinder wake in the downstream channel remains laminar (parabolic profile). Professor in Fluid Mechanics; AIAA Associate Fellow.

  11. Measurement and control of pressure driven flows in microfluidic devices using an optofluidic flow sensor.

    PubMed

    Cheri, Mohammad Sadegh; Shahraki, Hamidreza; Sadeghi, Jalal; Moghaddam, Mohammadreza Salehi; Latifi, Hamid

    2014-09-01

    Measurement and control of pressure-driven flow (PDF) has a great potential to enhance the performance of chemical and biological experiments in Lab on a Chip technology. In this paper, we present an optofluidic flow sensor for real-time measurement and control of PDF. The optofluidic flow sensor consists of an on-chip micro Venturi and two optical Fabry-Pérot (FP) interferometers. Flow rate was measured from the fringe shift of FP interferometers resulted from movement fluid in the on-chip micro Venturi. The experimental results show that the optofluidic flow sensor has a minimum detectable flow change of 5 nl/min that is suitable for real time monitoring and control of fluids in many chemical and biological experiments. A Finite Element Method is used to solve the three dimensional (3D) Navier-Stokes and continuity equations to validate the experimental results.

  12. Measurement and control of pressure driven flows in microfluidic devices using an optofluidic flow sensor

    PubMed Central

    Cheri, Mohammad Sadegh; Shahraki, Hamidreza; Sadeghi, Jalal; Moghaddam, Mohammadreza Salehi; Latifi, Hamid

    2014-01-01

    Measurement and control of pressure-driven flow (PDF) has a great potential to enhance the performance of chemical and biological experiments in Lab on a Chip technology. In this paper, we present an optofluidic flow sensor for real-time measurement and control of PDF. The optofluidic flow sensor consists of an on-chip micro Venturi and two optical Fabry-Pérot (FP) interferometers. Flow rate was measured from the fringe shift of FP interferometers resulted from movement fluid in the on-chip micro Venturi. The experimental results show that the optofluidic flow sensor has a minimum detectable flow change of 5 nl/min that is suitable for real time monitoring and control of fluids in many chemical and biological experiments. A Finite Element Method is used to solve the three dimensional (3D) Navier–Stokes and continuity equations to validate the experimental results. PMID:25584118

  13. Dynamic-Active Flow Control - Phase I

    DTIC Science & Technology

    2006-10-18

    Section, 4: Plenum Chamber, 5: Rear Observation Window, 6: Return Pipework , 7: Filtration Isolation Valve, 8: AC Motor and Centrifugal Pump, 10: Return... Pipework (pressure side), 11: Filtration Circuit. A large settling chamber existed upstream of the test section. The pump flow was introduced

  14. ISS Payload Racks Automated Flow Control Calibration Method

    NASA Technical Reports Server (NTRS)

    Simmonds, Boris G.

    2003-01-01

    Payload Racks utilize MTL and/or LTL station water for cooling of payloads and avionics. Flow control range from valves of fully closed, to up to 300 Ibmhr. Instrument accuracies are as high as f 7.5 Ibm/hr for flow sensors and f 3 Ibm/hr for valve controller, for a total system accuracy of f 10.5 Ibm/hr. Improved methodology was developed, tested and proven that reduces accuracy of the commanded flows to less than f 1 Ibmhr. Uethodology could be packed in a "calibration kit" for on- orbit flow sensor checkout and recalibration, extending the rack operations before return to earth. -

  15. Numerical Simulation of Fluidic Actuators for Flow Control Applications

    NASA Technical Reports Server (NTRS)

    Vasta, Veer N.; Koklu, Mehti; Wygnanski, Israel L.; Fares, Ehab

    2012-01-01

    Active flow control technology is finding increasing use in aerospace applications to control flow separation and improve aerodynamic performance. In this paper we examine the characteristics of a class of fluidic actuators that are being considered for active flow control applications for a variety of practical problems. Based on recent experimental work, such actuators have been found to be more efficient for controlling flow separation in terms of mass flow requirements compared to constant blowing and suction or even synthetic jet actuators. The fluidic actuators produce spanwise oscillating jets, and therefore are also known as sweeping jets. The frequency and spanwise sweeping extent depend on the geometric parameters and mass flow rate entering the actuators through the inlet section. The flow physics associated with these actuators is quite complex and not fully understood at this time. The unsteady flow generated by such actuators is simulated using the lattice Boltzmann based solver PowerFLOW R . Computed mean and standard deviation of velocity profiles generated by a family of fluidic actuators in quiescent air are compared with experimental data. Simulated results replicate the experimentally observed trends with parametric variation of geometry and inflow conditions.

  16. Control of flow through a vapor generator

    DOEpatents

    Radcliff, Thomas D.

    2005-11-08

    In a Rankine cycle system wherein a vapor generator receives heat from exhaust gases, provision is made to avoid overheating of the refrigerant during ORC system shut down while at the same time preventing condensation of those gases within the vapor generator when its temperature drops below a threshold temperature by diverting the flow of hot gases to ambient and to thereby draw ambient air through the vapor generator in the process. In one embodiment, a bistable ejector is adjustable between one position, in which the hot gases flow through the vapor generator, to another position wherein the gases are diverted away from the vapor generator. Another embodiment provides for a fixed valve ejector with a bias towards discharging to ambient, but with a fan on the downstream side of said vapor generator for overcoming this bias.

  17. Numerical Simulations of Plasma Based Flow Control Applications

    NASA Technical Reports Server (NTRS)

    Suzen, Y. B.; Huang, P. G.; Jacob, J. D.; Ashpis, D. E.

    2005-01-01

    A mathematical model was developed to simulate flow control applications using plasma actuators. The effects of the plasma actuators on the external flow are incorporated into Navier Stokes computations as a body force vector. In order to compute this body force vector, the model solves two additional equations: one for the electric field due to the applied AC voltage at the electrodes and the other for the charge density representing the ionized air. The model is calibrated against an experiment having plasma-driven flow in a quiescent environment and is then applied to simulate a low pressure turbine flow with large flow separation. The effects of the plasma actuator on control of flow separation are demonstrated numerically.

  18. Flow Separation Control Over a Ramp Using Sweeping Jet Actuators

    NASA Technical Reports Server (NTRS)

    Koklu, Mehti; Owens, Lewis R.

    2014-01-01

    Flow separation control on an adverse-pressure-gradient ramp model was investigated using various flow-control methods in the NASA Langley 15-Inch Wind Tunnel. The primary flow-control method studied used a sweeping jet actuator system to compare with more classic flow-control techniques such as micro-vortex generators, steady blowing, and steady- and unsteady-vortex generating jets. Surface pressure measurements and a new oilflow visualization technique were used to characterize the effects of these flow-control actuators. The sweeping jet actuators were run in three different modes to produce steady-straight, steady-angled, and unsteady-oscillating jets. It was observed that all of these flow-control methods are effective in controlling the separated flows on the ramp model. The steady-straight jet energizes the boundary layer by momentum addition and was found to be the least effective method for a fixed momentum coefficient. The steady-angled jets achieved better performance than the steady-straight jets because they generate streamwise vortices that energize the boundary layer by mixing high-momentum fluid with near wall low-momentum fluid. The unsteady-oscillating jets achieved the best performance by increasing the pressure recovery and reducing the downstream flow separation. Surface flow visualizations indicated that two out-of-phase counter-rotating vortices are generated per sweeping jet actuator, while one vortex is generated per vortex-generating jets. The extra vortex resulted in increased coverage, more pressure recovery, and reduced flow separation.

  19. Measurement and control systems for an imaging electromagnetic flow metre.

    PubMed

    Zhao, Y Y; Lucas, G; Leeungculsatien, T

    2014-03-01

    Electromagnetic flow metres based on the principles of Faraday's laws of induction have been used successfully in many industries. The conventional electromagnetic flow metre can measure the mean liquid velocity in axisymmetric single phase flows. However, in order to achieve velocity profile measurements in single phase flows with non-uniform velocity profiles, a novel imaging electromagnetic flow metre (IEF) has been developed which is described in this paper. The novel electromagnetic flow metre which is based on the 'weight value' theory to reconstruct velocity profiles is interfaced with a 'Microrobotics VM1' microcontroller as a stand-alone unit. The work undertaken in the paper demonstrates that an imaging electromagnetic flow metre for liquid velocity profile measurement is an instrument that is highly suited for control via a microcontroller.

  20. Radiant energy receiver having improved coolant flow control means

    DOEpatents

    Hinterberger, H.

    1980-10-29

    An improved coolant flow control for use in radiant energy receivers of the type having parallel flow paths is disclosed. A coolant performs as a temperature dependent valve means, increasing flow in the warmer flow paths of the receiver, and impeding flow in the cooler paths of the receiver. The coolant has a negative temperature coefficient of viscosity which is high enough such that only an insignificant flow through the receiver is experienced at the minimum operating temperature of the receiver, and such that a maximum flow is experienced at the maximum operating temperature of the receiver. The valving is accomplished by changes in viscosity of the coolant in response to the coolant being heated and cooled. No remotely operated valves, comparators or the like are needed.

  1. Design and Implementation of Automatic Air Flow Rate Control System

    NASA Astrophysics Data System (ADS)

    Akbar, A.; Saputra, C.; Munir, M. M.; Khairurrijal

    2016-08-01

    Venturimeter is an apparatus that can be used to measure the air flow rate. In this experiment we designed a venturimeter which equipped with a valve that is used to control the air flow rate. The difference of pressure between the cross sections was measured with the differential pressure sensor GA 100-015WD which can calculate the difference of pressures from 0 to 3737.33 Pa. A 42M048C Z36 stepper motor was used to control the valve. The precision of this motor rotation is about 0.15 °. A Graphical User Interface (GUI) was developed to monitor and set the value of flow rate then an 8-bit microcontroller was used to process the control system In this experiment- the venturimeter has been examined to get the optimal parameter of controller. The results show that the controller can set the stable output air flow rate.

  2. Double Stage Heat Transformer Controlled by Flow Ratio

    NASA Astrophysics Data System (ADS)

    Silva-Sotelo, S.; Romero, R. J.; Rodríguez – Martínez, A.

    this paper shows the values of Flow ratio (FR) for control of an absorption double stage heat transformer. The main parameters for the heat pump system are defined as COP, FR and GTL. The control of the entire system is based in a new definition of FR. The heat balance of the Double Stage Heat Transformer (DSHT) is used for the control. The mass flow is calculated for a HPVEE program and a second program control the mass flow. The mass flow is controlled by gear pumps connected to LabView program. The results show an increment in the fraction of the recovery energy. An example of oil distillation is used for the calculation. The waste heat energy is added at the system at 70 °C. Water ™ - Carrol mixture is used in the DSHT. The recover energy is obtained in a second absorber at 128 °C with two scenarios.

  3. Flow and quiet eye: the role of attentional control in flow experience.

    PubMed

    Harris, David J; Vine, Samuel J; Wilson, Mark R

    2017-02-25

    This report was designed to investigate the role of effective attention control in flow states, by developing an experimental approach to the study of flow. A challenge-skill balance manipulation was applied to self-paced netball and basketball shooting tasks, with point of gaze recorded through mobile eye tracking. Quiet eye was used to index optimal control of visual attention. While the experimental manipulation was found to have no effect, quiet eye was associated with the experience of flow. Furthermore, mediation revealed an indirect effect of quiet eye on performance through flow experience. This study provides initial evidence that flow may be preceded by changes in visual attention, suggesting that further investigation of visual attention may elucidate the cognitive mechanisms behind flow experience.

  4. Photothermally controlled Marangoni flow around a micro bubble

    SciTech Connect

    Namura, Kyoko Nakajima, Kaoru; Kimura, Kenji; Suzuki, Motofumi

    2015-01-26

    We have experimentally investigated the control of Marangoni flow around a micro bubble using photothermal conversion. Using a focused laser spot acting as a highly localized heat source on Au nanoparticles/dielectric/Ag mirror thin film enables us to create a micro bubble and to control the temperature gradient around the bubble at a micrometer scale. When we irradiate the laser next to the bubble, a strong main flow towards the bubble and two symmetric rotation flows on either side of it develop. The shape of this rotation flow shows a significant transformation depending on the relative position of the bubble and the laser spot. Using this controllable rotation flow, we have demonstrated sorting of the polystyrene spheres with diameters of 2 μm and 0.75 μm according to their size.

  5. Coupled parametric design of flow control and duct shape

    NASA Technical Reports Server (NTRS)

    Florea, Razvan (Inventor); Bertuccioli, Luca (Inventor)

    2009-01-01

    A method for designing gas turbine engine components using a coupled parametric analysis of part geometry and flow control is disclosed. Included are the steps of parametrically defining the geometry of the duct wall shape, parametrically defining one or more flow control actuators in the duct wall, measuring a plurality of performance parameters or metrics (e.g., flow characteristics) of the duct and comparing the results of the measurement with desired or target parameters, and selecting the optimal duct geometry and flow control for at least a portion of the duct, the selection process including evaluating the plurality of performance metrics in a pareto analysis. The use of this method in the design of inter-turbine transition ducts, serpentine ducts, inlets, diffusers, and similar components provides a design which reduces pressure losses and flow profile distortions.

  6. Flow control in low pressure turbine blades using plasma actuators

    NASA Astrophysics Data System (ADS)

    Ramakumar, Karthik

    2005-11-01

    An experimental study of plasma flow control actuators for flow separation control in low pressure turbine (LPT) blades is presented. The actuator arrangement consists of two copper strips separated by a dielectric medium with an input voltage of approximately 5kV and a frequency input varying from 3-5 kHz, creating a region of plasma used for boundary layer flow control. The effect of varying waveform on control efficacy is investigated using sine, square and saw tooth waveforms. The impact of duty cycle and forcing frequency on both displacement and momentum thickness are also examined. Boundary layer measurements are carried out using PIV while measurements of the wake downstream are performed using a 7-hole probe for Reynolds number ranging from 30,000 to 50,000. Separation is fully controlled in most configurations and boundary layer parameters reveal that the actuator entrains the free-stream flow at the actuator location and creates a region of high turbulence, essentially behaving similar to an active boundary layer trip. A small region of reversed flow near the surface indicates the presence of cross-stream vortical structures. The use of plasma synthetic jet actuators flow LPT flow control is also discussed.

  7. NASA F-16XL supersonic laminar flow control program overview

    NASA Technical Reports Server (NTRS)

    Fischer, Michael C.

    1992-01-01

    The viewgraphs and discussion of the NASA supersonic laminar flow control program are provided. Successful application of laminar flow control to a High Speed Civil Transport (HSCT) offers significant benefits in reductions of take-off gross weight, mission fuel burn, cruise drag, structural temperatures, engine size, emissions, and sonic boom. The ultimate economic success of the proposed HSCT may depend on the successful adaption of laminar flow control, which offers the single most significant potential improvements in lift drag ratio (L/D) of all the aerodynamic technologies under consideration. The F-16XL Supersonic Laminar Flow Control (SLFC) Experiment was conceived based on the encouraging results of in-house and NASA supported industry studies to determine if laminar flow control is feasible for the HSCT. The primary objective is to achieve extensive laminar flow (50-60 percent chord) on a highly swept supersonic wing. Data obtained from the flight test will be used to validate existing Euler and Navier Stokes aerodynamic codes and transition prediction boundary layer stability codes. These validated codes and developed design methodology will be delivered to industry for their use in designing supersonic laminar flow control wings. Results from this experiment will establish preliminary suction system design criteria enabling industry to better size the suction system and develop improved estimates of system weight, fuel volume loss due to wing ducting, turbocompressor power requirements, etc. so that benefits and penalties can be more accurately assessed.

  8. A summary of laser and microwave flow control in high-speed flows

    NASA Astrophysics Data System (ADS)

    Knight, D.

    2013-06-01

    Laser and microwave discharge in air has emerged as an effective method for flow control in high-speed flows. Computational and experimental research has demonstrated its capability for significant drag reduction and mitigation of adverse interactions in high-speed flows. The paper presents a summary of key computational and experimental studies performed at Rutgers University in collaboration with the Joint Institute for High Temperatures (Moscow, Russia) and St. Petersburg State University (St. Petersburg, Russia).

  9. Highly simplified lateral flow-based nucleic acid sample preparation and passive fluid flow control

    SciTech Connect

    Cary, Robert E.

    2015-12-08

    Highly simplified lateral flow chromatographic nucleic acid sample preparation methods, devices, and integrated systems are provided for the efficient concentration of trace samples and the removal of nucleic acid amplification inhibitors. Methods for capturing and reducing inhibitors of nucleic acid amplification reactions, such as humic acid, using polyvinylpyrrolidone treated elements of the lateral flow device are also provided. Further provided are passive fluid control methods and systems for use in lateral flow assays.

  10. The Investigation of Blowing Parameter Similarity for Controlling Flow Separation over Control Surface

    NASA Astrophysics Data System (ADS)

    Wang, Y. K.; Wu, P.; Deng, X. Y.; Zheng, W. L.; Zhang, Y. H.

    2011-09-01

    Because the flight performance of aircraft is so dependent on aerodynamic efficiency of elevator, it is very important to improve the flow separation over the control surfaces at high deflection angle in order to keep the aircraft having good flight capability, especially for the modern aircraft with tailless aerodynamic configuration. A new flow control technique to improve the flow separation over the control surface by microblowing at the flow separated position is discussed in this paper. Furthermore, the effect of the various blowing parameters are also investigated in detail, and based on these studies, the parameter similarity about this flow control technique is discussed.

  11. Automatic coolant flow control device for a nuclear reactor assembly

    SciTech Connect

    Hutter, Ernest

    1986-01-01

    A device which controls coolant flow through a nuclear reactor assembly comprises a baffle means at the exit end of said assembly having a plurality of orifices, and a bimetallic member in operative relation to the baffle means such that at increased temperatures said bimetallic member deforms to unblock some of said orifices and allow increased coolant flow therethrough.

  12. Automatic air flow control in air conditioning ducts

    NASA Technical Reports Server (NTRS)

    Obler, H. D.

    1972-01-01

    Device is designed which automatically selects air flow coming from either of two directions and which can be adjusted to desired air volume on either side. Device uses one movable and two fixed scoops which control air flow and air volume.

  13. Automatic coolant flow control device for a nuclear reactor assembly

    DOEpatents

    Hutter, E.

    1984-01-27

    A device which controls coolant flow through a nuclear reactor assembly comprises a baffle means at the exit end of said assembly having a plurality of orifices, and a bimetallic member in operative relation to the baffle means such that at increased temperatures said bimetallic member deforms to unblock some of said orifices and allow increased coolant flow therethrough.

  14. Numerical Modeling of Compressible Flow and Its Control

    DTIC Science & Technology

    2014-03-01

    Two main technical areas were addressed: nanosecond- pulse , dielectric barrier discharge flow control actuators, and large-scale unsteadiness in...interactions as a major influence on the experiments. High-fidelity fluid simulations of nanosecond- pulse discharges demonstrated the importance of rapid...shows promise for mitigating fatigue loading on high Mach number aircraft. 15. SUBJECT TERMS computational fluid dynamics, CFD , computational, flow

  15. Flow control mechanism of capillary driven flow in microchannel using non-mechanical forces

    NASA Astrophysics Data System (ADS)

    Nunna, Bharath Babu; Zhuang, Shiqiang; Lee, Eon Soo

    2016-11-01

    The capillary driven flow in microchannel is a self-driven flow by the natural phenomenon called surface tension of the fluid. The gradients in surface tension force which influence the flow field in microchannel is generated by the modulation of contact angle through a defined hydrophilization of the PDMS (Polydimethylsiloxane) microchannel surface. PDMS which is hydrophobic in nature is treated with various surface treatments in order to convert it to hydrophilic. The contact angle made by the fluid with the PDMS microchannel surface is altered when the surface is converted from hydrophobic to hydrophilic. The flow rate of fluid in the microchannel is directly proportional to the hydrophilicity of that microchannel since the capillary force which is the driving force of the flow is dependent on the contact angle. Flow control mechanism of capillary driven flow in microchannel using non-mechanical forces is developed by treating the microchannel surfaces with various surface treatments. The precise control of the surface characteristics like hydrophilicity and roughness of the miocrochannel helps to control the capillary flow in microchannel. The flow rate variation with respect to the various surface treated channels are studied. Principal Investigator.

  16. Flow control in a diffusing S-Duct

    NASA Technical Reports Server (NTRS)

    Vakili, A. D.; Wu, J. M.; Liver, P.; Bhat, M. K.

    1985-01-01

    Accurate measurements have been made of secondary flow in a 1.51 area ratio diffusing 30 deg - 30 deg S-Duct with circulair cross section. Turbulent flow was entering the duct at Mach number of 0.6, the boundary layer thickness at the duct entrance was ten percent of the duct inlet diameter. Through measurements made, local flow velocity vector as well as static and total pressures mapping of the flow at several stations were obtained. Strong secondary flow was measured in the first bend which continued into the second bend with new vorticity produced in there in the opposite direction. Surface oil flow visualization and wall pressures indicated a region of separated flow starting at theta approximately equal to 22 deg on the inside of the first bend up to theta approximately equal to 44 deg on the outside of the second bend. The flow separated in 'cyclone' form and never reattached in the duct. As a result of the secondary flow and the flow separation, significant total pressure distortion was observed at the exit of the duct. Using flow control devices the separation was eliminated while the exit distortion was improved.

  17. Flow control in a diffusing S-Duct

    NASA Technical Reports Server (NTRS)

    Vakili, A. D.; Wu, J. M.; Liver, P.; Bhat, M. K.

    1985-01-01

    Accurate measurements have been made of secondary flow in a 1.51 area ratio diffusing 30 deg - 30 deg S-Duct with circulair cross section. Turbulent flow was entering the duct at Mach number of 0.6, the boundary layer thickness at the duct entrance was ten percent of the duct inlet diameter. Through measurements made, local flow velocity vector as well as static and total pressures mapping of the flow at several stations were obtained. Strong secondary flow was measured in the first bend which continued into the second bend with new vorticity produced in there in the opposite direction. Surface oil flow visualization and wall pressures indicated a region of separated flow starting at theta approximately equal to 22 deg on the inside of the first bend up to theta approximately equal to 44 deg on the outside of the second bend. The flow separated in 'cyclone' form and never reattached in the duct. As a result of the secondary flow and the flow separation, significant total pressure distortion was observed at the exit of the duct. Using flow control devices the separation was eliminated while the exit distortion was improved.

  18. Summary of Data from the First AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Levy, David W.; Zickuhr, Tom; Vassberg, John; Agrawal, Shreekant; Wahls, Richard A.; Pirzadeh, Shahyar; Hemsch, Michael J.

    2002-01-01

    The results from the first AIAA CFD Drag Prediction Workshop are summarized. The workshop was designed specifically to assess the state-of-the-art of computational fluid dynamics methods for force and moment prediction. An impartial forum was provided to evaluate the effectiveness of existing computer codes and modeling techniques, and to identify areas needing additional research and development. The subject of the study was the DLR-F4 wing-body configuration, which is representative of transport aircraft designed for transonic flight. Specific test cases were required so that valid comparisons could be made. Optional test cases included constant-C(sub L) drag-rise predictions typically used in airplane design by industry. Results are compared to experimental data from three wind tunnel tests. A total of 18 international participants using 14 different codes submitted data to the workshop. No particular grid type or turbulence model was more accurate, when compared to each other, or to wind tunnel data. Most of the results overpredicted C(sub Lo) and C(sub Do), but induced drag (dC(sub D)/dC(sub L)(exp 2)) agreed fairly well. Drag rise at high Mach number was underpredicted, however, especially at high C(sub L). On average, the drag data were fairly accurate, but the scatter was greater than desired. The results show that well-validated Reynolds-Averaged Navier-Stokes CFD methods are sufficiently accurate to make design decisions based on predicted drag.

  19. The Combination of Micro Diaphragm Pumps and Flow Sensors for Single Stroke Based Liquid Flow Control

    PubMed Central

    Jenke, Christoph; Pallejà Rubio, Jaume; Kibler, Sebastian; Häfner, Johannes; Richter, Martin; Kutter, Christoph

    2017-01-01

    With the combination of micropumps and flow sensors, highly accurate and secure closed-loop controlled micro dosing systems for liquids are possible. Implementing a single stroke based control mode with piezoelectrically driven micro diaphragm pumps can provide a solution for dosing of volumes down to nanoliters or variable average flow rates in the range of nL/min to μL/min. However, sensor technologies feature a yet undetermined accuracy for measuring highly pulsatile micropump flow. Two miniaturizable in-line sensor types providing electrical readout—differential pressure based flow sensors and thermal calorimetric flow sensors—are evaluated for their suitability of combining them with mircopumps. Single stroke based calibration of the sensors was carried out with a new method, comparing displacement volumes and sensor flow volumes. Limitations of accuracy and performance for single stroke based flow control are described. Results showed that besides particle robustness of sensors, controlling resistive and capacitive damping are key aspects for setting up reproducible and reliable liquid dosing systems. Depending on the required average flow or defined volume, dosing systems with an accuracy of better than 5% for the differential pressure based sensor and better than 6.5% for the thermal calorimeter were achieved. PMID:28368344

  20. The Combination of Micro Diaphragm Pumps and Flow Sensors for Single Stroke Based Liquid Flow Control.

    PubMed

    Jenke, Christoph; Pallejà Rubio, Jaume; Kibler, Sebastian; Häfner, Johannes; Richter, Martin; Kutter, Christoph

    2017-04-03

    With the combination of micropumps and flow sensors, highly accurate and secure closed-loop controlled micro dosing systems for liquids are possible. Implementing a single stroke based control mode with piezoelectrically driven micro diaphragm pumps can provide a solution for dosing of volumes down to nanoliters or variable average flow rates in the range of nL/min to μL/min. However, sensor technologies feature a yet undetermined accuracy for measuring highly pulsatile micropump flow. Two miniaturizable in-line sensor types providing electrical readout-differential pressure based flow sensors and thermal calorimetric flow sensors-are evaluated for their suitability of combining them with mircopumps. Single stroke based calibration of the sensors was carried out with a new method, comparing displacement volumes and sensor flow volumes. Limitations of accuracy and performance for single stroke based flow control are described. Results showed that besides particle robustness of sensors, controlling resistive and capacitive damping are key aspects for setting up reproducible and reliable liquid dosing systems. Depending on the required average flow or defined volume, dosing systems with an accuracy of better than 5% for the differential pressure based sensor and better than 6.5% for the thermal calorimeter were achieved.

  1. Research in Natural Laminar Flow and Laminar-Flow Control, part 2

    NASA Technical Reports Server (NTRS)

    Hefner, Jerry N. (Compiler); Sabo, Frances E. (Compiler)

    1987-01-01

    Part 2 of the Symposium proceedings includes papers addressing various topics in basic wind tunnel research/techniques and computational transitional research. Specific topics include: advanced measurement techniques; laminar flow control; Tollmien-Schlichting wave characteristics; boundary layer transition; flow visualization; wind tunnel tests; flight tests; boundary layer equations; swept wings; and skin friction.

  2. Development of a Nonlinear Simulation for the McDonnell Douglas F-15 Eagle with a Longitudinal TECS Control-Law.

    DTIC Science & Technology

    1994-09-01

    E.L., Antoniewicz, R.F., and Krambeer, K.D., Derivation and Definition of a Linear Aircraft Model, NASA RP-1207, Aug. 1988. [7] Lambregts , A.A...Integrated System Design for Flight and Propulsion Control using Total Energy Principles. Technical Report AIAA 83-2561, AIAA, October 1983. [8] Lambregts

  3. RETROFITTING CONTROL FACILITIES FOR WET WEATHER FLOW TREATMENT

    EPA Science Inventory

    Available technologies were evaluated to demonstrate the technical feasibility and cost-effectiveness of retrofitting existing facilities to handle wet-weather flow. Cost/benefit relationships were also compared to construction of new conventional control and treatment facilitie...

  4. RETROFITTING CONTROL FACILITIES FOR WET WEATHER FLOW TREATMENT

    EPA Science Inventory

    Available technologies were evaluated to demonstrate the technical feasibility and cost-effectiveness of retrofitting existing facilities to handle wet-weather flow. Cost/benefit relationships were also compared to construction of new conventional control and treatment facilitie...

  5. RETROFITTING CONTROL FACILITIES FOR WET-WEATHER FLOW TREATMENT

    EPA Science Inventory

    Available technologies were evaluated to demonstrate the technical feasibility and cost effectiveness of retrofitting existing facilities to handle wet-weather flow. Cost/benefit relationships were also compared to construction of new conventional control and treatment facilities...

  6. Increasing Wind Turbine Power Generation Through Optimized Flow Control Design

    NASA Astrophysics Data System (ADS)

    Cooney, John; Williams, Theodore; Corke, Thomas

    2013-11-01

    A practical, validated methodology is outlined for implementing flow control systems into wind turbine designs to maximize power generation. This approach involves determining optimal flow control strategies to minimize aerodynamic losses for horizontal axis wind turbines during Region II operation. A quantitative design optimization (QDO) process is completed for the wind turbine utilized in the Notre Dame Laboratory for Enhanced Wind Energy Research. QDO utilizes CFD simulations and shape optimization tools to maximize effectiveness of flow control. Here, only flow control schemes that could be retrofitted on the existing turbine were explored. The final geometry is discussed along with accompanying validations of the predicted performance from wind tunnel experiments at full-scale conditions. Field data from the wind energy laboratory is included.

  7. RETROFITTING CONTROL FACILITIES FOR WET-WEATHER FLOW TREATMENT

    EPA Science Inventory

    Available technologies were evaluated to demonstrate the technical feasibility and cost effectiveness of retrofitting existing facilities to handle wet-weather flow. Cost/benefit relationships were also compared to construction of new conventional control and treatment facilities...

  8. Feedback Flow Control for a Pitching Turret (Part II) (POSTPRINT)

    DTIC Science & Technology

    2010-01-01

    imposes no penalty on the control input. VII. Closed-loop Control Run with an Advanced Controller Three compensators ( LQR regulators with Kalman...AFRL-RB-WP-TP-2010-3024 FEEDBACK FLOW CONTROL FOR A PITCHING TURRET (PART II) (POSTPRINT) T. Vaithianathan and H.A. Carlson Clear...display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YY) 2. REPORT TYPE 3

  9. Flow-Control Unit For Nitrogen And Hydrogen Gases

    NASA Technical Reports Server (NTRS)

    Chang, B. J.; Novak, D. W.

    1990-01-01

    Gas-flow-control unit installed and removed as one piece replaces system that included nine separately serviced components. Unit controls and monitors flows of nitrogen and hydrogen gases. Designed for connection via fluid-interface manifold plate, reducing number of mechanical fluid-interface connections from 18 to 1. Unit provides increasing reliability, safety, and ease of maintenance, and for reducing weight, volume, and power consumption.

  10. Control of Population Flow in Coherently Driven Quantum Ladders

    SciTech Connect

    Garcia-Fernandez, Ruth; Bergmann, Klaas; Ekers, Aigars; Yatsenko, Leonid P.; Vitanov, Nikolay V.

    2005-07-22

    A technique for adiabatic control of the population flow through a preselected decaying excited level in a three-level quantum ladder is presented. The population flow through the intermediate or upper level is controlled efficiently and robustly by varying the pulse delay between a pair of partly overlapping coherent laser pulses. The technique is analyzed theoretically and demonstrated in an experiment with Na{sub 2} molecules.

  11. Control of Spatially Inhomogeneous Shear Flows

    DTIC Science & Technology

    2011-10-01

    input B2 consists of an array of localized actuators described by an analytical Gaussian function . The temporal forcing of the system is provided by the...easily access the tools of linear control theory . For our application, a basis of approximate balanced modes (Rowley 2005) is computed using a snapshot...the red line depicts the evolution of the energy- density of a TS wavepacket , whereas the black line shows the same quantity when feedback control (case

  12. A sliding mode controller for vehicular traffic flow

    NASA Astrophysics Data System (ADS)

    Li, Yongfu; Kang, Yuhao; Yang, Bin; Peeta, Srinivas; Zhang, Li; Zheng, Taixong; Li, Yinguo

    2016-11-01

    This study proposes a sliding mode controller for vehicular traffic flow based on a car-following model to enhance the smoothness and stability of traffic flow evolution. In particular, the full velocity difference (FVD) model is used to capture the characteristics of vehicular traffic flow. The proposed sliding mode controller is designed in terms of the error between the desired space headway and the actual space headway. The stability of the controller is guaranteed using the Lyapunov technique. Numerical experiments are used to compare the performance of sliding mode control (SMC) with that of feedback control. The results illustrate the effectiveness of the proposed SMC method in terms of the distribution smoothness and stability of the space headway, velocity, and acceleration profiles. They further illustrate that the SMC strategy is superior to that of the feedback control strategy, while enabling computational efficiency that can aid in practical applications.

  13. Nuclear reactor flow control method and apparatus

    DOEpatents

    Church, John P.

    1993-01-01

    Method and apparatus for improving coolant flow in a nuclear reactor during accident as well as nominal conditions. The reactor has a plurality of fuel elements in sleeves and a plenum above the fuel and through which the sleeves penetrate. Holes are provided in the sleeve so that coolant from the plenum can enter the sleeve and cool the fuel. The number and size of the holes are varied from sleeve to sleeve with the number and size of holes being greater for sleeves toward the center of the core and less for sleeves toward the periphery of the core. Preferably the holes are all the same diameter and arranged in rows and columns, the rows starting from the bottom of every sleeve and fewer rows in peripheral sleeves and more rows in the central sleeves.

  14. Nuclear reactor flow control method and apparatus

    DOEpatents

    Church, J.P.

    1993-03-30

    Method and apparatus for improving coolant flow in a nuclear reactor during accident as well as nominal conditions. The reactor has a plurality of fuel elements in sleeves and a plenum above the fuel and through which the sleeves penetrate. Holes are provided in the sleeve so that coolant from the plenum can enter the sleeve and cool the fuel. The number and size of the holes are varied from sleeve to sleeve with the number and size of holes being greater for sleeves toward the center of the core and less for sleeves toward the periphery of the core. Preferably the holes are all the same diameter and arranged in rows and columns, the rows starting from the bottom of every sleeve and fewer rows in peripheral sleeves and more rows in the central sleeves.

  15. Method, apparatus and system for controlling fluid flow

    DOEpatents

    McMurtrey, Ryan D.; Ginosar, Daniel M.; Burch, Joesph V.

    2007-10-30

    A system, apparatus and method of controlling the flow of a fluid are provided. In accordance with one embodiment of the present invention, a flow control device includes a valve having a flow path defined therethrough and a valve seat in communication with the flow path with a valve stem disposed in the valve seat. The valve stem and valve seat are cooperatively configured to cause mutual relative linear displacement thereof in response to rotation of the valve stem. A gear member is coupled with the rotary stem and a linear positioning member includes a portion which complementarily engages the gear member. Upon displacement of the linear positioning member along a first axis, the gear member and rotary valve stem are rotated about a second axis and the valve stem and valve seat are mutually linearly displaced to alter the flow of fluid through the valve.

  16. Controlling flow direction in nanochannels by electric field strength

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Zhao, Tianshou; Li, Zhigang

    2015-08-01

    Molecular dynamics simulations are conducted to study the flow behavior of CsF solutions in nanochannels under external electric fields E . It is found that the channel surface energy greatly affects the flow behavior. In channels of high surface energy, water molecules, on average, move in the same direction as that of the electric field regardless of the strength of E . In low surface energy channels, however, water transports in the opposite direction to the electric field at weak E and the flow direction is changed when E becomes sufficiently large. The direction change of water flow is attributed to the coupled effects of different water-ion interactions, inhomogeneous water viscosity, and ion distribution changes caused by the electric field. The flow direction change observed in this work may be employed for flow control in complex micro- or nanofluidic systems.

  17. Exhaust bypass flow control for exhaust heat recovery

    DOEpatents

    Reynolds, Michael G.

    2015-09-22

    An exhaust system for an engine comprises an exhaust heat recovery apparatus configured to receive exhaust gas from the engine and comprises a first flow passage in fluid communication with the exhaust gas and a second flow passage in fluid communication with the exhaust gas. A heat exchanger/energy recovery unit is disposed in the second flow passage and has a working fluid circulating therethrough for exchange of heat from the exhaust gas to the working fluid. A control valve is disposed downstream of the first and the second flow passages in a low temperature region of the exhaust heat recovery apparatus to direct exhaust gas through the first flow passage or the second flow passage.

  18. Computer-controlled positive displacement pump for physiological flow simulation.

    PubMed

    Holdsworth, D W; Rickey, D W; Drangova, M; Miller, D J; Fenster, A

    1991-11-01

    A computer-controlled pump for use both in the study of vascular haemodynamics and in the calibration of clinical devices which measure blood flow is designed. The novel design of this pump incorporates two rack-mounted pistons, driven into opposing cylinders by a micro-stepping motor. This approach allows the production of nearly uninterrupted steady flow, as well as a variety of pulsatile waveforms, including waveforms with reverse flow. The capabilities of this pump to produce steady flow from 0.1 to 60 ml s-1, as well as sinusoidal flow and physiological flow, such as that found in the common femoral and common carotid arteries are demonstrated. Cycle-to-cycle reproducibility is very good, with an average variation of 0.1 ml s-1 over thousands of cycles.

  19. Velocity control for improving flow through a bottleneck

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hiroki; Yanagisawa, Daichi; Nishinari, Katsuhiro

    2017-04-01

    A bottleneck can largely deteriorate the flow, such as a traffic light or an on-ramp at a road. To alleviate bottleneck situations, one of the important strategies is to control input rate to suit the state of the road. In this study, we propose an effective velocity control of traveling particles, in which the particle velocity depends on the state of a bottleneck. To analyze our method, we modify the totally asymmetric simple exclusion process (TASEP) and introduce a slow-to-start rule, which we refer to as controlled TASEP in the present paper. Flow improvement is verified in numerical simulations and theoretical analyses by using controlled TASEP.

  20. An extended signal control strategy for urban network traffic flow

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Tian, Fuli; Shi, Zhongke

    2016-03-01

    Traffic flow patterns are in general repeated on a daily or weekly basis. To improve the traffic conditions by using the inherent repeatability of traffic flow, a novel signal control strategy for urban networks was developed via iterative learning control (ILC) approach. Rigorous analysis shows that the proposed learning control method can guarantee the asymptotic convergence. The impacts of the ILC-based signal control strategy on the macroscopic fundamental diagram (MFD) were analyzed by simulations on a test road network. The results show that the proposed ILC strategy can evenly distribute the accumulation in the network and improve the network mobility.

  1. Experimental Study of Plasma Control of an Unstarting Supersonic Flow

    NASA Astrophysics Data System (ADS)

    Im, Seong-Kyun; Do, Hyungrok; Cappelli, Mark A.

    2011-11-01

    Experimental studies of the control of unstarting supersonic model inlet flows using Dielectric Barrier Discharges (DBD) is demonstrated at Mach 4.7 flow conditions and a static temperature of ~60K and static pressure of ~1kPa. Planar Laser Rayleigh Scattering (PLRS) is used to visualize important flow features, such as boundary layers and shockwaves. Supersonic flow unstart is initiated by injecting mass into model inlet flows of either laminar or tripped turbulent boundary layer flow conditions. DBD discharge actuation of the tripped turbulent flow delays the unstart process, shifting the unstart dynamics closer to what is seen for the laminar boundary layer case. In all studies, a single DBD actuator pair is used, oriented parallel to the freestream flow, generating spanwise disturbances. It is proposed that strong suction flow which brings high momentum freestream flow near exposed electrode can be a mechanism of this actuation. PLRS reveals that this actuation is spatially confined to the regions close to the actuator electrodes, greatly limiting their performance. This material is based upon work supported by the Department of Energy under Award Number(s)DE-FC52-08NA28614.

  2. Control of flow rate and concentration in microchannel branches by induced-charge electrokinetic flow.

    PubMed

    Zhang, Fang; Daghighi, Yasaman; Li, Dongqing

    2011-12-15

    This paper presents a numerical study of controlling the flow rate and the concentration in a microchannel network by utilizing induced-charge electrokinetic flow (ICEKF). ICEKF over an electrically conducting surface in a microchannel will generate vortices, which can be used to adjust the flow rates and the concentrations in different microchannel branches. The flow field and concentration field were studied under different applied electric fields and with different sizes of the conducting surfaces. The results show that, by using appropriate size of the conducting surfaces in appropriate locations, the microfluidic system can generate not only streams of the same flow rate or linearly decreased flow rates in different channels, but also different, uniform concentrations within a short mixing length quickly.

  3. Controls on sediment transfer and storage on debris flow fans

    NASA Astrophysics Data System (ADS)

    Schürch, Peter; Densmore, Alexander L.; Rosser, Nick J.; McArdell, Brian W.

    2010-05-01

    Debris flows are important in transporting sediment from mountain slopes to valley floors. Debris flow fans are regarded as sediment traps, but often little is known about what proportion of the input at the fan apex is stored on the fan (the fan efficiency, ef) or how individual debris flow volumes evolve via entrainment and deposition along the flow path. It is therefore crucial to investigate the controls on debris flow volume change along the whole flow path in order to understand the role that debris flows play within the integrated sediment routing system. We present high spatial resolution data on the volume change of debris flows due to entrainment and deposition on the Illgraben fan, Switzerland. This fan has experienced 36 debris flows since June 2000, generally in response to summer (May-October) convective storms. We compare debris flow hydrographs from fan apex and fan toe with locally measured lag rates from terrestrial laser scanning (TLS) of a 300 m study reach for several of these events. Debris flow volumes are calculated from hydrographs measured by radar sensors, and flow velocity estimates are based on geophone measurements of flow front position. The debris flow lag rate is defined as the volume change per unit channel length. We present high-resolution (0.2 m grid) change maps from successive sets of TLS topographic data along the study reach. We use the change maps to derive reach-scale lag rates of single debris flow events by projecting the volume change onto a flow axis down the channel thalweg. We use video recordings of the flow fronts and recordings of geophones and radar sensors to investigate flow properties in two locations along the flow path. The flow hydrograph data show that flow volumes can change by up to one order of magnitude between fan apex and fan toe. Both increasing and decreasing flow volumes are observed in different events moving through the same channel. Lag rates measured in the study reach with TLS data are

  4. Passive and Active Flow Control by Swimming Fishes and Mammals

    NASA Astrophysics Data System (ADS)

    Fish, F. E.; Lauder, G. V.

    2006-01-01

    What mechanisms of flow control do animals use to enhance hydrodynamic performance? Animals are capable of manipulating flow around the body and appendages both passively and actively. Passive mechanisms rely on structural and morphological components of the body (i.e., humpback whale tubercles, riblets). Active flow control mechanisms use appendage or body musculature to directly generate wake flow structures or stiffen fins against external hydrodynamic loads. Fish can actively control fin curvature, displacement, and area. The vortex wake shed by the tail differs between eel-like fishes and fishes with a discrete narrowing of the body in front of the tail, and three-dimensional effects may play a major role in determining wake structure in most fishes.

  5. Laminar flow control, 1976 - 1982: A selected annotated bibliography

    NASA Technical Reports Server (NTRS)

    Tuttle, M. H.; Maddalon, D. V.

    1982-01-01

    Laminar Flow Control technology development has undergone tremendous progress in recent years as focused research efforts in materials, aerodynamics, systems, and structures have begun to pay off. A virtual explosion in the number of research papers published on this subject has occurred since interest was first stimulated by the 1976 introduction of NASA's Aircraft Energy Efficiency Laminar Flow Control Program. The purpose of this selected bibliography is to list available, unclassified laminar flow (both controlled and natural) research completed from about 1975 to mid 1982. Some earlier pertinent reports are included but listed separately in the Appendix. Reports listed herein emphasize aerodynamics and systems studies, but some structures work is also summarized. Aerodynamic work is mainly limited to the subsonic and transonic sped regimes. Because wind-tunnel flow qualities, such as free stream disturbance level, play such an important role in boundary-layer transition, much recent research has been done in this area and it is also included.

  6. Reduction of wind tunnel wall interference by controlled wall flow

    NASA Technical Reports Server (NTRS)

    Bernstein, S. (Editor); Joppa, R. G.

    1975-01-01

    An alternate method of testing was developed in which flow through the porous walls of the tunnel was actively controlled so as to approximate free air conditions in the neighborhood of the model during the test. The amount and distribution of the controlled flow through the walls is computed using a potential flow representation of the model based on the measured lift. Theoretical analysis is presented to prove the convergence of the method to free air conditions and to substantiate the general three-dimensional theory of operation when the normal flow distribution is continuous. A two-dimensional tunnel was constructed to evaluate the concept. Results show that substantial reduction of wall interference may be achieved with relatively low values of porosity of actively controlled walls.

  7. Control and Automation of Fluid Flow, Mass Transfer and Chemical Reactions in Microscale Segmented Flow

    NASA Astrophysics Data System (ADS)

    Abolhasani, Milad

    Flowing trains of uniformly sized bubbles/droplets (i.e., segmented flows) and the associated mass transfer enhancement over their single-phase counterparts have been studied extensively during the past fifty years. Although the scaling behaviour of segmented flow formation is increasingly well understood, the predictive adjustment of the desired flow characteristics that influence the mixing and residence times, remains a challenge. Currently, a time consuming, slow and often inconsistent manual manipulation of experimental conditions is required to address this task. In my thesis, I have overcome the above-mentioned challenges and developed an experimental strategy that for the first time provided predictive control over segmented flows in a hands-off manner. A computer-controlled platform that consisted of a real-time image processing module within an integral controller, a silicon-based microreactor and automated fluid delivery technique was designed, implemented and validated. In a first part of my thesis I utilized this approach for the automated screening of physical mass transfer and solubility characteristics of carbon dioxide (CO2) in a physical solvent at a well-defined temperature and pressure and a throughput of 12 conditions per hour. Second, by applying the segmented flow approach to a recently discovered CO2 chemical absorbent, frustrated Lewis pairs (FLPs), I determined the thermodynamic characteristics of the CO2-FLP reaction. Finally, the segmented flow approach was employed for characterization and investigation of CO2-governed liquid-liquid phase separation process. The second part of my thesis utilized the segmented flow platform for the preparation and shape control of high quality colloidal nanomaterials (e.g., CdSe/CdS) via the automated control of residence times up to approximately 5 minutes. By introducing a novel oscillatory segmented flow concept, I was able to further extend the residence time limitation to 24 hours. A case study of a

  8. Flow and Noise Control: Review and Assessment of Future Directions

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Choudhari, Meelan M.; Joslin, Ronald D.

    2002-01-01

    Technologies for developing radically new aerovehicles that would combine quantum leaps in cost, safety, and performance benefits with environmental friendliness have appeared on the horizon. This report provides both an assessment of the current state-of-the-art in flow and noise control and a vision for the potential gains to be made, in terms of performance benefit for civil and military aircraft and a unique potential for noise reduction, via future advances in flow and noise technologies. This report outlines specific areas of research that will enable the breakthroughs necessary to bring this vision to reality. Recent developments in many topics within flow and noise control are reviewed. The flow control overview provides succinct summaries of various approaches for drag reduction and improved maneuvering. Both exterior and interior noise problems are examined, including dominant noise sources, physics of noise generation and propagation, and both established and proposed concepts for noise reduction. Synergy between flow and noise control is a focus and, more broadly, the need to pursue research in a more concurrent approach involving multiple disciplines. Also discussed are emerging technologies such as nanotechnology that may have a significant impact on the progress of flow and noise control.

  9. The unified power flow controller: A new approach to power transmission control

    SciTech Connect

    Gyugyi, L.; Schauder, C.D.; Williams, S.L.; Rietman, T.R.; Torgerson, D.R.; Edris, A.

    1995-04-01

    This paper shows that the Unified Power Flow Controller (UPFC) is able to control both the transmitted real power and, independently, the reactive power flows at the sending-and the receiving-end of the transmission line. The unique capabilities of the UPFC in multiple line compensation are integrated into a generalized power flow controller that is able to maintain prescribed, and independently controllable, real power and reactive power flow in the line. The paper describes the basic concepts of the proposed generalized P and Q controller and compares it to the more conventional, but related power flow controller, such as the Thyristor-Controlled Series Capacitor and Thyristor-Controlled Phase Angle Regulator. The paper also presents results of computer simulations showing the performance of the UPFC under different system conditions.

  10. Power Flow Controller for Renewables: Transformer-less Unified Power Flow Controller for Wind and Solar Power Transmission

    SciTech Connect

    2012-02-08

    GENI Project: MSU is developing a power flow controller to improve the routing of electricity from renewable sources through existing power lines. The fast, innovative, and lightweight circuitry that MSU is incorporating into its controller will eliminate the need for a separate heavy and expensive transformer, as well as the construction of new transmission lines. MSU’s controller is better suited to control power flows from distributed and intermittent wind and solar power systems than traditional transformer-based controllers are, so it will help to integrate more renewable energy into the grid. MSU‘s power flow controller can be installed anywhere in the existing grid to optimize energy transmission and help reduce transmission congestion.

  11. Global nuclear material flow/control model

    SciTech Connect

    Dreicer, J.S.; Rutherford, D.S.; Fasel, P.K.; Riese, J.M.

    1997-10-01

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The nuclear danger can be reduced by a system for global management, protection, control, and accounting as part of an international regime for nuclear materials. The development of an international fissile material management and control regime requires conceptual research supported by an analytical and modeling tool which treats the nuclear fuel cycle as a complete system. The prototype model developed visually represents the fundamental data, information, and capabilities related to the nuclear fuel cycle in a framework supportive of national or an international perspective. This includes an assessment of the global distribution of military and civilian fissile material inventories, a representation of the proliferation pertinent physical processes, facility specific geographic identification, and the capability to estimate resource requirements for the management and control of nuclear material. The model establishes the foundation for evaluating the global production, disposition, and safeguards and security requirements for fissile nuclear material and supports the development of other pertinent algorithmic capabilities necessary to undertake further global nuclear material related studies.

  12. Active Flow Control and Global Stability Analysis of Separated Flow Over a NACA 0012 Airfoil

    NASA Astrophysics Data System (ADS)

    Munday, Phillip M.

    The objective of this computational study is to examine and quantify the influence of fundamental flow control inputs in suppressing flow separation over a canonical airfoil. Most flow control studies to this date have relied on the development of actuator technology, and described the control input based on specific actuators. Taking advantage of a computational framework, we generalize the inputs to fundamental perturbations without restricting inputs to a particular actuator. Utilizing this viewpoint, generalized control inputs aim to aid in the quantification and support the design of separation control techniques. This study in particular independently introduces wall-normal momentum and angular momentum to the separated flow using swirling jets through model boundary conditions. The response of the flow field and the surface vorticity fluxes to various combinations of actuation inputs are examined in detail. By closely studying different variables, the influence of the wall-normal and angular momentum injections on separated flow is identified. As an example, open-loop control of fully separated, incompressible flow over a NACA 0012 airfoil at alpha = 6° and 9° with Re = 23,000 is examined with large-eddy simulations. For the shallow angle of attack alpha = 6°, the small recirculation region is primarily affected by wall-normal momentum injection. For a larger separation region at alpha = 9°, it is observed that the addition of angular momentum input to wall-normal momentum injection enhances the suppression of flow separation. Reducing the size of the separated flow region significantly impacts the forces, and in particular reduces drag and increases lift on the airfoil. It was found that the influence of flow control on the small recirculation region (alpha = 6°) can be sufficiently quantified with the traditional coefficient of momentum. At alpha = 9°, the effects of wall-normal and angular momentum inputs are captured by modifying the standard

  13. A Separation Control CFD Validation Test Case. Part 1; Baseline and Steady Suction

    NASA Technical Reports Server (NTRS)

    Greenblatt, David; Paschal, Keith B.; Yao, Chung-Sheng; Harris, jerome; Schaeffler, Norman W.; Washburn, Anthony E.

    2004-01-01

    Low speed flow separation over a wall-mounted hump, and its control using steady suction, were studied experimentally in order to generate a data set for a workshop aimed at validating CFD turbulence models. The baseline and controlled data sets comprised static and dynamic surface pressure measurements, flow field measurements using Particle Image Velocimetry (PIV) and wall shear stress obtained via oil-film interferometry. In addition to the specific test cases studied, surface pressures for a wide variety of conditions were reported for different Reynolds numbers and suction rates. Stereoscopic PIV and oil-film flow visualization indicated that the baseline separated flow field was mainly two-dimensional. With the application of control, some three-dimensionality was evident in the spanwise variation of pressure recovery, reattachment location and spanwise pressure fluctuations. Part 2 of this paper, under preparation for the AIAA Meeting in Reno 2005, considers separation control by means of zero-efflux oscillatory blowing.

  14. A Separation Control CFD Validation Test Case. Part 1; Baseline and Steady Suction

    NASA Technical Reports Server (NTRS)

    Greenblatt, David; Paschal, Keith B.; Yao, Chung-Sheng; Harris, Jerome; Schaeffler, Norman W.; Washburn, Anthony E.

    2004-01-01

    Low speed flow separation over a wall-mounted hump, and its control using steady suction, were studied experimentally in order to generate a data set for a workshop aimed at validating CFD turbulence models. The baseline and controlled data sets comprised static and dynamic surface pressure measurements, flow field measurements using Particle Image Velocimetry (PIV) and wall shear stress obtained via oil-film interferometry. In addition to the specific test cases studied, surface pressures for a wide variety of conditions were reported for different Reynolds numbers and suction rates. Stereoscopic PIV and oil-film flow visualization indicated that the baseline separated flow field was mainly two- dimensional. With the application of control, some three-dimensionality was evident in the spanwise variation of pressure recovery, reattachment location and spanwise pressure fluctuations. Part 2 of this paper, under preparation for the AIAA Meeting in Reno 2005, considers separation control by means of zero-efflux oscillatory blowing.

  15. Control of a Quadcopter Aerial Robot Using Optic Flow Sensing

    NASA Astrophysics Data System (ADS)

    Hurd, Michael Brandon

    This thesis focuses on the motion control of a custom-built quadcopter aerial robot using optic flow sensing. Optic flow sensing is a vision-based approach that can provide a robot the ability to fly in global positioning system (GPS) denied environments, such as indoor environments. In this work, optic flow sensors are used to stabilize the motion of quadcopter robot, where an optic flow algorithm is applied to provide odometry measurements to the quadcopter's central processing unit to monitor the flight heading. The optic-flow sensor and algorithm are capable of gathering and processing the images at 250 frames/sec, and the sensor package weighs 2.5 g and has a footprint of 6 cm2 in area. The odometry value from the optic flow sensor is then used a feedback information in a simple proportional-integral-derivative (PID) controller on the quadcopter. Experimental results are presented to demonstrate the effectiveness of using optic flow for controlling the motion of the quadcopter aerial robot. The technique presented herein can be applied to different types of aerial robotic systems or unmanned aerial vehicles (UAVs), as well as unmanned ground vehicles (UGV).

  16. Model-Based Predictive Control of Turbulent Channel Flow

    NASA Astrophysics Data System (ADS)

    Kellogg, Steven M.; Collis, S. Scott

    1999-11-01

    In recent simulations of optimal turbulence control, the time horizon over which the control is determined matches the time horizon over which the flow is advanced. A popular workhorse of the controls community, Model-Based Predictive Control (MBPC), suggests using longer predictive horizons than advancement windows. Including additional time information in the optimization may generate improved controls. When the advancement horizon is smaller than the predictive horizon, part of the optimization and resulting control are discarded. Although this inherent inefficiency may be justified by improved control predictions, it has hampered prior investigations of MBPC for turbulent flow due to the expense associated with optimal control based on Direct Numerical Simulation. The current approach overcomes this by using our optimal control formulation based on Large Eddy Simulation. This presentation summarizes the results of optimal control simulations for turbulent channel flow using various ratios of advancement and predictive horizons. These results provide clues as to the roles of foresight, control history, cost functional, and turbulence structures for optimal control of wall-bounded turbulence.

  17. Active Flow Effectors for Noise and Separation Control

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2011-01-01

    New flow effector technology for separation control and enhanced mixing is based upon shape memory alloy hybrid composite (SMAHC) technology. The technology allows for variable shape control of aircraft structures through actively deformable surfaces. The flow effectors are made by embedding shape memory alloy actuator material in a composite structure. When thermally actuated, the flow effector def1ects into or out of the flow in a prescribed manner to enhance mixing or induce separation for a variety of applications, including aeroacoustic noise reduction, drag reduction, and f1ight control. The active flow effectors were developed for noise reduction as an alternative to fixed-configuration effectors, such as static chevrons, that cannot be optimized for airframe installation effects or variable operating conditions and cannot be retracted for off-design or fail-safe conditions. Benefits include: Increased vehicle control, overall efficiency, and reduced noise throughout all f1ight regimes, Reduced flow noise, Reduced drag, Simplicity of design and fabrication, Simplicity of control through direct current stimulation, autonomous re sponse to environmental heating, fast re sponse, and a high degree of geometric stability. The concept involves embedding prestrained SMA actuators on one side of the chevron neutral axis in order to generate a thermal moment and def1ect the structure out of plane when heated. The force developed in the host structure during def1ection and the aerodynamic load is used for returning the structure to the retracted position. The chevron design is highly scalable and versatile, and easily affords active and/or autonomous (environmental) control. The technology offers wide-ranging market applications, including aerospace, automotive, and any application that requires flow separation or noise control.

  18. Superelevation and overspill control secondary flow dynamics in submarine channels

    NASA Astrophysics Data System (ADS)

    Dorrell, R. M.; Darby, S. E.; Peakall, J.; Sumner, E. J.; Parsons, D. R.; Wynn, R. B.

    2013-08-01

    In subaerial and submarine meander bends, fluid flow travels downstream in a helical spiral, the structure of which is determined by centrifugal, hydrostatic, baroclinic, and Coriolis forces that together balance frictional stresses generated by the flow. The sense of rotation of this helical flow, and in particular, whether the near bed flow is directed toward the inner bank, e.g., "river-normal," or outer bank, e.g., "river-reversed," is crucial to the morphodynamic evolution of the channel. However, in recent years, there has been a debate over the river-normal or river-reversed nature of submarine flows. Herein, we develop a novel three-dimensional closure of secondary flow dynamics, incorporating downstream convective material transport, to cast new light on this debate. Specifically, we show that the presence of net radial material transport, arising from flow superelevation and overspill, exerts a key control on the near bed orientation of secondary flow in submarine meanders. Our analysis implies that river-reversed flows are likely to be much more prevalent throughout submarine-canyon fan systems than prior studies have indicated.

  19. Passive flow control by membrane wings for aerodynamic benefit

    NASA Astrophysics Data System (ADS)

    Timpe, Amory; Zhang, Zheng; Hubner, James; Ukeiley, Lawrence

    2013-03-01

    The coupling of passive structural response of flexible membranes with the flow over them can significantly alter the aerodynamic characteristic of simple flat-plate wings. The use of flexible wings is common throughout biological flying systems inspiring many engineers to incorporate them into small engineering flying systems. In many of these systems, the motion of the membrane serves to passively alter the flow over the wing potentially resulting in an aerodynamic benefit. In this study, the aerodynamic loads and the flow field for a rigid flat-plate wing are compared to free trailing-edge membrane wings with two different pre-tensions at a chord-based Reynolds number of approximately 50,000. The membrane was silicon rubber with a scalloped free trailing edge. The analysis presented includes load measurements from a sting balance along with velocity fields and membrane deflections from synchronized, time-resolved particle image velocimetry and digital image correlation. The load measurements demonstrate increased aerodynamic efficiency and lift, while the synchronized flow and membrane measurements show how the membrane motion serves to force the flow. This passive flow control introduced by the membranes motion alters the flows development over the wing and into the wake region demonstrating how, at least for lower angles of attack, the membranes motion drives the flow as opposed to the flow driving the membrane motion.

  20. Flow Characteristics Analysis of Widows' Creek Type Control Valve for Steam Turbine Control

    SciTech Connect

    Yoo, Yong H.; Sohn, Myoung S.; Suh, Kune Y.

    2006-07-01

    The steam turbine converts the kinetic energy of steam to mechanical energy of rotor blades in the power conversion system of fossil and nuclear power plants. The electric output from the generator of which the rotor is coupled with that of the steam turbine depends on the rotation velocity of the steam turbine bucket. The rotation velocity is proportional to the mass flow rate of steam entering the steam turbine through valves and nozzles. Thus, it is very important to control the steam mass flow rate for the load following operation of power plants. Among various valves that control the steam turbine, the control valve is most significant. The steam flow rate is determined by the area formed by the stem disk and the seat of the control valve. While the ideal control valve linearly controls the steam mass flow rate with its stem lift, the real control valve has various flow characteristic curves pursuant to the stem lift type. Thus, flow characteristic curves are needed to precisely design the control valves manufactured for the operating conditions of nuclear power plants. OMEGA (Optimized Multidimensional Experiment Geometric Apparatus) was built to experimentally study the flow characteristics of steam flowing inside the control valve. The Widows' Creek type control valve was selected for reference. Air was selected as the working fluid in the OMEGA loop to exclude the condensation effect in this simplified approach. Flow characteristic curves were plotted by calculating the ratio of the measured mass flow rate versus the theoretical mass flow rate of the air. The flow characteristic curves are expected to be utilized to accurately design and operate the control valve for fossil as well as nuclear plants. (authors)

  1. Synthetic perspective optical flow: Influence on pilot control tasks

    NASA Technical Reports Server (NTRS)

    Bennett, C. Thomas; Johnson, Walter W.; Perrone, John A.; Phatak, Anil V.

    1989-01-01

    One approach used to better understand the impact of visual flow on control tasks has been to use synthetic perspective flow patterns. Such patterns are the result of apparent motion across a grid or random dot display. Unfortunately, the optical flow so generated is based on a subset of the flow information that exists in the real world. The danger is that the resulting optical motions may not generate the visual flow patterns useful for actual flight control. Researchers conducted a series of studies directed at understanding the characteristics of synthetic perspective flow that support various pilot tasks. In the first of these, they examined the control of altitude over various perspective grid textures (Johnson et al., 1987). Another set of studies was directed at studying the head tracking of targets moving in a 3-D coordinate system. These studies, parametric in nature, utilized both impoverished and complex virtual worlds represented by simple perspective grids at one extreme, and computer-generated terrain at the other. These studies are part of an applied visual research program directed at understanding the design principles required for the development of instruments displaying spatial orientation information. The experiments also highlight the need for modeling the impact of spatial displays on pilot control tasks.

  2. Studies of turbulent shear flows and their control

    NASA Technical Reports Server (NTRS)

    Liu, Joseph T. C.

    1992-01-01

    The intent of the original proposal and the work carried out under the grant was to explore the instabilities of turbulent free shear flows of an incompressible fluid. The purpose for doing so was that coherent instabilities are susceptible to control via upstream forcing and because at sufficient finite amplitudes, the coherent modes enter into nonlinear interactions with the mean motion and thus, through such nonlinear interactions, the control of mixing and of mean flow spreading can be effected through the control of the coherent structures.

  3. Semitoroidal-diaphragm cavitating valve designed for bipropellant flow control

    NASA Technical Reports Server (NTRS)

    Young, A. L.

    1969-01-01

    Valve controls the flow of bipropellant liquids in rocket engines. Throttling and cavitation of the liquids are controlled by axial deflections of a semitoroidal metal diaphram. The valve is highly resistant to corrosion and leakage, and should be useful in food processing and chemical industries.

  4. Experimental Study on the Unified Power Flow Controller

    NASA Astrophysics Data System (ADS)

    Matsuki, Junya; Hayashi, Yasuhiro; Kitajima, Shunsuke; Takahashi, Masahiro; Murata, Kenji

    This paper presents the results of experimental study on the performance of a Unified Power Flow Controller (UPFC), one of the FACTS (Flexible AC Transmission Systems) controllers. A laboratory-scale UPFC was manufactured and installed on a laboratory electric power system to investigate its multifunctional capabilities as a power flow controller. The UPFC consists of two 4.5kVA, 200V back-to-back voltage-sourced converters, labeled “Converter 1" and “Converter 2", operated from a common DC link provided by a DC storage capacitor of 380V. It can provide independent control of both the real and reactive power flow in the line. Tests were performed to examine the capabilities of UPFC, under one-machine connected to an infinite-bus system. Steady-state responses under various kinds of operating conditions were measured and analyzed.

  5. Summary of Data from the Fifth AIAA CFD Drag Prediction Workshop

    NASA Technical Reports Server (NTRS)

    Levy, David W.; Laflin, Kelly R.; Tinoco, Edward N.; Vassberg, John C.; Mani, Mori; Rider, Ben; Rumsey, Chris; Wahls, Richard A.; Morrison, Joseph H.; Brodersen, Olaf P.; Crippa, Simone; Mavriplis, Dimitri J.; Murayama, Mitsuhiro

    2013-01-01

    Results from the Fifth AIAA CFD Drag Prediction Workshop (DPW-V) are presented. As with past workshops, numerical calculations are performed using industry-relevant geometry, methodology, and test cases. This workshop focused on force/moment predictions for the NASA Common Research Model wing-body configuration, including a grid refinement study and an optional buffet study. The grid refinement study used a common grid sequence derived from a multiblock topology structured grid. Six levels of refinement were created resulting in grids ranging from 0.64x10(exp 6) to 138x10(exp 6) hexahedra - a much larger range than is typically seen. The grids were then transformed into structured overset and hexahedral, prismatic, tetrahedral, and hybrid unstructured formats all using the same basic cloud of points. This unique collection of grids was designed to isolate the effects of grid type and solution algorithm by using identical point distributions. This study showed reduced scatter and standard deviation from previous workshops. The second test case studied buffet onset at M=0.85 using the Medium grid (5.1x106 nodes) from the above described sequence. The prescribed alpha sweep used finely spaced intervals through the zone where wing separation was expected to begin. Some solutions exhibited a large side of body separation bubble that was not observed in the wind tunnel results. An optional third case used three sets of geometry, grids, and conditions from the Turbulence Model Resource website prepared by the Turbulence Model Benchmarking Working Group. These simple cases were intended to help identify potential differences in turbulence model implementation. Although a few outliers and issues affecting consistency were identified, the majority of participants produced consistent results.

  6. Experimental Studies of Low-Pressure Turbine Flows and Flow Control

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.

    2012-01-01

    This report summarizes research performed in support of the NASA Glenn Research Center (GRC) Low-Pressure Turbine (LPT) Flow Physics Program. The work was performed experimentally at the U.S. Naval Academy faculties. The geometry corresponded to "Pak B" LPT airfoil. The test section simulated LPT flow in a passage. Three experimental studies were performed: (a) Boundary layer measurements for ten baseline cases under high and low freestream turbulence conditions at five Reynolds numbers of 25,000, 50,000, 100,000, 200,000, and 300,000, based on passage exit velocity and suction surface wetted length; (b) Passive flow control studies with three thicknesses of two-dimensional bars, and two heights of three-dimensional circular cylinders with different spanwise separations, at same flow conditions as the 10 baseline cases; (c) Active flow control with oscillating synthetic (zero net mass flow) vortex generator jets, for one case with low freestream turbulence and a low Reynolds number of 25,000. The Passive flow control was successful at controlling the separation problem at low Reynolds numbers, with varying degrees of success from case to case and varying levels of impact at higher Reynolds numbers. The active flow control successfully eliminated the large separation problem for the low Reynolds number case. Very detailed data was acquired using hot-wire anemometry, including single and two velocity components, integral boundary layer quantities, turbulence statistics and spectra, turbulent shear stresses and their spectra, and intermittency, documenting transition, separation and reattachment. Models were constructed to correlate the results. The report includes a summary of the work performed and reprints of the publications describing the various studies.

  7. Blood flow controls bone vascular function and osteogenesis

    PubMed Central

    Ramasamy, Saravana K.; Kusumbe, Anjali P.; Schiller, Maria; Zeuschner, Dagmar; Bixel, M. Gabriele; Milia, Carlo; Gamrekelashvili, Jaba; Limbourg, Anne; Medvinsky, Alexander; Santoro, Massimo M.; Limbourg, Florian P.; Adams, Ralf H.

    2016-01-01

    While blood vessels play important roles in bone homeostasis and repair, fundamental aspects of vascular function in the skeletal system remain poorly understood. Here we show that the long bone vasculature generates a peculiar flow pattern, which is important for proper angiogenesis. Intravital imaging reveals that vessel growth in murine long bone involves the extension and anastomotic fusion of endothelial buds. Impaired blood flow leads to defective angiogenesis and osteogenesis, and downregulation of Notch signalling in endothelial cells. In aged mice, skeletal blood flow and endothelial Notch activity are also reduced leading to decreased angiogenesis and osteogenesis, which is reverted by genetic reactivation of Notch. Blood flow and angiogenesis in aged mice are also enhanced on administration of bisphosphonate, a class of drugs frequently used for the treatment of osteoporosis. We propose that blood flow and endothelial Notch signalling are key factors controlling ageing processes in the skeletal system. PMID:27922003

  8. Microfluidic Device for Studying Controllable Hydrodynamic Flow Induced Cellular Responses.

    PubMed

    Zheng, Chunhong; Zhang, Xiannian; Li, Chunmei; Pang, Yuhong; Huang, Yanyi

    2017-03-07

    Hydrodynamic flow is an essential stimulus in many cellular functions, regulating many mechanical sensitive pathways and closely associating with human health status and diseases. The flow pattern of blood in vessels is the key factor in causing atherosclerosis. Hemodynamics has great effect on endothelial cells' gene expression and biological functions. There are various tools that can be used for studying flow-induced cellular responses but most of them are either bulky or lack precise controllability. We develop an integrated microfluidic device that can precisely generate different flow patterns to human endothelial cells cultured on-chip. We monitored cell morphology and used small-input RNA-seq technology to depict the transcriptome profiles of human umbilical vein endothelial cells under uni- or bidirectional flow. Such integrated and miniatured device has greatly facilitated our understanding of endothelial functions with shear stimulus, not only providing new data on the transcriptomic scale but also building the connection between cell phenotypic changes and expression alternations.

  9. Sap flow sensors: construction, quality control and comparison.

    PubMed

    Davis, Tyler W; Kuo, Chen-Min; Liang, Xu; Yu, Pao-Shan

    2012-01-01

    This work provides a design for two types of sensors, based on the thermal dissipation and heat ratio methods of sap flow calculation, for moderate to large scale deployments for the purpose of monitoring tree transpiration. These designs include a procedure for making these sensors, a quality control method for the final products, and a complete list of components with vendors and pricing information. Both sensor designs were field tested alongside a commercial sap flow sensor to assess their performance and show the importance for quality controlling the sensor outputs. Results show that for roughly 2% of the cost of commercial sensors, self-made sap flow sensors can provide acceptable estimates of the sap flow measurements compared to the commercial sensors.

  10. Oscillatory control of sample dispersion in a continuous flow system.

    PubMed

    Bruno, H; Andrade, F; Iñón, F; Tudino, M; Troccoli, O

    2001-03-01

    A new strategy for the instrumental control of sample dispersion in continuous flow systems is presented. The method is based on shaking a loosely held straight reactor while the sample travels through the flow injection manifold. This external disturbance yields a sample transport more similar to the plug flow type because of the changes promoted on the flow pattern. Up to a three-fold increase in peak height, a comparable reduction in peak width and a more Gaussian peak profile are observed when the signals obtained with the shaken reactor are compared with those obtained with the same reactor but static. Improvements in the analytical performance as a function of different operational variables are shown for systems with or without a chemical reaction. Analytical implications and possible uses are discussed since this strategy allows the control of dispersion by simply selecting the frequency and amplitude of oscillation.

  11. Combustor air flow control method for fuel cell apparatus

    DOEpatents

    Clingerman, Bruce J.; Mowery, Kenneth D.; Ripley, Eugene V.

    2001-01-01

    A method for controlling the heat output of a combustor in a fuel cell apparatus to a fuel processor where the combustor has dual air inlet streams including atmospheric air and fuel cell cathode effluent containing oxygen depleted air. In all operating modes, an enthalpy balance is provided by regulating the quantity of the air flow stream to the combustor to support fuel cell processor heat requirements. A control provides a quick fast forward change in an air valve orifice cross section in response to a calculated predetermined air flow, the molar constituents of the air stream to the combustor, the pressure drop across the air valve, and a look up table of the orifice cross sectional area and valve steps. A feedback loop fine tunes any error between the measured air flow to the combustor and the predetermined air flow.

  12. Sap Flow Sensors: Construction, Quality Control and Comparison

    PubMed Central

    Davis, Tyler W.; Kuo, Chen-Min; Liang, Xu; Yu, Pao-Shan

    2012-01-01

    This work provides a design for two types of sensors, based on the thermal dissipation and heat ratio methods of sap flow calculation, for moderate to large scale deployments for the purpose of monitoring tree transpiration. These designs include a procedure for making these sensors, a quality control method for the final products, and a complete list of components with vendors and pricing information. Both sensor designs were field tested alongside a commercial sap flow sensor to assess their performance and show the importance for quality controlling the sensor outputs. Results show that for roughly 2% of the cost of commercial sensors, self-made sap flow sensors can provide acceptable estimates of the sap flow measurements compared to the commercial sensors. PMID:22368504

  13. Lockheed laminar-flow control systems development and applications

    NASA Technical Reports Server (NTRS)

    Lange, Roy H.

    1987-01-01

    Progress is summarized from 1974 to the present in the practical application of laminar-flow control (LFC) to subsonic transport aircraft. Those efforts included preliminary design system studies of commercial and military transports and experimental investigations leading to the development of the leading-edge flight test article installed on the NASA JetStar flight test aircraft. The benefits of LFC on drag, fuel efficiency, lift-to-drag ratio, and operating costs are compared with those for turbulent flow aircraft. The current activities in the NASA Industry Laminar-Flow Enabling Technologies Development contract include summaries of activities in the Task 1 development of a slotted-surface structural concept using advanced aluminum materials and the Task 2 preliminary conceptual design study of global-range military hybrid laminar flow control (HLFC) to obtain data at high Reynolds numbers and at Mach numbers representative of long-range subsonic transport aircraft operation.

  14. Dielectric Barrier Discharge control on an unstarting supersonic flow

    NASA Astrophysics Data System (ADS)

    Im, Seong-Kyun; Do, Hyungrok; Bak, Moonsoo; Cappelli, Mark

    2011-10-01

    The control of unstarting supersonic model inlet flow using Dielectric Barrier Discharge (DBD) is experimentally demonstrated at Mach 4.7 flow condition. Planar Laser Rayleigh Scattering (PLRS) technique is utilized to visualize important flow features, such as boundary layers and shockwaves, at low static temperature (~60 K) and pressure (~1 kPa) freestream condition. The unstart which is initiated by jet injection in three different model inlet flow, a laminar boundary layer, tripped boundary layer without actuation, and tripped boundary layer with actuation, is demonstrated with PLRS technique. The delay of unstart process is observed through the DBD actuation of the tripped boundary layer when a single DBD actuator pair is oriented parallel to the freestream flow, generates spanwise disturbances. However, this actuation on unstart process is limited to a region of actuation. The control of unstarting supersonic model inlet flow using Dielectric Barrier Discharge (DBD) is experimentally demonstrated at Mach 4.7 flow condition. Planar Laser Rayleigh Scattering (PLRS) technique is utilized to visualize important flow features, such as boundary layers and shockwaves, at low static temperature (~60 K) and pressure (~1 kPa) freestream condition. The unstart which is initiated by jet injection in three different model inlet flow, a laminar boundary layer, tripped boundary layer without actuation, and tripped boundary layer with actuation, is demonstrated with PLRS technique. The delay of unstart process is observed through the DBD actuation of the tripped boundary layer when a single DBD actuator pair is oriented parallel to the freestream flow, generates spanwise disturbances. However, this actuation on unstart process is limited to a region of actuation. This material is based upon work supported by the Department of Energy under Award Number(s)DE-FC52-08NA28614.

  15. Improving wind turbine array efficiency through active flow control

    NASA Astrophysics Data System (ADS)

    Velarde, John-Michael; Wang, Guannan; Shea, Patrick; Glauser, Mark; Castillo, Luciano

    2013-11-01

    We attempted to demonstrate the capability of instrumenting three wind turbine blades with an air delivery system that provided active flow control in an effort to improve turbine performance in the presence of the wake turbulence that is inherent in a turbine array. Presently, turbines are being designed for set conditions, such as steady incoming wind and a set velocity profile, however conditions can be drastically different in the field - thus causing poor performance from the turbines. The blades were instrumented with pressure transducers which measured the suction surface pressure; the sensor setup was such that three unique blade configurations existed: spanwise sensors, chord-wise sensors, and a reference sensor. The compressed air was delivered through a rotary union connected to the turbine hub with tubing attached to the suction side of the blades. The primary purpose of this test was to demonstrate the ability to deliver air to a rotating frame for active flow control. We collected data under three test conditions using an open-section wind tunnel, courtesy of Texas Tech University: static with no flow control, rotation with no flow control, and rotation with active flow control.

  16. Closed-loop Separation Control Using Oscillatory Flow Excitation

    NASA Technical Reports Server (NTRS)

    Allan, Brian G.; Juang, Jer-Nan; Raney, David L.; Seifert, Avi; Pack, latunia G.; Brown, Donald E.

    2000-01-01

    Design and implementation of a digital feedback controller for a flow control experiment was performed. The experiment was conducted in a cryogenic pressurized wind tunnel on a generic separated configuration at a chord Reynolds number of 16 million and a Mach number of 0.25. The model simulates the upper surface of a 20% thick airfoil at zero angle-of-attack. A moderate favorable pressure gradient, up to 55% of the chord, is followed by a severe adverse pressure gradient which is relaxed towards the trailing edge. The turbulent separation bubble, behind the adverse pressure gradient, is then reduced by introducing oscillatory flow excitation just upstream of the point of flow separation. The degree of reduction in the separation region can be controlled by the amplitude of the oscillatory excitation. A feedback controller was designed to track a given trajectory for the desired degree of flow reattachment and to improve the transient behavior of the flow system. Closed-loop experiments demonstrated that the feedback controller was able to track step input commands and improve the transient behavior of the open-loop response.

  17. Mass-flow-rate-controlled fluid flow in nanochannels by particle insertion and deletion

    NASA Astrophysics Data System (ADS)

    Barclay, Paul L.; Lukes, Jennifer R.

    2016-12-01

    A nonequilibrium molecular dynamics method to induce fluid flow in nanochannels, the insertion-deletion method (IDM), is introduced. IDM inserts and deletes particles within distinct regions in the domain, creating locally high and low pressures. The benefits of IDM are that it directly controls a physically meaningful quantity, the mass flow rate, allows for pressure and density gradients to develop in the direction of flow, and permits treatment of complex aperiodic geometries. Validation of IDM is performed, yielding good agreement with the analytical solution of Poiseuille flow in a planar channel. Comparison of IDM to existing methods indicates that it is best suited for gases, both because it intrinsically accounts for compressibility effects on the flow and because the computational cost of particle insertion is lowest for low-density fluids.

  18. Mass-flow-rate-controlled fluid flow in nanochannels by particle insertion and deletion.

    PubMed

    Barclay, Paul L; Lukes, Jennifer R

    2016-12-01

    A nonequilibrium molecular dynamics method to induce fluid flow in nanochannels, the insertion-deletion method (IDM), is introduced. IDM inserts and deletes particles within distinct regions in the domain, creating locally high and low pressures. The benefits of IDM are that it directly controls a physically meaningful quantity, the mass flow rate, allows for pressure and density gradients to develop in the direction of flow, and permits treatment of complex aperiodic geometries. Validation of IDM is performed, yielding good agreement with the analytical solution of Poiseuille flow in a planar channel. Comparison of IDM to existing methods indicates that it is best suited for gases, both because it intrinsically accounts for compressibility effects on the flow and because the computational cost of particle insertion is lowest for low-density fluids.

  19. Numerical laser energy deposition on supersonic cavity flow and sensor placement strategies to control the flow.

    PubMed

    Yilmaz, Ibrahim; Aradag, Selin

    2013-01-01

    In this study, the impact of laser energy deposition on pressure oscillations and relative sound pressure levels (SPL) in an open supersonic cavity flow is investigated. Laser energy with a magnitude of 100 mJ is deposited on the flow just above the cavity leading edge and up to 7 dB of reduction is obtained in the SPL values along the cavity back wall. Additionally, proper orthogonal decomposition (POD) method is applied to the x-velocity data obtained as a result of computational fluid dynamics simulations of the flow with laser energy deposition. Laser is numerically modeled using a spherically symmetric temperature distribution. By using the POD results, the effects of laser energy on the flow mechanism are presented. A one-dimensional POD methodology is applied to the surface pressure data to obtain critical locations for the placement of sensors for real time flow control applications.

  20. On the control of a canonical separated flow

    NASA Astrophysics Data System (ADS)

    Griffin, John C.

    Flow separation is generally an undesirable phenomenon that produces adverse effects to ideal aerodynamic performance. Control of ow separation is a complex problem and thus a popular area of research. A common obstacle is the lack of understanding of the complex fluid mechanics in cases of ow separation, evident by the substantial amount of ow control achieved through trial-and-error methods. The purpose of this work is to better understand the nature of separation for improved active control methods, which includes closed-loop control via reduced order methods. Control of a canonical separation problem, with the key features of separated flow, is achieved at a chord Reynolds number of 105. Separation is created on a at plate model, void of curvature that would otherwise include effects particular to the type of aerodynamic body. The characteristics of the imposed separation are evaluated with the intent of having a nominally two-dimensional separation, with the same essential flow characteristics of a more traditionally stalled airfoil. Results provide a reduced-order estimation technique that is used to identify global, dynamic modes through experimental measurements. Reattachment of the baseline separation is first achieved in open-loop control via ZNMF actuation. Efficient reattachment is reached by targeting the identified characteristic flow frequencies, which is able to reattach the separated flow with less than a quarter of the control effort as a comparison case with high-frequency forcing. The baseline and control results are used to identify a reduced-order model suitable for closed-loop control, with benefits of set-point tracking and full boundary layer attachment with minimum control effort.

  1. Thermal Mechanisms for High Amplitude Aerodynamic Flow Control (YIP 2012)

    DTIC Science & Technology

    2016-04-15

    distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The potential of thermal perturbations (i.e. energy deposition) and subsequent compression... energy deposition for active flow control. The basic nature of this problem requires examination of a canonical flow system and turbulent shear...theory. Our most important finding is that the required energy deposition is related to an as yet to be determined measure of the initial shear layer

  2. Simulation, Control, and Applications for Flow and Scattering Problems

    DTIC Science & Technology

    2015-04-10

    and Optimization (08 2011) Kazufumi Ito, Tomoya Takeuchi. CIP immersed interface methods for hyperbolic equations withdiscontinuous coefficients ...augmented variables along the interface between the fluid flow and the porous media so that the problem can be decoupled as several Poisson equations . The...computational fluid dynamics and control of incompressible flows modeled by Navier-Stokes equations . Under the support of the current ARO grant, we

  3. Computational Methods for Feedback Controllers for Aerodynamics Flow Applications

    DTIC Science & Technology

    2007-08-15

    include the massively separated flow around an F-1i5E at 650 angle of attack reported by Forsythe et a/. (2004) (the first eddy-resolving simulation...to one step prediction, of MIMO (multi-input, multi- output) systems. A schematic representation of the feed-forward ANN-ARX network topology is...present, and can also accommodate multiple actuator interaction allowing for MIMO control. We did not intend it to be used for random turbulent flows, but

  4. Shock Boundary Layer Interaction Flow Control with Micro Vortex Generators

    DTIC Science & Technology

    2011-05-01

    hole Pitot rake 6o x vg variable φ cylinder mounted on the centre-line 380 M ∞ =1.4...constant mass flow through the slots. shock holder near-normal shock μVGs 123 143 14 hole Pitot rake 6o xvg variable φ cylinder mounted on the centre-line... Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39-18 Shock Boundary Layer Interaction Flow Control with

  5. Fluidic Control of Nozzle Flow: Some Performance Measurements

    NASA Technical Reports Server (NTRS)

    Federspiel, John; Bangert, Linda; Wing, David; Hawkes, Tim

    1995-01-01

    Results are presented of an experimental program that investigated the use of a secondary air stream to control the amount of flow through a convergent-divergent nozzle. These static tests utilized high pressure, ambient temperature air that was injected at the throat of the nozzle through an annular slot. Multiple injection slot sizes and injection angles were tested. The introduction of secondary flow was made in an opposing direction to the primary flow and the resulting flow field caused the primary stream to react as though the physical throat size had been reduced. The percentage reduction in primary flow rate was generally about twice the injected flow rate. The most effective throttling was achieved by injecting through the smallest slot in an orientation most nearly opposed to the approaching primary flow. Thrust edliciency, as measured by changes in nozzle thrust coefficient, was highest at high nozzle pressure ratios, NPR. The static test results agreed with predictions obtained prior from PABSD, a fully viscous computational fluid dynamics program. Since use of such an injection system on gas turbine engine exhaust nozzles would be primarily at high NPRs, it was concluded that fluidic control holds promise for reducing nozzle weight and complexity on future systems.

  6. Jet flow and premixed jet flame control by plasma swirler

    NASA Astrophysics Data System (ADS)

    Li, Gang; Jiang, Xi; Zhao, Yujun; Liu, Cunxi; Chen, Qi; Xu, Gang; Liu, Fuqiang

    2017-04-01

    A swirler based on dielectric barrier discharge plasma actuators is designed and its effectiveness in both jet flow and premixed jet flame control is demonstrated. In contrast to traditional spanwise-oriented actuators, plasma actuators are placed along the axial direction of the injector to induce a circumferential velocity to the main flow and create a swirl flow without any insertion or moving part. In the DBD plasma swirl injector, the discharge does not ignite the mixture nor does it induce flashback. Flame visualization is obtained by cameras while velocity profiles are obtained by Laser Doppler Anemometry measurements. The results obtained indicate the effectiveness of the new design.

  7. Light control of the flow of phototactic microswimmer suspensions.

    PubMed

    Garcia, Xabel; Rafaï, Salima; Peyla, Philippe

    2013-03-29

    Some microalgae are sensitive to light intensity gradients. This property is known as phototaxis: The algae swim toward a light source (positive phototaxis). We use this property to control the motion of microalgae within a Poiseuille flow using light. The combination of flow vorticity and phototaxis results in a concentration of algae around the center of the flow. Intermittent light exposure allows analysis of the dynamics of this phenomenon and its reversibility. With this phenomenon, we hope to pave the way toward new algae concentration techniques (a bottleneck challenge in biofuel algal production) and toward the improvement of pollutant biodetector technology.

  8. Light Control of the Flow of Phototactic Microswimmer Suspensions

    NASA Astrophysics Data System (ADS)

    Garcia, Xabel; Rafaï, Salima; Peyla, Philippe

    2013-03-01

    Some microalgae are sensitive to light intensity gradients. This property is known as phototaxis: The algae swim toward a light source (positive phototaxis). We use this property to control the motion of microalgae within a Poiseuille flow using light. The combination of flow vorticity and phototaxis results in a concentration of algae around the center of the flow. Intermittent light exposure allows analysis of the dynamics of this phenomenon and its reversibility. With this phenomenon, we hope to pave the way toward new algae concentration techniques (a bottleneck challenge in biofuel algal production) and toward the improvement of pollutant biodetector technology.

  9. Guidance of Autonomous Aerospace Vehicles for Vertical Soft Landing using Nonlinear Control Theory

    DTIC Science & Technology

    2015-08-11

    Chowdhary et al. Chowdhary et al. [ 2012 ] have experimented and presented concurrent learning MRAC for outer-loop control and PD based controller for...In AIAA Guidance, Navigation, and Control Conference (GNC),(Minneapolis, MN), AIAA, 2012 . John L Crassidis and John L Junkins. Optimal estimation of... Kim . Trajectory tracking control of quadrotor uav. In Control, Automation and Systems (ICCAS), 2011 11th International Conference on, pages 281–285

  10. Self-Contained Automated Methodology for Optimal Flow Control

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.; Gunzburger, Max D.; Nicolaides, Roy A.; Erlebacherl, Gordon; Hussaini, M. Yousuff

    1997-01-01

    This paper describes a self-contained, automated methodology for active flow control which couples the time-dependent Navier-Stokes system with an adjoint Navier-Stokes system and optimality conditions from which optimal states, i.e., unsteady flow fields and controls (e.g., actuators), may be determined. The problem of boundary layer instability suppression through wave cancellation is used as the initial validation case to test the methodology. Here, the objective of control is to match the stress vector along a portion of the boundary to a given vector; instability suppression is achieved by choosing the given vector to be that of a steady base flow. Control is effected through the injection or suction of fluid through a single orifice on the boundary. The results demonstrate that instability suppression can be achieved without any a priori knowledge of the disturbance, which is significant because other control techniques have required some knowledge of the flow unsteadiness such as frequencies, instability type, etc. The present methodology has been extended to three dimensions and may potentially be applied to separation control, re-laminarization, and turbulence control applications using one to many sensors and actuators.

  11. Flow monitoring and control system for injection wells

    DOEpatents

    Corey, John C.

    1993-01-01

    A system for monitoring and controlling the injection rate of fluid by an injection well of an in-situ remediation system for treating a contaminated groundwater plume. The well is fitted with a gated insert, substantially coaxial with the injection well. A plurality of openings, some or all of which are equipped with fluid flow sensors and gates, are spaced along the insert. The gates and sensors are connected to a surface controller. The insert may extend throughout part of, or substantially the entire length of the injection well. Alternatively, the insert may comprise one or more movable modules which can be positioned wherever desired along the well. The gates are opened part-way at the start of treatment. The sensors monitor and display the flow rate of fluid passing through each opening on a controller. As treatment continues, the gates are opened to increase flow in regions of lesser flow, and closed to decrease flow in regions of greater flow, thereby approximately equalizing the amount of fluid reaching each part of the plume.

  12. Flow monitoring and control system for injection wells

    DOEpatents

    Corey, J.C.

    1993-02-16

    A system for monitoring and controlling the injection rate of fluid by an injection well of an in-situ remediation system for treating a contaminated groundwater plume. The well is fitted with a gated insert, substantially coaxial with the injection well. A plurality of openings, some or all of which are equipped with fluid flow sensors and gates, are spaced along the insert. The gates and sensors are connected to a surface controller. The insert may extend throughout part of, or substantially the entire length of the injection well. Alternatively, the insert may comprise one or more movable modules which can be positioned wherever desired along the well. The gates are opened part-way at the start of treatment. The sensors monitor and display the flow rate of fluid passing through each opening on a controller. As treatment continues, the gates are opened to increase flow in regions of lesser flow, and closed to decrease flow in regions of greater flow, thereby approximately equalizing the amount of fluid reaching each part of the plume.

  13. Inlet Flow Control and Prediction Technologies for Embedded Propulsion Systems

    NASA Technical Reports Server (NTRS)

    McMillan, Michelle L.; Mackie, Scott A.; Gissen, Abe; Vukasinovic, Bojan; Lakebrink, Matthew T.; Glezer, Ari; Mani, Mori; Mace, James L.

    2011-01-01

    Fail-safe, hybrid, flow control (HFC) is a promising technology for meeting high-speed cruise efficiency, low-noise signature, and reduced fuel-burn goals for future, Hybrid-Wing-Body (HWB) aircraft with embedded engines. This report details the development of HFC technology that enables improved inlet performance in HWB vehicles with highly integrated inlets and embedded engines without adversely affecting vehicle performance. In addition, new test techniques for evaluating Boundary-Layer-Ingesting (BLI)-inlet flow-control technologies developed and demonstrated through this program are documented, including the ability to generate a BLI-like inlet-entrance flow in a direct-connect, wind-tunnel facility, as well as, the use of D-optimal, statistically designed experiments to optimize test efficiency and enable interpretation of results. Validated improvements in numerical analysis tools and methods accomplished through this program are also documented, including Reynolds-Averaged Navier-Stokes CFD simulations of steady-state flow physics for baseline, BLI-inlet diffuser flow, as well as, that created by flow-control devices. Finally, numerical methods were employed in a ground-breaking attempt to directly simulate dynamic distortion. The advances in inlet technologies and prediction tools will help to meet and exceed "N+2" project goals for future HWB aircraft.

  14. Controlling vibrational energy flow in liquid alkylbenzenes.

    PubMed

    Pein, Brandt C; Sun, Yuxiao; Dlott, Dana D

    2013-09-19

    Ultrafast infrared (IR) Raman spectroscopy was used to study vibrational energy in ϕ-S alkylbenzenes, where ϕ = C6H5 and substituents S were CH3- (toluene), (CH3)2CH- (isopropylbenzene, IPB), or (CH3)3C- (t-butylbenzene, TBB). Using methods described previously,1 the normal modes were classified as phenyl (ϕ), substituent (S), or global (G). IR pulses were tuned to find conditions that maximized the localization of initial CH-stretch excitations on ϕ or S. Anti-Stokes Raman spectroscopy measured transient energy content of Raman-active S, ϕ, and G modes, to determine the rates of phenyl to substituent (Φ → S) or substituent to phenyl (S → Φ) transfer during the first few picoseconds, when energy transfer was mainly intramolecular. Since phenyl CH-stretches were 90-130 cm(-1) uphill in energy from substituent CH-stretches, of interest were S → Φ processes where molecular structure and local couplings were more important than energy differences. The Φ → S process efficiencies were small and about equal with all three substituents. The S → Φ transfer efficiencies could be increased by increasing substituent size. This was opposite to what would be predicted on the basis of the larger density of states of larger substituents, and it provides a path toward controlling forward-to-backward vibrational energy transfer ratios. The S → Φ transfer efficiency is understood as resulting from an increase in the local anharmonic couplings. A heavier substituent, when vibrating, transfers energy more effectively to the phenyl group.

  15. Research in Natural Laminar Flow and Laminar-Flow Control, part 3

    NASA Technical Reports Server (NTRS)

    Hefner, Jerry N. (Compiler); Sabo, Frances E. (Compiler)

    1987-01-01

    Part 3 of the Symposium proceedings contains papers addressing advanced airfoil development, flight research experiments, and supersonic transition/laminar flow control research. Specific topics include the design and testing of natural laminar flow (NLF) airfoils, NLF wing gloves, and NLF nacelles; laminar boundary-layer stability over fuselage forebodies; the design of low noise supersonic/hypersonic wind tunnels; and boundary layer instability mechanisms on swept leading edges at supersonic speeds.

  16. Active Flow Control on a Boundary-Layer-Ingesting Inlet

    NASA Technical Reports Server (NTRS)

    Gorton, Susan Althoff; Owens, Lewis R.; Jenkins, Luther N.; Allan, Brian G.; Schuster, Ernest P.

    2004-01-01

    Boundary layer ingestion (BLI) is explored as means to improve overall system performance for Blended Wing Body configuration. The benefits of BLI for vehicle system performance benefit are assessed with a process derived from first principles suitable for highly-integrated propulsion systems. This performance evaluation process provides framework within which to assess the benefits of an integrated BLI inlet and lays the groundwork for higher-fidelity systems studies. The results of the system study show that BLI provides a significant improvement in vehicle performance if the inlet distortion can be controlled, thus encouraging the pursuit of active flow control (AFC) as a BLI enabling technology. The effectiveness of active flow control in reducing engine inlet distortion was assessed using a 6% scale model of a 30% BLI offset, diffusing inlet. The experiment was conducted in the NASA Langley Basic Aerodynamics Research Tunnel with a model inlet designed specifically for this type of testing. High mass flow pulsing actuators provided the active flow control. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion was determined by 120 total pressure measurements located at the aerodynamic interface plane. The test matrix was limited to a maximum freestream Mach number of 0.15 with scaled mass flows through the inlet for that condition. The data show that the pulsed actuation can reduce distortion from 29% to 4.6% as measured by the circumferential distortion descriptor DC60 using less than 1% of inlet mass flow. Closed loop control of the actuation was also demonstrated using a sidewall surface static pressure as the response sensor.

  17. (NTF) National Transonic Facility Test 213-SFW Flow Control II,

    NASA Image and Video Library

    2012-11-19

    (NTF) National Transonic Facility Test 213-SFW Flow Control II, Fast-MAC Model: The fundamental Aerodynamics Subsonic Transonic-Modular Active Control (Fast-MAC) Model was tested for the 2nd time in the NTF. The objectives were to document the effects of Reynolds numbers on circulation control aerodynamics and to develop and open data set for CFD code validation. Image taken in building 1236, National Transonic Facility

  18. Flow and Noise Control: Toward a Closer Linkage

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Choudhari, Meelan M.; Joslin, Ronald D.

    2002-01-01

    Motivated by growing demands for aircraft noise reduction and for revolutionary new aerovehicle concepts, the late twentieth century witnessed the beginning of a shift from single-discipline research, toward an increased emphasis on harnessing the potential of flow and noise control as implemented in a more fully integrated, multidisciplinary framework. At the same time, technologies for developing radically new aerovehicles, which promise quantum leap benefits in cost, safety and performance benefits with environmental friendliness, have appeared on the horizon. Transitioning new technologies to commercial applications will also require coupling further advances in traditional areas of aeronautics with intelligent exploitation of nontraditional and interdisciplinary technologies. Physics-based modeling and simulation are crucial enabling capabilities for synergistic linkage of flow and noise control. In these very fundamental ways, flow and noise control are being driven to be more closely linked during the early design phases of a vehicle concept for optimal and mutual noise and performance benefits.

  19. Mobile Monolith Polymer Elements For Flow Control In Microfluidic Systems

    DOEpatents

    Hasselbrink, Jr., Ernest F.; Rehm, Jason E.; Shepodd, Timothy J.; Kirby, Brian J.

    2006-01-24

    A cast-in-place and lithographically shaped mobile, monolithic polymer element for fluid flow control in microfluidic devices and method of manufacture. Microfluid flow control devices, or microvalves that provide for control of fluid or ionic current flow can be made incorporating a cast-in-place, mobile monolithic polymer element, disposed within a microchannel, and driven by fluid pressure (either liquid or gas) against a retaining or sealing surface. The polymer elements are made by the application of lithographic methods to monomer mixtures formulated in such a way that the polymer will not bond to microchannel walls. The polymer elements can seal against pressures greater than 5000 psi, and have a response time on the order of milliseconds. By the use of energetic radiation it is possible to depolymerize selected regions of the polymer element to form shapes that cannot be produced by conventional lithographic patterning and would be impossible to machine.

  20. Mobile monolithic polymer elements for flow control in microfluidic devices

    DOEpatents

    Hasselbrink, Jr., Ernest F.; Rehm, Jason E.; Shepodd, Timothy J.; Kirby, Brian J.

    2005-11-11

    A cast-in-place and lithographically shaped mobile, monolithic polymer element for fluid flow control in microfluidic devices and method of manufacture. Microfluid flow control devices, or microvalves that provide for control of fluid or ionic current flow can be made incorporating a cast-in-place, mobile monolithic polymer element, disposed within a microchannel, and driven by fluid pressure (either liquid or gas) against a retaining or sealing surface. The polymer elements are made by the application of lithographic methods to monomer mixtures formulated in such a way that the polymer will not bond to microchannel walls. The polymer elements can seal against pressures greater than 5000 psi, and have a response time on the order of milliseconds. By the use of energetic radiation it is possible to depolymerize selected regions of the polymer element to form shapes that cannot be produced by conventional lithographic patterning and would be impossible to machine.

  1. Mobile monolithic polymer elements for flow control in microfluidic devices

    DOEpatents

    Hasselbrink, Jr., Ernest F.; Rehm, Jason E.; Shepodd, Timothy J.

    2004-08-31

    A cast-in-place and lithographically shaped mobile, monolithic polymer element for fluid flow control in microfluidic devices and method of manufacture. Microfluid flow control devices, or microvalves that provide for control of fluid or ionic current flow can be made incorporating a cast-in-place, mobile monolithic polymer element, disposed within a microchannel, and driven by either fluid or gas pressure against a retaining or sealing surface. The polymer elements are made by the application of lithographic methods to monomer mixtures formulated in such a way that the polymer will not bond to microchannel walls. The polymer elements can seal against pressures greater than 5000 psi, and have a response time on the order of milliseconds. By the use of energetic radiation it is possible to depolymerize selected regions of the polymer element to form shapes that cannot be produced by conventional lithographic patterning and would be impossible to machine.

  2. Network Adaptive Deadband: NCS Data Flow Control for Shared Networks

    PubMed Central

    Díaz-Cacho, Miguel; Delgado, Emma; Prieto, José A. G.; López, Joaquín

    2012-01-01

    This paper proposes a new middleware solution called Network Adaptive Deadband (NAD) for long time operation of Networked Control Systems (NCS) through the Internet or any shared network based on IP technology. The proposed middleware takes into account the network status and the NCS status, to improve the global system performance and to share more effectively the network by several NCS and sensor/actuator data flows. Relationship between network status and NCS status is solved with a TCP-friendly transport flow control protocol and the deadband concept, relating deadband value and transmission throughput. This creates a deadband-based flow control solution. Simulation and experiments in shared networks show that the implemented network adaptive deadband has better performance than an optimal constant deadband solution in the same circumstances. PMID:23208556

  3. Unsteady aerodynamics and flow control for flapping wing flyers

    NASA Astrophysics Data System (ADS)

    Ho, Steven; Nassef, Hany; Pornsinsirirak, Nick; Tai, Yu-Chong; Ho, Chih-Ming

    2003-11-01

    The creation of micro air vehicles (MAVs) of the same general sizes and weight as natural fliers has spawned renewed interest in flapping wing flight. With a wingspan of approximately 15 cm and a flight speed of a few meters per second, MAVs experience the same low Reynolds number (10 4-10 5) flight conditions as their biological counterparts. In this flow regime, rigid fixed wings drop dramatically in aerodynamic performance while flexible flapping wings gain efficacy and are the preferred propulsion method for small natural fliers. Researchers have long realized that steady-state aerodynamics does not properly capture the physical phenomena or forces present in flapping flight at this scale. Hence, unsteady flow mechanisms must dominate this regime. Furthermore, due to the low flight speeds, any disturbance such as gusts or wind will dramatically change the aerodynamic conditions around the MAV. In response, a suitable feedback control system and actuation technology must be developed so that the wing can maintain its aerodynamic efficiency in this extremely dynamic situation; one where the unsteady separated flow field and wing structure are tightly coupled and interact nonlinearly. For instance, birds and bats control their flexible wings with muscle tissue to successfully deal with rapid changes in the flow environment. Drawing from their example, perhaps MAVs can use lightweight actuators in conjunction with adaptive feedback control to shape the wing and achieve active flow control. This article first reviews the scaling laws and unsteady flow regime constraining both biological and man-made fliers. Then a summary of vortex dominated unsteady aerodynamics follows. Next, aeroelastic coupling and its effect on lift and thrust are discussed. Afterwards, flow control strategies found in nature and devised by man to deal with separated flows are examined. Recent work is also presented in using microelectromechanical systems (MEMS) actuators and angular speed

  4. Aerodynamic control in compressible flow using microwave driven discharges

    NASA Astrophysics Data System (ADS)

    McAndrew, Brendan

    A new aerodynamic control scheme based on heating of the free stream flow is developed. The design, construction, and operation of a unique small scale wind tunnel to perform experiments involving this control scheme is detailed. Free stream heating is achieved by means of microwave driven discharges, and the resulting flow perturbations are used to alter the pressure distribution around a model in the flow. The experimental facility is also designed to allow the injection of an electron beam into the free stream for control of the discharge. Appropriate models for the fluid flow and discharge physics are developed, and comparisons of calculations based on those models are made with experimental results. The calculations have also been used to explore trends in parameters beyond the range possible in the experiments. The results of this work have been (1) the development of an operating facility capable of supporting free stream heat addition experiments in supersonic flow, (2) the development of a compatible instrumented model designed to make lift and drag measurements in a low pressure, high electrical noise environment, (3) a theoretical model to predict the change in breakdown threshold in the presence of an electron beam or other source of ionization, and (4) successful demonstration of aerodynamic control using free stream heat addition.

  5. Low-Speed Active Flow Control Laboratory Developed

    NASA Technical Reports Server (NTRS)

    Culley, Dennis E.; Bright, Michelle M.

    2005-01-01

    The future of aviation propulsion systems is increasingly focused on the application of control technologies to significantly enhance the performance of a new generation of air vehicles. Active flow control refers to a set of technologies that manipulate the flow of air and combustion gases deep within the confines of an engine to dynamically alter its performance during flight. By employing active flow control, designers can create engines that are significantly lighter, are more fuel efficient, and produce lower emissions. In addition, the operating range of an engine can be extended, yielding safer transportation systems. The realization of these future propulsion systems requires the collaborative development of many base technologies to achieve intelligent, embedded control at the engine locations where it will be most effective. NASA Glenn Research Center s Controls and Dynamics Technology Branch has developed a state-of-the-art low-speed Active Flow Control Laboratory in which emerging technologies can be integrated and explored in a flexible, low-cost environment. The facility allows the most promising developments to be prescreened and optimized before being tested on higher fidelity platforms, thereby reducing the cost of experimentation and improving research effectiveness.

  6. Does Kutta lift exist on a vortex ring in a uniform cross flow?

    NASA Astrophysics Data System (ADS)

    Lim, T. T.; Lua, K. B.; Thet, K.

    2008-05-01

    Past works [Y. K. Chang and A. D. Vakili, Phys. Fluids 7, 1583 (1995); R. Sau and K. Mahesh, AIAA Paper No. 2007-1316] show that a vortex ring ejected normal to a cross flow tilts and deforms as it propagates downstream, and they attribute this phenomenon to the Kutta lift or Magnus effect. Here, we show through a controlled experiment that there is no physical evidence of the existence of a Kutta lift when a fully developed vortex ring is exposed to a uniform cross flow. The observed phenomenon could be attributed to the modification of vorticity distribution of the vortex core due to the combined effect of the cross flow itself and the entrainment of boundary layer material during the formation of vortex ring.

  7. Phase effect on flow control for dielectric barrier plasma actuators

    SciTech Connect

    Singh, K. P.; Roy, Subrata

    2006-07-03

    Active control of flow has a wide range of applications. Specifically, mitigation of detachment due to the weakly ionized gas flow past a flat plate at an angle of attack is studied using two asymmetric sets of electrode pairs kept at a phase lag. The equations governing the dynamics of electrons, helium ions, and neutrals are solved self-consistently with charge-Poisson equation. The electrodynamic forces produced by two actuators largely depend on the relative phase between the potentials applied to rf electrodes and distance between them. A suitable phase and an optimum distance exist between two actuators for effective separation control.

  8. Discrete shunt controls in a Newton optimal power flow

    SciTech Connect

    Liu, W.H.E. ); Papa Iexopoulos, A.D. )

    1992-11-01

    Efficient and effective methods are needed for modeling discrete control actions in optimal power flow algorithms. Modeling discrete controls as continuous variables and rounding them off to the nearest steps is not satisfactory for controls with large step sizes such as shunt capacitors and reactors because it can significantly degrade optimality. Rigorous solution with discrete controls would involve a combinatorial research procedure which would be unacceptably slow for real-time applications. In this paper a penalty based discretization algorithm is proposed. The algorithm consistently provides a near optimal discrete solution for shunt controls without combinatorial search. It has been implemented in a production grade Newton optimal power flow program and tested on two actual power networks. Test results are reported.

  9. Pump and flow control subassembly of thermal control subsystem for photovoltaic power module

    NASA Astrophysics Data System (ADS)

    Motil, Brian; Santen, Mark A.

    The pump and flow control subassembly (PFCS) is an orbital replacement unit (ORU) on the Space Station Freedom photovoltaic power module (PVM). The PFCS pumps liquid ammonia at a constant rate of approximately 1170 kg/hr while providing temperature control by flow regulation between the radiator and the bypass loop. Also, housed within the ORU is an accumulator to compensate for fluid volumetric changes as well as the electronics and firmware for monitoring and control of the photovoltaic thermal control system (PVTCS). Major electronic functions include signal conditioning, data interfacing and motor control. This paper will provide a description of each major component within the PFCS along with performance test data. In addition, this paper will discuss the flow control algorithm and describe how the nickel hydrogen batteries and associated power electronics will be thermally controlled through regulation of coolant flow to the radiator.

  10. Pump and Flow Control Subassembly of Thermal Control Subsystem for Photovoltaic Power Module

    NASA Technical Reports Server (NTRS)

    Motil, Brian; Santen, Mark A.

    1993-01-01

    The pump and flow control subassembly (PFCS) is an orbital replacement unit (ORU) on the Space Station Freedom photovoltaic power module (PVM). The PFCS pumps liquid ammonia at a constant rate of approximately 1170 kg/hr while providing temperature control by flow regulation between the radiator and the bypass loop. Also, housed within the ORU is an accumulator to compensate for fluid volumetric changes as well as the electronics and firmware for monitoring and control of the photovoltaic thermal control system (PVTCS). Major electronic functions include signal conditioning, data interfacing and motor control. This paper will provide a description of each major component within the PFCS along with performance test data. In addition, this paper will discuss the flow control algorithm and describe how the nickel hydrogen batteries and associated power electronics will be thermally controlled through regulation of coolant flow to the radiator.

  11. Pump and Flow Control Subassembly of Thermal Control Subsystem for Photovoltaic Power Module

    NASA Technical Reports Server (NTRS)

    Motil, Brian; Santen, Mark A.

    1993-01-01

    The pump and flow control subassembly (PFCS) is an orbital replacement unit (ORU) on the Space Station Freedom photovoltaic power module (PVM). The PFCS pumps liquid ammonia at a constant rate of approximately 1170 kg/hr while providing temperature control by flow regulation between the radiator and the bypass loop. Also, housed within the ORU is an accumulator to compensate for fluid volumetric changes as well as the electronics and firmware for monitoring and control of the photovoltaic thermal control system (PVTCS). Major electronic functions include signal conditioning, data interfacing and motor control. This paper will provide a description of each major component within the PFCS along with performance test data. In addition, this paper will discuss the flow control algorithm and describe how the nickel hydrogen batteries and associated power electronics will be thermally controlled through regulation of coolant flow to the radiator.

  12. Experimental study of controlled tip disturbance effect on flow asymmetry

    NASA Technical Reports Server (NTRS)

    Degani, David; Tobak, Murray

    1992-01-01

    The effect on the asymmetric mean flow observed on pointed bodies of revolution at incidence of changing the size and location of a controlled disturbance as well as changes in angle of attack and flow conditions are evaluated experimentally. Flow visualization and side-force measurements are carried out for a generic ogive-cylinder body inclined at high angle of attack in a low-speed wind tunnel. For all angles of attack tested (30-60 deg), minute changes in the size or location of the controlled disturbance result in finite changes in the asymmetric flow field, even to the extent of reversing the sign of the side force or becoming almost symmetric. The process is reversible; returning the wire to an original position likewise restores the corresponding flow field and mean side force. The variation of side force with continuous variation of a perturbation's size or location remains continuous and single valued, even in the incidence range of 50 to 60 deg, where 'bistable' behavior of the asymmetric flow field is observed.

  13. Experimental study of controlled tip disturbance effect on flow asymmetry

    NASA Technical Reports Server (NTRS)

    Degani, David; Tobak, Murray

    1992-01-01

    The effect on the asymmetric mean flow observed on pointed bodies of revolution at incidence of changing the size and location of a controlled disturbance as well as changes in angle of attack and flow conditions are evaluated experimentally. Flow visualization and side-force measurements are carried out for a generic ogive-cylinder body inclined at high angle of attack in a low-speed wind tunnel. For all angles of attack tested (30-60 deg), minute changes in the size or location of the controlled disturbance result in finite changes in the asymmetric flow field, even to the extent of reversing the sign of the side force or becoming almost symmetric. The process is reversible; returning the wire to an original position likewise restores the corresponding flow field and mean side force. The variation of side force with continuous variation of a perturbation's size or location remains continuous and single valued, even in the incidence range of 50 to 60 deg, where 'bistable' behavior of the asymmetric flow field is observed.

  14. Formation of surface nanodroplets under controlled flow conditions

    PubMed Central

    Zhang, Xuehua; Lu, Ziyang; Tan, Huanshu; Bao, Lei; He, Yinghe; Sun, Chao; Lohse, Detlef

    2015-01-01

    Nanodroplets on a solid surface (i.e., surface nanodroplets) have practical implications for high-throughput chemical and biological analysis, lubrications, laboratory-on-chip devices, and near-field imaging techniques. Oil nanodroplets can be produced on a solid–liquid interface in a simple step of solvent exchange in which a good solvent of oil is displaced by a poor solvent. In this work, we experimentally and theoretically investigate the formation of nanodroplets by the solvent exchange process under well-controlled flow conditions. We find significant effects from the flow rate and the flow geometry on the droplet size. We develop a theoretical framework to account for these effects. The main idea is that the droplet nuclei are exposed to an oil oversaturation pulse during the exchange process. The analysis shows that the volume of the nanodroplets increases with the Peclet number Pe of the flow as ∝Pe3/4, which is in good agreement with our experimental results. In addition, at fixed flow rate and thus fixed Peclet number, larger and less homogeneously distributed droplets formed at less-narrow channels, due to convection effects originating from the density difference between the two solutions of the solvent exchange. The understanding from this work provides valuable guidelines for producing surface nanodroplets with desired sizes by controlling the flow conditions. PMID:26159418

  15. System and method for bidirectional flow and controlling fluid flow in a conduit

    DOEpatents

    Ortiz, M.G.

    1999-03-23

    A system for measuring bidirectional flow, including backflow, of fluid in a conduit is disclosed. The system utilizes a structural mechanism to create a pressure differential in the conduit. Pressure sensors are positioned upstream from the mechanism, at the mechanism, and downstream from the mechanism. Data from the pressure sensors are transmitted to a microprocessor or computer, and pressure differential detected between the pressure sensors is then used to calculate the backflow. Control signals may then be generated by the microprocessor or computer to shut off valves located in the conduit, upon the occurrence of backflow, or to control flow, total material dispersed, etc. in the conduit. 3 figs.

  16. System and method for bidirectional flow and controlling fluid flow in a conduit

    DOEpatents

    Ortiz, Marcos German

    1999-01-01

    A system for measuring bidirectional flow, including backflow, of fluid in a conduit. The system utilizes a structural mechanism to create a pressure differential in the conduit. Pressure sensors are positioned upstream from the mechanism, at the mechanism, and downstream from the mechanism. Data from the pressure sensors are transmitted to a microprocessor or computer, and pressure differential detected between the pressure sensors is then used to calculate the backflow. Control signals may then be generated by the microprocessor or computer to shut off valves located in the conduit, upon the occurrence of backflow, or to control flow, total material dispersed, etc. in the conduit.

  17. Closed-loop control of flow-induced cavity oscillations

    NASA Astrophysics Data System (ADS)

    Song, Qi

    Flow-induced cavity oscillations are a coupled flow-acoustic problem in which the inherent closed-loop system dynamics can lead to large unsteady pressure levels in and around the cavity, resulting in both broadband noise and discrete tones. This problem exists in many practical environments, such as landing gear bays and weapon delivery systems on aircraft, and automobile sunroofs and windows. Researchers in both fluid dynamics and controls have been working on this problem for more than fifty years. This is because not only is the physical nature of this problem rich and complex, but also it has become a standard test bed for controller deign and implementation in flow control. The ultimate goal of this research is to minimize the cavity acoustic tones and the broadband noise level over a range of freestream Mach numbers. Although open-loop and closed-loop control methodologies have been explored extensively in recent years, there are still some issues that need to be studied further. For example, a low-order theoretical model suitable for controller design does not exist. Most recent flow-induced cavity models are based either on Rossiter's semi-expirical formula or a proper orthogonal decomposition (POD) based models. These models cannot be implemented in adaptive controller design directly. In addition, closed-loop control of high subsonic and supersonic flows remains an unexplored area. In order to achieve these objectives, an analytical system model is first developed in this research. This analytical model is a transfer function based model and it can be used as a potential model for controller design. Then, a MIMO system identification algorithm is derived and combined with the generalized prediction control (GPC) algorithm. The resultant integration of adaptive system ID and GPC algorithms can potentially track nonstationary cavity dynamics and reduce the flow-induced oscillations. A novel piezoelectric-driven synthetic jet actuator array is designed for

  18. Wettability control on multiphase flow in patterned microfluidics

    NASA Astrophysics Data System (ADS)

    Juanes, R.; Zhao, B.; MacMinn, C. W.

    2016-12-01

    Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid-fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate's affinity to the injected fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms—cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)—responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge—from pore-filling to post-bridging—are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions.

  19. Wettability control on multiphase flow in patterned microfluidics

    PubMed Central

    Zhao, Benzhong; Juanes, Ruben

    2016-01-01

    Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid–fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate’s affinity to the invading fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms—cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)—responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge—from pore filling to postbridging—are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions. PMID:27559089

  20. Passive Flow Separation Control Mechanism Inspired by Shark Skin

    NASA Astrophysics Data System (ADS)

    Oakley, India; Lang, Amy

    2015-11-01

    The following experimental work seeks to examine shark scales as passive flow-actuated separation control mechanisms. It is hypothesized that the actuation of these scales can in fact reduce pressure drag by inhibiting flow reversal and thereby prevent flow separation. In order to examine this mechanism at a fundamental level, three-dimensional sharkskin scales were simplified and modeled as two-dimensional flaps. To further simplify the experiment, the flaps were observed within a laminar boundary layer. The laminar boundary layer was grown over a long flat plate that was placed inside a water tunnel. A rotating cylinder was also used to induce an unsteady, increasing adverse pressure gradient, which generated a reversing flow. In order to visualize the potential actuation of the two-dimensional flaps DPIV (digital particle image velocimetry) was utilized. Three main objectives for this work included, the actuation of the two-dimensional flaps, the resistance to a reversed flow as a result of flap actuation and the prevention of flow separation. However once the experiment was conducted the flaps did not perform as previously hypothesized. The adverse pressure gradient induced by the rotating cylinder did not produce a reversing flow powerful enough to actuate the flaps. NSF REU Site Award 1358991.

  1. Active flow control on a 1:4 car model

    NASA Astrophysics Data System (ADS)

    Heinemann, Till; Springer, Matthias; Lienhart, Hermann; Kniesburges, Stefan; Othmer, Carsten; Becker, Stefan

    2014-05-01

    Lift and drag of a passenger car are strongly influenced by the flow field around its rear end. The bluff body geometry produces a detached, transient flow which induces fluctuating forces on the body, affecting the rear axle, which may distress dynamic stability and comfort significantly. The investigations presented here deal with a 1:4 scale model of a simplified test car geometry that produces fluctuating lift and drag due to its strongly rounded rear geometry. To examine the influence of active flow control on this behavior, steady air jets were realized to exhaust from thin slots across the rear in three different configurations. Investigations were performed at and included the capturing of effective integral lift and drag, velocity measurements in the surrounding flow field with Laser Doppler Anemometry, surface pressure measurements and surface oil flow visualization on the rear. The flow field was found to be dominated by two longitudinal vortices, developing from the detachment of the flow at the upper C-pillar positions, and a recirculating, transverse vortex above the rear window. With an air jet emerging from a slot across the surface right below the rear window section, tangentially directed upstream toward the roof section, total lift could be reduced by more than 7 %, with rear axle lift reduction of about 5 % and negligible drag affection (1 %).

  2. Experimental Investigation of Flow Control in a Compact Inlet Duct

    NASA Astrophysics Data System (ADS)

    Debronsky, Brian; Amitay, Michael

    2012-11-01

    Attractive to aircraft designers are compact inlets, which implement curved flow paths from the air intake of the engine to the compressor face. A compromise must be made between the compactness of the inlet and its aerodynamic performance. The aerodynamic purpose of inlets is to decelerate the oncoming flow before reaching the engine while minimizing total pressure loss, unsteadiness and distortion. Low length-to-diameter ratio inlets have a high degree of curvature, which inevitably causes flow separation and secondary flows. To address this issue, active flow control was implemented on a compact (L/D = 1.6) inlet to improve its performance metrics. The experiments were conducted at a Mach number of 0.44, where the actuation from an array of skewed and pitched jets produced streamwise vortices opposite to the secondary flow structures. The actuation resulted in an improved pressure recovery at the aerodynamic interface plane (AIP), where both the strength of the secondary structures and the flow unsteadiness were significantly reduced. Northrop Grumman Corporation.

  3. Structural integrated sensor and actuator systems for active flow control

    NASA Astrophysics Data System (ADS)

    Behr, Christian; Schwerter, Martin; Leester-Schädel, Monika; Wierach, Peter; Dietzel, Andreas; Sinapius, Michael

    2016-04-01

    An adaptive flow separation control system is designed and implemented as an essential part of a novel high-lift device for future aircraft. The system consists of MEMS pressure sensors to determine the flow conditions and adaptive lips to regulate the mass flow and the velocity of a wall near stream over the internally blown Coanda flap. By the oscillating lip the mass flow in the blowing slot changes dynamically, consequently the momentum exchange of the boundary layer over a high lift flap required mass flow can be reduced. These new compact and highly integrated systems provide a real-time monitoring and manipulation of the flow conditions. In this context the integration of pressure sensors into flow sensing airfoils of composite material is investigated. Mechanical and electrical properties of the integrated sensors are investigated under mechanical loads during tensile tests. The sensors contain a reference pressure chamber isolated to the ambient by a deformable membrane with integrated piezoresistors connected as a Wheatstone bridge, which outputs voltage signals depending on the ambient pressure. The composite material in which the sensors are embedded consists of 22 individual layers of unidirectional glass fiber reinforced plastic (GFRP) prepreg. The results of the experiments are used for adapting the design of the sensors and the layout of the laminate to ensure an optimized flux of force in highly loaded structures primarily for future aeronautical applications. It can be shown that the pressure sensor withstands the embedding process into fiber composites with full functional capability and predictable behavior under stress.

  4. Effect of adaptive cruise control systems on traffic flow

    NASA Astrophysics Data System (ADS)

    Davis, L. C.

    2004-06-01

    The flow of traffic composed of vehicles that are equipped with adaptive cruise control (ACC) is studied using simulations. The ACC vehicles are modeled by a linear dynamical equation that has string stability. In platoons of all ACC vehicles, perturbations due to changes in the lead vehicle’s velocity do not cause jams. Simulations of merging flows near an onramp show that if the total incoming rate does not exceed the capacity of the single outgoing lane, free flow is maintained. With larger incoming flows, a state closely related to the synchronized flow phase found in manually driven vehicular traffic has been observed. This state, however, should not be considered congested because the flow is maximal for the density. Traffic composed of random sequences of ACC vehicles and manual vehicles has also been studied. At high speeds ( ˜30 m/s ) jamming occurs for concentrations of ACC vehicles of 10% or less. At 20% no jams are formed. The formation of jams is sensitive to the sequence of vehicles (ACC or manual). At lower speeds ( ˜15 m/s ) , no critical concentration for complete jam suppression is found. Rather, the average velocity in the pseudojam region increases with increasing ACC concentration. Mixing 50% ACC vehicles randomly with manually driven vehicles on the primary lane in onramp simulations shows only modestly reduced travel times and larger flow rates.

  5. Wettability control on multiphase flow in patterned microfluidics

    NASA Astrophysics Data System (ADS)

    Juanes, Ruben; Zhao, Benzhong; MacMinn, Christopher

    2016-11-01

    Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid-fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate's affinity to the injected fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms-cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)-responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge-from pore-filling to post-bridging-are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions.

  6. Effect of adaptive cruise control systems on traffic flow.

    PubMed

    Davis, L C

    2004-06-01

    The flow of traffic composed of vehicles that are equipped with adaptive cruise control (ACC) is studied using simulations. The ACC vehicles are modeled by a linear dynamical equation that has string stability. In platoons of all ACC vehicles, perturbations due to changes in the lead vehicle's velocity do not cause jams. Simulations of merging flows near an onramp show that if the total incoming rate does not exceed the capacity of the single outgoing lane, free flow is maintained. With larger incoming flows, a state closely related to the synchronized flow phase found in manually driven vehicular traffic has been observed. This state, however, should not be considered congested because the flow is maximal for the density. Traffic composed of random sequences of ACC vehicles and manual vehicles has also been studied. At high speeds (approximately 30 m/s ) jamming occurs for concentrations of ACC vehicles of 10% or less. At 20% no jams are formed. The formation of jams is sensitive to the sequence of vehicles (ACC or manual). At lower speeds (approximately 15 m/s ), no critical concentration for complete jam suppression is found. Rather, the average velocity in the pseudojam region increases with increasing ACC concentration. Mixing 50% ACC vehicles randomly with manually driven vehicles on the primary lane in onramp simulations shows only modestly reduced travel times and larger flow rates.

  7. Advances in the Design of High-Performance Flow Control

    NASA Astrophysics Data System (ADS)

    Chen, Kevin K.

    This thesis tackles challenges in feedback control design for fluid flows, from multiple angles and approaches. It covers three major facets---stability theory, control, and reduced-order modeling---and it investigates three major challenges of these facets: nonlinearity, high dimensionality, and non-normality. The dissertation begins with a discussion of global stability via linearized Navier--Stokes eigendecompositions, including numerical algorithms for this analysis. This section then investigates the global stability of a pipe flow through a T-shaped bifurcation at mid-hundred Reynolds numbers, which exhibits vortex breakdown. The recirculation and sensitivity regions closely coincide, which we explain using an inviscid short-wavelength perturbation theory. We also discuss the stability and receptivity properties of this flow. The second part discusses feedback control design for fluid flows, including optimal actuator and sensor placement. It presents an algorithm that computes the gradient of a control measure with respect to such placements, allowing an efficient gradient-based optimization. The implementation on the linearized Ginzburg--Landau and the Orr--Sommerfeld/Squire models of fluid flow reveals that common methods for placement, such as global mode analysis, are suboptimal. We discuss heuristics, including sensitivity, that may predict optimal placements. The third part covers reduced-order flow modeling. It examines previously unknown properties of dynamic mode decomposition (DMD)---a data-based modeling technique---including the uniqueness of the numerical algorithm and the boundary conditions of DMD-based models. We also propose an "optimized" DMD that produces less spurious decompositions, and gives the user control over the number of output modes. We show examples from the two-dimensional laminar flow over a cylinder. This part also investigates the stability and performance of high dimensional (e.g., fluid) systems in closed-loop with reduced

  8. Active Feedback Control of a Web Flutter Using Flow Control Devices

    NASA Astrophysics Data System (ADS)

    Hayashi, Yusuke; Watanabe, Masahiro; Hara, Kensuke

    This paper develops a non-contact active feedback control of web flutter in a narrow passage by using movable plates set at inlet and outlet of the passage. The strategy of this active feedback control is based on the flow-control which cancels the exciting fluid force acting on the web, i.e., cancels the self-excited feedback mechanism. In this paper, suppression of the web flutter by the active feedback control is demonstrated experimentally. In the experiments, a web (film), as a controlled object, is subjected to air flow in a narrow passage. The web flutter occurs to the web in the translational motion over the critical flow velocity. And the web flutter is actively controlled and suppressed by the movable plate motion which changes the air flow in the passage. The critical flow velocity under controlled condition is examined with changing the controller gain and phase-shift between the web motion and the movable plate motion. As a result, it is indicated that the active feedback control increases the critical flow velocity, and suppress the web flutter effectively. Moreover, the control performance is examined experimentally, and stabilization mechanism by the active feedback control is discussed.

  9. Controlled synthesis of poly(3-hexylthiophene) in continuous flow.

    PubMed

    Seyler, Helga; Subbiah, Jegadesan; Jones, David John; Holmes, Andrew Bruce; Wong, Wallace Wing Ho

    2013-01-01

    There is an increasing demand for organic semiconducting materials with the emergence of organic electronic devices. In particular, large-area devices such as organic thin-film photovoltaics will require significant quantities of materials for device optimization, lifetime testing and commercialization. Sourcing large quantities of materials required for the optimization of large area devices is costly and often impossible to achieve. Continuous-flow synthesis enables straight-forward scale-up of materials compared to conventional batch reactions. In this study, poly(3-hexylthiophene), P3HT, was synthesized in a bench-top continuous-flow reactor. Precise control of the molecular weight was demonstrated for the first time in flow for conjugated polymers by accurate addition of catalyst to the monomer solution. The P3HT samples synthesized in flow showed comparable performance to commercial P3HT samples in bulk heterojunction solar cell devices.

  10. Field-effect Flow Control in Polymer Microchannel Networks

    NASA Technical Reports Server (NTRS)

    Sniadecki, Nathan; Lee, Cheng S.; Beamesderfer, Mike; DeVoe, Don L.

    2003-01-01

    A new Bio-MEMS electroosmotic flow (EOF) modulator for plastic microchannel networks has been developed. The EOF modulator uses field-effect flow control (FEFC) to adjust the zeta potential at the Parylene C microchannel wall. By setting a differential EOF pumping rate in two of the three microchannels at a T-intersection with EOF modulators, the induced pressure at the intersection generated pumping in the third, field-free microchannel. The EOF modulators are able to change the magnitude and direction of the pressure pumping by inducing either a negative or positive pressure at the intersection. The flow velocity is tracked by neutralized fluorescent microbeads in the microchannels. The proof-of-concept of the EOF modulator described here may be applied to complex plastic ,microchannel networks where individual microchannel flow rates are addressable by localized induced-pressure pumping.

  11. Field-effect Flow Control in Polymer Microchannel Networks

    NASA Technical Reports Server (NTRS)

    Sniadecki, Nathan; Lee, Cheng S.; Beamesderfer, Mike; DeVoe, Don L.

    2003-01-01

    A new Bio-MEMS electroosmotic flow (EOF) modulator for plastic microchannel networks has been developed. The EOF modulator uses field-effect flow control (FEFC) to adjust the zeta potential at the Parylene C microchannel wall. By setting a differential EOF pumping rate in two of the three microchannels at a T-intersection with EOF modulators, the induced pressure at the intersection generated pumping in the third, field-free microchannel. The EOF modulators are able to change the magnitude and direction of the pressure pumping by inducing either a negative or positive pressure at the intersection. The flow velocity is tracked by neutralized fluorescent microbeads in the microchannels. The proof-of-concept of the EOF modulator described here may be applied to complex plastic ,microchannel networks where individual microchannel flow rates are addressable by localized induced-pressure pumping.

  12. Verification of the karst flow model under laboratory controlled conditions

    NASA Astrophysics Data System (ADS)

    Gotovac, Hrvoje; Andric, Ivo; Malenica, Luka; Srzic, Veljko

    2016-04-01

    Karst aquifers are very important groundwater resources around the world as well as in coastal part of Croatia. They consist of extremely complex structure defining by slow and laminar porous medium and small fissures and usually fast turbulent conduits/karst channels. Except simple lumped hydrological models that ignore high karst heterogeneity, full hydraulic (distributive) models have been developed exclusively by conventional finite element and finite volume elements considering complete karst heterogeneity structure that improves our understanding of complex processes in karst. Groundwater flow modeling in complex karst aquifers are faced by many difficulties such as a lack of heterogeneity knowledge (especially conduits), resolution of different spatial/temporal scales, connectivity between matrix and conduits, setting of appropriate boundary conditions and many others. Particular problem of karst flow modeling is verification of distributive models under real aquifer conditions due to lack of above-mentioned information. Therefore, we will show here possibility to verify karst flow models under the laboratory controlled conditions. Special 3-D karst flow model (5.6*2.6*2 m) consists of concrete construction, rainfall platform, 74 piezometers, 2 reservoirs and other supply equipment. Model is filled by fine sand (3-D porous matrix) and drainage plastic pipes (1-D conduits). This model enables knowledge of full heterogeneity structure including position of different sand layers as well as conduits location and geometry. Moreover, we know geometry of conduits perforation that enable analysis of interaction between matrix and conduits. In addition, pressure and precipitation distribution and discharge flow rates from both phases can be measured very accurately. These possibilities are not present in real sites what this model makes much more useful for karst flow modeling. Many experiments were performed under different controlled conditions such as different

  13. Inlet Flow Control and Prediction Technologies for Embedded Propulsion Systems

    NASA Technical Reports Server (NTRS)

    McMillan, Michelle L.; Gissen, Abe; Vukasinovic, Bojan; Lakebrink, Matthew T.; Glezer, Ari; Mani, Mori; Mace, James

    2010-01-01

    Fail-safe inlet flow control may enable high-speed cruise efficiency, low noise signature, and reduced fuel-burn goals for hybrid wing-body aircraft. The objectives of this program are to develop flow control and prediction methodologies for boundary-layer ingesting (BLI) inlets used in these aircraft. This report covers the second of a three year program. The approach integrates experiments and numerical simulations. Both passive and active flow-control devices were tested in a small-scale wind tunnel. Hybrid actuation approaches, combining a passive microvane and active synthetic jet, were tested in various geometric arrangements. Detailed flow measurements were taken to provide insight into the flow physics. Results of the numerical simulations were correlated against experimental data. The sensitivity of results to grid resolution and turbulence models was examined. Aerodynamic benefits from microvanes and microramps were assessed when installed in an offset BLI inlet. Benefits were quantified in terms of recovery and distortion changes. Microvanes were more effective than microramps at improving recovery and distortion.

  14. Overview of Active Flow Control at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Pack, L. G.; Joslin, R. D.

    1998-01-01

    The paper summarizes Active Flow Control projects currently underway at the NASA Langley Research Center. Technology development is being pursued within a multidisciplinary, cooperative approach, involving the classical disciplines of fluid mechanics, structural mechanics, material science, acoustics, and stability and control theory. Complementing the companion papers in this session, the present paper will focus on projects that have the goal of extending the state-of-the-art in the measurement, prediction, and control of unsteady, nonlinear aerodynamics. Toward this goal, innovative actuators, micro and macro sensors, and control strategies are considered for high payoff flow control applications. The target payoffs are outlined within each section below. Validation of the approaches range from bench-top experiments to wind-tunnel experiments to flight tests. Obtaining correlations for future actuator and sensor designs are implicit in the discussion. The products of the demonstration projects and design tool development from the fundamental NASA R&D level technology will then be transferred to the Applied Research components within NASA, DOD, and US Industry. Keywords: active flow control, separation control, MEMS, review

  15. Research in Natural Laminar Flow and Laminar-Flow Control, part 1

    NASA Technical Reports Server (NTRS)

    Hefner, Jerry N. (Compiler); Sabo, Frances E. (Compiler)

    1987-01-01

    Since the mid 1970's, NASA, industry, and universities have worked together to conduct important research focused at developing laminar flow technology that could reduce fuel consumption for general aviation, commuter, and transport aircraft by as much as 40 to 50 percent. The symposium was planned in view of the recent accomplishments within the areas of laminar flow control and natural laminar flow, and the potential benefits of laminar flow technology to the civil and military aircraft communities in the United States. Included were technical sessions on advanced theory and design tool development; wind tunnel and flight research; transition measurement and detection techniques; low and high Reynolds number research; and subsonic and supersonic research.

  16. AIAA Educator Academy - Mars Rover Curriculum: A 6 week multidisciplinary space science based curriculum

    NASA Astrophysics Data System (ADS)

    Henriquez, E.; Bering, E. A.; Slagle, E.; Nieser, K.; Carlson, C.; Kapral, A.

    2013-12-01

    The Curiosity mission has captured the imagination of children, as NASA missions have done for decades. The AIAA and the University of Houston have developed a flexible curriculum program that offers children in-depth science and language arts learning culminating in the design and construction of their own model rover. The program is called the Mars Rover Model Celebration. It focuses on students, teachers and parents in grades 3-8. Students learn to research Mars in order to pick a science question about Mars that is of interest to them. They learn principles of spacecraft design in order to build a model of a Mars rover to carry out their mission on the surface of Mars. The model is a mock-up, constructed at a minimal cost from art supplies. This project may be used either informally as an after school club or youth group activity or formally as part of a class studying general science, earth science, solar system astronomy or robotics, or as a multi-disciplinary unit for a gifted and talented program. The project's unique strength lies in engaging students in the process of spacecraft design and interesting them in aerospace engineering careers. The project is aimed at elementary and secondary education. Not only will these students learn about scientific fields relevant to the mission (space science, physics, geology, robotics, and more), they will gain an appreciation for how this knowledge is used to tackle complex problems. The low cost of the event makes it an ideal enrichment vehicle for low income schools. It provides activities that provide professional development to educators, curricular support resources using NASA Science Mission Directorate (SMD) content, and provides family opportunities for involvement in K-12 student learning. This paper will describe the structure and organization of the 6 week curriculum. A set of 30 new 5E lesson plans have been written to support this project as a classroom activity. The challenge of developing interactive

  17. Size-controlled flow synthesis of gold nanoparticles using a segmented flow microfluidic platform.

    PubMed

    Cabeza, Victor Sebastian; Kuhn, Simon; Kulkarni, Amol A; Jensen, Klavs F

    2012-05-01

    Segmented flow is often used in the synthesis of nanomaterials to achieve narrow particle size distribution. The narrowness of the distribution is commonly attributed to the reduced dispersion associated with segmented flows. On the basis of the analysis of flow fields and the resulting particle size distribution, we demonstrate that it is the slip velocity between the two fluids and internal mixing in the continuous-phase slugs that govern the nature of the particle size distribution. The reduction in the axial dispersion has less impact on particle growth and hence on the particle size distribution. Synthesis of gold nanoparticles from HAuCl(4) with rapid reduction by NaBH(4) serves as a model system. Rapid reduction yields gold nuclei, which grow by agglomeration, and it is controlled by the interaction of the nuclei with local flow. Thus, the difference in the physical properties of the two phases and the inlet flow rates ultimately control the particle growth. Hence, a careful choice of continuous and dispersed phases is necessary to control the nanoparticle size and size distribution.

  18. Management and control of unsteady and turbulent flows

    NASA Astrophysics Data System (ADS)

    Nagib, Hassan M.; Acharya, Mukund; Corke, Thomas C.; Reisenthel, Patrick H.; Wark, Candace E.

    1988-06-01

    Progress in four areas of research has been achieved during the first year: (1) controlled transitioning boundary layers; phase coupled plane TS waves and oblique waves are used to study various types of transition including detuned modes, (2) turbulent boundary layer structure and control; the structures responsible for the turbulence production in high Reynolds number boundary layers have been documented and manipulated, (3) management of unsteady and three-dimensional flows; flows over airfoils, axisymmetric forebodies, vortex-wing interactions, and wing-body junctions, are examined with and without passive and active flow manipulators including zero-mass base bleed, (4) scanning laser anemometry; a technique capable of mapping the flowfield in a plane has been developed.

  19. ac power control in the Core Flow Test Loop

    SciTech Connect

    McDonald, D.W.

    1980-01-01

    This work represents a status report on a development effort to design an ac power controller for the Core Flow Test Loop. The Core Flow Test Loop will be an engineering test facility which will simulate the thermal environment of a gas-cooled fast-breeder reactor. The problems and limitations of using sinusoidal ac power to simulate the power generated within a nuclear reactor are addressed. The transformer-thyristor configuration chosen for the Core Flow Test Loop power supply is presented. The initial considerations, design, and analysis of a closed-loop controller prototype are detailed. The design is then analyzed for improved performance possibilities and failure modes are investigated at length. A summary of the work completed to date and a proposed outline for continued development completes the report.

  20. Flow characteristics of control valve for different strokes

    NASA Astrophysics Data System (ADS)

    Jablonská, Jana; Kozubková, Milada

    2016-03-01

    The article deals with the determination of flow characteristics and loss coefficients of control valve when the water flows in the interval of operating parameters, including the evaluation of vapour and air cavitation regime. The characteristics of the control valve are measured on the experimental equipment and subsequently loss coefficients are determined. Data from experimental measurements are used for creating of mathematical model with vapour and air cavitation and verification results. This validation will enable the application of methods of numerical modelling for valves of atypical dimensions e.g. for use in nuclear power industry. The correct knowledge of the valve characteristics and fundamental coefficients (e.g. flow coefficient, cavitation coefficient and loss coefficient) is necessarily required primarily for designers of pipe networks.

  1. Intracycle angular velocity control of cross-flow turbines

    NASA Astrophysics Data System (ADS)

    Strom, Benjamin; Brunton, Steven L.; Polagye, Brian

    2017-08-01

    Cross-flow turbines, also known as vertical-axis turbines, are attractive for power generation from wind and water currents. Some cross-flow turbine designs optimize unsteady fluid forces and maximize power output by controlling blade kinematics within one rotation. One established method is to dynamically pitch the blades. Here we introduce a mechanically simpler alternative: optimize the turbine rotation rate as a function of angular blade position. We demonstrate experimentally that this approach results in a 59% increase in power output over standard control methods. Analysis of fluid forcing and blade kinematics suggest that power increase is achieved through modification of the local flow conditions and alignment of fluid force and rotation rate extrema. The result is a low-speed, structurally robust turbine that achieves high efficiency and could enable a new generation of environmentally benign turbines for renewable power generation.

  2. Closed-Loop Control of Vortex Formation in Separated Flows

    NASA Technical Reports Server (NTRS)

    Colonius, Tim; Joe, Won Tae; MacMynowski, Doug; Rowley, Clancy; Taira, Sam; Ahuja, Sunil

    2010-01-01

    In order to phase lock the flow at the desired shedding cycle, particularly at Phi,best, We designed a feedback compensator. (Even though the open-loop forcing at Wf below Wn can lead to phase-locked limit cycles with a high average lift,) This feedback controller resulted in the phase-locked limit cycles that the open-loop control could not achieve for alpha=30 and 40 Particularly for alpha=40, the feedback was able to stabilize the limit cycle that was not stable with any of the open-loop periodic forcing. This results in stable phase-locked limit cycles for a larger range of forcing frequencies than the open-loop control. Also, it was shown that the feedback achieved the high-lift unsteady flow states that open-loop control could not sustain even after the states have been achieved for a long period of time.

  3. Flow Control Predictions using URANS Modeling: A Parametric Study

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L.; Greenblatt, David

    2007-01-01

    A computational study was performed for steady and oscillatory flow control over a hump model with flow separation to assess how well the steady and unsteady Reynolds-averaged Navier-Stokes equations predict trends due to Reynolds number, control magnitude, and control frequency. As demonstrated previously, the hump model case is useful because it clearly demonstrates a failing in all known turbulence models: they under-predict the turbulent shear stress in the separated region and consequently reattachment occurs too far downstream. In spite of this known failing, three different turbulence models were employed to determine if trends can be captured even though absolute levels are not. The three turbulence models behaved similarly. Overall they showed very similar trends as experiment for steady suction, but only agreed qualitatively with some of the trends for oscillatory control.

  4. Application of laminar flow control to the High Speed Civil Transport - The NASA Supersonic Laminar Flow Control Program

    NASA Technical Reports Server (NTRS)

    Fischer, Michael C.; Vemuru, Chandra S.

    1991-01-01

    The NASA Supersonic Laminar Flow Control (SLFC) program encompasses the development of refined CFD methods and boundary layer stability codes for the highly 3D supersonic flow conditions encountered by the F-16XL technology demonstration aircraft and the prospective High Speed Civil Transport (HSCT). While the F-16XL-1 aircraft continues to gather SLFC data, work is under way on the F-16XL-2 aircraft: which will furnish attach-line design criteria, code-calibration data, and an improved understanding of the flowfield over a wing that will add confidence to the design of HSCTs' boundary layer-controlling air-suction panels.

  5. Flow manipulation and control methodologies for vacuum infusion processes

    NASA Astrophysics Data System (ADS)

    Alms, Justin B.

    Vacuum Infusion Processes (VIPs) are very attractive composite manufacturing processes since large structures such as fuselages and wind blades can be fabricated in a cost effective manner. In VIPs, the fabric layers are placed on a one sided mold which is closed by enveloping the entire mold with a thin plastic film and evacuating the air out. The vacuum compresses the fabric and when a resin inlet is opened, resin flows into the mold. The resin is allowed to cure before demolding the structure. However, VIPs causes non-repeatable and problematic resin filling patterns due to the heterogeneous nature of the material, nesting between various layers, and the hand labor utilized for laying up the fabric. The design of the manufacturing process routinely involves a trial and error model which make manufacturing costs and development time difficult to estimate. The clear solution to improving the reliability and robustness of VIPs is to implement a system capable of on-line flow control. While on-line flow control has been studied and developed for other composite manufacturing processes, the VIPs have been largely ignored as there are few process parameters that lend themselves to effective flow control. In this work, two new processes were discovered with the goal of on-line control of VIPs in mind. These two processes referred to as Flow Flooding Chamber (FFC) and Vacuum Induced Preform Relaxation (VIPR) will be discussed. They both employ an external vacuum chamber to influence the permeability of the fabric temporarily which allows one to redirect the resin flow to resin starved regions of the mold. The VIPR process in addition uses a low and regulated vacuum pressure in the external chamber to increase the permeability of the fabric in a controllable manner. The objective is to understand how the VIPR process affects the resin flow in order to implement it into a complete flow control and automated environment which will reduce or eliminate the variability

  6. Crossflow transition control by upstream flow deformation using plasma actuators

    NASA Astrophysics Data System (ADS)

    Dörr, Philipp C.; Kloker, Markus J.

    2017-02-01

    Control of laminar-turbulent transition in a swept-wing-type boundary-layer flow, subject to primary crossflow instability, is investigated using direct numerical simulations. In our previous works, we explored a direct base-flow stabilization aimed at a spanwise homogenous flow manipulation or a direct crossflow-vortex manipulation by plasma actuators. In this paper, the technique of upstream flow deformation (UFD) is applied, needing by far the least energy input. The actuators, modeled by local volume forcing, are set to excite amplified steady crossflow vortex (CFV) control modes with a higher spanwise wavenumber than the most amplified modes. The resulting nonlinear control CFVs are spaced narrower than the naturally occurring vortices and are less unstable with respect to secondary instability. They generate a beneficial mean-flow distortion attenuating the primary crossflow instability, and thus a delay of the transition to turbulence. Unlike roughness elements for UFD, the employed dielectric barrier discharge plasma actuators allow to set the force direction: Forcing against the crossflow has a direct, fundamental stabilizing effect due to a reduction of the mean crossflow, whereas forcing in the crossflow direction locally invokes the opposite due to a local increase of the mean crossflow. The differences between these settings, also with respect to forcing in streamwise direction, are discussed in detail, and it is shown that a significant transition delay can be achieved indeed with both, however with a differing efficiency and robustness. Additionally, a comparison to a set-up with an excitation of the control modes by synthetic blowing and suction is performed to clarify the role of the direct effect on the base flow.

  7. Passive and Active Control of Massively Separated High-Speed Flows

    DTIC Science & Technology

    2014-01-31

    V. Kale , J. Craig Dutton, Gregory S. Elliott. Experimental Characterization of a Pulsed Plasma Jet, AIAA Journal, (06 2013): 0. doi: 10.2514/1...2012 08/16/2011 18.00 11.00 13.00 12.00 Received Paper 9.00 5.00 Bradley G. DeBlauw, Eli Lazar, Nachiket Kale , Nick Glumac, Craig Dutton, Gregory Elliott...of Arc Filament Plasma Actuators, 2012 AIAA Aerospace Sciences Meeting. 09-JAN-12, . : , Nachiket V. Kale , J. Craig Dutton, Gregory S. Elliott4

  8. URBAN WET-WEATHER FLOW POLLUTION MANAGEMENT AND CONTROL

    EPA Science Inventory

    One of the challenges in protecting urban watersheds lies in effectively controlling the contaminants in both overland runoff and sewerage system overflows during wet-weather events. Abatement of wet-weather flow (WWF) pollution can be implemented at the source by land managemen...

  9. Application of porous materials for laminar flow control

    NASA Technical Reports Server (NTRS)

    Pearce, W. E.

    1978-01-01

    Fairly smooth porous materials were elected for study Doweave; Fibermetal; Dynapore; and perforated titanium sheet. Factors examined include: surface smoothness; suction characteristics; porosity; surface impact resistance; and strain compatibility. A laminar flow control suction glove arrangement was identified with material combinations compatible with thermal expansion and structural strain.

  10. URBAN WET-WEATHER FLOW POLLUTION MANAGEMENT AND CONTROL

    EPA Science Inventory

    One of the challenges in protecting urban watersheds lies in effectively controlling the contaminants in both overland runoff and sewerage system overflows during wet-weather events. Abatement of wet-weather flow (WWF) pollution can be implemented at the source by land managemen...

  11. Flow intake control using dry-weather forecast

    NASA Astrophysics Data System (ADS)

    Icke, Otto; van Schagen, Kim; Huising, Christian; Wuister, Jasper; van Dijk, Edward; Budding, Arjan

    2017-08-01

    Level-based control of the influent flow causes peak discharges at a waste water treatment plant (WWTP) after rainfall events. Furthermore, the capacity of the post-treatment is in general smaller than the maximum hydraulic capacity of the WWTP. This results in a significant bypass of the post-treatment during peak discharge. The optimisation of influent flow reduces peak discharge, and increases the treatment efficiency of the whole water cycle, which benefits the surface water quality. In this paper, it is shown that half of the bypasses of the post-treatment can be prevented by predictive control. A predictive controller for influent flow is implemented using the Aquasuite® Advanced Monitoring and Control platform. Based on real-time measured water levels in the sewerage and both rainfall and dry-weather flow (DWF) predictions, a discharge limitation is determined by a volume optimisation technique. For the analysed period (February-September 2016) results at WWTP Bennekom show that about 50 % of bypass volume can be prevented. Analysis of single rainfall events shows that the used approach is still conservative and that the bypass can be even further decreased by allowing discharge limitation during precipitation.

  12. Flow monitoring and control system for injection wells

    DOEpatents

    Corey, J.C.

    1991-01-01

    The present invention relates to a system for monitoring and controlling the rate of fluid flow from an injection well used for in-situ remediation of contaminated groundwater. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the US Department of Energy and Westinghouse Savannah River Company.

  13. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  14. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  15. Solving fluid-flow control problems with porous plastics.

    PubMed

    Wolbrom, I M

    1993-01-01

    To tackle fluid-flow control problems, traditional porous materials, such as ceramics, glass, metal, fabric, paper, and fibres, are now being replaced by an increasing range of porous plastics. In this article, the author discusses some of those that are available, and outlines the advantages of using these materials to replace traditional ones.

  16. 93. TEMPERATURE AND FLOW RATE CONTROLS FOR SYSTEM 1 AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    93. TEMPERATURE AND FLOW RATE CONTROLS FOR SYSTEM 1 AND SYSTEM 2, FACING WEST IN MECHANICAL EQUIPMENT ROOM (101), LSB (BLDG. 770) - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  17. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of a fundamental nature, concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research includes influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  18. Variability of sap flow on forest hillslopes: patterns and controls

    NASA Astrophysics Data System (ADS)

    Hassler, Sibylle; Blume, Theresa

    2013-04-01

    Sap flow in trees is an essential variable in integrated studies of hydrologic fluxes. It gives indication of transpiration rates for single trees and, with a suitable method of upscaling, for whole stands. This information is relevant for hydrologic and climate models, especially for the prediction of change in water fluxes in the soil-plant-atmosphere continuum under climate change. To this end, we do not only need knowledge concerning the response of sapflow to atmospheric forcing but also an understanding of the main controls on its spatial variability. Our study site consists of several subcatchments of the Attert basin in Luxembourg underlain by schists of the Ardennes massif. Within these subcatchments we measure sap flow in more than 20 trees on a range of forested hillslopes covered by a variety of temperate deciduous tree species such as beech, oak, hornbeam and maple as well as conifers such as firs. Our sap flow sensors are based on the heat pulse velocity method and consist of three needles, one needle acting as the heating device and the other two holding three thermistors each, enabling us to simultaneously measure sap flow velocity at three different depths within the tree. In close proximity to the trees we collect additional data on soil moisture, matric potential and groundwater levels. First results show that the sensor design seems promising for an upscaling of the measured sap flow velocities to sap flow at the tree level. The maximum depth of actively used sapwood as well as the decrease in sap flow velocity with increasing depth in the tree can be determined by way of the three thermistors. Marked differences in sap flow velocity profiles are visible between the different species, resulting in differences in sap flow for trees of similar diameter. We examine the range of tree sap flow values and variation due to species, size class, slope position and exposition and finally relate them to the dynamics of soil moisture conditions with the

  19. Pneumatic vortical flow control at high angles of attack

    NASA Technical Reports Server (NTRS)

    Tavella, Domingo A.; Schiff, Lewis B.; Cummings, Russell M.

    1990-01-01

    The injection of thin, high-momentum jets of air into the fuselage forebody boundary layers of the F-18 aircraft is explored numerically as a means of controlling the onset of fuselage vortices and of generating yaw control forces. The study was carried out for an angle of attack of 30 deg with symmetrical and asymmetrical blowing configurations. One-sided blowing results in a strongly asymmetrical flow pattern in the fore portion of the fuselage, leading to a net lateral force.

  20. Pneumatic vortical flow control at high angles of attack

    NASA Technical Reports Server (NTRS)

    Tavella, Domingo A.; Schiff, Lewis B.; Cummings, Russell M.

    1990-01-01

    The injection of thin, high-momentum jets of air into the fuselage forebody boundary layers of the F-18 aircraft is explored numerically as a means of controlling the onset of fuselage vortices and of generating yaw control forces. The study was carried out for an angle of attack of 30 deg with symmetrical and asymmetrical blowing configurations. One-sided blowing results in a strongly asymmetrical flow pattern in the fore portion of the fuselage, leading to a net lateral force.

  1. Controlling droplet incubation using close-packed plug flow

    PubMed Central

    Mary, Pascaline; Abate, Adam R.; Agresti, Jeremy J.; Weitz, David A.

    2011-01-01

    Controlling droplet incubation is critical for droplet-based microfluidic applications; however, current techniques are either of limited precision or place strict limits on the incubation times that can be achieved. Here, we present a simple technique to control incubation time by exploiting close-packed plug flow. In contrast to other techniques, this technique is applicable to very short and very long incubation times. PMID:21544238

  2. Experimental Feedback Control of Flow Induced Cavity Tones

    NASA Technical Reports Server (NTRS)

    Cabell, Randolph H.; Kegerise, Michael A.; Cox, David E.; Gibbs, Gary P.

    2005-01-01

    Discrete-time, linear quadratic methods were used to design feedback controllers for reducing tones generated by flow over a cavity. The dynamics of a synthetic jet actuator mounted at the leading edge of the cavity as observed by two microphones in the cavity were modeled over a broad frequency range using state space models computed from experimental data. Variations in closed loop performance as a function of model order, control order, control bandwidth, and state estimator design were studied using a cavity in the Probe Calibration Tunnel at NASA Langley. The controller successfully reduced the levels of multiple cavity tones at the tested flow speeds of Mach 0.275, 0.35, and 0.45. In some cases, the closed loop results were limited by excitation of sidebands of the cavity tones, or the creation of new tones at frequencies away from the cavity tones. Nonetheless, the results validate the combination of optimal control and experimentally-generated state space models, and suggest this approach may be useful for other flow control problems. The models were not able to account for non-linear dynamics, such as interactions between tones at different frequencies.

  3. A probabilistic approach to modeling and controlling fluid flows

    NASA Astrophysics Data System (ADS)

    Kaiser, Eurika; Noack, Bernd R.; Spohn, Andreas; Cattafesta, Louis N.; Morzynski, Marek; Daviller, Guillaume; Brunton, Bingni W.; Brunton, Steven L.

    2016-11-01

    We extend cluster-based reduced-order modeling (CROM) (Kaiser et al., 2014) to include control inputs in order to determine optimal control laws with respect to a cost function for unsteady flows. The proposed methodology frames high-dimensional, nonlinear dynamics into low- dimensional, probabilistic, linear dynamics which considerably simplifies the optimal control problem while preserving nonlinear actuation mechanisms. The data-driven approach builds upon the unsupervised partitioning of the data into few kinematically similar flow states using a clustering algorithm. The coarse-grained dynamics are then described by a Markov model which is closely related to the approximation of Perron-Frobenius operators. The Markov model can be used as predictor for the ergodic probability distribution for a particular control law approximating the long-term behavior of the system on which basis the optimal control law is determined. Moreover, we combine CROM with a recently developed approach for optimal sparse sensor placement for classification (Brunton et al., 2013) as a critical enabler for in-time control and for the systematic identification of dynamical regimes from few measurements. The approach is applied to a separating flow and a mixing layer exhibiting vortex pairing.

  4. Robust Feedback Control of Flow Induced Structural Radiation of Sound

    NASA Technical Reports Server (NTRS)

    Heatwole, Craig M.; Bernhard, Robert J.; Franchek, Matthew A.

    1997-01-01

    A significant component of the interior noise of aircraft and automobiles is a result of turbulent boundary layer excitation of the vehicular structure. In this work, active robust feedback control of the noise due to this non-predictable excitation is investigated. Both an analytical model and experimental investigations are used to determine the characteristics of the flow induced structural sound radiation problem. The problem is shown to be broadband in nature with large system uncertainties associated with the various operating conditions. Furthermore the delay associated with sound propagation is shown to restrict the use of microphone feedback. The state of the art control methodologies, IL synthesis and adaptive feedback control, are evaluated and shown to have limited success for solving this problem. A robust frequency domain controller design methodology is developed for the problem of sound radiated from turbulent flow driven plates. The control design methodology uses frequency domain sequential loop shaping techniques. System uncertainty, sound pressure level reduction performance, and actuator constraints are included in the design process. Using this design method, phase lag was added using non-minimum phase zeros such that the beneficial plant dynamics could be used. This general control approach has application to lightly damped vibration and sound radiation problems where there are high bandwidth control objectives requiring a low controller DC gain and controller order.

  5. Dielectric Barrier Discharge Plasma Actuators for Flow Control *

    NASA Astrophysics Data System (ADS)

    Corke, Thomas C.; Enloe, C. Lon; Wilkinson, Stephen P.

    2010-01-01

    The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single-dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body-force vector field that couples with the momentum in the external flow. The body force can be derived from first principles, and the effect of plasma actuators can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of internal and external flow applications. Although initially considered useful only at low speeds, plasma actuators are effective in a number of applications at high subsonic, transonic, and supersonic Mach numbers, owing largely to more optimized actuator designs that were developed through better understanding and modeling of the actuator physics. New applications continue to appear through a growing number of programs in the United States, Germany, France, England, the Netherlands, Russia, Australia, Japan, and China. This review provides an overview of the physics and modeling of SDBD plasma actuators. It highlights some of the capabilities of plasma actuators through examples from experiments and simulations.

  6. Experimental Investigation of Actuators for Flow Control in Inlet Ducts

    NASA Astrophysics Data System (ADS)

    Vaccaro, John; Elimelech, Yossef; Amitay, Michael

    2010-11-01

    Attractive to aircraft designers are compact inlets, which implement curved flow paths to the compressor face. These curved flow paths could be employed for multiple reasons. One of which is to connect the air intake to the engine embedded in the aircraft body. A compromise must be made between the compactness of the inlet and its aerodynamic performance. The aerodynamic purpose of inlets is to decelerate the oncoming flow before reaching the engine while minimizing total pressure loss, unsteadiness and distortion. Low length-to-diameter ratio inlets have a high degree of curvature, which inevitably causes flow separation and secondary flows. Currently, the length of the propulsion system is constraining the overall size of Unmanned Air Vehicles (UAVs), thus, smaller more efficient aircrafts could be realized if the propulsion system could be shortened. Therefore, active flow control is studied in a compact (L/D=1.5) inlet to improve performance metrics. Actuation from a spanwise varying coanda type ejector actuator and a hybrid coanda type ejector / vortex generator jet actuator is investigated. Special attention will be given to the pressure recovery at the AIP along with unsteady pressure signatures along the inlet surface and at the AIP.

  7. What mainly controls recession flows in river basins?

    NASA Astrophysics Data System (ADS)

    Biswal, Basudev; Nagesh Kumar, D.

    2014-03-01

    The ubiquity of the power law relationship between dQ/dt and Q for recession periods (-dQ/dt=kQα,Q being discharge at the basin outlet at time t) clearly hints at the existence of a dominant recession flow process that is common to all real basins. It is commonly assumed that a basin, during recession events, functions as a single phreatic aquifer resting on a impermeable horizontal bed or the Dupuit-Boussinesq (DB) aquifer, and with time different aquifer geometric conditions arise that give different values of α and k. The recently proposed alternative model, geomorphological recession flow model, however, suggests that recession flows are controlled primarily by the dynamics of the active drainage network (ADN). In this study we use data for several basins and compare the above two contrasting recession flow models in order to understand which of the above two factors dominates during recession periods in steep basins. Particularly, we do the comparison by selecting three key recession flow properties: (1) power law exponent α, (2) dynamic dQ/dt-Q relationship (characterized by k) and (3) recession timescale (time period for which a recession event lasts). Our observations suggest that neither drainage from phreatic aquifers nor evapotranspiration significantly controls recession flows. Results show that the value of α and recession timescale are not modeled well by DB aquifer model. However, the above mentioned three recession curve properties can be captured satisfactorily by considering the dynamics of the ADN as described by geomorphological recession flow model, possibly indicating that the ADN represents not just phreatic aquifers but the organization of various sub-surface storage systems within the basin.

  8. Bitrate adaptation flow control and client-based congestion control for multimedia-on-demand

    NASA Astrophysics Data System (ADS)

    Chan, Siu-Ping; Kok, Chi-Wah

    2003-06-01

    A flow control for streaming multimedia data over UDP on IP network is presented. The bitrate adaptation algorithm embedded in the protocol is considered to be an end-to-end mechanism in the application level. The flow control system constantly maintains the streaming buffer at a prescribed capacity even with bursty network losses by adapting the multimedia bitrate B from the streaming codec. A congestion control algorithm which is considered to be located in a lower level than that of the flow control mechanism is presented. It works together with the presented flow control to resolve network congestion problems while maintaining a degree of TCP-friendliness by changing the sending rate R at the server. Simulation results obtained from NS2 have shown better resource allocation can be obtained, and an overall incrase in the average sending rate and hence better quality of streaming media is observed.

  9. Model-based feedback control of subsonic cavity flows: Control design

    NASA Astrophysics Data System (ADS)

    Yuan, Xin

    In this dissertation, we present and discuss development, implementation, and experimental results of reduced-order model based feedback control of subsonic cavity flows. Model based feedback control of subsonic flows have been studied and implemented by the flow control group at the Collaborative Center of Control Science (CCCS) at the Ohio State University (OSU). The team, composed of researchers from the departments of Electrical Engineering and Mechanical Engineering at the Ohio State, the Air Force Research Laboratory, and NASA Glenn Research Center, possesses synergistic capabilities in all of the required multidisciplinary areas of experimental data acquisition, computational flow simulation, low dimensional modeling, controller design, and experimental validation. The goal of the CCCS effort is to develop tools and methodologies for the use of closed-loop aerodynamic flow control to manipulate the flow over maneuvering air vehicles. The problem chosen for the initial study by the CCCS flow team is control of the resonant noise generated by subsonic flow past an open cavity. This phenomenon is characterized by a strong coupling between the flow dynamics and the flow-induced acoustic field that can lead to self-sustained resonance. Two approaches towards model development have been studied in this dissertation. One aims at representing the physical properties of the system by dynamical models in transfer function forms, referred to as the physics-based linear model in this dissertation. The other approach we have followed is based on proper orthogonal decomposition (POD) and Galerkin projection methods involving the flow governing equations, which is referred to as the nonlinear model or Galerkin model in the dissertation. Each model mentioned above can be further divided into two types: model derived from numerical simulation data and model derived from real time experimental data. Different types of feedback controllers have been designed for corresponding

  10. Mass flow-rate control through time periodic electro-osmotic flows in circular microchannels

    NASA Astrophysics Data System (ADS)

    Chakraborty, Suman; Ray, Subhashis

    2008-08-01

    The present study is directed towards devising a scientific strategy for obtaining controlled time-periodic mass flow-rate characteristics through the employment of pulsating electric fields in circular microchannels by exploiting certain intrinsic characteristics of periodic electro-osmosis phenomenon. Within the assumption of thin electrical double layers, the governing equations for potential distribution and fluid flow are derived, corresponding to a steady base state and a time-varying perturbed state, by assuming periodic forms of the imposed electrical fields and the resultant velocity fields. For sinusoidal pulsations of the electric field superimposed over its mean, a signature map depicting the amplitudes of the mass flow rate and the electrical field as well as their phase differences is obtained from the theoretical analysis as a function of a nondimensional frequency parameter for different ratios of the characteristic electric double layer thickness relative to the microchannel radius. Distinctive characteristics in the signature profiles are obtained for lower and higher frequencies, primarily attributed to the finite time scale for momentum propagation away from the walls. The signature characteristics, obtained from the solution of the prescribed sinusoidal electric field, are subsequently used to solve the "inverse" problem, where the mass flow rate is prescribed in the form of sinusoidal pulsations and the desired electric fields that would produce the required mass flow-rate variations are obtained. The analysis is subsequently extended for controlled triangular and trapezoidal pulsations in the mass flow rate and the required electric fields are successfully obtained. It is observed that the higher the double layer thickness is in comparison to the channel radius, the more prominent is the deviation of the shape of the required electric field pulsation from the desired transience in the mass flow-rate characteristics. Possible extensions of the

  11. Control of flow separation in airfoil/wing design applications

    NASA Technical Reports Server (NTRS)

    Gally, Thomas A.

    1994-01-01

    Existing aerodynamic design methods have generally concentrated on the optimization of airfoil or wing shapes to produce a minimum drag while satisfying some basic constraints such as lift, pitching moment, or thickness. Since the minimization of drag almost always precludes the existence of separated flow, the evaluation and validation of these design methods for their robustness and accuracy when separated flow is present has not been aggressively pursued. However, two new applications for these design tools may be expected to include separated flow and the issues of aerodynamic design with this feature must be addressed. The first application of the aerodynamic design tools is the design of airfoils or wings to provide an optimal performance over a wide range of flight conditions (multipoint design). While the definition of 'optimal performance' in the multipoint setting is currently being hashed out, it is recognized that given a wide enough range of flight conditions, it will not be possible to ensure a minimum drag constraint at all conditions, and in fact some amount of separated flow (presumably small) may have to be allowed at the more demanding flight conditions. Thus a multipoint design method must be tolerant of the existence of separated flow and may include some controls upon its extent. The second application is in the design of wings with extended high speed buffet boundaries of their flight envelopes. Buffet occurs on a wing when regions of flow separation have grown to the extent that their time varying pressures induce possible destructive effects upon the wing structure or adversely effect either the aircraft controllability or the passenger comfort. A conservative approach to the expansion of the buffet flight boundary is to simply expand the flight envelope of nonseparated flow under the assumption that buffet will also thus be alleviated. However, having the ability to design a wing with separated flow and thus to control the location, extent

  12. Spectral element simulations of unsteady flow over a 3D, low aspect-ratio semi-circular wing

    NASA Astrophysics Data System (ADS)

    Kandala, Sriharsha; Rempfer, Dietmar

    2011-11-01

    Numerical simulations of unsteady 3D flow over a low-aspect-ratio semi-circular wing are performed using a spectral element method. Specsolve, a parallel spectral element solver currently under development at IIT, is used for the simulation. The solution is represented locally as a tensor product of Legendre polynomials and C0-continuity is enforced between adjacent domains. A BDF/EXT scheme is used for temporal integration. The fractional step method is used for computing velocity and pressure. The code incorporates a FDM (fast diagonalization method) based overlapping Schwarz preconditioner for the consistent Poisson operator and an algebraic multigrid based coarse grid solver (P.F. Fischer et al, J. Phys.: Conf. Ser.(125) 012076, 2008) for pressure. The simulation replicates the conditions of the active flow control experiment (D. Williams et al, AIAA paper, 2010-4969). The Reynolds number based on chord length and free-stream velocity is about 68000. Different angles of attack, encompassing both pre-stall and post-stall regimes, are considered. These results are compared with data from the experiment and numerical simulations based on Lattice Boltzmann method (G. Brès et al, AIAA paper, 2010-4713).

  13. Typing Local Control and State Using Flow Analysis

    NASA Astrophysics Data System (ADS)

    Guha, Arjun; Saftoiu, Claudiu; Krishnamurthi, Shriram

    Programs written in scripting languages employ idioms that confound conventional type systems. In this paper, we highlight one important set of related idioms: the use of local control and state to reason informally about types. To address these idioms, we formalize run-time tags and their relationship to types, and use these to present a novel strategy to integrate typing with flow analysis in a modular way. We demonstrate that in our separation of typing and flow analysis, each component remains conventional, their composition is simple, but the result can handle these idioms better than either one alone.

  14. Quantifying, characterizing, and controlling information flow in ultracold atomic gases

    SciTech Connect

    Haikka, P.; McEndoo, S.; Maniscalco, S.; Palma, G. M.

    2011-09-15

    We study quantum information flow in a model comprised of a trapped impurity qubit immersed in a Bose-Einstein-condensed reservoir. We demonstrate how information flux between the qubit and the condensate can be manipulated by engineering the ultracold reservoir within experimentally realistic limits. We show that this system undergoes a transition from Markovian to non-Markovian dynamics, which can be controlled by changing key parameters such as the condensate scattering length. In this way, one can realize a quantum simulator of both Markovian and non-Markovian open quantum systems, the latter ones being characterized by a reverse flow of information from the background gas (reservoir) to the impurity (system).

  15. Application of laminar flow control to supersonic transport configurations

    NASA Technical Reports Server (NTRS)

    Parikh, P. G.; Nagel, A. L.

    1990-01-01

    The feasibility and impact of implementing a laminar flow control system on a supersonic transport configuration were investigated. A hybrid laminar flow control scheme consisting of suction controlled and natural laminar flow was developed for a double-delta type wing planform. The required suction flow rates were determined from boundary layer stability analyses using representative wing pressure distributions. A preliminary design of structural modifications needed to accommodate suction through a perforated titanium skin was carried out together with the ducting and systems needed to collect, compress and discharge the suction air. The benefits of reduced aerodynamic drag were weighed against the weight, volume and power requirement penalties of suction system installation in a mission performance and sizing program to assess the net benefits. The study showed a feasibility of achieving significant laminarization of the wing surface by use of a hybrid scheme, leading to an 8.2 percent reduction in the cruise drag. This resulted in an 8.5 percent reduction in the maximum takeoff weight and a 12 percent reduction in the fuel burn after the inclusion of the LFC system installation penalties. Several research needs were identified for a resolution of aerodynamics, structural and systems issues before these potential benefits could be realized in a practical system.

  16. Fluidic actuators for active flow control on airframe

    NASA Astrophysics Data System (ADS)

    Schueller, M.; Weigel, P.; Lipowski, M.; Meyer, M.; Schlösser, P.; Bauer, M.

    2016-04-01

    One objective of the European Projects AFLoNext and Clean Sky 2 is to apply Active Flow Control (AFC) on the airframe in critical aerodynamic areas such as the engine/wing junction or the outer wing region for being able to locally improve the aerodynamics in certain flight conditions. At the engine/wing junction, AFC is applied to alleviate or even eliminate flow separation at low speeds and high angle of attacks likely to be associated with the integration of underwing- mounted Ultra High Bypass Ratio (UHBR) engines and the necessary slat-cut-outs. At the outer wing region, AFC can be used to allow more aggressive future wing designs with improved performance. A relevant part of the work on AFC concepts for airframe application is the development of suitable actuators. Fluidic Actuated Flow Control (FAFC) has been introduced as a Flow Control Technology that influences the boundary layer by actively blowing air through slots or holes out of the aircraft skin. FAFC actuators can be classified by their Net Mass Flux and accordingly divided into ZNMF (Zero Net Mass Flux) and NZNMF (Non Zero Net-Mass-Flux) actuators. In the frame of both projects, both types of the FAFC actuator concepts are addressed. In this paper, the objectives of AFC on the airframe is presented and the actuators that are used within the project are discussed.

  17. Active Flow Control: Instrumentation Automation and Experimental Technique

    NASA Technical Reports Server (NTRS)

    Gimbert, N. Wes

    1995-01-01

    In investigating the potential of a new actuator for use in an active flow control system, several objectives had to be accomplished, the largest of which was the experimental setup. The work was conducted at the NASA Langley 20x28 Shear Flow Control Tunnel. The actuator named Thunder, is a high deflection piezo device recently developed at Langley Research Center. This research involved setting up the instrumentation, the lighting, the smoke, and the recording devices. The instrumentation was automated by means of a Power Macintosh running LabVIEW, a graphical instrumentation package developed by National Instruments. Routines were written to allow the tunnel conditions to be determined at a given instant at the push of a button. This included determination of tunnel pressures, speed, density, temperature, and viscosity. Other aspects of the experimental equipment included the set up of a CCD video camera with a video frame grabber, monitor, and VCR to capture the motion. A strobe light was used to highlight the smoke that was used to visualize the flow. Additional effort was put into creating a scale drawing of another tunnel on site and a limited literature search in the area of active flow control.

  18. Stabilising falling liquid film flows using feedback control

    SciTech Connect

    Thompson, Alice B. Gomes, Susana N.; Pavliotis, Grigorios A.; Papageorgiou, Demetrios T.

    2016-01-15

    Falling liquid films become unstable due to inertial effects when the fluid layer is sufficiently thick or the slope sufficiently steep. This free surface flow of a single fluid layer has industrial applications including coating and heat transfer, which benefit from smooth and wavy interfaces, respectively. Here, we discuss how the dynamics of the system are altered by feedback controls based on observations of the interface height, and supplied to the system via the perpendicular injection and suction of fluid through the wall. In this study, we model the system using both Benney and weighted-residual models that account for the fluid injection through the wall. We find that feedback using injection and suction is a remarkably effective control mechanism: the controls can be used to drive the system towards arbitrary steady states and travelling waves, and the qualitative effects are independent of the details of the flow modelling. Furthermore, we show that the system can still be successfully controlled when the feedback is applied via a set of localised actuators and only a small number of system observations are available, and that this is possible using both static (where the controls are based on only the most recent set of observations) and dynamic (where the controls are based on an approximation of the system which evolves over time) control schemes. This study thus provides a solid theoretical foundation for future experimental realisations of the active feedback control of falling liquid films.

  19. TCP flow control using link layer information in mobile networks

    NASA Astrophysics Data System (ADS)

    Koga, Hiroyuki; Kawahara, Kenji; Oie, Yuji

    2002-07-01

    Mobile Networks have been expanding and IMT-2000 further increases their available bandwidth over wireless links. However, TCP, which is a reliable end-to-end transport protocol, is tuned to perform well in wired networks where bit error rates are very low and packet loss occurs mostly because of congestion. Although a TCP sender can execute flow control to utilize as much available bandwidth as possible in wired networks, it cannot work well in wireless networks characterized by high bit error rates. In the next generation mobile systems, sophisticated error recovery technologies of FEC and ARQ are indeed employed over wireless links, i.e., over Layer 2, to avoid performance degradation of upper layers. However, multiple retransmissions by Layer 2 ARQ can adversely increase transmission delay of TCP segments, which will further make TCP unnecessarily increase RTO (Retransmission TimeOut). Furthermore, a link bandwidth assigned to TCP flows can change in response to changing air conditions to use wireless links efficiently. TCP thus has to adapt its transmission rate according to the changing available bandwidth. The major goal of this study is to develop a receiver-based effective TCP flow control without any modification on TCP senders, which are probably connected with wired networks. For this end, we propose a TCP flow control employing some Layer 2 information on a wireless link at the mobile station. Our performance evaluation of the proposed TCP shows that the receiver-based TCP flow control can moderate the performance degradation very well even if FER on Layer 2 is high.

  20. Nocturnal insects use optic flow for flight control.

    PubMed

    Baird, Emily; Kreiss, Eva; Wcislo, William; Warrant, Eric; Dacke, Marie

    2011-08-23

    To avoid collisions when navigating through cluttered environments, flying insects must control their flight so that their sensory systems have time to detect obstacles and avoid them. To do this, day-active insects rely primarily on the pattern of apparent motion generated on the retina during flight (optic flow). However, many flying insects are active at night, when obtaining reliable visual information for flight control presents much more of a challenge. To assess whether nocturnal flying insects also rely on optic flow cues to control flight in dim light, we recorded flights of the nocturnal neotropical sweat bee, Megalopta genalis, flying along an experimental tunnel when: (i) the visual texture on each wall generated strong horizontal (front-to-back) optic flow cues, (ii) the texture on only one wall generated these cues, and (iii) horizontal optic flow cues were removed from both walls. We find that Megalopta increase their groundspeed when horizontal motion cues in the tunnel are reduced (conditions (ii) and (iii)). However, differences in the amount of horizontal optic flow on each wall of the tunnel (condition (ii)) do not affect the centred position of the bee within the flight tunnel. To better understand the behavioural response of Megalopta, we repeated the experiments on day-active bumble-bees (Bombus terrestris). Overall, our findings demonstrate that despite the limitations imposed by dim light, Megalopta-like their day-active relatives-rely heavily on vision to control flight, but that they use visual cues in a different manner from diurnal insects.

  1. Nocturnal insects use optic flow for flight control

    PubMed Central

    Baird, Emily; Kreiss, Eva; Wcislo, William; Warrant, Eric; Dacke, Marie

    2011-01-01

    To avoid collisions when navigating through cluttered environments, flying insects must control their flight so that their sensory systems have time to detect obstacles and avoid them. To do this, day-active insects rely primarily on the pattern of apparent motion generated on the retina during flight (optic flow). However, many flying insects are active at night, when obtaining reliable visual information for flight control presents much more of a challenge. To assess whether nocturnal flying insects also rely on optic flow cues to control flight in dim light, we recorded flights of the nocturnal neotropical sweat bee, Megalopta genalis, flying along an experimental tunnel when: (i) the visual texture on each wall generated strong horizontal (front-to-back) optic flow cues, (ii) the texture on only one wall generated these cues, and (iii) horizontal optic flow cues were removed from both walls. We find that Megalopta increase their groundspeed when horizontal motion cues in the tunnel are reduced (conditions (ii) and (iii)). However, differences in the amount of horizontal optic flow on each wall of the tunnel (condition (ii)) do not affect the centred position of the bee within the flight tunnel. To better understand the behavioural response of Megalopta, we repeated the experiments on day-active bumble-bees (Bombus terrestris). Overall, our findings demonstrate that despite the limitations imposed by dim light, Megalopta—like their day-active relatives—rely heavily on vision to control flight, but that they use visual cues in a different manner from diurnal insects. PMID:21307047

  2. Operation of the unified power flow controller as harmonic isolator

    SciTech Connect

    Enslin, J.H.R.; Zhao, J.; Spee, R.

    1996-11-01

    The unified power flow controller (UPFC) is a tool in the implementation of Flexible AC Transmission Systems (FACTS). It provides for the equivalent of static VAr compensation and series injection using back-to-back force commutated converters. This paper proposes a control strategy to extend UPFC operation to allow for the isolation of harmonics due to nonlinear loads. Simulation results based on the Electromagnetic Transients Program (EMTP) are used to illustrate device performance in a power system environment. Experimental results based on a single phase laboratory implementation verify the proposed control algorithm.

  3. Apparatus for controlling fluid flow in a conduit wall

    DOEpatents

    Glass, S. Jill; Nicolaysen, Scott D.; Beauchamp, Edwin K.

    2003-05-13

    A frangible rupture disk and mounting apparatus for use in blocking fluid flow, generally in a fluid conducting conduit such as a well casing, a well tubing string or other conduits within subterranean boreholes. The disk can also be utilized in above-surface pipes or tanks where temporary and controllable fluid blockage is required. The frangible rupture disk is made from a pre-stressed glass with controllable rupture properties wherein the strength distribution has a standard deviation less than approximately 5% from the mean strength. The frangible rupture disk has controllable operating pressures and rupture pressures.

  4. Feedback control of flow vorticity at low Reynolds numbers.

    PubMed

    Zeitz, Maria; Gurevich, Pavel; Stark, Holger

    2015-03-01

    Our aim is to explore strategies of feedback control to design and stabilize novel dynamic flow patterns in model systems of complex fluids. To introduce the control strategies, we investigate the simple Newtonian fluid at low Reynolds number in a circular geometry. Then, the fluid vorticity satisfies a diffusion equation. We determine the mean vorticity in the sensing area and use two control strategies to feed it back into the system by controlling the angular velocity of the circular boundary. Hysteretic feedback control generates self-regulated stable oscillations in time, the frequency of which can be adjusted over several orders of magnitude by tuning the relevant feedback parameters. Time-delayed feedback control initiates unstable vorticity modes for sufficiently large feedback strength. For increasing delay time, we first observe oscillations with beats and then regular trains of narrow pulses. Close to the transition line between the resting fluid and the unstable modes, these patterns are relatively stable over long times.

  5. Optimization of Feedback Control of Flow over a Circular Cylinder

    NASA Astrophysics Data System (ADS)

    Son, Donggun; Kim, Euiyoung; Choi, Haecheon

    2012-11-01

    We perform a feedback gain optimization of the proportional-integral-differential (PID) control for flow over a circular cylinder at Re = 60 and 100. We measure the transverse velocity at a centerline location in the wake as a sensing variable and provide blowing and suction at the upper and lower slots on the cylinder surface as an actuation. The cost function to minimize is defined as the mean square of the sensing variable, and the PID control gains are optimized by iterative feedback tuning method which is a typical model free gain optimization method. In this method, the control gains are iteratively updated by the gradient of cost function until the control system satisfies a certain stopping criteria. The PID control with optimal control gains successfully reduces the velocity fluctuations at the sensing location and attenuates (or annihilates) vortex shedding in the wake, resulting in the reduction in the mean drag and lift fluctuations. Supported by the NRF Program (2011-0028032).

  6. Vortex generator for controlling the dispersion of effluents in a flowing liquid

    NASA Technical Reports Server (NTRS)

    Costen, R. C. (Inventor)

    1977-01-01

    A method is disclosed for controlling the dispersion of effluents in a flowing liquid. A vortex generator for creating a distinct recirculating vortical flow is disposed in a flowing liquid and effluents are discharged into the vortical flow. The effluents are entrained in the vortical flow and by selectively positioning the vortex generator the dispersion of the entrained effluents can be controlled.

  7. Linear stability and control of swept Hiemenz flow

    NASA Astrophysics Data System (ADS)

    Guegan, Alan; Schmid, Peter; Huerre, Patrick

    2004-11-01

    Perturbations at the leading edge of swept wings may feed the downstream flow and trigger early boundary layer transition. Control strategies focusing on the leading edge boundary layer may provide significant improvement of flow stability over the wing surface. To this end, a gradient-based optimization algorithm is implemented to find the perturbations that experience the highest energy growth in swept Hiemenz flow over a finite time interval, under the Görtler-Hämmerlin assumption. A two-dimensional mechanism resembling the Orr-mechanism in the spanwise-wall-normal plane is shown to generate energy growth of up to three orders of magnitude for a Reynolds number Re=2000 and a spanwise wavenumber k=0.1. A similar algorithm is used to compute the wall-normal blowing/sucking sequence that most efficiently damps the energy amplification. The maximum energy is then found to decrease by more than 70%.

  8. Vacuum rated flow controllers for inert gas ion engines

    NASA Technical Reports Server (NTRS)

    Pless, L. C.

    1987-01-01

    Electrical propulsion systems which use a gas as a propellant require a gas flowmeter/controller which is capable of operating in a vacuum environment. The presently available instruments in the required flow ranges are designed and calibrated for use at ambient pressure. These instruments operate by heating a small diameter tube through which the gas is flowing and then sensing the change in temperature along the length of the tube. This temperature change is a function of the flow rate and the gas heat capacity. When installed in a vacuum, the change in the external thermal characteristics cause the tube to overheat and the temperature sensors are then operating outside their calibrated range. In addition, the variation in heat capacity with temperature limit the accuracy obtainable. These problems and the work in progress to solve them are discussed.

  9. Vacuum rated flow controllers for inert gas ion engines

    NASA Technical Reports Server (NTRS)

    Pless, L. C.

    1987-01-01

    Electrical propulsion systems which use a gas as a propellant require a gas flowmeter/controller which is capable of operating in a vacuum environment. The presently available instruments in the required flow ranges are designed and calibrated for use at ambient pressure. These instruments operate by heating a small diameter tube through which the gas is flowing and then sensing the change in temperature along the length of the tube. This temperature change is a function of the flow rate and the gas heat capacity. When installed in a vacuum, the change in the external thermal characteristics cause the tube to overheat and the temperature sensors are then operating outside their calibrated range. In addition, the variation in heat capacity with temperature limit the accuracy obtainable. These problems and the work in progress to solve them are discussed.

  10. Probing protein mechanical stability with controlled shear flows

    NASA Astrophysics Data System (ADS)

    Dusting, Jonathan; Ashton, Lorna; Leontini, Justin; Blanch, Ewan; Balabani, Stavroula

    2009-11-01

    Understanding and controlling protein aggregation or misfolding is of both fundamental and medical interest. The structural changes experienced by proteins in response to forces such as those generated within flows have not been well characterised, despite the importance of mechanics in many biological processes. By monitoring the structural conformation of proteins in different concentric cylinder flows using Raman Spectroscopy we have quantified the relative stability of β-sheet dominated proteins compared with those containing a greater proportion of α-helix. To ensure that the fluid stresses are quantified accurately, a combined DNS and PIV approach has been undertaken for flow cell characterisation across the full range of operating Re. This is important for practical concentric cylinder geometries where the shear components are non-zero and spatially dependent, with the peak stresses located near the endwalls. Furthermore, recirculation regions appear well below the crtical Reynolds number for Taylor vortex formation.

  11. Numerical Studies of a Fluidic Diverter for Flow Control

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Kuczmarski, Maria A.; Culley, Dennis E.; Raghu, Surya

    2009-01-01

    The internal flow structure in a specific fluidic diverter is studied over a range from low subsonic to sonic inlet conditions by a time-dependent numerical analysis. The understanding will aid in the development of fluidic diverters with minimum pressure losses and advanced designs of flow control actuators. The velocity, temperature and pressure fields are calculated for subsonic conditions and the self-induced oscillatory behavior of the flow is successfully predicted. The results of our numerical studies have excellent agreement with our experimental measurements of oscillation frequencies. The acoustic speed in the gaseous medium is determined to be a key factor for up to sonic conditions in governing the mechanism of initiating the oscillations as well as determining its frequency. The feasibility of employing plasma actuation with a minimal perturbation level is demonstrated in steady-state calculations to also produce oscillation frequencies of our own choosing instead of being dependent on the fixed-geometry fluidic device.

  12. Receptivity and control in non-parallel flows

    NASA Astrophysics Data System (ADS)

    Hill, D. C.

    1996-11-01

    The receptivity problem for non-parallel compressible flow over general airfoil geometries has been investigated using the adjoint parabolized stability equations (PSE). The excitation of TS waves by acoustic scattering due to localized surface suction is modeled, and compared with direct numerical simulations by Crouch & Spalart(Crouch, J.D. & Spalart, P.R., 1995. A study of non-parallel and nonlinear effects on the localized receptivity of boundary layers. J. Fluid Mech.,) Vol. 290.. The excitation of crossflow vortices on a NACA 64A010 airfoil at 53 degrees sweep in a Mach 1.5 flow is also investigated. The features of the boundary layer profile to which the vortex growth rate is most sensitive are identified. These sensitivity data can be exploited for the design of optimum laminar wings or flow-control systems.

  13. Modeling and control of flow-induced vibrations of a flexible hydrofoil in viscous flow

    NASA Astrophysics Data System (ADS)

    Caverly, Ryan James; Li, Chenyang; Chae, Eun Jung; Forbes, James Richard; Young, Yin Lu

    2016-06-01

    In this paper, a reduced-order model (ROM) of the flow-induced vibrations of a flexible cantilevered hydrofoil is developed and used to design an active feedback controller. The ROM is developed using data from high-fidelity viscous fluid-structure interaction (FSI) simulations and includes nonlinear terms to accurately capture the effect of lock-in. An active linear quadratic Gaussian (LQG) controller is designed based on a linearization of the ROM and is implemented in simulation with the ROM and the high-fidelity viscous FSI model. A controller saturation method is also presented that ensures that the control force applied to the system remains within a prescribed range. Simulation results demonstrate that the LQG controller successfully suppresses vibrations in both the ROM and viscous FSI simulations using a reasonable amount of control force.

  14. Enabling Technologies for Microfluidic Flow Control and Detection

    NASA Astrophysics Data System (ADS)

    Leslie, Daniel Christopher

    Advances in microfluidic technologies have expanded conventional chemical and biological techniques to the point where we can envision rapid, inexpensive and portable analysis. Among the numerous challenges in the development of portable, chip-based technologies are simple flow control and detection strategies, which will be essential to widespread acceptance and implementation at both the point-of-care and in locales with limited facilities/resources. The research presented in this dissertation is focused on the development of precise flow control techniques and new, simplified detection technologies aimed at addressing these challenges. An introduction to the concepts important to microfluidics and a brief history to the field are presented in Chapter 1. Chapter 2 will present the development of a technique for the precise control of small volumes of liquids, where well-studied electrical circuit concepts are employed to create frequency-dependent microfluidic circuits. In this system, elastomeric thin films act as fluidic capacitors and diodes, which, when combined with resistors (channels), make fluidic circuits that are described by analytical models. Metering of two separate chemical inputs with a single oscillatory pneumatic control line is demonstrated by combining simple fluidic circuits (i.e., band-pass filters) to significantly reduce the external hardware required for microfluidic flow control. In order to quantify multiple flow profiles in microfluidic circuits, a novel multiplexed flow measurement method using visible dyes is introduced in Chapter 3 and rapidly determines individual flow in connected channels, post-fabrication device quality and solution viscosity. Another thrust of this dissertation research has been to develop miniaturized bioanalytical systems. Chapter 4 describes the adaption of a nucleic-acid-tagged antibody protein detection reaction to a microfluidic platform for detection of down to 5 E. coli O157:H7 cells. Furthermore, a

  15. Numerical simulation of flow separation control by oscillatory fluid injection

    NASA Astrophysics Data System (ADS)

    Resendiz Rosas, Celerino

    2005-07-01

    In this work, numerical simulations of flow separation control are performed. The separation control technique studied is called "synthetic jet actuation". The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing significant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 airfoil. For this flow Re = 9 x 105 and the reduced frequency and momentum coefficient are F + = 1.1 and Cmu = 0.04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, however, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model. A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F+ ≈ O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields obtained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the

  16. Active Flow Control of a Transonic Shock over Curved Surfaces

    NASA Astrophysics Data System (ADS)

    Gissen, Abraham N.; Vukasinovic, Bojan; Glezer, Ari; Gogineni, Sivaram P.

    2013-11-01

    The effects of fluidic actuation on the evolution and dynamics of a transonic shock over a two-dimensional convex surface by controlling the ensuing shock-induced separation are investigated in wind tunnel experiments. Actuation is effected by a spanwise array of high-frequency (nominally 10 kHz) fluidic oscillating jets. The flow field upstream and downstream of the shock is investigated using high-speed Schlieren and PIV (3,000fps), and surface pressure measurements. It is shown that control of the shock-induced separating shear layer by exploiting direct control of small-scale motion can alter the degree of flow attachment and have a profound effect on the shock dynamics. The actuation diminishes shock oscillations near the surface, and leads to streamwise shock displacement that is proportional to the actuation strength (as measured, for example, by the mass flow rate coefficient). The strong correlation between the shock displacement and surface pressure are explored for application of closed-loop control.

  17. Magnetic Amplifier-Based Power-Flow Controller

    DOE PAGES

    Dimitrovski, Aleksandar; Li, Zhi; Ozpineci, Burak

    2015-02-05

    The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. In this paper, we introduce the magnetic amplifier-based power-flow controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can bemore » regulated by the small dc input to the dc winding. Moreover, a project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.« less

  18. Adaptive Identification and Control of Flow-Induced Cavity Oscillations

    NASA Technical Reports Server (NTRS)

    Kegerise, M. A.; Cattafesta, L. N.; Ha, C.

    2002-01-01

    Progress towards an adaptive self-tuning regulator (STR) for the cavity tone problem is discussed in this paper. Adaptive system identification algorithms were applied to an experimental cavity-flow tested as a prerequisite to control. In addition, a simple digital controller and a piezoelectric bimorph actuator were used to demonstrate multiple tone suppression. The control tests at Mach numbers of 0.275, 0.40, and 0.60 indicated approx. = 7dB tone reductions at multiple frequencies. Several different adaptive system identification algorithms were applied at a single freestream Mach number of 0.275. Adaptive finite-impulse response (FIR) filters of orders up to N = 100 were found to be unsuitable for modeling the cavity flow dynamics. Adaptive infinite-impulse response (IIR) filters of comparable order better captured the system dynamics. Two recursive algorithms, the least-mean square (LMS) and the recursive-least square (RLS), were utilized to update the adaptive filter coefficients. Given the sample-time requirements imposed by the cavity flow dynamics, the computational simplicity of the least mean squares (LMS) algorithm is advantageous for real-time control.

  19. Magnetic Amplifier-Based Power-Flow Controller

    SciTech Connect

    Dimitrovski, Aleksandar; Li, Zhi; Ozpineci, Burak

    2015-02-05

    The concept of the magnetic amplifier, a common electromagnetic device in electronic applications in the past, has seldom been used in power systems. In this paper, we introduce the magnetic amplifier-based power-flow controller (MAPFC), an innovative low-cost device that adopts the idea of the magnetic amplifier for power-flow control applications. The uniqueness of MAPFC is in the use of the magnetization of the ferromagnetic core, shared by an ac and a dc winding, as the medium to control the ac winding reactance inserted in series with the transmission line to be controlled. Large power flow in the line can be regulated by the small dc input to the dc winding. Moreover, a project on the R&D of an MAPFC has been funded by the U.S. Department of Energy (DOE) and conducted by the Oak Ridge National Laboratory (ORNL), the University of Tennessee-Knoxville, and Waukesha Electric Systems, Inc. since early 2012. Findings from the project are presented along with some results obtained in a laboratory environment.

  20. Model reduction and feedback control of transitional channel flow

    NASA Astrophysics Data System (ADS)

    Ilak, Milos

    This dissertation examines the use of reduced-order models for design of linear feedback controllers for fluid flows. The focus is on transitional channel flow, a canonical shear flow case with a simple geometry yet complex dynamics. Reduced-order models of the linearized Navier-Stokes equations, which describe the evolution of perturbations in transitional channel flow, are computed using two methods for snapshot-based balanced truncation, Balanced Proper Orthogonal Decomposition (BPOD) and Eigensystem Realization Algorithm (ERA). The performance of these models in feedback control is evaluated in both linearized and nonlinear Direct Numerical Simulations (DNS) of channel flow. The first part of the dissertation describes the application of BPOD to very large systems, and the detailed evaluation of the resulting reduced-order models. Exact balanced truncation, a standard method from control theory, is not computationally tractable for very large systems, such as those typically encountered in fluid flow simulations. The BPOD method, introduced by Rowley (2005), provides a close approximation. We first show that the approximation is indeed close by applying the method to a 1-D linear perturbation to channel flow at a single spatial wavenumber pair, for which exact balanced truncation is tractable. Next, as the first application of BPOD to a very high-dimensional linear system, we show that reduced-order BPOD models of a localized 3-D perturbation capture the dynamics very well. Moreover, the BPOD models significantly outperform standard Proper Orthogonal Decomposition (POD) models, as illustrated by a striking example where models using the POD modes that capture most of the perturbation energy fail to capture the perturbation dynamics. Next, reduced-order models of a complete control system for linearized channel flow are obtained using ERA, a computationally efficient method that results in the same reduced-order models as BPOD. Linear Quadratic Gaussian (LQG

  1. Development of flow/steric field-flow fractionation as a routine process control method

    SciTech Connect

    Barman, B.N.

    1988-08-30

    Researchers studied the feasibility of using the Flow/Steric Field-Flow Fractionation (Flow/StFFF) method for the characterization of particulate materials with diameters in the 1-100 micrometers range. Studies on the optimization of the method for the separation and characterization of different size particulate samples, as well as on the role of the crossflow field and channel flowrate on the separation and resolution, were performed with a number of spherical polystyrene divinylbenzene latex standards and included in the report. Applicability of the method as a fast and reliable practical tool for industrial process control, particularly for grinding operations, was examined by analyzing a number of samples obtained by grinding. Examples of materials considered include coal, limestone and glass.

  2. Geomorphological control on groundwater flow, transit times and water quality

    NASA Astrophysics Data System (ADS)

    de Dreuzy, Jean-Raynald; Marçais, Jean; Kolbe, Tamara; Courtois, Quentin; Longuevergne, Laurent; Steer, Philippe; Davy, Philippe; Thomas, Zahra; Le Carlier, Christian; Guillocheau, François; Pinay, Gilles

    2017-04-01

    In weathered zones, subsurface flows remain shallow and strongly depend on the geomorphological evolution of the landscape. Weathered profiles have limited depths. Subsurface circulations follow the structure of the hydrological catchment. Surface and subsurface flows are strongly coupled by rapid responses of saturations to recharge. Some of the circulations are indeed fast with surface/subsurface signatures and transit times of the order of some weeks to some months. Most of the water is however much older as revealed by anthropogenic tracers. For example, in the western crystalline basement of France, characteristic transit times are more of the order of decades. Detailed groundwater flow and transport modelling in well-documented sites show that behaviour of weathered zones is intermediary between hydrology and hydrogeology. While organization of flows is strongly constrained by topography like for hydrology, transit times are however much longer like in hydrogeology. Based on several catchments, we propose quantitative indicators to relate geomorphology with subsurface flow organization. We integrate geological constrains and saturation capacities to derive transit-time dynamics. We discuss the consequences on water quality linked to kinetically-controlled degradation of non-point source contaminants.

  3. Formation of surface nanodroplets under controlled flow conditions

    NASA Astrophysics Data System (ADS)

    Lohse, Detlef; Zhang, Xuehua; Lu, Ziyang; Tan, Huanshu; Bao, Lei; He, Yinghe; Sun, Chao

    2015-11-01

    Nanodroplets on a solid surface (i.e. surface nanodroplets) have practical implications for high-throughput chemical and biological analysis, lubrications, lab-on-chip devices, and near-field imaging techniques. Oil nanodroplets can be produced on a solid-liquid interface in a simple step of solvent exchange in which a good solvent of oil is displaced by a poor solvent. In this work, we experimentally and theoretically investigate the formation of nanodroplets by the solvent exchange process under well-controlled flow conditions. We find significant effects from the flow rate and the flow geometry on the droplet size. We develop a theoretical framework to account for these effects. The main idea is that the droplet nuclei are exposed to an oil oversaturation pulse during the exchange process. The analysis gives that the volume of the nanodroplets increases with the Peclet number Pe of the flow as ~ Pe 3 / 4 , which is in good agreement with our experimental results. In addition, at fixed flow rate and thus fixed Peclet number, larger and less homogeneously distributed droplets formed at less narrow channels, due to convection effects originating from the density difference between the two solutions of the solvent exchange.

  4. Application of the FUN3D Unstructured-Grid Navier-Stokes Solver to the 4th AIAA Drag Prediction Workshop Cases

    NASA Technical Reports Server (NTRS)

    Lee-Rausch, Elizabeth M.; Hammond, Dana P.; Nielsen, Eric J.; Pirzadeh, S. Z.; Rumsey, Christopher L.

    2010-01-01

    FUN3D Navier-Stokes solutions were computed for the 4th AIAA Drag Prediction Workshop grid convergence study, downwash study, and Reynolds number study on a set of node-based mixed-element grids. All of the baseline tetrahedral grids were generated with the VGRID (developmental) advancing-layer and advancing-front grid generation software package following the gridding guidelines developed for the workshop. With maximum grid sizes exceeding 100 million nodes, the grid convergence study was particularly challenging for the node-based unstructured grid generators and flow solvers. At the time of the workshop, the super-fine grid with 105 million nodes and 600 million elements was the largest grid known to have been generated using VGRID. FUN3D Version 11.0 has a completely new pre- and post-processing paradigm that has been incorporated directly into the solver and functions entirely in a parallel, distributed memory environment. This feature allowed for practical pre-processing and solution times on the largest unstructured-grid size requested for the workshop. For the constant-lift grid convergence case, the convergence of total drag is approximately second-order on the finest three grids. The variation in total drag between the finest two grids is only 2 counts. At the finest grid levels, only small variations in wing and tail pressure distributions are seen with grid refinement. Similarly, a small wing side-of-body separation also shows little variation at the finest grid levels. Overall, the FUN3D results compare well with the structured-grid code CFL3D. The FUN3D downwash study and Reynolds number study results compare well with the range of results shown in the workshop presentations.

  5. Controls on matrix flow, preferential flow and deep drainage rates in an alluvial Vertisol.

    NASA Astrophysics Data System (ADS)

    Arnold, Sven; Larsen, Joshua; Reading, Lucy; Finch, Warren; Bulovic, Nevenka; McIntyre, Neil

    2016-04-01

    Deep drainage is the process that describes water percolating from the land surface to a depth below the root zone where it may contribute to groundwater recharge. Quantitative estimation of deep drainage through Vertisols is challenging, largely due to the unknown relative contributions from: (i) flow through the soil matrix; and (ii) flow along preferential pathways in particular soil cracks, and how to model the transience of the relative contributions. The Condamine River Alluvium, a significant aquifer in semi-arid eastern Australia, is mostly covered by uniform dark cracking clays such as Black and Grey Vertisols. The aim of this study was to identify the environmental conditions (rainfall, antecedent soil moisture, etc) controlling matrix and preferential flow in selected Vertisol profiles at the time scale of individual rainfall events. Field experiments (including 16 probes recording soil moisture at one hour intervals across eight depths between 100 mm and 4000 mm) provide extensive soil moisture data, supplemented by weather station data collected at 15-minute intervals. In addition, laboratory experiments were used to infer the water retention curves. These data were used to (i) derive deep drainage rates using the zero-flux plane method, and (ii) calibrate a soil moisture balance model that represents both matrix and preferential flow. The model was used to estimate the parts of the vertical water flux attributed to soil matrix and preferential flow. High antecedent soil moisture was associated with low fluxes at shallow depths, however at deeper depths both low and high antecedent soil moisture were associated with larger fluxes. Further, both rainfall amount and intensity controlled the interplay between matrix and preferential flow. The results reveal new insights into deep drainage processes in Vertisols and provide the basis for developing a practical approach for deep drainage estimation.

  6. Integration and Modulation of Intercellular Signaling Underlying Blood Flow Control

    PubMed Central

    Segal, Steven S.

    2015-01-01

    Vascular resistance networks control tissue blood flow in concert with regulating arterial perfusion pressure. In response to increased metabolic demand, vasodilation arising in arteriolar networks ascends to encompass proximal feed arteries. By reducing resistance upstream, ascending vasodilation (AVD) increases blood flow into the microcirculation. Once initiated [e.g., through local activation of K+ channels in endothelial cells (ECs)], hyperpolarization is conducted through gap junctions along the endothelium. Via EC projections through the internal elastic lamina, hyperpolarization spreads into the surrounding smooth muscle cells (SMCs) through myoendothelial gap junctions (MEGJs) to promote their relaxation. Intercellular signaling through electrical signal transmission (i.e., cell-to-cell conduction) can thereby coordinate vasodilation along and among the branches of microvascular resistance networks. Perivascular sympathetic nerve fibers course through the adventitia and release norepinephrine to stimulate SMCs via α-adrenoreceptors to produce contraction. In turn, SMCs can signal ECs through MEGJs to activate K+ channels and attenuate sympathetic vasoconstriction. Activation of K+ channels along the endothelium will dissipate electrical signal transmission and inhibit AVD, thereby restricting blood flow into the microcirculation while maintaining peripheral resistance and perfusion pressure. This review explores the origins and nature of intercellular signaling governing blood flow control in skeletal muscle with respect to the interplay between AVD and sympathetic innervation. Whereas these interactions are integral to physical daily activity and athletic performance, resolving the interplay between respective signaling events provides insight into how selective interventions can improve tissue perfusion and oxygen delivery during vascular disease. PMID:26368324

  7. Development of an Actuator for Flow Control Utilizing Detonation

    NASA Technical Reports Server (NTRS)

    Lonneman, Patrick J.; Cutler, Andrew D.

    2004-01-01

    Active flow control devices including mass injection systems and zero-net-mass flux actuators (synthetic jets) have been employed to delay flow separation. These devices are capable of interacting with low-speed, subsonic flows, but situations exist where a stronger crossflow interaction is needed. Small actuators that utilize detonation of premixed fuel and oxidizer should be capable of producing supersonic exit jet velocities. An actuator producing exit velocities of this magnitude should provide a more significant interaction with transonic and supersonic crossflows. This concept would be applicable to airfoils on high-speed aircraft as well as inlet and diffuser flow control. The present work consists of the development of a detonation actuator capable of producing a detonation in a single shot (one cycle). Multiple actuator configurations, initial fill pressures, oxidizers, equivalence ratios, ignition energies, and the addition of a turbulence generating device were considered experimentally and computationally. It was found that increased initial fill pressures and the addition of a turbulence generator aided in the detonation process. The actuators successfully produced Chapman-Jouguet detonations and wave speeds on the order of 3000 m/s.

  8. Controlling Compressor Vane Flow Vectoring Angles at Transonic Speeds

    NASA Astrophysics Data System (ADS)

    Munson, Matthew; Rempfer, Dietmar; Williams, David; Acharya, Mukund

    2003-11-01

    The ability to control flow separation angles from compressor inlet guide vanes with a Coanda-type actuator is demonstrated using both wind tunnel experiments and finite element simulations. Vectoring angles up to 40 degrees from the uncontrolled baseline state were measured with helium schlieren visualization at transonic Mach numbers ranging from 0.1 to 0.6, and with airfoil chord Reynolds numbers ranging from 89,000 to 710,000. The magnitude of the vectoring angle is shown to depend upon the geometry of the trailing edge, and actuator slot size, and the momentum flux coefficient. Under certain conditions the blowing has no effect on the vectoring angle indicating that the Coanda effect is not present. DNS simulations with the finite element method investigated the effects of geometry changes and external flow. Continuous control of the vectoring angle is demonstrated, which has important implications for application to rotating machinery. The technique is shown to reduce the stall flow coefficient by 15 percent in an axial flow compressor.

  9. CFD Study of NACA 0018 Airfoil with Flow Control

    NASA Technical Reports Server (NTRS)

    Eggert, Christopher A.; Rumsey, Christopher L.

    2017-01-01

    The abilities of two different Reynolds-Averaged Navier-Stokes codes to predict the effects of an active flow control device are evaluated. The flow control device consists of a blowing slot located on the upper surface of an NACA 0018 airfoil, near the leading edge. A second blowing slot present on the airfoil near mid-chord is not evaluated here. Experimental results from a wind tunnel test show that a slot blowing with high momentum coefficient will increase the lift of the airfoil (compared to no blowing) and delay flow separation. A slot with low momentum coefficient will decrease the lift and induce separation even at low angles of attack. Two codes, CFL3D and FUN3D, are used in two-dimensional computations along with several different turbulence models. Two of these produced reasonable results for this flow, when run fully turbulent. A more advanced transition model failed to predict reasonable results, but warrants further study using different inputs. Including inviscid upper and lower tunnel walls in the simulations was found to be important in obtaining pressure distributions and lift coefficients that best matched experimental data. A limited number of three-dimensional computations were also performed.

  10. Control of continuous polyhydroxybutyrate synthesis using calorimetry and flow cytometry.

    PubMed

    Maskow, Thomas; Müller, Susann; Lösche, Andreas; Harms, Hauke; Kemp, Richard

    2006-02-20

    The substrate-carbon flow can be controlled in continuous bioreactor cultures by the medium composition, for example, by the C/N ratio. The carbon distribution is optimal when a maximum fraction flows into the desired product and the residual is just sufficient to compensate for the dilution of the microbial catalyst. Undershooting of the latter condition is reflected immediately by changes in the Gibbs energy dissipation and cellular states. Two calorimetric measurement principles were applied to optimize the continuous synthesis of polyhydroxybutyrate (PHB) by Variovorax paradoxus DSM4065 during growth with constantly increasing supply rates of fructose or toxic phenol. Firstly, the changed slope of the heat production rate in a complete heat balanced bioreactor (CHB) indicated optimum carbon channeling into PHB. The extent of the alteration depended directly on the toxic properties of the substrate. Secondly, a flow through calorimeter was connected with the bioreactor as a "measurement loop." The optimum substrate carbon distribution was indicated by a sudden change in the heat production rate independent of substrate toxicity. The sudden change was explained mathematically and exploited for the long-term control of phenol conversion into PHB. LASER flow cytometry measurements distinguished between subpopulations with completely different PHB-content. Populations grown on fructose preserved a constant ratio of two subpopulations with double and quadruple sets of DNA. Cells grown on phenol comprised a third subpopulation with a single DNA set. Rising phenol concentrations caused this subpopulation to increase. It may thus be considered as an indicator of chemostress.

  11. Control of cutaneous blood flow by central nervous system

    PubMed Central

    Ootsuka, Youichirou; Tanaka, Mutsumi

    2015-01-01

    Hairless skin acts as a heat exchanger between body and environment, and thus greatly contributes to body temperature regulation by changing blood flow to the skin (cutaneous) vascular bed during physiological responses such as cold- or warm-defense and fever. Cutaneous blood flow is also affected by alerting state; we ‘go pale with fright’. The rabbit ear pinna and the rat tail have hairless skin, and thus provide animal models for investigating central pathway regulating blood flow to cutaneous vascular beds. Cutaneous blood flow is controlled by the centrally regulated sympathetic nervous system. Sympathetic premotor neurons in the medullary raphé in the lower brain stem are labeled at early stage after injection of trans-synaptic viral tracer into skin wall of the rat tail. Inactivation of these neurons abolishes cutaneous vasomotor changes evoked as part of thermoregulatory, febrile or psychological responses, indicating that the medullary raphé is a common final pathway to cutaneous sympathetic outflow, receiving neural inputs from upstream nuclei such as the preoptic area, hypothalamic nuclei and the midbrain. Summarizing evidences from rats and rabbits studies in the last 2 decades, we will review our current understanding of the central pathways mediating cutaneous vasomotor control. PMID:27227053

  12. Optimal Control of Airfoil Flow Separation using Fluidic Excitation

    NASA Astrophysics Data System (ADS)

    Shahrabi, Arireza F.

    This thesis deals with the control of flow separation around a symmetric airfoils with the aid of multiple synthetic jet actuators (SJAs). CFD simulation methods have been implemented to uncover the flow separation regimes and associated properties such as frequencies and momentum ratio. In the first part of the study, the SJA was studied thoroughly. Large Eddy Simulations (LES) were performed for one individual cavity; the time history of SJA of the outlet velocity profile and the net momentum imparted to the flow were analyzed. The studied SJA is asymmetrical and operates with the aid of a piezoelectric (PZT) ceramic circular plate actuator. A three-dimensional mesh for the computational domain of the SJA and the surrounding volume was developed and was used to evaluate the details of the airflow conditions inside the SJA as well as at the outlet. The vibration of the PZT ceramic actuator was used as a boundary condition in the computational model to drive the SJA. Particular attention was given to developing a predictive model of the SJA outlet velocity. Results showed that the SJA velocity output is correlated to the PZT ceramic plate vibration, especially for the first frequency mode. SJAs are a particular class of zero net mass flux (ZNMF) fluidic devices with net imparted momentum to the flow. The net momentum imparted to the flow in the separated region is such that positive enhancement during AFC operations is achieved. Flows around the NACA 0015 airfoil were simulated for a range of operating conditions. Attention was given to the active open and closed loop control solutions for an airfoil with SJA at different angles of attack and flap angles. A large number of simulations using RANS & LES models were performed to study the effects of the momentum ratio (Cμ) in the range of 0 to 11% and of the non-dimensional frequency, F+, in the range of 0 to 2 for the control of flow separation at a practical angle of attack and flap angle. The optimum value of C

  13. Active Flow Control on Laminar flow over a Backward facing step

    NASA Astrophysics Data System (ADS)

    Mushyam, Aditya; Bergada, Josep M.

    2015-09-01

    In the present study, two dimensional flow over a backward-facing step in laminar flow regime with application of active flow control (AFC) technique is analysed. The aim of the present work is to gauge the effectiveness of implementing AFC to reduce drag and study its effects on flow characteristics. In order to analyse the influence of AFC on the boundary layer and the downstream vortex shedding, two different kinds of AFC techniques have been used in this study namely zero net mass flow actuators and fluidic actuators. A parametric non dimensional analysis has been carried out by varying the frequency from 0.025 to 0.1 and jet amplitude from 0.05 and 1. Four different positions of the groove were simulated; groove was respectively located at 0.024a, 0.047a, 0.072a and 0.097a, measured upstream from the right side upper edge. Three different non dimensional groove widths 0.023a, 0.048a and 0.073a were also evaluated, where a is the step height. The idea behind this study was to determine an optimal configuration to reduce the drag on the step and to suppress the vortex dissipation in the wake of the step. It was observed that when using an AFC frequency ± 10% of the vortex shedding one, was causing the maximum drag reduction. When comparing the effects of zero net mass flow actuators with the fluidic actuators, it was observed that zero net mass flow actuators were more effective.

  14. Flow control of micro-ramps on supersonic forward-facing step flow

    NASA Astrophysics Data System (ADS)

    Qing-Hu, Zhang; Tao, Zhu; Shihe, Yi; Anping, Wu

    2016-05-01

    The effects of the micro-ramps on supersonic turbulent flow over a forward-facing step (FFS) was experimentally investigated in a supersonic low-noise wind tunnel at Mach number 3 using nano-tracer planar laser scattering (NPLS) and particle image velocimetry (PIV) techniques. High spatiotemporal resolution images and velocity fields of supersonic flow over the testing model were captured. The fine structures and their spatial evolutionary characteristics without and with the micro-ramps were revealed and compared. The large-scale structures generated by the micro-ramps can survive the downstream FFS flowfield. The micro-ramps control on the flow separation and the separation shock unsteadiness was investigated by PIV results. With the micro-ramps, the reduction in the range of the reversal flow zone in streamwise direction is 50% and the turbulence intensity is also reduced. Moreover, the reduction in the average separated region and in separation shock unsteadiness are 47% and 26%, respectively. The results indicate that the micro-ramps are effective in reducing the flow separation and the separation shock unsteadiness. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172326 and 11502280).

  15. Modeling, simulation, and control of cavity flow oscillations

    NASA Astrophysics Data System (ADS)

    Rowley, Clarence W.

    2002-09-01

    This thesis involves the modeling of self-sustained oscillations in the flow past a rectangular cavity. The emphasis is on developing low-dimensional models that are suitable for analysis using tools from dynamical systems and control theory. Two-dimensional direct numerical simulations are performed, and indicate the presence of a "wake mode," which has been observed previously in experiments, but which is much less well understood than the "shear-layer mode" usually observed. We characterize the flow in both shear-layer mode and wake mode, and provide a criterion for predicting the onset of wake mode, as a function of the various geometrical and flow-related parameters. We focus on the modeling of shear-layer mode, and employ two distinct modeling approaches: first, we use the method of Proper Orthogonal Decomposition (POD) and Galerkin projection to reduce the Navier-Stokes equations to a low-dimensional system of ordinary differential equations (ODEs). We extend the method to compressible flows, using approximations that are valid for cold flows at moderate Mach number. In a compressible flow, both the kinematic and thermodynamic variables contribute to the total energy, and an inner product is introduced which respects this, and allows one to use vector-valued POD modes for the Galerkin projection, We obtain models in the form of ODEs with between 2 and 60 states, and compare models based on scalar-valued and vector-valued POD modes. All of the models work well for short times (a few periods of oscillation), but the models based on scalar-valued modes deviate for longer times, while in general the models based on vector-valued modes retain qualitatively correct dynamical behavior. In the second modeling approach, we model the underlying physical mechanisms separately (shear-layer amplification, acoustic scattering, acoustic propagation), and obtain linear models that are suitable for control design and analysis. We design a controller which stabilizes the

  16. Electronic flow rate controller for a portable insulin infusion pump.

    PubMed

    Ferguson, R T; Zinman, B; Marliss, E B; Albisser, A M

    1980-01-01

    An electronic controller is described that regulates the flow of infusate by controlling the fraction of time that a pump is energized. Using the integral programming capability of the device, any one of 256 possible basal rates between 0 and 49.6% of the maximum rate can be chosen. An externally triggerable single meal-associated pulse can also be configured. The rate during the meal pulse can be any one of the 255 equally spaced rates in the range of 0--99.7%. The duration of this pulse can be chosen in 3-min steps to a maximum of 12.75 h, after which the rate automatically returns to the basal value. The controller consumes a minimum amount of power and can continuously operate a dc motor-driven pump at 3.0 V for 36 h. It drives the pump in an on-off mode in order to control the average flow rate digitally. In this way a significant reduction in the power requirements is realized and the system can be run for many days using small rechargeable batteries. One year of experience with 20 of these controllers was obtained in the research laboratory and clinical investigation unit. The results of this experience indicated the reliability and precision of these controllers, gave insight into their modes of failure, and provided valuable biomedical data for their improvement.

  17. Development of laminar flow control wing surface porous structure

    NASA Technical Reports Server (NTRS)

    Klotzsche, M.; Pearce, W.; Anderson, C.; Thelander, J.; Boronow, W.; Gallimore, F.; Brown, W.; Matsuo, T.; Christensen, J.; Primavera, G.

    1984-01-01

    It was concluded that the chordwise air collection method, which actually combines chordwise and spanwise air collection, is the best of the designs conceived up to this time for full chord laminar flow control (LFC). Its shallower ducting improved structural efficiency of the main wing box resulting in a reduction in wing weight, and it provided continuous support of the chordwise panel joints, better matching of suction and clearing airflow requirements, and simplified duct to suction source minifolding. Laminar flow control on both the upper and lower surfaces was previously reduced to LFC suction on the upper surface only, back to 85 percent chord. The study concludes that, in addition to reduced wing area and other practical advantages, this system would be lighter because of the increase in effective structural wing thickness.

  18. On Mechanism of Plasma-shock-based Flow Control

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Li, Y. H.; Liang, H.; Jia, M.; Song, H. M.

    2011-09-01

    The mechanism of plasma-shock-based flow control was studied. Due to the high reduced electric field strength and peak power in the nanosecond discharge, a large quantity of high-energy electrons are produced. The quenching of the electronically excited states of N2, the dissociation of O2 and N2, and the recombination of molecular ions with electrons cause fast heating of local air near the electrode edge and fast air pressure rise, thus inducing shock waves. The effectiveness of using nanosecond discharge plasma aerodynamic actuation to improve flow separation control capability was validated at the freestream velocity of 150 m/s. Critical stall angle, lift and drag of NACA 0015 airfoil were measured with and without the nanosecond discharge plasma aerodynamic actuation in the wind tunnel experiments.

  19. Improving Advanced Inverter Control Convergence in Distribution Power Flow

    SciTech Connect

    Nagarajan, Adarsh; Palmintier, Bryan; Ding, Fei; Mather, Barry; Baggu, Murali

    2016-11-21

    Simulation of modern distribution system powerflow increasingly requires capturing the impact of advanced PV inverter voltage regulation on powerflow. With Volt/var control, the inverter adjusts its reactive power flow as a function of the point of common coupling (PCC) voltage. Similarly, Volt/watt control curtails active power production as a function of PCC voltage. However, with larger systems and higher penetrations of PV, this active/reactive power flow itself can cause significant changes to the PCC voltage potentially introducing oscillations that slow the convergence of system simulations. Improper treatment of these advanced inverter functions could potentially lead to incorrect results. This paper explores a simple approach to speed such convergence by blending in the previous iteration's reactive power estimate to dampen these oscillations. Results with a single large (5MW) PV system and with multiple 500kW advanced inverters show dramatic improvements using this approach.

  20. Electrically controlled one-way photon flow in plasmonic nanostructures.

    PubMed

    Davoyan, Artur; Engheta, Nader

    2014-11-06

    Photonics is frequently regarded as a potential pathway for substituting current solid-state electronics and as a promise for higher-speed all-optical computing. The fundamental challenges facing nanophotonics and electronics of the future are nanoscale on-chip integration of electronics and photonics with an efficient electric field tuning of light propagation, dynamic access to the light sources and material parameters of the system, as well as isolation of optical signals analogous to that in electronics. Here we suggest a paradigm for a monolithically integrated electronic control over the light propagation in nanoscale plasmonic waveguides. We theoretically demonstrate that magnetic field induced by the direct electric current flowing in metallic constituents of plasmonic nanostructures alters the material parameters and thus the optical signal flow. We use this principle for the design of an electrically controlled subwavelength optical isolator.

  1. Shuttle Gaseous Hydrogen Venting Risk from Flow Control Valve Failure

    NASA Technical Reports Server (NTRS)

    Drummond, J. Philip; Baurle, Robert A.; Gafney, Richard L.; Norris, Andrew T.; Pellett, Gerald L.; Rock, Kenneth E.

    2009-01-01

    This paper describes a series of studies to assess the potential risk associated with the failure of one of three gaseous hydrogen flow control valves in the orbiter's main propulsion system during the launch of Shuttle Endeavour (STS-126) in November 2008. The studies focused on critical issues associated with the possibility of combustion resulting from release of gaseous hydrogen from the external tank into the atmosphere during assent. The Shuttle Program currently assumes hydrogen venting from the external tank will result in a critical failure. The current effort was conducted to increase understanding of the risk associated with venting hydrogen given the flow control valve failure scenarios being considered in the Integrated In-Flight Anomaly Investigation being conducted by NASA.

  2. Stimuli-Responsive Polymer Brushes for Flow Control through Nanopores

    PubMed Central

    Adiga, Shashishekar P.; Brenner, Donald W.

    2012-01-01

    Responsive polymers attached to the inside of nano/micro-pores have attracted great interest owing to the prospect of designing flow-control devices and signal responsive delivery systems. An intriguing possibility involves functionalizing nanoporous materials with smart polymers to modulate biomolecular transport in response to pH, temperature, ionic concentration, light or electric field. These efforts open up avenues to develop smart medical devices that respond to specific physiological conditions. In this work, an overview of nanoporous materials functionalized with responsive polymers is given. Various examples of pH, temperature and solvent responsive polymers are discussed. A theoretical treatment that accounts for polymer conformational change in response to a stimulus and the associated flow-control effect is presented. PMID:24955529

  3. Reliable multicast protocol specifications flow control and NACK policy

    NASA Technical Reports Server (NTRS)

    Callahan, John R.; Montgomery, Todd L.; Whetten, Brian

    1995-01-01

    This appendix presents the flow and congestion control schemes recommended for RMP and a NACK policy based on the whiteboard tool. Because RMP uses a primarily NACK based error detection scheme, there is no direct feedback path through which receivers can signal losses through low buffer space or congestion. Reliable multicast protocols also suffer from the fact that throughput for a multicast group must be divided among the members of the group. This division is usually very dynamic in nature and therefore does not lend itself well to a priori determination. These facts have led the flow and congestion control schemes of RMP to be made completely orthogonal to the protocol specification. This allows several differing schemes to be used in different environments to produce the best results. As a default, a modified sliding window scheme based on previous algorithms are suggested and described below.

  4. Numerical Simulations of Asymmetric Mixing in Planar Shear Flows.

    DTIC Science & Technology

    2014-09-26

    unsteady shear flows with periodic boundary conditions (Riley & Metcalfe 1980), or in previous simulations of the splitter-plate geometry using either...Soloukhin, AIMA. Riley, 3.3. & Metcalfe , R.W. 1980, Direct Numerical simulation or a Perturbed, Turbulent Mixing Layer, AIAA paper 80-02741, Pasadena

  5. Validation of WIND for a Series of Inlet Flows

    NASA Technical Reports Server (NTRS)

    Slater, John W.; Abbott, John M.; Cavicchi, Richard H.

    2002-01-01

    Validation assessments compare WIND CFD simulations to experimental data for a series of inlet flows ranging in Mach number from low subsonic to hypersonic. The validation procedures follow the guidelines of the AIAA. The WIND code performs well in matching the available experimental data. The assessments demonstrate the use of WIND and provide confidence in its use for the analysis of aircraft inlets.

  6. Introduction to flow instability in turbine control valve

    NASA Astrophysics Data System (ADS)

    Kollross, Petr

    2017-09-01

    The purpose of this article is summarize experiments and knowledge about turbine control valves base on published articles and create more complex thesis about transient flow behaviour inside of valve. Next task of this article is point out reader to way leads to optimal design with as small as possible operation troubles. Troubles can be caused by non-design operation or by wrong shape design of inner parts how is written below.

  7. Ground vibration test of the laminar flow control JStar airplane

    NASA Technical Reports Server (NTRS)

    Kehoe, M. W.; Cazier, F. W., Jr.; Ellison, J. F.

    1985-01-01

    A ground vibration test was conducted on a Lockheed JetStar airplane that had been modified for the purpose of conducting laminar flow control experiments. The test was performed prior to initial flight flutter tests. Both sine-dwell and single-point-random excitation methods were used. The data presented include frequency response functions and a comparison of mode frequencies and mode shapes from both methods.

  8. Making Large Suction Panels For Laminar-Flow Control

    NASA Technical Reports Server (NTRS)

    Maddalon, Dal V.

    1991-01-01

    Perforated titanium panels used to identify and resolve issues related to manufacture. Recently, relatively large suction panels with aerodynamically satisfactory surface perforations and with surface contours and smoothness characteristics necessary for Laminar-Flow Control (LFC) designed, fabricated, and tested. Requirements of production lines for commercial transport airplanes carefully considered in development of panels. Sizes of panels representative of what is used on wing of commercial transport airplane. Tests of perforated panels in transonic wind tunnel demonstrated aerodynamic stability at flight mach numbers.

  9. Temperature-gated thermal rectifier for active heat flow control.

    PubMed

    Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

    2014-08-13

    Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (<1%). To the best of our knowledge, this is the first demonstration of solid-state active-thermal devices with a large rectification in the Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.

  10. Controlling a Linear Process in Turbulent Channel Flow

    NASA Astrophysics Data System (ADS)

    Lim, Junwoo; Kim, John

    1999-11-01

    Recent studies have shown that controllers developed based on a linear system theory work surprisingly well in reducing the viscous drag in turbulent boundary layers, suggesting that the essential dynamics of near-wall turbulence may well be approximated by the linearized model. Of particular interest is the linear process due to the coupling term between the wall-normal velocity and wall-normal vorticity terms in the linearized Navier-Stokes (N-S) equations, which enhances non-normality of the linearized system. This linear process is investigated through numerical simulations of a turbulent channel flow. It is shown that the linear coupling term plays an important role in fully turbulent -- and hence, nonlinear -- flows. Near-wall turbulence is shown to decay in the absence of the linear coupling term. The fact that the coupling term plays an essential role in maintaining near-wall turbulence suggests that an effective control algorithm for the drag reduction in turbulent flows should be aimed at reducing the effect of the coupling term in the wall region. Designing a control algorithm that directly accounts for the coupling term in a cost to be minimized will be discussed.

  11. Optimal Fixed-Interval Integrated Guidance-Control Laws for Hit-to-Kill Missiles

    DTIC Science & Technology

    2003-08-01

    Presented at the 2003 AIAA Guidance, Navigation, and Control Conference, August 11-14 , Austin, TX. Paper No:AIAA-2003-5579 © Optimal Synthesis ...Sweriduk† E. J. Ohlmeyer‡ Optimal Synthesis Inc. Naval Surface Warfare Center 868 San Antonio Road Dahlgren, VA 22448-5100 Palo Alto, CA 94303-4622...interest in methods for integrated synthesis of missile guidance and control systems in recent literature1-9. These techniques have the potential to

  12. Electrically heated particulate filter with zoned exhaust flow control

    DOEpatents

    Gonze, Eugene V [Pinckney, MI

    2012-06-26

    A system includes a particulate matter (PM) filter that includes X zones. An electrical heater includes Y heater segments that are associated with respective ones of the X zones. The electrical heater is arranged upstream from and proximate with the PM filter. A valve assembly includes Z sections that are associated with respective ones of the X zones. A control module adjusts flow through each of the Z sections during regeneration of the PM filter via control of the valve assembly. X, Y and Z are integers.

  13. Improvement of transient stability using unified power flow controller

    SciTech Connect

    Mihalic, R.; Zunko, P.; Povh, D.

    1996-01-01

    The aim of the paper is to analyze the effect of an Unified Power Flow Controller (UPFC) on transient stability margin enhancement of a longitudinal system. To utilize the UPFC possibilities fully, the three controllable UPFC parameters were determined during the digital simulation process performed by the NETOMAC simulation program. The basis for determination of the suitable damping strategy and for determination of the optimal UPFC parameters is a mathematical model, which describes the interdependence between longitudinal transmission system parameters, operating conditions and UPFC parameters in the form of analytical equations. On the basis of the mathematical model, the theoretical UPFC limits were also detected, and their appearance explained.

  14. Dynamic control of aerodynamic forces on a moving platform using active flow control

    NASA Astrophysics Data System (ADS)

    Brzozowski, Daniel P.

    The unsteady interaction between trailing edge aerodynamic flow control and airfoil motion in pitch and plunge is investigated in wind tunnel experiments using a two degree-of-freedom traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the trailing edge of the airfoil using hybrid synthetic jet actuators. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and particle image velocimetry (PIV) measurements that are taken phase-locked to the commanded actuation waveform. The effect of the unsteady motion on the model-embedded flow control is assessed in both trajectory tracking and disturbance rejection maneuvers. The time-varying aerodynamic lift and pitching moment are estimated from a PIV wake survey using a reduced order model based on classical unsteady aerodynamic theory. These measurements suggest that the entire flow over the airfoil readjusts within 2--3 convective time scales, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.

  15. An Investigation of Turbulence Mechanisms in V/STOL Upwash Flow Fields.

    DTIC Science & Technology

    1987-03-01

    flow. The system we developed utilized two sets of cylindrical lenses to form a thin laser sheet with variable height and width. An Argon ion laser was...George Homfeld who built much of the apparatus and made sure everything worked. 6 ~65 𔃻! 5. REFERENCES 1. Kalemaris, S.G., and Cea , R.A., "Effects of...Effects of Ground Wall-Jet Characteristics on Fountain Upwash Flow Formation and Development," AIAA Paper #81-1294, AIAA 14th Fluid & Plasma Dyn Conf

  16. INVITED PAPER: Control of sudden releases in channel flow

    NASA Astrophysics Data System (ADS)

    Katopodes, Nikolaos D.

    2009-12-01

    We present a method for the detection and real-time control of chemical releases in channel flow. Sensor arrays capable of detecting a broad menu of chemical agents are required at strategic locations of the channel. The sensors detect the instantaneous, spatially distributed concentration of the chemical agent and transmit the associated information to a predictive control model. The model provides optimal operation scenarios for computer controlled bleed valves mounted on the channel walls and connected to a common manifold. Control and elimination of the chemical cloud are achieved by optimal blowing and suction of ambient fluid. Gradient information is obtained by use of adjoint equations, so optimization of the control actions is achieved with the highest possible efficiency. The control is optimized over a finite prediction horizon and instructions are sent to the valve manifold. Next, the sensor arrays detect all changes effected by the control and report them to the control model, which advances the process over the next control horizon. Non-reflective boundary conditions for the adjoint equations are derived by a characteristic analysis, which minimizes spurious information in the computation of sensitivities.

  17. Algorithms for automatic feedback control of aerodynamic flows

    NASA Astrophysics Data System (ADS)

    Palaniappan, Karthik

    This thesis focuses on deriving algorithmic frameworks for the control of Aerodynamic Phenomena. The application of one such control law to the control of Flutter is discussed in detail. Flutter is an aero-structural instability that arises due to the adverse transfer of energy between the airplane structure and the surrounding fluid. CFD is now a mature technology and can be used as a design tool in addition to being used as an analysis tool. This is the motivation for much of the research that takes place at the Aerospace Computing Lab at Stanford. Shape optimization involves finding the shape (2-d or 3-d) that optimizes a certain performance index. Clearly, any optimum shape will be optimum only at the design point. It has been found that the aerodynamic performance at neighboring operating points is a lot less optimal than the original shapes. What we need to do is to design and develop a feasible way of controlling the flow at any operating point such that the resulting performance is optimal. In designing control laws, our philosophy has been to develop an algorithmic framework that enables treating a broad class of control problems rather than design control laws for specific isolated cases. This ensures that once a framework is established, extensions to particular problems can be done with very little effort. The framework we develop is problem independent and controller independent. Moreover, it has been shown that this leads to control laws that are feedback based, hence robust.

  18. Photovoltaic Inverter Controllers Seeking AC Optimal Power Flow Solutions

    SciTech Connect

    Dall'Anese, Emiliano; Dhople, Sairaj V.; Giannakis, Georgios B.

    2016-07-01

    This paper considers future distribution networks featuring inverter-interfaced photovoltaic (PV) systems, and addresses the synthesis of feedback controllers that seek real- and reactive-power inverter setpoints corresponding to AC optimal power flow (OPF) solutions. The objective is to bridge the temporal gap between long-term system optimization and real-time inverter control, and enable seamless PV-owner participation without compromising system efficiency and stability. The design of the controllers is grounded on a dual ..epsilon..-subgradient method, while semidefinite programming relaxations are advocated to bypass the non-convexity of AC OPF formulations. Global convergence of inverter output powers is analytically established for diminishing stepsize rules for cases where: i) computational limits dictate asynchronous updates of the controller signals, and ii) inverter reference inputs may be updated at a faster rate than the power-output settling time.

  19. Proportional feedback control of flow over a hemisphere

    NASA Astrophysics Data System (ADS)

    Lee, Jungil; Yun, Jinhyuk; Son, Donggun

    2016-11-01

    In the present study, a proportional feedback control is applied to laminar flow over a hemisphere at Re = 300 to reduce its lift fluctuations. As a control input, blowing/suction is distributed on the surface of hemisphere before the separation, and its strength is linearly proportional to the transverse velocity at a sensing location in the centerline of the wake. To determine the optimal sensing location, we introduce a correlation function between the lift force and the time derivative of sensing velocity. The optimal proportional gains for the proportional control are obtained for the sensing locations considered. It is shown that the present control successfully attenuates the velocity fluctuations at the sensing location, resulting in the reduction of lift fluctuations of hemisphere. Supported by NRF program (2014R1A1A1002671).

  20. Digital feedwater and recirculation flow control for GPUN Oyster Creek

    SciTech Connect

    Burjorjee, D. ); Gan, B. )

    1992-01-01

    This paper describes the digital system for feedwater and recirculation control that GPU Nuclear will be installing at Oyster Creek during its next outage - expected circa December 1992. The replacement was motivated by considerations of reliability and obsolescence - the analog equipment was aging and reaching the end of its useful life. The new system uses Atomic Energy of Canada Ltd.'s software platform running on dual, redundant, industrial-grade 386 computers with opto-isolated field input/output (I/O) accessed through a parallel bus. The feedwater controller controls three main feed regulating valves, two low flow regulating valves, and two block valves. The recirculation controller drives the five scoop positioners of the hydraulic couplers. The system also drives contacts that lock up the actuators on detecting an open circuit in their current loops.

  1. Environmental controls on sap flow in a northern hardwood forest.

    PubMed

    Bovard, B D; Curtis, P S; Vogel, C S; Su, H-B; Schmid, H P

    2005-01-01

    Our objective was to gain a detailed understanding of how photosynthetically active radiation (PAR), vapor pressure deficit (D) and soil water interact to control transpiration in the dominant canopy species of a mixed hardwood forest in northern Lower Michigan. An improved understanding of how these environmental factors affect whole-tree water use in unmanaged ecosystems is necessary in assessing the consequences of climate change on the terrestrial water cycle. We used continuously heated sap flow sensors to measure transpiration in mature trees of four species during two successive drought events. The measurements were scaled to the stand level for comparison with eddy covariance estimates of ecosystem water flux (Fw). Photosynthetically active radiation and D together explained 82% of the daytime hourly variation in plot-level transpiration, and low soil water content generally resulted in increased stomatal sensitivity to increasing D. There were also species-specific responses to drought. Quercus rubra L. showed low water use during both dry and wet conditions, and during periods of high D. Among the study species, Acer rubrum L. showed the greatest degree of stomatal closure in response to low soil water availability. Moderate increases in stomatal sensitivity to D during dry periods were observed in Populus grandidentata Michx. and Betula papyrifera Marsh. Sap flow scaled to the plot level and Fw demonstrated similar temporal patterns of water loss suggesting that the mechanisms controlling sap flow of an individual tree also control ecosystem evapotranspiration. However, the absolute magnitude of scaled sap flow estimates was consistently lower than Fw. We conclude that species-specific responses to PAR, D and soil water content are key elements to understanding current and future water fluxes in this ecosystem.

  2. Experimental Investigation of Actuators for Flow Control in Inlet Ducts

    NASA Astrophysics Data System (ADS)

    Vaccaro, John; Amitay, Michael

    2009-11-01

    For military applications, inlet designs are constrained by low observability requirements, which call for the use of an S-duct inlet. The inlets purpose is to limit the line-of-sight to the compressor and decelerate the incoming flow while minimizing total pressure loss, distortion, and unsteadiness. In addition, in unmanned aerial vehicles, the inlet length can determine the overall size of the aircraft. For this reason, aggressive inlets can have a large impact on overall system efficiency. Experiments have been conducted which evaluate the effectiveness of different actuation systems for active flow control in an aggressive S-duct inlet, L/D = 1.5 (at flow conditions representative of flight conditions). Comparisons will be made between: steady and unsteady blowing from a single 2-D tangential slit, spanwise varying injection from a tangential slit, and spanwise varying injection of a hybrid actuator that has both a coanda type injector along with vortex generator jets to eliminate vorticity developed by secondary flow inherent to S-ducts. Evaluations criteria will include total pressure recovery, AIP distortion levels, and unsteady pressure fluctuations.

  3. Non-Markovian quantum feedback networks II: Controlled flows

    NASA Astrophysics Data System (ADS)

    Gough, John E.

    2017-06-01

    The concept of a controlled flow of a dynamical system, especially when the controlling process feeds information back about the system, is of central importance in control engineering. In this paper, we build on the ideas presented by Bouten and van Handel [Quantum Stochastics and Information: Statistics, Filtering and Control (World Scientific, 2008)] and develop a general theory of quantum feedback. We elucidate the relationship between the controlling processes, Z, and the measured processes, Y, and to this end we make a distinction between what we call the input picture and the output picture. We should note that the input-output relations for the noise fields have additional terms not present in the standard theory but that the relationship between the control processes and measured processes themselves is internally consistent—we do this for the two main cases of quadrature measurement and photon-counting measurement. The theory is general enough to include a modulating filter which post-processes the measurement readout Y before returning to the system. This opens up the prospect of applying very general engineering feedback control techniques to open quantum systems in a systematic manner, and we consider a number of specific modulating filter problems. Finally, we give a brief argument as to why most of the rules for making instantaneous feedback connections [J. Gough and M. R. James, Commun. Math. Phys. 287, 1109 (2009)] ought to apply for controlled dynamical networks as well.

  4. Optimal control of an asymptotic model of flow separation

    NASA Astrophysics Data System (ADS)

    Qadri, Ubaid; Schmid, Peter; LFC-UK Team

    2015-11-01

    In the presence of surface imperfections, the boundary layer developing over an aircraft wing can separate and reattach, leading to a small separation bubble. We are interested in developing a low-order model that can be used to control the onset of separation at high Reynolds numbers typical of aircraft flight. In contrast to previous studies, we use a high Reynolds number asymptotic description of the Navier-Stokes equations to describe the motion of motion of the fluid. We obtain a steady solution to the nonlinear triple-deck equations for the separated flow over a small bump at high Reynolds numbers. We derive for the first time the adjoint of the nonlinear triple-deck equations and use it to study optimal control of the separated flow. We calculate the sensitivity of the properties of the separation bubble to local base flow modifications and steady forcing. We assess the validity of using this simplified asymptotic model by comparing our results with those obtained using the full Navier-Stokes equations.

  5. Flow Control Analysis on the Hump Model with RANS Tools

    NASA Technical Reports Server (NTRS)

    Viken, Sally A.; Vatsa, Veer N.; Rumsey, Christopher L.; Carpenter, Mark H.

    2003-01-01

    A concerted effort is underway at NASA Langley Research Center to create a benchmark for Computational Fluid Dynamic (CFD) codes. both unstructured and structured, against a data set for the hump model with actuation. The hump model was tested in the NASA Langley 0.3-m Transonic Cryogenic Tunnel. The CFD codes used for the analyses are the FUN2D (Full Unstructured Navier-Stokes 2-Dimensional) code, the structured TLNS3D (Thin-Layer Navier-Stokes 3-Dimensional) code, and the structured CFL3D code, all developed at NASA Langley. The current investigation uses the time-accurate Reynolds-Averaged Navier-Stokes (RANS) approach to predict aerodynamic performance of the active flow control experimental database for the hump model. Two-dimensional computational results verified that steady blowing and suction and oscillatory suction/blowing can be used to significantly reduce the separated flow region on the model. Discrepancies do exist between the CFD results and experimental data in the region downstream of the slot with the largest differences in the oscillatory cases. Overall, the structured CFD codes exhibited similar behavior with each other for a wide range of control conditions, with the unstructured FUN2D code showing moderately different results in the separated flow region for the suction and oscillatory cases.

  6. Development Activities on an Advanced Propellant Flow Control Unit

    NASA Astrophysics Data System (ADS)

    Noci, G.; Siciliano, P.; Fallerini, L.; Kutufa, N.; Rivetti, A.; Galassi, C.; Bruschi, P.; Piotto, M.

    2004-10-01

    A new generation of propellant control equipment for electric propulsion systems is needed in order to improve performance and operating ranges, symplify h/w configuration, reduce mass and dimensions, eliminate mass flow ripple, reduce time response. In this frame, the development of key components, their assembly and experimental investigation/ validation is on-going at Alenia Spazio-Laben/Business Unit Proel Tecnologie ( Proel in the following ) in the frame of an ESA GSTP program. The new components shall support different EP technologies, future EP multi-tasking capability and wide operating ranges. This paper reports about the development effort, its achievements and perspectives. 1. ABBREVIATIONS AND ACRONYMS BOL Beginning of Life CMBR Ceramic multilayer bender ring CTA Constant Temperature Anemometry. DUT Device under test EOL End of Life EP Electric Propulsion GEO Geosyncrhonous Earth Orbit GFCU Gas Flow Control Unit GIT Gridded ion thruster HET Hall Effect Thrusters LEO Low Earth Orbit LPC Low pressure capillary MEOP Maximum Expected Operating Pressure MFS Mass Flow rate Sensor NSSK North-South Station Keeping Pred Reduced pressure Ptank Tank pressure RMT Radiofrequency Magnetic Thruster RMTA Radiofrequency Magnetic Thruster Assembly ROOV Regulation and On-Off Valve SoW Statement of Work SPT Stationary Plasma Thruster.

  7. Passive jet control of flow around a circular cylinder

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Li; Gao, Dong-Lai; Yuan, Wen-Yong; Li, Hui; Hu, Hui

    2015-11-01

    In the present study, a passive flow control method, which is featured by passive windward suction combined with leeward jet over a circular cylinder for drag reduction and dynamic wind loading suppression, was experimentally investigated to manipulate unsteady wake vortex shedding from a circular cylinder. Four perforated pipe designs with different numbers of suction/jet holes (i.e., from 2 to 24 suction/jet holes) were used to create flow communicating channels between the windward and leeward stagnation points of a cylindrical test model. The experimental study was performed in a wind tunnel at a Reynolds number of Re = 4.16 × 104 based on the cylinder diameter and oncoming airflow speed. In addition to measuring surface pressure distributions to determine the dynamic wind loads acting on the test model, a digital particle image velocimetry (PIV) system was also used to quantify the wake flow characteristics in order to assess the effectiveness of the passive jet control method with different perforated pipe designs, in comparison with a baseline case without passive jet control. It was found that the passive jet control method is very effective in manipulating the wake vortex shedding process from the circular cylinder. The perforated pipe designs with more suction/jet holes were found to be more effective in reducing drag and suppressing fluctuating amplitude of the dynamic wind loads acting on the test model. With 24 suction/jet holes evenly distributed over the cylindrical test model (i.e., the N13 design of the present study), the passive jet control method was found to be able to achieve up to 33.7 % in drag reduction and 90.6 % in fluctuating wind loading suppression, in comparison with the baseline case. The PIV measurement results revealed clearly that the passive jet control method would cause airflow jets into the cylinder wake and change the shedding modes of the wake vortex structures from the cylindrical test model. Because of the dynamic

  8. Snapshot of Active Flow Control Research at NASA Langley

    NASA Technical Reports Server (NTRS)

    Washburn, A. E.; Gorton, S. Althoff; Anders, S. G.

    2002-01-01

    NASA Langley is aggressively investigating the potential advantages of active flow control as opposed to more traditional aerodynamic techniques. Many of these techniques will be blended with advanced materials and structures to further enhance payoff. Therefore a multi-disciplinary approach to technology development is being attempted that includes researchers from the more historical disciplines of fluid mechanics. acoustics, material science, structural mechanics, and control theory. The overall goals of the topics presented are focused on advancing the state of knowledge and understanding of controllable fundamental mechanisms in fluids rather than on specific engineering problems. An organizational view of current research activities at NASA Langley in active flow control as supported by several programs such as the Morphing Project under Breakthrough Vehicle Technologies Program (BVT). the Ultra-Efficient Engine Technology Program (UEET), and the 21st Century Aircraft Technology Program (TCAT) is presented. On-center research as well as NASA Langley funded contracts and grants are discussed at a relatively high level. The products of this research, as part of the fundamental NASA R and D (research and development) program. will be demonstrated as either bench-top experiments, wind-tunnel investigations, or in flight tests. Later they will be transferred to more applied research programs within NASA, DOD (Department of Defense), and U.S. industry.

  9. Synthetic Jets Flow Control on a vertical stabilizer

    NASA Astrophysics Data System (ADS)

    Rathay, Nicholas; Boucher, Matthew; Amitay, Michael

    2011-11-01

    The vertical stabilizer on most commercial transport aircraft is much larger than required for stability and control. The tail is significantly oversized in order to maintain controllability in the event of asymmetric engine failure and meet flying qualities requirements related to dynamic motion. Using aerodynamic flow control techniques, it may be possible to reduce the size of the tail while maintaining similar control authority during inclement flight conditions. Reducing the size of the tail decreases the weight and the drag of the airplane, which results in considerable savings in fuel costs. In this work, it is shown that synthetic jet (zero-net-mass-flux) actuators are capable of reattaching the separated flow on the rudder and augmenting the performance of the stabilizer. Experiments were conducted in an open-return wind tunnel on a 1/25th scale model of a vertical stabilizer and a partial fuselage section. The surface pressure, aerodynamic loads and data acquired with a Stereo PIV system were used to investigate the effectiveness of this technology as well as provide a more detailed analysis of the flowfield and showed that the synthetic jets are capable of augmenting the side-force by up to 20%.

  10. Optimal Control of Mixing in Stokes Fluid Flows

    NASA Astrophysics Data System (ADS)

    Mathew, George; Mezic, Igor; Grivopoulos, Symeon; Vaidya, Umesh; Petzold, Linda

    2006-11-01

    Motivated by the problem of microfluidic mixing, the problem of optimal control of advective mixing in Stokes fluid flows is considered. The velocity field is assumed to be induced by a finite set of spatially distributed force fields that can be modulated arbitrarily with time and a passive material is advected by the flow. To quantify the degree of mixedness of a density field, we use a Sobolev space norm of negative index. We pose a finite-time optimal control problem where we aim to achieve the best mixing for a fixed value of the action (time integral of the kinetic energy of the fluid body) per unit mass. We derive the first order necessary conditions for optimality that can be expressed as a two point boundary value problem and we discuss some elementary properties that the optimal controls need to satisfy. A conjugate gradient descent method is used to solve the optimal control problem and we present numerical results for two problems involving arrays of vortices. A comparison of the mixing performance shows that optimal aperiodic inputs can do better than periodic inputs.

  11. Feedback control of flow alignment in sheared liquid crystals.

    PubMed

    Strehober, David A; Schöll, Eckehard; Klapp, Sabine H L

    2013-12-01

    Based on a continuum theory, we investigate the manipulation of the nonequilibrium behavior of a sheared liquid crystal via closed-loop feedback control. Our goal is to stabilize a specific dynamical state, that is, the stationary "flow alignment," under conditions where the uncontrolled system displays oscillatory director dynamics with in-plane symmetry. To this end we employ time-delayed feedback control (TDFC), where the equation of motion for the ith component q(i)(t) of the order parameter tensor is supplemented by a control term involving the difference q(i)(t)-q(i)(t-τ). In this diagonal scheme, τ is the delay time. We demonstrate that the TDFC method successfully stabilizes flow alignment for suitable values of the control strength K and τ; these values are determined by solving an exact eigenvalue equation. Moreover, our results show that only small values of K are needed when the system is sheared from an isotropic equilibrium state, contrary to the case where the equilibrium state is nematic.

  12. Optimization and Control of Acoustic Liner Impedance with Bias Flow

    NASA Technical Reports Server (NTRS)

    Wood, Houston; Follet, Jesse

    2000-01-01

    Because communities are impacted by steady increases in aircraft traffic, aircraft noise continues to be a growing problem for the growth of commercial aviation. Research has focused on improving the design of specific high noise source areas of aircraft and on noise control measures to alleviate noise radiated from aircraft to the surrounding environment. Engine duct liners have long been a principal means of attenuating engine noise. The ability to control in-situ the acoustic impedance of a liner would provide a valuable tool to improve the performance of liners. The acoustic impedance of a liner is directly related to the sound absorption qualities of that liner. Increased attenuation rates, the ability to change liner acoustic impedance to match various operating conditions, or the ability to tune a liner to more precisely match design impedance represent some ways that in-situ impedance control could be useful. With this in mind, the research to be investigated will focus on improvements in the ability to control liner impedance using a mean flow through the liner which is referred to as bias flow.

  13. Flow controls on lowland river macrophytes: a review.

    PubMed

    Franklin, Paul; Dunbar, Michael; Whitehead, Paul

    2008-08-01

    We review the current status of knowledge regarding the role that flow parameters play in controlling the macrophyte communities of temperate lowland rivers. We consider both direct and indirect effects and the interaction with other factors known to control macrophyte communities. Knowledge gaps are identified and implications for the management of river systems considered. The main factors and processes controlling the status of macrophytes in lowland rivers are velocity (hence also discharge), light, substrate, competition, nutrient status and river management practices. We suggest that whilst the characteristics of any particular macrophyte community reflect the integral effects of a combination of the factors, fundamental importance can be attributed to the role of discharge and velocity in controlling instream macrophyte colonisation, establishment and persistence. Velocity and discharge also appear to control the relative influence of some of the other controlling factors. Despite the apparent importance of velocity in determining the status of macrophyte communities in lowland rivers, relatively little is understood about the nature of the processes controlling this relationship. Quantitative knowledge is particularly lacking. Consequently, the ability to predict macrophyte abundance and distribution in rivers is still limited. This is further complicated by the likely existence of feedback effects between the growth of macrophytes and velocity. Demand for water resources increases the pressure on lowland aquatic ecosystems. Despite growing recognition of the need to allocate water for the needs of instream biota, the inability to assess the flow requirements of macrophyte communities limits the scope to achieve this. This increases the likelihood of overexploitation of the water resource as other users, whose demands are quantifiable, are prioritised.

  14. Computational Analysis of Cryogenic Flow Through a Control Valve

    NASA Technical Reports Server (NTRS)

    Danes, Russell; Woods, Jody; Sulyma, Peter

    2003-01-01

    The initial efforts to develop the capability to model valves used in rocket engine component testing at Stennis Space Center are documented. An axisymmetric model of a control valve with LN2 as the working fluid was developed. The goal was to predict the effect of change in the plug/sear region of the valve prior to testing. The valve flow coefficient was predicted for a range of plug positions. Verification of the calculations was carried out to quantify the uncertainty in the numerical answer. The modeled results compared well qualitatively to experimental trends. Additionally, insights into the flow processes in the valve were obtained. Benefits from the verification process included the ability to use coarser grids and insight into ways to reduce computational time by using double precision accuracy and non-integer grid ratios. Future valve modeling activities will include shape optimization of the valve/seat region and dynamic grid modeling.

  15. Unsteady flow model for circulation-control airfoils

    NASA Technical Reports Server (NTRS)

    Rao, B. M.

    1979-01-01

    An analysis and a numerical lifting surface method are developed for predicting the unsteady airloads on two-dimensional circulation control airfoils in incompressible flow. The analysis and the computer program are validated by correlating the computed unsteady airloads with test data and also with other theoretical solutions. Additionally, a mathematical model for predicting the bending-torsion flutter of a two-dimensional airfoil (a reference section of a wing or rotor blade) and a computer program using an iterative scheme are developed. The flutter program has a provision for using the CC airfoil airloads program or the Theodorsen hard flap solution to compute the unsteady lift and moment used in the flutter equations. The adopted mathematical model and the iterative scheme are used to perform a flutter analysis of a typical CC rotor blade reference section. The program seems to work well within the basic assumption of the incompressible flow.

  16. Electromagnetic valve for controlling the flow of molten, magnetic material

    DOEpatents

    Richter, Tomas

    1998-01-01

    An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell.

  17. Electromagnetic valve for controlling the flow of molten, magnetic material

    DOEpatents

    Richter, T.

    1998-06-16

    An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell. 5 figs.

  18. Control algorithm for multiscale flow simulations of water

    NASA Astrophysics Data System (ADS)

    Kotsalis, Evangelos M.; Walther, Jens H.; Kaxiras, Efthimios; Koumoutsakos, Petros

    2009-04-01

    We present a multiscale algorithm to couple atomistic water models with continuum incompressible flow simulations via a Schwarz domain decomposition approach. The coupling introduces an inhomogeneity in the description of the atomistic domain and prevents the use of periodic boundary conditions. The use of a mass conserving specular wall results in turn to spurious oscillations in the density profile of the atomistic description of water. These oscillations can be eliminated by using an external boundary force that effectively accounts for the virial component of the pressure. In this Rapid Communication, we extend a control algorithm, previously introduced for monatomic molecules, to the case of atomistic water and demonstrate the effectiveness of this approach. The proposed computational method is validated for the cases of equilibrium and Couette flow of water.

  19. Control algorithm for multiscale flow simulations of water.

    PubMed

    Kotsalis, Evangelos M; Walther, Jens H; Kaxiras, Efthimios; Koumoutsakos, Petros

    2009-04-01

    We present a multiscale algorithm to couple atomistic water models with continuum incompressible flow simulations via a Schwarz domain decomposition approach. The coupling introduces an inhomogeneity in the description of the atomistic domain and prevents the use of periodic boundary conditions. The use of a mass conserving specular wall results in turn to spurious oscillations in the density profile of the atomistic description of water. These oscillations can be eliminated by using an external boundary force that effectively accounts for the virial component of the pressure. In this Rapid Communication, we extend a control algorithm, previously introduced for monatomic molecules, to the case of atomistic water and demonstrate the effectiveness of this approach. The proposed computational method is validated for the cases of equilibrium and Couette flow of water.

  20. Reduced order modeling, nonlinear analysis and control methods for flow control problems

    NASA Astrophysics Data System (ADS)

    Kasnakoglu, Cosku

    Flow control refers to the ability to manipulate fluid flow so as to achieve a desired change in its behavior, which offers many potential technological benefits, such as reducing fuel costs for vehicles and improving effectiveness of industrial processes. An interesting case of flow control is cavity flow control, which has been the motivation of this study: When air flow passes over a shallow cavity a strong resonance is produced by a natural feedback mechanism, scattering acoustic waves that propagate upstream and reach the shear layer, and developing flow structures. These cause many practical problems including damage and fatigue in landing gears and weapons bays in aircrafts. Presently there is a lack of sufficient mathematical analysis and control design tools for flow control problems. This includes mathematical models that are amenable to control design. Recently reduced-order modeling techniques, such as those based on proper orthogonal decomposition (POD) and Galerkin projection (GP), have come to interest. However, a main issue with these models is that the effect of boundary conditions, which is where the control input is, gets embedded into system coefficients. This results in a form quite different from what one deals with in standard control systems framework, which is a set of ordinary differential equations (ODE) where the input appears as an explicit term. Another issue with the standard POD/GP models is that they do not yield to systems that have any apparent structure in their coefficients. This leaves one with little choice other than to neglect the nonlinearities of the models and employ standard linear control theory based designs. The research presented in this thesis makes an effort at closing the gaps mentioned above by (1) presenting a reduced-order modeling method utilizing a novel technique for input separation on POD/GP models, (2) introducing a technique based on averaging theory and center manifold theory so as to reveal certain