WorldWideScience

Sample records for griswald flow control

  1. Flow Control

    Science.gov (United States)

    2013-04-08

    an aerodynamic design. A few examples of this type of flow control are winglets , fins, or dimples on a golf ball. The other type of flow control is...represented the density states of the flow field. The first parameter was the composition of the regression vector, Θ j. This regression vector was...Development Using Proper Orthogonal De- composition and Volterra Theory. In AIAA 2003-1922, 2003. A. Mani, M. Wang, and P. Moin. Resolution requirements

  2. Dynamic power flow controllers

    Science.gov (United States)

    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.

  3. Distributed Power Flow Controller

    NARCIS (Netherlands)

    Yuan, Z.

    2010-01-01

    In modern power systems, there is a great demand to control the power flow actively. Power flow controlling devices (PFCDs) are required for such purpose, because the power flow over the lines is the nature result of the impedance of each line. Due to the control capabilities of different types of P

  4. Distributed Power Flow Controller

    NARCIS (Netherlands)

    Yuan, Z.

    2010-01-01

    In modern power systems, there is a great demand to control the power flow actively. Power flow controlling devices (PFCDs) are required for such purpose, because the power flow over the lines is the nature result of the impedance of each line. Due to the control capabilities of different types of P

  5. Control of Unstable Flows

    Institute of Scientific and Technical Information of China (English)

    刘曾荣; 茅坚民

    2003-01-01

    Without introducing a discrete model, unstable continuous flows in a neighbourhood of an unstable stationary point can be stabilized. The linear part of the vector field of disturbing the flow can be managed to become the state variable multiplied by a negative constant. The nonlinear part of the vector field keeps to be unchanged,therefore flows far away from the stationary point are almost unaffected by the disturbance. The control method is easy to be used, even for practical problems for which a priori analytical knowledge of system dynamics is unavailable.

  6. Power flow controller

    NARCIS (Netherlands)

    Ferreira, J.A.; Yuan, Z.; De Haan, S.W.H.

    2008-01-01

    The invention relates to a power flow controller, comprising at least one first converter coupled with a power transmission line, and at least one second converter coupled with a power source, wherein said power source operates at a predeter-mined first frequency and connects to the power transmissi

  7. Shaped Recess Flow Control

    Science.gov (United States)

    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.

  8. Flow Control Technology

    Science.gov (United States)

    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

  9. Controllability of flow turbulence.

    Science.gov (United States)

    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.

  10. Control structures for flow process

    Directory of Open Access Journals (Sweden)

    Mircea Dulău

    2011-12-01

    Full Text Available In the industrial domain, a large number of applications is covered by slow processes, including the flow, the pressure, the temperature and the level control. Each control system must be treated in steady and dynamic states and from the point of view of the possible technical solutions. Based on mathematical models of the processes and design calculations, PC programs allow simulation and the determination of the control system performances.The paper presents a part of an industrial process with classical control loops of flow and temperature. The mathematical model of the flow control process was deducted, the control structure, based on experimental criterions, was designed and the version witch ensure the imposed performances was chosen. Using Matlab, the robustness performances were studied.

  11. Flow Interactions and Control

    Science.gov (United States)

    2013-03-04

    Simulation Spectra inside nozzle shows similar behavior to spectra along upstream shear layer Controlled transverse jet mixing requires...Distribution 3D physics-based morphology analysis of flexible flapping wings Wing gaits analysis using SVD (Singular Value

  12. Optimal Power Flow Control by Rotary Power Flow Controller

    Directory of Open Access Journals (Sweden)

    KAZEMI, A.

    2011-05-01

    Full Text Available This paper presents a new power flow model for rotary power flow controller (RPFC. RPFC injects a series voltage into the transmission line and provides series compensation and phase shifting simultaneously. Therefore, it is able to control the transmission line impedance and the active power flow through it. An RPFC is composed mainly of two rotary phase shifting transformers (RPST and two conventional (series and shunt transformers. Structurally, an RPST consists of two windings (stator and rotor windings. The rotor windings of the two RPSTs are connected in parallel and their stator windings are in series. The injected voltage is proportional to the vector sum of the stator voltages and so its amplitude and angle are affected by the rotor position of the two RPSTs. This paper, describes the steady state operation and single-phase equivalent circuit of the RPFC. Also in this paper, a new power flow model, based on power injection model of flexible ac transmission system (FACTS controllers, suitable for the power flow analysis is introduced. Proposed model is used to solve optimal power flow (OPF problem in IEEE standard test systems incorporating RPFC and the optimal settings and location of the RPFC is determined.

  13. Active Flow Control

    Science.gov (United States)

    FFOWCS WILLIAMS, J. E.

    2001-01-01

    This paper considers the two-dimensional problem of a plane vortex sheet disturbed by an impulsive line source. A previous incorrect treatment of this problem is examined in detail. Instabilities of the vortex sheet are triggered by the source and grow exponentially in space and time. The Green function is constructed for the problem and it is shown that a point source properly positioned and delayed will induce a field that cancels the unstable growing modes. The resulting displacement of the vortex sheet is expressed in simple terms. The instabilities are checked by the anti-source which combines with the field of the primary source into a vortex sheet response which decays with time at large time. This paper is a contribution to the study of active control of shear layer instabilities, the main contribution being to clear up a previous paper with peculiar results that are, in fact, wrong.

  14. Subcubic Control Flow Analysis Algorithms

    DEFF Research Database (Denmark)

    Midtgaard, Jan; Van Horn, David

    We give the first direct subcubic algorithm for performing control flow analysis of higher-order functional programs. Despite the long held belief that inclusion-based flow analysis could not surpass the ``cubic bottleneck, '' we apply known set compression techniques to obtain an algorithm...... that runs in time O(n^3/log n) on a unit cost random-access memory model machine. Moreover, we refine the initial flow analysis into two more precise analyses incorporating notions of reachability. We give subcubic algorithms for these more precise analyses and relate them to an existing analysis from...

  15. Multiverse data-flow control.

    Science.gov (United States)

    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.

  16. Unsteady flow about a circulation control airfoil

    Institute of Scientific and Technical Information of China (English)

    刘晶昌; 孙茂; 吴礼义

    1996-01-01

    The unsteady flow around a circulation control (CC) airfoil was investigated with Navier-Stokes method,which includes the flow around CC airfoil with pulsating jet,the flow around oscillating CC airfoil,and the flow around oscillating CC airfoil with pulsating jet.Dynamic properties of the flow and the aerodynamic forces were rewaled.

  17. VOST Flow-Control Valve Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A cryogenic flow-control valve based on Venturi-Offset Technology (VOST) will be designed and modeled. VOST provides precise linear flow control within a...

  18. Controlling Flow Turbulence Using Local Pinning Feedback

    Institute of Scientific and Technical Information of China (English)

    TANG Guo-Ning; HU Gang

    2006-01-01

    Flow turbulence control in two-dimensional Navier-Stokes equation is considered.By applying local pinning control only to a sjngle component of flow velocity field,the flow turbulence can be controlled to desirable targets.It is found that with certain number of controllers there exist an optimal control strength at which control error takes minimum value,and larger and smaller control strengths give worse control efficiency.The phvsical mechanism underlying these strange control results is analysed based on the interactions between different types of modes.

  19. Backstepping feedback control of open channel flow

    OpenAIRE

    Huo, Mandy; Malek, Sami

    2014-01-01

    We derive a feedback control law for the control of the downstream flow in a 1-D open channel by manipulating the water flow at an upstream location. We use backstepping for controller design and Lyapunov techniques for stability analysis. Finally, the controller is verified with simulations.

  20. Power flow control schemes for series-connected FACTS controllers

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Yang; Kazerani, Mehrdad [University of Waterloo, Department of Electrical & amp; Computer Engineering, Waterloo, Ont. (Canada N2L 3G1)

    2006-06-15

    Unified power flow controller (UPFC) and interline power flow controller (IPFC) are FACTS devices that can control the power flow in transmission lines by injecting active and reactive voltage components in series with the lines, using power converter modules, based on an externally regulated dc-link voltage. One key issue, in this application, is to find a relationship between the injected voltage and the resulting power flow in the line. In this paper, this relationship is derived analytically, and used to design two power flow control schemes. The proposed control schemes are applicable to any series-connected FACTS controller with the capability of producing a controllable voltage. In this paper, the proposed power flow control schemes are applied to a voltage-sourced converter-based IPFC, and the resulting control performances are examined using PSCAD/EMTDC simulation package. The simulation results show the effectiveness of the proposed power flow control schemes. (author)

  1. Power flow control using quadrature boosters

    Science.gov (United States)

    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. Instruction Scheduling Across Control Flow

    Directory of Open Access Journals (Sweden)

    Martin Charles Golumbic

    1993-01-01

    Full Text Available Instruction scheduling algorithms are used in compilers to reduce run-time delays for the compiled code by the reordering or transformation of program statements, usually at the intermediate language or assembly code level. Considerable research has been carried out on scheduling code within the scope of basic blocks, i.e., straight line sections of code, and very effective basic block schedulers are now included in most modern compilers and especially for pipeline processors. In previous work Golumbic and Rainis: IBM J. Res. Dev., Vol. 34, pp.93–97, 1990, we presented code replication techniques for scheduling beyond the scope of basic blocks that provide reasonable improvements of running time of the compiled code, but which still leaves room for further improvement. In this article we present a new method for scheduling beyond basic blocks called SHACOOF. This new technique takes advantage of a conventional, high quality basic block scheduler by first suppressing selected subsequences of instructions and then scheduling the modified sequence of instructions using the basic block scheduler. A candidate subsequence for suppression can be found by identifying a region of a program control flow graph, called an S-region, which has a unique entry and a unique exit and meets predetermined criteria. This enables scheduling of a sequence of instructions beyond basic block boundaries, with only minimal changes to an existing compiler, by identifying beneficial opportunities to cover delays that would otherwise have been beyond its scope.

  3. Development report, mass flow controller PN 5716068

    Science.gov (United States)

    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. Local Control of Blood Flow

    Science.gov (United States)

    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…

  5. Plasma Control of Turbine Secondary Flows Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose Phase I and II efforts that will focus on turbomachinery flow control. Specifically, the present work will investigate active control in a high speed...

  6. Modular Control Flow Analysis for Libraries

    DEFF Research Database (Denmark)

    Probst, Christian W.

    2002-01-01

    One problem in analyzing object oriented languages is that the exact control flow graph is not known statically due to dynamic dispatching. However, this is needed in order to apply the large class of known interprocedural analysis. Control Flow Analysis in the object oriented setting aims at det...... at determining run-time types of variables, thus allowing to possibly targeted method implementations. We present a flow sensitive analysis that allows separate handling of libraries and thereby efficient analysis of whole programs....

  7. Flow Control Over Sharp-Edged Wings

    Science.gov (United States)

    2007-07-01

    Sharp Leading Edge," Paper No. AIAA-2001-0121. 12Washburn, A. E., and Amitay, M., "Active Flow Control on the Stingray UAV: Physical Mechanisms," 4 2...A. E., and Amitay, M., "Active Flow Control on the Stingray UAV: Physical Mechanisms," 42 Aerospace Sciences Meeting & Exhibit," Paper No. AIAA-2004

  8. Flow Control in a Compact Inlet

    Science.gov (United States)

    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

  9. Power flow control using distributed saturable reactors

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Local flow control for active building facades

    Science.gov (United States)

    Kaligotla, Srikar; Chen, Wayne; Glauser, Mark

    2010-11-01

    Existing building facade designs are for a passive and an impermeable shell to prevent migration of outdoor air into the building and to control heat transfers between the exterior environment and the building interior. An active facade that can respond in real time to changing environmental conditions like wind speed and direction, pollutant load, temperature, humidity and light can lower energy use and maximize occupant comfort. With an increased awareness of cost and environmental effects of energy use, cross or natural ventilation has become an attractive method to lower energy use. Separated flow regions around such buildings are undesirable due to high concentration of pollutants, especially if the vents or dynamic windows for cross ventilation are situated in these regions. Outside pollutant load redistribution through vents can be regulated via flow separation control to minimize transport of pollutants into the building. Flow separation has been substantially reduced with the application of intelligent flow control tools developed at Syracuse University for flow around "silo" (turret) like structures. Similar flow control models can be introduced into buildings with cross ventilation for local external flow separation control. Initial experiments will be performed for turbulent flow over a rectangular block (scaled to be a mid-rise building) that has been configured with dynamic vents and unsteady suction actuators in a wind tunnel at various wind speeds.

  11. Supersonic Plasma Flow Control Experiments

    Science.gov (United States)

    2005-12-01

    to liquid metals , for example, the conductivities of typical plasma and electrolyte flows are relatively low. Ref. 14 cites the conductivity of...heating is the dominant effect. 15. SUBJECT TERMS Supersonic, plasma , MHD , boundary-layer 16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE...horns in operation on Mach 5 wind tunnel with a plasma discharge. 31 Figure 17 Front view of a 100 mA DC discharge generated with upstream pointing

  12. Specification and Construction of Control Flow Semantics

    OpenAIRE

    Smelik, R.; Rensink, A.; Kastenberg, H.; Grundy, J.; Howse, J.

    2006-01-01

    In this paper we propose a visual language CFSL for specifying control flow semantics of programming languages. We also present a translation from CFSL to graph production systems (GPS) for flow graph construction; that is, any CFSL specification, say for a language L, gives rise to a GPS that constructs from any L-program (represented as an abstract syntax graph) the corresponding flow graph. The specification language is rich enough to capture complex language constructs, including all of J...

  13. TFRC—IVS Flow Control Algorithm

    Institute of Scientific and Technical Information of China (English)

    HEKaijian; LINYaping; YANGAng

    2003-01-01

    This paper investigates the TCP (Trans-mission Control Protocol) friendliness of multicast video-conferencing systems. Through the analysis and simulation experiments it is shown that the slow response to network state changes and the fixed rate adjustment process lead to TCP unfriendliness in the bandwidth sharing. Therefore,this paper proposes a new TCP friendly flow control al-gorithm called TFRC-IVS flow control algorithm for the current best-effort Internet. TFRC-IVS (TCP-Friendly Rate Control--INRIA Videoconferencing System) algo-rithm utilizes TCP friendly control function derived from complex TCP model to calculate TCP friendly sending rate.Simulation results show that TFRC-IVS flow control algorithm improves the smoothness of transmission rates and converges quickly to the stable sending rate. In addi-tion, the TCP friendly control function in TFRC-IVS flow control algorithm ensures the TCP friendliness of video flows and fair bandwidth allocation with TCP flows, which the traditional static rate adjustment algorithm lacks.

  14. Flow Control in a Transonic Diffuser

    Science.gov (United States)

    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.

  15. Electroosmotically controllable multi-flow microreactor

    NARCIS (Netherlands)

    Kohlheyer, D.; Besselink, G.A.J.; Lammertink, Rob G.H.; Schlautmann, Stefan; Unnikrishnan, S.; Schasfoort, Richardus B.M.

    2005-01-01

    An adjustable diffusion-based microfluidic reactor is presented here, which is based on electro-osmotic guiding of reagent samples. The device consists of a laminar flow chamber with two separate reagent inlets. The position and the width of the two sample streams in the flow chamber can be controll

  16. Traffic Flow Control In Automated Highway Systems

    OpenAIRE

    Alvarez, Luis; Horowitz, Roberto

    1997-01-01

    This report studies the problem of traffic control in the Automated Highway System (AHS) hierarchical architecture of the California PATH program. A link layer controller for the PATH AHS architecture is presented. It is shown that the proposed control laws stabilize the vehicular density and flow around predetermined profiles.

  17. Planning to Plan-Integrating Control Flow

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In many planning situations, computation itself becomes a resource to be planned and scheduled. We model such computational resources as conventional resources which are used by control-flow actions, e.g., to direct the planning process. Control-flow actions and conventional actions are planned/scheduled in an integrated way and can interact with each other. Control-flow actions are then executed by the planning engine itself. The approach is illustrated by examples, e.g., for hierarchical planning, in which tasks that are temporally still far away impose only rough constraints on the current schedule, and control-flow tasks ensure that these tasks are refined as they approach the current time. Using the same mechanism, anytime algorithms can change appropriate search methods or parameters over time, and problems like scheduling critical time-outs for garbage collection can be made part of the planning itself.

  18. VOST Flow-Control Valve Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Two cryogenic flow-control valves of diameters 1/2" and 2" will be built and tested. Based on cryogenically-proven Venturi Off-Set Technology (VOST) they have no...

  19. A Lyapunov theory based UPFC controller for power flow control

    Energy Technology Data Exchange (ETDEWEB)

    Zangeneh, Ali; Kazemi, Ahad; Hajatipour, Majid; Jadid, Shahram [Center of Excellence for Power Systems Automation and Operation, Iran University of Science and Technology, Tehran (Iran)

    2009-09-15

    Unified power flow controller (UPFC) is the most comprehensive multivariable device among the FACTS controllers. Capability of power flow control is the most important responsibility of UPFC. According to high importance of power flow control in transmission lines, the proper controller should be robust against uncertainty and disturbance and also have suitable settling time. For this purpose, a new controller is designed based on the Lyapunov theory and its stability is also evaluated. The Main goal of this paper is to design a controller which enables a power system to track reference signals precisely and to be robust in the presence of uncertainty of system parameters and disturbances. The performance of the proposed controller is simulated on a two bus test system and compared with a conventional PI controller. The simulation results show the power and accuracy of the proposed controller. (author)

  20. Cavity flow control using a rod in cross flow

    Science.gov (United States)

    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

  1. Micro-Ramps for Hypersonic Flow Control

    Directory of Open Access Journals (Sweden)

    Konstantinos Kontis

    2012-04-01

    Full Text Available Shock/boundary layer interaction (SBLI is an undesirable phenomenon, occurring in high-speed propulsion systems. The conventional method to manipulate and control SBLI is using a bleed system that involves the removal of a certain amount of mass of the inlet flow to control boundary layer separation. However, the system requires a larger nacelle to compensate the mass loss, larger nacelles contribute to additional weight and drag and reduce the overall performance. This study investigates a novel type of flow control device called micro-ramps, a part of the micro vortex generators (VGs family that intends to replace the bleed technique. Micro-ramps produce pairs of counter-rotating streamwise vortices, which help to suppress SBLI and reduce the chances of flow separation. Experiments were done at Mach 5 with two micro-ramp models of different sizes. Schlieren photography, surface flow visualization and infrared thermography were used in this investigation. The results revealed the detailed flow characteristics of the micro-ramp, such as the primary and secondary vortices. This helps us to understand the overall flow physics of micro-ramps in hypersonic flow and their application for SBLI control.

  2. Environmental Control in Flow Bioreactors

    Directory of Open Access Journals (Sweden)

    Serena Giusti

    2017-04-01

    Full Text Available The realization of physiologically-relevant advanced in vitro models is not just related to the reproduction of a three-dimensional multicellular architecture, but also to the maintenance of a cell culture environment in which parameters, such as temperature, pH, and hydrostatic pressure are finely controlled. Tunable and reproducible culture conditions are crucial for the study of environment-sensitive cells, and can also be used for mimicking pathophysiological conditions related with alterations of temperature, pressure and pH. Here, we present the SUITE (Supervising Unit for In Vitro Testing system, a platform able to monitor and adjust local environmental variables in dynamic cell culture experiments. The physical core of the control system is a mixing chamber, which can be connected to different bioreactors and acts as a media reservoir equipped with a pH meter and pressure sensors. The chamber is heated by external resistive elements and the temperature is controlled using a thermistor. A purpose-built electronic control unit gathers all data from the sensors and controls the pH and hydrostatic pressure by regulating air and CO2 overpressure and flux. The system’s modularity and the possibility of imposing different pressure conditions were used to implement a model of portal hypertension with both endothelial and hepatic cells. The results show that the SUITE platform is able to control and maintain cell culture parameters at fixed values that represent either physiological or pathological conditions. Thus, it represents a fundamental tool for the design of biomimetic in vitro models, with applications in disease modelling or toxicity testing.

  3. Monitoring And Controlling Hydroponic Flow

    Science.gov (United States)

    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.

  4. Control of fully turbulent pipe flow

    Science.gov (United States)

    Kuehnen, Jakob; Hof, Bjoern

    2013-11-01

    We present a novel, very simple passive control technique, where a local modification of the flow profile by means of a stationary obstacle leads to full relaminarisation downstream. Relaminarisation is achieved about 50 diameters downstream of the control point. Since, in a smooth straight pipe, the flow remains laminar from that position significant reduction in skin friction can be accomplished. High-speed stereoscopic particle image velocimetry (S-PIV) has been used to investigate and capture the development of the transitional flow downstream the obstacle. We will present S-PIV measurements as well as pressure drop measurements and videos of the development of the flow during relaminarisation. The guiding fundamental principle behind our approach to control the velocity profile will be explained and discussed.

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

    Science.gov (United States)

    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%.

  6. Innovative Flow Control Concepts for Drag Reduction

    Science.gov (United States)

    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

  7. Linear control of oscillator and amplifier flows*

    Science.gov (United States)

    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.

  8. Declarative flow control for distributed instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Coordinated Control of Cross-Flow Turbines

    Science.gov (United States)

    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.

  10. Fuel cell with internal flow control

    Science.gov (United States)

    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.

  11. Control Flow Analysis for BioAmbients

    DEFF Research Database (Denmark)

    Nielson, Flemming; Nielson, Hanne Riis; Priami, C.

    2007-01-01

    This paper presents a static analysis for investigating properties of biological systems specified in BioAmbients. We exploit the control flow analysis to decode the bindings of variables induced by communications and to build a relation of the ambients that can interact with each other. We...

  12. Closed Loop Control and Turbulent Flows

    Science.gov (United States)

    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

  13. Control of microorganisms in flowing nutrient solutions.

    Science.gov (United States)

    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. Core flow control system for field applications; Sistema de controle de core-flow

    Energy Technology Data Exchange (ETDEWEB)

    Granzotto, Desiree G.; Adachi, Vanessa Y.; Bannwart, Antonio C.; Moura, Luiz F.M. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil); Sassim, Natache S.D.A. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Centro de Estudo do Petroleo (CEPETRO); Carvalho, Carlos H.M. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The significant heavy oil reserves worldwide and the presently high crude oil prices make it essential the development of technologies for heavy oil production and transportation. Heavy oils, with their inherent features of high viscosity (100- 10,000 cP) and density (below 20 deg API) require specific techniques to make it viable their flow in pipes at high flow rates. One of the simplest methods, which do not require use of heat or diluents, is provided by oil-water annular flow (core-flow). Among the still unsolved issues regarding core-flow is the two-phase flow control in order to avoid abrupt increases in the pressure drop due to the possible occurrence of bad water-lubricated points, and thus obtain a safe operation of the line at the lowest possible water-oil ratio. This work presents results of core flow tests which allow designing a control system for the inlet pressure of the line, by actuating on the water flow rate at a fixed oil flow rate. With the circuit model and the specified controller, simulations can be done to assess its performance. The experiments were run at core-flow circuit of LABPETRO-UNICAMP. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Serpentine Geometry Plasma Actuators for Flow Control

    Science.gov (United States)

    2013-08-23

    electrical power is supplied to them. As a method of introducing perturbations for low speed flow control, dielectric barrier discharge ( DBD ) actuators...SERPENTINE GEOMETRY DBD ACTUATORS DBD actuators are devices consisting of two asymmetri- cally placed actuators separated by a dielectric material and exposed...parameters can be found in Table I. The effects of plasma actuation are FIG. 1. (a) Schematic of DBD plasma actuator and the generated body force. (b

  17. Chaos control in traffic flow models

    CERN Document Server

    Shahverdiev, E M; Shahverdiev, Elman Mohammed; Tadaki, Shin-ichi

    1998-01-01

    Chaos control in some of the one- and two-dimensional traffic flow dynamical models in the mean field theory is studied.One dimensional model is investigated taking into account the effect of random delay. Two dimensional model takes into account the effects of overpasses, symmetric distribution of cars and blockages of cars moving in the same direction. Chaos synchronization is performed within both replica and nonreplica approaches, and using parameter perturbation method.

  18. Distributed Power-Flow Controller (DPFC Simulation

    Directory of Open Access Journals (Sweden)

    T Jagan Mohan Rao

    2014-10-01

    Full Text Available This paper describes the steady-state response and control of power in transmission line equipped with FACTS devices. Detailed simulations are carried out on two -machine systems to illustrate the control features of these devices and their influence to increase power transfer capability and improve system reliability. The DPFC is derived from the unified power-flow controller (UPFC and DPFC has the same control capability as the UPFC. The DPFC can be considered as a UPFC with an eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmission lines at the third -harmonic frequency. The interaction between the DPFC, the network and the machines are analyzed.

  19. Controlling flow time delays in flexible manufacturing cells

    NARCIS (Netherlands)

    Slomp, J.; Caprihan, R.; Bokhorst, J. A. C.

    2009-01-01

    Flow time delays in Flexible Manufacturing Cells (FMCs) are caused by transport and clamping/reclamping activities. This paper shows how dynamic scheduling parameters may control the flow times of jobs and the available task windows for flow time delays.

  20. Wake flow control using a dynamically controlled wind turbine

    Science.gov (United States)

    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).

  1. Electromechanically Actuated Valve for Controlling Flow Rate

    Science.gov (United States)

    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

  2. Controlling social media flow: avoiding unwanted publication

    Directory of Open Access Journals (Sweden)

    Elodie CRESPEL

    2016-12-01

    Full Text Available Social media blurs the boundaries of social life and brings together different spheres such as family, work or friends in the same online space. Users begin to post less intimate details about themselves, and they want to see fewer details of the private lives of others as well. Users want to better control what they read on social media. This paper studies the use of information and communication technology in social and cultural context. A qualitative approach provides a rich and detailed description of contexts and motivations of social media use. It shows that users are still negotiating the endless flow of information coming from social media.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  5. On-Chip Flow Control for 2-PhaseNanofluidics

    NARCIS (Netherlands)

    Shui, Lingling; Berg, van den Albert; Eijkel, Jan C.T.; Kim, Tae Song; Lee, Yoon-Sik; Chung, Twek-Dong; Jeon, Noo Li; Lee, Sang-Hoon; Suh, Kahp-Yang; Choo, Jaebm; Kim, Yong-Kweon

    2009-01-01

    We developed a novel method to control two-phase flow in nanochannels using regulating microchannels connected to the nanochannels. The flow rate inside a nanochannel can be regulated based on the pressure drops along the channel network. Stable flows with flow rates as low as 10-5 µL.min-1 (< pL.s-

  6. Particle and chemical control using tunnel flow

    Energy Technology Data Exchange (ETDEWEB)

    Chilese, Frank; Delgado, Gildardo R.; Wack, Daniel; Torczynski, John R.

    2017-09-12

    An apparatus for contaminant control, having: a first optical assembly including: a first light homogenizer tunnel with: a first end connected to an extreme ultra-violet light source, a second end in communication with a destination chamber, a first enclosed space, and, a first gas input arranged to introduce a first gas such that the first gas flows in a first direction toward the first end and in a second direction toward the second end. The apparatus alternately having: a second optical assembly including: a second light homogenizer tunnel with: a third end connected to an extreme ultra-violet light source, a fourth end in communication with a destination chamber, a second enclosed space, a diffusion barrier tube including: a fifth end facing the fourth end and a sixth end in communication with a destination chamber, and a second gas input between the second light homogenizer tunnel and the diffusion tube.

  7. Synchronization trigger control system for flow visualization

    Science.gov (United States)

    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.

  8. Control of Smoke Flow in a Tunnel

    Directory of Open Access Journals (Sweden)

    K Brahim

    2013-01-01

    Full Text Available This study focuses on fires in road tunnels in order to increase the level of security for users. This paper proposed numerical investigations carried out on a small scale tunnel model to study the fire-induced smoke control by longitudinal and longitudinal-natural ventilation systems. We studied the effect of two ventilation systems on the temperature distribution and stratification of the pollutant to estimate the effectiveness of ventilation systems. The flow is characterized by the temperature fields, temperature profiles and the Froude number. The numerical tool used is FDS (version 4.0. This numerical study requires validation with experiment and numerical results and comparison with the model developed by Kunsch J.P. to evaluate the critical velocity. However, good agreement with experimental results, it confirms the possibility of using this code in the problem.

  9. Glial and neuronal control of brain blood flow

    DEFF Research Database (Denmark)

    Attwell, David; Buchan, Alastair M; Charpak, Serge

    2010-01-01

    Blood flow in the brain is regulated by neurons and astrocytes. Knowledge of how these cells control blood flow is crucial for understanding how neural computation is powered, for interpreting functional imaging scans of brains, and for developing treatments for neurological disorders. It is now...... in our understanding of cerebral blood flow control have important implications for the development of new therapeutic approaches....

  10. Insect vision: controlling actions through optic flow.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    2013-05-01

    understanding of cavity flow physics gained through many of the early studies. More recent experimental studies like Heller and Delfs (1996), Unalmis et...75-491, 1975. Heller, H., and Delfs , J., “Cavity Pressure Oscillations: The Generating Mechanisms Visualized,” Journal of Sound and Vibration, Vol

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

    Science.gov (United States)

    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.

  13. Synthetic Capillaries to Control Microscopic Blood Flow

    Science.gov (United States)

    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.

  14. Improving Software Systems By Flow Control Analysis

    Directory of Open Access Journals (Sweden)

    Piotr Poznanski

    2012-01-01

    Full Text Available Using agile methods during the implementation of the system that meets mission critical requirements can be a real challenge. The change in the system built of dozens or even hundreds of specialized devices with embedded software requires the cooperation of a large group of engineers. This article presents a solution that supports parallel work of groups of system analysts and software developers. Deployment of formal rules to the requirements written in natural language enables using formal analysis of artifacts being a bridge between software and system requirements. Formalism and textual form of requirements allowed the automatic generation of message flow graph for the (sub system, called the “big-picture-model”. Flow diagram analysis helped to avoid a large number of defects whose repair cost in extreme cases could undermine the legitimacy of agile methods in projects of this scale. Retrospectively, a reduction of technical debt was observed. Continuous analysis of the “big picture model” improves the control of the quality parameters of the software architecture. The article also tries to explain why the commercial platform based on UML modeling language may not be sufficient in projects of this complexity.

  15. Review of hybrid laminar flow control systems

    Science.gov (United States)

    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.

  16. Use of UPFC device controlled by fuzzy logic controllers for decoupled power flow control

    Directory of Open Access Journals (Sweden)

    Ivković Sanja

    2014-01-01

    Full Text Available This paper investigates the possibility of decoupled active and reactive power flow control in a power system using a UPFC device controlled by fuzzy logic controllers. A Brief theoretical review of the operation principles and applications of UPFC devices and design principles of the fuzzy logic controller used are given. A Matlab/Simulink model of the system with UPFC, the fuzzy controller setup, and graphs of the results are presented. Conclusions are drawn regarding the possibility of using this system for decoupled control of the power flow in power systems based on analysis of these graphs.

  17. Recent progress in flow control for practical flows results of the STADYWICO and IMESCON projects

    CERN Document Server

    Barakos, George; Luczak, Marcin

    2017-01-01

    This book explores the outcomes on flow control research activities carried out within the framework of two EU-funded projects focused on training-through-research of Marie Sklodowska-Curie doctoral students. The main goal of the projects described in this monograph is to assess the potential of the passive- and active-flow control methods for reduction of fuel consumption by a helicopter. The research scope encompasses the fields of structural dynamics, fluid flow dynamics, and actuators with control. Research featured in this volume demonstrates an experimental and numerical approach with a strong emphasis on the verification and validation of numerical models. The book is ideal for engineers, students, and researchers interested in the multidisciplinary field of flow control. Provides highly relevant and up-to-date information on the topic of flow control; Includes assessments of a wide range of flow-control technologies and application examples for fixed and rotary-wing configurations; Reinforces reader u...

  18. Computational Modeling of Flow Control Systems for Aerospace Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Clear Science Corp. proposes to develop computational methods for designing active flow control systems on aerospace vehicles with the primary objective of...

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

    Science.gov (United States)

    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

  20. Flow Control for Supersonic Inlet Applications

    Science.gov (United States)

    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

  1. Topographic Controls on Landslide and Debris-Flow Mobility

    Science.gov (United States)

    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.

  2. Experimental Research on Flow Separation Control using Synthetic Jet Actuators

    NARCIS (Netherlands)

    Koopmans, E.; Hoeijmakers, H.W.M.

    2014-01-01

    Airplane wings can suffer from flow separation, which greatly decreases their aerodynamic per-formance. The flow separates due to the bound-ary layer possessing insufficient momentum to engage the adverse pressure gradient along the airfoil surface. Flow separation control actively influences the fl

  3. Experimental research on flow separation control using synthetic jet actuators

    NARCIS (Netherlands)

    Koopmans, E.; Hoeijmakers, H.W.M.

    2014-01-01

    Airplane wings can suffer from flow separation, which greatly decreases their aerodynamic per-formance. The flow separates due to the bound-ary layer possessing insufficient momentum to engage the adverse pressure gradient along the airfoil surface. Flow separation control actively influences the fl

  4. Fluid flow control with transformation media

    CERN Document Server

    Urzhumov, Yaroslav A

    2011-01-01

    We introduce a new concept for the manipulation of fluid flow around three-dimensional bodies. Inspired by transformation optics, the concept is based on a mathematical idea of coordinate transformations, and physically implemented with anisotropic porous media permeable to the flow of fluids. In two different situations - for an impermeable object situated either in a free-flowing fluid or in a fluid-filled porous medium - we show that the object can be coated with a properly chosen inhomogeneous, anisotropic permeable medium, such as to preserve the streamlines of flow and the pressure distribution that would have existed in the absence of the object. The proposed fluid flow cloak completely eliminates any disturbance of the flow by the object, including the downstream wake. Consequently, the structure helps prevent the onset of turbulence by keeping the flow laminar even above the typical critical Reynolds number for the object of the same shape and size. The cloak also cancels the viscous drag force. This...

  5. Microjet flow control in an ultra-compact serpentine inlet

    Institute of Scientific and Technical Information of China (English)

    Da Xingy; Fan Zhaolin; Fan Jianchao; Zeng Liquan; Rui Wei; Zhou Run

    2015-01-01

    Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interface plane (AIP) face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control (MFC) effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90? circumferential distortion pattern to 180? circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the momentum coefficient affects the control effectiveness in a dual stepping manner.

  6. Microjet flow control in an ultra-compact serpentine inlet

    Directory of Open Access Journals (Sweden)

    Da Xingya

    2015-10-01

    Full Text Available Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interface plane (AIP face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control (MFC effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the momentum coefficient affects the control effectiveness in a dual stepping manner.

  7. Active Control of Jet Engine Inlet Flows

    Science.gov (United States)

    2007-03-31

    investigation was performed with no pressure applied across the fan. To measure the high-frequency, unsteady jet velocity, an IFA 300 hot - wire anemometry ...flow at the engine face. Recommendations for the measurement devices include hot -film or hot - wire sensors and wall-mounted, high frequency pressure...the blade and creates flow instabilities that convect through the later compressor stages. This report presents a study performed to gain an

  8. Intelligent Control for Improvements in PEM Fuel Cell Flow Performance

    Institute of Scientific and Technical Information of China (English)

    Jonathan G Williams; Guoping Liu; Senchun Chai; David Rees

    2008-01-01

    The performance of fuel cells and the vehicle applications they are embedded into depends on a delicate balance of the correct temperature, humidity, reactant pressure, purity and flow rate. This paper successfully investigates the problem related to flow control with implementation on a single cell membrane electrode assembly (MEA). This paper presents a systematic approach for performing system identification using recursive least squares identification to account for the non-linear parameters of the fuel cell. Then, it presents a fuzzy controller with a simplified rule base validated against real time results with the existing flow controller which calculates the flow required from the stoichiometry value.

  9. Power flow analysis for DC voltage droop controlled DC microgrids

    DEFF Research Database (Denmark)

    Li, Chendan; Chaudhary, Sanjay; Dragicevic, Tomislav

    2014-01-01

    This paper proposes a new algorithm for power flow analysis in droop controlled DC microgrids. By considering the droop control in the power flow analysis for the DC microgrid, when compared with traditional methods, more accurate analysis results can be obtained. The algorithm verification...... is carried out by comparing the calculation results with detailed time domain simulation results. With the droop parameters as variables in the power flow analysis, their effects on power sharing and secondary voltage regulation can now be analytically studied, and specialized optimization in the upper level...... control can also be made accordingly. Case studies on power sharing and secondary voltage regulation are carried out using proposed power flow analysis....

  10. A Calculus for Control Flow Analysis of Security Protocols

    DEFF Research Database (Denmark)

    Buchholtz, Mikael; Nielson, Hanne Riis; Nielson, Flemming

    2004-01-01

    analysis methodology. We pursue an analysis methodology based on control flow analysis in flow logic style and we have previously shown its ability to analyse a variety of security protocols. This paper develops a calculus, LysaNS that allows for much greater control and clarity in the description...

  11. State Space Reduction of Linear Processes Using Control Flow Reconstruction

    NARCIS (Netherlands)

    Pol, van de Jaco; Timmer, Mark; Liu, Z.; Ravn, A.P.

    2009-01-01

    We present a new method for fighting the state space explosion of process algebraic specifications, by performing static analysis on an intermediate format: linear process equations (LPEs). Our method consists of two steps: (1) we reconstruct the LPE's control flow, detecting control flow parameters

  12. State Space Reduction of Linear Processes using Control Flow Reconstruction

    NARCIS (Netherlands)

    Pol, van de Jaco; Timmer, Mark

    2009-01-01

    We present a new method for fighting the state space explosion of process algebraic specifications, by performing static analysis on an intermediate format: linear process equations (LPEs). Our method consists of two steps: (1) we reconstruct the LPE's control flow, detecting control flow parameters

  13. Boundary control of fluid flow through porous media

    DEFF Research Database (Denmark)

    Hasan, Agus; Foss, Bjarne; Sagatun, Svein Ivar

    2010-01-01

    The flow of fluids through porous media can be described by the Boussinesq’s equation with mixed boundary conditions; a Neumann’s boundary condition and a nonlinear boundary condition. The nonlinear boundary condition provides a means to control the fluid flow through porous media. In this paper,......, some stabilizing controllers are constructed for various cases using Lyapunov design....

  14. MAG-GATE System for Molten metal Flow Control

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. COMPUTATIONAL FLOW RATE FEEDBACK AND CONTROL METHOD IN HYDRAULIC ELEVATORS

    Institute of Scientific and Technical Information of China (English)

    Xu Bing; Ma Jien; Lin Jianjie

    2005-01-01

    The computational flow rate feedback and control method, which can be used in proportional valve controlled hydraulic elevators, is discussed and analyzed. In a hydraulic elevator with this method, microprocessor receives pressure information from the pressure transducers and computes the flow rate through the proportional valve based on pressure-flow conversion real time algorithm. This hydraulic elevator is of lower cost and energy consumption than the conventional closed loop control hydraulic elevator whose flow rate is measured by a flow meter. Experiments are carried out on a test rig which could simulate the load of hydraulic elevator. According to the experiment results, the means to modify the pressure-flow conversion algorithm are pointed out.

  16. Power flow control of intertied ac microgrids

    DEFF Research Database (Denmark)

    Nutkani, Inam Ullah; Loh, Poh Chiang; Blaabjerg, Frede

    2013-01-01

    of interlinking power converters. Active and reactive power flows of these converters should preferably be managed autonomously without demanding for fast communication links. A scheme that can fulfill the objectives is now proposed, which upon realised, will result in more robustly integrated microgrids...

  17. Admission Control Algorithm for Guaranteeing Real-Time Anycast Flow

    Institute of Scientific and Technical Information of China (English)

    Weijia Jia; Zhang Chuanlin

    2002-01-01

    In this paper, we study admission control algorithm for anycast flow with real-time constraints. With the given time requirement, when the result of this algorithm give succeed information, we find route for the anycast flow requesting. Therefore, what we need to do is testing if the corresponding path rj has enough bandwidth for coming anycast flow requirement at source S with end-to-end deadline D. This admission control is scalable in terms of the number of flows can be admitted through local information of the routes.

  18. Microfluidic droplet control by photothermal interfacial flow

    OpenAIRE

    Muto, M.; Motosuke, M; 4th Micro and Nano Flows Conference (MNF2014)

    2014-01-01

    This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, U...

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

    Science.gov (United States)

    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.

  20. Efficient Flow Control Scheme in Multimedia Cloud Computing

    Directory of Open Access Journals (Sweden)

    Jinsheng Tan

    2013-10-01

    Full Text Available As multimedia cloud computing involving a great deal of calculations about graphics, images, audio and video, which consume a lot of resources and is a key issue toward traffic control. The characteristics of traditional HTB serial determine the bottleneck of its processing speed. The author provides a kind of mechanism based on multi-core processors pipeline style and parallelization of HTB flow control, makes the improvement of the analysis and algorithm toward flow control, and finally carries out experimental testing. The results show that: compared to traditional flow control, the multi-core processors pipeline style and parallelization of HTB flow control not only has greatly improved on the processing power, but still maintained a good stability, so as to meet the multimedia cloud computing users and data scale

  1. Photothermally controlled Marangoni flow around a micro bubble

    Energy Technology Data Exchange (ETDEWEB)

    Namura, Kyoko, E-mail: namura.kyoko.57r@st.kyoto-u.ac.jp; Nakajima, Kaoru; Kimura, Kenji; Suzuki, Motofumi [Department of Micro Engineering, Kyoto University, Kyoto daigaku-Katsura, Kyoto 615-8540 (Japan)

    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.

  2. International Conference on Instability and Control of Massively Separated Flows

    CERN Document Server

    Soria, Julio

    2015-01-01

    This book contains the outcome of the international meeting on instability, control and noise generated by massive flow separation that was organized at the Monash Center, in Prato, Italy, September 4-6, 2013. The meeting served as the final review of the EU-FP7 Instability and Control of Massively Separated Flows Marie Curie travel grant and was supported by the European Office of Aerospace Research and Development. Fifty leading specialists from twelve countries reviewed the progress made since the 50s of the last century and discussed modern analysis techniques, advanced experimental flow diagnostics, and recent developments in active flow control techniques from the incompressible to the hypersonic regime. Applications involving massive flow separation and associated instability and noise generation mechanisms of interest to the aeronautical, naval and automotive industries have been addressed from a theoretical, numerical or experimental point of view, making this book a unique source containing the stat...

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

    Science.gov (United States)

    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.

  4. Advanced flow measurement and active flow control of aircraft with MEMS

    Institute of Scientific and Technical Information of China (English)

    Jiang Chengyu; Deng Jinjun; Ma Binghe; Yuan Weizheng

    2012-01-01

    Advanced flow measurement and active flow control need the development of new type devices and systems. Micro-electro-mechanical systems (MEMS) technologies become the important and feasible approach for micro transducers fabrication. This paper introduces research works of MEMS/NEMS Lab in flow measurement sensors and active flow control actuators. Micro sensors include the flexible thermal sensor array, capacitive shear stress sensor and high sensitivity pressure sensor. Micro actuators are the balloon actuator and synthetic jet actuator respectively. Through wind tunnel test, these micro transducers achieve the goals of shear stress and pressure distribution measurement, boundary layer separation control, lift enhancement, etc. And unmanned aerial vehicle (UAV) flight test verifies the ability of maneuver control of micro actuator. In the future work, micro sensor and actuator can be combined into a closed-loop control system to construct aerodynamic smart skin system for aircraft.

  5. Automatic air flow control in air conditioning ducts

    Science.gov (United States)

    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.

  6. Glial and neuronal control of brain blood flow

    DEFF Research Database (Denmark)

    Attwell, David; Buchan, Alastair M; Charpak, Serge

    2010-01-01

    Blood flow in the brain is regulated by neurons and astrocytes. Knowledge of how these cells control blood flow is crucial for understanding how neural computation is powered, for interpreting functional imaging scans of brains, and for developing treatments for neurological disorders. It is now...

  7. Microvalves for precise dosing: proportional flow control on a chip

    NARCIS (Netherlands)

    Groen, Maarten Sytze

    2015-01-01

    Precise control of fluid flow becomes increasingly challenging as systems and instruments are scaled down. Smaller dimensions allow smaller flow ranges, but also leave smaller margins for error in performance. Reliable and effective fabrication and assembly procedures are therefore a primary require

  8. Electro-osmotically controllable multi-flow microreactor

    NARCIS (Netherlands)

    Kohlheyer, Dietrich; Besselink, Geert A.J.; Lammertink, Rob G.H.; Schlautmann, Stefan; Unnikrishnan, Sandeep; Schasfoort, Richard B.M.

    2005-01-01

    An adjustable diffusion-based microfluidic reactor is presented here, which is based on electro-osmotic guiding of reagent samples. The device consists of a laminar flow chamber with two separate reagent inlets. The position and the width of the two sample streams in the flow chamber can be controll

  9. On load flow control in electric power systems

    Energy Technology Data Exchange (ETDEWEB)

    Herbig, Arnim

    2000-01-01

    This dissertation deals with the control of active power flow, or load flow in electric power systems. During the last few years, interest in the possibilities to control the active power flows in transmission systems has increased significantly. There is a number of reasons for this, coming both from the application side - that is, from power system operations - and from the technological side. where advances in power electronics and related technologies have made new system components available. Load flow control is by nature a multi-input multi-output problem, since any change of load flow in one line will be complemented by changes in other lines. Strong cross-coupling between controllable components is to be expected, and the possibility of adverse interactions between these components cannot be rejected straightaway. Interactions with dynamic phenomena in the power system are also a source of concern. Three controllable components are investigated in this thesis, namely the controlled series capacitor (CSC), the phase angle regulator (PAR), and the unified power flow controller (UPFC). Properties and characteristics of these devices axe investigated and discussed. A simple control strategy is proposed. This strategy is then analyzed extensively. Mathematical methods and physical knowledge about the pertinent phenomena are combined, and it is shown that this control strategy can be used for a fairly general class of devices. Computer simulations of the controlled system provide insight into the system behavior in a system of reasonable size. The robustness and stability of the control system are discussed as are its limits. Further, the behavior of the control strategy in a system where the modeling allows for dynamic phenomena are investigated with computer simulations. It is discussed under which circumstances the control action has beneficial or detrimental effect on the system dynamics. Finally, a graphical approach for analyzing the effect of controllers

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

    Science.gov (United States)

    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.

  11. Effect of Mixed Traffic Flow on Control Delay at Signalized ...

    African Journals Online (AJOL)

    Effect of Mixed Traffic Flow on Control Delay at Signalized Intersections. ... Journal of Civil Engineering Research and Practice ... There are several methods available for operational analysis including mathematical models and traffic ...

  12. Chaos control applied to coherent states in transitional flows

    Energy Technology Data Exchange (ETDEWEB)

    Pausch, Marina; Eckhardt, Bruno, E-mail: bruno.eckhardt@physik.uni-marburg.de [Fachbereich Physik, Philipps-Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)

    2011-12-22

    Chaos control refers to a group of techniques by which an otherwise unstable dynamical state of a system can be maintained by small control forces. We here discuss their application to stabilizing the fixed points in a low dimensional model for shear flows. The simulations demonstrate a prototypical application of chaos control, show that control is almost always possible, and give insights into optimizing the control matrix from a design point of view.

  13. Dynamic control of the flow of terahertz light

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    Guided propagation of THz light has been intensely developed recently. We describe our efforts towards dynamic, optical control of the flow of light in waveguide structures, enabling reconfigurable photonic components for the terahertz frequency range.......Guided propagation of THz light has been intensely developed recently. We describe our efforts towards dynamic, optical control of the flow of light in waveguide structures, enabling reconfigurable photonic components for the terahertz frequency range....

  14. A sliding mode controller for vehicular traffic flow

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. Steady State Stokes Flow Interpolation for Fluid Control

    DEFF Research Database (Denmark)

    Bhatacharya, Haimasree; Nielsen, Michael Bang; Bridson, Robert

    2012-01-01

    Fluid control methods often require surface velocities interpolated throughout the interior of a shape to use the velocity as a feedback force or as a boundary condition. Prior methods for interpolation in computer graphics — velocity extrapolation in the normal direction and potential flow...... — suffer from a common problem. They fail to capture the rotational components of the velocity field, although extrapolation in the normal direction does consider the tangential component. We address this problem by casting the interpolation as a steady state Stokes flow. This type of flow captures...... the rotational components and is suitable for controlling liquid animations where tangential motion is pronounced, such as in a breaking wave...

  17. Controlling Disorder in Traffic Flow by Perturbation

    Institute of Scientific and Technical Information of China (English)

    LIKe-Ping; GAOZi-You; CHENTian-Lun

    2004-01-01

    We propose a new technique for controlling disorder in traffic system. A kind of control signal which can be considered as a perturbation has been designated at a given site (perturbation point) of the single-lane highway. When a vehicle passes the perturbation point at a time, the velocity of the vehicle will be changed at the next time by the perturbation. This technique is tested for the deterministic NaSch traffic model. The simulation results indicate that the traffic system can be transited from the disorder states to the order states, such as fixed-point, periodic motion, etc.

  18. A Numerical Proof of Concept for Thermal Flow Control

    Directory of Open Access Journals (Sweden)

    V. Dragan

    2017-02-01

    Full Text Available In this paper computational fluid dynamics is used to provide a proof of concept for controlled flow separation using thermal wall interactions with the velocity boundary layer. A 3D case study is presented, using a transition modeling Shear Stress Transport turbulence model. The highly loaded single slot flap airfoil was chosen to be representative for a light aircraft and the flow conditions were modeled after a typical landing speed. In the baseline case, adiabatic walls were considered while in the separation control case, the top surface of the flaps was heated to 500 K. This heating lead to flow separation on the flaps and a significant alteration of the flow pattern across all the elements of the wing. The findings indicate that this control method has potential, with implications in both aeronautical as well as sports and civil engineering applications.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  1. Passive flow control by membrane wings for aerodynamic benefit

    Science.gov (United States)

    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.

  2. Adjoint-based Optimal Flow Control for Compressible DNS

    CERN Document Server

    Otero, J Javier; Sandberg, Richard D

    2016-01-01

    A novel adjoint-based framework oriented to optimal flow control in compressible direct numerical simulations is presented. Also, a new formulation of the adjoint characteristic boundary conditions is introduced, which enhances the stability of the adjoint simulations. The flow configuration chosen as a case study consists of a two dimensional open cavity flow with aspect ratio $L/H=3$ and Reynolds number $Re=5000$. This flow configuration is of particular interest, as the turbulent and chaotic nature of separated flows pushes the adjoint approach to its limit. The target of the flow actuation, defined as cost, is the reduction of the pressure fluctuations at the sensor location. To exploit the advantages of the adjoint method, a large number of control parameters is used. The control consists of an actuating sub-domain where a two-dimensional body force is applied at every point within the sub-volume. This results in a total of $2.256 \\cdot 10^6$ control parameters. The final actuation achieved a successful ...

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

    Science.gov (United States)

    2006-03-31

    Methodos Numericos in Ingenieria 2005, Granada Y 3 rd Symposium on Global Flow Instability and Control September 2005 Crete, Greece. * AIAA San...valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From - To...31-03-2006 Final 01-02-2003 To 31-12-2005 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Global Instability and Control of Low Pressure Turbine Flows 5b

  4. 3rd Active Flow and Combustion Control Conference

    CERN Document Server

    2015-01-01

    The book reports on the latest theoretical and experimental advances in the  field of active flow and combustion control. It covers new developments in actuator technology and sensing, in robust and optimal open- and closed-loop control, as well as in model reduction for control. It collects contributions presented during the third edition of the Active Flow and Combustion Control conference, held in September 10-12, 2014 at the Technische Universität Berlin (Germany). This conference, as well as the research presented in the book, have been supported by the collaborative research center SFB 1029 -Substantial efficiency increase in gas turbines through direct use of coupled unsteady combustion and flow dynamics, funded by the DFG (German Research Foundation).

  5. Experimental Study on the Unified Power Flow Controller

    Science.gov (United States)

    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.

  6. Investigation of dielectric barrier discharge plasma flow control

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Effects of plasma flow control are researched on the basis of plasma exciting flow experiments and numerical simulations. Turbulent model is more effective than laminar model in plasma numerical simulation as results showed. Both plasma exciting effects of acceleration and flow separation suppression are investigated through experiments carried on the flat plate and the compressor cascades. The results demonstrate that boundary layer characteristic is modified by plasma exciting. Distributions of total pressure and velocity in the wake are improved notably for 20 m/s coming velocity and the effect of plasma can still be observed while velocity is increased to 50 m/s. For low velocity flow, plasma exciting is effective in flow separation suppression.

  7. Blood flow controls bone vascular function and osteogenesis

    Science.gov (United States)

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

    Science.gov (United States)

    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.

  9. Review of actuators for high speed active flow control

    Institute of Scientific and Technical Information of China (English)

    WANG Lin; LUO ZhenBing; XIA ZhiXun; LIU Bing; DENG Xiong

    2012-01-01

    Actuators are one of the key points for the development of active flow control technology.Efficient methods of high speed flow control can provide enhanced propulsive efficiency and at the same time enable safe and maneuverable high speed flight.The development of high speed flight technology promotes the emergence of novel and robust actuators.This review introduces the state of the art in the development of actuators that can be used in high speed active flow control.The classification and different operation criteria of the actuators are discussed.The specifications,mechanisms and applications of various popular actuator types including fluidic,mechanical,and plasma actuators are described.Based on the realistic need of high speed flow control and the existing results of actuators,a new actuator design method is proposed.At last,the merits and drawbacks of the actuators are summarized and some suggestions on the development of active flow control technology are put forward.

  10. Improving wind turbine array efficiency through active flow control

    Science.gov (United States)

    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.

  11. Fluidic Control of Nozzle Flow: Some Performance Measurements

    Science.gov (United States)

    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.

  12. Light Control of the Flow of Phototactic Microswimmer Suspensions

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. Modelling and Control Design of Unified Power Flow Controller for Various Control Strategies

    Directory of Open Access Journals (Sweden)

    T. Nireekshana

    2010-11-01

    Full Text Available Unified Power Flow Controller (UPFC is used to control the power flow in the transmission systems by controlling the impedance, voltage magnitude and phase angle. This controller offers advantages in terms of static and dynamic operation of the power system. It also brings in new challenges in power electronics and power system design. The basic structure of the UPFC consists of two voltage source inverter (VSI; where one converter is connected in parallel to the transmission line while the other is in series with the transmission line. The aim of the paper is to develop a control strategy for UPFC, modeling UPFC using MATLAB/SIMULINK and to analyze the control strategy to use the series voltage injection and shunt current injection for UPFC control. To simplify the design procedure we carry out the design for the series and shunt branches separately.In each case, a simple equivalent circuit represents the external system. The design has to be validated when the various subsystems are integrated.

  15. Effect of passive flow-control devices on turbulent low-speed base flow

    Science.gov (United States)

    Heidari-Miandoab, Farid

    Some configurations of blunt trailing-edge airfoils are known to have a lower pressure drag compared to sharp trailing-edge airfoils. However, this advantage in addition to the structural advantage of a thick trailing-edge airfoil is offset by its high base drag. At subsonic velocities, this is attributed to the low-pressure base flow dominated by a Karman vortex street. In the limiting case, the steady separated flow over a rearward-facing step is attained if the periodically shed vortices from a blunt trailing-edge are suppressed by the addition of a base spiltter-plate. Experimental studies in the Old Dominion University Low-Speed Closed-Circuit Wind Tunnel were conducted to examine the effect of several passive flow-control devices such as Wheeler doublets and wishbone vortex generators, longitudinal surface grooves, base cavities, and serrations on the characteristics of two- and three-dimensional base flows. Flow over flat-plate airfoil and rearward-facing step models was studied in the turbulent incompressible subsonic flow regime. Models with trailing-edge and step-sweep angles of 0, 30, and 45 degrees with respect to the crossflow direction were considered. Constant-temperature hot-wire anemometry, infrared surface thermography, and pitot-static probes were used to conduct flow measurements. The parameters measured included vortex shedding frequency, convective heat-transfer rates, base pressure, and flow reattachment distance. Surveys of mean velocity profiles in the wake were also conducted. Results have shown that most of the flow control devices tested increased the base pressure of the 2-D and 3-D flat-plate airfoils. Use of longitudinal surface grooves resulted in shorter flow reattachment distances and higher convective heat transfer rates downstream of the 2-D rearward-facing steps.

  16. Feedback Control of Turbulent Shear Flows by Genetic Programming

    CERN Document Server

    Duriez, Thomas; von Krbek, Kai; Bonnet, Jean-Paul; Cordier, Laurent; Noack, Bernd R; Segond, Marc; Abel, Markus; Gautier, Nicolas; Aider, Jean-Luc; Raibaudo, Cedric; Cuvier, Christophe; Stanislas, Michel; Debien, Antoine; Mazellier, Nicolas; Kourta, Azeddine; Brunton, Steven L

    2015-01-01

    Turbulent shear flows have triggered fundamental research in nonlinear dynamics, like transition scenarios, pattern formation and dynamical modeling. In particular, the control of nonlinear dynamics is subject of research since decades. In this publication, actuated turbulent shear flows serve as test-bed for a nonlinear feedback control strategy which can optimize an arbitrary cost function in an automatic self-learning manner. This is facilitated by genetic programming providing an analytically treatable control law. Unlike control based on PID laws or neural networks, no structure of the control law needs to be specified in advance. The strategy is first applied to low-dimensional dynamical systems featuring aspects of turbulence and for which linear control methods fail. This includes stabilizing an unstable fixed point of a nonlinearly coupled oscillator model and maximizing mixing, i.e.\\ the Lyapunov exponent, for forced Lorenz equations. For the first time, we demonstrate the applicability of genetic p...

  17. Rate Control Protocol for Fast Flows: A Survey

    Directory of Open Access Journals (Sweden)

    Mr. Gaganpreet Singh,

    2014-01-01

    Full Text Available In today’s world, congestion control is a main objective to maximize fairness, utilization and throughput of the Internet. Every protocol has its own features to handle the congestion. The most widely used protocol over the Internet is Transfer Control Protocol. It aims at reliable and in order delivery of bytes to the higher layer and it also protect the network from congestive control. Other congestion control protocols are XCP and RCP. These new protocols are advancement over TCP. We study new congestion control protocol like Rate Control Protocol that make flows complete frequently as compared to TCP and other version of TCP and XCP. In this paper we have presented a comparison between TCP, XCP and RCP, which shows that RCP is a superior choice to use over the Internet to make flows complete quickly

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

    Science.gov (United States)

    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.

  19. Session Types for Access and Information Flow Control

    OpenAIRE

    Capecchi, Sara; Castellani, Ilaria; Dezani-Ciancaglini, Mariangiola; Rezk, Tamara

    2010-01-01

    We consider a calculus for multiparty sessions with delegation, enriched with security levels for session participants and data. We propose a type system that guarantees both session safety and a form of access control. Moreover, this type system ensures secure information flow, including controlled forms of declassification. In particular, it prevents leaks due to the specific control constructs of the calculus, such as session opening, selection, branching and delegation. We illustrate the ...

  20. Optimal Control of Transient Flow in Natural Gas Networks

    CERN Document Server

    Zlotnik, Anatoly; Backhaus, Scott

    2015-01-01

    We outline a new control system model for the distributed dynamics of compressible gas flow through large-scale pipeline networks with time-varying injections, withdrawals, and control actions of compressors and regulators. The gas dynamics PDE equations over the pipelines, together with boundary conditions at junctions, are reduced using lumped elements to a sparse nonlinear ODE system expressed in vector-matrix form using graph theoretic notation. This system, which we call the reduced network flow (RNF) model, is a consistent discretization of the PDE equations for gas flow. The RNF forms the dynamic constraints for optimal control problems for pipeline systems with known time-varying withdrawals and injections and gas pressure limits throughout the network. The objectives include economic transient compression (ETC) and minimum load shedding (MLS), which involve minimizing compression costs or, if that is infeasible, minimizing the unfulfilled deliveries, respectively. These continuous functional optimiza...

  1. Unsteady aerodynamics and flow control for flapping wing flyers

    Science.gov (United States)

    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

  2. Aerodynamic control in compressible flow using microwave driven discharges

    Science.gov (United States)

    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.

  3. Flow Control Strategy for the High Speed Network Based on Control Theory

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Design of an effective congestion control scheme is a hot topic in the development of computer network. The flow control scheme can adjust the packet sending rate in source host, thus effectively avoiding the network congestion. This paper proposes a new flow control scheme based on discrete control theory. The simulation results show that this method can adjust the sending rate and queue level in buffer rapidly and effectively. The method is easy to implement and applicable to high speed networks.

  4. Control volume based modelling of compressible flow in reciprocating machines

    DEFF Research Database (Denmark)

    Andersen, Stig Kildegård; Thomsen, Per Grove; Carlsen, Henrik

    2004-01-01

    conservation laws for mass, energy, and momentum applied to a staggered mesh consisting of two overlapping strings of control volumes. Loss mechanisms can be included directly in the governing equations of models by including them as terms in the conservation laws. Heat transfer, flow friction......, and multidimensional effects must be calculated using empirical correlations; correlations for steady state flow can be used as an approximation. A transformation that assumes ideal gas is presented for transforming equations for masses and energies in control volumes into the corresponding pressures and temperatures...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  7. Passive Flow Separation Control Mechanism Inspired by Shark Skin

    Science.gov (United States)

    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.

  8. Implementation of Logic Flow in Planning and Production Control

    Directory of Open Access Journals (Sweden)

    Ulewicz Robert

    2016-03-01

    Full Text Available The article presents the results of analysis, the use of continuous flow of logic at the stage of production planning and control of the company producing furniture. The concept of continuous flow tends to regulate the flow of materials in a manner that provides the shortest flow path without unnecessary activities (Muda is a Japanese word meaning waste, a constant takt and defined throughput at constant resource requirements for the so-called transfer of material through the whole process. In the study Glenday’d sieve method was used to identify the correct area, which requires the value stream mapping, and areas called excessive complexity, which do not provide added value. The use of Glenday’s sieve method made it possible to identify areas in which it must be improve production capacity.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  11. Tutorial on Feedback Control of Flows, Part I: Stabilization of Fluid Flows in Channels and Pipes

    Directory of Open Access Journals (Sweden)

    Ole M. Aamo

    2002-07-01

    Full Text Available The field of flow control has picked up pace over the past decade or so, on the promise of real-time distributed control on turbulent scales being realizable in the near future. This promise is due to the micromachining technology that emerged in the 1980s and developed at an amazing speed through the 1990s. In lab experiments, so called micro-electro-mechanical systems (MEMS that incorporate the entire detection-decision-actuation process on a single chip, have been batch processed in large numbers and assembled into flexible skins for gluing onto body-fluid interfaces for drag reduction purposes. Control of fluid flows span a wide variety of specialities. In Part I of this tutorial, we focus on the problem of reducing drag in channel and pipe flows by stabilizing the parabolic equilibrium profile using boundary feedback control. The control strategics used for this problem include classical control, based on the Nyquist criteria, and various optimal control techniques (H2, H-Infinity, as well as applications of Lyapunov stability theory.

  12. A Nonlinear Flow Control Scheme Under Capacity Constraints

    Institute of Scientific and Technical Information of China (English)

    Yi Fan; Zhong-Ping Jiang

    2005-01-01

    We present a nonlinear flow control scheme based on a buffer management model with physical constraints. It extends previous result of Pitsillides et al. in [6] by improving the queue length regulation for better service of network traffics. Besides a single node system, we also address the decentralized control of many cascaded nodes. The proposed discontinuous controller asymptotically regulates the buffer queue length at the output port of a router/switch to a constant reference value, under unknown time varying interfering traffics and saturation constraints on control input and states. Its continuous approximation achieves practical regulation with an ultimate bound on the regulation error tunable by a design parameter.

  13. Multilevel Flow Modelling of Process Plant for Diagnosis and Control

    DEFF Research Database (Denmark)

    Lind, Morten

    1982-01-01

    of complex systems. A model of a nuclear power plant (PWR) is presented in the paper for illustration. Due to the consistency of the method, multilevel flow models provide specifications of plant goals and functions and may be used as a basis for design of computer-based support systems for the plant...... operator. Plant control requirements can be derived from the models and due to independence of the actual controller implementation the method may be used as a basis for design of control strategies and for the allocation of control tasks to the computer and the plant operator....

  14. Flow manipulation and control methodologies for vacuum infusion processes

    Science.gov (United States)

    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

  15. Analysis and control of flows in pressurized hydraulic networks

    NARCIS (Netherlands)

    Gupta, R.K.

    2006-01-01

    Analysis, design and flow control problems in pressurized hydraulic networks such as water transmission and distribution systems consisting of pipes and other appurtenant components such as reservoirs, pumps, valves and surge devices are dealt with from the prospective of network synthesis aiming at

  16. Flow Separation Control on Airfoil With Pulsed Nanosecond Discharge Actuator

    NARCIS (Netherlands)

    Correale, G.; Popov, I.B.; Ratikin, A.E.; Starikovskii, A.Y.; Hulshoff, S.J.; Veldhuis, L.L.M.

    2011-01-01

    An experimental study of flow separation control with a nanosecond pulse plasma actuator was performed in wind-tunnel experiments. The discharge used had a pulse width of 12 ns and rising time of 3 ns with voltage up to 12 kV. Repetition frequency was adjustable up to 10 kHz. The first series of exp

  17. Control volume based modelling of compressible flow in reciprocating machines

    DEFF Research Database (Denmark)

    Andersen, Stig Kildegård; Thomsen, Per Grove; Carlsen, Henrik

    2004-01-01

    , and multidimensional effects must be calculated using empirical correlations; correlations for steady state flow can be used as an approximation. A transformation that assumes ideal gas is presented for transforming equations for masses and energies in control volumes into the corresponding pressures and temperatures...

  18. Control and optimzation of sub-surface flow

    NARCIS (Netherlands)

    Jansen, J.D.

    2013-01-01

    Controlling the flow of fluids (e.g. water, oil, natural gas or CO2) in subsurface porous media is a technical process with many mathematical challenges. The underlying physics can be described with coupled nearly-elliptic and nearly-hyperbolic nonlinear partial differential equations, which require

  19. Analysis and control of flows in pressurized hydraulic networks

    NARCIS (Netherlands)

    Gupta, R.K.

    2006-01-01

    Analysis, design and flow control problems in pressurized hydraulic networks such as water transmission and distribution systems consisting of pipes and other appurtenant components such as reservoirs, pumps, valves and surge devices are dealt with from the prospective of network synthesis aiming at

  20. Flow intake control using dry-weather forecast

    Directory of Open Access Journals (Sweden)

    O. Icke

    2017-08-01

    Full Text Available 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.

  1. Flow intake control using dry-weather forecast

    Science.gov (United States)

    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.

  2. Control Flow Analysis Can Find New Flaws Too

    DEFF Research Database (Denmark)

    Bodei, Chiara; Buchholtz, Mikael; Degano, Pierpaolo;

    2004-01-01

    A previous study showed how control flow analysis can be applied to analyse key distribution protocols based on symmetric key cryptography. We have extended both the theoretical treatment and our fully automatic verifier to deal with protocols based on asymmetric cryptography. This paper reports...

  3. Microrelief-Controlled Overland Flow Generation: Laboratory and Field Experiments

    Directory of Open Access Journals (Sweden)

    Xuefeng Chu

    2015-01-01

    Full Text Available Surface microrelief affects overland flow generation and the related hydrologic processes. However, such influences vary depending on other factors such as rainfall characteristics, soil properties, and initial soil moisture conditions. Thus, in-depth research is needed to better understand and evaluate the combined effects of these factors on overland flow dynamics. The objective of this experimental study was to examine how surface microrelief, in conjunction with the factors of rainfall, soil, and initial moisture conditions, impacts overland flow generation and runoff processes in both laboratory and field settings. A series of overland flow experiments were conducted for rough and smooth surfaces that represented distinct microtopographic characteristics and the experimental data were analyzed and compared. Across different soil types and initial moisture conditions, both laboratory and field experiments demonstrated that a rough soil surface experienced a delayed initiation of runoff and featured a stepwise threshold flow pattern due to the microrelief-controlled puddle filling-spilling-merging dynamics. It was found from the field experiments that a smooth plot surface was more responsive to rainfall variations especially during an initial rainfall event. However, enhanced capability of overland flow generation and faster puddle connectivity of a rough field plot occurred during the subsequent rain events.

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

    Science.gov (United States)

    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

  5. Peningkatan Available Transfer Capability Mengggunakan Unified Power Flow Controller

    Directory of Open Access Journals (Sweden)

    Adyatmoko Wirananto

    2012-09-01

    Full Text Available Available Transfer Capability (ATC adalah kemampuan transfer yang masih mungkin bisa dilakukan pada sistem tenaga listrik. Pemasangan perangkat FACTS, yaitu Unified Power Flow Controller (UPFC dilakukan untuk meningkatkan nilai ATC. UPFC akan mengontrol injeksi daya reaktif dan mengontrol tegangan pada saluran transmisi yang dipasangi UPFC sehingga akan merubah aliran daya pada sistem tenaga listrik. Melalui analisis optimal power flow pada Sistem IEEE 14 bus, variabel-variabel kontrol akan diinjeksikan dari UPFC ke aliran daya Sistem IEEE 14 bus. Setelah dipasang UPFC sistem mampu mencapai nilai load margin maksimal pada 0,1511 ketika UPFC dipasang di Saluran 2-5, dengan ATC yang dicapai adalah 35,38 MW.

  6. Fluidic actuators for active flow control on airframe

    Science.gov (United States)

    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.

  7. Controlling radial fingering patterns in miscible confined flows.

    Science.gov (United States)

    Chen, Ching-Yao; Huang, C-W; Wang, L-C; Miranda, José A

    2010-11-01

    Injection-driven immiscible flow in radial Hele-Shaw cells results in highly ramified patterns if the injection rate is constant in time. Likewise, time-dependent gap immiscible flow in lifting Hele-Shaw cells leads to intricate morphologies if the cell's gap width grows exponentially with time. Recent studies show that the rising of these complex fingered structures can be controlled by properly adjusting the injection rate, and the time-dependent gap width. We investigate the effectiveness of these control strategies assuming that the fluids involved are miscible. Despite the absence of surface tension effects, intensive numerical simulations support the stabilizing role of these controlling protocols. Splitting, merging and competition of fingers are all inhibited. The sensitivity of the system to changes in the initial conditions and Péclet numbers is also discussed.

  8. Nocturnal insects use optic flow for flight control.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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).

  10. Vacuum rated flow controllers for inert gas ion engines

    Science.gov (United States)

    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.

  11. Magnetically Controlled Accretion Flows onto Young Stellar Objects

    CERN Document Server

    Adams, Fred C

    2011-01-01

    (abridged) Accretion from disks onto young stars is thought to follow magnetic field lines from the inner disk edge to the stellar surface. The accretion flow thus depends on the geometry of the magnetic field. This paper extends previous work by constructing a collection of orthogonal coordinate systems, including the corresponding differential operators, where one coordinate traces the magnetic field lines. This formalism allows for an (essentially) analytic description of the geometry and the conditions required for the flow to pass through sonic points. Using this approach, we revisit the problem of magnetically controlled accretion flow in a dipole geometry, and then generalize the treatment to consider magnetic fields with multiple components, including dipole, octupole, and split monopole contributions. This approach can be generalized further to consider more complex magnetic field configurations. Observations indicate that accreting young stars have substantial dipole and octupole components, and tha...

  12. DESIGN OF SLIT DAMS FOR CONTROLLING STONY DEBRIS FLOWS

    Institute of Scientific and Technical Information of China (English)

    Hui-Pang LIEN

    2003-01-01

    A new method to a slit dam for controlling the stony debris flow has been derived based on the mass conservation law of the stony debris flow passing through a slit dam and the laboratory experiment results.This new method is then combined with three primary efficiency expressions: the dimensionless sediment outflow ratio,the sediment concentration ratio,and the sediment storage rate to develop a simple module,with which the height and the spacing of the posts,as well as the total spacing of slit dam are determined.Furthermore,these expressions can also be applied to check those slit dams that have already been constructed with their effectiveness against various magnitudes of the debris flow. The comparison between these expressions and laboratory data is in reasonable agreement.

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

    Science.gov (United States)

    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. Flow induced vibration studies on PFBR control plug components

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, V., E-mail: prakash@igcar.gov.in [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India); Kumar, P. Anup; Anandaraj, M.; Thirumalai, M.; Anandbabu, C.; Rajan, K.K. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Flow induced vibration studies on Prototype Fast Breeder Reactor control plug model carried out. Black-Right-Pointing-Pointer Velocity similitude was followed for the study. Black-Right-Pointing-Pointer Frequencies and amplitude of vibrations of various control plug components measured. Black-Right-Pointing-Pointer Overall values of vibration are well within permissible limits. - Abstract: The construction of Prototype Fast Breeder Reactor (PFBR), a 500 MWe liquid sodium cooled reactor, is in progress at Kalpakkam in India. Control plug (CP) is located right above the core subassemblies in the hot pool. Control plug is an important component as many of the critical reactor parameters are sensed and controlled by the components housed in the control plug assembly. In PFBR primary circuit, components are basically thin walled, slender shells with diameter to thickness ratio ranging from 100 to 650. These components are prone to flow induced vibrations. The existence of free liquid (sodium) surfaces, which is the source of sloshing phenomenon and the operation of primary sodium pump in the primary pool are other potential sources of vibration of reactor components. Control plug is a hollow cylindrical shell structure and provides passages and support for 12 absorber rod drive mechanisms (ARDM) which consists of 9 control and safety rods and 3 diverse safety rods, 210 thermo wells to measure the sodium temperature at the exit of various fuel subassemblies, three failed fuel localization modules (FFLM) and acoustic detectors. It consists of a core cover plate (CCP), which forms the bottom end, two intermediate supports plate, i.e. lower stay plate (LSP) and upper stay plate (USP) and an outer shell. The CCP is located at a distance of 1.3 m from the core top. With such a gap, there will be long free hanging length of the thermocouple sleeves, Delayed neutron detector (DND) sampling tubes and ARDM shroud tubes and hence they are

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

    Science.gov (United States)

    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. GAS FLOW CONTROL SYSTEM IN REACTIVE MAGNETRON SPUTTERING TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    I. M. Klimovich

    2015-01-01

    Full Text Available  It is known that the discharge parameters and the chemical composition of the particles flux impinging onto the substrate during a reactive magnetron sputtering are unstable. As a result spontaneous transitions between the «metal» mode of the target surface and the «poisoned» mode of the target surface have been observed. This leads to nonrepeatability of the coating compositions from process to process. The aim of this work is to design a gas flow control system for reactive sputtering processes. The control system allows to maintain a steady nonequilibrium state of the magnetron discharge in transition mode where the chemical state of the target surface is unstable. The intensities of spectral lines of the discharge spectrum are proposed as control parameters. Photodiode detectors were used for registration of intensities of spectral lines. A gas flow control system regulates argon and reactive gas flow automatically, using feedback signals from photodiode detectors on the intensities of the spectral lines, vacuum gauge, ion current sensor, sensors of discharge current and voltage. As an example, the process of reactive magnetron Ti-Al-N deposition is considered. The following discharge parameters are controlled during sputtering a composite target based on Ti with Al cylindrical inserts: current, voltage, total pressure of a gas mixture, substrate temperature, bias voltage and current of the substrate. Nitrogen flow was controlled by the spectral line intensity of titanium TiI 506,5 nm. The value of the line intensity is connected with the value of reactivity. Elemental composition and structure of the Ti-Al-N coatings were studied using Rutherford backscattering spectroscopy, scanning electron microscopy and X-ray diffraction. It was found, that stoichiometric Ti-Al-N coatings have a globular structure, enhanced hardness and low friction coefficient in contrast to Ti-Al-N coatings with nonstoichiometric composition, which have a

  17. Flow Instability and Its Control in Compression Systems

    Institute of Scientific and Technical Information of China (English)

    Jingyi Chen

    2003-01-01

    This paper reviews the development in the research of flow instability and its control over the recent ten or more years. This development was largely stimulated by the novel idea of active control of the aerodynamic instability in compressors. Three topics are covered in the paper, which appeared as the major themes towards the goal of stability enhancement. The first topic is the pre-stall behavior of rotating stall, which plays a vital role in designing the control scheme and discovering the convenient route to find the causal factors of flow disturbances potentially leading to stall. The second topic is the mechanism of blade passage flow during stall and its inception, which is the basic knowledge needed to manipulate the blade design for the stability improvement and eventually to predict the unsteady performance of the compressor system. The third topic is the recent trend of the control strategy based on the learning of active vs. passive methods. To introduce to the discussion of these topics, a brief description of the history of the recent development is given at the beginning of the paper. In discussing each topic, future works are also highlighted to enhance the further development of this long-standing problem in turbomachinery research and application.

  18. Controlling Compressor Vane Flow Vectoring Angles at Transonic Speeds

    Science.gov (United States)

    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.

  19. asymptotics for open-loop window flow control

    Directory of Open Access Journals (Sweden)

    Arthur W. Berger

    1994-01-01

    Full Text Available An open-loop window flow-control scheme regulates the flow into a system by allowing at most a specified window size W of flow in any interval of length L. The sliding window considers all subintervals of length L, while the jumping window considers consecutive disjoint intervals of length L. To better understand how these window control schemes perform for stationary sources, we describe for a large class of stochastic input processes the asymptotic behavior of the maximum flow in such window intervals over a time interval [0,T] as T and Lget large, with T substantially bigger than L. We use strong approximations to show that when T≫L≫logT an invariance principle holds, so that the asymptotic behavior depends on the stochastic input process only via its rate and asymptotic variability parameters. In considerable generality, the sliding and jumping windows are asymptotically equivalent. We also develop an approximate relation between the two maximum window sizes. We apply the asymptotic results to develop approximations for the means and standard deviations of the two maximum window contents. We apply computer simulation to evaluate and refine these approximations.

  20. Design of Poiseuille Flow Controllers Using the Method of Inequalities

    Institute of Scientific and Technical Information of China (English)

    John McKernan; James F.Whidborne; George Papadakis

    2009-01-01

    This paper investigates the use of the method of inequalities (MoI) to design output-feedback compensators for the problem of the control of instabilities in a laminar plane Poiseuille flow.In common with many flows,the dynamics of streamwise vortices in plane Poiseuille flow are very non-normal.Consequently,small perturbations grow rapidly with a large transient that may trigger nonlinearities and lead to turbulence even though such perturbations would,in a linear flow model,eventually decay.Such a system can be described as a conditionally linear system.The sensitivity is measured using the maximum transient energy growth,which is widely used in the fluid dynamics community.The paper considers two approaches.In the first approach,the MoI is used to design low-order proportional and proportional-integral (PI) controllers.In the second one,the MoI is combined with McFarlane and Glover's H∞ loop-shaping design procedure in a mixed-optimization approach.

  1. CFD Study of NACA 0018 Airfoil with Flow Control

    Science.gov (United States)

    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.

  2. Optimal Control of Airfoil Flow Separation using Fluidic Excitation

    Science.gov (United States)

    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

  3. Mitigation of shock-induced flow separation using magnetohydrodynamic flow control

    Indian Academy of Sciences (India)

    R BALASUBRAMANIAN; K ANANDHANARAYANAN; R KRISHNAMURTHY; DEBASIS CHAKRABORTY

    2017-03-01

    A numerical investigation is carried out to demonstrate a proof of concept, magnetohydrodynamicsbased active flow control, for mitigation of laminar flow separation over a flat plate due to shock wave–boundary layer interaction. The CERANS-MHD code has been used to solve the governing resistive magnetohydrodynamic equations discretized in finite-volume framework. The AUSM-PW? flux function is used in modellingthe advection terms and central differencing is used in modelling the resistive terms. Powell’s source term method is used for divergence cleaning of the magnetic field. The Hartmann number is varied from 0 to 12,000 to effectuate mitigation of flow separation, with the magnetic field applied at the wall and oriented transverse to the flat plate flow direction. Due to the Hartmann effect, flow separation is observed to be suppressed withincrease in Hartmann number beyond 6000. However, the overall magnitude of skin friction distribution increases drastically, resulting in large increase in skin friction drag as compared with the non-magnetic case,and is a cause of concern.

  4. Particle size control of detergents in mixed flow spray dryers

    Directory of Open Access Journals (Sweden)

    Mark Jonathan Crosby

    2015-03-01

    Full Text Available Particle size is a key quality parameter of a powder detergent as it determines its performance, the bulk density and the look and feel of the product. Consequently, it is essential that particle size is controlled to ensure the consistency of performance when comparing new formulations. The majority of study reported in the literature relating to particle size control, focuses on the spray produced by the atomisation technique. One approach advocated to achieve particle size control is the manipulation of the ratio of the mass slurry rate and mass flow rate of gas used for atomisation. Within this study, ratio control was compared with an automatic cascade loop approach using online measurements of the powder particle size on a small-scale pilot plant. It was concluded that cascade control of the mean particle size, based on manipulating the mass flow rate of gas, resulted in tighter, more responsive control. The effect of a ratio change varied with different formulations and different slurry rates. Furthermore, changes in slurry rate caused complications, as the impact on particle size growth in the dryer is non-linear and difficult to predict. The cascade loop enables further study into the effect of particle size on detergent performance.

  5. Power System Stability Enhancement Using Unified Power Flow Controller

    Directory of Open Access Journals (Sweden)

    Prechanon Kumkratug

    2010-01-01

    Full Text Available Problem statement: The enhancement of transient stability of the power system is one of the most challenging research areas in power engineer. Approach: This study presents the method to enhance transient stability of power system by Unified Power Flow Controller (UPFC. The mathematical model of power system equipped with a UPFC is systematically derived. The parameters of UPFC are modeled into power flow equation and thus it is used to determine control strategy. The swing curves of the three phase faulted power system without and with a UPFC are tested and compared in various cases. Results: The swing curve of system without a UPFC gets increases monotonically and thus the system can be considered as unstable whereas the swing curves of system with a UPFC can return to stable equilibrium point. Conclusion: From the simulation results, the UPFC can enhance transient stability of power system.

  6. Control Flow Analysis for the Pi-calculus

    DEFF Research Database (Denmark)

    Bodei, C.; Degano, P.; Nielson, Flemming;

    1998-01-01

    Control Flow Analysis is a static technique for predicting safe and computable approximations to the set of values that the objects of a program may assume during its execution. We present an analysis for the pi-calculus that shows how names will be bound to actual channels at run time. The formu......Control Flow Analysis is a static technique for predicting safe and computable approximations to the set of values that the objects of a program may assume during its execution. We present an analysis for the pi-calculus that shows how names will be bound to actual channels at run time....... The formulation of the analysis requires no extensions to the pi-calculus, except for assigning ``channels'' to the occurrences of names within restrictions, and assigning ``binders'' to the occurrences of names within input prefixes. The result of our analysis establishes a super-set of the set of names to which...

  7. Improving Advanced Inverter Control Convergence in Distribution Power Flow

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. Empirical Reduced-Order Modeling for Boundary Feedback Flow Control

    Directory of Open Access Journals (Sweden)

    Seddik M. Djouadi

    2008-01-01

    Full Text Available This paper deals with the practical and theoretical implications of model reduction for aerodynamic flow-based control problems. Various aspects of model reduction are discussed that apply to partial differential equation- (PDE- based models in general. Specifically, the proper orthogonal decomposition (POD of a high dimension system as well as frequency domain identification methods are discussed for initial model construction. Projections on the POD basis give a nonlinear Galerkin model. Then, a model reduction method based on empirical balanced truncation is developed and applied to the Galerkin model. The rationale for doing so is that linear subspace approximations to exact submanifolds associated with nonlinear controllability and observability require only standard matrix manipulations utilizing simulation/experimental data. The proposed method uses a chirp signal as input to produce the output in the eigensystem realization algorithm (ERA. This method estimates the system's Markov parameters that accurately reproduce the output. Balanced truncation is used to show that model reduction is still effective on ERA produced approximated systems. The method is applied to a prototype convective flow on obstacle geometry. An H∞ feedback flow controller is designed based on the reduced model to achieve tracking and then applied to the full-order model with excellent performance.

  9. Controlling a Linear Process in Turbulent Channel Flow

    Science.gov (United States)

    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.

  10. Stabilising falling liquid film flows using feedback control

    CERN Document Server

    Thompson, Alice B; Pavliotis, Grigorios A; Papageorgiou, Demetrios T

    2015-01-01

    The flow of a fluid layer with one interface exposed to the air and the other an inclined planar wall becomes 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 introducing deliberately spatially-varying or time-dependent perturbations via the injection and suction of fluid through the wall. We find that 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, the system can still be successfully controlled even if the feedback must be applied via a set of localised actuators, and only a small number of system observation...

  11. Numerical modelling of structural controls on fluid flow and mineralization

    Directory of Open Access Journals (Sweden)

    Yanhua Zhang

    2011-07-01

    Full Text Available This paper presents the results of a set of numerical models focussing on structural controls on hydrothermal mineralization. We first give an overview of natural phenomena of structurally-controlled ore formation and the background theory and mechanisms for such controls. We then provide the results of a group of simple 2D numerical models validated through comparison with Cu-vein structure observed near the Shilu Copper deposit (Yangchun, Guangdong Province, China and finally a case study of 3D numerical modelling applied to the Hodgkinson Province in North Queensland (Australia. Two modelling approaches, discrete deformation modelling and continuum coupled deformation and fluid flow modelling, are involved. The 2D model-derived patterns are remarkably consistent with the Cu-vein structure from the Shilu Copper deposit, and show that both modelling approaches can realistically simulate the mechanical behaviours of shear and dilatant fractures. The continuum coupled deformation and fluid flow model indicates that pattern of the Cu-veins near the Shilu deposit is the result of shear strain localization, development of dilation and fluid focussing into the dilatant fracture segments. The 3D case-study models (with deformation and fluid flow coupling on the Hodgkinson Province generated a number of potential gold mineralization targets.

  12. Electrically heated particulate filter with zoned exhaust flow control

    Science.gov (United States)

    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. Numerical model of compressible gas flow in soil pollution control

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on the theory of fluid dynamics in porous media, a numerical model of gas flow in unsaturated zone is developed with the consideration of gas density change due to variation of air pressure. This model is characterized of its wider range of availability. The accuracy of this numerical model is analyzed through comparison with modeling results by previous model with presumption of little pressure variation and the validity of this numerical model is shown. Thus it provides basis for the designing and management of landfill gas control system or soil vapor ex.action system in soil pollution control.

  14. Research on Underwater Vehicle Based on Multiphase Flow Control

    Directory of Open Access Journals (Sweden)

    Zhang Xiaoshi

    2015-01-01

    Full Text Available The commercial software ANSYS CFX is used for modeling the hydrodynamic characteristics of submarine-launched vehicle. In the numerical simulations, the SST (Shear Stress Transport turbulence model is employed to describe the turbulence phenomenon occurring in the continuous fluid. The Rayleigh-Plesset equations are applied to analyze the cavitation phenomenon. Three-dimensional numerical simulation was carried out to study the cavity shape, the surface pressure distribution and the drag force with different flow control. The result shows that the gas and the number of ventilation holes control to show any significant impact on the cavity shape and the surface pressure are effective measures to decrease resistance.

  15. Control of energy flow in residential buildings; Energieflussregelung in Wohngebaeuden

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Martin

    2011-07-01

    Energy systems in residential buildings are changing from monovalent, combustion based systems to multivalent systems containing technologies such as solar collectors, pellet boilers, heat pumps, CHP and multiple storages. Multivalent heat and electricity generation and additional storages raise the number of possible control signals in the system. This creates additional degrees of freedom regarding the choice of the energy converter and the instant of time for energy conversion. New functionality of controllers such as prioritisation of energy producers, optimization of electric self consumption and control of storages and energy feed-in are required. Within the scope of this thesis, new approaches for demand-driven optimal control of energy flows in multivalent building energy systems are developed and evaluated. The approaches are evaluated by means of system energy costs and operating emissions. For parametrisation of the controllers an easily understandable operating concept is developed. The energy flow controllers are implemented as a multi agent system (MAS) and a nonlinear model predictive controller (MPC). Proper functionality and stability are demonstrated in simulations of two example energy systems. In both example systems the MPC controller achieves less energy costs and operating emissions due to system wide global optimization and the more detailed system model within the controller. The multi agent approach turns out to perform better for systems with a huge number of components, e.g. in home automation and energy management systems. Due to the good performance of the reference control strategies, a significant reduction of energy costs and operating emissions is only possible with limitations. Systems for heat generation show only an especially low potential for optimization because of marginal variation ins heat production costs. The adaptation of the operation mode to user priorities, changing utilization characteristics and dynamic energy

  16. Dynamic control of aerodynamic forces on a moving platform using active flow control

    Science.gov (United States)

    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.

  17. P-Q decoupled control schemes using fuzzy neural networks for the unified power flow controller

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Tsao-Tsung [Department of Electrical Engineering, CEECS, National United University, 1 Lien-Da, Kung-Ching Li, MiaoLi 36003 (China)

    2007-12-15

    This paper presents a new P-Q decoupled control scheme using fuzzy neural networks for the unified power flow controller (UPFC) to improve the dynamic control performance of power systems with the aim of reducing the inevitable interactions between the real and reactive power flow control parameters. In this paper, a set of equivalent controlled current and voltage sources is adopted for mathematically modeling the UPFC and the test power systems. To simplify the theoretical analysis of the control system the 3-phase description of a two-bus test power system model embedded with a UPFC is transformed into d-q components based on a synchronously rotating reference frame. For the control systems with inherent nonlinear coupling features, a feed-forward control scheme based on fuzzy neural controllers is developed to realize the decoupling control objectives. Based on the simulation results, the proposed control scheme is able to overcome the drawbacks of the traditional power flow controllers on small disturbance linearizing method. Comprehensive simulation results on the PSCAD and MATLAB programs are presented and discussed to verify the effectiveness of the proposed control scheme. (author)

  18. INVITED PAPER: Control of sudden releases in channel flow

    Science.gov (United States)

    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.

  19. Optimal Power Flow Using Adaptive Fuzzy Logic Controllers

    Directory of Open Access Journals (Sweden)

    Abdullah M. Abusorrah

    2013-01-01

    Full Text Available This paper presents an approach for optimum reactive power dispatch through the power network with flexible AC transmission systems (FACTSs devices, using adaptive fuzzy logic controller (AFLC driven by adaptive fuzzy sets (AFSs. The membership functions of AFLC are optimized based on 2nd-order fuzzy set specifications. The operation of FACTS devices (particularly, static VAR compensator (SVC and the setting of their control parameters (QSVC are optimized dynamically based on the proposed AFLC to enhance the power system stability in addition to their main function of power flow control. The proposed AFLC is compared with a static fuzzy logic controller (SFLC, driven by a fixed fuzzy set (FFS. Simulation studies were carried out and validated on the standard IEEE 30-bus test system.

  20. Photovoltaic Inverter Controllers Seeking AC Optimal Power Flow Solutions

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Neural Network Predictive Control for Vanadium Redox Flow Battery

    Directory of Open Access Journals (Sweden)

    Hai-Feng Shen

    2013-01-01

    Full Text Available The vanadium redox flow battery (VRB is a nonlinear system with unknown dynamics and disturbances. The flowrate of the electrolyte is an important control mechanism in the operation of a VRB system. Too low or too high flowrate is unfavorable for the safety and performance of VRB. This paper presents a neural network predictive control scheme to enhance the overall performance of the battery. A radial basis function (RBF network is employed to approximate the dynamics of the VRB system. The genetic algorithm (GA is used to obtain the optimum initial values of the RBF network parameters. The gradient descent algorithm is used to optimize the objective function of the predictive controller. Compared with the constant flowrate, the simulation results show that the flowrate optimized by neural network predictive controller can increase the power delivered by the battery during the discharge and decrease the power consumed during the charge.

  2. Application of Active Flow Control Technique for Gust Load Alleviation

    Institute of Scientific and Technical Information of China (English)

    XU Xiaoping; ZHU Xiaoping; ZHOU Zhou; FAN Ruijun

    2011-01-01

    A new gust load alleviation technique is presented in this paper based on active flow control.Numerical studies are conducted to investigate the beneficial effects on the aerodynamic characteristics of the quasi “Global Hawk” airfoil using arrays of jets during the gust process.Based on unsteady Navier-Stokes equations,the grid-velocity method is introduced to simulate the gust influence,and dynamic response in vertical gust flow perturbation is investigated for the airfoil as well.An unsteady surface transpiration boundary condition is enforced over a user specified portion of the airfoil's surface to emulate the time dependent velocity boundary conditions.Firstly,after applying this method to simulate typical NACA0006 airfoil gust response to a step change in the angle of attack,it shows that the indicial responses of the airfoil make good agreement with the exact theoretical values and the calculated values in references.Furthermore,gust response characteristic for the quasi “Global Hawk” airfoil is analyzed.Five kinds of flow control techniques are introduced as steady blowing,steady suction,unsteady blowing,unsteady suction and synthetic jets.The physical analysis of the influence on the effects of gust load alleviation is proposed to provide some guidelines for practice.Numerical results have indicated that active flow control technique,as a new technology of gust load alleviation,can affect and suppress the fluid disturbances caused by gust so as to achieve the purpose of gust load alleviation.

  3. PWM Flow Rate Control of ER Valve and its Application to ER Actuator Control

    Science.gov (United States)

    Nakano, Masami; Minagawa, Shuji; Hagino, Katsuya

    The PWM (Pulse Width Modulation) control of ER valve consisting of two parallel electrodes has been investigated to continuously control the flow rate of an electrorheological (ER) suspension containing sulfonated polymer particles in silicone oil. PWM wave voltages are applied to the electrodes of the ER valve. It is possible to control continuously the flow rate by changing the duty ratio of the PWM wave from 1 to 0, where the duty ratio of 1 corresponds to the state to stop the flow. A miniature bellows actuator driven by a pair of PWM controlled ER valves has been developed, and the control characteristics of the actuator have been investigated. The duty ratios of both ER valves have been proposed to be changed alternately in proportion to the control voltage V to control the flow rate into and out of the bellows chamber, and also an overlap duty ratio Dov at V=0V has been introduced. The introduction of the overlap duty ratio Dov was found to be very important to smoothly control the actuator and to improve the control performance.

  4. Non-Markovian quantum feedback networks II: Controlled flows

    Science.gov (United States)

    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.

  5. Downhole water flow controller for aquifer storage recovery wells

    Energy Technology Data Exchange (ETDEWEB)

    Pyne, R.D.

    1987-09-08

    This patent describes a downhole flow control device for continuous automatic control of water flowing into or out of wells, aquifers and the like through pipe columns. The upper end of the first tubular member is mounted to the pipe column so as to be in fluid communication therewith. The lower end of the first tubular member is substantially closed. A second tubular member is mounted concentrically within and proximate to the first tubular member and has an open upper end and side walls and a substantially closed lower end. First openings are spaced in vertical relationship to the second openings. Third openings are through the second tubular member. The second tubular member is vertically movable with respect to the first tubular member so as to selectively align the third openings with either of the first and second openings. Biasing means are located between the lower ends of the first and second tubular members for normally urging the second tubular member vertically upward with respect to the first tubular member. The biasing means are yieldable upon the introduction of water into the pump column to permit the second tubular member to be vertically displaced relative to the first tubular member to thereby close the third openings with respect to the first or second openings. The third openings align with one of the first and second openings dependent upon the direction of fluid flow within the pipe column.

  6. Feedback control of flow alignment in sheared liquid crystals.

    Science.gov (United States)

    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.

  7. Control algorithm for multiscale flow simulations of water

    DEFF Research Database (Denmark)

    Kotsalis, E. M.; Walther, Jens Honore; Kaxiras, E.

    2009-01-01

    . 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......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...... 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....

  8. Control algorithm for multiscale flow simulations of water

    Science.gov (United States)

    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.

  9. Cerebral autoregulation control of blood flow in the brain

    CERN Document Server

    Payne, Stephen

    2016-01-01

    This Brief provides a comprehensive introduction to the control of blood flow in the brain. Beginning with the basic physiology of autoregulation, the author goes on to discuss measurement techniques, mathematical models, methods of analysis, and relevant clinical conditions, all within this single volume. The author draws together this disparate field, and lays the groundwork for future research directions. The text gives an up-to-date review of the state of the art in cerebral autoregulation, which is particularly relevant as cerebral autoregulation moves from the laboratory to the bedside. Cerebral Autoregulation will be useful to researchers in the physical sciences such as mathematical biology, medical physics, and biomedical engineering whose work is concerned with the brain. Researchers in the medical sciences and clinicians dealing with the brain and blood flow, as well as industry professionals developing techniques such as ultrasound, MRI, and CT will also find this Brief of interest.

  10. Intracycle Angular Velocity Control of Cross-Flow Turbines

    CERN Document Server

    Strom, Benjamin; Polagye, Brian

    2016-01-01

    Cross-flow turbines, also known as vertical-axis turbines, have numerous features that make them attractive for wind and marine renewable energy. To maximize power output, the turbine blade kinematics may be controlled during the course of the blade revolution, thus optimizing the unsteady fluid dynamic forces. Dynamically pitching the blades, similar to blade control in a helicopter, is an established method. However, this technique adds undesirable mechanical complexity to the turbine, increasing cost and reducing durability. Here we introduce a novel alternative requiring no additional moving parts: we optimize the turbine rotation rate as a function of blade position resulting in motion (including changes in the effective angle of attack) that is precisely timed to exploit unsteady fluid effects. We demonstrate experimentally that this approach results in a 79% increase in power output over industry standard control methods. Analysis of the fluid forcing and blade kinematics show that maximal power is ach...

  11. Computing an operating parameter of a unified power flow controller

    Science.gov (United States)

    Wilson, David G; Robinett, III, Rush D

    2015-01-06

    A Unified Power Flow Controller described herein comprises a sensor that outputs at least one sensed condition, a processor that receives the at least one sensed condition, a memory that comprises control logic that is executable by the processor; and power electronics that comprise power storage, wherein the processor causes the power electronics to selectively cause the power storage to act as one of a power generator or a load based at least in part upon the at least one sensed condition output by the sensor and the control logic, and wherein at least one operating parameter of the power electronics is designed to facilitate maximal transmittal of electrical power generated at a variable power generation system to a grid system while meeting power constraints set forth by the electrical power grid.

  12. Unified power flow controller: modeling and dynamic characteristic

    Science.gov (United States)

    Bach, D. H.; Loc, H. D.

    2005-12-01

    Unified power flow controller (UPFC) consists two converters. There are three purposes of this paper, firstly to illustrate the UPFC device based VSC designs, then to describe a decoupling method the UPFC's controller into two separate control systems of the shunt and the series converters respectively in realizing an appropriate coordination between them. Finally, using the Matlab tool to build a discrete simulator for the UPFC with 12 pulse converters. The simulation results show that the developed UPFC model is reflected the static and dynamic characteristics of the UPFC. The harmonics of the output of the model were analyzed. Using the simple power system with UPFC as an example, the dynamics characteristics were studied. The fault status of the system with UPFC was analyzed too.

  13. Speed limit and ramp meter control for traffic flow networks

    Science.gov (United States)

    Goatin, Paola; Göttlich, Simone; Kolb, Oliver

    2016-07-01

    The control of traffic flow can be related to different applications. In this work, a method to manage variable speed limits combined with coordinated ramp metering within the framework of the Lighthill-Whitham-Richards (LWR) network model is introduced. Following a 'first-discretize-then-optimize' approach, the first order optimality system is derived and the switch of speeds at certain fixed points in time is explained, together with the boundary control for the ramp metering. Sequential quadratic programming methods are used to solve the control problem numerically. For application purposes, experimental setups are presented wherein variable speed limits are used as a traffic guidance system to avoid traffic jams on highway interchanges and on-ramps.

  14. Multiphase flow dynamics and control; Dynamique et controle des ecoulements polyphasiques

    Energy Technology Data Exchange (ETDEWEB)

    Duret, E.

    2005-02-01

    Production in the petroleum industry requires a better knowledge of multiphase flow, as the design of pipelines may cause the flow to become strongly unstable. For instance, for low flow rates and when a sea line ends at a riser, the riser base may accumulate liquid and stop the flow of gas. Then, the upstream gas is compressed until its pressure is large enough to push the liquid slug downstream. Under such conditions, a cyclic process occurs which is called severe slugging, generating large and fast fluctuations in pressure and flow rates. This thesis is devoted to two methods to stabilize this undesirable phenomenon. Using the pipeline's ability to separate phases to pick-up the gas upstream the riser base, they are mainly based on the perturbation theory (fast proportional effect, slow integral effect). The first one uses a secondary riser to transport the gas to the surface facilities. A stability study worked out with the phase diagrams technique shows that it is a good method to control this phenomenon. However, it imposes a high pressure in all the system. Thus, the second controller re-injects the gas at a determined height in the riser to decrease the hydrostatic pressure. A first stability study in open loop give a criterion on the minimal reinjection height. Then, the controller is developed by using the two-time scale control techniques. Finally, let us denote that these two controllers have been validated with a small size experimental set up. (author)

  15. Orifice plate for controlling solids flow, methods of use thereof and articles comprising the same

    Energy Technology Data Exchange (ETDEWEB)

    Jukkola, Glen D.; Teigen, Bard C.

    2017-01-31

    Disclosed herein is an orifice plate comprising one or more plates having orifices disposed therein; the orifices being operative to permit the flow of solids from a moving bed heat exchanger to a solids flow control system; where the orifice plate is downstream of a tube bundle of the moving bed heat exchanger and upstream of the solids flow control system and wherein the orifice plate is operative to evenly distribute the flow of solids in the solids flow control system.

  16. The aerodynamic performance of several flow control devices for internal flow systems

    Science.gov (United States)

    Eckert, W. T.; Wettlaufer, B. M.; Mort, K. W.

    1982-01-01

    An experimental reseach and development program was undertaken to develop and document new flow-control devices for use in the major modifications to the 40 by 80 Foot wind tunnel at Ames Research Center. These devices, which are applicable to other facilities as well, included grid-type and quasi-two-dimensional flow straighteners, louver panels for valving, and turning-vane cascades with net turning angles from 0 deg to 90 deg. The tests were conducted at model scale over a Reynolds number range from 2 x 100,000 to 17 x 100,000, based on chord. The results showed quantitatively the performance benefits of faired, low-blockage, smooth-surface straightener systems, and the advantages of curved turning-vanes with hinge-line gaps sealed and a preferred chord-to-gap ratio between 2.5 and 3.0 for 45 deg or 90 deg turns.

  17. Comparison between PI and PID controllers used in UPFC control for power flow

    Energy Technology Data Exchange (ETDEWEB)

    Aghdam, Hossein Nasir [Department of Electrical Engineering, Ahar Branch, Islamic Azad University, Ahar (Iran, Islamic Republic of); email: h_nasir@iau-ahar.ac.ir; Kaheh, Meghdad [Department of Electrical Engineering, Majlesi Branch, Islamic Azad University, Majlesi (Iran, Islamic Republic of); email: kaheh.meghdad@gmail.com; Najafi, Babak [Department of Electrical Engineering, Germi Branch, Islamic Azad University, Germi (Iran, Islamic Republic of); email: ba.najafi@gmail.com4; Farhadi, Payam; Karimi, Mohammad [Department of Electrical Engineering, Parsabad Moghan Branch, Islamic Azad University, Young Researchers Club, Parsabad Moghan (Iran, Islamic Republic of); email: pfarhadi@iaupmogan.ac.ir; Karimi, Mohammad, email: mohammadkarimi62@gmail.com

    2011-07-01

    This paper compares features of PI and PID Controllers, the two most frequently used unified power flow controllers (UPFC) in transmission lines. These are Flexible AC Transmission Systems devices (FACTS) which are used in general to control the power flow and damp oscillations of power systems. These features enhance the capacity of existing transmission systems to carry energy, obviating the need to build new transmission lines while at the same time respecting safety, environmental, and economic constraints. The growing demand for energy has put pressure on the industry to develop appropriate methods for augmenting the efficacity and reliability of systems while operating within their various limitations. In conclusion, it was demonstrated that the PI controller response is better for power system stability but that in reactive power control the PI and PID controllers have similar performance. The efficiency of the UPFCs was also demonstrated using MATLAB/SIMULINK software.

  18. Experimental validation of tonal noise control from subsonic axial fans using flow control obstructions

    Science.gov (United States)

    Gérard, Anthony; Berry, Alain; Masson, Patrice; Gervais, Yves

    2009-03-01

    This paper presents the acoustic performance of a novel approach for the passive adaptive control of tonal noise radiated from subsonic fans. Tonal noise originates from non-uniform flow that causes circumferentially varying blade forces and gives rise to a considerably larger radiated dipolar sound at the blade passage frequency (BPF) and its harmonics compared to the tonal noise generated by a uniform flow. The approach presented in this paper uses obstructions in the flow to destructively interfere with the primary tonal noise arising from various flow conditions. The acoustic radiation of the obstructions is first demonstrated experimentally. Indirect on-axis acoustic measurements are used to validate the analytical prediction of the circumferential spectrum of the blade unsteady lift and related indicators generated by the trapezoidal and sinusoidal obstructions presented in Ref. [A. Gérard, A. Berry, P. Masson, Y. Gervais, Modelling of tonal noise control from subsonic axial fans using flow control obstructions, Journal of Sound and Vibration (2008), this issue, doi: 10.1016/j.jsv.2008.09.027.] and also by cylindrical obstructions used in the literature. The directivity and sound power attenuation are then given in free field for the control of the BPF tone generated by rotor/outlet guide vane (OGV) interaction and the control of an amplified BPF tone generated by the rotor/OGV interaction with an added triangular obstruction between two outlet guide vanes to enhance the primary non-uniform flow. Global control was demonstrated in free field, attenuation up to 8.4 dB of the acoustic power at BPF has been measured. Finally, the aerodynamic performances of the automotive fan used in this study are almost not affected by the presence of the control obstruction.

  19. Aircraft energy efficiency laminar flow control wing design study

    Science.gov (United States)

    Bonner, T. F., Jr.; Pride, J. D., Jr.; Fernald, W. W.

    1977-01-01

    An engineering design study was performed in which laminar flow control (LFC) was integrated into the wing of a commercial passenger transport aircraft. A baseline aircraft configuration was selected and the wing geometry was defined. The LFC system, with suction slots, ducting, and suction pumps was integrated with the wing structure. The use of standard aluminum technology and advanced superplastic formed diffusion bonded titanium technology was evaluated. The results of the design study show that the LFC system can be integrated with the wing structure to provide a structurally and aerodynamically efficient wing for a commercial transport aircraft.

  20. An instrument to control parallel plate separation for nanoscale flow control

    Science.gov (United States)

    White, J.; Ma, H.; Lang, J.; Slocum, A.

    2003-11-01

    The handling of extremely small samples of gases and liquids has long been a subject of research among biologists, chemists, and engineers. A few scientific instruments, notably the surface force apparatus, have been used extensively to investigate very short-range molecular phenomena. This article describes the design, fabrication, and characterization of an easily manufactured, gas and liquid flow control device called the Nanogate. The Nanogate controls liquid flows under very high planar confinement, wherein the liquid film is, in one dimension, on the scale of nanometers, but is on the scale of hundreds of microns in its other dimensions. The liquid film is confined between a silica (Pyrex) surface with a typical roughness of Ra≈6 nm and a gold-covered silicon surface with a typical roughness of Ra≈2 nm. During the manufacturing process, the Pyrex flows and conforms to the gold-covered silicon surface, improving the mating properties of the two surfaces. The fluid film thickness can be controlled within 2 Å, from sub-10 nm up to 1 μm. Control of helium gas flow rates in the 10-9 atm cm3/s range, and sub-nl/s flow rates of water and methanol have been predicted and experimentally verified.

  1. Investigation of cyanobacteria in a controlled hyperbolic straining flow

    Science.gov (United States)

    Akbaridoust, Farzan; Philip, Jimmy; Marusic, Ivan

    2016-11-01

    Here we report a systematic study on the effect of straining flow on cyanobacteria, which are a cause of significant water contamination issues worldwide. We focus on the species Anaebena Circinalis. A micro-cross channel equipped with two online computer-controlled on-chip membrane valves was designed and fabricated using standard soft-lithography. The device produces a hyperbolic straining flow on a micron-scaled region similar to G. I. Taylor's four-roll mill at larger scale. It was used to investigate the behaviour of a single filament of cynobacteria in a crowded medium under an increasing uniform strain rate flow. The velocity field and the resulting uniform strain-rate was measured in the absence of bacteria filaments using micro-PIV. A large number of single filaments of bacteria were trapped and exposed to stain-rates over 2 to 15 s-1. Previous studies have reported anecdotal evidence of suspected mechanical damage to Anaebena Circinalis for strain rates considerably lower than the maximum values studied here. In our case, no mechanical damage was observed. This work was performed in part at the Melbourne Centre for Nanofabrication (MCN) in the Victorian Node of the Australian National Fabrication Facility (ANFF).

  2. Using a pressure controlled vortex design method to control secondary flow losses in a turbine stage

    Institute of Scientific and Technical Information of China (English)

    Deng Qingfeng; Zheng Qun; Yue Guoqiang; Zhang Hai; Luo Mingcong

    2013-01-01

    A turbine design method based on pressure controlled vortex design (PCVD) is presented to design a small-size turbine stage. Contrary to the conventional controlled vortex design (CVD) method, the main objective of PCVD is to control the axial velocity and radial pressure in the sta-tor-rotor gap. Through controlling axial velocity, the PCVD establishes a direct tie to meridional stream surface. Thus stream surface variation is induced, resulting in a large secondary flow vortex covering the full blade passage in the respective stator and rotor. This secondary flow vortex could be dedicated to control the secondary flow mitigation and migration. Through radial pressure, the PCVD is also associated with the macroscopic driving force of fluid motion. So the better benefit of CVD can be achieved. The core concept behind PCVD is to mainly control the spanwise pressure gradient by altering profile loading at various spanwise locations. Therefore not only the local pro-file lift is affected, but also the resulting throat widths, stage reaction degree, and massflow rate are altered or redistributed respectively. With the PCVD method, the global stage efficiency is increased successfully while the mass flow rate keeps constant. Additionally there is no endwall shape optimi-zation, stacking optimization, or pitch/chord variations, concentrating solely on varying blade pro-file deflections and stagger.

  3. Ferrofluid magnetoviscous control of wall flow channeling in porous media

    Institute of Scientific and Technical Information of China (English)

    Faal; Larachi

    2007-01-01

    [1]Bacri,J.C.,Perzynski,R.,Shliomis,M.I.,& Burde,G.I.(1995).Negative viscosity effect in a magnetic fluid.Physical Review Letters,75(11),2128-2131.[2]Felderhof,B.U.(2001).Flow of a ferrofluid down a tube in an oscillating magnetic field.Physical Review E,64(021508),1-7.[3]Khuzir,P.,Bossis,G.,Bashtovoi,V.,& Volkova,O.(2003).Flow of magnetorheological fluid through porous media.European Journal of Mechanics B/Fluids,22,331-343.[4]McTague,J.P.(1969).Magnetoviscosity of magnetic colloids.Journal of Chemical Physics,51,133-136.[5]Odenbach,S.(2003).Magnetic fluids-Suspensions of magnetic dipoles and their magnetic control.Journal of Physics:Condensed Matter,15,S 1497-S1508.[6]Rinaldi,C.,& Zahn,M.(2002).Effects of spin viscosity on ferrofluid flow profiles in alternating and rotating magnetic fields.Physics of Fluids,14,2847-2870.[7]Rosensweig,R.E.(1997).Ferrohydrodynamics.New York:Dover Publications.[8]Schumacher,K.R.,Sellien,I.,Knoke,G.S.,Cadet,T.,& Finlayson,B.A.(2003).Experiment and simulation of laminar and turbulent ferrofluid pipe flow in an oscillating magnetic field.Physical Review E,67(026308),1-11.[9]Shliomis,M.I.(1972).Effective viscosity of magnetic suspensions.Soviet Physics JETP,34,1291-1294.[10]Whitaker,S.(1999).Theory and applications of transport in porous media.Dordrecht:Kluwer Academic Press.[11]Zeuner,A.,Richter,R.,& Rehberg,I.(1998).Experiments on negative and positive magnetoviscosity in an alternating magnetic field.Physical Review E,58,62876293.

  4. A Numerical Investigation of Controllably Flexible Hydrofoil in Laminar Flows

    Science.gov (United States)

    He, G. Y.; Zhang, X.; Zhang, S. G.; He, G. W.

    Aquatic animals, such as fishes, whales, seals and penguins, are naturally born to be flexible and deformable, which promise their effective locomotion through water. They are able to produce hydrodynamic thrust by active control of their body configurations. That is, the aquatic animals could wiggle their flexible bodies at an appropriate frequency and amplitude suitable to the hydrodynamics surrounding them. However, the mechanism for the active controls has not been adequately understood yet and attracts current research. One obstacle which hinders such investigation is the difficulty in experimental measurements of the flows around the wiggling bodies, and thus numerical simulation is becoming an indispensable alternative. In the paper, an immersed boundary method is developed to simulate the NACA 65-10 hydrofoil. It is observed that a wiggling hydrofoil exhibits a higher thrust while a stationary hydrofoil offers little improvement.

  5. Melt Flow Control in the Directional Solidification of Binary Alloys

    Science.gov (United States)

    Zabaras, Nicholas

    2003-01-01

    Our main project objectives are to develop computational techniques based on inverse problem theory that can be used to design directional solidification processes that lead to desired temperature gradient and growth conditions at the freezing front at various levels of gravity. It is known that control of these conditions plays a significant role in the selection of the form and scale of the obtained solidification microstructures. Emphasis is given on the control of the effects of various melt flow mechanisms on the local to the solidification front conditions. The thermal boundary conditions (furnace design) as well as the magnitude and direction of an externally applied magnetic field are the main design variables. We will highlight computational design models for sharp front solidification models and briefly discuss work in progress toward the development of design techniques for multi-phase volume-averaging based solidification models.

  6. Stability analysis of traffic flow with extended CACC control models

    Science.gov (United States)

    Ya-Zhou, Zheng; Rong-Jun, Cheng; Siu-Ming, Lo; Hong-Xia, Ge

    2016-06-01

    To further investigate car-following behaviors in the cooperative adaptive cruise control (CACC) strategy, a comprehensive control system which can handle three traffic conditions to guarantee driving efficiency and safety is designed by using three CACC models. In this control system, some vital comprehensive information, such as multiple preceding cars’ speed differences and headway, variable safety distance (VSD) and time-delay effect on the traffic current and the jamming transition have been investigated via analytical or numerical methods. Local and string stability criterion for the velocity control (VC) model and gap control (GC) model are derived via linear stability theory. Numerical simulations are conducted to study the performance of the simulated traffic flow. The simulation results show that the VC model and GC model can improve driving efficiency and suppress traffic congestion. Project supported by the National Natural Science Foundation of China (Grant Nos. 71571107 and 11302110). The Scientific Research Fund of Zhejiang Province, China (Grant Nos. LY15A020007, LY15E080013, and LY16G010003). The Natural Science Foundation of Ningbo City (Grant Nos. 2014A610030 and 2015A610299), the Fund from the Government of the Hong Kong Administrative Region, China (Grant No. CityU11209614), and the K C Wong Magna Fund in Ningbo University, China.

  7. Dynamic Flow Control Strategies of Vehicle SCR Urea Dosing System

    Institute of Scientific and Technical Information of China (English)

    LIN Wei; ZHANG Youtong; ASIF Malik

    2015-01-01

    Selective Catalyst Reduction(SCR) Urea Dosing System(UDS) directly affects the system accuracy and the dynamic response performance of a vehicle. However, the UDS dynamic response is hard to keep up with the changes of the engine’s operating conditions. That will lead to low NOX conversion efficiency or NH3 slip. In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions, an advanced control strategy based on an air-assisted volumetric UDS is presented. It covers the methods of flow compensation and switching working conditions. The strategy is authenticated on an UDS and tested in different dynamic conditions. The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS. The inject deviation range is improved from being between–8%and 10%to–4%and 2%and became more stable than before, and the dynamic response time was shortened from 200 ms to 150 ms . The ETC cycle result shows that after using the new strategy the NH3 emission is reduced by 60%, and the NOX emission remains almost unchanged. The trade-off between NOX conversion efficiency and NH3 slip is mitigated. The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine’s operating conditions quickly.

  8. Provably correct control flow graphs from Java bytecode programs with exceptions

    NARCIS (Netherlands)

    Amighi, A.; de Carvalho Gomes, Pedro; Gurov, Dilian; Huisman, Marieke

    We present an algorithm for extracting control flow graphs from Java bytecode that captures normal as well as exceptional control flow. We prove its correctness, in the sense that the behaviour of the extracted control flow graph is a sound over-approximation of the behaviour of the original

  9. Development of digital flow control system for multi-channel variable-rate sprayers

    Science.gov (United States)

    Precision modulation of nozzle flow rates is a critical step for variable-rate spray applications in orchards and ornamental nurseries. An automatic flow rate control system activated with microprocessors and pulse width modulation (PWM) controlled solenoid valves was developed to control flow rates...

  10. Exploring active flow control for efficient control of separation on an Ahmed model

    Science.gov (United States)

    McNally, Jonathan; Alvi, Farrukh

    2016-11-01

    Active flow control is applied to an Ahmed model with a rear slant angle of 25°, where a typical flow field consists of a three-dimensional separation region on the rear slant of the bluff body. Linear arrays of discrete microjets, previously proven to effectively control this separation, are investigated further. A principal aim of this experimental study is to examine the sensitivity of control as the actuator location is shifted with respect to the separation location. Aerodynamic force and surface pressure measurements, combined with the velocity field obtained using particle image velocimetry, provide a measure of control efficacy and insight into the interaction of jet arrays with the local flow field, including the separating shear layer. An energy balance is conducted to characterize control efficiency for multiple positions over a range of microjet array blowing conditions. Results show that moving the actuator array further into the separation region requires higher microjet momentum to obtain a desired aerodynamic benefit. An empirical relationship is also developed for determining the required jet velocity as a function of position by relating the jet penetration distance to local flow features and length scales. Partial support by FCAAP and NSF.

  11. Control algorithms for control of real and reactive power flows and power oscillation damping using UPFC

    Energy Technology Data Exchange (ETDEWEB)

    Ilango, G. Saravana; Nagamani, C.; Sai, A.V.S.S.R.; Aravindan, D. [Department of Electrical and Electronics Engineering, National Institute of Technology, Tiruchirappalli 620015, Tamil Nadu (India)

    2009-04-15

    This paper investigates the application of multivariable control technique to multi-input multi-output (MIMO) non-linear problem of a power transmission system with UPFC. The main objective is to achieve effective independent control of real and reactive power flows with zero dynamic interactions. Towards achieving the objective, feed-back linearization control (FBLC) scheme is implemented in the laboratory for the control of UPFC. A two-bus power system with UPFC has been built in laboratory and the control implementation has been carried out using DSP TMS320LF2407A. Both power flow control and power oscillation damping issues are addressed. The excellent correlation between simulation and experimental results using a laboratory test system establish the validity of the proposed scheme. Although the power stage of the developed laboratory system is a scaled down model and has limited ratings, the FBLC controller can be used equally effectively in a more realistic system set up by appropriate scaling factors for the fed-back signals of currents and voltages and for initiating the inverter voltages. The proposed controller enables UPFC to independently control the real and reactive power with absolute decoupling. Also it is found that the overall performance of the system with the proposed controller is far superior to that using conventional cascade PI control structure. (author)

  12. Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics

    Science.gov (United States)

    LaGraff, John E.; Povinelli, Louis A.; Gostelow, J. Paul; Glauser, Mark

    2010-01-01

    Topics covered include: Flow Physics and control for Internal and External Aerodynamics (not in TOC...starts on pg13); Breaking CFD Bottlenecks in Gas-Turbine Flow-Path Design; Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading; DNS and Embedded DNS as Tools for Investigating Unsteady Heat Transfer Phenomena in Turbines; Cavitation, Flow Structure and Turbulence in the Tip Region of a Rotor Blade; Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows; Active Flow Control of Lifting Surface With Flap-Current Activities and Future Directions; Closed-Loop Control of Vortex Formation in Separated Flows; Global Instability on Laminar Separation Bubbles-Revisited; Very Large-Scale Motions in Smooth and Rough Wall Boundary Layers; Instability of a Supersonic Boundary-Layer With Localized Roughness; Active Control of Open Cavities; Amplitude Scaling of Active Separation Control; U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities; Some Issues Related to Integrating Active Flow Control With Flight Control; Active Flow Control Strategies Using Surface Pressure Measurements; Reduction of Unsteady Forcing in a Vaned, Contra-Rotating Transonic Turbine Configuration; Active Flow Control Stator With Coanda Surface; Controlling Separation in Turbomachines; Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets; Reduced Order Modeling Incompressible Flows; Study and Control of Flow Past Disk, and Circular and Rectangular Cylinders Aligned in the Flow; Periodic Forcing of a Turbulent Axisymmetric Wake; Control of Vortex Breakdown in Critical Swirl Regime Using Azimuthal Forcing; External and Turbomachinery Flow Control Working Group; Boundary Layers, Transitions and Separation; Efficiency Considerations in Low Pressure Turbines; Summary of Conference; and Final Plenary Session

  13. Analysis of Cisco Open Network Environment (ONE) OpenFlow Controller Implementation

    Science.gov (United States)

    2014-08-01

    or match criteria to ports that are not connected) as well as the ability to install and uninstall a flow from switches without deleting it entirely...Port recognition Not explicit Yes Install/ uninstall flows NA Yes Set dynamic flows Requires code manipulation Yes 6 5.2 OpenFlow Control Channel...Setup The initial handshake between the controller and switch was monitored using packet analysis tools capable of understanding OpenFlow protocol

  14. Backbone of complex networks of corporations: The flow of control

    Science.gov (United States)

    Glattfelder, J. B.; Battiston, S.

    2009-09-01

    We present a methodology to extract the backbone of complex networks based on the weight and direction of links, as well as on nontopological properties of nodes. We show how the methodology can be applied in general to networks in which mass or energy is flowing along the links. In particular, the procedure enables us to address important questions in economics, namely, how control and wealth are structured and concentrated across national markets. We report on the first cross-country investigation of ownership networks, focusing on the stock markets of 48 countries around the world. On the one hand, our analysis confirms results expected on the basis of the literature on corporate control, namely, that in Anglo-Saxon countries control tends to be dispersed among numerous shareholders. On the other hand, it also reveals that in the same countries, control is found to be highly concentrated at the global level, namely, lying in the hands of very few important shareholders. Interestingly, the exact opposite is observed for European countries. These results have previously not been reported as they are not observable without the kind of network analysis developed here.

  15. Backbone of complex networks of corporations: the flow of control.

    Science.gov (United States)

    Glattfelder, J B; Battiston, S

    2009-09-01

    We present a methodology to extract the backbone of complex networks based on the weight and direction of links, as well as on nontopological properties of nodes. We show how the methodology can be applied in general to networks in which mass or energy is flowing along the links. In particular, the procedure enables us to address important questions in economics, namely, how control and wealth are structured and concentrated across national markets. We report on the first cross-country investigation of ownership networks, focusing on the stock markets of 48 countries around the world. On the one hand, our analysis confirms results expected on the basis of the literature on corporate control, namely, that in Anglo-Saxon countries control tends to be dispersed among numerous shareholders. On the other hand, it also reveals that in the same countries, control is found to be highly concentrated at the global level, namely, lying in the hands of very few important shareholders. Interestingly, the exact opposite is observed for European countries. These results have previously not been reported as they are not observable without the kind of network analysis developed here.

  16. Dielectric barrier discharge plasma actuator for flow control

    Science.gov (United States)

    Opaits, Dmitry Florievich

    Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness in separation control, acoustic noise reduction, and other aeronautic applications. In contrast to conventional DBD actuators driven by sinusoidal voltages, we proposed and used a voltage profile consisting of nanosecond pulses superimposed on dc bias voltage. This produces what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. Experimental studies were conducted of a flow induced in a quiescent room air by a single DBD actuator. A new approach for non-intrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low

  17. Minimal sensor count approach to fuzzy logic rotary blood pump flow control.

    Science.gov (United States)

    Casas, Fernando; Ahmed, Nisar; Reeves, Andrew

    2007-01-01

    A rotary blood pump fuzzy logic flow controller without flow sensors was developed and tested in vitro. The controller, implemented in LabView, was set to maintain a flow set point in the presence of external pressure disturbances. Flow was estimated as a function of measured pump's delta P and speed, using a steady-state, nonlinear approximation. The fuzzy controller used the pump's flow estimate and delta P as feedback variables. The defuzzified control output manipulated the pump speed. Membership functions included flow error, delta P, and pump speed. Experimental runs in a mock loop (water/glycerin 3.5 cPs, 37 degrees C), using the estimated flow, were compared with those using a Transonic flow meter for nine conditions of flow and delta P (4 to 6 L/min, 150 to 350 mm Hg). Pressure disturbances generated by a servo pinch valve ranged from +/-23 to +/-47 mm Hg. Results indicated that the fuzzy controller ably regulated the flow set point to within +/-10% of the baseline even under large swings in pressure. There was no difference in controller performance between the ultrasonic flow measurement and the estimated flow calculation scenarios. These tests demonstrated that the fuzzy controller is capable of rejecting disturbances and regulating flow to acceptable limits while using a flow estimate.

  18. Power flow control and voltage stability limit: regulating transformer versus UPFC

    Energy Technology Data Exchange (ETDEWEB)

    Haque, M.H. [Nanyang Technological Univ., Center for Advanced Power Electronics, Nanyang (Singapore)

    2004-05-01

    Power flow through an AC transmission line can be controlled by injecting an adjustable compensating voltage in series with the line. This paper evaluates and compares the power flow control ranges of a simple system obtained by injecting an adjustable series compensating voltage produced by a regulating transformer and unified power flow controller. The static voltage stability limits of the system with a regulating transformer and unified power flow controller are also determined and compared. In evaluating the power flow control ranges and voltage stability limits, the transmission line of the system is modelled in four different ways. The results obtained for various line models are also compared. (Author)

  19. An Intelligent Traffic Flow Control System Based on Radio Frequency Identification and Wireless Sensor Networks

    OpenAIRE

    Chao, Kuei-Hsiang; Chen, Pi-Yun

    2014-01-01

    This study primarily focuses on the use of radio frequency identification (RFID) as a form of traffic flow detection, which transmits collected information related to traffic flow directly to a control system through an RS232 interface. At the same time, the sensor analyzes and judges the information using an extension algorithm designed to achieve the objective of controlling the flow of traffic. In addition, the traffic flow situation is also transmitted to a remote monitoring control syste...

  20. Cellular Automaton Models of Highway Traffic Flow Considering Lane-Control and Speed-Control

    Institute of Scientific and Technical Information of China (English)

    钱勇生; 李文俊; 曾俊伟; 王敏; 杜加伟; 广晓平

    2011-01-01

    As two kinds of management modes of highway tramc control, lane-control, and speed-control produce different effect under different conditions. In this paper, traffic flow cellular automaton models for four-lane highway system with two opposing directions under the above two modes are established considering car and truck mixed running. Through computer numerical simulating, the fundamental diagrams with different parameters are obtained, and after the analysis of density-flux diagrams, the variation discipline of flux with traffic density under different control models is gained. The results indicate that, compared with lane-control, utilization ratio of road can be further improved with speed-control when the truck number increases. The research result is of great significance for reasonable providing theoretical guidance for highway traffic control.

  1. Flow Diode and Method for Controlling Fluid Flow Origin of the Invention

    Science.gov (United States)

    Dyson, Rodger W (Inventor)

    2015-01-01

    A flow diode configured to permit fluid flow in a first direction while preventing fluid flow in a second direction opposite the first direction is disclosed. The flow diode prevents fluid flow without use of mechanical closures or moving parts. The flow diode utilizes a bypass flowline whereby all fluid flow in the second direction moves into the bypass flowline having a plurality of tortuous portions providing high fluidic resistance. The portions decrease in diameter such that debris in the fluid is trapped. As fluid only travels in one direction through the portions, the debris remains trapped in the portions.

  2. Active flow control for a NACA-0012 Profile: Part II

    Science.gov (United States)

    Oualli, H.; Makadem, M.; Ouchene, H.; Ferfouri, A.; Bouabdallah, A.; Gad-El-Hak, M.

    2016-11-01

    Active flow control is applied to a NACA-0012 profile. The experiments are conducted in a wind tunnel. Using a high-resolution visible-light camera and tomography, flow visualizations are carried out. LES finite-volume 3D code is used to complement the physical experiments. The symmetric wing is clipped into two parts, and those parts extend and retract along the chord according to the same sinusoidal law we optimized last year for the same profile but clipped at an angle of 60 deg, instead of the original 90 deg. The Reynolds number range is extended to 500,000, thus covering the flying regimes of micro-UAVs, UAVs, as well as small aircraft. When the nascent cavity is open and the attack angle is 30 deg, the drag coefficient is increased by 1,300%, as compared to the uncontrolled case. However, when the cavity is covered and Re <=105 , a relatively small frequency, f <= 30 Hz, is required for the drag coefficient to drop to negative values. At the maximum Reynolds number, thrust is generated but only at much higher frequencies, 12 <= f <= 16 kHz.

  3. Plasma-based Control of Supersonic Nozzle Flow

    CERN Document Server

    Gaitonde, Datta V

    2009-01-01

    The flow structure obtained when Localized Arc Filament Plasma Actuators (LAFPA) are employed to control the flow issuing from a perfectly expanded Mach 1.3 nozzle is elucidated by visualizing coherent structures obtained from Implicit Large-Eddy Simulations. The computations reproduce recent experimental observations at the Ohio State University to influence the acoustic and mixing properties of the jet. Eight actuators were placed on a collar around the periphery of the nozzle exit and selectively excited to generate various modes, including first and second mixed (m = +/- 1 and m = +/- 2) and axisymmetric (m = 0). In this fluid dynamics video http://ecommons.library.cornell.edu/bitstream/1813/13723/2/Alljoinedtotalwithmodetextlong2-Datta%20MPEG-1.m1v, http://ecommons.library.cornell.edu/bitstream/1813/13723/3/Alljoinedtotalwithmodetextlong2-Datta%20MPEG-2.m2v}, unsteady and phase-averaged quantities are displayed to aid understanding of the vortex dynamics associated with the m = +/- 1 and m = 0 modes exci...

  4. Dynamic evolution process of turbulent channel flow after opposition control

    Science.gov (United States)

    Ge, Mingwei; Tian, De; Yongqian, Liu

    2017-02-01

    Dynamic evolution of turbulent channel flow after application of opposition control (OC), together with the mechanism of drag reduction, is studied through direct numerical simulation (DNS). In the simulation, the pressure gradient is kept constant, and the flow rate increases due to drag reduction. In the transport of mean kinetic energy (MKE), one part of the energy from the external pressure is dissipated by the mean shear, and the other part is transported to the turbulent kinetic energy (TKE) through a TKE production term (TKP). It is found that the increase of MKE is mainly induced by the reduction of TKP that is directly affected by OC. Further analysis shows that the suppression of the redistribution term of TKE in the wall normal direction plays a key role in drag reduction, which represses the wall normal velocity fluctuation and then reduces TKP through the attenuation of its main production term. When OC is suddenly applied, an acute imbalance of energy in space is induced by the wall blowing and suction. Both the skin-friction and TKP terms exhibit a transient growth in the initial phase of OC, which can be attributed to the local effect of and in the viscous sublayer. Project supported by the National Natural Science Foundation of China (Grant No. 11402088 and Grant No. 51376062) , State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (Grant No. LAPS15005), and ‘the Fundamental Research Funds for the Central Universities’ (Grant No.2014MS33).

  5. Jet flow control at the blade scale to manipulate lift

    Science.gov (United States)

    Braud, Caroline; Guilmineau, Emmanuel

    2016-09-01

    The turbulent atmospheric boundary layer in which wind turbines are implemented is strongly inhomogeneous and unsteady. This induces unsteady mechanical loads at different characteristic time scales from seconds to minutes which limits significantly their life time. Different control strategies have been proposed in the framework of the French ANR SmartEole project to alleviate the impact of these upstream fluctuations at the farm, wind turbine and blade scales (i.e. characteristic time scales from seconds to minutes). The present work, which is part of this ANR project, focuses on the flow control strategies at the blade scale, to manipulate lift and thus alleviate fatigue loads. The design of a NACA654-421 airfoil profile has been modified to be able to implement jet control. Slotted jet and discrete jet configurations were implemented numerically and experimentally respectively. Results show the ability of both configurations to increase the lift by up to 30% using a significant redistribution of the mean shear. Efficiency seems to be more important using slotted jets, which however needs to be confirmed from 3D simulations.

  6. Chaos control for the plates subjected to subsonic flow

    Science.gov (United States)

    Norouzi, Hamed; Younesian, Davood

    2016-07-01

    The suppression of chaotic motion in viscoelastic plates driven by external subsonic air flow is studied. Nonlinear oscillation of the plate is modeled by the von-Kármán plate theory. The fluid-solid interaction is taken into account. Galerkin's approach is employed to transform the partial differential equations of the system into the time domain. The corresponding homoclinic orbits of the unperturbed Hamiltonian system are obtained. In order to study the chaotic behavior of the plate, Melnikov's integral is analytically applied and the threshold of the excitation amplitude and frequency for the occurrence of chaos is presented. It is found that adding a parametric perturbation to the system in terms of an excitation with the same frequency of the external force can lead to eliminate chaos. Variations of the Lyapunov exponent and bifurcation diagrams are provided to analyze the chaotic and periodic responses. Two perturbation-based control strategies are proposed. In the first scenario, the amplitude of control forces reads a constant value that should be precisely determined. In the second strategy, this amplitude can be proportional to the deflection of the plate. The performance of each controller is investigated and it is found that the second scenario would be more efficient.

  7. GASP cloud encounter statistics - Implications for laminar flow control flight

    Science.gov (United States)

    Jasperson, W. H.; Nastrom, G. D.; Davis, R. E.; Holdeman, J. D.

    1984-01-01

    The cloud observation archive from the NASA Global Atmospheric Sampling Program (GASP) is analyzed in order to derive the probability of cloud encounter at altitudes normally flown by commercial airliners, for application to a determination of the feasability of Laminar Flow Control (LFC) on long-range routes. The probability of cloud encounter is found to vary significantly with season. Several meteorological circulation features are apparent in the latitudinal distribution of cloud cover. The cloud encounter data are shown to be consistent with the classical midlatitude cyclone model with more clouds encountered in highs than in lows. Aircraft measurements of route-averaged time-in-clouds fit a gamma probability distribution model which is applied to estimate the probability of extended cloud encounter, and the associated loss of LFC effectiveness along seven high-density routes. The probability is demonstrated to be low.

  8. Hillslope characteristics as controls of subsurface flow variability

    Directory of Open Access Journals (Sweden)

    S. Bachmair

    2012-06-01

    Full Text Available Hillslope hydrological dynamics, particularly subsurface flow (SSF, are highly variable and complex. A profound understanding of factors controlling this variability is needed. Therefore we investigated the relationship between variability of shallow water table dynamics and various hillslope characteristics. We ask whether measurable hillslope properties explain patterns of subsurface flow variability. To approach this question shallow water table dynamics of three adjacent large-scale hillslopes were monitored with high spatial and temporal resolution over 18 months. The hillslopes are similar in terms of topography and parent material, but different in vegetation cover (grassland, coniferous forest, and mixed forest. We expect vegetation to be an important driver of water table dynamics at our study site, especially given the minor differences in topography. Various hillslope properties were determined in the field and via GIS analysis: common topography descriptors, well depth, soil properties via slug tests, and several vegetation parameters. Response variables characterizing the water table response per well were calculated for different temporal scales (entire time series, seasonal scale, event scale. Partial correlation analysis and a Random Forest machine learning approach were carried out to assess the explainability of SSF variability by measurable hillslope characteristics. We found a complex interplay of predictors, yet soil properties and topography showed the highest single explanatory power. Surprisingly, vegetation characteristics played a minor role. Solely throughfall and canopy cover exerted a slightly stronger control, especially in summer. Most importantly, the examined hillslope characteristics explained only a small proportion of the observed SSF variability. Consequently there must be additional important drivers not represented by current measurement techniques of the hillslope configuration (e.g. bedrock properties

  9. Hillslope characteristics as controls of subsurface flow variability

    Science.gov (United States)

    Bachmair, S.; Weiler, M.

    2012-10-01

    Hillslope hydrological dynamics, particularly subsurface flow (SSF), are highly variable and complex. A profound understanding of factors controlling this variability is needed. Therefore we investigated the relationship between variability of shallow water table dynamics and various hillslope characteristics. We ask whether measurable hillslope properties explain patterns of subsurface flow variability. To approach this question, shallow water table dynamics of three adjacent large-scale hillslopes were monitored with high spatial and temporal resolution over 18 months. The hillslopes are similar in terms of topography and parent material, but different in vegetation cover (grassland, coniferous forest, and mixed forest). We expect vegetation to be an important driver of water table dynamics at our study site, especially given the minor differences in topography. Various hillslope properties were determined in the field and via GIS analysis: common topography descriptors, well depth, soil properties via slug tests, and several vegetation parameters. Response variables characterizing the water table response per well were calculated for different temporal scales (entire time series, seasonal scale, event scale). Partial correlation analysis and a Random Forest machine learning approach were carried out to assess the explainability of SSF variability by measurable hillslope characteristics. We found a complex interplay of predictors, yet soil properties and topography showed the highest single explanatory power. Surprisingly, vegetation characteristics played a minor role. Solely throughfall and canopy cover exerted a slightly stronger control, especially in summer. Most importantly, the examined hillslope characteristics explained only a small proportion of the observed SSF variability. Consequently there must be additional important drivers not represented by current measurement techniques of the hillslope configuration (e.g. bedrock properties, preferential

  10. Hillslope characteristics as controls of subsurface flow variability

    Directory of Open Access Journals (Sweden)

    S. Bachmair

    2012-10-01

    Full Text Available Hillslope hydrological dynamics, particularly subsurface flow (SSF, are highly variable and complex. A profound understanding of factors controlling this variability is needed. Therefore we investigated the relationship between variability of shallow water table dynamics and various hillslope characteristics. We ask whether measurable hillslope properties explain patterns of subsurface flow variability. To approach this question, shallow water table dynamics of three adjacent large-scale hillslopes were monitored with high spatial and temporal resolution over 18 months. The hillslopes are similar in terms of topography and parent material, but different in vegetation cover (grassland, coniferous forest, and mixed forest. We expect vegetation to be an important driver of water table dynamics at our study site, especially given the minor differences in topography. Various hillslope properties were determined in the field and via GIS analysis: common topography descriptors, well depth, soil properties via slug tests, and several vegetation parameters. Response variables characterizing the water table response per well were calculated for different temporal scales (entire time series, seasonal scale, event scale. Partial correlation analysis and a Random Forest machine learning approach were carried out to assess the explainability of SSF variability by measurable hillslope characteristics. We found a complex interplay of predictors, yet soil properties and topography showed the highest single explanatory power. Surprisingly, vegetation characteristics played a minor role. Solely throughfall and canopy cover exerted a slightly stronger control, especially in summer. Most importantly, the examined hillslope characteristics explained only a small proportion of the observed SSF variability. Consequently there must be additional important drivers not represented by current measurement techniques of the hillslope configuration (e.g. bedrock properties

  11. Design, analysis, optimization and control of rotor tip flows

    Science.gov (United States)

    Maesschalck, Cis Guy M. De

    Developments in turbomachinery focus on efficiency and reliability enhancements, while reducing the production costs. In spite of the many noteworthy experimental and numerical investigations over the past decades, the turbine tip design presents numerous challenges to the engine manufacturers, and remains the primary factor defining the machine durability for the periodic removal of the turbine components during overhaul. Due to the hot gases coming from the upstream combustion chamber, the turbine blades are subjected to temperatures far above the metal creep temperature, combined with severe thermal stresses induced within the blade material. Inadequate designs cause early tip burnouts leading to considerable performance degradations, or even a catastrophic turbine failure. Moreover, the leakage spillage, nowadays often exceeding the transonic regime, generates large aerodynamic penalties which are responsible for about one third of the turbine losses. In this view, the current doctoral research exploits the potential through the modification and optimization of the blade tip shape as a means to control the tip leakage flow aerodynamics and manage the heat load distribution over the blade profile to improve the turbine efficiency and durability. Three main design strategies for unshrouded turbine blade tips were analyzed and optimized: tight running clearances, blade tip contouring and the use of complex squealer-like geometries. The altered overtip flow physics and heat transfer characteristics were simulated for tight gap sizes as low as 0.5% down to 0.1% of the blade height, occurring during engine transients and soon to be expected due to recent developments in active clearance control strategies. The potential of fully 3D contoured blade top surfaces, allowing to adapt the profile locally to the changing flow conditions throughout the camberline, is quantified. First adopting a quasi-3D approach and subsequently using a full 3D optimization. For the

  12. Automated methanol dosage using liquid flow controllers; Automatisierte Methanolregelung mit Liquid Flow Controllern

    Energy Technology Data Exchange (ETDEWEB)

    Sattler, Thomas [Buerkert Fluid Control Systems, Ingelfingen (Germany)

    2010-12-15

    Transmission gearwheels are frequently exposed to extreme loads. Generally, in order to counteract premature wear, gearwheels made from steel are surface-hardened. This is carried out primarily by gas carburizing and subsequent quenching (case hardening). These processes of gas carburizing increase the carbon content in the boundary area of the workpiece and change the boundary structure of the steel. In the foundation Institut fuer Werkstofftechnik (IWT) (Institute for Materials Engineering) in Bremen, they are engaged intensively with the various processes of heat treatment for the hardening of steel. As an alternative to gas carburizing using endogas, the Nitrogen-Methanol Process, in which liquid methanol is directly introduced into the furnace, plays an important role and is gaining in importance. At the IWT, Liquid Flow Controllers (LFC) provide regulated and completely documented processes. (orig.)

  13. Provably Correct Control-Flow Graphs from Java Programs with Exceptions

    NARCIS (Netherlands)

    Amighi, A.; de Carvalho Gomes, Pedro; Huisman, Marieke

    2011-01-01

    We present an algorithm to extract flow graphs from Java bytecode, focusing on exceptional control flows. We prove its correctness, meaning that the behaviour of the extracted control-flow graph is an over-approximation of the behaviour of the original program. Thus any safety property that holds

  14. Unveiling astrocytic control of cerebral blood flow with optogenetics.

    Science.gov (United States)

    Masamoto, Kazuto; Unekawa, Miyuki; Watanabe, Tatsushi; Toriumi, Haruki; Takuwa, Hiroyuki; Kawaguchi, Hiroshi; Kanno, Iwao; Matsui, Ko; Tanaka, Kenji F; Tomita, Yutaka; Suzuki, Norihiro

    2015-06-16

    Cortical neural activities lead to changes in the cerebral blood flow (CBF), which involves astrocytic control of cerebrovascular tone. However, the manner in which astrocytic activity specifically leads to vasodilation or vasoconstriction is difficult to determine. Here, cortical astrocytes genetically expressing a light-sensitive cation channel, channelrhodopsin-2 (ChR2), were transcranially activated with a blue laser while the spatiotemporal changes in CBF were noninvasively monitored with laser speckle flowgraphy in the anesthetised mouse cortex. A brief photostimulation induced a fast transient increase in CBF. The average response onset time was 0.7 ± 0.7 sec at the activation foci, and this CBF increase spread widely from the irradiation spot with an apparent propagation speed of 0.8-1.1 mm/sec. The broad increase in the CBF could be due to a propagation of diffusible vasoactive signals derived from the stimulated astrocytes. Pharmacological manipulation showed that topical administration of a K(+) channel inhibitor (BaCl2; 0.1-0.5 mM) significantly reduced the photostimulation-induced CBF responses, which indicates that the ChR2-evoked astrocytic activity involves K(+) signalling to the vascular smooth muscle cells. These findings demonstrate a unique model for exploring the role of the astrocytes in gliovascular coupling using non-invasive, time-controlled, cell-type specific perturbations.

  15. Power Flow Algorithms for Multi-Terminal VSC-HVDC With Droop Control

    OpenAIRE

    Wang, Wenyuan; Barnes, Mike

    2014-01-01

    This paper addresses the problem posed by complex, nonlinear controllers for power system load flows employing multi-terminal voltage source converter (VSC) HVDC systems. More realistic dc grid control strategies can thus be carefully considered in power flow analysis of ac/dc grids. Power flow methods for multi-terminal VSC-HVDC (MTDC) systems are analyzed for different types of dc voltage control techniques and the weaknesses of present methods are addressed. As distributed voltage control ...

  16. Slit-check dams for the control of debris flow

    Science.gov (United States)

    Armanini, Aronne; Larcher, Michele

    2017-04-01

    Debris flows are paroxysmal events that mobilize, alongside water, huge quantities of sediment in a very short time, then with both solid and liquid huge discharges, possibly exceeding the capacity of the current torrent restoration works. In this respect, the climate change forcing cannot be ignored. In the majority of urbanized areas, that are generally the most vulnerable, there is often not enough space to create channelling works able to let the volumes pass through without overflowing. The simplest, less expensive and most sustainable solution consists in reducing the peak solid discharge by creating storage areas upstream of the settlements, typically upstream of the alluvial fans, allowing for reduced works of canalization, that are compatible with the constraints imposed by the urbanization. The general idea consists in storing a part of the flowing solids during the peak of the hydrograph and releasing it in a successive phase or during minor floods. For this purpose, and in order to optimize the solid peak discharge reduction, it is necessary that properly designed open-check dams, capable of inducing a significative sedimentation of the solid discharge only when this exceeds a design-threshold value, control the deposition basins. A correct design of the check dam is crucial in order to induce the sedimentation in the right amount and at the right moment: a too early sedimentation might fill the volume before the peak, like in the case of close-check dams, while a too weak sedimentation might not use the whole available volume. In both cases, the channelling works might not be sufficient to let all the flow pass through, compromising the safety of the settlement. To avoid this inconvenience, we propose the use of slit-check dams, whose efficiency has already been proved for bed load. Check dams are often designed only on the base of the designer's experience. Besides, even today it is often believed that the filtering effect of open check dams is

  17. Some aspects of flow control over a NACA0015 airfoil using synthetic jets

    Science.gov (United States)

    Parthasarathy, T.; Das, S. P.

    2017-04-01

    Flow control for performance enhancement over airfoils has become an increasingly important topic. This work details the characteristics of flow control using synthetic jets over a NACA0015 airfoil at a Reynolds number of 896,000 based on the chord length and free stream velocity, and at 20° angle of attack wherein the flow is separated. Numerical simulations were performed to help understand the behaviour of the controlled flow for a range of synthetic jet parameters. Analysis of key flow parameters such as phase averaged pressure and streamline profiles indicate that the synthetic jet is efficient in increasing the lift coefficient; more so for larger jet amplitudes and at smaller angles of jet injection. Behaviour of the flow characteristics for controlled cases has been analysed from the flow structures obtained from the same. This work serves as a platform to qualitatively and quantitatively understand the effects of the jet parameters on the separated flow over the airfoil.

  18. VARIABLE FIRING RATE OIL BURNER USING PULSE FUEL FLOW CONTROL.

    Energy Technology Data Exchange (ETDEWEB)

    KRISHNA,C.R.; BUTCHER,T.A.; KAMATH,B.R.

    2004-10-01

    The residential oil burner market is currently dominated by the pressure-atomized retention head burner, which has an excellent reputation for reliability and efficiency. In this burner, oil is delivered to a fuel nozzle at pressures from 100 to 150 psi. In addition, to atomizing the fuel, the small, carefully controlled size of the nozzle exit orifice serves to control the burner firing rate. Burners of this type are currently available at firing rates of more than 0.5 gallons-per-hour (70,000 Btu/hr). Nozzles have been made for lower firing rates, but experience has shown that such nozzles suffer rapid fouling of the necessarily small passages, leading to bad spray patterns and poor combustion performance. Also, traditionally burners and the nozzles are oversized to exceed the maximum demand. Typically, this is figured as follows. The heating load of the house on the coldest day for the location is considered to define the maximum heat load. The contractor or installer adds to this to provide a safety margin and for future expansion of the house. If the unit is a boiler that provides domestic hot water through the use of a tankless heating coil, the burner capacity is further increased. On the contrary, for a majority of the time, the heating system is satisfying a much smaller load, as only rarely do all these demands add up. Consequently, the average output of the heating system has to be much less than the design capacity and this is accomplished by start and stop cycling operation of the system so that the time-averaged output equals the demand. However, this has been demonstrated to lead to overall efficiencies lower than the steady-state efficiency. Therefore, the two main reasons for the current practice of using oil burners much larger than necessary for space heating are the unavailability of reliable low firing rate oil burners and the desire to assure adequate input rate for short duration, high draw domestic hot water loads. One approach to solve this

  19. Interaction Between Strategic and Local Traffic Flow Controls

    Science.gov (United States)

    Grabbe, Son; Sridhar, Banavar; Mukherjee, Avijit; Morando, Alexander

    2010-01-01

    The loosely coordinated sets of traffic flow management initiatives that are operationally implemented at the national- and local-levels have the potential to under, over, and inconsistently control flights. This study is designed to explore these interactions through fast-time simulations with an emphasis on identifying inequitable situations in which flights receive multiple uncoordinated delays. Two operationally derived scenarios were considered in which flights arriving into the Dallas/Fort Worth International Airport were first controlled at the national-level, either with a Ground Delay Program or a playbook reroute. These flights were subsequently controlled at the local level. The Traffic Management Advisor assigned them arrival scheduling delays. For the Ground Delay Program scenarios, between 51% and 53% of all arrivals experience both pre-departure delays from the Ground Delay Program and arrival scheduling delays from the Traffic Management Advisor. Of the subset of flights that received multiple delays, between 5.7% and 6.4% of the internal departures were first assigned a pre-departure delay by the Ground Delay Program, followed by a second pre-departure delay as a result of the arrival scheduling. For the playbook reroute scenario, Dallas/Fort Worth International Airport arrivals were first assigned pre-departure reroutes based on the MW_2_DALLAS playbook plan, and were subsequently assigned arrival scheduling delays by the Traffic Management Advisor. Since the airport was operating well below capacity when the playbook reroute was in effect, only 7% of the arrivals were observed to receive both rerouting and arrival scheduling delays. Findings from these initial experiments confirm field observations that Ground Delay Programs operated in conjunction with arrival scheduling can result in inequitable situations in which flights receive multiple uncoordinated delays.

  20. Controlling Subsurface Fractures and Fluid Flow: A Basic Research Agenda

    Energy Technology Data Exchange (ETDEWEB)

    Pyrak-Nolte, Laura J [Purdue Univ., West Lafayette, IN (United States); DePaolo, Donald J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Pietraß, Tanja [USDOE Office of Science, Washington, DC (United States)

    2015-05-22

    From beneath the surface of the earth, we currently obtain about 80-percent of the energy our nation consumes each year. In the future we have the potential to generate billions of watts of electrical power from clean, green, geothermal energy sources. Our planet’s subsurface can also serve as a reservoir for storing energy produced from intermittent sources such as wind and solar, and it could provide safe, long-term storage of excess carbon dioxide, energy waste products and other hazardous materials. However, it is impossible to underestimate the complexities of the subsurface world. These complexities challenge our ability to acquire the scientific knowledge needed for the efficient and safe exploitation of its resources. To more effectively harness subsurface resources while mitigating the impacts of developing and using these resources, the U.S. Department of Energy established SubTER – the Subsurface Technology and Engineering RD&D Crosscut team. This DOE multi-office team engaged scientists and engineers from the national laboratories to assess and make recommendations for improving energy-related subsurface engineering. The SubTER team produced a plan with the overall objective of “adaptive control of subsurface fractures and fluid flow.”This plan revolved around four core technological pillars—Intelligent Wellbore Systems that sustain the integrity of the wellbore environment; Subsurface Stress and Induced Seismicity programs that guide and optimize sustainable energy strategies while reducing the risks associated with subsurface injections; Permeability Manipulation studies that improve methods of enhancing, impeding and eliminating fluid flow; and New Subsurface Signals that transform our ability to see into and characterize subsurface systems. The SubTER team developed an extensive R&D plan for advancing technologies within these four core pillars and also identified several areas where new technologies would require additional basic research

  1. Bandwidth turbulence control based on flow community structure in the Internet

    Science.gov (United States)

    Wu, Xiaoyu; Gu, Rentao; Ji, Yuefeng

    2016-10-01

    Bursty flows vary rapidly in short period of time, and cause fierce bandwidth turbulence in the Internet. In this letter, we model the flow bandwidth turbulence process by constructing a flow interaction network (FIN network), with nodes representing flows and edges denoting bandwidth interactions among them. To restrain the bandwidth turbulence in FIN networks, an immune control strategy based on flow community structure is proposed. Flows in community boundary positions are immunized to cut off the inter-community turbulence spreading. By applying this control strategy in the first- and the second-level flow communities separately, 97.2% flows can effectively avoid bandwidth variations by immunizing 21% flows, and the average bandwidth variation degree reaches near zero. To achieve a similar result, about 70%-90% immune flows are needed with targeted control strategy based on flow degrees and random control strategy. Moreover, simulation results showed that the control effect of the proposed strategy improves significantly if the immune flow number is relatively smaller in each control step.

  2. MHD Stability Analysis and Flow Controls of Liquid Metal Free Surface Film Flows as Fusion Reactor PFCs

    Science.gov (United States)

    Zhang, Xiujie; Pan, Chuanjie; Xu, Zengyu

    2016-12-01

    Numerical and experimental investigation results on the magnetohydrodynamics (MHD) film flows along flat and curved bottom surfaces are summarized in this study. A simplified modeling has been developed to study the liquid metal MHD film state, which has been validated by the existing experimental results. Numerical results on how the inlet velocity (V), the chute width (W) and the inlet film thickness (d0) affect the MHD film flow state are obtained. MHD stability analysis results are also provided in this study. The results show that strong magnetic fields make the stable V decrease several times compared to the case with no magnetic field, especially small radial magnetic fields (Bn) will have a significant impact on the MHD film flow state. Based on the above numerical and MHD stability analysis results flow control methods are proposed for flat and curved MHD film flows. For curved film flow we firstly proposed a new multi-layers MHD film flow system with a solid metal mesh to get the stable MHD film flows along the curved bottom surface. Experiments on flat and curved MHD film flows are also carried out and some firstly observed results are achieved. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2014GB125003 and 2013GB114002), National Natural Science Foundation of China (No. 11105044)

  3. Power flow controller with a fractionally rated back-to-back converter

    Science.gov (United States)

    Divan, Deepakraj M.; Kandula, Rajendra Prasad; Prasai, Anish

    2016-03-08

    A power flow controller with a fractionally rated back-to-back (BTB) converter is provided. The power flow controller provide dynamic control of both active and reactive power of a power system. The power flow controller inserts a voltage with controllable magnitude and phase between two AC sources at the same frequency; thereby effecting control of active and reactive power flows between the two AC sources. A transformer may be augmented with a fractionally rated bi-directional Back to Back (BTB) converter. The fractionally rated BTB converter comprises a transformer side converter (TSC), a direct-current (DC) link, and a line side converter (LSC). By controlling the switches of the BTB converter, the effective phase angle between the two AC source voltages may be regulated, and the amplitude of the voltage inserted by the power flow controller may be adjusted with respect to the AC source voltages.

  4. Aerodynamic Flow Control by Thermoacoustic Excitation from the Constituent Nanomaterials on the Platform Surface

    Science.gov (United States)

    2016-02-01

    control, turbulence, fluid mechanics, nonlinear coupling, planar jet experiment, Director’s Research Initiative (DRI) 16. SECURITY CLASSIFICATION OF...Successful development of active aerodynamic flow control technologies that delay or prevent separation could lead to substantial performance...improvements, including increased speed, maneuverability, payload capacity, and/or range. However, instances in which active flow control technologies have

  5. Active bypass flow control for a seal in a gas turbine engine

    Energy Technology Data Exchange (ETDEWEB)

    Ebert, Todd A.; Kimmel, Keith D.

    2017-01-10

    An active bypass flow control system for controlling bypass compressed air based upon leakage flow of compressed air flowing past an outer balance seal between a stator and rotor of a first stage of a gas turbine in a gas turbine engine is disclosed. The active bypass flow control system is an adjustable system in which one or more metering devices may be used to control the flow of bypass compressed air as the flow of compressed air past the outer balance seal changes over time as the outer balance seal between the rim cavity and the cooling cavity wears. In at least one embodiment, the metering device may include a valve formed from one or more pins movable between open and closed positions in which the one pin at least partially bisects the bypass channel to regulate flow.

  6. Control valve and control valve system for controlling solids flow, methods of manufacture thereof and articles comprising the same

    Energy Technology Data Exchange (ETDEWEB)

    Jukkola, Glen D.; Teigen, Bard C.

    2017-04-11

    Disclosed herein is a solids flow control valve comprising a standpipe; a shoe; and a transport pipe; wherein the standpipe is in operative communication with the shoe and lies upstream of the shoe; the standpipe comprising a first end and a second end, where the first end is in contact with a source that contains disposable solids and the second end is in fluid contact with the shoe; the shoe being operative to restrict the flow of the disposable solids; the transport pipe being disposed downstream of the shoe to receive and transport the solids from the shoe.

  7. PI2 controller based coordinated control with Redox Flow Battery and Unified Power Flow Controller for improved Restoration Indices in a deregulated power system

    Directory of Open Access Journals (Sweden)

    R. Thirunavukarasu

    2016-12-01

    Full Text Available The nature of power system restoration problem involves status assessment, optimization of generation capability and load pickup. This paper proposes the evaluation of Power System Restoration Indices (PSRI based on the Automatic Generation Control (AGC assessment of interconnected power system in a deregulated environment. The PSRI are useful for system planners to prepare the power system restoration plans and to improve the efficiency of the physical operation of the power system with the increased transmission capacity in the network. The stabilization of frequency and tie-line power oscillations in an interconnected power system becomes challenging when implemented in the future competitive environment. This paper also deals with the concept of AGC in two-area reheat power system having coordinated control action with Redox Flow Battery (RFB and Unified Power Flow Controller (UPFC are capable of controlling the network performance in a very fast manner and improve power transfer limits in order to have a better restoration. In addition to that a new Proportional–Double Integral (PI2 controller is designed and implemented in AGC loop and controller parameters are optimized through Bacterial Foraging Optimization (BFO algorithm. Simulation results reveal that the proposed PI2 controller is that it has good stability during load variations, excellent transient and dynamic responses when compared with the system comprising PI controller. Moreover the AGC loop with RFB coordinated with UPFC has greatly improved the dynamic response and it reduces the control input requirements, to ensure improved PSRI in order to provide the reduced restoration time, thereby improving the system reliability.

  8. Power system security enhancement with unified power flow controller under multi-event contingency conditions

    National Research Council Canada - National Science Library

    S. Ravindra; Chintalapudi V. Suresh; S. Sivanagaraju; V.C. Veera Reddy

    2017-01-01

    .... An improved teaching learning based optimization (ITLBO) algorithm has been presented. To enhance the system security under contingency conditions in the presence of unified power flow controller (UPFC...

  9. Control of the Unsteady Flow Structure Behind the Cylinder with Passive Control Method

    Directory of Open Access Journals (Sweden)

    Mustafa Atakan Akar

    2014-04-01

    Full Text Available In this study, it is aimed to control flow structure downstream of inner cylinder with seven different diameters (Di= 30, 40, 50, 60, 70, 80, 90mm by a surrounding outer cylinder that have β=0.5 porosity. The diameter of outer cylinder was chosen as 100mm. The perforation hole diameters of the cylinder were 10mm. The water height was kept constant during experiments as hw=400mm.The depth-averaged free stream velocity was U=100m/s which corresponded to a Reynolds number ReD=10000 based on outer cylinder diameter. Flow characteristics downstream of cylinder was investigated by using particle image velocimetry (PIV technique. PIV experiments were performed at the mid-section of water 200mm. It has been observed that the perforated outer cylinder decreased vortex shedding downstream of inner cylinder with different diameters (Di=30, 40, 50, 60, 70, 80, 90mm. For high diameter ratios Di/Do≥0.7 perforated outer cylinder lost its effect on the flow control.

  10. Developed generalised unified power flow controller model in the Newton–Raphson power-flow analysis using combined mismatches method

    DEFF Research Database (Denmark)

    Kamel, Salah; Jurado, Francisco; Chen, Zhe

    2016-01-01

    This study proposes the generalised unified power flow controller (GUPFC) model in the hybrid current power mismatch Newton-Raphson formulation (HPCIM). In this model, active power, real and imaginary current components are injected at the terminals of series impedances of GUPFC. These injected...... values are calculated during the iterative process based on the desired controlled values and buses voltage at the terminals of GUPFC. The parameters of GUPFC can be calculated during the iterative process and the final values are updated after load flow convergence. Using the developed GUPFC model......, the original structure and symmetry of the admittance and Jacobian matrices can still be kept, the changing of Jacobian matrix is eliminated. Consequently, the complexities of the computer load flow program codes with GUPFC are reduced. The HPCIM load flow code with the proposed model is written in C...

  11. Flujo de control en iOS Flow control in iOS

    Directory of Open Access Journals (Sweden)

    Franklin Hernández Castro

    2012-11-01

    Full Text Available El objetivo de este artículo es explicar los flujos de control que se usan en la programación de las aplicaciones en iOS, con el fin de resumir los aspectos más relevantes que se deben tomar en cuenta para programar una tarea a ser realizada por un dispositivo móvil del tipo iPhone o iPad. Debido a que el ambiente iOS es estrictamente orientado a objetos (OOP, los flujos de control no son obvios; además, los estándares de la firma Apple® definen patrones de diseño en el sistema que son altamente recomendados en este tipo de diseño. En este artículo se introducen algunos de ellos.This paper explain the control flows that are used by programming applications in iOS, trying to summarize the most important aspects to be considered by programming mobile devices like iPhone and iPad. Because iOS environment, is strictly a object-oriented one(OOP, control flows are not obvious, besides Apple® use design patterns highly recommended in this type of programming. Here we introduces some of them.

  12. The friction control of magnetic fluid in the Couette flow

    Science.gov (United States)

    Labkovich, O. N.; Reks, A. G.; Chernobai, V. A.

    2017-06-01

    In the work characteristic areas of magnetic fluid flow are experimentally determined in the gap between the cylinders: the area of strong dipole-dipole interaction between magnetite particles 041,2. For areas with high flow losses in viscous friction is shown the possibility of reducing the introduction of magnetic fluid of carbon nanotubes and creating a rotating magnetic field.

  13. Flow Physics and Control for Internal and External Aerodynamics

    Science.gov (United States)

    Wygnanski, I.

    2010-01-01

    Exploiting instabilities rather than forcing the flow is advantageous. Simple 2D concepts may not always work. Nonlinear effects may result in first order effect. Interaction between spanwise and streamwise vortices may have a paramount effect on the mean flow, but this interaction may not always be beneficial.

  14. Hemodynamic Parameters of Low-Flow Isoflurane and Low-Flow Sevoflurane Anesthesia During Controlled Ventilation With Laryngeal Mask Airway

    OpenAIRE

    Negargar, Sohrab; Peirovifar, Ali; Mahmoodpoor, Ata; Parish, Masoud; Golzari, Samad EJ; Molseqi, Haniye; Negargar, Soheil

    2014-01-01

    Background: Nowadays laryngeal mask airway (LMA) is popular as one of the best choices for airway management. Low-flow anesthesia has some advantages like lower pollution, hemodynamic stability and cost effectiveness. Volatile anesthetics are widely used for anesthesia maintenance during operations. Sevoflurane has more hemodynamic stability compared to isoflurane, but there are few studies comparing the hemodynamic stabilities of these two anesthetics during controlled low flow anesthesia wi...

  15. Steady streamwise transpiration control in turbulent pipe flow

    CERN Document Server

    Gómez, F; Rudman, M; Sharma, AS; McKeon, BJ

    2016-01-01

    A study of the the main features of low- and high amplitude steady streamwise wall transpiration applied to pipe flow is presented. The effect of the two transpiration parameters, amplitude and wavenumber, on the flow have been investigated by means of direct numerical simulation at a moderate turbulent Reynolds number. The behaviour of the three identified mechanisms that act in the flow: modification of Reynolds shear stress, steady streaming and generation of non-zero mean streamwise gradients, have been linked to the transpiration parameters. The observed trends have permitted the identification of wall transpiration configurations able to reduce or increase the overall flow rate in -36.1% and 19.3% respectively. A resolvent analysis has been carried out to obtain a description of the reorganization of the flow structures induced by the transpiration.

  16. Ferrofluid magnetoviscous control of wall flow channeling in porous media

    Institute of Scientific and Technical Information of China (English)

    Fa(ic)al Larachi; Damien Desvigne

    2007-01-01

    We analyzed the phenomenon of ferrofluid magnetoviscosity in high-permeability wall-region non-magnetic porous media of the Müller kind.After upscaling the pore-level ferrohydrodynamic model, we obtained a simplified volume-average zero-order axisymmetric model for non-Darcy non-turbulent flow of steady-state isothermal incompressible Newtonian ferrofluids through a porous medium experiencing external constant bulk-flow oriented gradient magnetic field, ferrofluid self-consistent demagnetizing field and induced magnetic field in the solid. The model was explored in contexts plagued by wall flow maldistribution due to low column-to-particle diameter ratios. It was shown that for proper magnetic field arrangement, wall channeling can be reduced by inflating wall flow resistance through magnetovisco-thickening and Kelvin body force density which reroute a fraction of wall flow towards bed core.

  17. A constant air flow rate control of blower for residential applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.M. [Tamkang Univ., Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering

    1998-03-01

    This paper presents a technique to control a blower for residential applications at constant air flow rate using an induction motor drive. The control scheme combines a variable volt/hertz ratio inverter drive and an average motor current regulation loop to achieve control of the motor torque-speed characteristics, consequently controlling the air flow rate of the blower which the motor is driving. The controller is simple to implement and practical for commercialization. It is also reliable, since no external pressure or air flow sensor is required. Both a theoretical derivation and an experimental verification for the control scheme are presented in this paper.

  18. Tunable sensor response by voltage-control in biomimetic hair flow sensors

    NARCIS (Netherlands)

    Droogendijk, H.; Krijnen, G.J.M.

    2012-01-01

    We report improvements in detection limit and responsivity of biomimetic hair flow sensors by electrostatic spring-softening (ESS). Applying a DC-bias voltage to our capacitive flow sensors mediates large (80% and more) voltage-controlled electromechanical amplification of the flow signal for freque

  19. Tunable sensor response by voltage-control in biomimetic hair flow sensors

    NARCIS (Netherlands)

    Droogendijk, H.; Krijnen, G.J.M.

    2012-01-01

    We report improvements in detection limit and responsivity of biomimetic hair flow sensors by electrostatic spring-softening (ESS). Applying a DC-bias voltage to our capacitive flow sensors mediates large (80% and more) voltage-controlled electro-mechanical amplification of the flow signal for frequ

  20. Controlling Subsurface Fractures and Fluid Flow: A Basic Research Agenda

    Energy Technology Data Exchange (ETDEWEB)

    Pyrak-Nolte, Laura J [Purdue Univ., West Lafayette, IN (United States); DePaolo, Donald J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Pietraß, Tanja [USDOE Office of Science, Washington, DC (United States)

    2015-05-22

    From beneath the surface of the earth, we currently obtain about 80-percent of the energy our nation consumes each year. In the future we have the potential to generate billions of watts of electrical power from clean, green, geothermal energy sources. Our planet’s subsurface can also serve as a reservoir for storing energy produced from intermittent sources such as wind and solar, and it could provide safe, long-term storage of excess carbon dioxide, energy waste products and other hazardous materials. However, it is impossible to underestimate the complexities of the subsurface world. These complexities challenge our ability to acquire the scientific knowledge needed for the efficient and safe exploitation of its resources. To more effectively harness subsurface resources while mitigating the impacts of developing and using these resources, the U.S. Department of Energy established SubTER – the Subsurface Technology and Engineering RD&D Crosscut team. This DOE multi-office team engaged scientists and engineers from the national laboratories to assess and make recommendations for improving energy-related subsurface engineering. The SubTER team produced a plan with the overall objective of “adaptive control of subsurface fractures and fluid flow.”This plan revolved around four core technological pillars—Intelligent Wellbore Systems that sustain the integrity of the wellbore environment; Subsurface Stress and Induced Seismicity programs that guide and optimize sustainable energy strategies while reducing the risks associated with subsurface injections; Permeability Manipulation studies that improve methods of enhancing, impeding and eliminating fluid flow; and New Subsurface Signals that transform our ability to see into and characterize subsurface systems. The SubTER team developed an extensive R&D plan for advancing technologies within these four core pillars and also identified several areas where new technologies would require additional basic research

  1. Frequency tuning allows flow direction control in microfluidic networks with passive features.

    Science.gov (United States)

    Jain, Rahil; Lutz, Barry

    2017-05-02

    Frequency tuning has emerged as an attractive alternative to conventional pumping techniques in microfluidics. Oscillating (AC) flow driven through a passive valve can be rectified to create steady (DC) flow, and tuning the excitation frequency to the characteristic (resonance) frequency of the underlying microfluidic network allows control of flow magnitude using simple hardware, such as an on-chip piezo buzzer. In this paper, we report that frequency tuning can also be used to control the direction (forward or backward) of the rectified DC flow in a single device. Initially, we observed that certain devices provided DC flow in the "forward" direction expected from previous work with a similar valve geometry, and the maximum DC flow occurred at the same frequency as a prominent peak in the AC flow magnitude, as expected. However, devices of a slightly different geometry provided the DC flow in the opposite direction and at a frequency well below the peak AC flow. Using an equivalent electrical circuit model, we found that the "forward" DC flow occurred at the series resonance frequency (with large AC flow peak), while the "backward" DC flow occurred at a less obvious parallel resonance (a valley in AC flow magnitude). We also observed that the DC flow occurred only when there was a measurable differential in the AC flow magnitude across the valve, and the DC flow direction was from the channel with large AC flow magnitude to that with small AC flow magnitude. Using these observations and the AC flow predictions from the equivalent circuit model, we designed a device with an AC flowrate frequency profile that was expected to allow the DC flow in opposite directions at two distinct frequencies. The fabricated device showed the expected flow reversal at the expected frequencies. This approach expands the flow control toolkit to include both magnitude and direction control in frequency-tuned microfluidic pumps. The work also raises interesting questions about the

  2. Investigation of co-flow jet flow control and its applications

    Science.gov (United States)

    Lefebvre, Alexis M.

    This thesis investigates the performance of co-flow jet (CFJ) flow control and its applications using experimental testing and computational fluid dynamics (CFD) simulations. For a stationary airfoil and wing, CFJ increases the lift coefficient (CL), reduces the drag and may produce thrust at a low angle of attack (AoA). The maximum lift coefficient is substantially increased for a 2D CFJ airfoil and reaches a value of 4.8 at Cmicro = 0.30. The power consumption of the CFJ pump, measured by the power coefficient (Pc), is influenced by a variety of parameters, including the momentum coefficient (C micro ), the AoA, the injection slot location, and the internal cavity configuration. A low Cmicro of 0.04 produces a rather small Pc in the range of 0.01--0.02 while a higher Cmicro rapidly increases the Pc. Due to the stronger leading edge suction effect, increasing the AoA decreases the Pc. That is until the flow is near separation, within about 2°--3° of the stall AoA. An injection slot location within 2%--5% chord from the leading edge very effectively reduces the power coefficient. An internal cavity design with no separation is crucial to minimize the CFJ power consumption. Overall, the CFJ effectiveness is enhanced with an increasing Mach number as long as the flow remains subsonic, typically with free stream Mach number less than 0.4. Two pitching airfoil oscillations with dynamic stall are studied in this thesis, namely the mild dynamic stall and the deep dynamic stall. At Mach 0.3, the CFJ with a relatively low Cmicro of 0.08 removes the mild dynamic stall. Thereby, the time-averaged lift is increased by 32% and the time-averaged drag is decreased by 80%. The resulting time-averaged aerodynamic (L/D)ave, which does not take the pumping power into account, reaches 118.3. When C micro is increased, the time-averaged drag becomes negative, which demonstrates the feasibility of a CFJ to propel helicopter blades using its pump as the only source of power. The deep

  3. Money versus Time: Evaluation of Flow Control in Terms of Energy Consumption and Convenience

    CERN Document Server

    Frohnapfel, Bettina; Quadrio, Maurizio

    2012-01-01

    Flow control with the goal of reducing the skin friction drag on the fluid-solid interface is an active fundamental research area, motivated by its potential for significant energy savings and reduced emissions in the transport sector. Customarily, the performance of drag reduction techniques in internal flows is evaluated under two alternative flow conditions, i.e. at constant mass flow rate or constant pressure gradient. Successful control leads to reduction of drag and pumping power within the former approach, whereas the latter leads to an increase of the mass flow rate and pumping power. In practical applications, however, money and time define the flow control challenge: a compromise between the energy expenditure (money) and the corresponding convenience (flow rate) achieved with that amount of energy has to be reached so as to accomplish a goal which in general depends on the specific application. Based on this idea, we derive two dimensionless parameters which quantify the total energy consumption an...

  4. A congestion line flow control in deregulated power system

    Directory of Open Access Journals (Sweden)

    Venkatarajan Shanmuga Sundaram

    2011-01-01

    Full Text Available Under open access, market-driven transactions have become the new independent decision variables defining the behavior of the power system. The possibility of transmission lines getting over-loaded is relatively more under deregulated operation because different parts of the system are owned by separate companies and in part operated under varying service charges. This paper discusses a two-tier algorithm for correcting the lone overloads in conjunction with the conventional power-flow methods. The method uses line flow sensitivities, which are computed by the East Decoupled Power-flow algorithm and can be adapted for on-line implementation.

  5. Discretionary Information Flow Control for Interaction-Oriented Specifications

    DEFF Research Database (Denmark)

    Lluch Lafuente, Alberto; Nielson, Flemming; Nielson, Hanne Riis

    2015-01-01

    This paper presents an approach to specify and check discretionary information flow properties of concurrent systems. The approach is inspired by the success of the interaction-oriented paradigm to concurrent systems (cf. choreographies, behavioural types, protocols,...) in providing behavioural...... guarantees of global properties such as deadlock-absence. We show how some information flow properties are easier to formalise and check on a global interaction-oriented description of a concurrent system rather than on a local process-oriented description of the components of the system. We use a simple...... choreography description language adapted from the literature of choreographies and session types. We provide a generic method to instrument the semantics with information flow annotations. Policies are used to specify the admissible flows of information. The main contribution of the paper is a sound type...

  6. Active bypass flow control for a seal in a gas turbine engine

    Energy Technology Data Exchange (ETDEWEB)

    Ebert, Todd A.; Kimmel, Keith D.

    2017-03-14

    An active bypass flow control system for controlling bypass compressed air based upon leakage flow of compressed air flowing past an outer balance seal between a stator and rotor of a first stage of a gas turbine in a gas turbine engine is disclosed. The active bypass flow control system is an adjustable system in which one or more metering devices may be used to control the flow of bypass compressed air as the flow of compressed air past the outer balance seal changes over time as the outer balance seal between the rim cavity and the cooling cavity wears In at least one embodiment, the metering device may include an annular ring having at least one metering orifice extending therethrough, whereby alignment of the metering orifice with the outlet may be adjustable to change a cross-sectional area of an opening of aligned portions of the outlet and the metering orifice.

  7. Analysis of Interline Power Flow Controller (IPFC Location in Power Transmission Systems

    Directory of Open Access Journals (Sweden)

    Amir Kahyaei

    2011-07-01

    Full Text Available The Interline Power Flow Controller (IPFC is one of the latest generation Flexible AC Transmission Systems (FACTS controller used to control power flows of multiple transmission lines. The aim of this paper is investigation of the effect of location of IPFC on profile of voltage and real and reactive power flow in transmission lines in power system. This model is incorporated in Newton- Raphson (NR power flow algorithm to study the power flow control in transmission lines in which IPFC is placed. A program in MATLAB/SIMULINK has been written in order to extend conventional NR algorithm based on this model. Numerical results are carried out on a standard power system. The results without and with IPFC for various locations are compared in terms of voltages, active and reactive power flows to demonstrate the performance of the IPFC model.

  8. An iterative method for controlling reactive power flow in boundary transformers

    Energy Technology Data Exchange (ETDEWEB)

    Trigo, Angel L.; Martinez, Jose L.; Riquelme, Jesus; Romero, Esther [Department of Electrical Engineering, University of Seville (Spain)

    2011-02-15

    This paper presents an operational tool designed to help the system operator to control the reactive power flow in transmission-subtransmission boundary transformers. The main objective is to determine the minimum number of control actions necessary to ensure that reactive power flows in transmission/subtransmission transformers remain within limits. The proposed iterative procedure combines the use of a linear programming problem and a load flow tool. The linear programming assumes a linear behaviour between dependent and control variables around an operating point, modelled with sensitivities. Experimental results regarding IEEE systems are provided comparing the performance of the proposed approach with that of a conventional optimal power flow. (author)

  9. The effect of unified power flow controller location in power systems

    Energy Technology Data Exchange (ETDEWEB)

    Tumay, M. [Cukurova University, Baliai-Adana (Turkey). Department of Electrical and Electronic Engineering; Vural, A.M. [Gaziantep University (Turkey). Department of Electrical and Electronic Engineering; Lo, K.L. [University of Strathclyde, Glasgow (United Kingdom). Department of Electrical and Electronic Engineering

    2004-09-01

    The Unified Power Flow Controller (UPFC) is a device that is capable of providing control of voltage magnitude, active and reactive power flows. This paper represents the effect of UPFC location in steady-state analysis and to demonstrate the capabilities of UPFC in controlling active and reactive power flow within any electrical network. In this paper, a complete power injection model of UPFC including both the series injection branch and the shunt exciting branch is derived in rectangular form. An injected power model method is used to represent UPFC in load flow program. Finally, different types of simulation tasks are carried out based on IEEE 30-bus test system. (author)

  10. Controlling Surface Roughness to Enhance Mass Flow Rates in Nanochannels

    Science.gov (United States)

    Zimon, Malgorzata; Emerson, David; Reese, Jason

    2012-11-01

    A very active field of research in fluid mechanics and material science is predicting the behavior of Newtonian fluids flowing over porous media with different wettabilities. Opposite effects have been observed: some state that wall roughness always suppresses fluid-slip, whereas others show that for some cases roughness may reduce the surface friction. In this work, MD simulations were carried out to further investigate physical mechanisms for liquid slip, and factors affecting it. A rough wall was formed by either periodically spaced rectangular protrusions or was represented by a cosine wave. The MD simulations were conducted to study Poiseuille and Couette flow of liquid argon in a nanochannel with hydrophilic kryptonian walls. The effect of wall roughness and interface wettability on the streaming velocity, and the slip-length at the walls, is observed to be significant. Our results show a dependency of mass flow rate on the type of flow and topography of the channel walls. For a fixed magnitude of the driving force, an increase in the mass flow rate, compared to the smooth surface, was observed for the wavy roughness, whereas the opposite effect was observed for Couette flow where a higher slip was obtained for rectangular gaps. The study is funded in the UK by the Engineering and Physical Sciences Research Council.

  11. A low-order model for flow control studies in cylinder wakes

    Science.gov (United States)

    Balasubramanian, Ganapathi; Olinger, David J.; Demetriou, Michael

    1998-11-01

    Control of three-dimensional wake structures behind circular cylinders is investigated using a previously developed coupled map lattice. The map consists of circle map oscillators along the cylinder span coupled by a diffusion model. Our goal is to develop an efficient model for flow control studies in cylinder wakes. Complex vortex shedding patterns, such as vortex dislocations and frequency cells, are observed behind vibrating cables in uniform freestream flows and stationary cylinders in sheared flows. These structures are controlled by the addition of periodic control signals to the forcing term in the map. Discontinuous nonlinear control theory is used to derive the control laws. Parallel shedding is realized for the case of uniform flow and oblique shedding is achieved for sheared inflows. The effectiveness of the discontinuous nonlinear control theory is compared with the previous application of chaos control theory to the coupled map lattice.

  12. Electro-Magnetic Flow Control to Enable Natural Laminar Flow Wings Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This research team has developed a solid-state electromagnetic device that, when embedded along the leading edge of an aircraft wing, can disrupt laminar air flow on...

  13. An electronic flow control system for a variable-rate tree sprayer

    Science.gov (United States)

    Precise modulation of nozzle flow rates is a critical measure to achieve variable-rate spray applications. An electronic flow rate control system accommodating with microprocessors and pulse width modulation (PWM) controlled solenoid valves was designed to manipulate the output of spray nozzles inde...

  14. Numerical Investigation of Flow Control Feasibility with a Trailing Edge Flap

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2014-01-01

    the control system, a standard PID controller is implemented in a finite volume based incompressible flow solver. An immersed boundary method is applied to treat the problem of simulating a deformable airfoil trailing edge. The flow field is solved using a 2D Reynolds averaged Navier-Stokes finite volume...

  15. The Use of Logistics n the Quality Parameters Control System of Material Flow

    Science.gov (United States)

    Karpova, Natalia P.; Toymentseva, Irina A.; Shvetsova, Elena V.; Chichkina, Vera D.; Chubarkova, Elena V.

    2016-01-01

    The relevance of the research problem is conditioned on the need to justify the use of the logistics methodologies in the quality parameters control process of material flows. The goal of the article is to develop theoretical principles and practical recommendations for logistical system control in material flows quality parameters. A leading…

  16. Control-flow analysis of function calls and returns by abstract interpretation

    DEFF Research Database (Denmark)

    Midtgaard, Jan; Jensen, Thomas P.

    2012-01-01

    Abstract interpretation techniques are used to derive a control-flow analysis for a simple higher-order functional language. The analysis approximates the interprocedural control-flow of both function calls and returns in the presence of first-class functions and tail-call optimization. In additi...... a rational reconstruction of a constraint-based CFA from abstract interpretation principles....

  17. Normative regulation of cash flows as information provision of their accounting and control

    OpenAIRE

    TOMCHUK V.V.

    2012-01-01

    The importance of normative and legislative basis of accounting and control of cash flows is considered in the article «Normative regulation of cash flows as information provision of their accounting and control» written by Victor Vasyliyovych Tomchuk from the National Scientific Center «Institute of Agrarian Economics».

  18. CFD simulations of the flow control performance applied for inlet of low drag high-bypass turbofan engine at cross flow regimes

    Science.gov (United States)

    Kursakov, I. A.; Kazhan, E. V.; Lysenkov, A. V.; Savelyev, A. A.

    2016-10-01

    Paper describes the optimization procedure for low cruise drag inlet of high-bypass ratio turbofan engine (HBRE). The critical cross-flow velocity when the flow separation on the lee side of the inlet channel occurs is determined. The effciency of different flow control devices used to improve the flow parameters at inlet section cross flow regime is analyzed. Boundary layer suction, bypass slot and vortex generators are considered. It is shown that flow control devices enlarge the stability range of inlet performance at cross flow regimes.

  19. Review of zero-net-mass-flux jet and its application in separation flow control

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Since the zero-net-mass-flux (ZNMF) jet was first used as a laboratory flow control method in 1990’s, it has attracted much attention. The ZNMF jet has unique features such as compact actuator, no requirement for external air supply, complex piping, etc., and becomes a hot topic research subject in fluid mechanics. This review introduces the state of the art in the development of ZNMF jet in the quiescent fluid, the interaction of the ZNMF jet with the cross flow and its application in the separation flow control. The evolution of the vortex ring/pair and the spacial flow structure of the ZNMF in quicent fluid or cross flow are presented, as well as the key parameter effects. At last, the applications of ZNMF jet in the wake control of the circular cylinder, the separation control on the airfoil and the aerodynamic force or moment control on MAV/UAV are presented.

  20. Review of zero-net-mass-flux jet and its application in separation flow control

    Institute of Scientific and Technical Information of China (English)

    ZHANG PanFeng; WANG JinJun; FENG LiHao

    2008-01-01

    Since the zero-net-mass-flux (ZNMF) jet was first used as a laboratory flow control method in 1990's, it has attracted much attention. The ZNMF jet has unique features such as compact actuator, no requirement for external air supply, complex piping, etc., and becomes a hot topic research subject in fluid mechanics. This review introduces the state of the art in the development of ZNMF jet in the quiescent fluid, the interaction of the ZNMF jet with the cross flow and its application in the separation flow control. The evolution of the vortex ring/pair and the spacial flow structure of the ZNMF in quicent fluid or cross flow are presented, as well as the key parameter effects. At last, the applications of ZNMF jet in the wake control of the circular cylinder, the separation control on the airfoil and the aerodynamic force or moment control on MAV/UAV are presented.

  1. Control of the flow behind a backward-facing step by visual feedback

    CERN Document Server

    Gautier, N

    2013-01-01

    The separated flow downstream a backward-facing step is controlled using visual information for feedback. This is done when looking at the flow from two vantage points. Flow velocity fields are computed in real-time and used to yield inputs to a control loop. This approach to flow control is shown to be able to control the detached flow in the same way as has been done before by using the area of the recirculation region downstream the step as input for a gradient descent optimization scheme. Visual feedback using real-time computations of 2D velocity fields also allows for novel inputs to the feedback scheme. As a proof of concept, the spatially averaged value of the swirling strength is successfully used as input for an automatically tuned PID controller.

  2. Active Flow Control on a Generic Trapezoidal Wing Planform

    Science.gov (United States)

    Wygnanski, Israel; Little, Jesse; Roentsch, Bernhard; Endrikat, Sebastian

    2016-11-01

    Fluidic oscillators are employed to increase the lift and improve longitudinal stability of a generic trapezoidal wing having aspect ratio of 1.15 and taper ratio of 0.27. Actuation is applied along the flap hinge which spans the entire wing and is parallel to the trailing edge. Experiments are conducted at a Reynolds number of 1 . 7 ×106 for a wide range of incidence (-8° o to 24°) and flap deflection angles (0° to 75°). Baseline flow on the deflected flap is directed inboard prior to boundary layer separation, but changes to outboard with increasing incidence and flap deflection. The attached spanwise flow can be redirected using a sparse distribution of fluidic oscillators acting as a fluidic fence. However, the majority of lift enhancement and pitch break improvement is accomplished using a more dense distribution of actuators which attaches separated flow to the flap. Integral force and moment results are supported by surface flow visualization, pressure sensitive paint and PIV which reveal unique flow features such as a hinge vortex analogous to the leading edge vortex on a forward swept wing and the possible existence of an absolute instability in a plane parallel to the highly deflected flap. Supported by U.S. Office of Naval Research (N00014-14-1-0387).

  3. Fluid control in microfluidic devices using a fluid conveyance extension and an absorbent microfluidic flow modulator.

    Science.gov (United States)

    Yuen, Po Ki

    2013-05-07

    This article presents a simple method for controlling fluid in microfluidic devices without the need for valves or pumps. A fluid conveyance extension is fluidly coupled to the enclosed outlet chamber of a microfluidic device. After a fluid is introduced into the microfluidic device and saturates the fluid conveyance extension, a fluid flow in the microfluidic device is generated by contacting an absorbent microfluidic flow modulator with the fluid conveyance extension to absorb the fluid from the fluid conveyance extension through capillary action. Since the fluid in the microfluidic device is fluidly coupled with the fluid conveyance extension and the fluid conveyance extension is fluidly coupled with the absorbent microfluidic flow modulator, the absorption rate of the absorbent microfluidic flow modulator, which is the rate at which the absorbent microfluidic flow modulator absorbs fluid, matches the fluid flow rate in the microfluidic device. Thus, the fluid flow rate in the microfluidic device is set by the absorption rate of the absorbent microfluidic flow modulator. Sheath flow and fluid switching applications are demonstrated using this simple fluid control method without the need for valves or pumps. Also, the ability to control the fluid flow rate in the microfluidic device is demonstrated using absorbent microfluidic flow modulators with various absorbent characteristics and dimensions.

  4. Quadratic models of AC-DC power flow and optimal reactive power flow with HVDC and UPFC controls

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Juan; Yan, Wei; Wen, Lili [The Key Laboratory of High Voltage Engineering and Electrical New Technology, Ministry of Education, Electrical Engineering College of Chongqing University, Chongqing 400030 (China); Li, Wenyuan [British Columbia Transmission Corporation (BCTC), Suite 1100, Four Bentall Center, 1055 Dunsmuir Street, P.O. Box 49260, Vancouver, BC (Canada)

    2008-03-15

    Quadratic models of power flow (PF) and optimal reactive power flow (ORPF) for AC-DC power systems are proposed in the paper. Voltage magnitudes at the two sides of ideal converter transformers are used as additional state variables to build the quadratic models. Effects of converter controls on equality constraints are considered. The quadratic expression of unified power flow controller (UPFC) is also developed and incorporated into the proposed models. The proposed PF model retaining nonlinearity has a better convergence feature and requires less CPU time compared to traditional PF models. The Hessian matrices in the quadratic AC-DC ORPF model are constant and need to be calculated only once in the entire optimization process, which speeds up the calculation greatly. Results obtained from the four IEEE test systems and an actual utility system indicate that the proposed quadratic models achieve a superior performance than conventional models. (author)

  5. Controlling mixing and segregation in time periodic granular flows

    Science.gov (United States)

    Bhattacharya, Tathagata

    Segregation is a major problem for many solids processing industries. Differences in particle size or density can lead to flow-induced segregation. In the present work, we employ the discrete element method (DEM)---one type of particle dynamics (PD) technique---to investigate the mixing and segregation of granular material in some prototypical solid handling devices, such as a rotating drum and chute. In DEM, one calculates the trajectories of individual particles based on Newton's laws of motion by employing suitable contact force models and a collision detection algorithm. Recently, it has been suggested that segregation in particle mixers can be thwarted if the particle flow is inverted at a rate above a critical forcing frequency. Further, it has been hypothesized that, for a rotating drum, the effectiveness of this technique can be linked to the probability distribution of the number of times a particle passes through the flowing layer per rotation of the drum. In the first portion of this work, various configurations of solid mixers are numerically and experimentally studied to investigate the conditions for improved mixing in light of these hypotheses. Besides rotating drums, many studies of granular flow have focused on gravity driven chute flows owing to its practical importance in granular transportation and to the fact that the relative simplicity of this type of flow allows for development and testing of new theories. In this part of the work, we observe the deposition behavior of both mono-sized and polydisperse dry granular materials in an inclined chute flow. The effects of different parameters such as chute angle, particle size, falling height and charge amount on the mass fraction distribution of granular materials after deposition are investigated. The simulation results obtained using DEM are compared with the experimental findings and a high degree of agreement is observed. Tuning of the underlying contact force parameters allows the achievement

  6. CFA2: a Context-Free Approach to Control-Flow Analysis

    CERN Document Server

    Vardoulakis, Dimitrios

    2011-01-01

    In a functional language, the dominant control-flow mechanism is function call and return. Most higher-order flow analyses, including k-CFA, do not handle call and return well: they remember only a bounded number of pending calls because they approximate programs with control-flow graphs. Call/return mismatch introduces precision-degrading spurious control-flow paths and increases the analysis time. We describe CFA2, the first flow analysis with precise call/return matching in the presence of higher-order functions and tail calls. We formulate CFA2 as an abstract interpretation of programs in continuation-passing style and describe a sound and complete summarization algorithm for our abstract semantics. A preliminary evaluation shows that CFA2 gives more accurate data-flow information than 0CFA and 1CFA.

  7. Using artificial intelligence to control fluid flow computations

    Science.gov (United States)

    Gelsey, Andrew

    1992-01-01

    Computational simulation is an essential tool for the prediction of fluid flow. Many powerful simulation programs exist today. However, using these programs to reliably analyze fluid flow and other physical situations requires considerable human effort and expertise to set up a simulation, determine whether the output makes sense, and repeatedly run the simulation with different inputs until a satisfactory result is achieved. Automating this process is not only of considerable practical importance but will also significantly advance basic artificial intelligence (AI) research in reasoning about the physical world.

  8. Control grid motion estimation for efficient application of optical flow

    CERN Document Server

    Zwart, Christine M

    2012-01-01

    Motion estimation is a long-standing cornerstone of image and video processing. Most notably, motion estimation serves as the foundation for many of today's ubiquitous video coding standards including H.264. Motion estimators also play key roles in countless other applications that serve the consumer, industrial, biomedical, and military sectors. Of the many available motion estimation techniques, optical flow is widely regarded as most flexible. The flexibility offered by optical flow is particularly useful for complex registration and interpolation problems, but comes at a considerable compu

  9. Analytical models for flow control in subsonic and supersonic diffusing flow paths using steady blowing and suction

    Science.gov (United States)

    Sarimurat, Mehmet Nasir

    Flow blowing/suction has multiple beneficial effects on the performance of axial flow compressors. In both low speed and high speed compressors a small amount of flow blowing and/or suction can be applied in the region of adverse pressure gradient to control the boundary layer separation and obtain high pressure ratio across the compressor. On the other hand in high speed compressors where a passage shock is present inside the passage, flow blowing/suction can also be used to manage the shock location inside the passage and increase the operating range of the compressor. In the first part of this study, an analytical model based on the integral method for boundary layer with flow blowing in incompressible flows is developed that shows the effect of mass, momentum, velocity magnitude and injection angle of the blowing flow on the behavior of the boundary layer. According to the model the change in the boundary layer momentum thickness across the blowing location is linear function of the momentum of the blowing flow and exponential function of the velocity of the blowing flow. Also if the size of the blowing slot and the velocity of the blown flow are kept constant, when the amount of the blown flow is increased by increasing the blowing angle, there is an "optimum" angle that maximizes the decrease in the momentum thickness across the blowing station. This angle is a function of the velocity ratio and it reaches an asymptotic value of around 40°. The model also shows that the change in the trailing-edge momentum thickness is an exponential function of the change in the momentum thickness across the blowing location. The developed modeled is confirmed for the NACA-65-410 low speed cascade using Computational Fluid Dynamics and a good agreement between the theory and CFD is obtained. In the second part of the thesis a quasi-1D inviscid and compressible flow theory in a converging/diverging flow passage is presented that can predict the amount of flow blowing or

  10. Optical Flow Structure Effects in Children’s Postural Control

    Science.gov (United States)

    Barela, José A.

    2016-01-01

    The aim of this study was to investigate the effect of distance and optic flow structure on visual information and body sway coupling in children and young adults. Thirty children (from 4 to 12 years of age) and 10 young adults stood upright inside of a moving room oscillating at 0.2 Hz, at 0.25 and 1.5 m from the front wall, and under three optical flow conditions (global, central, and peripheral). Effect of distance and optic flow structure on the coupling of visual information and body sway is age-dependent, with 4-year-olds being more affected at 0.25 m distance than older children and adults are. No such difference was observed at 1.5 m from the front wall. Moreover, 4-year-olds’ sway was larger and displayed higher variability. These results suggest that despite being able to accommodate change resulting from varying optic flow conditions, young children have difficulty in dodging stronger visual stimuli. Lastly, difference in sway performance may be due to immature inter-modality sensory reweighting. PMID:27352305

  11. SPIV study of passive flow control on a WT airfoil

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Hansen, Martin Otto Laver; Meyer, Knud Erik

    2010-01-01

    Stereoscopic Particle Image Velocimetry (SPIV) measurements investigating the effect of vortex generators (VGs) on the flow near stall have been carried out in the purpose built LM Glasfiber wind tunnel on a DU 91-W2-250 profile. Measurements have been conducted at Re=0.9*10^6, corresponding...

  12. Controlled generation and use of CO in flow

    DEFF Research Database (Denmark)

    Hansen, Steffen V. F.; Wilson, Zoe E.; Ulven, Trond;

    2016-01-01

    A method for the generation and use of carbon monoxide in flow chemistry has been developed. By using a tube-in-tube reactor, oxalyl chloride can be conveniently and safely hydrolyzed using a NaOH solution to generate CO in the outer stream, which then passes through AF-2400 semi-permeable inner ...

  13. A Simple CPS Transformation of Control-Flow Information

    DEFF Research Database (Denmark)

    Damian, Daniel; Danvy, Olivier

    2002-01-01

    We build on Danvy and Nielsen's first-order program transformation into continuation-passing style (CPS) to design a new CPS transformation of flow information that is simpler and more efficient than what has been presented in previous work. The key to simplicity and efficiency is that our CPS...

  14. Metabolic control of muscle blood flow during exercise in humans

    DEFF Research Database (Denmark)

    Boushel, Robert Christopher

    2003-01-01

    During muscle contraction, several mechanisms regulate blood flow to ensure a close coupling between muscle oxygen delivery and metabolic demand. No single factor has been identified to constitute the primary metabolic regulator, yet there are signal transduction pathways between skeletal muscle...

  15. Electromagnetic control of oscillating flows in a cavity

    NARCIS (Netherlands)

    Kalter, R.

    2015-01-01

    In continuous steel casting, liquid steel flows turbulently through a submerged nozzle into a thin, vertical mould. In the mould the liquid steel is cooled, such that it solidifies and plate steel is formed. On top of the liquid steel in the mould, a slag layer is present and due to the turbulent be

  16. Multiphase Flow Technology Impacts on Thermal Control Systems for Exploration

    Science.gov (United States)

    McQuillen, John; Sankovic, John; Lekan, Jack

    2006-01-01

    The Two-Phase Flow Facility (TPHIFFy) Project focused on bridging the critical knowledge gap by developing and demonstrating critical multiphase fluid products for advanced life support, thermal management and power conversion systems that are required to enable the Vision for Space Exploration. Safety and reliability of future systems will be enhanced by addressing critical microgravity fluid physics issues associated with flow boiling, condensation, phase separation, and system stability. The project included concept development, normal gravity testing, and reduced gravity aircraft flight campaigns, in preparation for the development of a space flight experiment implementation. Data will be utilized to develop predictive models that could be used for system design and operation. A single fluid, two-phase closed thermodynamic loop test bed was designed, assembled and tested. The major components in this test bed include: a boiler, a condenser, a phase separator and a circulating pump. The test loop was instrumented with flow meters, thermocouples, pressure transducers and both high speed and normal speed video cameras. A low boiling point surrogate fluid, FC-72, was selected based on scaling analyses using preliminary designs for operational systems. Preliminary results are presented which include flow regime transitions and some observations regarding system stability.

  17. Design of hydrodynamically confined microfluidics: controlling flow envelope and pressure.

    Science.gov (United States)

    Christ, Kevin V; Turner, Kevin T

    2011-04-21

    Closed-channel microfluidic devices are widely used in a number of chemical and biological applications; however, it is often difficult to interact with samples, such as cells, that are enclosed inside them. Hydrodynamically confined microflows (HCMs) allow microfluidic-type flows to be generated in open liquid environments, such as Petri dishes, thus greatly increasing the flexibility of microfluidic approaches. HCMs have previously been used for protein patterning and selective cell treatment applications, but the underlying fluid mechanics is not fully understood. Here, we examine the effect of device geometry and flow parameters on the properties of the flow envelope and pressure drop of several two-port HCM devices using a combination of experiments and modeling. A three-port device, which allows for different flow envelope shapes to be generated, is also analyzed. The experimental results agree well with the 3-D computational fluid dynamics simulations, with the majority of the measurements within 10% of the simulations. The results presented provide a framework for understanding the fluid mechanics of HCMs and will aid in the design of HCM devices for a broad range of applications.

  18. Control of Low Reynolds Number Flows with Fluid Structure Interactions

    Science.gov (United States)

    2014-02-02

    public release; distribution is unlimited. 27 the direct numerical simulations of Andro and Jacquin [37] for a plunging NACA 0012 airfoil at Re...34Bifurcating Flows of Plunging Airfoils at High Strouhal Numbers," Journal of Fluid Mechanics, Vol. 708, 2012, pp. 349-376. [37] Andro , J.Y

  19. Resource Considerations during Parallel Scheduling of Large Control Flow Dominated Applications

    DEFF Research Database (Denmark)

    Grode, Jesper Nicolai Riis; Madsen, Jan

    1995-01-01

    This paper presents a technique to determine the possible parallelism between different control-structures in large hierarchical Control- and Data-Flow Graphs (CDFGs). The technique is based on a hierarchical bottom-up heuristic, which after resolving data- and control-dependencies between control...

  20. Active Flow Control on Bidirectional Rotors for Tidal MHK Applications

    Energy Technology Data Exchange (ETDEWEB)

    Shiu, Henry [Research Engineer; van Dam, Cornelis P. [Professor

    2013-08-22

    A marine and hydrokinetic (MHK) tidal turbine extracts energy from tidal currents, providing clean, sustainable electricity generation. In general, all MHK conversion technologies are confronted with significant operational hurdles, resulting in both increased capital and operations and maintenance (O&M) costs. To counter these high costs while maintaining reliability, MHK turbine designs can be simplified. Prior study found that a tidal turbine could be cost-effectively simplified by removing blade pitch and rotor/nacelle yaw. Its rotor would run in one direction during ebb and then reverse direction when the current switched to flood. We dubbed such a turbine a bidirectional rotor tidal turbine (BRTT). The bidirectional hydrofoils of a BRTT are less efficient than conventional hydrofoils and capture less energy, but the elimination of the pitch and yaw systems were estimated to reduce levelized cost of energy by 7.8%-9.6%. In this study, we investigated two mechanisms for recapturing some of the performance shortfall of the BRTT. First, we developed a novel set of hydrofoils, designated the yy series, for BRTT application. Second, we investigated the use of active flow control via microtabs. Microtabs are small deployable/retractable tabs, typically located near the leading or trailing edge of an air/hydrofoil with height on the order of the boundary layer thickness (1% - 2% of chord). They deploy approximately perpendicularly to the foil surface and, like gurney flaps and plain flaps, globally affect the aerodynamics of the airfoil. By strategically placing microtabs and selectively deploying them based on the direction of the inflow, performance of a BRTT rotor can be improved while retaining bidirectional operation. The yy foils were computationally designed and analyzed. They exhibited better performance than the baseline bidirectional foil, the ellipse. For example, the yyb07cn-180 had 14.7% higher (l/d)max than an ellipse of equal thickness. The yyb07cn

  1. Control Volume Analysis, Entropy Balance and the Entropy Production in Flow Systems

    OpenAIRE

    Niven, Robert K.; Noack, Bernd R.

    2014-01-01

    This chapter concerns "control volume analysis", the standard engineering tool for the analysis of flow systems, and its application to entropy balance calculations. Firstly, the principles of control volume analysis are enunciated and applied to flows of conserved quantities (e.g. mass, momentum, energy) through a control volume, giving integral (Reynolds transport theorem) and differential forms of the conservation equations. Several definitions of steady state are discussed. The concept of...

  2. Observer-based Controller For Microrobot in Pulsatile Blood Flow

    OpenAIRE

    Sadelli, Lounis; Fruchard, Matthieu; Ferreira, Antoine

    2014-01-01

    International audience; We propose an observer-based controller for a magnetic microrobot immersed in the human vasculature. The drag force depends on the pulsatile blood velocity and specially acts on the microrobot dynamics. In the design of advanced control laws, the blood velocity is usually assumed to be known or set to a constant mean value to achieve the control objectives, whereas the sole robot position is measured. We prove the stability of the proposed observer-based controller com...

  3. Preprogrammed capillarity to passively control system-level sequential and parallel microfluidic flows.

    Science.gov (United States)

    Kim, Sung-Jin; Paczesny, Sophie; Takayama, Shuichi; Kurabayashi, Katsuo

    2013-06-01

    In microfluidics, capillarity-driven solution flow is often beneficial, owing to its inherently spontaneous motion. However, it is commonly perceived that, in an integrated microfluidic system, the passive capillarity control alone can hardly achieve well-controlled sequential and parallel flow of multiple solutions. Despite this common notion, we hereby demonstrate system-level sequential and parallel microfluidic flow processing by fully passive capillarity-driven control. After manual loading of solutions with a pipette, a network of microfluidic channels passively regulates the flow timing of the multiple solution menisci in a sequential and synchronous manner. Also, use of auxiliary channels and preprogramming of inlet-well meniscus pressure and channel fluidic conductance allow for controlling the flow direction of multiple solutions in our microfluidic system. With those components orchestrated in a single device chip, we show preprogrammed flow control of 10 solutions. The demonstrated system-level flow control proves capillarity as a useful means even for sophisticated microfluidic processing without any actively controlled valves and pumps.

  4. Feedback control for unsteady flow and its application to the stochastic Burgers equation

    Science.gov (United States)

    Choi, Haecheon; Temam, Roger; Moin, Parviz; Kim, John

    1993-08-01

    The study applies mathematical methods of control theory to the problem of control of fluid flow with the long-range objective of developing effective methods for the control of turbulent flows. Model problems are employed through the formalism and language of control theory to present the procedure of how to cast the problem of controlling turbulence into a problem in optimal control theory. Methods of calculus of variations through the adjoint state and gradient algorithms are used to present a suboptimal control and feedback procedure for stationary and time-dependent problems. Two types of controls are investigated: distributed and boundary controls. Several cases of both controls are numerically simulated to investigate the performances of the control algorithm. Most cases considered show significant reductions of the costs to be minimized. The dependence of the control algorithm on the time-descretization method is discussed.

  5. AGC of a multi-area power system under deregulated environment using redox flow batteries and interline power flow controller

    Directory of Open Access Journals (Sweden)

    Tulasichandra Sekhar Gorripotu

    2015-12-01

    Full Text Available In this paper, Proportional Integral Derivative with Filter (PIDF is proposed for Automatic Generation Control (AGC of a multi-area power system in deregulated environment. Initially, a two area four units thermal system without any physical constraints is considered and the gains of the PIDF controller are optimized employing Differential Evolution (DE algorithm using ITAE criterion. The superiority of proposed DE optimized PIDF controller over Fuzzy Logic controller is demonstrated. Then, to further improve the system performance, an Interline Power Flow Controller (IPFC is placed in the tie-line and Redox Flow Batteries (RFB is considered in the first area and the controller parameters are tuned. Additionally, to get an accurate insight of the AGC problem, important physical constraints such as Time Delay (TD and Generation Rate Constraints (GRC are considered and the controller parameters are retuned. The performance of proposed controller is evaluated under different operating conditions that take place in a deregulated power market. Further, the proposed approach is extended to a two area six units hydro thermal system. Finally, sensitivity analysis is performed by varying the system parameters and operating load conditions from their nominal values.

  6. Power flow model/calculation for power systems with multiple FACTS controllers

    Energy Technology Data Exchange (ETDEWEB)

    Radman, Ghadir; Raje, Reshma S. [Center for Energy Systems Research, Tennessee Technological University, P.O. Box 5004, Cookeville, Tennessee-38505 (United States)

    2007-10-15

    This paper presents a new procedure for steady state power flow calculation of power systems with multiple flexible AC transmission system (FACTS) controllers. The focus of this paper is to show how the conventional power flow calculation method can systematically be modified to include multiple FACTS controllers. Newton-Raphson method of iterative solution is used for power flow equations in polar coordinate. The impacts of FACTS controllers on power flow is accommodated by adding new entries and modifying some existing entries in the linearized Jacobian equation of the same system with no FACTS controllers. Three major FACTS controllers (STATic synchronous COMpensator (STATCOM), static synchronous series compensator (SSSC), and unified power flow controller (UPFC)) are studied in this paper. STATCOM is modeled in voltage control mode. SSSC controls the active power of the link to which it is connected. The UPFC controls the active and the reactive power flow of the link while maintaining a constant voltage at one of the buses. The modeling approach presented in this paper is tested on the 9-bus western system coordinating council (WSCC) power system and implemented using MATLAB software package. The numerical results show the robust convergence of the presented procedure. (author)

  7. Synthesis of colloidal microgels using oxygen-controlled flow lithography.

    Science.gov (United States)

    An, Harry Z; Eral, H Burak; Chen, Lynna; Chen, Michelle B; Doyle, Patrick S

    2014-10-14

    We report a synthesis approach based on stop-flow lithography (SFL) for fabricating colloidal microparticles with any arbitrary 2D-extruded shape. By modulating the degree of oxygen inhibition during synthesis, we achieved previously unattainable particle sizes. Brownian diffusion of colloidal discs in bulk suggests the out-of-plane dimension can be as small as 0.8 μm, which agrees with confocal microscopy measurements. We measured the hindered diffusion of microdiscs near a solid surface and compared our results to theoretical predictions. These colloidal particles can also flow through physiological microvascular networks formed by endothelial cells undergoing vasculogensis under minimal hydrostatic pressure (∼5 mm H2O). This versatile platform creates future opportunities for on-chip parametric studies of particle geometry effects on particle passage properties, distribution and cellular interactions.

  8. Distributed flow sensing for closed-loop speed control of a flexible fish robot.

    Science.gov (United States)

    Zhang, Feitian; Lagor, Francis D; Yeo, Derrick; Washington, Patrick; Paley, Derek A

    2015-10-23

    Flexibility plays an important role in fish behavior by enabling high maneuverability for predator avoidance and swimming in turbulent flow. This paper presents a novel flexible fish robot equipped with distributed pressure sensors for flow sensing. The body of the robot is molded from soft, hyperelastic material, which provides flexibility. Its Joukowski-foil shape is conducive to modeling the fluid analytically. A quasi-steady potential-flow model is adopted for real-time flow estimation, whereas a discrete-time vortex-shedding flow model is used for higher-fidelity simulation. The dynamics for the flexible fish robot yield a reduced model for one-dimensional swimming. A recursive Bayesian filter assimilates pressure measurements to estimate flow speed, angle of attack, and foil camber. The closed-loop speed-control strategy combines an inverse-mapping feedforward controller based on an average model derived for periodic actuation of angle-of-attack and a proportional-integral feedback controller utilizing the estimated flow information. Simulation and experimental results are presented to show the effectiveness of the estimation and control strategy. The paper provides a systematic approach to distributed flow sensing for closed-loop speed control of a flexible fish robot by regulating the flapping amplitude.

  9. Information flow and controlling in regularization inversion of quantitative remote sensing

    Institute of Scientific and Technical Information of China (English)

    YANG Hua; XU Wangli; ZHAO Hongrui; CHEN Xue; WANG Jindi

    2005-01-01

    In order to minimize uncertainty of the inversed parameters to the largest extent by making full use of the limited information in remote sensing data, it is necessary to understand what the information flow in quantitative remote sensing model inversion is, thus control the information flow. Aiming at this, the paper takes the linear kernel-driven model inversion as an example. At first, the information flow in different inversion methods is calculated and analyzed, then the effect of information flow controlled by multi-stage inversion strategy is studied, finally, an information matrix based on USM is defined to control information flow in inversion. It shows that using Shannon entropy decrease of the inversed parameters can express information flow more properly. Changing the weight of a priori knowledge in inversion or fixing parameters and partitioning datasets in multi-stage inversion strategy can control information flow. In regularization inversion of remote sensing, information matrix based on USM may be a better tool for quantitatively controlling information flow.

  10. Development of an Active Flow Control Technique for an Airplane High-Lift Configuration

    Science.gov (United States)

    Shmilovich, Arvin; Yadlin, Yoram; Dickey, Eric D.; Hartwich, Peter M.; Khodadoust, Abdi

    2017-01-01

    This study focuses on Active Flow Control methods used in conjunction with airplane high-lift systems. The project is motivated by the simplified high-lift system, which offers enhanced airplane performance compared to conventional high-lift systems. Computational simulations are used to guide the implementation of preferred flow control methods, which require a fluidic supply. It is first demonstrated that flow control applied to a high-lift configuration that consists of simple hinge flaps is capable of attaining the performance of the conventional high-lift counterpart. A set of flow control techniques has been subsequently considered to identify promising candidates, where the central requirement is that the mass flow for actuation has to be within available resources onboard. The flow control methods are based on constant blowing, fluidic oscillators, and traverse actuation. The simulations indicate that the traverse actuation offers a substantial reduction in required mass flow, and it is especially effective when the frequency of actuation is consistent with the characteristic time scale of the flow.

  11. Experimental Investigation of Flow Separation Control Using Dielectric Barrier Discharge Plasma Actuators

    Institute of Scientific and Technical Information of China (English)

    LI Gang; NIE Chaoqun; LI Yiming; ZHU Junqiang; XU Yanji

    2008-01-01

    Influence of plasma actuators as a flow separation control device was investigated experimentally.Hump model was used to demonstrate the effect of plasma actuators on external flow separation,while for internal flow separation a set of compressor cascade was adopted.In order to investigate the modification of the flow structure by the plasma actuator,the flow field was examined non-intrusively by particle image velocimetry measurements in the hump model experiment and by a hot film probe in the compressor cascade experiment.The results showed that the plasma actuator could be effective in controlling the flow separation both over the hump and in the compressor cascade when the incoming velocity was low.As the incoming velocity increased,the plasma actuator was less effective. It is urgent to enhance the intensity of the plasma actuator for its better application.Methods to increase the intensity of plasma actuator were also studied.

  12. Numerical Study of Control of Flow Separation Over a Ramp with Nanosecond Plasma Actuator

    Science.gov (United States)

    Zheng, J. G.; Khoo, B. C.; Cui, Y. D.; Zhao, Z. J.; Li, J.

    2016-06-01

    The nanosecond plasma discharge actuator driven by high voltage pulse with typical rise and decay time of several to tens of nanoseconds is emerging as a promising active flow control means in recent years and is being studied intensively. The characterization study reveals that the discharge induced shock wave propagates through ambient air and introduces highly transient perturbation to the flow. On the other hand, the residual heat remaining in the discharge volume may trigger the instability of external flow. In this study, this type of actuator is used to suppress flow separation over a ramp model. Numerical simulation is carried out to investigate the interaction of the discharge induced disturbance with the external flow. It is found that the flow separation region over the ramp can be reduced significantly. Our work may provide some insights into the understanding of the control mechanism of nanosecond pulse actuator.

  13. Particle image velocimetry of active flow control on a compressor cascade

    Energy Technology Data Exchange (ETDEWEB)

    Hecklau, M.; Rennings, R. van; Zander, V.; Nitsche, W. [Technische Universitaet Berlin, Department of Aeronautics and Astronautics, Berlin (Germany); Huppertz, A.; Swoboda, M. [Rolls-Royce Deutschland Ltd. and Co. KG, Dahlewitz (Germany)

    2011-04-15

    AFC (Active Flow Control) experiments have been performed by means of steady and pulsed blowing out of the sidewalls as well as out of the blade's suction surface in a highly loaded compressor cascade. PIV (Particle Image Velocimetry) was used to evaluate the fully three-dimensional internal flow field and the impact of AFC methods. The aim was to observe the secondary flow structures and flow instabilities by PIV, to tune the AFC device operation parameters. This paper summarizes the different PIV measurements performed at the stator cascade to give an overview of the dominant flow features in the passage flow field and to obtain a detailed view of control mechanisms. In addition, a new vortex detection method is presented, based on a 2D-wavelet which is applicable in two-dimensional velocity data fields. (orig.)

  14. Determination of the controlling factors and origins of the bilinear flow from horizontal well transient responses

    Energy Technology Data Exchange (ETDEWEB)

    Baba, A.; Azzouguen, A.; Mazouzi, A. [Sonatrach/AMT/DP, Alger (Algeria); Tiab, D. [Oklahoma Univ., Norman, OK (United States); Aissaoui, K. [Sonatrach/AMT/PED, Alger (Algeria)

    2002-06-01

    Over the last ten years, the most significant technological advance in the petroleum industry has been the development of horizontal well drilling techniques. At intermediate time, linear flow is the dominant flow in the theory of horizontal wells. The analysis of horizontal well tests is being further complicated by the presence of a bilinear flow regime as intermediate time flow during the horizontal well transient behavior. In this study, the authors demonstrate the occurrence of a bilinear flow in horizontal wells as intermediate time flow regime. They also determine the controlling factors and the origins of the bilinear flow. An analogy is established between a horizontal well and a finite conductivity vertical fracture. An equation is developed using the application of the conventional and Tiab's Direct Synthesis (TDST) methods to determine the reservoir and well characteristics of the Hassi-Messaoud field of Algeria. 20 refs., 6 tabs., 9 figs.

  15. Numerical investigation on feedback control of flow around an oscillating hydrofoil by Lorentz force

    Energy Technology Data Exchange (ETDEWEB)

    Liu Zongkai; Zhou Benmou; Liu Huixing; Ji Yanliang; Huang Yadong, E-mail: kfliukai@126.com [Science and Technology on Transient Physics Laboratory, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2013-06-15

    In order to improve the hydrodynamic characteristics of a hydrofoil (NACA0012), this paper investigates an oscillating hydrofoil immersed in seawater (an electrically poorly conducting fluid) with feedback control of electromagnetic force (Lorentz force). This method is used in the iterative process, by forecasting the location of boundary layer separation points and attack angle at the next time step and figuring out the optimal force distribution function based on these parameters, then returns to the current time step and applies the optimal force onto the leeside to control the flow separation. Based on the basic flow governing equations, the flow field structures, lift evolutions and energy consumptions (the input impulse of Lorentz force) have been numerically investigated. Numerical results show that with this control, the flow separation could be fully suppressed. Meanwhile, the lift increases dramatically and oscillation is suppressed successfully. Furthermore, under similar lift improvement and control effects, the feedback control optimal ratio is 72.58%. (paper)

  16. Numerical investigation on feedback control of flow around an oscillating hydrofoil by Lorentz force

    Science.gov (United States)

    Liu, Zong-Kai; Zhou, Ben-Mou; Liu, Hui-Xing; Ji, Yan-Liang; Huang, Ya-Dong

    2013-06-01

    In order to improve the hydrodynamic characteristics of a hydrofoil (NACA0012), this paper investigates an oscillating hydrofoil immersed in seawater (an electrically poorly conducting fluid) with feedback control of electromagnetic force (Lorentz force). This method is used in the iterative process, by forecasting the location of boundary layer separation points and attack angle at the next time step and figuring out the optimal force distribution function based on these parameters, then returns to the current time step and applies the optimal force onto the leeside to control the flow separation. Based on the basic flow governing equations, the flow field structures, lift evolutions and energy consumptions (the input impulse of Lorentz force) have been numerically investigated. Numerical results show that with this control, the flow separation could be fully suppressed. Meanwhile, the lift increases dramatically and oscillation is suppressed successfully. Furthermore, under similar lift improvement and control effects, the feedback control optimal ratio is 72.58%.

  17. Flow field description of the Space Shuttle Vernier reaction control system exhaust plumes

    Science.gov (United States)

    Cerimele, Mary P.; Alred, John W.

    1987-01-01

    The flow field for the Vernier Reaction Control System (VRCS) jets of the Space Shuttle Orbiter has been calculated from the nozzle throat to the far-field region. The calculations involved the use of recently improved rocket engine nozzle/plume codes. The flow field is discussed, and a brief overview of the calculation techniques is presented. In addition, a proposed on-orbit plume measurement experiment, designed to improve future estimations of the Vernier flow field, is addressed.

  18. Performance and Analysis of Reactive Power Compensation by Unified Power Flow Controller

    Directory of Open Access Journals (Sweden)

    Yogita Kumari

    2015-09-01

    Full Text Available The Unified Power Flow Controller (UPFC is the most versatile of the FACTS controllers envisaged so far. The main function of the UPFC is to control the flow of real and reactive power by injection of a voltage in series with the transmission line. Both the magnitude and the phase angle of the voltage can be varied independently. Real and Reactive power flow control can allow for power flow in prescribed routes, loading of transmission lines close to their thermal limits and can be utilized for improving transient and small signal stability of the power system. In this paper UPFC is incorporated in a SMIB (Single Machine Infinite Bus system and the response of SMIB system has been recorded with and without UPFC, thereafter the comparison of both the output has been done. When no UPFC is installed, real and reactive power through the transmission line cannot be controlled. This paper presents control and performance of UPFC intended for installation on that transmission line to control power flow. Installing the UPFC makes it possible to control amount of active power flowing through the line. Simulations are carried out using MATLAB software to validate the performance of the UPFC.

  19. Computational Study of pH-sensitive Hydrogel-based Microfluidic Flow Controllers

    Directory of Open Access Journals (Sweden)

    Jundika C. Kurnia

    2011-08-01

    Full Text Available This computational study investigates the sensing and actuating behavior of a pH-sensitive hydrogel-based microfluidic flow controller. This hydrogel-based flow controller has inherent advantage in its unique stimuli-sensitive properties, removing the need for an external power supply. The predicted swelling behavior the hydrogel is validated with steady-state and transient experiments. We then demonstrate how the model is implemented to study the sensing and actuating behavior of hydrogels for different microfluidic flow channel/hydrogel configurations: e.g., for flow in a T-junction with single and multiple hydrogels. In short, the results suggest that the response of the hydrogel-based flow controller is slow. Therefore, two strategies to improve the response rate of the hydrogels are proposed and demonstrated. Finally, we highlight that the model can be extended to include other stimuli-responsive hydrogels such as thermo-, electric-, and glucose-sensitive hydrogels.

  20. Self-control of traffic lights and vehicle flows in urban road networks

    Science.gov (United States)

    Lämmer, Stefan; Helbing, Dirk

    2008-04-01

    Based on fluid-dynamic and many-particle (car-following) simulations of traffic flows in (urban) networks, we study the problem of coordinating incompatible traffic flows at intersections. Inspired by the observation of self-organized oscillations of pedestrian flows at bottlenecks, we propose a self-organization approach to traffic light control. The problem can be treated as a multi-agent problem with interactions between vehicles and traffic lights. Specifically, our approach assumes a priority-based control of traffic lights by the vehicle flows themselves, taking into account short-sighted anticipation of vehicle flows and platoons. The considered local interactions lead to emergent coordination patterns such as 'green waves' and achieve an efficient, decentralized traffic light control. While the proposed self-control adapts flexibly to local flow conditions and often leads to non-cyclical switching patterns with changing service sequences of different traffic flows, an almost periodic service may evolve under certain conditions and suggests the existence of a spontaneous synchronization of traffic lights despite the varying delays due to variable vehicle queues and travel times. The self-organized traffic light control is based on an optimization and a stabilization rule, each of which performs poorly at high utilizations of the road network, while their proper combination reaches a superior performance. The result is a considerable reduction not only in the average travel times, but also of their variation. Similar control approaches could be applied to the coordination of logistic and production processes.

  1. A Novel Approach to Adaptive Flow Separation Control

    Science.gov (United States)

    2016-09-03

    and Coefficient of Lift 5. Lift Control - Closed Loop Case 1 6. Lift Control - Closed Loop Case 2 7. Lift Control - Closed Loop Case 3 8...One Dimension 13. MPC Convergence Behavior Summary 14. Benchmark Plant Visualization 15. Benchmark Results: beta = 0.2, step tracking 16...non-dimensional lift coefficient . Fig. 3 shows how Z_lift was computed in this research while Fig. 4 shows the close correspondence between Z_lift

  2. Flow structures and sandbar dynamics in a canyon river during a controlled flood, Colorado River, Arizona

    Science.gov (United States)

    Wright, S.A.; Kaplinski, M.

    2011-01-01

    In canyon rivers, debris fan constrictions create rapids and downstream pools characterized by secondary flow structures that are closely linked to channel morphology. In this paper we describe detailed measurements of the three-dimensional flow structure and sandbar dynamics of two pools along the Colorado River in the Grand Canyon during a controlled flood release from Glen Canyon Dam. Results indicate that the pools are characterized by large lateral recirculation zones (eddies) resulting from flow separation downstream from the channel constrictions, as well as helical flow structures in the main channel and eddy. The lateral recirculation zones are low-velocity areas conducive to fine sediment deposition, particularly in the vicinity of the separation and reattachment points and are thus the dominant flow structures controlling sandbar dynamics. The helical flow structures also affect morphology but appear secondary in importance to the lateral eddies. During the controlled flood, sandbars in the separation and reattachment zones at both sites tended to build gradually during the rising limb and peak flow. Deposition in shallow water on the sandbars was accompanied by erosion in deeper water along the sandbar slope at the interface with the main channel. Erosion occurred via rapid mass failures as well as by gradual boundary shear stress driven processes. The flow structures and morphologic links at our study sites are similar to those identified in other river environments, in particular sharply curved meanders and channel confluences where the coexistence of lateral recirculation and helical flows has been documented. Copyright 2011 by the American Geophysical Union.

  3. Sound Control-Flow Graph Extraction for Java Programs with Exceptions

    NARCIS (Netherlands)

    Amighi, A.; de Carvalho Gomes, Pedro; Gurov, Dilian; Huisman, Marieke; Eleftherakis, George; Hinchey, Mike; Holcombe, Mike

    2012-01-01

    We present an algorithm to extract control-flow graphs from Java bytecode, considering exceptional flows. We then establish its correctness: the behavior of the extracted graphs is shown to be a sound over-approximation of the behavior of the original programs. Thus, any temporal safety property

  4. Analysis of the occurrence of flow-induced pulsations in a gas control station

    NARCIS (Netherlands)

    Peters, M.C.A.M.; Riezebos, H.J.

    2001-01-01

    Strong flow-induced pulsations were observed at some measurement and control stations of the major gas transport company in the Netherlands, Gasunie. These resonances occur when the gas flow is passing closed side branches in the system at a sufficiently high velocity. Unsteady vortex shedding at th

  5. Improved coal grinding and fuel flow control in thermal power plants

    DEFF Research Database (Denmark)

    Niemczyk, Piotr; Bendtsen, Jan Dimon

    2011-01-01

    A novel controller for coal circulation and pulverized coal flow in a coal mill is proposed. The design is based on optimal control theory for bilinear systems with additional integral action. The states are estimated from the grinding power consumption and the amount of coal accumulated...... in the mill by employing a special variant of a Luenberger observer. The controller uses the rotating classifier to improve the dynamical performance of the overall system. The proposed controller is compared with a PID-type controller with available pulverized coal flow measurements under nominal conditions...

  6. Sympathetic reflex control of blood flow in human peripheral tissues

    DEFF Research Database (Denmark)

    Henriksen, O

    1991-01-01

    Sympathetic vasoconstrictor reflexes are essential for the maintenance of arterial blood pressure in upright position. It has been generally believed that supraspinal sympathetic vasoconstrictor reflexes elicited by changes in baroreceptor activity play an important role. Recent studies on human...... sympathetic vasoconstrictor reflexes are blocked. Blood flow has been measure by the local 133Xe-technique. The results indicate the presence of spinal as well as supraspinal sympathetic vasoconstrictor reflexes to human peripheral tissues. Especially is emphasized the presence of a local sympathetic veno...

  7. Oscillations and chaos in renal blood flow control

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H

    1993-01-01

    In normotensive, halothane-anesthetized rats, oscillations can be found both in the single-nephron blood flow and in the tubular pressure. Experimental data and computer simulations support the hypothesis that the oscillations are caused by the tubuloglomerular feedback (TGF) mechanism. Model...... studies show that the key parameters determining the stability of the TGF system are the open loop gain of the system and the time delays in the signal transmission through the various components of the feedback loop. Within a broad range of parameters, the system is unstable and has self-sustained stable...

  8. Pick'n'Fix: Capturing Control Flow in Modular Compilers

    DEFF Research Database (Denmark)

    Day, Laurence E.; Bahr, Patrick

    2014-01-01

    We present a modular framework for implementing languages with effects and control structures such as loops and conditionals. This framework enables modular definitions of both syntax and semantics as well as modular implementations of compilers and virtual machines. In order to compile control s...

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

    Science.gov (United States)

    2006-08-01

    Passive vortex control devices such as vortex generators and winglets attach to the wing and require no energy input. Passive vortex control...width. The dynamic test parameters are summarized in Table 2. The composite duty cycle input signal is denoted ( ) ( )ou t u u tδ= + in which ou

  10. Bidirectional control system for energy flow in solar powered flywheel

    Science.gov (United States)

    Nola, Frank J. (Inventor)

    1987-01-01

    An energy storage system for a spacecraft is provided which employs a solar powered flywheel arrangement including a motor/generator which, in different operating modes, drives the flywheel and is driven thereby. A control circuit, including a threshold comparator, senses the output of a solar energy converter, and when a threshold voltage is exceeded thereby indicating the availability of solar power for the spacecraft loads, activates a speed control loop including the motor/generator so as to accelerate the flywheel to a constant speed and thereby store mechanical energy, while also supplying energy from the solar converter to the loads. Under circumstances where solar energy is not available and thus the threshold voltage is not exceeded, the control circuit deactivates the speed control loop and activates a voltage control loop that provides for operation of the motor as a generator so that mechanical energy from the flywheel is converted into electrical energy for supply to the spacecraft loads.

  11. On the properties and mechanisms of microjet arrays in crossflow for the control of flow separation

    Science.gov (United States)

    Fernandez, Erik J.

    By utilizing passive and active methods of flow control, the aerodynamic performance of external and internal components can be greatly improved. Recently however, the benefits of applying active flow control methods to turbomachinery components for improved fuel efficiency, reduced engine size, and greater operational envelope has sparked a renewed interest in some of these flow control techniques. The more attractive of these, is active control in the form of jets in cross flow. With their ability to be turned on and off, as well as their negligible effect on drag when not being actuated, they are well suited for applications such as compressor and turbine blades, engine inlet diffusers, internal engine passages, and general external aerodynamics. This study consists of two parts. The first is the application of active control on a low-pressure turbine (LPT) cascade to determine the effectiveness of microjet actuators on flow separation at relatively low speeds. The second study, motivated by the first, involves a parametric study on a more canonical model to examine the effects of various microjet parameters on the efficacy of separation control and to provide a better understanding of the relevant flow physics governing this control approach. With data obtained from velocity measurements across the wide parametric range, correlations for the growth of the counter-rotating vortex pairs generated by these actuators are deduced. From the information and models obtained throughout the study, basic suggestions for microjet actuator design are presented.

  12. Method and apparatus for controlling the flow rate of mercury in a flow system

    Science.gov (United States)

    Grossman, Mark W.; Speer, Richard

    1991-01-01

    A method for increasing the mercury flow rate to a photochemical mercury enrichment utilizing an entrainment system comprises the steps of passing a carrier gas over a pool of mercury maintained at a first temperature T1, wherein the carrier gas entrains mercury vapor; passing said mercury vapor entrained carrier gas to a second temperature zone T2 having temperature less than T1 to condense said entrained mercury vapor, thereby producing a saturated Hg condition in the carrier gas; and passing said saturated Hg carrier gas to said photochemical enrichment reactor.

  13. Active Fail-Safe Micro-Array Flow Control for Advanced Embedded Propulsion Systems

    Science.gov (United States)

    Anderson, Bernhard H.; Mace, James L.; Mani, Mori

    2009-01-01

    The primary objective of this research effort was to develop and analytically demonstrate enhanced first generation active "fail-safe" hybrid flow-control techniques to simultaneously manage the boundary layer on the vehicle fore-body and to control the secondary flow generated within modern serpentine or embedded inlet S-duct configurations. The enhanced first-generation technique focused on both micro-vanes and micro-ramps highly-integrated with micro -jets to provide nonlinear augmentation for the "strength' or effectiveness of highly-integrated flow control systems. The study focused on the micro -jet mass flow ratio (Wjet/Waip) range from 0.10 to 0.30 percent and jet total pressure ratios (Pjet/Po) from 1.0 to 3.0. The engine bleed airflow range under study represents about a 10 fold decrease in micro -jet airflow than previously required. Therefore, by pre-conditioning, or injecting a very small amount of high-pressure jet flow into the vortex generated by the micro-vane and/or micro-ramp, active flow control is achieved and substantial augmentation of the controlling flow is realized.

  14. The control of self-propelled microjets inside a microchannel with time-varying flow rates

    NARCIS (Netherlands)

    Khalil, Islam S.M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver S.; Misra, Sarthak

    2013-01-01

    We demonstrate the closed-loop motion control of self-propelled microjets inside a fluidic microchannel. The motion control of the microjets is achieved in hydrogen peroxide solution with time-varying flow rates, under the influence of the controlled magnetic fields and the self-propulsion force. Ma

  15. Active Flow Control with Adaptive Design Techniques for Improved Aircraft Safety Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The increased aircraft safety potential of active flow control using synthetic jets - specifically, using synthetic jets on the leading edge of the wing to delay...

  16. Final Report - Investigation of Intermittent Turbulence and Turbulent Structures in the Presence of Controlled Sheared Flows

    Energy Technology Data Exchange (ETDEWEB)

    Gilmore, Mark A. [University of New Mexico

    2013-06-27

    Final Report for grant DE-FG02-06ER54898. The dynamics and generation of intermittent plasma turbulent structures, widely known as "blobs" have been studied in the presence of sheared plasma flows in a controlled laboratory experiment.

  17. Ultra-Low-Power High-Frequency Micro-Vortex Generators for Transonic Flow Control Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Active flow control to prevent or delay boundary layer separation dramatically improves the performance of air vehicles in critical regions of the flight envelope....

  18. DC Voltage Droop Control Implementation in the AC/DC Power Flow Algorithm: Combinational Approach

    DEFF Research Database (Denmark)

    Akhter, F.; Macpherson, D.E.; Harrison, G.P.

    2015-01-01

    In this paper, a combinational AC/DC power flow approach is proposed for the solution of the combined AC/DC network. The unified power flow approach is extended to include DC voltage droop control. In the VSC based MTDC grids, DC droop control is regarded as more advantageous in terms...... of operational flexibility, as more than one VSC station controls the DC link voltage of the MTDC system. This model enables the study of the effects of DC droop control on the power flows of the combined AC/DC system for steady state studies after VSC station outages or transient conditions without needing...... to use its complete dynamic model. Further, the proposed approach can be extended to include multiple AC and DC grids for combined AC/DC power flow analysis. The algorithm is implemented by modifying the MATPOWER based MATACDC program and the results shows that the algorithm works efficiently....

  19. Prediction and Control of Vortex Dominated and Vortex-wake Flows

    Science.gov (United States)

    Kandil, Osama

    1996-01-01

    This report describes the activities and accomplishments under this research grant, including a list of publications and dissertations, produced in the field of prediction and control of vortex dominated and vortex wake flows.

  20. Model of Integration of Material Flow Control System with MES/ERP System via Cloud Computing

    National Research Council Canada - National Science Library

    Peter Peniak

    2014-01-01

    This article deals with a model of application gateway for integration of Material Flow Control System with ERP/MES systems, which are provided by Cloud Computing and Software as Service delivery model...

  1. Applying work flow control in make-to-order job shops

    DEFF Research Database (Denmark)

    Harrod, Steven; Kanet, John J.

    2013-01-01

    This paper considers work flow control within a make-to-order job shop, which in this presentation differs from either a just-in-time (JIT) or make-to-inventory system because finished goods due dates are externally determined and early delivery of finished goods is prohibited. In particular...... an experimental matrix of four work flow controls (uncontrolled, Kanban, CONWIP, and POLCA) and three queuing disciplines (first come first serve, shortest operation processing time, and earliest operation due date). Statistically significant comparisons demonstrate that while shop inventory (partially complete...... orders) is reduced through work flow control, the total inventory of pending, incomplete, and held finished goods orders increases. Further, the choice of queue discipline is far more significant than the choice of work flow control method. This paper contributes a detailed performance analysis...

  2. Dynamic Stall Flow Control Through the Use of a Novel Plasma Based Actuator Technology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Lynntech proposes a novel flow control methodology for airfoils undergoing dynamic stall. Dynamic stall refers to an aerodynamic phenomenon that is experienced by...

  3. Hybrid Active and Passive Control of Vibratory Power Flow in Flexible Isolation System

    Directory of Open Access Journals (Sweden)

    Y.P. Xiong

    2000-01-01

    Full Text Available A hybrid active and passive vibration control strategy is developed to reduce the total power flows from machines, subject to multiple excitations, to supporting flexible structures. The dynamic interactions between machines, controllers, and receiving structures are studied. A force feedback control process governed by a proportional control law is adopted to produce active control forces to cancel the transmitted forces in the mounts. Computational simulations of a simple and a multiple dimensional hybrid vibration isolation system are performed to study the force transmissibility and the total power flows from vibration sources through active and passive isolators to the supporting structures. The investigation focuses on the effects of a hybrid control approach to the reduction of power flow transmissions and the influence of the dynamic characteristics of the control on power flow spectra. The hybrid control mechanism is synthesised from the power flow analysis. Conclusions and control strategies, well supported by numerical simulations, are deduced providing very useful guidelines for hybrid vibration isolation design.

  4. Numerical Modeling of Plasma Actuators for Flow Control

    OpenAIRE

    KOURTZANIDIS, Konstantinos

    2014-01-01

    As aerodynamic flow control still remains one of the top subjects of research in the aerospace scientific world, new ways to perform such a control are being constantly studied. Microwave plasma discharges have been proposed as a mean of a non-intrusive flow control method based on the creation of hot spots of air (via the creation of plasma discharges) which can eventually interact with the external flow and modify its attributes in a beneficial way to the aerodynamic coefficients of the body of i...

  5. Prediction and control of vortex-dominated and vortex-wake flows

    Science.gov (United States)

    Kandil, Osama

    1993-01-01

    This progress report documents the accomplishments achieved in the period from December 1, 1992 until November 30, 1993. These accomplishments include publications, national and international presentations, NASA presentations, and the research group supported under this grant. Topics covered by documents incorporated into this progress report include: active control of asymmetric conical flow using spinning and rotary oscillation; supersonic vortex breakdown over a delta wing in transonic flow; shock-vortex interaction over a 65-degree delta wing in transonic flow; three dimensional supersonic vortex breakdown; numerical simulation and physical aspects of supersonic vortex breakdown; and prediction of asymmetric vortical flows around slender bodies using Navier-Stokes equations.

  6. Analysis of design parameters and flow characteristics of the vortex valve for SIT flow control

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Young Dong; Chang, Moon Hee; Kim, Seong O.; Kim, Young In

    1997-01-01

    This study was performed to provide a technical basis for the development of the vortex valve which will be adopted in Korean Advanced Reactor. The influence of nondimensional and geometrical parameters of the vortex valve were investigated by analyzing the flow field of the vortex chamber, and the performance related parameters were evaluated by utilizing of the published experimental and analytical data. Also the level transients of the stand pipe were investigated by using of the simplified analytical model. In order to obtain the more detailed information on the vortex flow field, three dimensional preliminary analyses for the vortex valve design were conducted by FLUENT code. This study were carried out by using the simplified analytical model of the vortex valve and downstream pipe. However, the detailed analysis on the integrated system of the vortex valve with the as built design data and the required operating conditions should be performed to obtain the more accurate results on the vortex valve behavior. Also the experimental study over a wide range of operating conditions to develop the correlation of the design parameters and the performance verification should be performed for the practical design and engineering applications of the vortex valve. The results of this study can be used as a basic information for the development of the vortex valve design for the SIT of Korean Advanced Reactor. (author). 12 refs., 5 tabs., 33 figs.

  7. Compact Fluidic Actuator Arrays For Flow Control Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective of the proposed research is to design, develop and demonstrate fluidic actuator arrays for aerodynamic separation control and drag reduction....

  8. Compact Fluidic Actuator Arrays for Flow Control Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective of the proposed research is to design, develop and demonstrate fluidic actuator arrays for aerodynamic separation control and drag reduction....

  9. Low Order Empirical Galerkin Models for Feedback Flow Control

    Science.gov (United States)

    Tadmor, Gilead; Noack, Bernd

    2005-11-01

    Model-based feedback control restrictions on model order and complexity stem from several generic considerations: real time computation, the ability to either measure or reliably estimate the state in real time and avoiding sensitivity to noise, uncertainty and numerical ill-conditioning are high on that list. Empirical POD Galerkin models are attractive in the sense that they are simple and (optimally) efficient, but are notoriously fragile, and commonly fail to capture transients and control effects. In this talk we review recent efforts to enhance empirical Galerkin models and make them suitable for feedback design. Enablers include `subgrid' estimation of turbulence and pressure representations, tunable models using modes from multiple operating points, and actuation models. An invariant manifold defines the model's dynamic envelope. It must be respected and can be exploited in observer and control design. These ideas are benchmarked in the cylinder wake system and validated by a systematic DNS investigation of a 3-dimensional Galerkin model of the controlled wake.

  10. Splitting of Traffic Flows to Control Congestion in Special Events

    Directory of Open Access Journals (Sweden)

    Ciro D'Apice

    2011-01-01

    minimized with respect to the same control parameter. The obtained results have been tested by simulations of urban networks. Decongestion effects are also confirmed estimating the time a car needs to cross a fixed route on the network.

  11. Model of Integration of Material Flow Control System with MES/ERP System via Cloud Computing

    Directory of Open Access Journals (Sweden)

    Peter Peniak

    2014-05-01

    Full Text Available This article deals with a model of application gateway for integration of Material Flow Control System with ERP/MES systems, which are provided by Cloud Computing and Software as Service delivery model. The developed gateway interface is supposed to cover fundamental requirements of production systems for customization and real-time control of material flow within manufacturing processes. Designed solution has been tested and evaluated for High Bay Storage system in a real production environment

  12. Fibro-Vascular Coupling in the Control of Cochlear Blood Flow

    OpenAIRE

    Min Dai; Xiaorui Shi

    2011-01-01

    BACKGROUND: Transduction of sound in the cochlea is metabolically demanding. The lateral wall and hair cells are critically vulnerable to hypoxia, especially at high sound levels, and tight control over cochlear blood flow (CBF) is a physiological necessity. Yet despite the importance of CBF for hearing, consensus on what mechanisms are involved has not been obtained. METHODOLOGY/PRINCIPAL FINDINGS: We report on a local control mechanism for regulating inner ear blood flow involving fibrocyte...

  13. Control of 2D Flexible Structures by Confinement of Vibrations and Regulation of Their Energy Flow

    Directory of Open Access Journals (Sweden)

    Fakhreddine Landolsi

    2009-01-01

    Full Text Available In this paper, we investigate the control of 2D flexible structures by vibration confinement and the regulation of their energy flow along prespecified spatial paths. A discretized-model-based feedback strategy, aiming at confining and suppressing simultaneously the vibration, is proposed. It is assumed that the structure consists of parts that are sensitive to vibrations. The control design introduces a new pseudo-modal matrix derived from the computed eigenvectors of the discretized model. Simulations are presented to show the efficacy of the proposed control law. A parametric study is carried out to examine the effects of the different control parameters on the simultaneous confinement and suppression of vibrations. In addition, we conducted a set of simulations to investigate the flow control of vibrational energy during the confinement-suppression process. We found that the energy flow can be regulated via a set of control parameters for different confinement configurations.

  14. Active Vibration Isolation Control: Comparison of Feedback and Feedforward Control Strategies Applied to Coriolis Mass-Flow Meters

    NARCIS (Netherlands)

    van de Ridder, Bert; Hakvoort, Wouter; van Dijk, Johannes

    2015-01-01

    In this paper we describe the design, implementation and results of multi degree of freedom (DOF) active vibration control for a Coriolis mass-flow meter (CMFM). Without vibration control, environmental vibrational disturbances results in nanometre movement of the fluid-conveying tube which causes

  15. Escherichia coli control in a surface flow treatment wetland.

    Science.gov (United States)

    MacIntyre, M E; Warner, B G; Slawson, R M

    2006-06-01

    A field experiment showed that numbers of Escherichia coli declined significantly when floating Lemna spp. plants were removed to create open water areas in a typical newly constructed surface flow treatment wetland in southern Ontario. It is suggested that E. coli declined immediately after Lemna removal because the Lemna was shading the water column from penetration by natural UV radiation, it was providing favourable attachment sites for the E. coli, and it was not allowing effective free exchange of oxygen from surface winds to the water column to maintain high enough dissolved oxygen supplies for predator zooplankton populations. Operators of wetland systems must have the specialized skills required to recognize the cause and the appropriate maintenance requirements to maintain efficient operation of such unconventional systems should E. coli numbers increase during the course of operation.

  16. Liquid metal flow control by DC electromagnetic pumps; Controle de vazao de metais liquidos por bombas eletromagneticas de corrente continua

    Energy Technology Data Exchange (ETDEWEB)

    Borges, Eduardo Madeira; Braz Filho, Francisco Antonio; Guimaraes, Lamartine Nogueira Frutuoso [Instituto de Estudos Avancados (IEAv), Sao Jose dos Campos, SP (Brazil)], e-mail: eduardo@ieav.cta.br, e-mail: fbraz@ieav.cta.br, e-mail: guimarae@ieav.cta.br

    2006-07-01

    The cooling system of high-density thermal power requires fluids of high thermal conductivity, such as liquid metals. Electromagnetic pumps can be used to liquid metal fluid flow control in cooling circuits. The operation of electromagnetic pumps used to flow control is based on Lorentz force. This force can be achieved by magnetic field and electric current interaction, controlled by external independent power supplies. This work presents the electromagnetic pump operational principles, the IEAv development scheme and the BEMC-1 simulation code. The theoretical results of BEMC-1 simulation are compared to electromagnetic pump operation experimental data, validating the BEMC-1 code. This code is used to evaluate the DC electromagnetic pump performance applied to Mercury flow control and others liquid metal such as Sodium, Lead and Bismuth, used in nuclear fast reactors. (author)

  17. Efficient Ionization Investigation for Flow Control and Energy Extraction

    Science.gov (United States)

    Schneider, Steven J.; Kamhawi, Hani; Blankson, Isaiah M.

    2009-01-01

    Nonequilibrium ionization of air by nonthermal means is explored for hypersonic vehicle applications. The method selected for evaluation generates a weakly ionized plasma using pulsed nanosecond, high-voltage discharges sustained by a lower dc voltage. These discharges promise to provide a means of energizing and sustaining electrons in the air while maintaining a nearly constant ion/neutral molecule temperature. This paper explores the use of short approx.5 nsec, high-voltage approx.12 to 22 kV, repetitive (40 to 100 kHz) discharges in generating a weakly ionized gas sustained by a 1 kV dc voltage in dry air at pressures from 10 to 80 torr. Demonstrated lifetimes of the sustainer discharge current approx.10 to 25 msec are over three orders of magnitude longer than the 5 nsec pulse that generates the electrons. This life is adequate for many high speed flows, enabling the possibility of exploiting weakly ionized plasma phenomena in flow-fields such as those in hypersonic inlets, combustors, and nozzles. Results to date are obtained in a volume of plasma between electrodes in a bell jar. The buildup and decay of the visible emission from the pulser excited air is photographed on an ICCD camera with nanosecond resolution and the time constants for visible emission decay are observed to be between 10 to 15 nsec decreasing as pressure increases. The application of the sustainer voltage does not change the visible emission decay time constant. Energy consumption as indicated by power output from the power supplies is 194 to 669 W depending on pulse repetition rate.

  18. Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

    Science.gov (United States)

    Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

    2013-01-01

    Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

  19. ENERGY EFFICIENT FLOW AND LEVEL CONTROL IN A HYDRO POWER PLANT USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    A. Selwin Mich Priyadharson

    2014-01-01

    Full Text Available The main objective and an innovative design of this work is to improve the energy efficiency by controlling the variables flow and level in a hydroelectric power plant using Programmable Logic Control (PLC-Human Machine Interface (HMI and fuzzy logic approach. This project will focus on design and development of flow and level controller for small scale hydro generating units by implementing gate control based on PLC-HMI and Fuzzy Logic Control (FLC. So far there is no other better performing control scheme, with uncomplicated approach, in order to match and satisfy the dynamic changes in load demand. In this project, FLC will be applied to flow and level control for small scale hydro generating units is proposed. A lab scale experimental setup is made-up as prototype model for flow and level control and simulation outputs were achieved, using PLC-HMI based fuzzy controller scheme. The hardware set up is designed with 5 stages in the tank 1 and 2 stages in the tank 2. Based on the outputs of the level sensors from tanks 1 and 2, the ladder logic will perform. B&R Industrial Automation PLC inbuilt with 24 digital inputs and provides 16 potential free outputs is used to perform control action. Finally, the performance of the proposed scheme is evaluated by simulation results by comparing with conventional controllers output using the data collected from the hydroelectric power plant. The merits of the proposed Fuzzy scheme over the conventional method are spotlighted.

  20. CFD Analysis of Thermal Control System Using NX Thermal and Flow

    Science.gov (United States)

    Fortier, C. R.; Harris, M. F. (Editor); McConnell, S. (Editor)

    2014-01-01

    The Thermal Control Subsystem (TCS) is a key part of the Advanced Plant Habitat (APH) for the International Space Station (ISS). The purpose of this subsystem is to provide thermal control, mainly cooling, to the other APH subsystems. One of these subsystems, the Environmental Control Subsystem (ECS), controls the temperature and humidity of the growth chamber (GC) air to optimize the growth of plants in the habitat. The TCS provides thermal control to the ECS with three cold plates, which use Thermoelectric Coolers (TECs) to heat or cool water as needed to control the air temperature in the ECS system. In order to optimize the TCS design, pressure drop and heat transfer analyses were needed. The analysis for this system was performed in Siemens NX Thermal/Flow software (Version 8.5). NX Thermal/Flow has the ability to perform 1D or 3D flow solutions. The 1D flow solver can be used to represent simple geometries, such as pipes and tubes. The 1D flow method also has the ability to simulate either fluid only or fluid and wall regions. The 3D flow solver is similar to other Computational Fluid Dynamic (CFD) software. TCS performance was analyzed using both the 1D and 3D solvers. Each method produced different results, which will be evaluated and discussed.

  1. Modeling of fluid-induced vibrations and identification of hydrodynamic forces on flow control valves

    Institute of Scientific and Technical Information of China (English)

    Samad Mehrzad; Ilgar Javanshir; Ahmad Rahbar Ranji; Seyyed Hadi Taheri

    2015-01-01

    Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.

  2. Automatic system for air flow control in air-tight chambers of the NPP primary circuit

    Energy Technology Data Exchange (ETDEWEB)

    Bersenev, V.L.; Bagautdinov, Z.S.; Panov, S.Yu.

    1985-01-01

    A system for automatic control of air flows is briefly described which is based on a tensometric flow rate sensor. A sensitive element of the sensor, made of paper-based laminate, under the effect of incoming air flow travels, causing a bending of an elastic element, made of stainless steel. The deformation causes changes in the electric resistance of tensoresistors, the degree of a change being proportional to the air flow rate. A 400 Ohm tensoresistor is used in the sensor. Errors in the flow rate measurement using the tensometric sensor does not exceed +-3% even in the low rate air flow range. The system, tested at the Beloyarsk NPP, has shown a high reliability and accuracy of measurements, which permits to recommend it for the use in technological ventilation of NPPs.

  3. Structural optimization of porous media for fast and controlled capillary flows.

    Science.gov (United States)

    Shou, Dahua; Fan, Jintu

    2015-05-01

    A general quantitative model of capillary flow in homogeneous porous media with varying cross-sectional sizes is presented. We optimize the porous structure for the minimization of the penetration time under global constraints. Programmable capillary flows with constant volumetric flow rate and linear evolution of flow distance to time are also obtained. The controlled innovative flow behaviors are derived based on a dynamic competition between capillary force and viscous resistance. A comparison of dynamic transport on the basis of the present design with Washburn's equation is presented. The regulation and maximization of flow velocity in porous materials is significant for a variety of applications including biomedical diagnostics, oil recovery, microfluidic transport, and water management of fabrics.

  4. Cluster-based control of a separating flow over a smoothly contoured ramp

    Science.gov (United States)

    Kaiser, Eurika; Noack, Bernd R.; Spohn, Andreas; Cattafesta, Louis N.; Morzyński, Marek

    2017-01-01

    The ability to manipulate and control fluid flows is of great importance in many scientific and engineering applications. The proposed closed-loop control framework addresses a key issue of model-based control: The actuation effect often results from slow dynamics of strongly nonlinear interactions which the flow reveals at timescales much longer than the prediction horizon of any model. Hence, we employ a probabilistic approach based on a cluster-based discretization of the Liouville equation for the evolution of the probability distribution. 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 a state space discretization using a clustering algorithm which groups kinematically similar flow states into a low number of clusters. The temporal evolution of the probability distribution on this set of clusters is then described by a control-dependent Markov model. This Markov model can be used as predictor for the ergodic probability distribution for a particular control law. This probability distribution approximates the long-term behavior of the original system on which basis the optimal control law is determined. We examine how the approach can be used to improve the open-loop actuation in a separating flow dominated by Kelvin-Helmholtz shedding. For this purpose, the feature space, in which the model is learned, and the admissible control inputs are tailored to strongly oscillatory flows.

  5. Geometric optimization of cross-flow heat exchanger based on dynamic controllability

    Directory of Open Access Journals (Sweden)

    Alotaibi Sorour

    2008-01-01

    Full Text Available The operation of heat exchangers and other thermal equipments in the face of variable loads is usually controlled by manipulating inlet fluid temperatures or mass flow rates, where the controlled variable is usually one of the output temperatures. The aim of this work is to optimize the geometry of a tube with internal flow of water and an external cross-flow of air, based on its controllability characteristics. Controllability is a useful concept both from theoretical and practical perspective since it tells us if a particular output can be controlled by a particular input. This concept can also provide us with information about the easiest operating condition to control a particular output. A transient model of a tube in cross-flow is developed, where an implicit formulation is used for transient numerical solutions. The aspect ratio of the tube is optimized, subject to volume constraints, based on the optimum operation in terms of controllability. The reported optimized aspect ratio, water mass flow rate and controllability are studied for deferent external properties of the tube.

  6. Distributed coordination of power flow controlling devices in transmission systems; Verteilte koordinierte Lastflusssteuerung in elektrischen Energieuebertragungsnetzen

    Energy Technology Data Exchange (ETDEWEB)

    Haeger, Ulf; Rehtanz, Christian [Technische Univ. Dortmund (Germany); Lehnhoff, Sebastian [OFFIS - Institut fuer Informatik, Oldenburg (Germany)

    2011-07-01

    Energy market activities together with an increasing integration of high capacity unpredictable renewable resources (e. g. wind power) pose an increased utilization of electrical transmission networks. In order to eliminate consequential congestions it is necessary to upgrade the grid. Constructing new lines is difficult due to environmental specifications. An alternative is the integration of power flow controllers in order to dynamically redirect power flows. In this paper we present a multi-agent based algorithm that allows for an autonomous distributed coordination of power flow controllers. (orig.)

  7. Analysis of unsteady flow forces acting on the thermowell in a steam turbine control stage

    Science.gov (United States)

    Badur, J.; Kornet, S.; Sławiński, D.; Ziółkowski, P.

    2016-10-01

    In the present paper the phenomenon of unsteady flow forces acting on the thermowell for measuring steam temperature in a steam turbine control stage has been presented. The non-stationarity of fluid acting on the thermowell such as: Strouhal frequency, pressure amplitude, pressure peaks, pressure field, velocity field etc. have been studied analytically and numerically. There have been examined two cases of flow with changing mass flow rate, pressure and temperature in the control stage chamber of a turbine high-pressure cylinder. The problem of entry into resonance by thermowell has been described in the ASME standard PTC19.3 TW-2010 with providing detailed guidelines for thermowell designs.

  8. PASSIVE-ACTIVE CONTROL OF POWER FLOW IN AN ISOLATION SYSTEM MOUNTED ON FLEXIBLE FOUNDATIONS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A general model of flexible isolation systems which involves both the passive and active control factors is established by inserting actuators into an passive isolation system. And the power flow transmission function in such a system as with multi-disturbance, multi-mounts, passive isolators and actuators is deduced. By means of the numerical simulation method, the influence of actuators on power flow transmission characteristic is studied. And as a conclusion, the passive-active synthetic control strategy of power flow is summarized.

  9. Active flow control integrated diffuser (afcid) for increased energy efficiency in variable air volume systems

    Science.gov (United States)

    Van Der Schijff, Hermanus P.

    Variable air volume (VAV) air terminals are designed to save energy by reducing airflow into a given space based on occupancy and required load. Systems are typically designed to operate at peak load, however as load is reduced, performance is compromised due to inadequate throw. As a result, fans are installed to adjust for the losses, negating many of the energy savings. Additionally flow is vectored by the use of vanes, a basic passive type of flow control. An experimental investigation was performed to study the application of flow control on that of a HVAC diffuser using synthetic jets distributed evenly along the diffuser edge parallel to the flow field. The study was conducted on a 1:3 scale typical office space (150 ft2), which included a simulated scale HVAC system supplied by compressed air. Two different jet blowing ratios were investigated for system loads of 60% and 90%. The flow field was established using hot wire anemometry and Particle Image Velocimetry (PIV). This study demonstrates the effectiveness of synthetic jet based active flow control at controlling airflow, showing ability to affect throw parameters for changing flow rates within the test chamber. Vectoring of up to 20% and improvement in jet spread of 200% was demonstrated. The use of such devices has the potential to improve air quality and air distribution in building while simultaneously lowering energy demands of HVAC systems.

  10. Experimental and computational studies of active flow control on a model truck-trailer

    Directory of Open Access Journals (Sweden)

    Jahanmiri Mohsen

    2012-04-01

    Full Text Available Active flow control is probably the most challenging research area in vehicle aerodynamics. Being able to manipulate a flow field in order to achieve desired results beneficial to engineering is the only way to meet today’s demands for competitive and efficient solutions in the automotive industry. The current work studies the flow control on a semi detailed model truck by using detached-eddy simulations and wind tunnel experiments aiming at reducing the aerodynamic drag. This study combines both passive and active flow control applied on the rear end of the trailer. An indigenous fluidic actuator (loudspeaker in cavity with slots is used as a synthetic jet in the experiment. Both experiments and computations demonstrate that the active flow control works successfully and results in flow reattachment to the flaps. The numerical simulations show that the drag coefficient, CD decreased by 3.9% when AFC was activated compared to the baseline case without flaps. The corresponding decrease when AFC was deactivated (with flaps was only 0.7%. The experimental results show a decrease of CD by 3.1% for the case with activated AFC compared to the baseline case. When AFC was deactivated the corresponding decrease in CD was 1.8%. A detailed flow analysis made in computations and experiments is used to explain these results.

  11. A novel feedback control system – Controlling the material flow in deep drawing using distributed blank-holder force

    DEFF Research Database (Denmark)

    Endelt, Benny Ørtoft; Tommerup, Søren; Danckert, Joachim

    2013-01-01

    The performance of a feedback control system is often limited by the quality of the model on which it is based, and often the controller design is based on trial and error due to insufficient modeling capabilities. A framework is proposed where the controller design is based on classical state...... on a deep drawing operation where the objective was to control material flow throughout the part using only spatial information regarding flange draw-in. The control system controls both the magnitude and distribution of the blank-holder force. The methodology proved stable and flexible with respect...

  12. Representing Causality and Reasoning about Controllability of Multi-level Flow-Systems

    DEFF Research Database (Denmark)

    Heussen, Kai; Lind, Morten

    2010-01-01

    -based reasoning about control situations remains a challenge due to the entanglement of process and control systems that co-establish the intended causal structure of a process. Due to this entanglement, reasoning about such systems depends on a coherent representation of control and process. This paper explains...... modeling of controlled processes with multilevelflow models and proposes a new framework for modeling causal influence in multilevel flow models on the basis of a flow/potential analogy. The results are illustrated on examples from the domain of electric power systems....

  13. RESEARCH ON THE PERFORMANCE OF NEW TYPE OF PROPORTIONAL PESSURE AND FLOW CONTROL VALVE

    Institute of Scientific and Technical Information of China (English)

    Quan Long; Ma Jian; Wang Yongjin

    2003-01-01

    A new closed loop flow controlling principle through correcting the valve's opening area while load pressure is changing is carried out. Further more a principle using only one proportional valve to compound control pressure and flow is suggested. By using very simple proportional throttle valve in structure, the functions that five kinds of proportional valves or any two of them combined possess can be complimented. After analyzing, comparing, and testing the dynamic and static characteristics of valve with different controlling principles and main valve structure styles, the optimized structure styles and control methods are achieved.

  14. U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities

    Science.gov (United States)

    Schmit, Ryan

    2010-01-01

    To develop New Flow Control Techniques: a) Knowledge of the Flow Physics with and without control. b) How does Flow Control Effect Flow Physics (What Works to Optimize the Design?). c) Energy or Work Efficiency of the Control Technique (Cost - Risk - Benefit Analysis). d) Supportability, e.g. (size of equipment, computational power, power supply) (Allows Designer to include Flow Control in Plans).

  15. Jugular Venous Flow Abnormalities in Multiple Sclerosis Patients Compared to Normal Controls

    Science.gov (United States)

    Sethi, Sean K.; Utriainen, David T.; Daugherty, Ana M.; Feng, Wei; Hewett, J. Joseph; Raz, Naftali; Haacke, E. Mark

    2014-01-01

    Background To determine if extracranial venous structural and flow abnormalities exist in patients with multiple sclerosis (MS). Methods Magnetic resonance imaging was used to assess the anatomy and function of major veins in the neck in 138 MS patients and 67 healthy controls (HC). Time-of-flight (TOF) MR angiography (MRA) was used to assess stenosis while 2D phase contrast flow quantification (PCFQ) was used to assess flow at the C2/C3 and C5/C6 levels. Venous flow was normalized to the total arterial flow. The MS patients were divided into stenotic and non-stenotic groups based on MRA assessment, and each group was compared to the HC group in anatomy and flow. Results The MS group showed lower normalized internal jugular vein (IJV) blood flow (tIJV/tA) than the HC group (p < 0.001). In the MS group, 72 (52%) evidenced stenosis (ST) while 66 (48%) were non-stenotic (NST). In the HC group, 11 (23%) showed a stenosis while 37 (77%) were non-stenotic. The ST-MS group had lower IJV flow than both HC and NST-MS groups. Conclusion After categorizing the MS population into two groups based upon anatomical stenosis determined from an absolute quantification of IJV cross-section, clear differences in IJV flow between the stenotic MS and HC samples became evident. Despite the unknown etiology of MS, abnormal venous flow was noted in a distinct group of MS patients compared to HC. PMID:25316522

  16. Flow Modification over Rotor Blade with Suction Boundary Layer Control Technique

    Directory of Open Access Journals (Sweden)

    Navneet Kumar

    2016-06-01

    Full Text Available The efficiency of transonic aircraft engines depend upon the performance of compressor rotor. To increase compressor rotors performance flow separation around rotor blades must be delayed and controlled. The aim was to control the flow separation of blades using suction boundary layer control method. Rotor blade has been modelled in designing software CATIA and then a suction surface has been created on blade and then import these geometries to ANSYS-CFX 14.5 for computational analysis of flow around blades. Suction slot has been applied at the trailing edge of suction surface and Shear stress transport model has been used for computational analysis. Two different suction mass flow rates 1 kg/s and 1.5 kg/s have been used here and boundary layer separation effects have been changed and this could be readily seen that the velocity vectors have reattached, preventing the boundary layer separation at the suction surface of the blade.

  17. Installation of a flow control device in an inclined air-curtain fume hood to control wake-induced exposure.

    Science.gov (United States)

    Chen, Jia-Kun

    2016-08-01

    An inclined plate for flow control was installed at the lower edge of the sash of an inclined air-curtain fume hood to reduce the effects of the wake around a worker standing in front of the fume hood. Flow inside the fume hood is controlled by the inclined air-curtain and deflection plates, thereby forming a quad-vortex flow structure. Controlling the face velocity of the fume hood resulted in convex, straight, concave, and attachment flow profiles in the inclined air-curtain. We used the flow visualization and conducted a tracer gas test with a mannequin to determine the performance of two sash geometries, namely, the half-cylinder and inclined plate designs. When the half-cylinder design was used, the tracer gas test registered a high leakage concentration at Vf ≦ 57.1 fpm or less. This concentration occurred at the top of the sash opening, which was close to the breathing zone of the mannequin placed in front of the fume hood. When the inclined plate design was used, the containment was good, with concentrations of 0.002-0.004 ppm, at Vf ≦ 63.0 fpm. Results indicate that an inclined plate effectively reduces the leakage concentration induced by recirculation flow structures that form in the wake of a worker standing in front of an inclined air-curtain fume hood.

  18. Improved Performance of Personalized Ventilation by Control of the Convection Flow around Occupant Body

    DEFF Research Database (Denmark)

    Bolashikov, Zhecho Dimitrov; Melikov, Arsen Krikor; Krenek, Miroslav

    2009-01-01

    This paper reports on methods of control of the free convection flow around human body aiming at improvement of inhaled air quality for occupants at workstations with personalized ventilation (PV). Two methods of control were developed and explored: passive - blocking the free convection developm......This paper reports on methods of control of the free convection flow around human body aiming at improvement of inhaled air quality for occupants at workstations with personalized ventilation (PV). Two methods of control were developed and explored: passive - blocking the free convection...... personalized air was free of it. Tracer gas concentration measurements were used to identify the effect of controlling the free convection flow on inhaled air quality. The use of both methods improved the performance of PV and made it possible to bring more than 90% clean air in inhalation at substantially...

  19. Controlled reattachment in separated flows: a variational approach to recirculation length reduction

    CERN Document Server

    Boujo, E

    2014-01-01

    A variational technique is used to derive analytical expressions for the sensitivity of recirculation length to steady forcing in separated flows. Linear sensitivity analysis is applied to the two-dimensional steady flow past a circular cylinder for Reynolds numbers $40 \\leq Re \\leq 120$, both in the subcritical and supercritical regimes. Regions which are the most sensitive to volume forcing and wall blowing/suction are identified. Control configurations which reduce the recirculation length are designed based on the sensitivity information, in particular small cylinders used as control devices in the wake of the main cylinder, and fluid suction at the cylinder wall. Validation against full non-linear Navier-Stokes calculations shows excellent agreement for small-amplitude control. The linear stability properties of the controlled flow are systematically investigated. At moderate Reynolds numbers, we observe that regions where control reduces the recirculation length correspond to regions where it has a stab...

  20. Microbridge structures for uniform interval control of flowing droplets in microfluidic networks.

    Science.gov (United States)

    Lee, Do-Hyun; Lee, Wonhye; Um, Eujin; Park, Je-Kyun

    2011-09-01

    Precise temporal control of microfluidic droplets such as synchronization and combinatorial pairing of droplets is required to achieve a variety range of chemical and biochemical reactions inside microfluidic networks. Here, we present a facile and robust microfluidic platform enabling uniform interval control of flowing droplets for the precise temporal synchronization and pairing of picoliter droplets with a reagent. By incorporating microbridge structures interconnecting the droplet-carrying channel and the flow control channel, a fluidic pressure drop was derived between the two fluidic channels via the microbridge structures, reordering flowing droplets with a defined uniform interval. Through the adjustment of the control oil flow rate, the droplet intervals were flexibly and precisely adjustable. With this mechanism of droplet spacing, the gelation of the alginate droplets as well as control of the droplet interval was simultaneously achieved by additional control oil flow including calcified oleic acid. In addition, by parallel linking identical microfluidic modules with distinct sample inlet, controlled synchronization and pairing of two distinct droplets were demonstrated. This method is applicable to facilitate and develop many droplet-based microfluidic applications, including biological assay, combinatorial synthesis, and high-throughput screening.

  1. Numerical Simulation of Tip Clearance Flow Passive Control in Axial Turbine

    Institute of Scientific and Technical Information of China (English)

    LI Wei; QIAO Wei-yang; XU Kai-fu; LUO Hua-ling

    2008-01-01

    This paper focuses on the effects of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip, a double squealer tip, a pressure side tip shelf with inclined squealer tip on a double squealer tip, a tip platform extension edge in pressure side and in suction side respectively. A pressure-correction based, 3D Reynolds-averaged Navier-Stokes equations CFD code with Reynolds Stress Model was adopted. The variable specific heat was considered. The detailed tip clearance flow field with different squealer rims was described with the streamline and the velocity vector. Accordingly, the mechanisms of five passive controls were elucidated; the effects of the passive controls on turbine efficiency and tip clearance flow field were illuminated. The results showed that the secondary flow loss near the outer casing including the tip leakage losses and the passage vortex losses could be reduced in all the five passive control methods. The turbine efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine efficiency, and the efficiency increased by 0.215%.

  2. Design and Implementation of Power Flow Control for a novel Dual Input DC-DC Converter

    DEFF Research Database (Denmark)

    Taeed, Fazel; Ouyang, Ziwei; Nymand, Morten

    2014-01-01

    In this paper a control strategy for controlling the power flow from input voltage sources of a novel dual-input dcdc converter to the load is introduced. The converter can be used in renewable energy applications with two independent power sources. Firstly, the operation principle of the converter...... to control the power flow in the converter. The implemented controller in FPGA is low cost and simple. The complete system can be practically used in power management for renewable energy sources....... is outlined; then the control method for adjusting power sharing is proposed. In the next step, the controller is implemented in an FPGA, and then a 350W dual input converter is built to verify operation of the proposed control strategy. The experimental results show the excellent ability of the controller...

  3. Flow-Induced Control of Pattern Formation in Chemical Systems

    Science.gov (United States)

    Berenstein, Igal; Beta, Carsten

    Since Alan Turing's seminal paper in 1952, the study of spatio-temporal patterns that arise in systems of reacting and diffusing components has grown into an immense and vibrant realm of scientific research. This field includes not only chemical systems but spans many areas of science as diverse as cell and developmental biology, ecology, geosciences, or semiconductor physics. For several decades research in this field has concentrated on the vast variety of patterns that can emerge in reaction-diffusion systems and on the underlying instabilities. In the 1990s, stimulated by the pioneering work of Ott, Grebogi and Yorke, control of pattern formation arose as a new topical focus and gradually developed into an entire new field of research. On the one hand, research interests concentrated on control and suppression of undesired dynamical states, in particular on control of chaos. On the other hand, the design and engineering of particular space-time patterns became a major focus in this field that motivates ongoing scientific effort until today...

  4. Flow separation control by using bowed blade in highly loaded turbine cascades

    Institute of Scientific and Technical Information of China (English)

    YAMAMOTO; Atsumasa

    2009-01-01

    Due to the serious flow separations and centralized vortices,there are high secondary losses in highly loaded turbines.It is imperative to find measures to control the flow separation and vortices hence improve the turbine performance.This paper reports our recent progress on flow separation and vor-tices control in highly loaded turbine cascades by using bowed blades.Two sets of highly loaded tur-bine cascades with the turning angles of 113° and 160°,and each with 7 bowed blade angles 0°(straight),±10°,±20° and ±30° were experimentally investigated.Both internal flow field measurement and flow visualization on the blade surfaces were conducted,and the effects of blade bowing on the flow topology,distribution of vorticity and the flow energy loss were discussed.The results show that,for the cascade with the turning angle of 113°,the appropriately positive bow angle could reduce the flow energy loss;whereas for the cascade with the turning angle of 160°,the well selected negative bow angle can give the better aerodynamic performance.

  5. Flow separation control by using bowed blade in highly loaded turbine cascades

    Institute of Scientific and Technical Information of China (English)

    TAN ChunQing; ZHANG HuaLiang; CHEN HaiSheng; DONG XueZhi; ZHAO HongLei; YAMAMOTO Atsumasa

    2009-01-01

    Due to the serious flow separations and centralized vortices, there are high secondary losses in highly loaded turbines. It is imperative to find measures to control the flow separation and vortices hence improve the turbine performance. This paper reports our recent progress on flow separation and vor-tices control in highly loaded turbine cascades by using bowed blades. Two sets of highly loaded tur-bine cascades with the turning angles of 113°and 160°, and each with 7 bowed blade angles 0°(straight),±10°, ±20° and ±30° were experimentally investigated. Both internal flow field measurement and flow visualization on the blade surfaces were conducted, and the effects of blade bowing on the flow topology, distribution of vorticity and the flow energy loss were discussed. The results show that, for the cascade with the turning angle of 113°, the appropriately positive bow angle could reduce the flow energy loss; whereas for the cascade with the turning angle of 160°, the well selected negative bow angle can give the better aerodynamic performance.

  6. Topological analysis of plasma flow control on corner separation in a highly loaded compressor cascade

    Institute of Scientific and Technical Information of China (English)

    Xiao-Hu Zhao; Yun Wu; Ying-Hong Li; Xue-De Wang; Qin Zhao

    2012-01-01

    In this paper,flow behavior and topology structure in a highly loaded compressor cascade with and without plasma aerodynamic actuation (PAA) are investigated.Streamline pattern,total pressure loss coefficient,outlet flow angle and topological analysis are considered to study the effect and mechanism of the plasma flow control on corner separation.Results presented include the boundary layer flow behavior,effects of three types of PAA on separated flows and performance parameters,topology structures and sequences of singular points with and without PAA.Two separation lines,reversed flow and backflow exist on the suction surface.The cross flow on the endwall is an important element for the corner separation.PAA can reduce the undertuming and overturning as well as the total pressure loss,leading to an overall increase of flow turning and enhancement of aerodynamic performance.PAA can change the topology structure,sequences of singular points and their corresponding separation lines.Types Ⅱ and Ⅲ PAA are much more efficient in controlling corner separation and enhancing aerodynamic performances than type Ⅰ.

  7. Generic control flow for the four types of clutch-to-clutch shifts

    Directory of Open Access Journals (Sweden)

    Yunjiang Cheng

    2016-05-01

    Full Text Available It is known that the clutch-to-clutch shifts in both planetary-type automatic transmission and dual clutch transmission can be divided into four types, which are power-on upshift, power-on downshift, power-off upshift, and power-off downshift. In previous studies, many control methods of clutch-to-clutch shifts are analyzed, but the control flows of the four types are different. In this article, the principle of these shifts is analyzed in detail. The concept of oncoming clutch’s torque ability is proposed. A generic control flow is designed, which divides the shift processes of the four types into the same three phases, and the control algorithm in transmission control unit and the calibration process can be simplified. The powertrain system model and the shift controller are established on MATLAB/Simulink platform. The generic control flow is verified by software-in-the-loop simulations. The simulation results show that the proposed generic control flow can control the four types of shifts properly.

  8. Flow mixing inside a control-rod guide tube - Experimental tests and CFD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Angele, Kristian, E-mail: Kristian.Angele@vattenfall.com [Vattenfall Research and Development AB, SE-81426 Aelvkarleby (Sweden); Odemark, Ylva; Cehlin, Mathias; Hemstroem, Bengt; Hoegstroem, Carl-Maikel; Henriksson, Mats [Vattenfall Research and Development AB, SE-81426 Aelvkarleby (Sweden); Tinoco, Hernan; Lindqvist, Hans [Forsmarks Kraftgrupp AB, SE-74203 Oesthammar (Sweden)

    2011-12-15

    This paper covers a combined experimental and computational effort carried out at Vattenfall Research and Development AB in order to study the thermal mixing in the annular region between a top tube and a control-rod stem. The low frequency thermal fluctuations in this region can result in problems with thermal fatigue and have caused cracks in the control-rod stems of several nuclear reactors (). The flow in the vertical annular region formed by the top tube and the control-rod stem is characterized by the mixing of hot bypass flow with cold crud-removal flow. The crud-removal flow is flowing upwards along the control-rod stem, and the warmer bypass flow is entering through eight horizontal holes positioned in the lower part of the guide tube and four holes in the upper part of the top tube, forming jets. Two full-scale models of a control rod, including the control-rod stem and the guide tube, were constructed. The first model, designed to work at atmospheric conditions, was made of Plexiglass, in order to be able to visualize the mixing process, whereas the second one was made of steel to allow for a higher temperature difference between the two flows, and the heating of the top tube. CFD simulations of the case at atmospheric conditions were also carried out. Both the experiments and the simulations showed that the mixing region between the cold crud-removal flow and the warm bypass flow is dominated by large flow structures coming from above. The process is characterized by low frequency, high amplitude temperature fluctuations. The process is basically hydrodynamic, caused by the downward transport of flow structures originated at the upper bypass inlets. The damping thermal effects through buoyancy is of secondary importance, as also the scaling analysis shows, however a slight damping of the temperature fluctuations can be seen due to natural convection due to a pre-heating of the cold crud-removal flow. The comparison between numerical and experimental

  9. Multiphase flow through porous media: an adaptive control volume finite element formulation

    Science.gov (United States)

    Mostaghimi, P.; Tollit, B.; Gorman, G.; Neethling, S.; Pain, C.

    2012-12-01

    Accurate modeling of multiphase flow in porous media is of great importance in a wide range of applications in science and engineering. We have developed a numerical scheme which employs an implicit pressure explicit saturation (IMPES) algorithm for the temporal discretization of the governing equations. The saturation equation is spatially discretized using a node centered control volume method on an unstructured finite element mesh. The face values are determined through an upwind scheme. The pressure equation is spatially discretized using a continuous control volume finite element method (CV-FEM) to achieve consistency with the discrete saturation equation. The numerical simulation is implemented in Fluidity, an open source and general purpose fluid simulator capable of solving a number of different governing equations for fluid flow and accompanying field equations on arbitrary unstructured meshes. The model is verified against the Buckley-Leverett problem where a quasi-analytical solution is available. We discuss the accuracy and the order of convergence of the scheme. We demonstrate the scheme for modeling multiphase flow in a synthetic heterogeneous porous medium along with the use of anisotropic mesh adaptivity to control local solution errors and increase computational efficiency. The adaptive method is also used to simulate two-phase flow in heap leaching, an industrial mining process, where the flow of the leaching solution is gravitationally dominated. Finally we describe the extension of the developed numerical scheme for simulation of flow in multiscale fractured porous media and its capability to model the multiscale characterization of flow in full scale.

  10. Control of fluid flow during Bridgman crystal growth using low-frequency vibrational stirring

    Science.gov (United States)

    Zawilski, Kevin Thomas

    The goal of this research program was to develop an in depth understanding of a promising new method for stirring crystal growth melts called coupled vibrational stirring (CVS). CVS is a mixing technique that can be used in sealed systems and produces rapid mixing through vortex flows. Under normal operating conditions, CVS uses low-frequency vibrations to move the growth crucible along a circular path, producing a surface wave and convection in the melt. This research focused on the application of CVS to the vertical Bridgman technique. CVS generated flows were directly studied using a physical modeling system containing water/glycerin solutions. Sodium nitrate was chosen as a model growth system because the growth process could be directly observed using a transparent furnace. Lead magnesium niobate-lead titanate (PMNT) was chosen as the third system because of its potential application for high performance solid state transducers and actuators. In this study, the critical parameters for controlling CVS flows in cylindrical Bridgman systems were established. One of the most important results obtained was the dependence of an axial velocity gradient on the vibrational frequency. By changing the frequency, the intensity of fluid flow at a given depth can be easily manipulated. The intensity of CVS flows near the crystal-melt interface was found to be important. When flow intensity near the interface increased during growth, large growth rate fluctuations and significant changes in interface shape were observed. To eliminate such fluctuations, a constant flow rate near the crystal-melt interface was maintained by decreasing the vibrational frequency. A continuous frequency ramp was found to be essential to grow crystals of good quality under strong CVS flows. CVS generated flows were also useful in controlling the shape of the growth interface. In the sodium nitrate system without stirring, high growth rates produced a very concave interface. By adjusting the flow

  11. Genetic and environmental influences on the relationship between flow proneness, locus of control and behavioral inhibition.

    Directory of Open Access Journals (Sweden)

    Miriam A Mosing

    Full Text Available Flow is a psychological state of high but subjectively effortless attention that typically occurs during active performance of challenging tasks and is accompanied by a sense of automaticity, high control, low self-awareness, and enjoyment. Flow proneness is associated with traits and behaviors related to low neuroticism such as emotional stability, conscientiousness, active coping, self-esteem and life satisfaction. Little is known about the genetic architecture of flow proneness, behavioral inhibition and locus of control--traits also associated with neuroticism--and their interrelation. Here, we hypothesized that individuals low in behavioral inhibition and with an internal locus of control would be more likely to experience flow and explored the genetic and environmental architecture of the relationship between the three variables. Behavioral inhibition and locus of control was measured in a large population sample of 3,375 full twin pairs and 4,527 single twins, about 26% of whom also scored the flow proneness questionnaire. Findings revealed significant but relatively low correlations between the three traits and moderate heritability estimates of .41, .45, and .30 for flow proneness, behavioral inhibition, and locus of control, respectively, with some indication of non-additive genetic influences. For behavioral inhibition we found significant sex differences in heritability, with females showing a higher estimate including significant non-additive genetic influences, while in males the entire heritability was due to additive genetic variance. We also found a mainly genetically mediated relationship between the three traits, suggesting that individuals who are genetically predisposed to experience flow, show less behavioral inhibition (less anxious and feel that they are in control of their own destiny (internal locus of control. We discuss that some of the genes underlying this relationship may include those influencing the function of

  12. Upland Processes and Controls on September 2013 Debris Flows, Rocky Mountain National Park, Colorado

    Science.gov (United States)

    Patton, A. I.; Rathburn, S. L.; Bilderback, E. L.

    2015-12-01

    The extreme rainstorms that occurred in Colorado in September 2013 initiated numerous debris flows in the northern Front Range. These flows delivered sediment to upland streams, impacted buildings and infrastructure in and near Rocky Mountain National Park (RMNP), and underscored the importance of ongoing hazards in mountainous areas. Slope failures occurred primarily at elevations above 2600 m on south facing slopes >40 degrees. The 2013 failures provide a valuable opportunity to better understand site-specific geomorphic variables that control slope failure in the interior United States and the frequency of debris flows in steep terrain. Slope characteristics including soil depth, vegetation type and prevalence, contributing area, slope convexity/concavity and soil texture were compared between 11 debris flow sites and 30 control sites that did not fail in RMNP. This analysis indicates that slope morphology is the primary controlling factor: 45% of the debris flow sites initiated in or below a colluvial hollow and 36% of the failed sites initiated in other areas of convergent hillslope topography. Only one of the 30 control sites (3%) was located within a colluvial hollow and only two control sites (6%) were located in other areas of convergent topography. Difference in the average maximum soil thickness between debris flow sites (0.9 m) and control sites (0.7 m) is not significant but may reflect the difficulty of using a soil probe in glacially derived soils. Additional research includes field mapping and geochronologic study at one 2013 debris deposit with evidence of multiple mass movements. Preliminary results from the mapping indicate that up to six debris flows have occurred at this site. Radiocarbon analysis of organic material and 10Be analysis of quartz from boulders in old debris levees indicate the timing of past events in this area. Future land management in RMNP will utilize this understanding of controls on slope failure and event frequency.

  13. Controlled Flow Distortion in an Offset Diffuser using Hybrid Trapped Vorticity

    Science.gov (United States)

    Burrows, T. J.; Vukasinovic, B.; Glezer, A.

    2016-11-01

    Trapped vorticity concentration engendered by deliberate modification of the internal surface of an offset diffuser is coupled with a spanwise array of surface-integrated fluidic-oscillating jets for hybrid flow control of streamwise vorticity concentrations that dominate the base flow and give rise to flow distortions at the engine inlet. The local and global characteristics of the diffuser flow in the absence and presence of the actuation are investigated at Mach numbers up to M = 0.7, using surface oil-flow visualization and pressure distributions, and particle image velocimetry. It is shown that two sources of streamwise vorticity dominate the base flow distortion, namely, corner and a central pair of counter-rotating vortices. The present investigations demonstrate that the actuation affects the topology, strength and scale of the trapped vorticity and thereby its coupling to and interaction with the counter rotating streamwise vortices, where the central vortex pair becomes fully suppressed. As a result, the actuation significantly alters the evolution of the flow within the diffuser, and leads to significant suppression of pressure distortion at the engine inlet (by about 80%) at actuation level that is less than 0.7% of the diffuser's mass flow rate. These findings indicate the utility of hybrid trapped vorticity actuation for mitigating adverse effects of secondary vorticity concentrations formed by local separation and corner flows. Supported by ONR.

  14. Numerical study and control method of interaction of nucleation and boundary layer separation in condensing flow

    Institute of Scientific and Technical Information of China (English)

    Liansuo AN; Zhi WANG; Zhonghe HAN

    2009-01-01

    The spontaneous nucleation flow in turbine cascade was numerically studied. The model was imple-mented within a full Navier-Stokes viscous flow solution procedure and the process of condensation was calculated by the quadrature method of moments that shows good accuracy with very broad size distributions.Results were presented for viscous and inviscous flow,showing the influence of boundary layer separation and wake vortices on spontaneous nucleation. The results show that the degree of flow separation in wet steam flow is greater than that in superheated steam flow due to condensation shock and that the loss cannot be neglected.Furthermore, the impact of boundary layer separation and wake vortices on velocity profiles and its implications for profile loss were considered. The calculations showed that layer separation and wake vortices influence nucleation rate, leading to different droplet distributions. A method for controlling homogeneous nucleation and for reducing degree of flow separation in high-speed transonic wet steam flow was presented. The liquid phase parameter distribution is sensitive to the suction side profile of turbine cascade, which impacts the nucleation rate distribution leading to different droplet distributions and affects the degree of flow separation. The numerical study provides a practical design method for turbine blade to reduce wetness losses.

  15. Coordinated power control of unified power flow controller and its application for enhancing dynamic power system performance

    Science.gov (United States)

    Fang, Wanliang

    This thesis focuses on reporting my research study on a problem area relating to use of Unified Power Flow Controller (UPFC) for coordinating load flow in power systems so as to enhance their static and dynamic performance by having more secure and economical operation and higher dynamic stability margin. UPFC is considered as one of the most promising devices for implementing the Flexible AC Transmission System (FACTS) concept. Although development of UPFC is still on an infant stage, probing into its impact on power system operation is actively pursued and significant effort has been devoted to put it forward as a practical FACTS device and as a challenging academic research object. In order to consider UPFC as a basic power system element, it has to be involved in associated load flow computation essentially for power system control analysis and operational planning. An up front problem for design engineers is therefore pointing to a need to modify existing load flow program so as to accommodate interactions of UPFCs. A lot of research output start coming out but their computational efficiency are not high enough. In this regard, I propose two methods to perform the UPFC embedded load flow calculation to cater for two different types of application. The first one caters for analyzing direct control of load flow on transmission lines with embedded UPFCs. In this type of problem, active and reactive power of the lines, as well as the magnitude of bus voltages are priori given. The load flow solution can then be obtained and enables the UPFC parameters to be determined with a significantly improved computational efficiency. The second one works in contrary to the first one by which parameters of UPFCs are given before hand and the load flow calculation is performed for conforming a feasible operation. It can be regarded as an indirect load flow control calculation which is useful in planning stage for incorporating UPFC into existing system and/or carrying out

  16. Flow separation control on swept wing with nanosecond pulse driven DBD plasma actuators

    Directory of Open Access Journals (Sweden)

    Zhao Guangyin

    2015-04-01

    Full Text Available A 15° swept wing with dielectric barrier discharge plasma actuator is designed. Experimental study of flow separation control with nanosecond pulsed plasma actuation is performed at flow velocity up to 40 m/s. The effects of the actuation frequency and voltage on the aerodynamic performance of the swept wing are evaluated by the balanced force and pressure measurements in the wind tunnel. At last, the performances on separation flow control of the three types of actuators with plane and saw-toothed exposed electrodes are compared. The optimal actuation frequency for the flow separation control on the swept wing is detected, namely the reduced frequency is 0.775, which is different from 2-D airfoil separation control. There exists a threshold voltage for the low swept wing flow control. Before the threshold voltage, as the actuation voltage increases, the control effects become better. The maximum lift is increased by 23.1% with the drag decreased by 22.4% at 14°, compared with the base line. However, the best effects are obtained on actuator with plane exposed electrode in the low-speed experiment and the abilities of saw-toothed actuators are expected to be verified under high-speed conditions.

  17. Numerical and Experimental Investigation of Turbulent Transport Control via Shaping of Radial Plasma Flow Profiles

    Energy Technology Data Exchange (ETDEWEB)

    Gilmore, Mark Allen [Univ. of New Mexico, Albuquerque, NM (United States)

    2017-02-05

    Turbulence, and turbulence-driven transport are ubiquitous in magnetically confined plasmas, where there is an intimate relationship between turbulence, transport, instability driving mechanisms (such as gradients), plasma flows, and flow shear. Though many of the detailed physics of the interrelationship between turbulence, transport, drive mechanisms, and flow remain unclear, there have been many demonstrations that transport and/or turbulence can be suppressed or reduced via manipulations of plasma flow profiles. This is well known in magnetic fusion plasmas [e.g., high confinement mode (H-mode) and internal transport barriers (ITB’s)], and has also been demonstrated in laboratory plasmas. However, it may be that the levels of particle transport obtained in such cases [e.g. H-mode, ITB’s] are actually lower than is desirable for a practical fusion device. Ideally, one would be able to actively feedback control the turbulent transport, via manipulation of the flow profiles. The purpose of this research was to investigate the feasibility of using both advanced model-based control algorithms, as well as non-model-based algorithms, to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles. The University of New Mexico was responsible for the experimental portion of the project, while our collaborators at the University of Montana provided plasma transport modeling, and collaborators at Lehigh University developed and explored control methods.

  18. Model Reference Adaptive Control of the Air Flow Rate of Centrifugal Compressor Using State Space Method

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jaeyoung; Jung, Mooncheong; Yu, Sangseok [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Yi, Sun [North Carolina A and T State Univ., Raleigh (United States)

    2016-08-15

    In this study, a model reference adaptive controller is developed to regulate the outlet air flow rate of centrifugal compressor for automotive supercharger. The centrifugal compressor is developed using the analytical based method to predict the transient behavior of operating and the designed model is validated with experimental data to confirm the system accuracy. The model reference adaptive control structure consists of a compressor model and a MRAC(model reference adaptive control) mechanism. The feedback control do not robust with variation of system parameter but the applied adaptive control is robust even if the system parameter is changed. As a result, the MRAC was regulated to reference air flow rate. Also MRAC was found to be more robust control compared with the feedback control even if the system parameter is changed.

  19. Nonlinear output feedback control of underwater vehicle propellers using feedback form estimated axial flow velocity

    DEFF Research Database (Denmark)

    Fossen, T.I.; Blanke, M.

    2000-01-01

    Accurate propeller shaft speed controllers can be designed by using nonlinear control theory and feedback from the axial water velocity in the propeller disc. In this paper, an output feedback controller is derived, reconstructing the axial flow velocity from vehicle speed measurements, using...... a three-state model of propeller shaft speed, forward (surge) speed of the vehicle, and the axial flow velocity. Lyapunov stability theory is used to prove that a nonlinear observer combined with an output feedback integral controller provide exponential stability. The output feedback controller...... compensates for variations in thrust due to time variations in advance speed. This is a major problem when applying conventional vehicle-propeller control systems, The proposed controller is simulated for an underwater vehicle equipped with a single propeller. The simulations demonstrate that the axial water...

  20. Robust and Optimal Control of Magnetic Microparticles inside Fluidic Channels with Time-Varying Flow Rates

    Directory of Open Access Journals (Sweden)

    Islam S.M. Khalil

    2016-06-01

    Full Text Available Targeted therapy using magnetic microparticles and nanoparticles has the potential to mitigate the negative side-effects associated with conventional medical treatment. Major technological challenges still need to be addressed in order to translate these particles into in vivo applications. For example, magnetic particles need to be navigated controllably in vessels against flowing streams of body fluid. This paper describes the motion control of paramagnetic microparticles in the flowing streams of fluidic channels with time-varying flow rates (maximum flow is 35 ml.hr−1. This control is designed using a magnetic-based proportional-derivative (PD control system to compensate for the time-varying flow inside the channels (with width and depth of 2 mm and 1.5 mm, respectively. First, we achieve point-to-point motion control against and along flow rates of 4 ml.hr−1, 6 ml.hr−1, 17 ml.hr−1, and 35 ml.hr−1. The average speeds of single microparticle (with average diameter of 100 μm against flow rates of 6 ml.hr−1 and 30 ml.hr−1 are calculated to be 45 μm.s−1 and 15 μm.s−1, respectively. Second, we implement PD control with disturbance estimation and compensation. This control decreases the steady-state error by 50%, 70%, 73%, and 78% at flow rates of 4 ml.hr−1, 6 ml.hr−1, 17 ml.hr−1, and 35 ml.hr−1, respectively. Finally, we consider the problem of finding the optimal path (minimal kinetic energy between two points using calculus of variation, against the mentioned flow rates. Not only do we find that an optimal path between two collinear points with the direction of maximum flow (middle of the fluidic channel decreases the rise time of the microparticles, but we also decrease the input current that is supplied to the electromagnetic coils by minimizing the kinetic energy of the microparticles, compared to a PD control with disturbance compensation.

  1. Robust and Optimal Control of Magnetic Microparticles Inside Fluidic Channels with Time-varying Flow Rates

    Directory of Open Access Journals (Sweden)

    Islam S.M. Khalil

    2016-06-01

    Full Text Available Targeted therapy using magnetic microparticles and nanoparticles has the potential to mitigate the negative side-effects associated with conventional medical treatment. Major technological challenges still need to be addressed in order to translate these particles into in vivo applications. For example, magnetic particles need to be navigated controllably in vessels against flowing streams of body fluid. This paper describes the motion control of paramagnetic microparticles in the flowing streams of fluidic channels with time-varying flow rates (maximum flow is 35 ml.hr-1. This control is designed using a magnetic-based proportional-derivative (PD control system to compensate for the time-varying flow inside the channels (with width and depth of 2 mm and 1.5 mm, respectively. First, we achieve point-to-point motion control against and along flow rates of 4 ml.hr-1, 6 ml.hr-1, 17 ml.hr-1, and 35 ml.hr-1. The average speeds of single microparticle (with average diameter of 100 μm against flow rates of 6 ml.hr-1 and 30 ml.hr-1 are calculated to be 45 μm.s-1 and 15 μm.s-1, respectively. Second, we implement PD control with disturbance estimation and compensation. This control decreases the steady-state error by 50%, 70%, 73%, and 78% at flow rates of 4 ml.hr-1, 6 ml.hr-1, 17 ml.hr-1, and 35 ml.hr-1, respectively. Finally, we consider the problem of finding the optimal path (minimal kinetic energy between two points using calculus of variation, against the mentioned flow rates. Not only do we find that an optimal path between two collinear points with the direction of maximum flow (middle of the fluidic channel decreases the rise time of the microparticles, but we also decrease the input current that is supplied to the electromagnetic coils by minimizing the kinetic energy of the microparticles, compared to a PD control with disturbance compensation.

  2. A novel feedback control system – Controlling the material flow in deep drawing using distributed blank-holder force

    DEFF Research Database (Denmark)

    Endelt, Benny Ørtoft; Tommerup, Søren; Danckert, Joachim

    2013-01-01

    on a deep drawing operation where the objective was to control material flow throughout the part using only spatial information regarding flange draw-in. The control system controls both the magnitude and distribution of the blank-holder force. The methodology proved stable and flexible with respect......The performance of a feedback control system is often limited by the quality of the model on which it is based, and often the controller design is based on trial and error due to insufficient modeling capabilities. A framework is proposed where the controller design is based on classical state...... space control theory and time series. The system plant has been modeled using non-linear finite element and the gain factors for the control loop were identified by solving the optimal control problem using a non-linear least square optimization algorithm. The proposed design method has been applied...

  3. Control-flow analysis of function calls and returns by abstract interpretation

    DEFF Research Database (Denmark)

    Midtgaard, Jan; Jensen, Thomas P.

    2009-01-01

    We derive a control-flow analysis that approximates the interprocedural control-flow of both function calls and returns in the presence of first-class functions and tail-call optimization. In addition to an abstract environment, our analysis computes for each expression an abstract control stack......, effectively approximating where function calls return across optimized tail calls. The analysis is systematically calculated by abstract interpretation of the stack-based CaEK abstract machine of Flanagan et al. using a series of Galois connections. Abstract interpretation provides a unifying setting in which...

  4. Vibration control of multi-degrees-of-freedom system with dynamic absorbers based on power flow

    Institute of Scientific and Technical Information of China (English)

    WANG Quanjuan; HUANG Wenhua; XIA Songbo; LI Jimin; SUN Zhizhuo

    2003-01-01

    In accordance with a multiple degrees of freedom vibration system with dynamicvibration absorbers (DVAs), an equivalent admittance matrix and the power flows input majorstructure and minor structure are deduced on the basis of the theories of structure mobility.Furthermore, regarding the net power flow of main vibration system as the controlled object,probed into are the single and multiple model controls of multi-degrees-of-freedom system withone or several absorbers attached. And the control mechanism and effect of dynamic vibrationabsorbers are revealed.

  5. Directional flow induced by synchronized longitudinal and zeta-potential controlling AC-electrical fields

    NARCIS (Netherlands)

    Wouden, van der E.J.; Hermes, D.C.; Gardeniers, J.G.E.; Berg, van den A.

    2006-01-01

    Electroosmotic flow (EOF) in a microchannel can be controlled by electronic control of the surface charge using an electrode embedded in the wall of the channel. By setting a voltage to the electrode, the zeta-potential at the wall can be changed locally. Thus, the electrode acts as a "gate" for liq

  6. ANN BASED CONTROL PATTERNS ESTIMATOR FOR UPFC USED IN POWER FLOW PROBLEM

    Directory of Open Access Journals (Sweden)

    K.Krishnaveni

    2007-09-01

    Full Text Available The continuous growth in the demand for electric power necessitates the flexibility of operation in power system. Of different power electronics-based Flexible AC Transmission System (FACTS devices, which enhance the power transmission capabilities, Unified Power Flow Controller (UPFC provides an emerging and promising solution for the power flow problems in the system, as it simultaneously and/or selectively controls the transmission parameters. In this context, the paper proposes the power flow control in a simple system by injecting the series compensating voltage, which is an important function of UPFC. For this purpose, ANN controller based UPFC is used. Control patterns are generated for obtaining the adjustable series voltage from the second converter that, in turn, controls the power flow in the system. With the proposed model, by varying control coefficient the series injected voltage can be adjusted. MATLAB Simulation is used to test the proposed model. The control horizon is identified and presented for various values of existing active and reactive powers.

  7. Spatially distributed control for optimal drag reduction of the flow past a circular cylinder

    Science.gov (United States)

    Poncet, Philippe; Hildebrand, Roland; Cottet, Georges-Henri; Koumoutsakos, Petros

    We report high drag reduction in direct numerical simulations of controlled flows past circular cylinders at Reynolds numbers of 300 and 1000. The flow is controlled by the azimuthal component of the tangential velocity of the cylinder surface. Starting from a spanwise-uniform velocity profile that leads to high drag reduction, the optimization procedure identifies, for the same energy input, spanwise-varying velocity profiles that lead to higher drag reduction. The three-dimensional variations of the velocity field, corresponding to modes A and B of three-dimensional wake instabilities, are largely responsible for this drag reduction. The spanwise wall velocity variations introduce streamwise vortex braids in the wake that are responsible for reducing the drag induced by the primary spanwise vortices shed by the cylinder. The results demonstrate that extending two-dimensional controllers to three-dimensional flows is not optimal as three-dimensional control strategies can lead efficiently to higher drag reduction.

  8. Turbulent Drag Reduction: Studies of Feedback Control and Flow Over Riblets

    Science.gov (United States)

    Choi, Haecheon

    The objective of this study is to explore concepts for control of turbulent boundary layers leading to skin -friction reduction using the direct numerical simulation technique. This report is divided into three parts where three different control methods are investigated; a passive control by longitudinal riblets, an active control by sensing and perturbing structures near the wall, and a feedback control procedure guided by control theory. In PART I significant drag reduction is achieved when the surface boundary condition is modified to suppress the dynamically significant coherent structures present in the wall region. The drag reduction is accompanied with significant reduction in the intensity of the wall -layer structures and reductions in the magnitude of Reynolds shear stress throughout the flow. Two essential drag reduction mechanisms are presented. In PART II mathematical methods of control theory are applied to the problem of control of fluid flow. The procedure of how to cast the problem of controlling turbulence into a problem in optimal control theory is presented through the formalism and language of control theory. Then a suboptimal control and feedback procedure are presented using methods of calculus of variations through the adjoint state and gradient algorithms. This suboptimal feedback control procedure is applied to the distributed and boundary controls of the stochastic Burgers equation. Most cases considered show significant reductions of the costs. In PART III direct numerical simulation is performed to analyze turbulent flow over longitudinal riblets, and to educe the mechanism of drag reduction by riblets. The computed drags on the riblet surfaces are in good agreement with the existing experimental data. Differences in the mean-velocity profile and turbulence quantities are found to be limited to the inner region of the boundary layer. Velocity and vorticity fluctuations as well as the Reynolds shear stresses above the riblets are

  9. Power flow control for transmission networks with implicit modeling of static synchronous series compensator

    DEFF Research Database (Denmark)

    Kamel, S.; Jurado, F.; Chen, Zhe

    2015-01-01

    This paper presents an implicit modeling of Static Synchronous Series Compensator (SSSC) in Newton–Raphson load flow method. The algorithm of load flow is based on the revised current injection formulation. The developed model of SSSC is depended on the current injection approach. In this model......, the voltage source representation of SSSC is transformed to current source, and then this current is injected at the sending and auxiliary buses. These injected currents at the terminals of SSSC are a function of the required line flow and voltage of buses. These currents can be included easily...... to the original mismatches at the terminal buses of SSSC. The developed model can be used to control active and reactive line flow together or individually. The implicit modeling of SSSC device decreases the complexity of load flow code, the modification of Jacobian matrix is avoided, the change only...

  10. Transient stability and control of renewable generators based on Hamiltonian surface shaping and power flow control. Part II, analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Robinett, Rush D., III; Wilson, David Gerald

    2010-11-01

    The swing equations for renewable generators connected to the grid are developed and a wind turbine is used as an example. The swing equations for the renewable generators are formulated as a natural Hamiltonian system with externally applied non-conservative forces. A two-step process referred to as Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) is used to analyze and design feedback controllers for the renewable generators system. This formulation extends previous results on the analytical verification of the Potential Energy Boundary Surface (PEBS) method to nonlinear control analysis and design and justifies the decomposition of the system into conservative and non-conservative systems to enable a two-step, serial analysis and design procedure. The first step is to analyze the system as a conservative natural Hamiltonian system with no externally applied non-conservative forces. The Hamiltonian surface of the swing equations is related to the Equal-Area Criterion and the PEBS method to formulate the nonlinear transient stability problem. This formulation demonstrates the effectiveness of proportional feedback control to expand the stability region. The second step is to analyze the system as natural Hamiltonian system with externally applied non-conservative forces. The time derivative of the Hamiltonian produces the work/rate (power flow) equation which is used to ensure balanced power flows from the renewable generators to the loads. The Second Law of Thermodynamics is applied to the power flow equations to determine the stability boundaries (limit cycles) of the renewable generators system and enable design of feedback controllers that meet stability requirements while maximizing the power generation and flow to the load. Necessary and sufficient conditions for stability of renewable generators systems are determined based on the concepts of Hamiltonian systems, power flow, exergy (the maximum work that can be extracted from an energy flow) rate

  11. Active flow control over a backward-facing step using plasma actuation

    Science.gov (United States)

    Ruisi, R.; Zare-Behtash, H.; Kontis, K.; Erfani, R.

    2016-09-01

    Due to the more stringent aviation regulations on fuel consumption and noise reduction, the interest for smaller and mechanically less complex devices for flow separation control has increased. Plasma actuators are currently among the most studied typology of devices for active flow control purposes due to their small size and lightweight. In this study, a single dielectric barrier discharge (SDBD) actuator is used on a backward-facing step to assess its effects on the separated turbulent shear layer and its reattachment location. A range of actuating modulation frequencies, related to the natural frequencies of shear layer instability (flapping) and vortex shedding instability, are examined. The particle image velocimetry technique is used to analyse the flow over the step and the reattachment location. The bulk-flow experiments show negligible effects both on the shear layer and on the reattachment location for every frequency considered, and the actuator is not able to induce a sufficient velocity increase at the step separation point.

  12. Effects of speed bottleneck on traffic flow with feedback control signal

    Science.gov (United States)

    Zhu, Kangli; Bi, Jiantao; Wu, Jianjun; Li, Shubin

    2016-09-01

    Various car-following models (CMs) have been developed to capture the complex characteristics of microscopic traffic flow, among which the coupled map CM can better reveal and reflect various phenomena of practical traffic flow. Capacity change at bottleneck contributes to high-density traffic flow upstream the bottleneck and contains very complex dynamic behavior. In this paper, we analyze the effect of speed bottleneck on the spatial-temporal evolution characteristics of traffic flow, and propose a method to reduce traffic congestion with the feedback control signal based on CM. Simulation results highlight the potential of using the feedback signal to control the stop-and-go wave and furthermore to alleviate the traffic congestion effectively.

  13. Heavy Class Helicopter Fuselage Model Drag Reduction by Active Flow Control Systems

    Science.gov (United States)

    De Gregorio, F.

    2017-08-01

    A comprehensive experimental investigation of helicopter blunt fuselage drag reduction using active flow control is being carried out within the European Clean Sky program. The objective is to demonstrate the capability of several active flow technologies to decrease fuselage drag by alleviating the flow separation occurring in the rear area of some helicopters. The work is performed on a simplified blunt fuselage at model-scale. Two different flow control actuators are considered for evaluation: steady blowing, unsteady blowing (or pulsed jets). Laboratory tests of each individual actuator are first performed to assess their performance and properties. The fuselage model is then equipped with these actuators distributed in 3 slots located on the ramp bottom edge. This paper addresses the promising results obtained during the wind-tunnel campaign, since significant drag reductions are achieved for a wide range of fuselage angles of attack and yaw angles without detriment of the other aerodynamic characteristics.

  14. A particle-swarm-based approach of power system stability enhancement with unified power flow controller

    Energy Technology Data Exchange (ETDEWEB)

    Al-Awami, Ali T.; Abido, M.A. [Electrical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Box 784 (Saudi Arabia); Abdel-Magid, Y.L. [Electrical Engineering Program, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates)

    2007-03-15

    The use of the supplementary controllers of a unified power flow controller (UPFC) to damp low frequency oscillations in a weakly connected system is investigated. The potential of the UPFC supplementary controllers to enhance the dynamic stability is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. Individual designs of the UPFC controllers and power system stabilizer (PSS) using particle-swarm optimization (PSO) technique are discussed. The effectiveness of the proposed controllers on damping low frequency oscillations is tested through eigenvalue analysis and non-linear time simulation. (author)

  15. Active Flow Control of Lifting Surface With Flap-Current Activities and Future Directions

    Science.gov (United States)

    Ahmadi, G.; Marzocca, P.; Jha, R.; Alstorm, B.; Obied, S.; Kabir, P.; Shahrabi, A.

    2010-01-01

    The main objective is to develop effective control strategies for separation control of an airfoil with a single hinge flap. The specific objectives are: Develop an active control architecture for flow control around an airfoil with flap. Design, fabricate, a wind tunnel test of a high lift wing (with flap) with integrated actuators and sensors. Design, development and fabrication of synthetic jet actuators. Develop appropriate control strategy for application to the airfoil. Wind tunnel testing of the high lift wing at various angles of attack and flap positions with closed loop control.

  16. Reduction Effect Analysis of Erosion Control Facilities Using Debris Flow Numerical Model

    Science.gov (United States)

    Jun, Kyewon; Kim, Younghwan; Oh, Chaeyeon; Lee, Hojin; Kim, SoungDoug

    2017-04-01

    With the increase in frequency of typhoons and heavy rains following the climate change, the scale of damage from the calamities in the mountainous areas has been growing larger and larger, which is different from the past. For the case of Korea where 64% of land is consisted of the mountainous areas, establishment of the check dams has been drastically increased after 2000 in order to reduce the damages from the debris flow. However, due to the lack of data on scale, location and kind of check dams established for reducing the damages in debris flow, the measures to prevent damages based on experience and subjective basis have to be relied on. This study, the high-precision DEM data was structured by using the terrestrial LiDAR in the Jecheon area where the debris flow damage occurred in July 2009. And, from the numerical models of the debris flow, Kanako-2D that is available to reflect the erosion and deposition action was applied to install the erosion control facilities (water channel, check dam) and analyzed the effect of reducing the debris flow shown in the downstream. After installing the erosion control facilities, most of debris flow moves along the water channel to reduce the area to expand the debris flow, and after installing the check dam, the flow depth and flux of the debris flow were reduced along with the erosion. However, even after constructing the erosion control facilities, damages were still inflicted on private residences or agricultural sites located on the upper regions where the deposition was made. Acknowledgments This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2016R1D1A3B03933362)

  17. Effects of Active and Passive Control Techniques on Mach 1.5 Cavity Flow Dynamics

    Directory of Open Access Journals (Sweden)

    Selin Aradag

    2017-01-01

    Full Text Available Supersonic flow over cavities has been of interest since 1960s because cavities represent the bomb bays of aircraft. The flow is transient, turbulent, and complicated. Pressure fluctuations inside the cavity can impede successful weapon release. The objective of this study is to use active and passive control methods on supersonic cavity flow numerically to decrease or eliminate pressure oscillations. Jet blowing at several locations on the front and aft walls of the cavity configuration is used as an active control method. Several techniques are used for passive control including using a cover plate to separate the flow dynamics inside and outside of the cavity, trailing edge wall modifications, such as inclination of the trailing edge, and providing curvature to the trailing edge wall. The results of active and passive control techniques are compared with the baseline case in terms of pressure fluctuations, sound pressure levels at the leading edge, trailing edge walls, and cavity floor and in terms of formation of the flow structures and the results are presented. It is observed from the results that modification of the trailing edge wall is the most effective of the control methods tested leading to up to 40 dB reductions in cavity tones.

  18. A Flow Rate Control Approach on Off-Design Analysis of an Organic Rankine Cycle System

    Directory of Open Access Journals (Sweden)

    Ben-Ran Fu

    2016-09-01

    Full Text Available This study explored effects of off-design heat source temperature (TW,in or flow rate (mW on heat transfer characteristics and performance of an organic Rankine cycle system by controlling the flow rate of working fluid R245fa (i.e., the operation flow rate of R245fa was controlled to ensure that R245fa reached saturation liquid and vapor states at the outlets of the preheater and evaporator, respectively. The results showed that the operation flow rate of R245fa increased with TW,in or mW; higher TW,in or mW yielded better heat transfer performance of the designed preheater and required higher heat capacity of the evaporator; heat transfer characteristics of preheater and evaporator differed for off-design TW,in and mW; and net power output increased with TW,in or mW. The results further indicated that the control strategy should be different for various off-design conditions. Regarding maximum net power output, the flow rate control approach is optimal when TW,in or mW exceeds the design point, but the pressure control approach is better when TW,in or mW is lower than the design point.

  19. Metabolic control of resting hemispheric cerebral blood flow is oxidative, not glycolytic

    OpenAIRE

    Powers, William. J.; Videen, Tom O.; Markham, Joanne; Walter, Vonn; Perlmutter, Joel S.

    2011-01-01

    Although the close regional coupling of resting cerebral blood flow (CBF) with both cerebral metabolic rate of oxygen (CMRO2) and cerebral metabolic rate of glucose (CMRglc) within individuals is well documented, there are few data regarding the coupling between whole brain flow and metabolism among different subjects. To investigate the metabolic control of resting whole brain CBF, we performed multivariate analysis of hemispheric CMRO2, CMRglc, and other covariates as predictors of resting ...

  20. The Effects of Sweeping Jet Actuator Parameters on Flow Separation Control

    Science.gov (United States)

    Koklu, Mehti

    2015-01-01

    A parametric experimental study was performed with sweeping jet actuators (fluidic oscillators) to determine their effectiveness in controlling flow separation on an adverse pressure gradient ramp. Actuator parameters that were investigated include blowing coefficients, operation mode, pitch and spreading angles, streamwise location, aspect ratio, and scale. Surface pressure measurements and surface oil flow visualization were used to characterize the effects of these parameters on the actuator performance. 2D Particle Image Velocimetry measurements of the flow field over the ramp and hot-wire measurements of the actuator's jet flow were also obtained for selective cases. In addition, the sweeping jet actuators were compared to other well-known flow control techniques such as micro-vortex generators, steady blowing, and steady vortex-generating jets. The results confirm that the sweeping jet actuators are more effective than steady blowing and steady vortex-generating jets. The results also suggest that an actuator with a larger spreading angle placed closer to the location where the flow separates provides better performance. For the cases tested, an actuator with an aspect ratio, which is the width/depth of the actuator throat, of 2 was found to be optimal. For a fixed momentum coefficient, decreasing the aspect ratio to 1 produced weaker vortices while increasing the aspect ratio to 4 reduced coverage area. Although scaling down the actuator (based on the throat dimensions) from 0.25 inch x 0.125 inch to 0.15 inch x 0.075 inch resulted in similar flow control performance, scaling down the actuator further to 0.075 inch x 0.0375 inch reduced the actuator efficiency by reducing the coverage area and the amount of mixing in the near-wall region. The results of this study provide insight that can be used to design and select the optimal sweeping jet actuator configuration for flow control applications.

  1. Control volume based modelling in one space dimension of oscillating, compressible flow in reciprocating machines

    DEFF Research Database (Denmark)

    Andersen, Stig Kildegård; Carlsen, Henrik; Thomsen, Per Grove

    2006-01-01

    We present an approach for modelling unsteady, primarily one-dimensional, compressible flow. The conservation laws for mass, energy, and momentum are applied to a staggered mesh of control volumes and loss mechanisms are included directly as extra terms. Heat transfer, flow friction......, and multidimensional effects are calculated using empirical correlations. Transformations of the conservation equations into new variables, artificial dissipation for dissipating acoustic phenomena, and an asymmetric interpolation method for minimising numerical diffusion and non physical temperature oscillations...

  2. Perspective on traffic control: Aspects of freeway control, intersection control and the control of transit flow in the Netherlands

    NARCIS (Netherlands)

    Hakkesteegt, P.

    1988-01-01

    Paper presented at the 1988 TRB Annual Meeting, Washington D.C., USA. The first part of this paper deals with the control and signalling system for motorways, directed to a more efficient use of available road capacity and to the improvement of road safety. The second part gives some insight into th

  3. Numerical simulation of tandem-cylinder noise-reduction using plasma-based flow control

    Science.gov (United States)

    Wang, Meng; Eltaweel, Ahmed; Thomas, Flint; Kozlov, Alexey; Kim, Dongjoo

    2011-11-01

    The noise of low-Mach-number flow over tandem cylinders at ReD = 22 , 000 and its reduction using plasma actuators are simulated numerically to confirm and extend earlier experimental results. The numerical approach is based on large-eddy simulation for the turbulent flow field, a semi-empirical plasma actuation model, and Lighthill's theory for acoustic calculation. Excellent agreement between LES and experimental results is obtained for both the baseline flow and flow with plasma control in terms of wake velocity profiles, turbulence intensity, and frequency spectra of pressure fluctuations on the downstream cylinder. The validated flow-field results allow an accurate acoustic analysis based on Lighthill's equation, which is solved using a boundary-element method. The effectiveness of plasma actuators for reducing noise is demonstrated. In the baseline flow, the acoustic field is dominated by the interaction of the downstream cylinder with the upstream wake. With flow control the interaction noise is reduced drastically through suppression of vortex shedding from the upstream cylinder, and the vortex-shedding noise from the downstream cylinder becomes dominant. The peak sound pressure level is reduced by approximately 15 dB. Supported by NASA Cooperative Agreement NNX07AO09A.

  4. Fracture control of ground water flow and water chemistry in a rock aquitard.

    Science.gov (United States)

    Eaton, Timothy T; Anderson, Mary P; Bradbury, Kenneth R

    2007-01-01

    There are few studies on the hydrogeology of sedimentary rock aquitards although they are important controls in regional ground water flow systems. We formulate and test a three-dimensional (3D) conceptual model of ground water flow and hydrochemistry in a fractured sedimentary rock aquitard to show that flow dynamics within the aquitard are more complex than previously believed. Similar conceptual models, based on regional observations and recently emerging principles of mechanical stratigraphy in heterogeneous sedimentary rocks, have previously been applied only to aquifers, but we show that they are potentially applicable to aquitards. The major elements of this conceptual model, which is based on detailed information from two sites in the Maquoketa Formation in southeastern Wisconsin, include orders of magnitude contrast between hydraulic diffusivity (K/S(s)) of fractured zones and relatively intact aquitard rock matrix, laterally extensive bedding-plane fracture zones extending over distances of over 10 km, very low vertical hydraulic conductivity of thick shale-rich intervals of the aquitard, and a vertical hydraulic head profile controlled by a lateral boundary at the aquitard subcrop, where numerous surface water bodies dominate the shallow aquifer system. Results from a 3D numerical flow model based on this conceptual model are consistent with field observations, which did not fit the typical conceptual model of strictly vertical flow through an aquitard. The 3D flow through an aquitard has implications for predicting ground water flow and for planning and protecting water supplies.

  5. Energy Efficient Thermal Management for Natural Gas Engine Aftertreatment via Active Flow Control

    Energy Technology Data Exchange (ETDEWEB)

    David K. Irick; Ke Nguyen; Vitacheslav Naoumov; Doug Ferguson

    2006-04-01

    The project is focused on the development of an energy efficient aftertreatment system capable of reducing NOx and methane by 90% from lean-burn natural gas engines by applying active exhaust flow control. Compared to conventional passive flow-through reactors, the proposed scheme cuts supplemental energy by 50%-70%. The system consists of a Lean NOx Trap (LNT) system and an oxidation catalyst. Through alternating flow control, a major amount of engine exhaust flows through a large portion of the LNT system in the absorption mode, while a small amount of exhaust goes through a small portion of the LNT system in the regeneration or desulfurization mode. By periodically reversing the exhaust gas flow through the oxidation catalyst, a higher temperature profile is maintained in the catalyst bed resulting in greater efficiency of the oxidation catalyst at lower exhaust temperatures. The project involves conceptual design, theoretical analysis, computer simulation, prototype fabrication, and empirical studies. This report details the progress during the first twelve months of the project. The primary activities have been to develop the bench flow reactor system, develop the computer simulation and modeling of the reverse-flow oxidation catalyst, install the engine into the test cell, and begin design of the LNT system.

  6. Energy Efficient Thermal Management for Natural Gas Engine Aftertreatment via Active Flow Control

    Energy Technology Data Exchange (ETDEWEB)

    David K. Irick; Ke Nguyen; Vitacheslav Naoumov; Doug Ferguson

    2005-04-01

    The project is focused on the development of an energy efficient aftertreatment system capable of reducing NOx and methane by 90% from lean-burn natural gas engines by applying active exhaust flow control. Compared to conventional passive flow-through reactors, the proposed scheme cuts supplemental energy by 50%-70%. The system consists of a Lean NOx Trap (LNT) system and an oxidation catalyst. Through alternating flow control, a major amount of engine exhaust flows through a large portion of the LNT system in the absorption mode, while a small amount of exhaust goes through a small portion of the LNT system in the regeneration or desulfurization mode. By periodically reversing the exhaust gas flow through the oxidation catalyst, a higher temperature profile is maintained in the catalyst bed resulting in greater efficiency of the oxidation catalyst at lower exhaust temperatures. The project involves conceptual design, theoretical analysis, computer simulation, prototype fabrication, and empirical studies. This report details the progress during the first twelve months of the project. The primary activities have been to develop the bench flow reactor system, develop the computer simulation and modeling of the reverse-flow oxidation catalyst, install the engine into the test cell, and begin design of the LNT system.

  7. MODELING AND ANALYSIS OF UNSTEADY FLOW BEHAVIOR IN DEEPWATER CONTROLLED MUD-CAP DRILLING

    Directory of Open Access Journals (Sweden)

    Jiwei Li

    Full Text Available Abstract A new mathematical model was developed in this study to simulate the unsteady flow in controlled mud-cap drilling systems. The model can predict the time-dependent flow inside the drill string and annulus after a circulation break. This model consists of the continuity and momentum equations solved using the explicit Euler method. The model considers both Newtonian and non-Newtonian fluids flowing inside the drill string and annular space. The model predicts the transient flow velocity of mud, the equilibrium time, and the change in the bottom hole pressure (BHP during the unsteady flow. The model was verified using data from U-tube flow experiments reported in the literature. The result shows that the model is accurate, with a maximum average error of 3.56% for the velocity prediction. Together with the measured data, the computed transient flow behavior can be used to better detect well kick and a loss of circulation after the mud pump is shut down. The model sensitivity analysis show that the water depth, mud density and drill string size are the three major factors affecting the fluctuation of the BHP after a circulation break. These factors should be carefully examined in well design and drilling operations to minimize BHP fluctuation and well kick. This study provides the fundamentals for designing a safe system in controlled mud-cap drilling operati.

  8. Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow

    DEFF Research Database (Denmark)

    Pedersen, Simon; Løhndorf, Petar Durdevic; Yang, Zhenyu

    2014-01-01

    The severe slugging flow is always challenging in oil & gas production, especially for the current offshore based production. The slugging flow can cause a lot of potential problems, such as those relevant to production safety, fatigue as well as capability. As one typical phenomenon in multi......-phase flow dynamics, the slug can be avoided or eliminated by proper facility design and control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key...

  9. Integrated Channel Selector for Directing Fluid Flow Using Thermoreversible Gelation Controlled by a Digital Mirror Device

    Directory of Open Access Journals (Sweden)

    Yoshitaka Shirasaki

    2013-01-01

    Full Text Available An integrated channel selector system employing thermoreversible gelation of a polymer was developed. Here, we show a system with 3×3 arrayed microchannels having nine crossing points. Infrared laser irradiation was used to form gel areas at several crossing points in arranging a flow path from the inlet to one of the nine outlets passing through certain junctions and channels. The multipoint irradiation by the infrared laser was realized using a personal-computer-controlled digital mirror device. The system was demonstrated to be able to direct flow to all nine outlets. Finally, we achieved to produce flexible paths for flowing particles including side trips.

  10. Comparison of Mars Science Laboratory Reaction Control System Jet Computations With Flow Visualization and Velocimetry

    Science.gov (United States)

    Bathel, Brett F.; Danehy, Paul M.; Johansen, Craig T.; Ashcraft, Scott W.; Novak, Luke A.

    2013-01-01

    Numerical predictions of the Mars Science Laboratory reaction control system jets interacting with a Mach 10 hypersonic flow are compared to experimental nitric oxide planar laser-induced fluorescence data. The steady Reynolds Averaged Navier Stokes equations using the Baldwin-Barth one-equation turbulence model were solved using the OVERFLOW code. The experimental fluorescence data used for comparison consists of qualitative two-dimensional visualization images, qualitative reconstructed three-dimensional flow structures, and quantitative two-dimensional distributions of streamwise velocity. Through modeling of the fluorescence signal equation, computational flow images were produced and directly compared to the qualitative fluorescence data.

  11. Experimental Studies on The Mechanism and COntrol of Secondary Flow Losses in Turbine Cascades

    Institute of Scientific and Technical Information of China (English)

    WangZhongqi; HanWanjin; 等

    1992-01-01

    This paper summarizes the results of the authors' 4 year experimental studies on the secondary flow losses in turbine cascades.cascade wind tunnel experiments were carried out concerning the influence of aspect rations,incidence,turning angles and outer endwall divergent angles in order to unveil the evolution mechanism of secondary flow losses in turbine cascades without end clearance.Some methods for controlling the secondary flows are investigated including the blade leaning,blade cambering,endwall convergence and leading edge extension at two ends of the blade.

  12. Power flow analysis for droop controlled LV hybrid AC-DC microgrids with virtual impedance

    DEFF Research Database (Denmark)

    Li, Chendan; Chaudhary, Sanjay; Vasquez, Juan Carlos

    2014-01-01

    The AC-DC hybrid microgrid is an effective form of utilizing different energy resources and the analysis of this system requires a proper power flow algorithm. This paper proposes a suitable power flow algorithm for LV hybrid AC-DC microgrid based on droop control and virtual impedance. Droop...... and virtual impedance concepts for AC network, DC network and interlinking converter are reviewed so as to model it in the power flow analysis. The validation of the algorithm is verified by comparing it with steady state results from detailed time domain simulation. The effectiveness of the proposed...

  13. Preventive Security-Constrained Optimal Power Flow Considering UPFC Control Modes

    Directory of Open Access Journals (Sweden)

    Xi Wu

    2017-08-01

    Full Text Available The successful application of the unified power flow controller (UPFC provides a new control method for the secure and economic operation of power system. In order to make the full use of UPFC and improve the economic efficiency and static security of a power system, a preventive security-constrained power flow optimization method considering UPFC control modes is proposed in this paper. Firstly, an iterative method considering UPFC control modes is deduced for power flow calculation. Taking into account the influence of different UPFC control modes on the distribution of power flow after N-1 contingency, the optimization model is then constructed by setting a minimal system operation cost and a maximum static security margin as the objective. Based on this model, the particle swarm optimization (PSO algorithm is utilized to optimize power system operating parameters and UPFC control modes simultaneously. Finally, a standard IEEE 30-bus system is utilized to demonstrate that the proposed method fully exploits the potential of static control of UPFC and significantly increases the economic efficiency and static security of the power system.

  14. Effect of DC Link Control Strategies on Multiterminal AC-DC Power Flow

    Directory of Open Access Journals (Sweden)

    Shagufta Khan

    2015-01-01

    Full Text Available For power-flow solution of power systems incorporating multiterminal DC (MTDC network(s, five quantities are required to be solved per converter. On the other hand, only three independent equations comprising two basic converter equations and one DC network equation exist per converter. Thus, for solution, two additional equations are required. These two equations are derived from the control specifications adopted for the DC links. Depending on the application, several combinations of valid control specifications are possible. Each combination of a set of valid control specifications is known as a control strategy. The number of control strategies increases with an increase in the number of the DC terminals or converters. It is observed that the power-flow convergence of integrated AC-MTDC power systems is strongly affected by the control strategy adopted for the DC links. This work investigates the mechanism by which different control strategies affect the power-flow convergence pattern of AC-MTDC power systems. To solve the DC variables in the Newton-Raphson (NR power-flow model, sequential method is considered in this paper. Numerous case studies carried out on a three-terminal DC network incorporated in the IEEE-300 bus test system validate this.

  15. Effect of refrigerant flow control on the thermodynamic performances of reciprocating chillers

    Energy Technology Data Exchange (ETDEWEB)

    Tassou, S.A.; Al-Nizari, H.O. (Brunel, The University of West London, Uxbridge (United Kingdom). Dept. of Mechanical Engineering)

    1993-01-01

    This paper investigates the effect of refrigerant flow control on the steady-state and transient performances of refrigeration systems. The objective is to identify the effect of alternative expansion valves and design and control criteria on the energy efficiency of the system. The results indicate that a high valve-gain reduces the on/off cycling losses but produces high-amplitude superheat oscillations at steady-state conditions. Low valve-gain, on the other hand, increases the cycling losses but improves the stability of superheat control at steady-state conditions. For optimum performance, a variable-gain refrigerant flow-control device is required. Variable gain, together with other control refinements, can be implemented through the development of microprocessor-controlled electronic expansion-devices. (author)

  16. Passive microfluidic control of two merging streams by capillarity and relative flow resistance.

    Science.gov (United States)

    Kim, Sung-Jin; Lim, Yong Taik; Yang, Haesik; Shin, Yong Beom; Kim, Kyuwon; Lee, Dae-Sik; Park, Se Ho; Kim, Youn Tae

    2005-10-01

    In the progress of microfluidic devices, a simple and precise control of multiple streams has been essential for complex microfluidic networks. Consequently, microfluidic devices, which have a simple structure, typically use external energy sources to control the multiple streams. Here, we propose a pure passive scheme that uses capillarity without using external force or external regulation to control the merging of two streams and even to regulate their volumetric flow rate (VFR). We accomplish this process by controlling the geometry of two inlets and a junction, and by regulating the hydrophilicity of a substrate. Additionally, we use the relative flow resistance to control the VFR ratio of the merged two streams. Our results will significantly simplify the control of multiple streams without sacrificing precision.

  17. Dielectric Barrier Discharge Plasma Actuator for Flow Control

    Science.gov (United States)

    Opaits, Dmitry, F.

    2012-01-01

    This report is Part II of the final report of NASA Cooperative Agreement contract no. NNX07AC02A. It includes a Ph.D. dissertation. The period of performance was January 1, 2007 to December 31, 2010. Part I of the final report is the overview published as NASA/CR-2012- 217654. Asymmetric dielectric barrier discharge (DBD) plasma actuators driven by nanosecond pulses superimposed on dc bias voltage are studied experimentally. This produces non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. The approach consisted of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

  18. A New Real Time Lyapunov Based Controller for Power Quality Improvement in Unified Power Flow Controllers Using Direct Matrix Converters

    Directory of Open Access Journals (Sweden)

    Joaquim Monteiro

    2017-06-01

    Full Text Available This paper proposes a Direct Matrix Converter operating as a Unified Power Flow Controller (DMC-UPFC with an advanced control method for UPFC, based on the Lyapunov direct method, presenting good results in power quality assessment. This control method is used for real-time calculation of the appropriate matrix switching state, determining which switching state should be applied in the following sampling period. The control strategy takes into account active and reactive power flow references to choose the vector converter closest to the optimum. Theoretical principles for this new real-time vector modulation and control applied to the DMC-UPFC with input filter are established. The method needs DMC-UPFC dynamic equations to be solved just once in each control cycle, to find the required optimum vector, in contrast to similar control methods that need 27 vector estimations per control cycle. The designed controller’s performance was evaluated using Matlab/Simulink software. Controllers were also implemented using a digital signal processing (DSP system and matrix hardware. Simulation and experimental results show decoupled transmission line active (P and reactive (Q power control with zero theoretical error tracking and fast response. Output currents and voltages show small ripple and low harmonic content.

  19. Integrated control system of transverse flow CO II laser and its application

    Science.gov (United States)

    Liu, Juan; Tang, Xiahui; Zhang, Yang; Peng, Hao; Wang, Youqing

    2008-03-01

    Aiming to the special high power CO II laser surface treatment, the paper developed the integrated control system based on S7-200 PLC of transverse flow CO II laser. The selection of key technology and components, detection and control of signals, integrated control of complete circuit, technology of human machine interface and process control of system have been researched. Double closed loop power control system was realized, so that the stability of the laser power was in +/-2%. Also, the giving power can be controlled by the laser controller or by the processing machine, thus, the users can control the laser more efficiently when processing. A series of experiments have been performed on 5kW transverse flow CO II laser, the output laser power was stable at discharge current of 9A for 8 hours, and the maximal power was 5.42 kW. The new type of transverse flow CO II Laser with Integrated Control System has been applied for special laser cladding with power-modulating on the metallic surface of the oil industry production.

  20. ASYMMETRIC VORTICES FLOW OVER SLENDER BODY AND ITS ACTIVE CONTROL AT HIGH ANGLE OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    DENG Xueying; WANG Yankui

    2004-01-01

    The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed,which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks.

  1. Modeling Cerebral Blood Flow Control During Posture Change from Sitting to Standing

    DEFF Research Database (Denmark)

    Olufsen, Mette; Tran, Hien; Ottesen, Johnny T.

    2004-01-01

    , the heart, and venous valves. We use physiologically based control mechanisms to describe the regulation of cerebral blood velocity and arterial pressure in response to orthostatic hypotension resulting from postural change. Beyond active control mechanisms we also have to include certain passive non......Hypertension, decreased cerebral blood flow, and diminished cerebral blood flow regulation, are among the first signs indicating the presence of cerebral vascular disease. In this paper, we will present a mathematical model that can predict blood flow and pressure during posture change from sitting......-linearities in some of the compliance-pressure and resistance-pressure relationships. Futhermore, an acurate and physiologically based submodel, describing the dynamics of how gravity effects the blood distribution during suspine changes, is included. To justify the fidelity of our mathematical model and control...

  2. Experimental Study of Stable Surfaces for Anti-Slug Control in Multi-phase Flow

    DEFF Research Database (Denmark)

    Pedersen, Simon; Løhndorf, Petar Durdevic; Stampe, Kasper;

    2016-01-01

    Severe slugging flow is always challenging in oil & gas production, especially for the current offshore based production. The slugging flow can cause a lot of problems, such as those relevant to production safety, fatigue as well as capability. As one typical phenomenon in multi-phase flow dynamics......, the slug can be avoided or eliminated by proper facility design or control of operational conditions. Based on a testing facility which can emulate a pipeline-riser or a gas-lifted production well in a scaled-down manner, this paper experimentally studies the correlations of key operational parameters...... that the capability, performance and efficiency of anti-slug control can be dramatically improved if these stable surfaces can be experimentally determined beforehand. The paper concludes that obtaining the stable surface on the new developed map can significantly improve the production rate in a control scheme. Even...

  3. EXPERIMENTAL MEASUREMENT OF MAGNETIC FIELD IN A NOVEL FLOW CONTROL OF MOLD

    Institute of Scientific and Technical Information of China (English)

    G.J. Xu; D.H. Li; J.C. He

    2002-01-01

    In order to know the distribution of magnetic field in a novel flow control of mold(NFC Mold) and to provide the experimental data for the electromagnetic structuredesign and the analysis of flow control in continuous casting mold, the magnetic fieldin a NFC Mold were measured by Tesla meter of Model CT-3. The method of vectorsynthesis was adopted in the measurement of magnetic fields. The results showed thatthe magnetic field in the NFC Mold was composed of two main magnetic areas thatwere symmetrical. Although there was leaking magnetic flux between the lower surfaceof the upper pole and the upper surface of the lower pole on the sides, it was restrainedby the main magnetic fields effectively. Therefore the NFC Mold was more preferablysatisfied to be used in controlling the molten steel flow in continuous casting mold.

  4. A History of Suction-Type Laminar Flow Control with Emphasis on Flight Research

    Science.gov (United States)

    Braslow, Albert L.

    1999-01-01

    Laminar-flow control is an area of aeronautical research that has a long history at NASA's Langley Research Center, Dryden Flight Research Center, their predecessor organizations, and elsewhere. In this monograph, the author, who spent much of his career at Langley working with this research, presents a history of that portion of laminar-flow technology known as active laminar-flow control, which employs suction of a small quantity of air through airplane surfaces. This important technique offers the potential for significant reduction in drag and, thereby, for large increases in range or reductions in fuel usage for aircraft. For transport aircraft, the reductions in fuel consumed as a result of laminar-flow control may equal 30 percent of present consumption. Given such potential, it is obvious that active laminar-flow control with suction is an important technology. In this study, the author covers the early history of the subject and brings the story all the way to the mid-1990s with an emphasis on flight research, much of which has occurred at Dryden. This is an important monograph that not only encapsulates a lot of history in a brief compass but also does so in language that is accessible to non-technical readers. NASA is publishing it in a format that will enable it to reach the wide audience the subject deserves.

  5. Control Theoretic Modeling and Generated Flow Patterns of a Fish-Tail Robot

    Science.gov (United States)

    Massey, Brian; Morgansen, Kristi; Dabiri, Dana

    2003-11-01

    Many real-world engineering problems involve understanding and manipulating fluid flows. One of the challenges to further progress in the area of active flow control is the lack of appropriate models that are amenable to control-theoretic studies and algorithm design and also incorporate reasonably realistic fluid dynamic effects. We focus here on modeling and model-verification of bio-inspired actuators (fish-fin type structures) used to control fluid dynamic artifacts that will affect speed, agility, and stealth of Underwater Autonomous Vehicles (UAVs). Vehicles using fish-tail type systems are more maneuverable, can turn in much shorter and more constrained spaces, have lower drag, are quieter and potentially more efficient than those using propellers. We will present control-theoretic models for a simple prototype coupled fluid and mechanical actuator where fluid effects are crudely modeled by assuming only lift, drag, and added mass, while neglecting boundary effects. These models will be tested with different control input parameters on an experimental fish-tail robot with the resulting flow captured with DPIV. Relations between the model, the control function choices, the obtained thrust and drag, and the corresponding flow patterns will be presented and discussed.

  6. Application of Newton's optimal power flow in voltage/reactive power control

    Energy Technology Data Exchange (ETDEWEB)

    Bjelogrlic, M.; Babic, B.S. (Electric Power Board of Serbia, Belgrade (YU)); Calovic, M.S. (Dept. of Electrical Engineering, University of Belgrade, Belgrade (YU)); Ristanovic, P. (Institute Nikola Tesla, Belgrade (YU))

    1990-11-01

    This paper considers an application of Newton's optimal power flow to the solution of the secondary voltage/reactive power control in transmission networks. An efficient computer program based on the latest achievements in the sparse matrix/vector techniques has been developed for this purpose. It is characterized by good robustness, accuracy and speed. A combined objective function appropriate for various system load levels with suitable constraints, for treatment of the power system security and economy is also proposed. For the real-time voltage/reactive power control, a suboptimal power flow procedure has been derived by using the reduced set of control variables. This procedure is based on the sensitivity theory applied to the determination of zones for the secondary voltage/reactive power control and corresponding reduced set of regulating sources, whose reactive outputs represent control variables in the optimal power flow program. As a result, the optimal power flow program output becomes a schedule to be used by operators in the process of the real-time voltage/reactive power control in both normal and emergency operating states.

  7. Resource Considerations during Parallel Scheduling of Large Control Flow Dominated Applications

    DEFF Research Database (Denmark)

    Grode, Jesper Nicolai Riis; Madsen, Jan

    1995-01-01

    This paper presents a technique to determine the possible parallelism between different control-structures in large hierarchical Control- and Data-Flow Graphs (CDFGs). The technique is based on a hierarchical bottom-up heuristic, which after resolving data- and control-dependencies between control......-structures, parallelizes selected control-structures , subject to minimizing resource consumption. The purpose of the technique is to be able to predict resource consumption and estimate execution time for large CDFGs. The technique has been tested on several CDFGs with up to 1442 nodes. The results indicate...

  8. Open-phase operating modes of power flow control topologies in a Smart Grid Distribution Network

    Science.gov (United States)

    Astashev, M. G.; Novikov, M. A.; Panfilov, D. I.; Rashitov, P. A.; Remizevich, T. V.; Fedorova, M. I.

    2015-12-01

    The power flow regulating circuit node in an alternating current system is reviewed. The circuit node is accomplished based on a thyristor controlled phase angle regulator (TCPAR) with controlled thyristor switch. Research results of the individual phase control of the output voltage for the TCPAR are presented. Analytical expressions for the overvoltage factor calculation in the thyristor switch circuit for open-phase operating modes are received. Based on evaluation of overvoltage in operational and emergency modes, the implementability conditions of the individual phase control of the output voltage are determined. Under these conditions, maximal performance and complete controllability are provided.

  9. The development of three-dimensional adjoint method for flow control with blowing in convergent-divergent nozzle flows

    Science.gov (United States)

    Sikarwar, Nidhi

    The noise produced by the low bypass ratio turbofan engines used to power fighter aircraft is a problem for communities near military bases and for personnel working in close proximity to the aircraft. For example, carrier deck personnel are subject to noise exposure that can result in Noise-Induced Hearing Loss which in-turn results in over a billion dollars of disability payments by the Veterans Administration. Several methods have been proposed to reduce the jet noise at the source. These methods include microjet injection of air or water downstream of the jet exit, chevrons, and corrugated nozzle inserts. The last method involves the insertion of corrugated seals into the diverging section of a military-style convergent-divergent jet nozzle (to replace the existing seals). This has been shown to reduce both the broadband shock-associated noise as well as the mixing noise in the peak noise radiation direction. However, the original inserts were designed to be effective for a take-off condition where the jet is over-expanded. The nozzle performance would be expected to degrade at other conditions, such as in cruise at altitude. A new method has been proposed to achieve the same effects as corrugated seals, but using fluidic inserts. This involves injection of air, at relatively low pressures and total mass flow rates, into the diverging section of the nozzle. These fluidic inserts" deflect the flow in the same way as the mechanical inserts. The fluidic inserts represent an active control method, since the injectors can be modified or turned off depending on the jet operating conditions. Noise reductions in the peak noise direction of 5 to 6 dB have been achieved and broadband shock-associated noise is effectively suppressed. There are multiple parameters to be considered in the design of the fluidic inserts. This includes the number and location of the injectors and the pressures and mass flow rates to be used. These could be optimized on an ad hoc basis with

  10. Heat flow control in thermo-magnetic convective systems using engineered magnetic fields

    Science.gov (United States)

    Lee, Jaewook; Nomura, Tsuyoshi; Dede, Ercan M.

    2012-09-01

    We present the design of a magnetically controlled convective heat transfer system. The underlying thermo-magnetic instability phenomenon is described, and enhanced convective fluid flow patterns are determined using non-linear programming techniques plus a design sensitivity analysis. Specifically, the magnetic fluid body force is computed by finding the optimal distribution and magnetization direction of a magnetic field source, where the objective is to minimize the maximum temperature of a closed loop heat transfer system. Sizeable fluid recirculation zones are induced by arranging magnetic field generation elements in configurations similar to Halbach arrays. Applications include improved heat flow control for electromechanical systems.

  11. Numerical experiments on transition control in wall-bounded shear flows

    Science.gov (United States)

    Biringen, S.; Caruso, M. J.

    1987-01-01

    Results are presented from a numerical simulation of transition control in plane channel and boundary layer flows. The analysis is based on a pseudo-spectral/finite difference semi-implicit solution procedure employed to numerically integrate the time-dependent, three-dimensional, incompressible Navier-Stokes equations in a doubly periodic domain. In the channel flow, it was found that the active periodic suction/blowing method was effective in controlling strongly three-dimensional disturbances. In the boundary layer, the preliminary analysis indicated that in the early stages, passive control by suction is as effective as active control to suppress instabilities. The current work is focused on a detailed comparison of active and passive control by suction/blowing in the boundary layer.

  12. Optimal Control of Partially Miscible Two-Phase Flow with Applications to Subsurface CO2 Sequestration

    KAUST Repository

    Simon, Moritz

    2013-01-01

    Motivated by applications in subsurface CO2 sequestration, we investigate constrained optimal control problems with partially miscible two-phase flow in porous media. The objective is, e.g., to maximize the amount of trapped CO2 in an underground reservoir after a fixed period of CO2 injection, where the time-dependent injection rates in multiple wells are used as control parameters. We describe the governing two-phase two-component Darcy flow PDE system and formulate the optimal control problem. For the discretization we use a variant of the BOX method, a locally conservative control-volume FE method. The timestep-wise Lagrangian of the control problem is implemented as a functional in the PDE toolbox Sundance, which is part of the HPC software Trilinos. The resulting MPI parallelized Sundance state and adjoint solvers are linked to the interior point optimization package IPOPT. Finally, we present some numerical results in a heterogeneous model reservoir.

  13. Nonlinear Power Flow Control Design Utilizing Exergy, Entropy, Static and Dynamic Stability, and Lyapunov Analysis

    CERN Document Server

    Robinett III, Rush D

    2011-01-01

    Nonlinear Powerflow Control Design presents an innovative control system design process motivated by renewable energy electric grid integration problems. The concepts developed result from the convergence of three research and development goals: • to create a unifying metric to compare the value of different energy sources – coal-burning power plant, wind turbines, solar photovoltaics, etc. – to be integrated into the electric power grid and to replace the typical metric of costs/profit; • to develop a new nonlinear control tool that applies power flow control, thermodynamics, and complex adaptive systems theory to the energy grid in a consistent way; and • to apply collective robotics theories to the creation of high-performance teams of people and key individuals in order to account for human factors in controlling and selling power into a distributed, decentralized electric power grid. All three of these goals have important concepts in common: exergy flow, limit cycles, and balance between compe...

  14. A flow control study of a supersonic mixing layer via NPLS

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The flow control of a supersonic mixing layer was studied in a supersonic mixing layer wind tunnel with convective Mach number (Mc) at 0.5. The passive control of the mixing layer was achieved by perturbation tapes on the trailing edge of the splitter plate. The control effects of 2D and 3D perturbation tapes with different sizes were compared. The mixing layer was visualized via NPLS,and the transient fine structures were identifiable in NPLS images,which were used to analyze the effects of flow control. The results show that the 2D tapes can enhance the 2D characteristic of the mixing layer,delaying mixing layer transition; and the 3D tapes can enhance the 3D characteristic of the mixing layer,advancing mixing layer transition. 3D structures of the mixing layer were visualized,and the H-type Λ vortexes were found with 3D tapes control.

  15. Power Quality Improvement Using Hybrid Power Flow Controller in Power System

    Directory of Open Access Journals (Sweden)

    Manidhar Thula ,

    2014-01-01

    Full Text Available This paper discusses the applicability of Hybrid Power Flow Controller (HPFC as an alternative to Unified Power Flow Controller (UPFC for improvement of power system performance. UPFC is a flexible AC transmission system (FACTS device containing two switching converters, one in series and one in shunt. To configure the HPFC, one of the switching converters of the UPFC is replaced by thyristor controlled variable impedances, thus reducing the cost. In this paper, the HPFC has been configured by multilevel Voltage Source Converter (VSC used for the shunt compensation branches and a thyristor controlled variable impedance used for series compensation. It is shown that with suitable control the HPFC can inject a voltage of required magnitude in series with the line at any desired angle, just like UPFC. This helps in providing compensation equivalent to UPFC and improving the steady state stability limits of the power system.

  16. A nonlinear optimization approach for UPFC power flow control and voltage security

    Science.gov (United States)

    Kalyani, Radha Padma

    This dissertation provides a nonlinear optimization algorithm for the long term control of Unified Power Flow Controller (UPFC) to remove overloads and voltage violations by optimized control of power flows and voltages in the power network. It provides a control strategy for finding the long term control settings of one or more UPFCs by considering all the possible settings and all the (N-1) topologies of a power network. Also, a simple evolutionary algorithm (EA) has been proposed for the placement of more than one UPFC in large power systems. In this publication dissertation, Paper 1 proposes the algorithm and provides the mathematical and empirical evidence. Paper 2 focuses on comparing the proposed algorithm with Linear Programming (LP) based corrective method proposed in literature recently and mitigating cascading failures in larger power systems. EA for placement along with preliminary results of the nonlinear optimization is given in Paper 3.

  17. Minimization of Interrupted Power by Optimal Power Flow Control with Multiple UPFCs

    Science.gov (United States)

    Kawabe, Ken-Ichi; Yokoyama, Akihiko

    Our study aims at minimization of power not supplied (PNS) under the severe fault condition such as tripping of double circuits of transmission lines. In this paper, we propose a new static control method which can minimize PNS by coordinately controlling multiple unified power flow controllers (UPFCs), generators and loads. The proposed method is based on multiple optimal power flow (OPF) calculations, and determines not only control variables of UPFCs but also which and how much generators and loads should be shed after the fault. Digital simulations are carried out with the IEEE RTS-24 system. Three simulation cases, with and without UPFCs, and with uncontrollable UPFCs, are compared and the results shows that reduction of PNS can be accomplished by UPFCs with the proposed control method. Furthermore, it is made clear that the multiple OPFs, which consider the priority loads to be shed, are very effective on reduction of total PNS.

  18. Robust optimal control of material flows in demand-driven supply networks

    Science.gov (United States)

    Laumanns, Marco; Lefeber, Erjen

    2006-04-01

    We develop a model based on stochastic discrete-time controlled dynamical systems in order to derive optimal policies for controlling the material flow in supply networks. Each node in the network is described as a transducer such that the dynamics of the material and information flows within the entire network can be expressed by a system of first-order difference equations, where some inputs to the system act as external disturbances. We apply methods from constrained robust optimal control to compute the explicit control law as a function of the current state. For the numerical examples considered, these control laws correspond to certain classes of optimal ordering policies from inventory management while avoiding, however, any a priori assumptions about the general form of the policy.

  19. Macropore system characteristics controls on non-reactive solute transport at different flow rates

    Science.gov (United States)

    Larsbo, Mats; Koestel, John

    2014-05-01

    Preferential flow and transport in macroporous soils are important pathways for the leaching of agrochemicals through soils. Preferential solute transport in soil is to a large extent determined by the macropore system characteristics and the water flow conditions. The importance of different characteristics of the macropore system is likely to vary with the flow conditions. The objective of this study was to determine which properties of the macropore system that control the shape of non-reactive tracer solute breakthrough curves at different steady-state flow rates. We sampled five undisturbed columns (20 cm high, 20 cm diameter) from the soil surface of four soils with clay contents between 21 and 50 %. Solute transport experiments were carried out under unsaturated conditions at 2, 4, 6, 8 and 12 mm h-1 flow rates. For each flow rate a pulse of potassium bromide solution was applied at the soil surface and the electrical conductivity was measured with high temporal resolution in the column effluent. We used the 5 % arrival time and the holdback factor to estimate the degree of preferential transport from the resulting breakthrough curves. Unsaturated hydraulic conductivities were measured at the soil surface of the columns using a tension disc infiltrometer. The macropore system was imaged by industrial X-ray computed tomography at a resolution of 125 μm in all directions. Measures of the macropore system characteristics including measures of pore continuity were calculated from these images using the ImageJ software. Results show that the degree of preferential transport is generally increasing with flow rate when larger pores become active in the transport. The degree of preferential flow was correlated to measures of macropore topology. This study show that conclusions drawn from experiments carried out at one flow rate should generally not be extrapolated to other flow rates.

  20. The Dynamics of Controlled Flow Separation within a Diverter Duct Diffuser

    Science.gov (United States)

    Peterson, C. J.; Vukasinovic, B.; Glezer, A.

    2016-11-01

    The evolution and receptivity to fluidic actuation of the flow separation within a rectangular, constant-width, diffuser that is branched off of a primary channel is investigated experimentally at speeds up to M = 0.4. The coupling between the diffuser's adverse pressure gradient and the internal separation that constricts nearly half of the flow passage through the duct is controlled using a spanwise array of fluidic actuators on the surface upstream of the diffuser's inlet plane. The dynamics of the separating surface vorticity layer in the absence and presence of actuation are investigated using high-speed particle image velocimetry combined with surface pressure measurements and total pressure distributions at the primary channel's exit plane. It is shown that the actuation significantly alters the incipient dynamics of the separating vorticity layer as the characteristic cross stream scales of the boundary layer upstream of separation and of the ensuing vorticity concentrations within the separated flow increase progressively with actuation level. It is argued that the dissipative (high frequency) actuation alters the balance between large- and small-scale motions near separation by intensifying the large-scale motions and limiting the small-scale dynamics. Controlling separation within the diffuser duct also has a profound effect on the global flow. In the presence of actuation, the mass flow rate in the primary duct increases 10% while the fraction of the diverted mass flow rate in the diffuser increases by more than 45% at 0.7% actuation mass fraction. Supported by the Boeing Company.

  1. Feedback Control of Flow Separation Using Plasma Actuator and FBG Sensor

    Directory of Open Access Journals (Sweden)

    Takehiko Segawa

    2016-01-01

    Full Text Available A feedback control system for mitigating flow separation was developed by using a string-type dielectric-barrier-discharge (DBD plasma actuator and a fiber Bragg grating (FBG sensor. Tangential jets were induced from the string-type DBD plasma actuator, which was located at 5% chord from the leading edge of an NACA0024 airfoil. The FBG sensor was attached to the interior surface near the root of the cantilever beam modeled on the pressure surface of the airfoil. The strain at the cantilever root was reflected in the form of Bragg wavelengths (λB detected by the FBG sensor when the cantilever tip was vibrated by the flow near the trailing edge of the airfoil. It was found that calculating running standard deviations in the Bragg wavelength (λB′ detected by the sensor was valuable for judging flow separation in real time. The feedback control of flow separation on the NACA0024 airfoil was successfully demonstrated by setting λB′=0.0028 with periodic flow separations generated in a wind tunnel by oscillating a side wall of the test section with frequency fw=0.42 Hz. It was confirmed that the appearance probability of flow separation tends to decrease with a decrease in the duration for calculating λB′ and with an increase in the duration of jet injection.

  2. Surface Patterning: Controlling Fluid Flow Through Dolphin and Shark Skin Biomimicry

    Science.gov (United States)

    Gamble, Lawren; Lang, Amy; Bradshaw, Michael; McVay, Eric

    2013-11-01

    Dolphin skin is characterized by circumferential ridges, perpendicular to fluid flow, present from the crest of the head until the tail fluke. When observing a cross section of skin, the ridges have a sinusoidal pattern. Sinusoidal grooves have been proven to induce vortices in the cavities that can help control flow separation which can reduce pressure drag. Shark skin, however, is patterned with flexible scales that bristle up to 50 degrees with reversed flow. Both dolphin ridges and shark scales are thought to help control fluid flow and increase swimming efficiency by delaying the separation of the boundary layer. This study investigates how flow characteristics can be altered with bio-inspired surface patterning. A NACA 4412 hydrofoil was entirely patterned with transverse sinusoidal grooves, inspired by dolphin skin but scaled so the cavities on the model have the same Reynolds number as the cavities on a swimming shark. Static tests were conducted at a Reynolds number of approximately 100,000 and at varying angles of attack. The results were compared to the smooth hydrofoil case. The flow data was quantified using Digital Particle Image Velocimetry (DPIV). The results of this study demonstrated that the patterned hydrofoil experienced greater separation than the smooth hydrofoil. It is hypothesize that this could be remediated if the pattern was placed only after the maximum thickness of the hydrofoil. Funding through NSF REU grant 1062611 is gratefully acknowledged.

  3. Field Test Results from a 10 kW Wind Turbine with Active Flow Control

    Science.gov (United States)

    Rice, Thomas; Bychkova, Veronika; Taylor, Keith; Clingman, Dan; Amitay, Michael

    2015-11-01

    Active flow control devices including synthetic jets and dynamic vortex generators were tested on a 10 kW wind turbine at RPI. Previous work has shown that load oscillations caused by dynamic stall could be modified through the use of active flow control by injecting momentum into the flow field near the leading edge of a dynamically pitching model. In this study, this work has been extended to its logical conclusion, field-testing active flow control on a real wind turbine. The blades in the current study have a 0.28m chord and 3.05m span, no twist or taper, and were retrofitted with six synthetic jets on one blade and ten dynamic vortex generators on a second blade. The third blade of this turbine was not modified, in order to serve as a control. Strain gauges were installed on each blade to measure blades' deflection. A simple closed loop control was demonstrated and preliminary results indicate reduced vibrational amplitude. Future testing will be conducted on a larger scale, 600kW machine at NREL, incorporating information collected during this study.

  4. Reduction of aerodynamic load fluctuation on wind turbine blades through active flow control

    Science.gov (United States)

    Velarde, John-Michael; Coleman, Thomas; Magstadt, Andrew; Aggarwal, Somil; Glauser, Mark

    2015-11-01

    The current set of experiments deals with implementing active flow control on a Bergey Excel 1, 1kW turbine. The previous work in our group demonstrated successfully that implementation of a simple closed-loop controller could reduce unsteady aerodynamic load fluctuation by 18% on a vertically mounted wing. Here we describe a similar flow control method adapted to work in the rotating frame of a 2.5m diameter wind turbine. Strain gages at the base of each blade measure the unsteady fluctuation in the blades and pressure taps distributed along the span of the blades feed information to the closed-loop control scheme. A realistic, unsteady flow field has been generated by placing a cylinder upstream of the turbine to induce shedding vortices at frequencies in the bandwidth of the first structural bending mode of the turbine blades. The goal of these experiments is to demonstrate closed-loop flow control as a means to reduce the unsteady fluctuation in the blades and increase the overall lifespan of the wind turbine.

  5. An Innovative Algorithm to Implement Flow Control in Full Duplex Ethernet

    Institute of Scientific and Technical Information of China (English)

    WANGTao; GENing; FENGChongxi

    2003-01-01

    Nowadays Ethernet is a widely used LAN technology.It is based on a Media access control (MAC) method called Carrier sense multiple access with Collision detection(CAMS/CD).With CSMA/CD,hosts on Ethernet must operate in half duplex mode;with collision detection and random backoff,Ethernet is a self-contained LAN in the aspect of flow control.After the appearance of switching Ethernet,applications of full duplex Ethernet are booming,and how to manage network bandwidth and switch ports without CSMA/CD is a major issue.In this way,IEEE specifled and explicit flow control scheme,called "PAUSE operation" in Standard 802.3.In order to implement IEEE PAUSE operation and flow control effectively,we propose an innovative algorithm called Queue Length based PAUSE operation-QLPAUSE.It will set the pause time parameter according to the instant input port queue length and local condition checking.With it the hosts can make better use of the full duplex link.With the simulation results,it is proved that QLPAUSE is an active flow control,and it is an easy-to-implement and high efflciency scheme.Finally,the application of this algorithm is provided,with more and more Switching Ethernet,and PAUSE operation is accepted and supported by more and more manufacturers.Within many implementation methods,QLPAUSE is a best candidate.

  6. Numerical Modeling of Cavitating Venturi: A Flow Control Element of Propulsion System

    Science.gov (United States)

    Majumdar, Alok; Saxon, Jeff (Technical Monitor)

    2002-01-01

    In a propulsion system, the propellant flow and mixture ratio could be controlled either by variable area flow control valves or by passive flow control elements such as cavitating venturies. Cavitating venturies maintain constant propellant flowrate for fixed inlet conditions (pressure and temperature) and wide range of outlet pressures, thereby maintain constant, engine thrust and mixture ratio. The flowrate through the venturi reaches a constant value and becomes independent of outlet pressure when the pressure at throat becomes equal to vapor pressure. In order to develop a numerical model of propulsion system, it is necessary to model cavitating venturies in propellant feed systems. This paper presents a finite volume model of flow network of a cavitating venturi. The venturi was discretized into a number of control volumes and mass, momentum and energy conservation equations in each control volume are simultaneously solved to calculate one-dimensional pressure, density, and flowrate and temperature distribution. The numerical model predicts cavitations at the throat when outlet pressure was gradually reduced. Once cavitation starts, with further reduction of downstream pressure, no change in flowrate is found. The numerical predictions have been compared with test data and empirical equation based on Bernoulli's equation.

  7. High-Lift System for a Supercritical Airfoil: Simplified by Active Flow Control

    Science.gov (United States)

    Melton, LaTunia Pack; Schaeffler, Norman W.; Lin, John C.

    2007-01-01

    Active flow control wind tunnel experiments were conducted in the NASA Langley Low-Turbulence Pressure Tunnel using a two-dimensional supercritical high-lift airfoil with a 15% chord hinged leading-edge flap and a 25% chord hinged trailing-edge flap. This paper focuses on the application of zero-net-mass-flux periodic excitation near the airfoil trailing edge flap shoulder at a Mach number of 0.1 and chord Reynolds numbers of 1.2 x 10(exp 6) to 9 x 10(exp 6) with leading- and trailing-edge flap deflections of 25 deg. and 30 deg., respectively. The purpose of the investigation was to increase the zero-net-mass-flux options for controlling trailing edge flap separation by using a larger model than used on the low Reynolds number version of this model and to investigate the effect of flow control at higher Reynolds numbers. Static and dynamic surface pressures and wake pressures were acquired to determine the effects of flow control on airfoil performance. Active flow control was applied both upstream of the trailing edge flap and immediately downstream of the trailing edge flap shoulder and the effects of Reynolds number, excitation frequency and amplitude are presented. The excitations around the trailing edge flap are then combined to control trailing edge flap separation. The combination of two closely spaced actuators around the trailing-edge flap knee was shown to increase the lift produced by an individual actuator. The phase sensitivity between two closely spaced actuators seen at low Reynolds number is confirmed at higher Reynolds numbers. The momentum input required to completely control flow separation on the configuration was larger than that available from the actuators used.

  8. Active Control of Panel Vibrations Induced by a Boundary Layer Flow

    Science.gov (United States)

    Chow, Pao-Liu

    1998-01-01

    In recent years, active and passive control of sound and vibration in aeroelastic structures have received a great deal of attention due to many potential applications to aerospace and other industries. There exists a great deal of research work done in this area. Recent advances in the control of sound and vibration can be found in the several conference proceedings. In this report we will summarize our research findings supported by the NASA grant NAG-1-1175. The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to study the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. The vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings will be presented in the next three sections. In Section II we shall describe our results on the boundary control of nonlinear panel vibration, with or without flow excitation. Section III is concerned with active control of the vibration and sound radiation from a nonlinear elastic panel. A detailed description of our work on the parametric vibrational control of nonlinear elastic panel will be presented in Section IV. This paper will be submitted to the Journal

  9. A review of wind turbine-oriented active flow control strategies

    Science.gov (United States)

    Aubrun, Sandrine; Leroy, Annie; Devinant, Philippe

    2017-10-01

    To reduce the levelized cost of energy, the energy production, robustness and lifespan of horizontal axis wind turbines (HAWTs) have to be improved to ensure optimal energy production and operational availability during periods longer than 15-20 years. HAWTs are subject to unsteady wind loads that generate combinations of unsteady mechanical loads with characteristic time scales from seconds to minutes. This can be reduced by controlling the aerodynamic performance of the wind turbine rotors in real time to compensate the overloads. Mitigating load fluctuations and optimizing the aerodynamic performance at higher time scales need the development of fast-response active flow control (AFC) strategies located as close as possible to the torque generation, i.e., directly on the blades. The most conventional actuators currently used in HAWTs are mechanical flaps/tabs (similar to aeronautical accessories), but some more innovative concepts based on fluidic and plasma actuators are very promising since they are devoid of mechanical parts, have a fast response and can be driven in unsteady modes to influence natural instabilities of the flow. In this context, the present paper aims at giving a state-of-the-art review of current research in wind turbine-oriented flow control strategies applied at the blade scale. It provides an overview of research conducted in the last decade dealing with the actuators and devices devoted to developing AFC on rotor blades, focusing on the flow phenomena that they cause and that can lead to aerodynamic load increase or decrease. After providing some general background on wind turbine blade aerodynamics and on the atmospheric flows in which HAWTs operate, the review focuses on flow separation control and circulation control mainly through experimental investigations. It is followed by a discussion about the overall limitations of current studies in the wind energy context, with a focus on a few studies that attempt to provide a global

  10. Structured Composition of Dataflow and Control-Flow for Reusable and Robust Scientific Workflows

    Energy Technology Data Exchange (ETDEWEB)

    Bowers, S; Ludaescher, B; Ngu, A; Critchlow, T

    2005-09-07

    Data-centric scientific workflows are often modeled as dataflow process networks. The simplicity of the dataflow framework facilitates workflow design, analysis, and optimization. However, some workflow tasks are particularly ''control-flow intensive'', e.g., procedures to make workflows more fault-tolerant and adaptive in an unreliable, distributed computing environment. Modeling complex control-flow directly within a dataflow framework often leads to overly complicated workflows that are hard to comprehend, reuse, schedule, and maintain. In this paper, we develop a framework that allows a structured embedding of control-flow intensive subtasks within dataflow process networks. In this way, we can seamlessly handle complex control-flows without sacrificing the benefits of dataflow. We build upon a flexible actor-oriented modeling and design approach and extend it with (actor) frames and (workflow) templates. A frame is a placeholder for an (existing or planned) collection of components with similar function and signature. A template partially specifies the behavior of a subworkflow by leaving ''holes'' (i.e., frames) in the subworkflow definition. Taken together, these abstraction mechanisms facilitate the separation and structured re-combination of control-flow and dataflow in scientific workflow applications. We illustrate our approach with a real-world scientific workflow from the astrophysics domain. This data-intensive workflow requires remote execution and file transfer in a semi-reliable environment. For such work-flows, we propose a 3-layered architecture: The top-level, typically a dataflow process network, includes Generic Data Transfer (GDT) frames and Generic remote eXecution (GX) frames. At the second level, the user can specialize the behavior of these generic components by embedding a suitable template (here: transducer templates for control-flow intensive tasks). At the third level, frames inside the

  11. Numerical Simulation of Stall Flow Control Using a DBD Plasma Actuator in Pulse Mode

    Science.gov (United States)

    Khoshkhoo, R.; Jahangirian, A.

    2016-09-01

    A numerical simulation method is employed to investigate the effects of the unsteady plasma body force over the stalled NACA 0015 airfoil at low Reynolds number flow conditions. The plasma body force created by a dielectric barrier discharge actuator is modeled with a phenomenological method for plasma simulation coupled with the compressible Navier-Stokes equations. The governing equations are solved using an efficient implicit finitevolume method. The responses of the separated flow field to the effects of an unsteady body force in various inter-pulses and duty cycles as well as different locations and magnitudes are studied. It is shown that the duty cycle and inter-pulse are key parameters for flow separation control. Additionally, it is concluded that the body force is able to attach the flow and can affect boundary layer grow that Mach number 0.1 and Reynolds number of 45000.

  12. Experimental investigation of high-incidence delta-wing flow control

    Science.gov (United States)

    Buzica, Andrei; Bartasevicius, Julius; Breitsamter, Christian

    2017-09-01

    The possibility of extending the flight envelope for configurations with slender delta-shaped wings is investigated in this study by means of active flow control through pulsating jets from slot pairs distributed along the leading edge. The experiments comprise stereoscopic particle image velocimetry as well as force and moment measurements on a half-delta wing model. The analysis focuses on three high-incidence regimes: pre-stall, stall, and post-stall. This study also compares different perturbation methods: blowing with spatially constant and variable parameters, frequency and phase. At an incidence of 45^circ, the unison pulsed blowing facilitates the most significant flow transformation. Here, the separated shear layer reattaches on the wing's suction side, thus increasing the lift. Phase-averaged flow field measurements describe, in this particular case, the underlying physics of the flow-disturbance interaction.

  13. Hydrodynamic directional control of liquid metal droplets within a microfluidic flow focusing system

    Science.gov (United States)

    Gol, Berrak; Kurdzinski, Michael E.; Tovar-Lopez, Francisco J.; Petersen, Phred; Mitchell, Arnan; Khoshmanesh, Khashayar

    2016-04-01

    Here, we investigate the directional control of Galinstan liquid metal droplets when transferring from the high-viscosity glycerol core into the parallel low-viscosity NaOH sheath streams within a flow focusing microfluidic system. In the presence of sufficient flow mismatch between the sheath streams, the droplets are driven toward the higher velocity interface and cross the interface under the influence of surface tension gradient. A minimum flow mismatch of 125 μl/min is required to enable the continuous transfer of droplets toward the desired sheath stream. The response time of droplets, the time required to change the direction of droplet transfer, is governed by the response time of the syringe pump driven microfluidic system and is found to be 3.3 and 8.8 s when increasing and decreasing the flow rate of sheath stream, respectively.

  14. Numerical Modeling of the Fluid Flow in Continuous Casting Tundish with Different Control Devices

    Directory of Open Access Journals (Sweden)

    Zhu He

    2013-01-01

    Full Text Available Numerical simulations were conducted to study the melt flow under the influence of control devices in a T-type two-strand bloom caster tundish via the open source Computational Fluid Dynamics software OpenFOAM. Three different cases were studied: a bare tundish, a tundish with two pairs of baffles, and a tundish equipped with a turbulence inhibitor and a pair of baffles. Turbulence inhibitor and baffles arrangement showed an improvement of the fluid flow characteristics, yielding lower values of dead volume and higher values of plug flow. With a turbulence inhibitor, the velocity of metal which flows directly toward the tundish floor is smaller and the turbulence kinetic energy of the melt top surface is lower than the other two arrangements.

  15. Traffic flow collection wireless sensor network node for intersection light control

    Science.gov (United States)

    Li, Xu; Li, Xue

    2011-10-01

    Wireless sensor network (WSN) is expected to be deployed in intersection to monitor the traffic flow continuously, and the monitoring datum can be used as the foundation of traffic light control. In this paper, a WSN based on ZigBee protocol for monitoring traffic flow is proposed. Structure, hardware and work flow of WSN nodes are designed. CC2431 from Texas Instrument is chosen as the main computational and transmission unit, and CC2591 as the amplification unit. The stability experiment and the actual environment experiment are carried out in the last of the paper. The results of experiments show that WSN has the ability to collect traffic flow information quickly and transmit the datum to the processing center in real time.

  16. Investigation of several passive and active methods for turbulent flow separation control

    Science.gov (United States)

    Lin, J. C.; Howard, F. G.; Bushnell, D. M.; Selby, G. V.

    1990-01-01

    Relative performance of several passive and active methods for controlling two-dimensional turbulent separated flow associated with a curved backward-facing ramp were investigated at low speeds. Surface static pressure measurement and oil flow visualization results indicate that submerged vortex generators, vortex generator jets, elongated arches at +-alpha, and large-eddy breakup devices at +-alpha placed near the baseline separation location reduce flow separation and increase pressure recovery. Spanwise cylinders reduce flow separation but decrease pressure recovery downstream. Arches with alpha = 0 deg, Helmholtz resonators, and Viets' fluidic flappers examined so far have no significant effect in reducing separation. Wall cooling computation indicates that separation delay on a partially cooled ramp is nearly the same as on a fully-cooled ramp while minimizing the frictional drag increase associated with the wall cooling process.

  17. Characteristics of pulsed plasma synthetic jet and its control effect on supersonic flow

    Institute of Scientific and Technical Information of China (English)

    Jin Di; Cui Wei; Li Yinghong; Li Fanyu; Jia Min; Sun Quan; Zhang Bailing

    2015-01-01

    The plasma synthetic jet is a novel flow control approach which is currently being stud-ied. In this paper its characteristic and control effect on supersonic flow is investigated both exper-imentally and numerically. In the experiment, the formation of plasma synthetic jet and its propagation velocity in quiescent air are recorded and calculated with time resolved schlieren method. The jet velocity is up to 100 m/s and no remarkable difference has been found after chang-ing discharge parameters. When applied in Mach 2 supersonic flow, an obvious shockwave can be observed. In the modeling of electrical heating, the arc domain is not defined as an initial condition with fixed temperature or pressure, but a source term with time-varying input power density, which is expected to better describe the influence of heating process. Velocity variation with different heat-ing efficiencies is presented and discussed and a peak velocity of 850 m/s is achieved in still air with heating power density of 5.0 · 1012 W/m3. For more details on the interaction between plasma syn-thetic jet and supersonic flow, the plasma synthetic jet induced shockwave and the disturbances in the boundary layer are numerically researched. All the results have demonstrated the control authority of plasma synthetic jet onto supersonic flow.

  18. Characteristics of pulsed plasma synthetic jet and its control effect on supersonic flow

    Directory of Open Access Journals (Sweden)

    Jin Di

    2015-02-01

    Full Text Available The plasma synthetic jet is a novel flow control approach which is currently being studied. In this paper its characteristic and control effect on supersonic flow is investigated both experimentally and numerically. In the experiment, the formation of plasma synthetic jet and its propagation velocity in quiescent air are recorded and calculated with time resolved schlieren method. The jet velocity is up to 100 m/s and no remarkable difference has been found after changing discharge parameters. When applied in Mach 2 supersonic flow, an obvious shockwave can be observed. In the modeling of electrical heating, the arc domain is not defined as an initial condition with fixed temperature or pressure, but a source term with time-varying input power density, which is expected to better describe the influence of heating process. Velocity variation with different heating efficiencies is presented and discussed and a peak velocity of 850 m/s is achieved in still air with heating power density of 5.0 × 1012 W/m3. For more details on the interaction between plasma synthetic jet and supersonic flow, the plasma synthetic jet induced shockwave and the disturbances in the boundary layer are numerically researched. All the results have demonstrated the control authority of plasma synthetic jet onto supersonic flow.

  19. Technological study of laser cutting silicon steel controlled by rotating gas flow

    Science.gov (United States)

    Lei, Hong; Yi, Zhang; chenglong, Mi

    2009-04-01

    Using traditional laser cutting technology, it is easy to produce molten slag in laser cutting silicon steel sheet. The main reason is the inevitable oxidizing reaction in the process caused by the use of oxygen as the aided gas. As a common solution, high pressure and high purity N 2 or an inert gas is therefore used instead of oxygen. Although the cut quality is improved, the cutting efficiency is reduced because of the lack of energy generated from an exothermic oxidation reaction. The technology used in this paper is to employ a newly developed cyclone slag separator. The slag separator is located under the workpiece to form rotating gas flow for controlling the direction of the flowing slag gas. Adopting the new technology reported here, oxygen is still used as the aided gas. The experiments prove that, by controlling the technical parameters reasonably tightly, glossy and dross-free cutting kerfs are obtained for reduced laser power. The gas flow acting under the workpiece is simulated using the finite element method (FEM). The operating law of the rotating gas flow is verified by ANSYS, which provides an academic basis for controlling the flowing direction of the slag gas.

  20. Influence of Optic-Flow Information Beyond the Velocity Field on the Active Control of Heading

    Directory of Open Access Journals (Sweden)

    Li Li

    2011-05-01

    Full Text Available We examined both the sufficiency of the optic-flow velocity field and the influence of optic-flow information beyond the velocity field on the active control of heading. The display simulated a vehicle traveling on a circular path through a random-dot 3D cloud under a static or a dynamic scene in which dots were periodically redrawn to remove information beyond a velocity field. Participants used a joystick, under either velocity and acceleration control dynamics, to steer and align the vehicle orientation with their perceived heading while experiencing random perturbations to the vehicle orientation. Frequency response (Bode plots show reasonably good performance under both display conditions with a decrease in gain and an increase in phase lag for the dynamic scene for both control dynamics. The performance data were then fit by a Crossover Model to identify reaction time and lead time constant to determine how much participants anticipated future heading to generate lead control. Reaction time was longer and lead time constant was smaller for the dynamic than the static scene for both control dynamics. We conclude that the velocity field alone is sufficient to support closed-loop heading control, but optic-flow information beyond the velocity field improves visuomotor performance in self-motion control.