Active control of annular flow-induced vibration of axisymmetric elastic beam by the local gap width control

International Nuclear Information System (INIS)

Takada, Shoji; Shintani, Atsuhiko; Ito, Tomohiro; Fujita, Katsuhisa

2011-01-01

Flow-induced vibration may occur in the structures such as elastic beams subjected to annular flow in the narrow passage. Once the flow-induced vibration occurs, vibration amplitude becomes larger, consequently it causes a lot of troubles such as fatigue or failure in mechanical structures. In this paper, for the purpose to avoid these troubles, the active control of vibration of an axisymmetric elastic beam subjected to annular flow is investigated. An air-pressured actuator is attached on the surface of the circular cylinder for the vibrational control. As the shape of the actuator changes by control, the gap width in narrow passage changes, which causes the change of the fluid pressure. Therefore, the vibration of the fluid-structure coupled system can be suppressed. The fluid-structure coupled equation based on the Euler-Bernoulli type of partial differential equation and the Navier-Stokes equations is analytically derived including control terms. By applying the optimal control law to the coupled system, the unstable behavior is stabilized. The stability of the coupled system is investigated by eigenvalue analyses of controlled coupled equations. Numerical simulations are performed to investigate the efficiency of the proposed control method. (author)

Sensor Development for Active Flow Control

Science.gov (United States)

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

2001-01-01

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

Plasma actuators for active flow control based on a glow discharge

International Nuclear Information System (INIS)

Kühn, M.; Kühn-Kauffeldt, M.; Schein, J.; Belinger, A.

2017-01-01

In this work a glow discharge based active flow control for high flow velocities and low Reynolds numbers is presented. Unlike common plasma actuators such as dielectric barrier discharge (DBD) or spark jets, this actuator uses small impulse bits at frequencies. The actuator is optimized for frequencies up to 40 kHz to counter Tollmien Schlichting wave effects and so reduce overall air foil drag. Several measurements to prove the non-eroding effect of the actuator and the electrical properties were performed. It was found that the actuator is capable of operating at high frequencies without measurable erosion. (paper)

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

Usefulness of DC power flow for active power flow analysis with flow controlling devices

NARCIS (Netherlands)

Van Hertem, D.; Verboomen, J.; Purchala, K.; Belmans, R.; Kling, W.L.

2006-01-01

DC power flow is a commonly used tool for contingency analysis. Recently, due to its simplicity and robustness, it also becomes increasingly used for the real-time dispatch and techno-economic analysis of power systems. It is a simplification of a full power flow looking only at active power.

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.

Development of in-series piezoelectric bimorph bending beam actuators for active flow control applications

Science.gov (United States)

Chan, Wilfred K.; Clingman, Dan J.; Amitay, Michael

2016-04-01

Piezoelectric materials have long been used for active flow control purposes in aerospace applications to increase the effectiveness of aerodynamic surfaces on aircraft, wind turbines, and more. Piezoelectric actuators are an appropriate choice due to their low mass, small dimensions, simplistic design, and frequency response. This investigation involves the development of piezoceramic-based actuators with two bimorphs placed in series. Here, the main desired characteristic was the achievable displacement amplitude at specific driving voltages and frequencies. A parametric study was performed, in which actuators with varying dimensions were fabricated and tested. These devices were actuated with a sinusoidal waveform, resulting in an oscillating platform on which to mount active flow control devices, such as dynamic vortex generators. The main quantification method consisted of driving these devices with different voltages and frequencies to determine their free displacement, blocking force, and frequency response. It was found that resonance frequency increased with shorter and thicker actuators, while free displacement increased with longer and thinner actuators. Integration of the devices into active flow control test modules is noted. In addition to physical testing, a quasi-static analytical model was developed and compared with experimental data, which showed close correlation for both free displacement and blocking force.

Stochastic cycle selection in active flow networks

Science.gov (United States)

Woodhouse, Francis; Forrow, Aden; Fawcett, Joanna; Dunkel, Jorn

2016-11-01

Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such non-equilibrium networks. By connecting concepts from lattice field theory, graph theory and transition rate theory, we show how topology controls dynamics in a generic model for actively driven flow on a network. Through theoretical and numerical analysis we identify symmetry-based rules to classify and predict the selection statistics of complex flow cycles from the network topology. Our conceptual framework is applicable to a broad class of biological and non-biological far-from-equilibrium networks, including actively controlled information flows, and establishes a new correspondence between active flow networks and generalized ice-type models.

Local correlations for flap gap oscillatory blowing active flow control technology

Directory of Open Access Journals (Sweden)

Cătălin NAE

2010-09-01

Full Text Available Active technology for oscillatory blowing in the flap gap has been tested at INCAS subsonic wind tunnel in order to evaluate this technology for usage in high lift systems with active flow control. The main goal for this investigation was to validate TRL level 4 for this technology and to extend towards flight testing. CFD analysis was performed in order to identify local correlations with experimental data and to better formulate a design criteria so that a maximum increase in lift is possible under given geometrical constraints. Reference to a proposed metric for noise evaluation is also given. This includes basic 2D flow cases and also 2.5D configurations. In 2.5D test cases this work has been extended so that the proposed system may be selected as a mature technology in the JTI Clean Sky, Smart Fixed Wing Aircraft ITD. Complex post-processing of the experimental and CFD data was mainly oriented towards system efficiency and TRL evaluation for this active technology.

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...

Experimental study of the active control applied to the flow past a backward facing ramp

Science.gov (United States)

Hlevca, Dan; Gilliéron, Patrick; Grasso, Francesco

2018-03-01

An experimental study of open loop active flow control on a backward facing ramp is presented. The ramp has finite span and a slant angle of 25°. Wind tunnel experiments were performed both for the uncontrolled and the controlled cases where time periodic forcing by pulsed jets is considered. The control system exploits an electro-magnetic valve system to generate pulsed jets with an operating frequency and duty cycle ranging, respectively, between 50 and 250 Hz and between 25 and 60%. A parametric study was carried out for three different freestream velocities and varying the frequency of the pulsed jets and the duty cycle. The control strategy relies on the injection of periodic perturbations before separation at the edge of the slant, considering various combinations of frequencies and duty cycles while keeping constant the blowing time for every Reynolds number, so as to excite the flow with the same jet structure over different actuation cycle extents. The receptivity of the flow to periodic forcing was assessed by characterizing mean and unsteady flow properties, turbulence statistics and flow topology. The study focused on the impact of control on reattachement and showed that the flow locks with excitation frequencies typical of initial Kelvin-Helmholtz instabilities. However, the flow was found to respond to any injected unsteady perturbation locking to the forcing frequencies and the extent of the region where locking occurs was found to be of the order of a few slant heights. A relaxation process was observed and the flow was found to relax past the slant trailing edge toward frequencies close to the natural ones.

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

Science.gov (United States)

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

2010-04-01

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

Enhanced fuel efficiency on tractor-trailers using synthetic jet-based active flow control

Science.gov (United States)

Amitay, Michael; Menicovich, David; Gallardo, Daniele

2016-04-01

The application of piezo-electrically-driven synthetic-jet-based active flow control to reduce drag on tractor-trailers was explored experimentally in wind tunnel testing as well as full-scale road tests. Aerodynamic drag accounts for more than 50% of the usable energy at highway speeds, a problem that applies primarily to trailer trucks. Therefore, a reduction in aerodynamic drag results in large saving of fuel and reduction in CO2 emissions. The active flow control technique that is being used relies on a modular system comprised of distributed, small, highly efficient actuators. These actuators, called synthetic jets, are jets that are synthesized at the edge of an orifice by a periodic motion of a piezoelectric diaphragm(s) mounted on one (or more) walls of a sealed cavity. The synthetic jet is zero net mass flux (ZNMF), but it allows momentum transfer to flow. It is typically driven near diaphragm and/or cavity resonance, and therefore, small electric input [O(10W)] is required. Another advantage of this actuator is that no plumbing is required. The system doesn't require changes to the body of the truck, can be easily reconfigured to various types of vehicles, and consumes small amounts of electrical power from the existing electrical system of the truck. Preliminary wind tunnel results showed up to 18% reduction in fuel consumption, whereas road tests also showed very promising results.

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

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.

Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows

Science.gov (United States)

Sammy, Mo

2010-01-01

Active flow control is often used to manipulate flow instabilities to achieve a desired goal (e.g. prevent separation, enhance mixing, reduce noise, etc.). Instability frequencies normally scale with flow velocity scale and inversely with flow length scale (U/l). In a laboratory setting for such flow experiments, U is high, but l is low, resulting in high instability frequency. In addition, high momentum and high background noise & turbulence in the flow necessitate high amplitude actuation. Developing a high amplitude and high frequency actuator is a major challenge. Ironically, these requirements ease up in application (but other issues arise).

First-In-Flight Full-Scale Application of Active Flow Control: The XV-15 Tiltrotor Download Reduction

National Research Council Canada - National Science Library

Nagib, Hassan M; Kiedaisch, John W; Wygnanski, Israel J; Stalker, Aaron D; Wood, Tom; McVeigh, Michael A

2004-01-01

... the effectiveness of Active flow Control (AFC) in reducing the download during hover. The flaps/ailerons were retrofitted with actuators delivering zero-mass-flux periodic jets emanating from slots positioned tangential to the surface...

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.

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.

Experimental Investigation of the Compressor Cascade under an Active Flow Control

Directory of Open Access Journals (Sweden)

Lukáč J.

2013-04-01

Full Text Available The paper is concerned with flow past compressor blade cascade (NACA 65 with thickened trailing edge at off-design regimes, which are characteristic by partial or complete flow separation on the suction surface of the blades. An attempt has been made to moderate the flow separation using continuous or periodic blowing from the sidewalls. The flow field was visualized using schlieren technique and surface paint visualization. The visualizations were complemented by measurement of the static pressure distribution on the suction surface of the blades. In agreement with the literature, the visualizations confirmed a complexity of the 3-dimensional flow separation, which was intensified by influence of the sidewall boundary layers developing from upstream parts of the test section. Furthermore, it was found out that the effect of both continuous and periodic blowing was rather minor. Finally, the results agree with the available literature showing that it is highly difficult to considerably control the complex 3-dimensional flow separation in the compressor cascade by control jets issuing (only from the sidewalls

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

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. This journal is © 2011 The Royal Society

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.

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

Flow Control Research at NASA Langley in Support of High-Lift Augmentation

Science.gov (United States)

Sellers, William L., III; Jones, Gregory S.; Moore, Mark D.

2002-01-01

The paper describes the efforts at NASA Langley to apply active and passive flow control techniques for improved high-lift systems, and advanced vehicle concepts utilizing powered high-lift techniques. The development of simplified high-lift systems utilizing active flow control is shown to provide significant weight and drag reduction benefits based on system studies. Active flow control that focuses on separation, and the development of advanced circulation control wings (CCW) utilizing unsteady excitation techniques will be discussed. The advanced CCW airfoils can provide multifunctional controls throughout the flight envelope. Computational and experimental data are shown to illustrate the benefits and issues with implementation of the technology.

The art and science of flow control

Science.gov (United States)

Gad-El-hak, Mohamed

1989-01-01

The ability to actively or passively manipulate a flow field to effect a desired change is of immense technological importance. In this article, methods of control to achieve transition delay, separation postponement, lift enhancement, drag reduction, turbulence augmentation, or noise suppression are considered. Emphasis is placed on external boundary-layer flows although applicability of some of the methods reviewed for internal flows will be mentioned. Attempts will be made to present a unified view of the different methods of control to achieve a variety of end results. Performance penalties associated with a particular method such as cost, complexity, or trade-off will be elaborated.

Plasma Control of Turbine Secondary Flows, Phase I

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...

Drag reduction of motor vehicles by active flow control using the Coanda effect

Science.gov (United States)

Geropp, D.; Odenthal, H.-J.

A test facility has been constructed to realistically simulate the flow around a two dimensional car shaped body in a wind tunnel. A moving belt simulator has been employed to generate the relative motion between model and ground. In a first step, the aerodynamic coefficients cL and cD of the model are determined using static pressure and force measurements. LDA-measurements behind the model show the large vortex and turbulence structures of the near and far wake. In a second step, the ambient flow around the model is modified by way of an active flow control which uses the Coanda effect, whereby the base-pressure increases by nearly 50% and the total drag can be reduced by 10%. The recirculating region is completely eliminated. The current work reveals the fundamental physical phenomena of the new method by observing the pressure forces on the model surface as well as the time averaged velocities and turbulence distributions for the near and far wake. A theory resting on this empirical information is developed and provides information about the effectiveness of the blowing method. For this, momentum and energy equations were applied to the flow around the vehicle to enable a validation of the theoretical results using experimental values.

Baseline Validation of Unstructured Grid Reynolds-Averaged Navier-Stokes Toward Flow Control

Science.gov (United States)

Joslin, Ronald D.; Viken, Sally A.

2001-01-01

The value of the use of the Reynolds-averaged Navier-Stokes methodology for active flow control applications is assessed. An experimental flow control database exists for a NACA0015 airfoil modified at the leading edge to implement a fluidic actuator; hence, this configuration is used. Computational results are documented for the baseline wing configuration (no control) with the experimental results and assumes two-dimensional flow. The baseline wing configuration has discontinuities at the leading edge, trailing edge, and aft of midchord on the upper surface. A limited number of active flow control applications have been tested in the laboratory and in flight. These applications include dynamic stall control using a deformable leading edge, separation control for takeoff and landing flight conditions using piezoelectric devices, pulsed vortex generators, zero-net-mass oscillations, and thrust vectoring with zero-net-mass piezoelectric-driven oscillatory actuation. As yet, there is no definitive comparison with experimental data that indicates current computational capabilities can quantitatively predict the large aerodynamic performance gains achieved with active flow control in the laboratory. However, one study using the Reynolds-averaged Navier-Stokes (RANS) methodology has shown good quantitative agreement with experimental results for an isolated zero-net-mass actuator. In addition, some recent studies have used RANS to demonstrate qualitative performance gains compared with the experimental data for separation control on an airfoil. Those quantitative comparisons for both baseline and flow control cases indicated that computational results were in poor quantitative agreement with the experiments. The current research thrust will investigate the potential use of an unstructured grid RANS approach to predict aerodynamic performance for active flow control applications building on the early studies. First the computational results must quantitatively match

Active Control of Flow around NACA 0015 Airfoil by Using DBD Plasma Actuator

Directory of Open Access Journals (Sweden)

Şanlısoy A.

2013-04-01

Full Text Available In this study, effect of plasma actuator on a flat plate and manipulation of flow separation on NACA0015 airfoil with plasma actuator at low Reynolds numbers were experimentally investigated. In the first section of the study, plasma actuator which consists of positive and grounded electrode couple and dielectric layer, located on a flat plate was actuated at different frequencies and peak to peak voltages in range of 3-5 kHz and 6-12 kV respectively. Theinduced air flow velocity on the surface of flat plate was measured by pitot tube at different locations behind the actuator. The influence of dielectricthickness and unsteady actuation with duty cycle was also examined. In the second section, the effect of plasma actuator on NACA0015 airfoil was studied atReynolds number 15000 and 30000. Four plasma actuators were placed at x/C = 0.1, 0.3, 0.5 and 0.9, and different electrode combinations were activated by sinusoidal signal. Flow visualizations were done when the attack angles were 0°, 5°, 10°, 15° and 20°. The results indicate that up to the 15° attack angle, the separated flow was reattached by plasma actuator at 12kV peak to peak voltage and 4 kHz frequency. However, 12 kVpp voltage was insufficient to reattach the flow at 20° angle of attack. The separated flow could be reattached by increasing the voltage up to 13 kV. Lift coefficient was also increased by the manipulated flow over the airfoil. Results showed that even high attack angles, the actuators can control the flow separation and prevent the airfoil from stall at low Reynolds numbers.

Locus of control in relation to flow

Directory of Open Access Journals (Sweden)

Celeste M Taylor

2006-04-01

Full Text Available The principal objective of the study was to examine the relationship between locus of control and optimal experience (flow in carrying out work and/or study activities. Two questionnaires measuring the aforementioned constructs were administered to a group of first and second-year Human Resource Management students (n=168 between the ages of 16 and 30. The results suggest that more frequent experience of flow is positively correlated with Autonomy and Internal Locus of Control. Limitations, lines of future research, implications and further contributions are discussed.

Defining Quantum Control Flow

OpenAIRE

Ying, Mingsheng; Yu, Nengkun; Feng, Yuan

2012-01-01

A remarkable difference between quantum and classical programs is that the control flow of the former can be either classical or quantum. One of the key issues in the theory of quantum programming languages is defining and understanding quantum control flow. A functional language with quantum control flow was defined by Altenkirch and Grattage [\\textit{Proc. LICS'05}, pp. 249-258]. This paper extends their work, and we introduce a general quantum control structure by defining three new quantu...

Experimental Studies of Low-Pressure Turbine Flows and Flow Control. Streamwise Pressure Profiles and Velocity Profiles

Science.gov (United States)

Volino, Ralph

2012-01-01

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

Geometry of thresholdless active flow in nematic microfluidics

Science.gov (United States)

Green, Richard; Toner, John; Vitelli, Vincenzo

2017-10-01

Active nematics are orientationally ordered but apolar fluids composed of interacting constituents individually powered by an internal source of energy. When activity exceeds a system-size-dependent threshold, spatially uniform active apolar fluids undergo a hydrodynamic instability leading to spontaneous macroscopic fluid flow. Here we show that a special class of spatially nonuniform configurations of such active apolar fluids display laminar (i.e., time-independent) flow even for arbitrarily small activity. We also show that two-dimensional active nematics confined on a surface of nonvanishing Gaussian curvature must necessarily experience a nonvanishing active force. This general conclusion follows from a key result of differential geometry: Geodesics must converge or diverge on surfaces with nonzero Gaussian curvature. We derive the conditions under which such curvature-induced active forces generate thresholdless flow for two-dimensional curved shells. We then extend our analysis to bulk systems and show how to induce thresholdless active flow by controlling the curvature of confining surfaces, external fields, or both. The resulting laminar flow fields are determined analytically in three experimentally realizable configurations that exemplify this general phenomenon: (i) toroidal shells with planar alignment, (ii) a cylinder with nonplanar boundary conditions, and (iii) a Frederiks cell that functions like a pump without moving parts. Our work suggests a robust design strategy for active microfluidic chips and could be tested with the recently discovered living liquid crystals.

Active flow control of the laminar separation bubble on a plunging airfoil near stall

Science.gov (United States)

Pande, Arth; Agate, Mark; Little, Jesse; Fasel, Hermann

2017-11-01

The effects of small amplitude (A/c = 0.048) high frequency (πfc/U∞ = 0.70) plunging motion on the X-56A airfoil are examined experimentally at Re = 200,000 for 12° angle of attack (CL,MAX = 12.25°) . The purpose of this research is to study the aerodynamic influence of structural motion when the wing is vibrating close to its eigenfrequency near static stall. Specific focus is placed on the laminar separation bubble (LSB) near the leading edge and its control via plasma actuation. In the baseline case, the leading edge bubble bursts during the oscillation cycle causing moment stall. A collaborative computational effort has shown that small amplitude forcing at a frequency that is most amplified by the primary instability of the LSB (FLSB+= 1, Fc+= 52) generates coherent spanwise vortices that entrain freestream momentum, thus reducing separation all while maintaining a laminar flow state. Results (PIV and surface pressure) indicate that a similar control mechanism is effective in the experiments. This is significant given the existence of freestream turbulence in the wind tunnel which has been shown to limit the efficacy of this active flow control technique in a model problem using Direct Numerical Simulation. The implications of these results are discussed.

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)

A magnetically actuated, high momentum rate MEMS pulsed microjet for active flow control

International Nuclear Information System (INIS)

Ducloux, O; Viard, R; Talbi, A; Pernod, P; Preobrazhensky, V; Gimeno, L; Merlen, A; Deblock, Y

2009-01-01

A small-sized, high momentum rate (>10 −2 N), dynamically actuated microvalve fulfilling the functional specifications for active aerodynamic flow control was designed, fabricated and characterized. The prototype consists of a microfabricated silicon channel pinched by an actuated poly(dimethyl siloxane) (PDMS) polymer membrane. Actuation is provided by coupling an inductive driving coil and a NdFeB permanent magnet fixed on the PDMS elastomeric membrane. The development of a specific microfabrication process, and a complete characterization of the fabricated prototypes are presented in this paper. The yield air microjet performances reach 150 m s −1 for an actuation frequency situated in the range [0 Hz–400 Hz] and an outlet area of about 1 mm 2 . Experimental results also show that the use of a vectoring plate placed at the outlet of the microvalve provided not only easier integration of the microsystem, but also improved the penetration of the microjet into the main flow

Feasibility of missile guidance using MEMS-based active flow control

International Nuclear Information System (INIS)

DeChamplain, A.; Hamel, N.; Rainville, P.-A.; Gosselin, P.; Wong, F.

2002-01-01

The aim of this study was to evaluate the feasibility to control a missile or rocket by mean of an active flow control device such as MEMS (Micro Electro Mechanical Systems) in the form of a microbubble. For this simple aerodynamic form coupled to the geometry of a generic missile, different microbubble arrangements can have a very significant impact in steady operation. Using CFD, combinations of different microbubble configurations (ratio between the apparent diameter and apparent height) and positions on the surface of the missile were evaluated for their impact on overall system performance for a missile flying at Mach 2.5 at an altitude of 6 km at a zero angle of attack. From a validation study with the generic missile geometry tested experimentally, the Fluent commercial code gave an excellent accuracy of 2% for the drag coefficient. With the appropriate numerical parameters from the validation, different configurations of microbubble(s) were simulated to give only marginal changes to the coefficient of moment as compared to experimental values at an angle of attack of 14 degrees. Considering the major advantages in weight and space savings, this would certainly be a technology to implement for small changes in guidance parameters. (author)

Liquid-Flow Controller With Trickle Preflow

Science.gov (United States)

Cox, George B., Jr.

1990-01-01

Liquid-flow controller allows pressure in liquid to increase steeply with flow as flow starts, then provides more-gradual nearly linear rise of pressure with flow as flow and pressure increase beyond preset breakpoint. Controller alternative version of mechanism described in "Liquid-Flow Controller Responds To Pressure" (MFS-28329) and "Liquid-Flow Controller With Preset Break Pressure" (MFS-28330). Material cut out of cone at tip of pintle. Liquid always passes from shell, albeit at low rate. When pressure in shell great enough to force orifice away from pintle, liquid flows at greater rate.

Fluid flow control system

International Nuclear Information System (INIS)

Rion, Jacky.

1982-01-01

Fluid flow control system featuring a series of grids placed perpendicular to the fluid flow direction, characterized by the fact that it is formed of a stack of identical and continuous grids, each of which consists of identical meshes forming a flat lattice. The said meshes are offset from one grid to the next. This system applies in particular to flow control of the coolant flowing at the foot of an assembly of a liquid metal cooled nuclear reactor [fr

Reactive Flow Control of Delta Wing Vortex (Postprint)

Science.gov (United States)

2006-08-01

wing aircraft. A substantial amount of research has been dedicated to the control of aerodynamic flows using both passive and active control mechanisms...Passive vortex control devices such as vortex generators and winglets attach to the wing and require no energy input. Passive vortex control...leading edges is also effective for changing the aerodynamic characteristics of delta wings [2] [3]. Gutmark and Guillot [5] proposed controlling

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.

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.

Flow Characteristics of Ground Vehicle Wake and Its Response to Flow Control

Science.gov (United States)

Sellappan, Prabu; McNally, Jonathan; Alvi, Farrukh

2017-11-01

Air pollution, fuel shortages, and cost savings are some of the many incentives for improving the aerodynamics of vehicles. Reducing wake-induced aerodynamic drag, which is dependent on flow topology, on modern passenger vehicles is important for improving fuel consumption rates which directly affect the environment. In this research, an active flow control technique is applied on a generic ground vehicle, a 25°Ahmed model, to investigate its effect on the flow topology in the near-wake. The flow field of this canonical bluff body is extremely rich, with complex and unsteady flow features such as trailing wake vortices and c-pillar vortices. The spatio-temporal response of these flow features to the application of steady microjet actuators is investigated. The responses are characterized independently through time-resolved and volumetric velocity field measurements. The accuracy and cost of volumetric measurements in this complex flow field through Stereoscopic- and Tomographic- Particle Image Velocimetry (PIV) will also be commented upon. National Science Foundation PIRE Program.

Information transmission and signal permutation in active flow networks

Science.gov (United States)

Woodhouse, Francis G.; Fawcett, Joanna B.; Dunkel, Jörn

2018-03-01

Recent experiments show that both natural and artificial microswimmers in narrow channel-like geometries will self-organise to form steady, directed flows. This suggests that networks of flowing active matter could function as novel autonomous microfluidic devices. However, little is known about how information propagates through these far-from-equilibrium systems. Through a mathematical analogy with spin-ice vertex models, we investigate here the input–output characteristics of generic incompressible active flow networks (AFNs). Our analysis shows that information transport through an AFN is inherently different from conventional pressure or voltage driven networks. Active flows on hexagonal arrays preserve input information over longer distances than their passive counterparts and are highly sensitive to bulk topological defects, whose presence can be inferred from marginal input–output distributions alone. This sensitivity further allows controlled permutations on parallel inputs, revealing an unexpected link between active matter and group theory that can guide new microfluidic mixing strategies facilitated by active matter and aid the design of generic autonomous information transport networks.

Active control of noise amplification in the flow over a square leading-edge flat plate utilizing DBD plasma actuator

Science.gov (United States)

Yadong, HUANG; Benmou, ZHOU

2018-05-01

Perturbation is generally considered as the flow noise, and its energy can gain transient growth in the separation bubble. The amplified perturbations may cause unstable Kelvin–Helmohltz vortices which induce the three-dimensional transition. Active control of noise amplification via dielectric barrier discharge plasma actuator in the flow over a square leading-edge flat plate is numerically studied. The actuator is installed near the plate leading-edge where the separation bubble is formed. The maximum energy amplification of perturbations is positively correlated with the separation bubble scale which decreases with the increasing control parameters. As the magnitude of noise amplification is reduced, the laminar-turbulent transition is successfully suppressed.

Novel Active Combustion Control Valve

Science.gov (United States)

Caspermeyer, Matt

2014-01-01

This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

Nocturnal insects use optic flow for flight control

OpenAIRE

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

2011-01-01

To avoid collisions when navigating through cluttered environments, flying insects must control their flight so that their sensory systems have time to detect obstacles and avoid them. To do this, day-active insects rely primarily on the pattern of apparent motion generated on the retina during flight (optic flow). However, many flying insects are active at night, when obtaining reliable visual information for flight control presents much more of a challenge. To assess whether nocturnal flyin...

Active load control techniques for wind turbines.

Energy Technology Data Exchange (ETDEWEB)

van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.; Johnson, Scott J. (University of California, Davis, CA)

2008-07-01

This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

Active Control of Jet Engine Inlet Flows

National Research Council Canada - National Science Library

Rediniotis, Othon; Bowersox, Rodney; Kirk, Aaron; Kumar, Abhinav; Tichenor, Nathan

2007-01-01

...), flow visualization tests, particle image velocimetry (PIV), pressure probe and wall static tap experiments at various locations, the development and evolution of the secondary flow structures were observed...

An Autonomous Sensor System Architecture for Active Flow and Noise Control Feedback

Science.gov (United States)

Humphreys, William M, Jr.; Culliton, William G.

2008-01-01

Multi-channel sensor fusion represents a powerful technique to simply and efficiently extract information from complex phenomena. While the technique has traditionally been used for military target tracking and situational awareness, a study has been successfully completed that demonstrates that sensor fusion can be applied equally well to aerodynamic applications. A prototype autonomous hardware processor was successfully designed and used to detect in real-time the two-dimensional flow reattachment location generated by a simple separated-flow wind tunnel model. The success of this demonstration illustrates the feasibility of using autonomous sensor processing architectures to enhance flow control feedback signal generation.

Active flow control insight gained from a modified integral boundary layer equation

Science.gov (United States)

Seifert, Avraham

2016-11-01

Active Flow Control (AFC) can alter the development of boundary layers with applications (e.g., reducing drag by separation delay or separating the boundary layers and enhancing vortex shedding to increase drag). Historically, significant effects of steady AFC methods were observed. Unsteady actuation is significantly more efficient than steady. Full-scale AFC tests were conducted with varying levels of success. While clearly relevant to industry, AFC implementation relies on expert knowledge with proven intuition and or costly and lengthy computational efforts. This situation hinders the use of AFC while simple, quick and reliable design method is absent. An updated form of the unsteady integral boundary layer (UIBL) equations, that include AFC terms (unsteady wall transpiration and body forces) can be used to assist in AFC analysis and design. With these equations and given a family of suitable velocity profiles, the momentum thickness can be calculated and matched with an outer, potential flow solution in 2D and 3D manner to create an AFC design tool, parallel to proven tools for airfoil design. Limiting cases of the UIBL equation can be used to analyze candidate AFC concepts in terms of their capability to modify the boundary layers development and system performance.

Content dependent information flow control

DEFF Research Database (Denmark)

Nielson, Hanne Riis; Nielson, Flemming

2017-01-01

Information flow control extends access control by not only regulating who is allowed to access what data but also the subsequent use of the data. Applications within communications systems require such information flow control to be dependent on the actual contents of the data. We develop...

RANS Simulation of the Separated Flow over a Bump with Active Control

Science.gov (United States)

Iaccarino, Gianluca; Marongiu, Claudio; Catalano, Pietro; Amato, Marcello

2003-01-01

The objective of this paper is to investigate the accuracy of Reynolds-Averaged Navier- Stokes (RANS) techniques in predicting the effect of steady and unsteady flow control devices. This is part of a larger effort in applying numerical simulation tools to investigate of the performance of synthetic jets in high Reynolds number turbulent flows. RANS techniques have been successful in predicting isolated synthetic jets as reported by Kral et al. Nevertheless, due to the complex, and inherently unsteady nature of the interaction between the synthetic jet and the external boundary layer flow, it is not clear whether RANS models can represent the turbulence statistics correctly.

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...

Redox active polymers and colloidal particles for flow batteries

Science.gov (United States)

Gavvalapalli, Nagarjuna; Moore, Jeffrey S.; Rodriguez-Lopez, Joaquin; Cheng, Kevin; Shen, Mei; Lichtenstein, Timothy

2018-05-29

The invention provides a redox flow battery comprising a microporous or nanoporous size-exclusion membrane, wherein one cell of the battery contains a redox-active polymer dissolved in the non-aqueous solvent or a redox-active colloidal particle dispersed in the non-aqueous solvent. The redox flow battery provides enhanced ionic conductivity across the electrolyte separator and reduced redox-active species crossover, thereby improving the performance and enabling widespread utilization. Redox active poly(vinylbenzyl ethylviologen) (RAPs) and redox active colloidal particles (RACs) were prepared and were found to be highly effective redox species. Controlled potential bulk electrolysis indicates that 94-99% of the nominal charge on different RAPs is accessible and the electrolysis products are stable upon cycling. The high concentration attainable (>2.0 M) for RAPs in common non-aqueous battery solvents, their electrochemical and chemical reversibility, and their hindered transport across porous separators make them attractive materials for non-aqueous redox flow batteries based on size-selectivity.

Active Flow Control in a Radial Vaned Diffuser for Surge Margin Improvement: A Multislot Suction Strategy

Directory of Open Access Journals (Sweden)

Aurélien Marsan

2017-01-01

Full Text Available This work is the final step of a research project that aims at evaluating the possibility of delaying the surge of a centrifugal compressor stage using a boundary-layer suction technique. It is based on Reynolds-Averaged Navier-Stokes numerical simulations. Boundary-layer suction is applied within the radial vaned diffuser. Previous work has shown the necessity to take into account the unsteady behavior of the flow when designing the active flow control technique. In this paper, a multislot strategy is designed according to the characteristics of the unsteady pressure field. Its implementation results in a significant increase of the stable operating range predicted by the unsteady RANS numerical model. A hub-corner separation still exists further downstream in the diffuser passage but does not compromise the stability of the compressor stage.

Implementation of Real-Time Feedback Flow Control Algorithms on a Canonical Testbed

Science.gov (United States)

Tian, Ye; Song, Qi; Cattafesta, Louis

2005-01-01

This report summarizes the activities on "Implementation of Real-Time Feedback Flow Control Algorithms on a Canonical Testbed." The work summarized consists primarily of two parts. The first part summarizes our previous work and the extensions to adaptive ID and control algorithms. The second part concentrates on the validation of adaptive algorithms by applying them to a vibration beam test bed. Extensions to flow control problems are discussed.

Electromagnetic application device for flow rate/flow speed control

International Nuclear Information System (INIS)

Yoshioka, Senji.

1994-01-01

Electric current and magnetic field are at first generated in a direction perpendicular to a flow channel of a fluid, and forces generated by electromagnetic interaction of the current and the magnetic field are combined and exerted on the fluid, to control the flow rate and the flow speed thereby decreasing flowing pressure loss. In addition, an electric current generation means and a magnetic field generation means integrated together are disposed to a structural component constituting the flow channel, and they are combined to attain the aimed effect. The current generating means forms a potential difference by supplying electric power to a pair of electrodes as a cathode and an anode by using structures disposed along the channel, to generate an electric field or electric current in a direction perpendicular to the flow channel. The magnetic field generating means forms a counter current (reciprocal current) by using structures disposed along the flow channel, to generate synthesized or emphasized magnetic field. The fluid can be applied with a force in the direction of the flowing direction by the electromagnetic interaction of the electric current and the magnetic field, thereby capable of propelling the fluid. Accordingly, the flowrate/flowing speed can be controlled inside of the flow channel and flowing pressure loss can be decreased. (N.H.)

Efficiency improvements of electromagnetic flow control

International Nuclear Information System (INIS)

Spong, E.; Reizes, J.A.; Leonardi, E.

2005-01-01

In turbulent flow, frictional resistance and heat transfer are controlled to a large degree by the intensity of the turbulence fluctuations in the near vicinity of a surface. In the case of a weak electrically conducting fluid, such as seawater, turbulence intensity can be controlled by subjecting the fluid to electromagnetic fields. This technique, known as Electro-magneto-hydro-dynamic (EMHD) flow control, has been shown to have promise as a means of reducing the turbulence intensity, and hence heat transfer or frictional drag of turbulent boundary layers. Unfortunately EMHD flow control currently suffers from poor efficiency due to the high energy requirements of the electromagnetic field. A numerical study has been conducted in which a new electromagnetic actuator design has been developed to provide a more efficient spatial distribution of the electromagnetic forces. The new actuator design has then been coupled to an ideal flow sensor. A flow control subroutine, embedded in the numerical model, uses the velocity information from the ideal sensor to determine the appropriate actuating force to apply to the flow at each time step. The new actuator design has been shown to be capable of successfully attenuating a sequence of artificial low speed streaks in a simplified model of a low Reynolds number turbulent boundary layer. Thus, a potential solution to the poor efficiency of EMHD flow control has been offered by providing the means whereby the expensive electromagnetic forces can be strategically and sparingly applied to the flow

Characterization of an Actively Controlled Three-Dimensional Turret Wake

Science.gov (United States)

Shea, Patrick; Glauser, Mark

2012-11-01

Three-dimensional turrets are commonly used for housing optical systems on airborne platforms. As bluff bodies, these geometries generate highly turbulent wakes that decrease the performance of the optical systems and the aircraft. The current experimental study looked to use dynamic suction in both open and closed-loop control configurations to actively control the turret wake. The flow field was characterized using dynamic pressure and stereoscopic PIV measurements in the wake of the turret. Results showed that the suction system was able to manipulate the wake region of the turret and could alter not only the spatial structure of the wake, but also the temporal behavior of the wake flow field. Closed-loop, feedback control techniques were used to determine a more optimal control input for the flow control. Similar control effects were seen for both the steady open-loop control case and the closed-loop feedback control configuration with a 45% reduction in the suction levels when comparing the closed-loop to the open-loop case. These results provide unique information regarding the development of the baseline three-dimensional wake and the wake with three different active flow control configurations.

Improved oxygen-activation method for determining water flow behind casing

International Nuclear Information System (INIS)

McKeon, D.C.; Scott, H.D.; Olesen, J.R.; Patton, G.L.; Mitchell, R.J.

1991-01-01

This paper reports on impulse activation which is a new oxygen-activation technique developed to detect vertical water flow and to provide a quantitative measure of water flow velocity and flow rate. Flow-loop measurements made over a wide range of water velocities are in good agreement with theoretical predictions. Measurements of up- and downward channel flow were made at the U.S. Environmental Protection Agency (EPA) leak test well in Ada, OK, to demonstrate the technique in a controlled environment and to confirm that EPA requirements have been met. A major advantage of this method over previous procedures is that a measurement is a known zero-flow zone is not required. The impulse-activation technique has improved sensitivity to both low and high flow rates. In the EPA leak test well, the technique successfully discriminated between 0- and 1.4 ft/min flow conditions. The lowest quantified velocity was 1.8 ft/min or 10 BWPD, significantly below the EPA requirement of 3 ft/min. The upper limit of detection has not been determined by exceeds 137 ft/min. The water flow log (WFL SM ) measurement uses the impulse-activation technique and a Dual-Bust SM , thermal-decay-time (TDT SM ) tool to detect water flow behind casing. An important application of this measurement is testing for fluid migration in the wellbore as part of the mechanical integrity testing process for Class I and II disposal wells. The new oxygen-activation measurement was used in numerous production wells to identify the presence of water flow behind casing. Additional applications include the identification of open fractures in horizontal wells and the quantification of water flow in the tubing/casing annulus in injection and production wells

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.

Integrated soft sensor model for flow control.

Science.gov (United States)

Aijälä, G; Lumley, D

2006-01-01

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

Active Control of Fan Noise: Feasibility Study. Volume 6; Theoretical Analysis for Coupling of Active Noise Control Actuator Ring Sources to an Annular Duct with Flow

Science.gov (United States)

Kraft, R. E.

1996-01-01

The objective of this effort is to develop an analytical model for the coupling of active noise control (ANC) piston-type actuators that are mounted flush to the inner and outer walls of an annular duct to the modes in the duct generated by the actuator motion. The analysis will be used to couple the ANC actuators to the modal analysis propagation computer program for the annular duct, to predict the effects of active suppression of fan-generated engine noise sources. This combined program will then be available to assist in the design or evaluation of ANC systems in fan engine annular exhaust ducts. An analysis has been developed to predict the modes generated in an annular duct due to the coupling of flush-mounted ring actuators on the inner and outer walls of the duct. The analysis has been combined with a previous analysis for the coupling of modes to a cylindrical duct in a FORTRAN computer program to perform the computations. The method includes the effects of uniform mean flow in the duct. The program can be used for design or evaluation purposes for active noise control hardware for turbofan engines. Predictions for some sample cases modeled after the geometry of the NASA Lewis ANC Fan indicate very efficient coupling in both the inlet and exhaust ducts for the m = 6 spinning mode at frequencies where only a single radial mode is cut-on. Radial mode content in higher order cut-off modes at the source plane and the required actuator displacement amplitude to achieve 110 dB SPL levels in the desired mode were predicted. Equivalent cases with and without flow were examined for the cylindrical and annular geometry, and little difference was found for a duct flow Mach number of 0.1. The actuator ring coupling program will be adapted as a subroutine to the cylindrical duct modal analysis and the exhaust duct modal analysis. This will allow the fan source to be defined in terms of characteristic modes at the fan source plane and predict the propagation to the

Strategic Management Accounting in Organizations’ Cash Flow Control

Directory of Open Access Journals (Sweden)

Y. P. Vetrov

2017-09-01

Full Text Available The article deals with the various interpretations of the term "strategic management accounting". The role and importance of strategic management accounting in the organization’s cash flows control are investigated. The accounting and analytical models of strategic management accounting are analyzed. The territorial scope of this article covers the Russian Federation. The study concludes that the system of assessment parameters of organization’s financial condition should cover all its aspects, namely, financial sustainability, solvency, liquidity and business activity. Hence, strategic management accounting of cash flows makes it possible to correctly set information base to monitor financial flows of a company which responds the tends of market economy and allows to make optimal management decisions.

Vibration-accelerated activation of flow units in a Pd-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Li, Ning, E-mail: hslining@mail.hust.edu.cn [School of Materials Science and Engineering, and State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Liu, Ze [Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Wang, Xinyun [School of Materials Science and Engineering, and State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang, Meng [Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou 510632 (China)

2017-04-24

Controlled activation of flow units and in-situ characterization of mechanical properties in metallic glasses are facing challenges thus far. Here, vibrational loading is introduced through nanoscale dynamic mechanical analysis technique to probe vibration-accelerated atomic level flow that plays a crucial role in the mechanical behavior of metallic glasses. The intriguing finding is that high vibrational frequency induces deep indentation depth, prominent pop-in events on load–depth curves and low storage modulus, exhibiting a vibration-facilitated activation of flow units in Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} metallic glass. Theoretical analysis revealed that vibration-moderated activation time-scale accelerate the activation of flow units and responsible for the above scenario.

Experimental investigation of an actively controlled three-dimensional turret wake

Science.gov (United States)

Shea, Patrick R.

Hemispherical turrets are bluff bodies commonly used to house optical systems on airborne platforms. These bluff bodies develop complex, three-dimensional flow fields that introduce high mean and fluctuating loads to the turret as well as the airframe support structure which reduce the performance of both the optical systems and the aircraft. An experimental investigation of the wake of a three-dimensional, non-conformal turret was performed in a low-speed wind tunnel at Syracuse University to develop a better understanding of the fundamental flow physics associated with the turret wake. The flow field was studied at a diameter based Reynolds number of 550,000 using stereoscopic particle image velocimetry and dynamic pressure measurements both with and without active flow control. Pressure measurements were simultaneously sampled with the PIV measurements and taken on the surrounding boundary layer plate and at several locations on the turret geometry. Active flow control of the turret wake was performed around the leading edge of the turret aperture using dynamic suction in steady open-loop, unsteady open-loop, and simple closed-loop configurations. Analysis of the uncontrolled wake provided insight into the complex three-dimensional wake when evaluated spatially using PIV measurements and temporally using spectral analysis of the pressure measurements. Steady open-loop suction was found to significantly alter the spatial and temporal nature of the turret wake despite the control being applied locally to the aperture region of the turret. Unsteady open-loop and simple closed-loop control were found to provide similar levels of control to the steady open-loop forcing with a 45% reduction in the control input as calculated using the jet momentum coefficient. The data set collected provides unique information regarding the development of the baseline three-dimensional wake and the wake with three different active flow control configurations. These data can be used to

Electrogates for stop-and-go control of liquid flow in microfluidics

Science.gov (United States)

Arango, Y.; Temiz, Y.; Gökçe, O.; Delamarche, E.

2018-04-01

Diagnostics based on microfluidic devices necessitate specific reagents, flow conditions, and kinetics for optimal performance. Such an optimization is often achieved using assay-specific microfluidic chip designs or systems with external liquid pumps. Here, we present "electrogates" for stop-and-go control of flow of liquids in capillary-driven microfluidic chips by combining liquid pinning and electrowetting. Electrogates are simple to fabricate and efficient: a sample pipetted to a microfluidic chip flows autonomously in 15-μm-deep hydrophilic channels until the liquid meniscus is pinned at the edge of a 1.5-μm-deep trench patterned at the bottom of a rectangular microchannel. The flow can then be resumed by applying a DC voltage between the liquid and the trench via integrated electrodes. Using a trench geometry with a semicircular shape, we show that retention times longer than 30 min are achieved for various aqueous solutions such as biological buffers, artificial urine, and human serum. We studied the activation voltage and activation delay of electrogates using a chip architecture having 6 independent flow paths and experimentally showed that the flow can be resumed in less than 1 s for voltages smaller than 10 V, making this technique compatible with low-power and portable microfluidic systems. Electrogates therefore can make capillary-driven microfluidic chips very versatile by adding flow control in microfluidic channels in a flexible manner.

Active control of the jet in coaxial arrangement

Directory of Open Access Journals (Sweden)

Šafařík P.

2013-04-01

Full Text Available An axisymmetric jet flow, issuing as a fully developed flow from a long straight pipe at Re = 1600 and 5500, was actively controlled by an annular synthetic jet. The Pitot tube, hot-wire anemometry (CTA and flow visualization were used for an experimental investigation of the flow control. The working fluid was air. The effect of varying Strouhal number (St = (0.18÷1.94 on a width and entrainment of the main jet flow was studied. It was found that the main jet is the most sensitive to the actuation at St = 0.28÷0.60 and St = 0.18, for Re = 1600 and Re = 5500, respectively.

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)

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.

Computational Modeling of Flow Control Systems for Aerospace Vehicles, Phase I

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...

Flow Control Over Sharp-Edged Wings

Science.gov (United States)

2007-07-01

Gad-el-Hak (2001) as the ability to actively or passively manipulate a flow field to effect a desired change. The challenge is to achieve that change...combinations. Been able to independently control both is a great challenge . These requirements may appear too stringent for the sharp- edged airfoils...06 0𔄁 08 09 lic Vlc Figure 22: Pressure distributions for Model B at a=13 °. Stations I (left); 2 (right) 1 , -2 1 F - [12 1 -6a -16 08 -08 06 -06

Adaptive optimization for active queue management supporting TCP flows

NARCIS (Netherlands)

Baldi, S.; Kosmatopoulos, Elias B.; Pitsillides, Andreas; Lestas, Marios; Ioannou, Petros A.; Wan, Y.; Chiu, George; Johnson, Katie; Abramovitch, Danny

2016-01-01

An adaptive decentralized strategy for active queue management of TCP flows over communication networks is presented. The proposed strategy solves locally, at each link, an optimal control problem, minimizing a cost composed of residual capacity and buffer queue size. The solution of the optimal

Formal Verification of Effectiveness of Control Activities in Business Processes

Science.gov (United States)

Arimoto, Yasuhito; Iida, Shusaku; Futatsugi, Kokichi

It has been an important issue to deal with risks in business processes for achieving companies' goals. This paper introduces a method for applying a formal method to analysis of risks and control activities in business processes in order to evaluate control activities consistently, exhaustively, and to give us potential to have scientific discussion on the result of the evaluation. We focus on document flows in business activities and control activities and risks related to documents because documents play important roles in business. In our method, document flows including control activities are modeled and it is verified by OTS/CafeOBJ Method that risks about falsification of documents are avoided by control activities in the model. The verification is done by interaction between humans and CafeOBJ system with theorem proving, and it raises potential to discuss the result scientifically because the interaction gives us rigorous reasons why the result is derived from the verification.

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.

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...

Compressed-air flow control system.

Science.gov (United States)

Bong, Ki Wan; Chapin, Stephen C; Pregibon, Daniel C; Baah, David; Floyd-Smith, Tamara M; Doyle, Patrick S

2011-02-21

We present the construction and operation of a compressed-air driven flow system that can be used for a variety of microfluidic applications that require rapid dynamic response and precise control of multiple inlet streams. With the use of inexpensive and readily available parts, we describe how to assemble this versatile control system and further explore its utility in continuous- and pulsed-flow microfluidic procedures for the synthesis and analysis of microparticles.

Neural control of adrenal medullary and cortical blood flow during hemorrhage

International Nuclear Information System (INIS)

Breslow, M.J.; Jordan, D.A.; Thellman, S.T.; Traystman, R.J.

1987-01-01

Hemorrhagic hypotension produces an increase in adrenal medullary blood flow and a decrease in adrenal cortical blood flow. To determine whether changes in adrenal blood flow during hemorrhage are neurally mediated, the authors compared blood flow responses following adrenal denervation (splanchnic nerve section) with changes in the contralateral, neurally intact adrenal. Carbonized microspheres labeled with 153 Gd, 114 In, 113 Sn, 103 Ru, 95 Nb or 46 Se were used. Blood pressure was reduced and maintained at 60 mmHg for 25 min by hemorrhage into a pressurized bottle system. Adrenal cortical blood flow decreased to 50% of control with hemorrhage in both the intact and denervated adrenal. Adrenal medullary blood flow increased to four times control levels at 15 and 25 min posthemorrhage in the intact adrenal, but was reduced to 50% of control at 3, 5, and 10 min posthemorrhage in the denervated adrenal. In a separate group of dogs, the greater splanchnic nerve on one side was electrically stimulated at 2, 5, or 15 Hz for 40 min. Adrenal medullary blood flow increased 5- to 10-fold in the stimulated adrenal but was unchanged in the contralateral, nonstimulated adrenal. Adrenal cortical blood flow was not affected by nerve stimulation. They conclude that activity of the splanchnic nerve profoundly affects adrenal medullary vessels but not adrenal cortical vessels and mediates the observed increase in adrenal medullary blood flow during hemorrhagic hypotension

Flow control for oblique shock wave reflections

OpenAIRE

Giepman, R.H.M.

2016-01-01

Shock wave-boundary layer interactions are prevalent in many aerospace applications that involve transonic or supersonic flows. Such interactions may lead to boundary layer separation, flow unsteadiness and substantial losses in the total pressure. Flow control techniques can help to mitigate these adverse effects and stabilize the interaction. This thesis focuses on passive flow control techniques for oblique shock wave reflections on flat plates and presents experimental results for both la...

Parallel Vortex Body Interaction Enabled by Active Flow Control

Science.gov (United States)

Weingaertner, Andre; Tewes, Philipp; Little, Jesse

2017-11-01

An experimental study was conducted to explore the flow physics of parallel vortex body interaction between two NACA 0012 airfoils. Experiments were carried out at chord Reynolds numbers of 740,000. Initially, the leading airfoil was characterized without the target one being installed. Results are in good agreement with thin airfoil theory and data provided in the literature. Afterward, the leading airfoil was fixed at 18° incidence and the target airfoil was installed 6 chord lengths downstream. Plasma actuation (ns-DBD), originating close to the leading edge, was used to control vortex shedding from the leading airfoil at various frequencies (0.04 governing parameters of this vortex body interaction are explored. This work was supported by the Army Research Office under ARO Grant No. W911NF-14-1-0662.

Numerical study of flow control strategies for a simplified square back ground vehicle

Energy Technology Data Exchange (ETDEWEB)

Eulalie, Yoann; Gilotte, Philippe [Plastic Omnium, Avenue du bois des vergnes, F-01150 Sainte-Julie (France); Mortazavi, Iraj, E-mail: iraj.mortazavi@cnam.fr [Team M2N, CNAM Paris, 292 Rue St. Martin, 75003 Paris (France)

2017-06-15

Current automotive trends lead to vertical shapes in the region of the rear tailgates, which induce high aerodynamical losses at the rear wall of vehicles. It is therefore important to work on turbulent wake in order to find drag reduction solutions for the current vehicle design. This paper focuses on flow control strategies, which are designed to interact with shear layers backward from the detachment region, in order to increase pressure values in the wake of a square back bluff body. This study involves large eddy simulation results validated by experimental data. After the first section, which represents experimental validation of LES computations with and without active flow control on an Ahmed bluff body, we will present a wide range of numerical results describing several active and passive flow control solutions leading to drag reductions of up to 10%. The last part of this paper will focus on some fluid mechanisms, which could explain these aerodynamical performances. (paper)

Numerical study of flow control strategies for a simplified square back ground vehicle

International Nuclear Information System (INIS)

Eulalie, Yoann; Gilotte, Philippe; Mortazavi, Iraj

2017-01-01

Current automotive trends lead to vertical shapes in the region of the rear tailgates, which induce high aerodynamical losses at the rear wall of vehicles. It is therefore important to work on turbulent wake in order to find drag reduction solutions for the current vehicle design. This paper focuses on flow control strategies, which are designed to interact with shear layers backward from the detachment region, in order to increase pressure values in the wake of a square back bluff body. This study involves large eddy simulation results validated by experimental data. After the first section, which represents experimental validation of LES computations with and without active flow control on an Ahmed bluff body, we will present a wide range of numerical results describing several active and passive flow control solutions leading to drag reductions of up to 10%. The last part of this paper will focus on some fluid mechanisms, which could explain these aerodynamical performances. (paper)

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.

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.

Skin-friction drag reduction in turbulent channel flow based on streamwise shear control

International Nuclear Information System (INIS)

Kim, Jung Hoon; Lee, Jae Hwa

2017-01-01

Highlights: • We perform DNSs of fully developed turbulent channel flows to explore an active flow control concept using streamwise velocity shear control at the wall. • The structural spacing and wall amplitude parameters are systematically changed to achieve a high-efficient drag reduction rate for longitudinal control surface. • Significant drag reduction is observed with an increase in the two parameters with an accompanying reduction of the Reynolds stresses and vorticity fluctuations. • The generation and evolution of the turbulent vortices in the absence of velocity shear and how they contribute to DR have been examined. - Abstract: It is known that stretching and intensification of a hairpin vortex by mean shear play an important role to create a hairpin vortex packet, which generates the large Reynolds shear stress associated with skin-friction drag in wall-bounded turbulent flows. In order to suppress the mean shear at the wall for high efficient drag reduction (DR), in the present study, we explore an active flow control concept using streamwise shear control (SSC) at the wall. The longitudinal control surface is periodically spanwise-arranged with no-control surface while varying the structural spacing, and an amplitude parameter for imposing the strength of the actuating streamwise velocity at the wall is introduced to further enhance the skin-friction DR. Significant DR is observed with an increase in the two parameters with an accompanying reduction of the Reynolds stresses and vorticity fluctuations, although a further increase in the parameters amplifies the turbulence activity in the near-wall region. In order to study the direct relationship between turbulent vortical structures and DR under the SSC, temporal evolution with initial eddies extracted by conditional averages for Reynolds-stress-maximizing Q2 events are examined. It is shown that the generation of new vortices is dramatically inhibited with an increase in the parameters

Active control of massively separated high-speed/base flows with electric arc plasma actuators

Science.gov (United States)

DeBlauw, Bradley G.

The current project was undertaken to evaluate the effects of electric arc plasma actuators on high-speed separated flows. Two underlying goals motivated these experiments. The first goal was to provide a flow control technique that will result in enhanced flight performance for supersonic vehicles by altering the near-wake characteristics. The second goal was to gain a broader and more sophisticated understanding of these complex, supersonic, massively-separated, compressible, and turbulent flow fields. The attainment of the proposed objectives was facilitated through energy deposition from multiple electric-arc plasma discharges near the base corner separation point. The control authority of electric arc plasma actuators on a supersonic axisymmetric base flow was evaluated for several actuator geometries, frequencies, forcing modes, duty cycles/on-times, and currents. Initially, an electric arc plasma actuator power supply and control system were constructed to generate the arcs. Experiments were performed to evaluate the operational characteristics, electromagnetic emission, and fluidic effect of the actuators in quiescent ambient air. The maximum velocity induced by the arc when formed in a 5 mm x 1.6 mm x 2 mm deep cavity was about 40 m/s. During breakdown, the electromagnetic emission exhibited a rise and fall in intensity over a period of about 340 ns. After breakdown, the emission stabilized to a near-constant distribution. It was also observed that the plasma formed into two different modes: "high-voltage" and "low-voltage". It is believed that the plasma may be switching between an arc discharge and a glow discharge for these different modes. The two types of plasma do not appear to cause substantial differences on the induced fluidic effects of the actuator. In general, the characterization study provided a greater fundamental understanding of the operation of the actuators, as well as data for computational model comparison. Preliminary investigations

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...... recognized that neurotransmitter-mediated signalling has a key role in regulating cerebral blood flow, that much of this control is mediated by astrocytes, that oxygen modulates blood flow regulation, and that blood flow may be controlled by capillaries as well as by arterioles. These conceptual shifts...

Effect of Flow Rate Controller on Liquid Steel Flow in Continuous Casting Mold using Numerical Modeling

Science.gov (United States)

Gursoy, Kadir Ali; Yavuz, Mehmet Metin

2014-11-01

In continuous casting operation of steel, the flow through tundish to the mold can be controlled by different flow rate control systems including stopper rod and slide-gate. Ladle changes in continuous casting machines result in liquid steel level changes in tundishes. During this transient event of production, the flow rate controller opening is increased to reduce the pressure drop across the opening which helps to keep the mass flow rate at the desired level for the reduced liquid steel level in tundish. In the present study, computational fluid dynamic (CFD) models are developed to investigate the effect of flow rate controller on mold flow structure, and particularly to understand the effect of flow controller opening on meniscus flow. First, a detailed validation of the CFD models is conducted using available experimental data and the performances of different turbulence models are compared. Then, the constant throughput casting operations for different flow rate controller openings are simulated to quantify the opening effect on meniscus region. The results indicate that the meniscus velocities are significantly affected by the flow rate controller and its opening level. The steady state operations, specified as constant throughput casting, do not provide the same mold flow if the controller opening is altered. Thus, for quality and castability purposes, adjusting the flow controller opening to obtain the fixed mold flow structure is proposed. Supported by Middle East Technical University (METU) BAP (Scientific Research Projects) Coordination.

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...

Flow visualization of two-phase flows using photochromic dye activation method

International Nuclear Information System (INIS)

Kawaji, M.; Ahmad, W.; DeJesus, J.M.; Sutharshan, B.; Lorencez, C.; Ojha, M.

1993-01-01

A non-intrusive flow visualization technique based on light activation of photochromic dye material has been used to obtain velocity profiles in gas-liquid flows including annular, slug and stratified flows. The preliminary results revealed several important two-phase flow mechanisms that have not been clearly seen previously. (orig.)

Neural control of blood flow during exercise in human metabolic syndrome.

Science.gov (United States)

Limberg, Jacqueline K; Morgan, Barbara J; Sebranek, Joshua J; Proctor, Lester T; Eldridge, Marlowe W; Schrage, William G

2014-09-01

α-Adrenergic-mediated vasoconstriction is greater during simulated exercise in animal models of metabolic syndrome (MetSyn) when compared with control animals. In an attempt to translate such findings to humans, we hypothesized that adults with MetSyn (n = 14, 35 ± 3 years old) would exhibit greater α-adrenergic responsiveness during exercise when compared with age-matched healthy control subjects (n = 16, 31 ± 3 years old). We measured muscle sympathetic nerve activity (MSNA; microneurography) and forearm blood flow (Doppler ultrasound) during dynamic forearm exercise (15% of maximal voluntary contraction). α-Adrenergic agonists (phenylephrine and clonidine) and an antagonist (phentolamine) were infused intra-arterially to assess α-adrenergic receptor responsiveness and restraint, respectively. Resting MSNA was ∼35% higher in adults with MetSyn (P exercise. Clonidine-mediated vasoconstriction was greater in adults with MetSyn (P  0.05). Interestingly, exercise-mediated vasodilatation was greater in MetSyn (P exercise blood flow during low-intensity hand-grip exercise when compared with age-matched healthy control subjects. These results suggest that adults with MetSyn exhibit compensatory vascular control mechanisms capable of preserving blood flow responses to exercise in the face of augmented sympathetic adrenergic activity. © 2014 The Authors. Experimental Physiology © 2014 The Physiological Society.

Controls on summer low flow

Science.gov (United States)

Graham, C. B.; McNamara, J. P.

2012-12-01

Summer low flow has significant impacts on aquatic flora and fauna, municipal water use, and power generation. However, the controls on the minimum annual summer discharge are complex, including a combination of snowmelt dynamics, summer evapotranspiration demand, and spring, summer precipitation patterns and surface - groundwater interactions. This is especially true in the Rocky Mountain West of the United States, where snowpack provides the majority of water available for spring runoff and groundwater replenishment. In this study, we look at summer low flow conditions at four snow dominated catchments (26 km2 - 2200 km2) in South-central Idaho currently feeling the effects of climate change. Measures of snowmelt dynamics, summer evapotranspiration demand and spring and summer precipitation are used to determine the dominant controls on late summer low flow magnitude, timing and duration. These analyses show that the controls vary between watersheds, with significant implications for the impacts of climate change in snow dominated areas of the Rocky Mountain West.

Activity flow over resting-state networks shapes cognitive task activations.

Science.gov (United States)

Cole, Michael W; Ito, Takuya; Bassett, Danielle S; Schultz, Douglas H

2016-12-01

Resting-state functional connectivity (FC) has helped reveal the intrinsic network organization of the human brain, yet its relevance to cognitive task activations has been unclear. Uncertainty remains despite evidence that resting-state FC patterns are highly similar to cognitive task activation patterns. Identifying the distributed processes that shape localized cognitive task activations may help reveal why resting-state FC is so strongly related to cognitive task activations. We found that estimating task-evoked activity flow (the spread of activation amplitudes) over resting-state FC networks allowed prediction of cognitive task activations in a large-scale neural network model. Applying this insight to empirical functional MRI data, we found that cognitive task activations can be predicted in held-out brain regions (and held-out individuals) via estimated activity flow over resting-state FC networks. This suggests that task-evoked activity flow over intrinsic networks is a large-scale mechanism explaining the relevance of resting-state FC to cognitive task activations.

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.

Homeland Security and Information Control: A Model of Asymmetric Information Flows.

Science.gov (United States)

Maxwell, Terrence A.

2003-01-01

Summarizes some of the activities the United States government has undertaken to control the dissemination of information since 2001. It also explores, through a conceptual model of information flows, potential impacts and discontinuities between policy purposes and outcomes. (AEF)

Stabilising falling liquid film flows using feedback control

Energy Technology Data Exchange (ETDEWEB)

Thompson, Alice B., E-mail: alice.thompson1@imperial.ac.uk; Gomes, Susana N.; Pavliotis, Grigorios A.; Papageorgiou, Demetrios T. [Department of Mathematics, Imperial College London, London SW7 2AZ (United Kingdom)

2016-01-15

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

Flow Control

Science.gov (United States)

2013-04-08

can be written as â fj (t) =WO tanh( WIx (t)+bI)+bO, (38) where WI , WO are the input and output matrices, respectively, and bI and bO are the input...applications, present on envisioned airborne optical platforms . One of the problems is that all adaptive optical systems rely on mechanically moving some...of successfully controlling the optical aberration due to the flow over the aperture of airborne optical platforms . As outlined above, systems

Active Control of Flow Separation on a High-Lift System with Slotted Flap at High Reynolds Number

Science.gov (United States)

Khodadoust, Abdollah; Washburn, Anthony

2007-01-01

The NASA Energy Efficient Transport (EET) airfoil was tested at NASA Langley's Low- Turbulence Pressure Tunnel (LTPT) to assess the effectiveness of distributed Active Flow Control (AFC) concepts on a high-lift system at flight scale Reynolds numbers for a medium-sized transport. The test results indicate presence of strong Reynolds number effects on the high-lift system with the AFC operational, implying the importance of flight-scale testing for implementation of such systems during design of future flight vehicles with AFC. This paper describes the wind tunnel test results obtained at the LTPT for the EET high-lift system for various AFC concepts examined on this airfoil.

Active combustion flow modulation valve

Science.gov (United States)

Hensel, John Peter; Black, Nathaniel; Thorton, Jimmy Dean; Vipperman, Jeffrey Stuart; Lambeth, David N; Clark, William W

2013-09-24

A flow modulation valve has a slidably translating hollow armature with at least one energizable coil wound around and fixably attached to the hollow armature. The energizable coil or coils are influenced by at least one permanent magnet surrounding the hollow armature and supported by an outer casing. Lorentz forces on the energizable coils which are translated to the hollow armature, increase or decrease the flow area to provide flow throttling action. The extent of hollow armature translation depends on the value of current supplied and the direction of translation depends on the direction of current flow. The compact nature of the flow modulation valve combined with the high forces afforded by the actuator design provide a flow modulation valve which is highly responsive to high-rate input control signals.

Grid-Connection Half-Bridge PV Inverter System for Power Flow Controlling and Active Power Filtering

Directory of Open Access Journals (Sweden)

Chih-Lung Shen

2012-01-01

Full Text Available A half-bridge photovoltaic (PV system is proposed, which can not only deal with bidirectional power flowing but also improve power quality. According to varying insolation, the system conditions real power for dc and ac loads to accommodate different amounts of PV power. Furthermore, the system eliminates current harmonics and improves power factor simultaneously. As compared with conventional PV inverter, the total number of active switches and current sensors can be reduced so that its cost is lower significantly. For current command determination, a linear-approximation method (LAM is applied to avoid the complicated calculation and achieve the maximum power point tracking (MPPT feature. For current controlling, a direct-source-current-shaping (DSCS algorithm is presented to shape the waveform of line current. Simulation results and practical measurements also demonstrate the feasibility of the proposed half-bridge PV system.

Separation flow control on a generic ground vehicle using steady microjet arrays

Energy Technology Data Exchange (ETDEWEB)

Aubrun, Sandrine; Kourta, Azeddine [Universite d' Orleans, Laboratoire PRISME, Orleans cedex (France); McNally, Jonathan; Alvi, Farrukh [Florida State University, FAMU-FSU College of Engineering, Tallahassee, FL (United States)

2011-11-15

A model of a generic vehicle shape, the Ahmed body with a 25 slant, is equipped with an array of blowing steady microjets 6 mm downstream of the separation line between the roof and the slanted rear window. The goal of the present study is to evaluate the effectiveness of this actuation method in reducing the aerodynamic drag, by reducing or suppressing the 3D closed separation bubble located on the slanted surface. The efficiency of this control approach is quantified with the help of aerodynamic load measurements. The changes in the flow field when control is applied are examined using PIV and wall pressure measurements and skin friction visualisations. By activating the steady microjet array, the drag coefficient was reduced by 9-14% and the lift coefficient up to 42%, depending on the Reynolds number. The strong modification of the flow topology under progressive flow control is particularly studied. (orig.)

Manipulation of vortex rings for flow control

International Nuclear Information System (INIS)

Toyoda, Kuniaki; Hiramoto, Riho

2009-01-01

This paper reviews the dynamics of vortex rings and the control of flow by the manipulation of vortex rings. Vortex rings play key roles in many flows; hence, the understanding of the dynamics of vortex rings is crucial for scientists and engineers dealing with flow phenomena. We describe the structures and motions of vortex rings in circular and noncircular jets, which are typical examples of flows evolving into vortex rings. For circular jets the mechanism of evolving, merging and breakdown of vortex rings is described, and for noncircular jets the dynamics of three-dimensional deformation and interaction of noncircular vortex rings under the effect of self- and mutual induction is discussed. The application of vortex-ring manipulation to the control of various flows is reviewed with successful examples, based on the relationship between the vortex ring dynamics and the flow properties. (invited paper)

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...

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.

Plasma-based actuators for turbulent boundary layer control in transonic flow

Science.gov (United States)

Budovsky, A. D.; Polivanov, P. A.; Vishnyakov, O. I.; Sidorenko, A. A.

2017-10-01

The study is devoted to development of methods for active control of flow structure typical for the aircraft wings in transonic flow with turbulent boundary layer. The control strategy accepted in the study was based on using of the effects of plasma discharges interaction with miniature geometrical obstacles of various shapes. The conceptions were studied computationally using 3D RANS, URANS approaches. The results of the computations have shown that energy deposition can significantly change the flow pattern over the obstacles increasing their influence on the flow in boundary layer region. Namely, one of the most interesting and promising data were obtained for actuators basing on combination of vertical wedge with asymmetrical plasma discharge. The wedge considered is aligned with the local streamlines and protruding in the flow by 0.4-0.8 of local boundary layer thickness. The actuator produces negligible distortion of the flow at the absence of energy deposition. Energy deposition along the one side of the wedge results in longitudinal vortex formation in the wake of the actuator providing momentum exchange in the boundary layer. The actuator was manufactured and tested in wind tunnel experiments at Mach number 1.5 using the model of flat plate. The experimental data obtained by PIV proved the availability of the actuator.

Active control of multi-input hydraulic journal bearing system

Science.gov (United States)

Chuang, Jen-Chen; Chen, Chi-Yin; Tu, Jia-Ying

2016-09-01

Because of the advantages of high accuracy, high capacity, and low friction, the development of hydrostatic bearing for machine tool receives significant attention in the last decades. The mechanics and mechanical design of hydrostatic journal bearing with capillary restrictors has been discussed in literature. However, pragmatically, the undesired loading effects of cutting force tend to result in resonance and instability of the rotor and damage the shaft during operation. Therefore, multi-input, active flow control using state feedback design is proposed in this paper. To this purpose, the proportional pressure valves are added to the hydraulic system as active control devices, and the linearised models of the bearing and valve are discussed and identified. Simulation and experimental work is conducted to verify the proposed active control and parameter identification techniques. The results show that the unbalance responses of the rotor are reduced by the proposed state feedback controller, which is able to regulate the flow pressure effectively, thus enhancing the stability and accuracy of the hydraulic journal bearing.

Flow control for oblique shock wave reflections

NARCIS (Netherlands)

Giepman, R.H.M.

2016-01-01

Shock wave-boundary layer interactions are prevalent in many aerospace applications that involve transonic or supersonic flows. Such interactions may lead to boundary layer separation, flow unsteadiness and substantial losses in the total pressure. Flow control techniques can help to mitigate these

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.......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...

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

Science.gov (United States)

Motil, Brian; Santen, Mark A.

1993-01-01

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

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

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

Science.gov (United States)

Mosing, Miriam A; Pedersen, Nancy L; Cesarini, David; Johannesson, Magnus; Magnusson, Patrik K E; Nakamura, Jeanne; Madison, Guy; Ullén, Fredrik

2012-01-01

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 dopaminergic neural

Photothermally controlled Marangoni flow around a micro bubble

International Nuclear Information System (INIS)

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

2015-01-01

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

Photothermally controlled Marangoni flow around a micro bubble

Science.gov (United States)

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

2015-01-01

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.

Control of unsteady separated flow associated with the dynamic pitching of airfoils

Science.gov (United States)

Ahmed, Sajeer

1991-01-01

Although studies have been done to understand the dependence of parameters for the occurrence of deep stall, studies to control the flow for sustaining lift for a longer time has been little. To sustain the lift for a longer time, an understanding of the development of the flow over the airfoil is essential. Studies at high speed are required to study how the flow behavior is dictated by the effects of compressibility. When the airfoil is pitched up in ramp motion or during the upstroke of an oscillatory cycle, the flow development on the upper surface of the airfoil and the formation of the vortex dictates the increase in lift behavior. Vortex shedding past the training edge decreases the lift. It is not clear what is the mechanism associated with the unsteady separation and vortex formation in present unsteady environment. To develop any flow control device, to suppress the vortex formation or delay separation, it is important that this mechanism be properly understood. The research activities directed toward understanding these questions are presented and the results are summarized.

On-Chip Enucleation of Bovine Oocytes using Microrobot-Assisted Flow-Speed Control

Directory of Open Access Journals (Sweden)

Akihiko Ichikawa

2013-06-01

Full Text Available In this study, we developed a microfluidic chip with a magnetically driven microrobot for oocyte enucleation. A microfluidic system was specially designed for enucleation, and the microrobot actively controls the local flow-speed distribution in the microfluidic chip. The microrobot can adjust fluid resistances in a channel and can open or close the channel to control the flow distribution. Analytical modeling was conducted to control the fluid speed distribution using the microrobot, and the model was experimentally validated. The novelties of the developed microfluidic system are as follows: (1 the cutting speed improved significantly owing to the local fluid flow control; (2 the cutting volume of the oocyte can be adjusted so that the oocyte undergoes less damage; and (3 the nucleus can be removed properly using the combination of a microrobot and hydrodynamic forces. Using this device, we achieved a minimally invasive enucleation process. The average enucleation time was 2.5 s and the average removal volume ratio was 20%. The proposed new system has the advantages of better operation speed, greater cutting precision, and potential for repeatable enucleation.

Simulation Results of Closed Loop Controlled Interline Power Flow Controller System

Directory of Open Access Journals (Sweden)

P. USHA RANI

2016-01-01

Full Text Available The Interline Power Flow Controller (IPFC is the latest generation of Flexible AC Transmission Systems (FACTS devices which can be used to control power flows of multiple transmission lines. A dispatch strategy is proposed for an IPFC operating at rated capacity, in which the power circulation between the two series converters is used as the parameter to optimize the voltage profile and power transfer. Voltage stability curves for test system are shown to illustrate the effectiveness of this proposed strategy. In this paper, a circuit model for IPFC is developed and simulation of interline power flow controller is done using the proposed circuit model. Simulation is done using MATLAB simulink and the results are presented.

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....

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).

Active flow control on a NACA 23012 airfoil model by means of magnetohydrodynamic plasma actuator

International Nuclear Information System (INIS)

Kazanskiy, P N; Moralev, I A; Bityurin, V A; Efimov, A V

2016-01-01

The paper is devoted to the study of high speed flow control around the airfoil by means of the Lorentz force. The latter is formed by creating the pulsed arc filament, moving in the magnetic field along the upper airfoil surface. The research was performed for the NACA23012 airfoil model at flow velocities up to 60 m/s (134 mph). The dynamic measurement of the aerodynamic forces on the airfoil was made. Changes up to 5% in an average value of lift and pitching moment were obtained at pulse repetition frequency up to 13 Hz and average discharge power less than 200 W. The amplitude of lift force oscillation was obtained as high as 10%, with the integration time of the balance 30 ms. The dynamic flow visualization of an airfoil model after a single discharge ignition was performed. It is shown that interaction of the main flow with the arc-induced disturbance leads to the dramatic changes in the flow structure. It was shown that the upstream movement of the arc channel (I = 40-700 A) leads to the local flow separation and simultaneously to the formation of a high pressure region above the model surface. Current paper presents investigation of previous work. (paper)

Control of high frequency microactuators using active structures

International Nuclear Information System (INIS)

Kreth, P A; Alvi, F S; Reese, B M; Oates, W S

2015-01-01

A fluidically driven microactuator that generates supersonic, pulsed microjets has been implemented with smart materials to actively and precisely control the frequency of the microjets in a closed-loop manner. Since this actuator relies on a number of microscale flow and acoustic phenomena to produce the pulsed microjets, its resonant frequency is determined by its geometry and other flow parameters. The design discussed in this paper integrates piezoelectric stacks by connecting them to movable sidewalls within the actuator such that the microactuator's internal geometry can be controlled by varying the voltage across the piezo-stacks. An open-loop control scheme demonstrates the frequency modulation capabilities that are enabled with this design: very large frequency deviations (up to ±500 Hz) around the actuator design frequency are attained at very high rates (up to 1 kHz). Closed-loop control of the microactuator's frequency was also demonstrated, and the results indicate that (combined with appropriate sensors) this actuator could be used effectively for active, feedback control in high-speed, resonance-dominated flowfields. This proof of concept study clearly illustrates the ability of this robust and compact actuator to produce perturbations that can be modulated and controlled based on the desired control objective. (paper)

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.

Numerical study of MHD supersonic flow control

Science.gov (United States)

Ryakhovskiy, A. I.; Schmidt, A. A.

2017-11-01

Supersonic MHD flow around a blunted body with a constant external magnetic field has been simulated for a number of geometries as well as a range of the flow parameters. Solvers based on Balbas-Tadmor MHD schemes and HLLC-Roe Godunov-type method have been developed within the OpenFOAM framework. The stability of the solution varies depending on the intensity of magnetic interaction The obtained solutions show the potential of MHD flow control and provide insights into for the development of the flow control system. The analysis of the results proves the applicability of numerical schemes, that are being used in the solvers. A number of ways to improve both the mathematical model of the process and the developed solvers are proposed.

Anthropogenic effect on avalanche and debris flow activity

OpenAIRE

S. A. Sokratov; Yu. G. Seliverstov; A. L. Shnyparkov; K. P. Koltermann

2013-01-01

The paper presents examples of the change in snow avalanches and debris flows activity due to the anthropogenic pressure on vegetation and relief. The changes in dynamical characteristics of selected snow avalanches and debris flows due to the anthropogenic activity are quantified. The conclusion is made that the anthropogenic effects on the snow avalanches and debris flows activity are more pronounced than the possible effects of the climate change. The necessity is expressed on the unavoida...

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 Aquasuitetext">® 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.

Variability of sap flow on forest hillslopes: patterns and controls

Science.gov (United States)

Hassler, Sibylle; Blume, Theresa

2013-04-01

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

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.

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)

Thermally activated plastic flow in the presence of multiple obstacle types

International Nuclear Information System (INIS)

Dong, Y; Curtin, W A

2012-01-01

The rate- and temperature-dependent plastic flow in a material containing two types of thermally activatable obstacles to dislocation motion is studied both numerically and theoretically in a regime of relative obstacle densities for which the zero-temperature stress is additive. The numerical methods consider the low-density ‘forest’ obstacles first as point obstacles and then as extended obstacles having a finite interaction length with the dislocation, while the high-density ‘solute’ obstacles are treated as point obstacles. Results show that the finite-temperature flow stresses due to different obstacle strengthening mechanisms are additive, as proposed by Kocks et al, only when all strengthening obstacles can be approximated as point-like obstacles. When the activation distance of the low-density extended obstacles exceeds the spacing between the high-density obstacles, the finite-temperature flow stress is non-additive and the effective activation energy differs from that of the Kocks et al model. An analytical model for the activation energy versus flow stress is proposed, based on analysis of the simulation results, to account for the effect of the finite interaction length. In this model, for high forest activation energies, the point-pinning solute obstacles provide a temperature-dependent backstress σ b on dislocation and the overall activation energy is otherwise controlled by the forest activation energy. The model predictions agree well with numerical results for a wide range of obstacle properties, clearly showing the effect due to the finite interaction between dislocation and the obstacles. The implications of our results on the activation volume are discussed with respect to experimental results on solute-strengthened fcc alloys. (paper)

Integration of power flow controlling devices and HVDC-systems into the optimal power flow; Integration von leistungsflusssteuernden Komponenten und HGUe-Systemen in die Leistungsflussoptimierung

Energy Technology Data Exchange (ETDEWEB)

Natemeyer, Hendrik; Scheufen, Martin; Roehder, Andreas; Schnettler, Armin [RWTH Aachen Univ. (Germany). Inst. fuer Hochspannungstechnik (IFHT)

2012-07-01

An integration of High Voltage Direct Current Transmission Systems (HVDC) or Flexible AC Transmission Systems (FACTS) into power systems enables the possibility to actively influence and control the corresponding power flows in the electrical network. The systemic benefits are a more efficient utilization of existing transmission capacities and improved controllability in fault situations. This paper introduces methods of a coordinative control of such devices and their representation in stationary power flow calculations including the control in (n-1)-cases. This might be a useful tool for the network operation, especially in face of more frequently occurring fast system changes. Examples of a corresponding implementation and application are provided. (orig.)

Bio-mimetic Flow Control

Science.gov (United States)

Choi, Haecheon

2009-11-01

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

Effects of glycemic control on saliva flow rates and protein composition in non-insulin-dependent diabetes mellitus.

Science.gov (United States)

Dodds, M W; Dodds, A P

1997-04-01

The objective of this study was to determine whether improvements in the level of diabetic control in a group of subjects with poorly controlled non-insulin-dependent diabetes mellitus influence salivary output and composition. Repeated whole unstimulated and stimulated parotid saliva samples were collected from diabetic patients attending an outpatient diabetes education program and a matched nondiabetic control group. Saliva was analyzed for flow rates, parotid protein concentration and composition, and amylase activity. Subjective responses to questions about salivary hypofunction were tested. There were no significant differences in whole unstimulated and stimulated parotid flow rates or stimulated parotid protein concentration and composition between diabetics and the control group. Amylase activity was higher in diabetics and decreased with improved glycemic control. Subjects reporting taste alterations had higher mean blood glucose levels than subjects with normal taste sensation. Poorly controlled non-insulin-dependent diabetes mellitus has no influence on saliva output, although amylase activity may be elevated, and there may be taste alterations.

Objective function choice for control of a thermocapillary flow using an adjoint-based control strategy

International Nuclear Information System (INIS)

Muldoon, Frank H.; Kuhlmann, Hendrik C.

2015-01-01

Highlights: • Suppression of oscillations in a thermocapillary flow is addressed by optimization. • The gradient of the objective function is obtained by solving the adjoint equations. • The issue of choosing an objective function is investigated. - Abstract: The problem of suppressing flow oscillations in a thermocapillary flow is addressed using a gradient-based control strategy. The physical problem addressed is the “open boat” process of crystal growth, the flow in which is driven by thermocapillary and buoyancy effects. The problem is modeled by the two-dimensional unsteady incompressible Navier–Stokes and energy equations under the Boussinesq approximation. The goal of the control is to suppress flow oscillations which arise when the driving forces are such that the flow becomes unsteady. The control is a spatially and temporally varying temperature gradient boundary condition at the free surface. The control which minimizes the flow oscillations is found using a conjugate gradient method, where the gradient of the objective function with respect to the control variables is obtained from solving a set of adjoint equations. The issue of choosing an objective function that can be both optimized in a computationally efficient manner and optimization of which provides control that damps the flow oscillations is investigated. Almost complete suppression of the flow oscillations is obtained for certain choices of the objective function.

Drag Reduction by Laminar Flow Control

Directory of Open Access Journals (Sweden)

Nils Beck

2018-01-01

Full Text Available The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF and Hybrid Laminar Flow Control (HLFC to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today’s turbulent aircraft.

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

Science.gov (United States)

2016-04-15

transport aircraft , much less cruise. The search for a perfect actuator continues, but progress has been limited by the often proprietary nature these...wave generation as a mechanism for high amplitude, high bandwidth actuation has been demonstrated, but the fundamental physics of how this...moving forward with such a definition. 15. SUBJECT TERMS active flow control, energy deposition, plasma actuation 16. SECURITY CLASSIFICATION OF: 17

Active technique by suction to control the flow structure over a van model

Science.gov (United States)

Harinaldi, Budiarso, Warjito, Kosasih, Engkos A.; Tarakka, Rustan; Simanungkalit, Sabar P.

2012-06-01

Today research trend in car aerodynamics are carried out from the point of view of the durable development. Some car companies have the objective to develop control solution that enable to reduce the aerodynamic drag of vehicle. It provides the possibility to modify the flow separation to reduce the development of the swirling structures around the vehicle. In this study, a family van is modeled with a modified form of Ahmed's body by changing the orientation of the flow from its original form (modified/reversed Ahmed Body). This model is equipped with a suction on the rear side to comprehensively examine the pressure field modifications that occur. The investigation combines computational and experimental work. The computational simulation used is k-epsilon flow turbulence model. The reversed Ahmed body used in the investigation has slant angle (φ) 35° at the front part. In the computational work, meshing type is tetra/hybrid element with hex core type and the grid number is more than 1.7 million in order to ensure detail discretization and more accurate calculation results. The boundary condition is upstream velocity of 11.1 m/s. Mean free stream at far upstream region is assumed in a steady state condition and uniform. The suction velocity is set at 1 m/s. Meanwhile in the experimental work a reversed Ahmed model is tested in a controlled wind tunnel experiments. The main measurement is the drag aerodynamic measurement at rear of the body of the model using strain gage. The results show that the application of a suction in the rear part of the van model give the effect of reducing the wake and the vortex is formed. Aerodynamic drag reduction close to 24% for the computational approach and 14.8% for the experimental approach by introducing a suction have been obtained.

Controlling Heat Transport and Flow Structures in Thermal Turbulence Using Ratchet Surfaces

Science.gov (United States)

Jiang, Hechuan; Zhu, Xiaojue; Mathai, Varghese; Verzicco, Roberto; Lohse, Detlef; Sun, Chao

2018-01-01

In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchetlike roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the large scale circulation roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled. The two different orientations of LSCR give two quite different heat transport efficiencies, indicating that heat transport is sensitive to the LSCR direction over the asymmetric roughness structure. Through a quantitative analysis of the dynamics of thermal plume emissions and the orientation of the LSCR over the asymmetric structure, we provide a physical explanation for these findings. The current work has important implications for passive and active flow control in engineering, biofluid dynamics, and geophysical flows.

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.

Control of supersonic axisymmetric base flows using passive splitter plates and pulsed plasma actuators

Science.gov (United States)

Reedy, Todd Mitchell

An experimental investigation evaluating the effects of flow control on the near-wake downstream of a blunt-based axisymmetric body in supersonic flow has been conducted. To better understand and control the physical phenomena that govern these massively separated high-speed flows, this research examined both passive and active flow-control methodologies designed to alter the stability characteristics and structure of the near-wake. The passive control investigation consisted of inserting splitter plates into the recirculation region. The active control technique utilized energy deposition from multiple electric-arc plasma discharges placed around the base. The flow-control authority of both methodologies was evaluated with experimental diagnostics including particle image velocimetry, schlieren photography, surface flow visualization, pressure-sensitive paint, and discrete surface pressure measurements. Using a blowdown-type wind tunnel reconstructed specifically for these studies, baseline axisymmetric experiments without control were conducted for a nominal approach Mach number of 2.5. In addition to traditional base pressure measurements, mean velocity and turbulence quantities were acquired using two-component, planar particle image velocimetry. As a result, substantial insight was gained regarding the time-averaged and instantaneous near-wake flow fields. This dataset will supplement the previous benchmark point-wise laser Doppler velocimetry data of Herrin and Dutton (1994) for comparison with new computational predictive techniques. Next, experiments were conducted to study the effects of passive triangular splitter plates placed in the recirculation region behind a blunt-based axisymmetric body. By dividing the near-wake into 1/2, 1/3, and 1/4 cylindrical regions, the time-averaged base pressure distribution, time-series pressure fluctuations, and presumably the stability characteristics were altered. While the spatial base pressure distribution was

A compact active grid for stirring pipe flow

NARCIS (Netherlands)

Verbeek, A.A.; Pos, R.C.; Stoffels, G.G.M.; Geurts, B.J.; Meer, van der Th.

2013-01-01

A compact active grid is developed with which a pipe flow can be stirred in order to enhance the turbulence. The active grid is composed of a stationary and a rotating disk with characteristic hole patterns. This active grid is placed inside the pipe, allowing flow to pass through it. With only one

A compact active grid for stirring pipe flow

NARCIS (Netherlands)

Verbeek, Antonie Alex; Pos, R.C.; Stoffels, Genie G.M.; Geurts, Bernardus J.; van der Meer, Theodorus H.

A compact active grid is developed with which a pipe flow can be stirred in order to enhance the turbulence. The active grid is composed of a stationary and a rotating disk with characteristic hole patterns. This active grid is placed inside the pipe, allowing flow to pass through it. With only one

Flow Control Enabled Aircraft Design

National Research Council Canada - National Science Library

Nangia, Rajendar

2004-01-01

...: Many future advanced aircraft concepts being considered by the Air Force fall outside the current aerodynamic design practice and will rely heavily on the use of flow control technology to optimize flight performance...

Direct numerical simulation of turbulent channel flow with spanwise alternatively distributed strips control

Science.gov (United States)

Ni, Weidan; Lu, Lipeng; Fang, Jian; Moulinec, Charles; Yao, Yufeng

2018-05-01

The effect of spanwise alternatively distributed strips (SADS) control on turbulent flow in a plane channel has been studied by direct numerical simulations to investigate the characteristics of large-scale streamwise vortices (LSSVs) induced by small-scale active wall actuation, and their potential in suppressing flow separation. SADS control is realized by alternatively arranging out-of-phase control (OPC) and in-phase control (IPC) wall actuations on the lower channel wall surface, in the spanwise direction. It is found that the coherent structures are suppressed or enhanced alternatively by OPC or IPC, respectively, leading to the formation of a vertical shear layer, which is responsible for the LSSVs’ presence. Large-scale low-speed region can also be observed above the OPC strips, which resemble large-scale low-speed streaks. LSSVs are found to be in a statistically-converged steady state and their cores are located between two neighboring OPC and IPC strips. Their motions contribute significantly to the momentum transport in the wall-normal and spanwise directions, demonstrating their potential ability to suppress flow separation.

Suboptimal control for drag reduction in turbulent pipe flow

International Nuclear Information System (INIS)

Choi, Jung Il; Sung, Hyung Jin; Xu, Chun Xiao

2001-01-01

A suboptimal control law in turbulent pipe flow is derived and tested. Two sensing variables ∂ρ/∂θ / w and ∂ν θ /∂r / w are applied with two actuations φ θ and φ γ . To test the suboptimal control law, direct numerical simulations of turbulent pipe flow at Re τ =150 are performed. When the control law is applied, a 13∼23% drag reduction is achieved. The most effective drag reduction is made at the pair of ∂υ θ /∂r / w and φ γ . An impenetrable virtual wall concept is useful for analyzing the near-wall suction and blowing. The virtual wall concept is useful for analyzing the near-wall behavior of the controlled flow. Comparison of the present suboptimal control with that of turbulent channel flow reveals that the curvature effect is insignificant

Bubble gate for in-plane flow control.

Science.gov (United States)

Oskooei, Ali; Abolhasani, Milad; Günther, Axel

2013-07-07

We introduce a miniature gate valve as a readily implementable strategy for actively controlling the flow of liquids on-chip, within a footprint of less than one square millimetre. Bubble gates provide for simple, consistent and scalable control of liquid flow in microchannel networks, are compatible with different bulk microfabrication processes and substrate materials, and require neither electrodes nor moving parts. A bubble gate consists of two microchannel sections: a liquid-filled channel and a gas channel that intercepts the liquid channel to form a T-junction. The open or closed state of a bubble gate is determined by selecting between two distinct gas pressure levels: the lower level corresponds to the "open" state while the higher level corresponds to the "closed" state. During closure, a gas bubble penetrates from the gas channel into the liquid, flanked by a column of equidistantly spaced micropillars on each side, until the flow of liquid is completely obstructed. We fabricated bubble gates using single-layer soft lithographic and bulk silicon micromachining procedures and evaluated their performance with a combination of theory and experimentation. We assessed the dynamic behaviour during more than 300 open-and-close cycles and report the operating pressure envelope for different bubble gate configurations and for the working fluids: de-ionized water, ethanol and a biological buffer. We obtained excellent agreement between the experimentally determined bubble gate operational envelope and a theoretical prediction based on static wetting behaviour. We report case studies that serve to illustrate the utility of bubble gates for liquid sampling in single and multi-layer microfluidic devices. Scalability of our strategy was demonstrated by simultaneously addressing 128 bubble gates.

Fast incorporation of optical flow into active polygons.

Science.gov (United States)

Unal, Gozde; Krim, Hamid; Yezzi, Anthony

2005-06-01

In this paper, we first reconsider, in a different light, the addition of a prediction step to active contour-based visual tracking using an optical flow and clarify the local computation of the latter along the boundaries of continuous active contours with appropriate regularizers. We subsequently detail our contribution of computing an optical flow-based prediction step directly from the parameters of an active polygon, and of exploiting it in object tracking. This is in contrast to an explicitly separate computation of the optical flow and its ad hoc application. It also provides an inherent regularization effect resulting from integrating measurements along polygon edges. As a result, we completely avoid the need of adding ad hoc regularizing terms to the optical flow computations, and the inevitably arbitrary associated weighting parameters. This direct integration of optical flow into the active polygon framework distinguishes this technique from most previous contour-based approaches, where regularization terms are theoretically, as well as practically, essential. The greater robustness and speed due to a reduced number of parameters of this technique are additional and appealing features.

ISS Payload Racks Automated Flow Control Calibration Method

Science.gov (United States)

Simmonds, Boris G.

2003-01-01

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

Active Noise Control Experiments using Sound Energy Flu

Science.gov (United States)

Krause, Uli

2015-03-01

This paper reports on the latest results concerning the active noise control approach using net flow of acoustic energy. The test set-up consists of two loudspeakers simulating the engine noise and two smaller loudspeakers which belong to the active noise system. The system is completed by two acceleration sensors and one microphone per loudspeaker. The microphones are located in the near sound field of the loudspeakers. The control algorithm including the update equation of the feed-forward controller is introduced. Numerical simulations are performed with a comparison to a state of the art method minimising the radiated sound power. The proposed approach is experimentally validated.

Development of a flow controller for long-term sampling of gases and vapors using evacuated canisters.

Science.gov (United States)

Rossner, Alan; Farant, Jean Pierre; Simon, Philippe; Wick, David P

2002-11-15

Anthropogenic activities contribute to the release of a wide variety of volatile organic compounds (VOC) into microenvironments. Developing and implementing new air sampling technologies that allow for the characterization of exposures to VOC can be useful for evaluating environmental and health concerns arising from such occurrences. A novel air sampler based on the use of a capillary flow controller connected to evacuated canisters (300 mL, 1 and 6 L) was designed and tested. The capillary tube, used to control the flow of air, is a variation on a sharp-edge orifice flow controller. It essentially controls the velocity of the fluid (air) as a function of the properties of the fluid, tube diameter and length. A model to predict flow rate in this dynamic system was developed. The mathematical model presented here was developed using the Hagen-Poiseuille equation and the ideal gas law to predict flow into the canisters used to sample for long periods of time. The Hagen-Poiseuille equation shows the relationship between flow rate, pressure gradient, capillary resistance, fluid viscosity, capillary length and diameter. The flow rates evaluated were extremely low, ranging from 0.05 to 1 mL min(-1). The model was compared with experimental results and was shown to overestimate the flow rate. Empirical equations were developed to more accurately predict flow for the 300 mL, 1 and 6 L canisters used for sampling periods ranging from several hours to one month. The theoretical and observed flow rates for different capillary geometries were evaluated. Each capillary flow controller geometry that was tested was found to generate very reproducible results, RSD gas chromatograph. The capillary flow controller was found to exceed the performance of the sorbent samplers in this comparison.

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.

Liquid metal flow control by DC electromagnetic pumps

International Nuclear Information System (INIS)

Borges, Eduardo Madeira; Braz Filho, Francisco Antonio; Guimaraes, Lamartine Nogueira Frutuoso

2006-01-01

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)

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

Directory of Open Access Journals (Sweden)

Christoph Jenke

2017-04-01

Full Text Available 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.

Design and Realization of Intelligent Flow Controller

Directory of Open Access Journals (Sweden)

Jianxiong Ye

2014-09-01

Full Text Available According to accurate flow rate control requirements in large irrigation zone, a fuzzy controller with dead-band is designed on the characteristics analysis and comparison of PID and Fuzzy. The setting values of water flow for gates are determined by real-time water level detection sensors, and the realistic value of discharged water and gate opening are detected out with relative sensors, simulation manifest that the specific control strategy can adjust the gate swiftly in circumstance of huge offset, and regulate the gate slightly in time of small bias, it is realized with Siemens S315 PLC (Programmable Logical Controller and has being working steadily for 2 years, the aim of regulation is performed properly.

Traffic flow impacts of adaptive cruise control deactivation and (Re)activation with cooperative driver behavior

NARCIS (Netherlands)

Klunder, G.; Li, M.; Minderhoud, M.

2009-01-01

In 2006 in the Netherlands, a field operational test was carried out to study the effect of adaptive cruise control (ACC) and lane departure warning on driver behavior and traffic flow in real traffic. To estimate the effect for larger penetration rates, simulations were needed. For a reliable

Control of flow geometry using electromagnetic body forcing

International Nuclear Information System (INIS)

Rossi, L.; Bocquet, S.; Ferrari, S.; Garcia de la Cruz, J.M.; Lardeau, S.

2009-01-01

This paper presents conceptual experiments and simulations aiming at controlling flow geometries. Such flow design is performed by driving electromagnetically a shallow layer of brine, the forcing being generated by a transverse electrical current and different combinations of permanent magnets placed underneath the brine supporting wall. It is shown how different basic flow characteristics can be obtained with a single pair of magnets, by varying the angle with the electrical current. These basic flows are proposed as potential building blocks for advanced and complex flows studies. Three typical flow structures are presented to illustrate these building blocks. The discussion is then extended to multi-scale geometry by using blocks of various sizes. The flow is analysed using complementary experiments and numerical simulations. A good agreement is found between the 3D simulations and the experiments for both velocity and acceleration fields, which allows a higher degree of confidence in designing and modelling such flows. As the control of the flow geometry is important for mixing, in particular at low Reynolds number, we also illustrate the different stirring properties of the electromagnetically forced flows by comparing visualisations of passive scalars. They reveal complementary mixing properties for each of the building blocks.

Two-phase flow measurements using a photochromic dye activation technique

International Nuclear Information System (INIS)

Kawaji, M.

1998-01-01

A novel flow visualization method called photochromic dye activation (PDA) technique has been used to investigate flow structures and mechanisms in various two-phase flow regimes. This non-intrusive flow visualization technique utilizes light activation of a photochromic dye material dissolved in a clear liquid and is a molecular tagging technique, requiring no seed particles. It has been used to yield both quantitative and qualitative flow data in the liquid phase in annular flow, slug flow and stratified-wavy flows. (author)

Development of the Circulation Control Flow Scheme Used in the NTF Semi-Span FAST-MAC Model

Science.gov (United States)

Jones, Gregory S.; Milholen, William E., II; Chan, David T.; Allan, Brian G.; Goodliff, Scott L.; Melton, Latunia P.; Anders, Scott G.; Carter, Melissa B.; Capone, Francis J.

2013-01-01

The application of a circulation control system for high Reynolds numbers was experimentally validated with the Fundamental Aerodynamic Subsonic Transonic Modular Active Control semi-span model in the NASA Langley National Transonic Facility. This model utilized four independent flow paths to modify the lift and thrust performance of a representative advanced transport type of wing. The design of the internal flow paths highlights the challenges associated with high Reynolds number testing in a cryogenic pressurized wind tunnel. Weight flow boundaries for the air delivery system were identified at mildly cryogenic conditions ranging from 0.1 to 10 lbm/sec. Results from the test verified system performance and identified solutions associated with the weight-flow metering system that are linked to internal perforated plates used to achieve flow uniformity at the jet exit.

The Method of Optimization of Hydropower Plant Performance for Use in Group Active Power Controller

Directory of Open Access Journals (Sweden)

Glazyrin G.V.

2017-04-01

Full Text Available The problem of optimization of hydropower plant performance is considered in this paper. A new method of calculation of optimal load-sharing is proposed. The method is based on application of incremental water flow curves representing relationship between the per unit increase of water flow and active power. The optimal load-sharing is obtained by solving the nonlinear equation governing the balance of total active power and the station power set point with the same specific increase of water flow for all turbines. Unlike traditional optimization techniques, the solution of the equation is obtained without taking into account unit safe operating zones. Instead, if calculated active power of a unit violates the permissible power range, load-sharing is recalculated for the remaining generating units. Thus, optimal load-sharing algorithm suitable for digital control systems is developed. The proposed algorithm is implemented in group active power controller in Novosibirsk hydropower plant. An analysis of operation of group active power controller proves that the application of the proposed method allows obtaining optimal load-sharing at each control step with sufficient precision.

Predesigned surface patterns and topological defects control the active matter.

Science.gov (United States)

Turiv, Taras; Peng, Chenhui; Guo, Yubing; Wei, Qi-Huo; Lavrentovich, Oleg

Active matter exhibits remarkable patterns of never-ending dynamics with giant fluctuations of concentration, varying order, nucleating and annihilating topological defects. These patterns can be seen in active systems of both biological and artificial origin. A fundamental question is whether and how one can control this chaotic out-of-equilibrium behavior. We demonstrate a robust control of local concentration, trajectories of active self-propelled units and the net flows of active bacteria Bacillus Substilis by imposing pre-designed surface patterns of orientational order in a water-based lyotropic chromonic liquid crystal. The patterns force the bacteria to gather into dynamic swarms with spatially modulated concentration and well-defined polarity of motion. Topological defects produce net motion of bacteria with a unidirectional circulation, while pairs of defects induce a pumping action. The qualitative features of the dynamics can be explained by interplay of curvature and activity, in particular, by ability of mixed splay-bend curvatures to generate threshold-less active flows. The demonstrated level of control opens opportunities in engineering materials and devices that mimic rich functionality of living systems. This work was supported by NSF Grants DMR-1507637, DMS-1434185, CMMI-1436565, by the Petroleum Research Grant PRF# 56046-ND7 administered by the American Chemical Society.

Plasma actuators for bluff body flow control

Science.gov (United States)

Kozlov, Alexey V.

The aerodynamic plasma actuators have shown to be efficient flow control devices in various applications. In this study the results of flow control experiments utilizing single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in cross-flow are reported. This work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re D = 20,000...164,000. Circular cylinders in cross-flow are chosen for study since they represent a generic flow geometry that is similar in all essential aspects to a landing gear oleo or strut. The minimization of the unsteady flow separation from the models and associated large-scale wake vorticity by using actuators reduces the radiated aerodynamic noise. Using either steady or unsteady actuation at ReD = 25,000, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly and near-field sound pressure levels are reduced by 13.3 dB. Unsteady actuation at an excitation frequency of St D = 1 is found to be most effective. The unsteady actuation also has the advantage that total suppression of shedding is achieved for a duty cycle of only 25%. However, since unsteady actuation is associated with an unsteady body force and produces a tone at the actuation frequency, steady actuation is more suitable for noise control applications. Two actuation strategies are used at ReD = 82,000: spanwise and streamwise oriented actuators. Near field microphone measurements in an anechoic wind tunnel and detailed study of the near wake using LDA are presented in the study. Both spanwise and streamwise actuators give nearly the same noise reduction level of 11.2 dB and 14.2 dB, respectively, and similar changes in the wake velocity profiles. The contribution of the actuator induced noise is found to be small compared to the natural shedding

Separation Dynamics of Controlled Internal Flow in an Adverse Pressure Gradient

Science.gov (United States)

Peterson, C. J.; Vukasinovic, B.; Glezer, A.

2017-11-01

The effects of fluidic actuation on the dynamic evolution of aggressive internal flow separation is investigated at speeds up to M = 0.4 within a constant-width diffuser branching off of a primary flow duct. It is shown that a spanwise array of fluidic actuators upstream of the separation actively controls the flow constriction (and losses) within the diffuser and consequently the local pressure gradient at its entrance. The effectiveness of the actuation, as may be measured by the increased flow rate that is diverted through the diffuser, scales with its flow rate coefficient. In the presence of actuation (0.7% mass fraction), the mass flow rate in the primary duct increases by 10% while the fraction of the diverted mass flow rate in the diffuser increases by more than 45%. The flow dynamics near separation in the absence and presence of actuation are characterized using high speed particle image velocimetry and analyzed using proper orthogonal and spectral decompositions. In particular, the spectral contents of the incipient boundary layer separation are compared in the absence and presence of actuation with emphasis on the changes in local dynamics near separation as the characteristic cross stream scale of the boundary layer increases with separation delay.

Cerebral blood flow response to functional activation

DEFF Research Database (Denmark)

Paulson, Olaf B; Hasselbalch, Steen G; Rostrup, Egill

2010-01-01

Cerebral blood flow (CBF) and cerebral metabolic rate are normally coupled, that is an increase in metabolic demand will lead to an increase in flow. However, during functional activation, CBF and glucose metabolism remain coupled as they increase in proportion, whereas oxygen metabolism only inc...... the cerebral tissue's increased demand for glucose supply during neural activation with recent evidence supporting a key function for astrocytes in rCBF regulation....

The synthesis of active pharmaceutical ingredients (APIs using continuous flow chemistry

Directory of Open Access Journals (Sweden)

Marcus Baumann

2015-07-01

Full Text Available The implementation of continuous flow processing as a key enabling technology has transformed the way we conduct chemistry and has expanded our synthetic capabilities. As a result many new preparative routes have been designed towards commercially relevant drug compounds achieving more efficient and reproducible manufacture. This review article aims to illustrate the holistic systems approach and diverse applications of flow chemistry to the preparation of pharmaceutically active molecules, demonstrating the value of this strategy towards every aspect ranging from synthesis, in-line analysis and purification to final formulation and tableting. Although this review will primarily concentrate on large scale continuous processing, additional selected syntheses using micro or meso-scaled flow reactors will be exemplified for key transformations and process control. It is hoped that the reader will gain an appreciation of the innovative technology and transformational nature that flow chemistry can leverage to an overall process.

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry.

Science.gov (United States)

Baumann, Marcus; Baxendale, Ian R

2015-01-01

The implementation of continuous flow processing as a key enabling technology has transformed the way we conduct chemistry and has expanded our synthetic capabilities. As a result many new preparative routes have been designed towards commercially relevant drug compounds achieving more efficient and reproducible manufacture. This review article aims to illustrate the holistic systems approach and diverse applications of flow chemistry to the preparation of pharmaceutically active molecules, demonstrating the value of this strategy towards every aspect ranging from synthesis, in-line analysis and purification to final formulation and tableting. Although this review will primarily concentrate on large scale continuous processing, additional selected syntheses using micro or meso-scaled flow reactors will be exemplified for key transformations and process control. It is hoped that the reader will gain an appreciation of the innovative technology and transformational nature that flow chemistry can leverage to an overall process.

Arduino control of a pulsatile flow rig.

Science.gov (United States)

Drost, S; de Kruif, B J; Newport, D

2018-01-01

This note describes the design and testing of a programmable pulsatile flow pump using an Arduino micro-controller. The goal of this work is to build a compact and affordable system that can relatively easily be programmed to generate physiological waveforms. The system described here was designed to be used in an in-vitro set-up for vascular access hemodynamics research, and hence incorporates a gear pump that delivers a mean flow of 900 ml/min in a test flow loop, and a peak flow of 1106 ml/min. After a number of simple identification experiments to assess the dynamic behaviour of the system, a feed-forward control routine was implemented. The resulting system was shown to be able to produce the targeted representative waveform with less than 3.6% error. Finally, we outline how to further increase the accuracy of the system, and how to adapt it to specific user needs. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

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

Anthropogenic effect on avalanche and debris flow activity

Directory of Open Access Journals (Sweden)

S. A. Sokratov

2013-01-01

Full Text Available The paper presents examples of the change in snow avalanches and debris flows activity due to the anthropogenic pressure on vegetation and relief. The changes in dynamical characteristics of selected snow avalanches and debris flows due to the anthropogenic activity are quantified. The conclusion is made that the anthropogenic effects on the snow avalanches and debris flows activity are more pronounced than the possible effects of the climate change. The necessity is expressed on the unavoidable changes of the natural environment as the result of a construction and of use of the constructed infrastructure to be account for in corresponding planning of the protection measures.

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

International Nuclear Information System (INIS)

Gilmore, Mark Allen

2017-01-01

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.

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.

Synthetic perspective optical flow: Influence on pilot control tasks

Science.gov (United States)

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

1989-01-01

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

Predicting flow at work: investigating the activities and job characteristics that predict flow states at work.

Science.gov (United States)

Nielsen, Karina; Cleal, Bryan

2010-04-01

Flow (a state of consciousness where people become totally immersed in an activity and enjoy it intensely) has been identified as a desirable state with positive effects for employee well-being and innovation at work. Flow has been studied using both questionnaires and Experience Sampling Method (ESM). In this study, we used a newly developed 9-item flow scale in an ESM study combined with a questionnaire to examine the predictors of flow at two levels: the activities (brainstorming, planning, problem solving and evaluation) associated with transient flow states and the more stable job characteristics (role clarity, influence and cognitive demands). Participants were 58 line managers from two companies in Denmark; a private accountancy firm and a public elder care organization. We found that line managers in elder care experienced flow more often than accountancy line managers, and activities such as planning, problem solving, and evaluation predicted transient flow states. The more stable job characteristics included in this study were not, however, found to predict flow at work. Copyright 2010 APA, all rights reserved.

Flow-Control Unit For Nitrogen And Hydrogen Gases

Science.gov (United States)

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

1990-01-01

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

End-tidal control vs. manually controlled minimal-flow anesthesia: a prospective comparative trial.

Science.gov (United States)

Wetz, A J; Mueller, M M; Walliser, K; Foest, C; Wand, S; Brandes, I F; Waeschle, R M; Bauer, M

2017-11-01

To ensure safe general anesthesia, manually controlled anesthesia requires constant monitoring and numerous manual adjustments of the gas dosage, especially for low- and minimal-flow anesthesia. Oxygen flow-rate and administration of volatile anesthetics can also be controlled automatically by anesthesia machines using the end-tidal control technique, which ensures constant end-tidal concentrations of oxygen and anesthetic gas via feedback and continuous adjustment mechanisms. We investigated the hypothesis that end-tidal control is superior to manually controlled minimal-flow anesthesia (0.5 l/min). In this prospective trial, we included 64 patients undergoing elective surgery under general anesthesia. We analyzed the precision of maintenance of the sevoflurane concentration (1.2-1.4%) and expiratory oxygen (35-40%) and the number of necessary adjustments. Target-concentrations of sevoflurane and oxygen were maintained at more stable levels with the use of end-tidal control (during the first 15 min 28% vs. 51% and from 15 to 60 min 1% vs. 19% deviation from sevoflurane target, P tidal oxygen (5, IQR 3-6). The target-concentrations were reached earlier with the use of end-tidal compared with manual controlled minimal-flow anesthesia but required slightly greater use of anesthetic agents (6.9 vs. 6.0 ml/h). End-tidal control is a superior technique for setting and maintaining oxygen and anesthetic gas concentrations in a stable and rapid manner compared with manual control. Consequently, end-tidal control can effectively support the anesthetist. © 2017 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Provably correct control flow graphs from Java bytecode programs with exceptions

NARCIS (Netherlands)

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

2016-01-01

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

Bypass flow rate control method

International Nuclear Information System (INIS)

Kiyama, Yoichi.

1997-01-01

In a PWR type reactor, bypass flow rate is controlled by exchanging existent jetting hole plugs of a plurality of nozzles disposed to the upper end of incore structures in order to flow a portion of primary coolants as a bypass flow to the upper portion of the pressure vessel. Two kinds of exchange plugs, namely, a first plug and a second plug each having a jetting out hole of different diameter are used as exchange plugs. The first plug has the diameter as that of an existent plug and the second plug has a jetting out hole having larger diameter than that of the existent plug. Remained extent plugs are exchanged to a combination of the first and the second plugs without exchanging existent plugs having seizing with the nozzles, in which the number and the diameter of the jetting out holes of the second plugs are previously determined based on predetermined total bypass flow rate to be jetted from the entire plugs after exchange of plugs. (N.H.)

Flow and Noise Control: Review and Assessment of Future Directions

Science.gov (United States)

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

2002-01-01

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

Phase Resolved Angular Velocity Control of Cross Flow Turbines

Science.gov (United States)

Strom, Benjamin; Brunton, Steven; Polagye, Brian

2015-11-01

Cross flow turbines have a number of operational advantages for the conversion of kinetic energy in marine or fluvial currents, but they are often less efficient than axial flow devices. Here a control scheme is presented in which the angular velocity of a cross flow turbine with two straight blades is prescribed as a function of azimuthal blade position, altering the time-varying effective angle of attack. Flume experiments conducted with a scale model turbine show approximately an 80% increase in turbine efficiency versus optimal constant angular velocity and constant resistive torque control schemes. Torque, drag, and lateral forces on one- and two-bladed turbines are analyzed and interpreted with bubble flow visualization to develop a simple model that describes the hydrodynamics responsible for the observed increase in mean efficiency. Challenges associated with implementing this control scheme on commercial-scale devices are discussed. If solutions are found, the performance increase presented here may impact the future development of cross flow turbines.

Examples of detection of water flow by oxygen activation on pulsed neutron logs

International Nuclear Information System (INIS)

de Rosset, W.H.M.

1986-01-01

Upward flow of water in cased wellbores may be detected with pulsed neutron capture (PNC) and gamma ray (GR) tools. Water entering tubing, casing and flowing behind pipe may similarly be evaluated qualitatively. Gamma ray background anomalies in PNC data and elevation of GR tool response occur when water is flowing above threshold velocities and volumes. The technique requires logging the well under static and flow conditions or logging at different tools speeds in a flowing well. Oxygen activation results in increased gamma ray count rates at each detector. PNC far detector and GR well log curves from each log run (flowing well, static well) are overlain. The increases for each curve are offset from the point of water entry by a distance similar to tool source-detector spacing. These offsets in gamma increase are 15-20 ft. higher for the GR than for the PNC far detector and distinguish oxygen activation due to flowing water from common hot spots. The amount of gamma ray increase is controlled by the velocity of upward flow of water past the tool, the amount of water flowing, and the distance of the flow from the tool. Prior planning is important to gain usable information in flowing wells. The upward relative velocity imposes maximal and minimal tool speeds to produce significant gamma increases, and tool speed must be adjusted to optimize gamma changes. Use of the technique to answer actual production problems is illustrated with examples. Insight was gained which led to the correction of the problem in each case

Bluff Body Flow Control Using Dielectric Barrier Discharge Plasma Actuators

Science.gov (United States)

Thomas, Flint; Kozlov, Alexey

2008-11-01

The results of an experimental investigation involving the use of dielectric barrier discharge plasma actuators to control bluff body flow is presented. The motivation for the work is plasma landing gear noise control for commercial transport aircraft. For these flow control experiments, the cylinder in cross-flow is chosen for study since it represents a generic flow geometry that is similar in all essential aspects to a landing gear strut. The current work is aimed both at extending the plasma flow control concept to Reynolds numbers typical of landing approach and take-off and on the development of optimum plasma actuation strategies. The cylinder wake flow with and without actuation are documented in detail using particle image velocimetry (PIV) and constant temperature hot-wire anemometry. The experiments are performed over a Reynolds number range extending to ReD=10^5. Using either steady or unsteady plasma actuation, it is demonstrated that even at the highest Reynolds number Karman shedding is totally eliminated and turbulence levels in the wake decrease by more than 50%. By minimizing the unsteady flow separation from the cylinder and associated large-scale wake vorticity, the radiated aerodynamic noise is also reduced.

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.

Thaw flow control for liquid heat transport systems

Science.gov (United States)

Kirpich, Aaron S.

1989-01-01

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

Identifying the best locations to install flow control devices in sewer networks to enable in-sewer storage

Science.gov (United States)

Leitão, J. P.; Carbajal, J. P.; Rieckermann, J.; Simões, N. E.; Sá Marques, A.; de Sousa, L. M.

2018-01-01

The activation of available in-sewer storage volume has been suggested as a low-cost flood and combined sewer overflow mitigation measure. However, it is currently unknown what the attributes for suitable objective functions to identify the best location for flow control devices are and the impact of those attributes on the results. In this study, we present a novel location model and efficient algorithm to identify the best location(s) to install flow limiters. The model is a screening tool that does not require hydraulic simulations but rather considers steady state instead of simplistic static flow conditions. It also maximises in-sewer storage according to different reward functions that also considers the potential impact of flow control device failure. We demonstrate its usefulness on two real sewer networks, for which an in-sewer storage potential of approximately 2,000 m3 and 500 m3 was estimated with five flow control devices installed.

An Experimental Study on Active Flow Control Using Synthetic Jet Actuators over S809 Airfoil

International Nuclear Information System (INIS)

Gul, M; Uzol, O; Akmandor, I S

2014-01-01

This study investigates the effect of periodic excitation from individually controlled synthetic jet actuators on the dynamics of the flow within the separation and re-attachment regions of the boundary layer over the suction surface of a 2D model wing that has S809 airfoil profile. Experiments are performed in METUWIND's C3 open-loop suction type wind tunnel that has a 1 m × 1 m cross-section test section. The synthetic jet array on the wing consists of three individually controlled actuators driven by piezoelectric diaphragms located at 28% chord location near the mid-span of the wing. In the first part of the study, surface pressure, Constant Temperature Anemometry (CTA) and Particle Image Velocimetry (PIV) measurements are performed over the suction surface of the airfoil to determine the size and characteristics of the separated shear layer and the re-attachment region, i.e. the laminar separation bubble, at 2.3x10 5 Reynolds number at zero angle of attack and with no flow control as a baseline case. For the controlled case, CTA measurements are carried out under the same inlet conditions at various streamwise locations along the suction surface of the airfoil to investigate the effect of the synthetic jet on the boundary layer properties. During the controlled case experiments, the synthetic jet actuators are driven with a sinusoidal frequency of 1.45 kHz and 300Vp-p. Results of this study show that periodic excitation from the synthetic jet actuators eliminates the laminar separation bubble formed over the suction surface of the airfoil at 2.3x10 5 Reynolds number at zero angle of attack

The effects of surface topography control using liquid crystal elastomers on bodies in flow

Science.gov (United States)

Settle, Michael; Guin, Tyler; Beblo, Richard; White, Timothy; Reich, Gregory

2018-03-01

Surface topography control has use across many applications including delayed separation of flow via selective boundary-layer tripping. Recently, advances with liquid crystal elastomers (LCE) have been leveraged for controlled, repeatable, out-of-plane deformations that could enable these topographical changes. An aligned LCE deforms when heated, associated with a loss in order. Circumferential patterns fabricated through the thickness of the LCE film yield a predictable conical out-of-plane deformation that can control surface topography. This study focuses on the experimental investigation of LCE behavior for flow control. Initially, the deformations of LCE samples 1/2" in diameter and 50 µm thick were characterized using Digital Image Correlation under uniform positive and negative gauge pressures at various temperatures. Surface topography showed strong dependence on boundary conditions, sample dimensions, and pattern location relative to the applied boundary conditions, informing adjustment of the LCE of the chemistry to produce higher modulus and glassy materials. As an initial demonstration of the ability to control flow, Then, to demonstrate the potential for flow control, 3D printed cylinders with varying arrangements of representative topographical features were characterized in a wind tunnel with Particle Image Velocimetry. Results showed that features with a maximum deflection height of 1.5 mm in a two-row arrangement can form an asymmetric wake about a 73 mm diameter cylinder that reduces drag while generating lift. These results inform subsequent investigation of active LCE elements on a cylinder that are currently under examination.

Eppur Si Muove: The dynamic nature of physiological control of renal blood flow by the renal sympathetic nerves.

Science.gov (United States)

Schiller, Alicia M; Pellegrino, Peter Ricci; Zucker, Irving H

2017-05-01

Tubuloglomerular feedback and the myogenic response are widely appreciated as important regulators of renal blood flow, but the role of the sympathetic nervous system in physiological renal blood flow control remains controversial. Where classic studies using static measures of renal blood flow failed, dynamic approaches have succeeded in demonstrating sympathetic control of renal blood flow under normal physiological conditions. This review focuses on transfer function analysis of renal pressure-flow, which leverages the physical relationship between blood pressure and flow to assess the underlying vascular control mechanisms. Studies using this approach indicate that the renal nerves are important in the rapid regulation of the renal vasculature. Animals with intact renal innervation show a sympathetic signature in the frequency range associated with sympathetic vasomotion that is eliminated by renal denervation. In conscious rabbits, this sympathetic signature exerts vasoconstrictive, baroreflex control of renal vascular conductance, matching well with the rhythmic, baroreflex-influenced control of renal sympathetic nerve activity and complementing findings from other studies employing dynamic approaches to study renal sympathetic vascular control. In this light, classic studies reporting that nerve stimulation and renal denervation do not affect static measures of renal blood flow provide evidence for the strength of renal autoregulation rather than evidence against physiological renal sympathetic control of renal blood flow. Thus, alongside tubuloglomerular feedback and the myogenic response, renal sympathetic outflow should be considered an important physiological regulator of renal blood flow. Clinically, renal sympathetic vasomotion may be important for solving the problems facing the field of therapeutic renal denervation. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydrodynamic Capture and Release of Passively Driven Particles by Active Particles Under Hele-Shaw Flows

Science.gov (United States)

Mishler, Grant; Tsang, Alan Cheng Hou; Pak, On Shun

2018-03-01

The transport of active and passive particles plays central roles in diverse biological phenomena and engineering applications. In this paper, we present a theoretical investigation of a system consisting of an active particle and a passive particle in a confined micro-fluidic flow. The introduction of an external flow is found to induce the capture of the passive particle by the active particle via long-range hydrodynamic interactions among the particles. This hydrodynamic capture mechanism relies on an attracting stable equilibrium configuration formed by the particles, which occurs when the external flow intensity exceeds a certain threshold. We evaluate this threshold by studying the stability of the equilibrium configurations analytically and numerically. Furthermore, we study the dynamics of typical capture and non-capture events and characterize the basins of attraction of the equilibrium configurations. Our findings reveal a critical dependence of the hydrodynamic capture mechanism on the external flow intensity. Through adjusting the external flow intensity across the stability threshold, we demonstrate that the active particle can capture and release the passive particle in a controllable manner. Such a capture-and-release mechanism is desirable for biomedical applications such as the capture and release of therapeutic payloads by synthetic micro-swimmers in targeted drug delivery.

Flow stabilization with active hydrodynamic cloaks.

Science.gov (United States)

Urzhumov, Yaroslav A; Smith, David R

2012-11-01

We demonstrate that fluid flow cloaking solutions, based on active hydrodynamic metamaterials, exist for two-dimensional flows past a cylinder in a wide range of Reynolds numbers (Re's), up to approximately 200. Within the framework of the classical Brinkman equation for homogenized porous flow, we demonstrate using two different methods that such cloaked flows can be dynamically stable for Re's in the range of 5-119. The first highly efficient method is based on a linearization of the Brinkman-Navier-Stokes equation and finding the eigenfrequencies of the least stable eigenperturbations; the second method is a direct numerical integration in the time domain. We show that, by suppressing the von Kármán vortex street in the weakly turbulent wake, porous flow cloaks can raise the critical Reynolds number up to about 120 or five times greater than for a bare uncloaked cylinder.

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.

Flow control at low Reynolds numbers using periodic airfoil morphing

Science.gov (United States)

Jones, Gareth; Santer, Matthew; Papadakis, George; Bouremel, Yann; Debiasi, Marco; Imperial-NUS Joint PhD Collaboration

2014-11-01

The performance of airfoils operating at low Reynolds numbers is known to suffer from flow separation even at low angles of attack as a result of their boundary layers remaining laminar. The lack of mixing---a characteristic of turbulent boundary layers---leaves laminar boundary layers with insufficient energy to overcome the adverse pressure gradient that occurs in the pressure recovery region. This study looks at periodic surface morphing as an active flow control technique for airfoils in such a flight regime. It was discovered that at sufficiently high frequencies an oscillating surface is capable of not only reducing the size of the separated region---and consequently significantly reducing drag whilst simultaneously increasing lift---but it is also capable of delaying stall and as a result increasing CLmax. Furthermore, by bonding Macro Fiber Composite actuators (MFCs) to the underside of an airfoil skin and driving them with a sinusoidal frequency, it is shown that this control technique can be practically implemented in a lightweight, energy efficient way. Imperial-NUS Joint Ph.D. Programme.

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.

Forced-flow bioreactor for sucrose inversion using ceramic membrane activated by silanization.

Science.gov (United States)

Nakajima, M; Watanabe, A; Jimbo, N; Nishizawa, K; Nakao, S

1989-02-20

A forced-flow enzyme membrane reactor system for sucrose inversion was investigated using three ceramic membranes having different pore sizes. Invertase was immobilized chemically to the inner surface of a ceramic membrane activated by a silane-glutaraldehyde technique. With the cross-flow filtration of sucrose solution, the reaction rate was a function of the permeate flux, easily controlled by pressure. Using 0.5 microm support pore size of membrane, the volumetric productivity obtained was 10 times higher than that in a reported immobilized enzyme column reactor, with a short residence time of 5 s and 100% conversion of the sucrose inversion.

Irreducible Representations of Oscillatory and Swirling Flows in Active Soft Matter

Science.gov (United States)

Ghose, Somdeb; Adhikari, R.

2014-03-01

Recent experiments imaging fluid flow around swimming microorganisms have revealed complex time-dependent velocity fields that differ qualitatively from the stresslet flow commonly employed in theoretical descriptions of active matter. Here we obtain the most general flow around a finite sized active particle by expanding the surface stress in irreducible Cartesian tensors. This expansion, whose first term is the stresslet, must include, respectively, third-rank polar and axial tensors to minimally capture crucial features of the active oscillatory flow around translating Chlamydomonas and the active swirling flow around rotating Volvox. The representation provides explicit expressions for the irreducible symmetric, antisymmetric, and isotropic parts of the continuum active stress. Antisymmetric active stresses do not conserve orbital angular momentum and our work thus shows that spin angular momentum is necessary to restore angular momentum conservation in continuum hydrodynamic descriptions of active soft matter.

A work process and information flow description of control room operations

International Nuclear Information System (INIS)

Davey, E.; Matthews, G.

2007-01-01

The control room workplace is the location from which all plant operations are supervised and controlled on a shift-to-shift basis. The activities comprising plant operations are structured into a number of work processes, and information is the common currency that is used to convey work requirements, communicate business and operating decisions, specify work practice, and describe the ongoing plant and work status. This paper describes the motivation for and early experience with developing a work process and information flow model of CANDU control room operations, and discusses some of the insights developed from model examination that suggest ways in which changes in control centre work specification, organization of resources, or asset layout could be undertaken to achieve operational improvements. (author)

A note on supersonic flow control with nanosecond plasma actuator

Science.gov (United States)

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

2018-04-01

A concept study on supersonic flow control using nanosecond pulsed plasma actuator is conducted by means of numerical simulation. The nanosecond plasma discharge is characterized by the generation of a micro-shock wave in ambient air and a residual heat in the discharge volume arising from the rapid heating of near-surface gas by the quick discharge. The residual heat has been found to be essential for the flow separation control over aerodynamic bodies like airfoil and backward-facing step. In this study, novel experiment is designed to utilize the other flow feature from discharge, i.e., instant shock wave, to control supersonic flow through shock-shock interaction. Both bow shock in front of a blunt body and attached shock anchored at the tip of supersonic projectile are manipulated via the discharged-induced shock wave in an appropriate manner. It is observed that drag on the blunt body is reduced appreciably. Meanwhile, a lateral force on sharp-edged projectile is produced, which can steer the body and give it an effective angle of attack. This opens a promising possibility for extending the applicability of this flow control technique in supersonic flow regime.

GABAA Receptor-Mediated Bidirectional Control of Synaptic Activity, Intracellular Ca2+, Cerebral Blood Flow, and Oxygen Consumption in Mouse Somatosensory Cortex In Vivo

DEFF Research Database (Denmark)

Jessen, Sanne Barsballe; Brazhe, Alexey; Lind, Barbara Lykke

2015-01-01

Neural activity regulates local increases in cerebral blood flow (ΔCBF) and the cortical metabolic rate of oxygen (ΔCMRO2) that constitutes the basis of BOLD functional neuroimaging signals. Glutamate signaling plays a key role in brain vascular and metabolic control; however, the modulatory effect...... of GABA is incompletely understood. Here we performed in vivo studies in mice to investigate how THIP (which tonically activates extrasynaptic GABAARs) and Zolpidem (a positive allosteric modulator of synaptic GABAARs) impact stimulation-induced ΔCBF, ΔCMRO2, local field potentials (LFPs), and fluorescent...... cytosolic Ca2+ transients in neurons and astrocytes. Low concentrations of THIP increased ΔCBF and ΔCMRO2 at low stimulation frequencies. These responses were coupled to increased synaptic activity as indicated by LFP responses, and to Ca2+ activities in neurons and astrocytes. Intermediate and high...

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.

Flow control of micro-ramps on supersonic forward-facing step flow

International Nuclear Information System (INIS)

Zhang Qing-Hu; Zhu Tao; Wu Anping; Yi Shihe

2016-01-01

The effects of the micro-ramps on supersonic turbulent flow over a forward-facing step (FFS) was experimentally investigated in a supersonic low-noise wind tunnel at Mach number 3 using nano-tracer planar laser scattering (NPLS) and particle image velocimetry (PIV) techniques. High spatiotemporal resolution images and velocity fields of supersonic flow over the testing model were captured. The fine structures and their spatial evolutionary characteristics without and with the micro-ramps were revealed and compared. The large-scale structures generated by the micro-ramps can survive the downstream FFS flowfield. The micro-ramps control on the flow separation and the separation shock unsteadiness was investigated by PIV results. With the micro-ramps, the reduction in the range of the reversal flow zone in streamwise direction is 50% and the turbulence intensity is also reduced. Moreover, the reduction in the average separated region and in separation shock unsteadiness are 47% and 26%, respectively. The results indicate that the micro-ramps are effective in reducing the flow separation and the separation shock unsteadiness. (paper)

Exhaust bypass flow control for exhaust heat recovery

Science.gov (United States)

Reynolds, Michael G.

2015-09-22

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

Control of District Heating System with Flow-dependent Delays

DEFF Research Database (Denmark)

Bendtsen, Jan Dimon; Ledesma, Jorge Val; Kallesøe, Carsten Skovmose

2017-01-01

All flow systems are subject to transport delays, which are governed by the flow rates in the system. When the flow rates themselves are control inputs, the system becomes subject to input-dependent state delays, which poses significant theoretical problems. In an earlier paper, we proposed...

Active surge control for variable speed axial compressors.

Science.gov (United States)

Lin, Shu; Yang, Chunjie; Wu, Ping; Song, Zhihuan

2014-09-01

This paper discusses active surge control in variable speed axial compressors. A compression system equipped with a variable area throttle is investigated. Based on a given compressor model, a fuzzy logic controller is designed for surge control and a proportional speed controller is used for speed control. The fuzzy controller uses measurements of the change of pressure rise as well as the change of mass flow to determine the throttle opening. The presented approach does not require the knowledge of system equilibrium or the surge line. Numerical simulations show promising results. The proposed fuzzy logic controller performs better than a backstepping controller and is capable to suppress surge at different operating points. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Application of Shark Skin Flow Control Techniques to Airflow

Science.gov (United States)

Morris, Jackson Alexander

Due to millions of years of evolution, sharks have evolved to become quick and efficient ocean apex predators. Shark skin is made up of millions of microscopic scales, or denticles, that are approximately 0.2 mm in size. Scales located on the shark's body where separation control is paramount (such as behind the gills or the trailing edge of the pectoral fin) are capable of bristling. These scales are hypothesized to act as a flow control mechanism capable of being passively actuated by reversed flow. It is believed that shark scales are strategically sized to interact with the lower 5% of a boundary layer, where reversed flow occurs at the onset of boundary layer separation. Previous research has shown shark skin to be capable of controlling separation in water. This thesis aims to investigate the same passive flow control techniques in air. To investigate this phenomenon, several sets of microflaps were designed and manufactured with a 3D printer. The microflaps were designed in both 2D (rectangular) and 3D (mirroring shark scale geometry) variants. These microflaps were placed in a low-speed wind tunnel in the lower 5% of the boundary layer. Solid fences and a flat plate diffuser with suction were placed in the tunnel to create different separated flow regions. A hot film probe was used to measure velocity magnitude in the streamwise plane of the separated regions. The results showed that low-speed airflow is capable of bristling objects in the boundary layer. When placed in a region of reverse flow, the microflaps were passively actuated. Microflaps fluctuated between bristled and flat states in reverse flow regions located close to the reattachment zone.

Flow-controlled magnetic particle manipulation

Science.gov (United States)

Grate, Jay W [West Richland, WA; Bruckner-Lea, Cynthia J [Richland, WA; Holman, David A [Las Vegas, NV

2011-02-22

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

X-29 vortex flow control tests

Science.gov (United States)

Hancock, Regis; Fullerton, Gordon

1992-01-01

A joint Air Force/NASA X-29 aircraft program to improve yaw control at high angle of attack using vortex flow control (VFC) is described. Directional VFC blowing proved to a be a powerful yaw moment generator and was very effective in overriding natural asymmetries, but was essentially ineffective in suppressing wing rock. Symmetric aft blowing also had little effect on suppressing wing rock.

Forecasting of cash flow from an enterprise’s principal activities

OpenAIRE

Kanapickienė, Rasa; Šlekienė, Vaida

2008-01-01

The article deals with the forecasting of a cash flow from primary activities of an enterprise. Different mathematical methods are applied to forecast cash flow. Cash flow forecasts are often introduced in the project of the enterprise budget. Some scientific sources state that it is possible to forecast cash flow from primary activities of an enterprise according to its historical financial data by the means of regression analysis. These sources suggest various models of regression analysis ...

Modelling and control of systems with flow

NARCIS (Netherlands)

van Mourik, S.

2008-01-01

In practice, feedback control design consists of three steps: modelling, model reduction and controller design for the reduced model. Systems with flow are often complicated, and there is yet no standard algorithm that integrates these steps. In this thesis we make a modest effort by considering two

Control of a Quadcopter Aerial Robot Using Optic Flow Sensing

Science.gov (United States)

Hurd, Michael Brandon

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

Control of Vibratory Energy Harvesters in the Presence of Nonlinearities and Power-Flow Constraints

Science.gov (United States)

Cassidy, Ian L.

Over the past decade, a significant amount of research activity has been devoted to developing electromechanical systems that can convert ambient mechanical vibrations into usable electric power. Such systems, referred to as vibratory energy harvesters, have a number of useful of applications, ranging in scale from self-powered wireless sensors for structural health monitoring in bridges and buildings to energy harvesting from ocean waves. One of the most challenging aspects of this technology concerns the efficient extraction and transmission of power from transducer to storage. Maximizing the rate of power extraction from vibratory energy harvesters is further complicated by the stochastic nature of the disturbance. The primary purpose of this dissertation is to develop feedback control algorithms which optimize the average power generated from stochastically-excited vibratory energy harvesters. This dissertation will illustrate the performance of various controllers using two vibratory energy harvesting systems: an electromagnetic transducer embedded within a flexible structure, and a piezoelectric bimorph cantilever beam. Compared with piezoelectric systems, large-scale electromagnetic systems have received much less attention in the literature despite their ability to generate power at the watt--kilowatt scale. Motivated by this observation, the first part of this dissertation focuses on developing an experimentally validated predictive model of an actively controlled electromagnetic transducer. Following this experimental analysis, linear-quadratic-Gaussian control theory is used to compute unconstrained state feedback controllers for two ideal vibratory energy harvesting systems. This theory is then augmented to account for competing objectives, nonlinearities in the harvester dynamics, and non-quadratic transmission loss models in the electronics. In many vibratory energy harvesting applications, employing a bi-directional power electronic drive to actively

Flow control arrangements for centrifuges

International Nuclear Information System (INIS)

Alderton, G.W.; Davidge, P.C.

1983-01-01

In a centrifuge plant for the separation of uranium isotopes, when a centrifuge machine breaks down, light gas is produced. This gas can cause adjacent machines to break down, so propagating the fault. The present invention provides flow control arrangements in gas pipes to the centrifuge, whereby sudden egress of gas from a failed machine is inhibited. (author)

Information-flow-based Access Control for Virtualized Systems

Directory of Open Access Journals (Sweden)

Dmitriy Aleksandrovich Postoev

2014-12-01

Full Text Available The article is devoted to the method of information-flow-based access control, adopted for virtualized systems. General structure of access control system for virtual infrastructure is proposed.

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.

Effect of flow and active mixing on bacterial growth in a colon-like geometry

Science.gov (United States)

Cremer, Jonas; Segota, Igor; Arnoldini, Markus; Groisman, Alex; Hwa, Terence

The large intestine harbors bacteria from hundreds of species, with bacterial densities reaching up to 1012 cells per gram. Many different factors influence bacterial growth dynamics and thus bacterial density and microbiota composition. One dominant force is flow which can in principle lead to a washout of bacteria from the proximal colon. Active mixing by Contractions of the colonic wall together with bacterial growth might counteract such flow-forces and allow high bacterial densities to occur. As a step towards understanding bacterial growth in the presence of mixing and flow, we constructed an in-vitro setup where controlled wall-deformations of a channel emulate Contractions. We investigate growth along the channel under a steady nutrient inflow. In the limits of no or very frequent Contractions, the device behaves like a plug-flow reactor and a chemostat respectively. Depending on mixing and flow, we observe varying spatial gradients in bacterial density along the channel. Active mixing by deformations of the channel wall is shown to be crucial in maintaining a steady-state bacterial population in the presence of flow. The growth-dynamics is quantitatively captured by a simple mathematical model, with the effect of mixing described by an effective diffusion term.

Field effect control of electro-osmotic flow in microfluidic networks

NARCIS (Netherlands)

van der Wouden, E.J.

2006-01-01

This thesis describes the development of a Field Effect Flow Control (FEFC) system for the control of Electro Osmotic Flow (EOF) in microfluidic networks. For this several aspects of FEFC have been reviewed and a process to fabricate microfluidic channels with integrated electrodes has been

State Space Reduction of Linear Processes using Control Flow Reconstruction

NARCIS (Netherlands)

van de Pol, Jan Cornelis; 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

State Space Reduction of Linear Processes Using Control Flow Reconstruction

NARCIS (Netherlands)

van de Pol, Jan Cornelis; Timmer, Mark; Liu, Zhiming; Ravn, Anders 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

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

Science.gov (United States)

Cary, Robert E.

2015-12-08

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

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

Energy Technology Data Exchange (ETDEWEB)

Cary, Robert B.

2018-04-17

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

Evaluation of steady flow torques and pressure losses in a rotary flow control valve by means of computational fluid dynamics

International Nuclear Information System (INIS)

Okhotnikov, Ivan; Noroozi, Siamak; Sewell, Philip; Godfrey, Philip

2017-01-01

Highlights: • A novel design of a rotary flow control valve driven by a stepper motor is proposed. • The intended use of the valve in the high flow rate independent metering hydraulic system is suggested. • Pressure drops, steady flow torques of the valve for various flow rates and orifice openings are studied by means of computational fluid dynamics. • The discharge coefficient and flow jet angles dependencies on the orifice opening are obtained. • A design method to decrease the flow forces without reducing the flow rate in single-staged valves is demonstrated. - Abstract: In this paper, a novel design of a rotary hydraulic flow control valve has been presented for high flow rate fluid power systems. High flow rates in these systems account for substantial flow forces acting on the throttling elements of the valves and cause the application of mechanically sophisticated multi-staged servo valves for flow regulation. The suggested design enables utilisation of single-stage valves in power hydraulics operating at high flow rates regimes. A spool driver and auxiliary mechanisms of the proposed valve design were discussed and selection criteria were suggested. Analytical expressions for metering characteristics as well as steady flow torques have been derived. Computational fluid dynamics (CFD) analysis of steady state flow regimes was conducted to evaluate the hydraulic behaviour of the proposed valve. This study represents a special case of an independent metering concept applied to the design of power hydraulic systems with direct proportional valve control operating at flow rates above 150 litres per minute. The result gained using parametric CFD simulations predicted the induced torque and the pressure drops due to a steady flow. Magnitudes of these values prove that by minimising the number of spool's mobile metering surfaces it is possible to reduce the flow-generated forces in the new generation of hydraulic valves proposed in this study

Wind tunnel experiments on flow separation control of an Unmanned Air Vehicle by nanosecond discharge plasma aerodynamic actuation

International Nuclear Information System (INIS)

Chen Kang; Liang Hua

2016-01-01

Plasma flow control (PFC) is a new kind of active flow control technology, which can improve the aerodynamic performances of aircrafts remarkably. The flow separation control of an unmanned air vehicle (UAV) by nanosecond discharge plasma aerodynamic actuation (NDPAA) is investigated experimentally in this paper. Experimental results show that the applied voltages for both the nanosecond discharge and the millisecond discharge are nearly the same, but the current for nanosecond discharge (30 A) is much bigger than that for millisecond discharge (0.1 A). The flow field induced by the NDPAA is similar to a shock wave upward, and has a maximal velocity of less than 0.5 m/s. Fast heating effect for nanosecond discharge induces shock waves in the quiescent air. The lasting time of the shock waves is about 80 μs and its spread velocity is nearly 380 m/s. By using the NDPAA, the flow separation on the suction side of the UAV can be totally suppressed and the critical stall angle of attack increases from 20° to 27° with a maximal lift coefficient increment of 11.24%. The flow separation can be suppressed when the discharge voltage is larger than the threshold value, and the optimum operation frequency for the NDPAA is the one which makes the Strouhal number equal one. The NDPAA is more effective than the millisecond discharge plasma aerodynamic actuation (MDPAA) in boundary layer flow control. The main mechanism for nanosecond discharge is shock effect. Shock effect is more effective in flow control than momentum effect in high speed flow control. (paper)

Three Flow Features behind the Flow Control Authority of DBD Plasma Actuator: Result of High-Fidelity Simulations and the Related Experiments

Directory of Open Access Journals (Sweden)

Kozo Fujii

2018-04-01

Full Text Available Both computational and experimental studies are conducted for understanding of the flow separation control mechanism of a DBD (dielectric barrier discharge plasma actuator. Low speed flows over an airfoil are considered. A DBD plasma actuator is attached near the leading edge of an airfoil and the mechanism of flow control of this small device is discussed. The DBD plasma actuator, especially in burst mode, is shown to be very effective for controlling flow separation at Reynolds number of 6.3 × 104, when applied to the flows at an angle of attack higher than the stall. The analysis reveals that the flow structure includes three remarkable features that provide good authority for flow separation control with the appropriate actuator parameters. With proper setting of the actuator parameters to enhance the effective flow features for the application, good flow control can be achieved. Based on the analysis, guidelines for the effective use of DBD plasma actuators are proposed. A DBD plasma actuator is also applied to the flows under cruise conditions. With the DBD plasma actuator attached, a simple airfoil turns out to show higher lift-to-drag ratio than a well-designed airfoil.

Occurrence and prevention of enhanced oxide deposition in boiler flow control orifices

International Nuclear Information System (INIS)

Woolsey, I.S.; Thomas, D.M.; Garbett, K.; Bignold, G.J.

1989-10-01

Once-through boilers, such as those of the AGRs, incorporate flow control orifices at the boiler inlet to ensure a satisfactory flow distribution and stability in the parallel flow paths of the boiler. Deposition of corrosion products in the flow control orifice leads to changes in the orifice pressure loss characteristics, which could lead to problems of flow maldistribution within the boiler, and any adverse consequences resulting from this, such as tube overheating. To date, AGR boiler inlet orifices have not suffered significant fouling due to corrosion products in the boiler feedwater. However, oxide deposition in orifices has been observed in other plants, and in experimental loops operating under conditions very similar to those at inlet to AGR boilers. The lack of deposition in AGR flow control orifices is therefore somewhat surprising. This Report describes studies carried out to examine the factors controlling oxide deposition in flow control orifices, the intention of the work being to explain why deposition has not occurred in AGR boilers to date, and to provide means of preventing deposition in the future should this prove necessary. (author)

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

to free stream velocity U=15 m/s. The objective was to investigate the flow structures induced by and separation controlling behavior of vortex generators on the airfoil. The experimental results show strong separation of the uncontrolled flow whereas an intermittent behavior appears for the controlled...

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 ca...

Experimental investigation of different fluid flow profiles in a rotary multi-bed active magnetic regenerator device

DEFF Research Database (Denmark)

Fortkamp, F. P.; Eriksen, D.; Engelbrecht, K.

2018-01-01

A rotary multi-bed active magnetic regenerator (AMR) device was modified to allow testing different fluid flow waveforms, with different blow fractions (i.e. the fraction of the AMR cycle when there is fluid flow in the regenerators). The different values of blow fraction were generated using dif.......1% was obtained for the largest blow fraction tested (80%). Designs for magnetic refrigerators where the fluid flow waveform can change during operation are also discussed in this paper.......A rotary multi-bed active magnetic regenerator (AMR) device was modified to allow testing different fluid flow waveforms, with different blow fractions (i.e. the fraction of the AMR cycle when there is fluid flow in the regenerators). The different values of blow fraction were generated using...... different cam rings that actuate the poppet valves at the inlet and outlet of the regenerators, controlling how long the valves stay open and the number of valves open at the same time. Results showed that smaller blow fractions yield higher values of temperature span for fixed flow rate and cooling...

CFD Validation and Flow Control of RAE-M2129 S-Duct Diffuser Using CREATETM-AV Kestrel Simulation Tools

Directory of Open Access Journals (Sweden)

Pooneh Aref

2018-03-01

Full Text Available The flow physics modeling and validation of the Royal Aircraft Establishment (RAE subsonic intake Model 2129 (M2129 are presented. This intake has an 18 inches long S duct with a 5.4 inches offset, an external and an internal lip, forward and rear extended ducts, and a center-positioned bullet before the outlet. Steady-state and unsteady experimental data are available for this duct. The measurements include engine face conditions (pressure recovery, static pressure to free-stream total pressure ratio, and distortion coefficient at the worst 60 ∘ sector or DC60, as well as wall static pressure data along the duct. The intake has been modeled with HPCMP CREATE TM -AV Kestrel simulation tools. The validation results are presented including the effects of turbulence models on predictions. In general, very good agreement (difference errors are less than 6% was found between predictions and measurements. Secondary flow at the first bend and a region of flow separation are predicted at the starboard wall with an averaged DC60 coefficient of 0.2945 at the engine face. Next, a passive and an active flow control method are computationally investigated. The passive one uses vane-type vortex generators and the active one has synthetic jet actuators. The results show that considered passive and active flow control methods reduce the distortion coefficient at the engine face and the worst 60 ∘ sector to 0.1361 and 0.0881, respectively. The flow control performance trends agree with those obtained in experiments as well. These results give confidence to apply the Kestrel simulation tools for the intake design studies of new and unconventional vehicles and hence to reduce the uncertainties during their flight testing.

Integrated Lateral Flow Device for Flow Control with Blood Separation and Biosensing

Directory of Open Access Journals (Sweden)

Veronica Betancur

2017-12-01

Full Text Available Lateral flow devices are versatile and serve a wide variety of purposes, including medical, agricultural, environmental, and military applications. Yet, the most promising opportunities of these devices for diagnosis might reside in point-of-care (POC applications. Disposable paper-based lateral flow strips have been of particular interest, because they utilize low-cost materials and do not require expensive fabrication instruments. However, there are constraints on tuning flow rates and immunoassays functionalization in papers, as well as technical challenges in sensors’ integration and concentration units for low-abundant molecular detection. In the present work, we demonstrated an integrated lateral flow device that applied the capillary forces with functionalized polymer-based microfluidics as a strategy to realize a portable, simplified, and self-powered lateral flow device (LFD. The polydimethylsiloxane (PDMS surface was rendered hydrophilic via functionalization with different concentrations of Pluronic F127. Controlled flow is a key variable for immunoassay-based applications for providing enough time for protein binding to antibodies. The flow rate of the integrated LFD was regulated by the combination of multiple factors, including Pluronic F127 functionalized surface properties and surface treatments of microchannels, resistance of the integrated flow resistor, the dimensions of the microstructures and the spacing between them in the capillary pump, the contact angles, and viscosity of the fluids. Various plasma flow rates were regulated and achieved in the whole device. The LFD combined the ability to separate high quality plasma from human whole blood by using a highly asymmetric plasma separation membrane, and created controlled and steady fluid flow using capillary forces produced by the interfacial tensions. Biomarker immunoglobulin G (IgG detection from plasma was demonstrated with a graphene nanoelectronic sensor integrated

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)

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.

Turbulent Flow Modification With Thermoacoustic Waves for Separation Control

Science.gov (United States)

2017-08-24

respectively. At the outlet, the time-average flow is set to be the target state of the sponge zone. In this section, the effects of momentum thickness...Turbulent Flow Modification With Thermoacoustic Waves For Separation Control The views, opinions and/or findings contained in this report are those...currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. Florida State University Sponsored Research Administration 874

Sorting catalytically active polymersome nanoreactors by flow cytometry

NARCIS (Netherlands)

Nallani, M.; Woestenenk, R.; de Hoog, H.P.M.; van Dongen, S.F.M.; Boezeman, J.; Cornelissen, J.J.L.M.; Nolte, R.J.M.; van Hest, J.C.M.

2009-01-01

A strategy that involves a versatile one-step preparation procedure of enzyme filled porous and stable polymeric catalytically active nanoreactors (polymersomes) by flow cytometry was reported. A 1:1 mixture of the polymerase dispersions was analyzed in a Coulter Epics Elite Flow Cytometer, while

A new method for controlling refrigerant flow in automobile air conditioning

Energy Technology Data Exchange (ETDEWEB)

Xuquan Li; Jiangping Chen; Zhijiu Chen [Shanghai Jiao Tong University (China). Institute of Refrigeration and Cryogenics Engineering; Weihua Liu; Wei Hu; Xiaobing Liu [Shanghai Delphi Automotive Air Conditiong Systems Co. Ltd., Changhai (China)

2004-05-01

This paper describes the improvement of the refrigerant flow control method by using an electronic expansion valve (EEV) which is driven by a stepper motor in automobile air conditioning system. An EEV can make a quick response to the abrupt change in the refrigerant flow rate during the change in automobile speed and the thermostatic on/off operation. The flow rate characteristic of the EEV for automobile air conditioning was presented. A microcontroller is used to receive the input signal and generate the output signal to control the opening of the EEV. The fuzzy self-tuning proportional-integral-derivative (PID) control method is employed. Experimental results show that the new control method can feed adequate refrigerant flow into the evaporator in various operations. The evaporator discharge air temperature has dropped by approximately 3{sup o}C as compared with that of the conventional PID control system. (author)

Heat transfer enhancement through control of added perturbation velocity in flow field

International Nuclear Information System (INIS)

Wang, Jiansheng; Wu, Cui; Li, Kangning

2013-01-01

Highlights: ► Three strategies which restrain the flow drag in heat transfer are proposed. ► Added perturbation induces quasi-streamwise vortices around controlled zone. ► The flow and heat transfer features depend on induced quasi-streamwise vortices. ► Vertical strategy has the best synthesis performance of three control strategies. ► Synthesis performance with control strategy is superior to that without strategy. - Abstract: The characteristics of heat transfer and flow, through an added perturbation velocity, in a rectangle channel, are investigated by Large Eddy Simulation (LES). The downstream, vertical, and upstream control strategy, which can suppress the lift of low speed streaks in the process of improving the performance of heat transfer, are adopted in numerical investigation. Taking both heat transfer and flow properties into consideration, the synthesis performance of heat transfer and flow of three control strategies are evaluated. The numerical results show that the flow structure in boundary layer has been varied obviously for the effect of perturbation velocity and induced quasi-streamwise vortices emerging around the controlled zone. The results indicate that the vertical control strategy has the best synthesis performance of the three control strategies, which also has the least skin frication coefficient. The upstream and downstream strategies can improve the heat transfer performance, but the skin frication coefficient is higher than that with vertical control strategy

Intracycle angular velocity control of cross-flow turbines

Science.gov (United States)

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

2017-08-01

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

Improvement of Performance Range of Centrifugal Compressors Gas by Surge Line Modification Using Active Controller Based on Fuzzy Logic

Directory of Open Access Journals (Sweden)

Pezhman Mohammadi

2012-04-01

Full Text Available In this work, surge of prevention is a critical problem in oil and gas industries, particularly when return gas flow or gas flow reduces in transportation of gas pipelines. This paper is illustrated new results about surge control of centrifugal compressors .surge phenomenon is flow unsteady state in compressors which causes damages seriously in compressor construction. Furthermore, it also demonstrates in comparison with anti surge control ،active surge control expands stability range.Active surge control which based on fuzzy logic،is the main idea that used in this investigation. Using fuzzy controller causes an improvement in compressor's condition and increase performance range of the compressor, in addition to prevention of any instability in compressor. The simulation results is also satisfactory.

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...

Engineering analysis of mass flow rate for turbine system control and design

International Nuclear Information System (INIS)

Yoo, Yong H.; Suh, Kune Y.

2011-01-01

Highlights: → A computer code is written to predict the steam mass flow rate through valves. → A test device is built to study the steam flow characteristics in the control valve. → Mass flow based methodology eases the programming and experimental procedures. → The methodology helps express the characteristics of each device of a turbine system. → The results can commercially be used for design and operation of the turbine system. - Abstract: The mass flow rate is determined in the steam turbine system by the area formed between the stem disk and the seat of the control valve. For precise control the steam mass flow rate should be known given the stem lift. However, since the thermal hydraulic characteristics of steam coming from the generator or boiler are changed going through each device, it is hard to accurately predict the steam mass flow rate. Thus, to precisely determine the steam mass flow rate, a methodology and theory are developed in designing the turbine system manufactured for the nuclear and fossil power plants. From the steam generator or boiler to the first bunch of turbine blades, the steam passes by a stop valve, a control valve and the first nozzle, each of which is connected with piping. The corresponding steam mass flow rate can ultimately be computed if the thermal and hydraulic conditions are defined at the stop valve, control valve and pipes. The steam properties at the inlet of each device are changed at its outlet due to geometry. The Compressed Adiabatic Massflow Analysis (CAMA) computer code is written to predict the steam mass flow rate through valves. The Valve Engineered Layout Operation (VELO) test device is built to experimentally study the flow characteristics of steam flowing inside the control valve with the CAMA input data. The Widows' Creek type control valve was selected as reference. CAMA is expected to be commercially utilized to accurately design and operate the turbine system for fossil as well as nuclear power

Wing Tip Drag Reduction at Nominal Take-Off Mach Number: An Approach to Local Active Flow Control with a Highly Robust Actuator System

Directory of Open Access Journals (Sweden)

Matthias Bauer

2016-10-01

Full Text Available This paper discusses wind tunnel test results aimed at advancing active flow control technology to increase the aerodynamic efficiency of an aircraft during take-off. A model of the outer section of a representative civil airliner wing was equipped with two-stage fluidic actuators between the slat edge and wing tip, where mechanical high-lift devices fail to integrate. The experiments were conducted at a nominal take-off Mach number of M = 0.2. At this incidence velocity, separation on the wing section, accompanied by increased drag, is triggered by the strong slat edge vortex at high angles of attack. On the basis of global force measurements and local static pressure data, the effect of pulsed blowing on the complex flow is evaluated, considering various momentum coefficients and spanwise distributions of the actuation effort. It is shown that through local intensification of forcing, a momentum coefficient of less than c μ = 0.6 % suffices to offset the stall by 2.4°, increase the maximum lift by more than 10% and reduce the drag by 37% compared to the uncontrolled flow.

Transient flows in active porous media

DEFF Research Database (Denmark)

Kosmidis, Lefteris I.; Jensen, Kaare Hartvig

2017-01-01

Stimuli-responsivematerials that modify their shape in response to changes in environmental conditions-such as solute concentration, temperature, pH, and stress-are widespread in nature and technology. Applications include micro- and nanoporous materials used in filtration and flow control. The p...

A Computed River Flow-Based Turbine Controller on a Programmable Logic Controller for Run-Off River Hydroelectric Systems

Directory of Open Access Journals (Sweden)

Razali Jidin

2017-10-01

Full Text Available The main feature of a run-off river hydroelectric system is a small size intake pond that overspills when river flow is more than turbines’ intake. As river flow fluctuates, a large proportion of the potential energy is wasted due to the spillages which can occur when turbines are operated manually. Manual operation is often adopted due to unreliability of water level-based controllers at many remote and unmanned run-off river hydropower plants. In order to overcome these issues, this paper proposes a novel method by developing a controller that derives turbine output set points from computed mass flow rate of rivers that feed the hydroelectric system. The computed flow is derived by summation of pond volume difference with numerical integration of both turbine discharge flows and spillages. This approach of estimating river flow allows the use of existing sensors rather than requiring the installation of new ones. All computations, including the numerical integration, have been realized as ladder logics on a programmable logic controller. The implemented controller manages the dynamic changes in the flow rate of the river better than the old point-level based controller, with the aid of a newly installed water level sensor. The computed mass flow rate of the river also allows the controller to straightforwardly determine the number of turbines to be in service with considerations of turbine efficiencies and auxiliary power conservation.

Active control of convection

Energy Technology Data Exchange (ETDEWEB)

Bau, H.H. [Univ. of Pennsylvania, Philadelphia, PA (United States)

1995-12-31

Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

Quality control of the documentation process in electronic economic activities

Directory of Open Access Journals (Sweden)

Krutova A.S.

2017-06-01

Full Text Available It is proved that the main tool that will provide adequate information resources e economic activities of social and economic relations are documenting quality control processes as the basis of global information space. Directions problems as formation evaluation information resources in the process of documentation, namely development tools assess the efficiency of the system components – qualitative assessment; development of mathematical modeling tools – quantitative evaluation. A qualitative assessment of electronic documentation of economic activity through exercise performance, efficiency of communication; document management efficiency; effectiveness of flow control operations; relationship management effectiveness. The concept of quality control process documents electronically economic activity to components which include: the level of workflow; forms adequacy of information; consumer quality documents; quality attributes; type of income data; condition monitoring systems; organizational level process documentation; attributes of quality, performance quality consumer; type of management system; type of income data; condition monitoring systems. Grounded components of the control system electronic document subjects of economic activity. Detected components IT-audit management system economic activity: compliance audit; audit of internal control; detailed multilevel analysis; corporate risk assessment methodology. The stages and methods of processing electronic transactions economic activity during condition monitoring of electronic economic activity.

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...... solver. In order to more accurately simulate wall bounded flows around the immersed boundary, a modified boundary condition is introduced in the k- ω turbulence model. As an example, turbulent flow over a NACA 64418 airfoil with a deformable trailing edge is investigated. Results from numerical...

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.

Forced excitation and active control for the measurement of fluid-elastic forces

International Nuclear Information System (INIS)

Caillaud, Sebastien

1999-01-01

The action of a fluid flow on a tubes bundle is commonly decomposed into a random turbulent excitation and a fluid-elastic excitation. The fluid-elastic forces which are coupled to the tubes movement can be experimentally determined from an analysis of the vibratory response of the structure excited by turbulent forces. For low flow velocities, the turbulent excitation can be insufficient to make the tube significantly vibrate and to permit a correct vibratory analysis. On the opposite side, the structure can become unstable for high flow velocities: the fluid-elastic forces make the fluid-structure damping system fall towards zero. Two experimental methods are proposed in order to extend the considered flow rate. An additional excitation force allows to increase the tube vibration level for improving the signal-noise ratio at low velocities. When the tube is submitted to fluid-elastic instability, an artificial damping contribution by active control allows to stabilize it. Methods are implemented on a flexible tube inserted into rigid tubes bundle water and water-air transverse flows. Two actuator technologies are used: an electromagnetic exciter and piezoelectric actuators. The additional excitation method shows that the fluid-elastic forces remain insignificant at low velocity single phase flow. With the active control method, it is possible to carry out tests beyond the fluid-elastic instability. In two-phase flow, the stabilization of the structure is observed for low vacuum rates. The obtained new results are analyzed with the literature expected results in terms of fluid-elastic coupling and turbulent excitation. (author) [fr

Steady State Stokes Flow Interpolation for Fluid Control

DEFF Research Database (Denmark)

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

2012-01-01

— 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......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...

Multilevel flow modelling of process plant for diagnosis and control

International Nuclear Information System (INIS)

Lind, M.

1982-08-01

The paper describes the multilevel flow modelling methodology which can be used to construct functional models of energy and material processing systems. The models describe mass and energy flow topology on different levels of abstraction and represent the hierarchical functional structure 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 basic for design of control strategies and for the allocation of control tasks to the computer and the plant operator. (author)

Multilevel Flow Modelling of Process Plant for Diagnosis and Control

DEFF Research Database (Denmark)

Lind, Morten

1982-01-01

The paper describes the multilevel flow modelling methodology which can be used to construct functional models of energy and material processing systems. The models describe mass and energy flow topology on different levels of abstraction and represent the hierarchical functional structure...... 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....

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

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

Science.gov (United States)

Kurnia, Jundika C.; Birgersson, Erik; Mujumdar, Arun S.

2011-01-01

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. PMID:24956303

Active control of flow noise sources in turbulent boundary layer on a flat-plate using piezoelectric bimorph film

International Nuclear Information System (INIS)

Song, Woo Seog; Lee, Seung Bae; Shin, Dong Shin; Na, Yang

2006-01-01

The piezoelectric bimorph film, which, as an actuator, can generate more effective displacement than the usual PVDF film, is used to control the turbulent boundary-layer flow. The change of wall pressures inside the turbulent boundary layer is observed by using the multi-channel microphone array flush-mounted on the surface when actuation at the non-dimensional frequency f b + =0.008 and 0.028 is applied to the turbulent boundary layer. The wall pressure characteristics by the actuation to produce local displacement are more dominantly influenced by the size of the actuator module than the actuation frequency. The movement of large-scale turbulent structures to the upper layer is found to be the main mechanism of the reduction in the wall-pressure energy spectrum when the 700ν/u τ -long bimorph film is periodically actuated at the non-dimensional frequency f b + =0.008 and 0.028. The bimorph actuator is triggered with the time delay for the active forcing at a single frequency when a 1/8' pressure-type, pin-holed microphone sensor detects the large-amplitude pressure event by the turbulent spot. The wall-pressure energy in the late-transitional boundary layer is partially reduced near the convection wavenumber by the open-loop control based on the large amplitude event

On the flow around Glauert-Goldschmied body in the narrow channel and separation control strategy

Czech Academy of Sciences Publication Activity Database

Procházka, Pavel P.; Uruba, Václav

2016-01-01

Roč. 16, č. 1 (2016), s. 643-644 ISSN 1617-7061 R&D Projects: GA ČR(CZ) GP14-25354P Institutional support: RVO:61388998 Keywords : PIV * active flow control * Glauert-Goldschmied body Subject RIV: BK - Fluid Dynamics http://onlinelibrary.wiley.com/doi/10.1002/pamm.201610310/full

Fibro-vascular coupling in the control of cochlear blood flow.

Directory of Open Access Journals (Sweden)

Min Dai

Full Text Available 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.We report on a local control mechanism for regulating inner ear blood flow involving fibrocyte signaling. Fibrocytes in the super-strial region are spatially distributed near pre-capillaries of the spiral ligament of the albino guinea pig cochlear lateral wall, as demonstrably shown in transmission electron microscope and confocal images. Immunohistochemical techniques reveal the inter-connected fibrocytes to be positive for Na+/K+ ATPase β1 and S100. The connected fibrocytes display more Ca(2+ signaling than other cells in the cochlear lateral wall as indicated by fluorescence of a Ca(2+ sensor, fluo-4. Elevation of Ca(2+ in fibrocytes, induced by photolytic uncaging of the divalent ion chelator o-nitrophenyl EGTA, results in propagation of a Ca(2+ signal to neighboring vascular cells and vasodilation in capillaries. Of more physiological significance, fibrocyte to vascular cell coupled signaling was found to mediate the sound stimulated increase in cochlear blood flow (CBF. Cyclooxygenase-1 (COX-1 was required for capillary dilation.The findings provide the first evidence that signaling between fibrocytes and vascular cells modulates CBF and is a key mechanism for meeting the cellular metabolic demand of increased sound activity.

Does seismic activity control carbon exchanges between transform-faults in old ocean crust and the deep sea? A hypothesis examined by the EU COST network FLOWS

Science.gov (United States)

Lever, M. A.

2014-12-01

The European Cooperation in Science and Technology (COST)-Action FLOWS (http://www.cost.eu/domains_actions/essem/Actions/ES1301) was initiated on the 25th of October 2013. It is a consortium formed by members of currently 14 COST countries and external partners striving to better understand the interplay between earthquakes and fluid flow at transform-faults in old oceanic crust. The recent occurrence of large earthquakes and discovery of deep fluid seepage calls for a revision of the postulated hydrogeological inactivity and low seismic activity of old oceanic transform-type plate boundaries, and indicates that earthquakes and fluid flow are intrinsically associated. This Action merges the expertise of a large number of research groups and supports the development of multidisciplinary knowledge on how seep fluid (bio)chemistry relates to seismicity. It aims to identify (bio)geochemical proxies for the detection of precursory seismic signals and to develop innovative physico-chemical sensors for deep-ocean seismogenic faults. National efforts are coordinated through Working Groups (WGs) focused on 1) geophysical and (bio)geochemical data acquisition; 2) modelling of structure and seismicity of faults; 3) engineering of deep-ocean physico-chemical seismic sensors; and 4) integration and dissemination. This poster will illustrate the overarching goals of the FLOWS Group, with special focus to research goals concerning the role of seismic activity in controlling the release of carbon from the old ocean crust into the deep ocean.

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.

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.

Two-phase flow measurement by pulsed neutron activation techniques

International Nuclear Information System (INIS)

Kehler, P.

1978-01-01

The Pulsed Neutron Activation (PNA) technique for measuring the mass flow velocity and the average density of two-phase mixtures is described. PNA equipment can be easily installed at different loops, and PNA techniques are non-intrusive and independent of flow regimes. These features of the PNA technique make it suitable for in-situ measurement of two-phase flows, and for calibration of more conventional two-phase flow measurement devices. Analytic relations governing the various PNA methods are derived. The equipment and procedures used in the first air-water flow measurement by PNA techniques are discussed, and recommendations are made for improvement of future tests. In the present test, the mass flow velocity was determined with an accuracy of 2 percent, and average densities were measured down to 0.08 g/cm 3 with an accuracy of 0.04 g/cm 3 . Both the accuracy of the mass flow velocity measurement and the lower limit of the density measurement are functions of the injected activity and of the total number of counts. By using a stronger neutron source and a larger number of detectors, the measurable density can be decreased by a factor of 12 to .007 g/cm 3 for 12.5 cm pipes, and to even lower ranges for larger pipes

Experiencing flow in a workplace physical activity intervention for female health care workers

DEFF Research Database (Denmark)

Elbe, Anne-Marie; Barene, Svein; Strahler, Katharina

2016-01-01

and adherence to regular physical activity 18 weeks after the end of the intervention was found. Furthermore, repeated measures throughout the intervention period showed a significantly different development of flow values over time for the adherers and nonadherers. Flow therefore may be of importance...... for adherence to regular workplace physical activity. Future research needs to investigate the importance of flow in other physical activity settings, especially also for male participants.......Flow is a rewarding psychological state that motivates individuals to repeat activities. This study explored healthcare workers’ flow experiences during a workplace exercise intervention. Seventy-nine females were assigned to either a 12-week football or Zumba exercise intervention and their flow...

Routing power flows in distribution networks using locally controlled power electronics

NARCIS (Netherlands)

Hamelink, J.; Nguyen, P.H.; Kling, W.L.; Ribeiro, P.F.; Groot, de R.J.W.

2012-01-01

The power grid has gradually changed its operation during the recent decades. These developments have encouraged a shift from centralized to decentralized power flow control. A research has been carried out to investigate the possibilities to control power flows using the Smart Power Router (SPR) in

An active, collaborative approach to learning skills in flow cytometry.

Science.gov (United States)

Fuller, Kathryn; Linden, Matthew D; Lee-Pullen, Tracey; Fragall, Clayton; Erber, Wendy N; Röhrig, Kimberley J

2016-06-01

Advances in science education research have the potential to improve the way students learn to perform scientific interpretations and understand science concepts. We developed active, collaborative activities to teach skills in manipulating flow cytometry data using FlowJo software. Undergraduate students were given compensated clinical flow cytometry listmode output (FCS) files and asked to design a gating strategy to diagnose patients with different hematological malignancies on the basis of their immunophenotype. A separate cohort of research trainees was given uncompensated data files on which they performed their own compensation, calculated the antibody staining index, designed a sequential gating strategy, and quantified rare immune cell subsets. Student engagement, confidence, and perceptions of flow cytometry were assessed using a survey. Competency against the learning outcomes was assessed by asking students to undertake tasks that required understanding of flow cytometry dot plot data and gating sequences. The active, collaborative approach allowed students to achieve learning outcomes not previously possible with traditional teaching formats, for example, having students design their own gating strategy, without forgoing essential outcomes such as the interpretation of dot plots. In undergraduate students, favorable perceptions of flow cytometry as a field and as a potential career choice were correlated with student confidence but not the ability to perform flow cytometry data analysis. We demonstrate that this new pedagogical approach to teaching flow cytometry is beneficial for student understanding and interpretation of complex concepts. It should be considered as a useful new method for incorporating complex data analysis tasks such as flow cytometry into curricula. Copyright © 2016 The American Physiological Society.

Higher frequency network activity flow predicts lower frequency node activity in intrinsic low-frequency BOLD fluctuations.

Science.gov (United States)

Bajaj, Sahil; Adhikari, Bhim Mani; Dhamala, Mukesh

2013-01-01

The brain remains electrically and metabolically active during resting conditions. The low-frequency oscillations (LFO) of the blood oxygen level-dependent (BOLD) signal of functional magnetic resonance imaging (fMRI) coherent across distributed brain regions are known to exhibit features of this activity. However, these intrinsic oscillations may undergo dynamic changes in time scales of seconds to minutes during resting conditions. Here, using wavelet-transform based time-frequency analysis techniques, we investigated the dynamic nature of default-mode networks from intrinsic BOLD signals recorded from participants maintaining visual fixation during resting conditions. We focused on the default-mode network consisting of the posterior cingulate cortex (PCC), the medial prefrontal cortex (mPFC), left middle temporal cortex (LMTC) and left angular gyrus (LAG). The analysis of the spectral power and causal flow patterns revealed that the intrinsic LFO undergo significant dynamic changes over time. Dividing the frequency interval 0 to 0.25 Hz of LFO into four intervals slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), slow-3 (0.073-0.198 Hz) and slow-2 (0.198-0.25 Hz), we further observed significant positive linear relationships of slow-4 in-out flow of network activity with slow-5 node activity, and slow-3 in-out flow of network activity with slow-4 node activity. The network activity associated with respiratory related frequency (slow-2) was found to have no relationship with the node activity in any of the frequency intervals. We found that the net causal flow towards a node in slow-3 band was correlated with the number of fibers, obtained from diffusion tensor imaging (DTI) data, from the other nodes connecting to that node. These findings imply that so-called resting state is not 'entirely' at rest, the higher frequency network activity flow can predict the lower frequency node activity, and the network activity flow can reflect underlying structural

Numerical Investigation of Flow Control Feasibility with a Trailing Edge Flap

International Nuclear Information System (INIS)

Zhu, W J; Shen, W Z; Sørensen, J N

2014-01-01

This paper concerns a numerical study of employing an adaptive trailing edge flap to control the lift of an airfoil subject to unsteady inflow conditions. The periodically varying inflow is generated by two oscillating airfoils, which are located upstream of the controlled airfoil. To establish 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 solver. In order to more accurately simulate wall bounded flows around the immersed boundary, a modified boundary condition is introduced in the k- ω turbulence model. As an example, turbulent flow over a NACA 64418 airfoil with a deformable trailing edge is investigated. Results from numerical simulations are convincing and may give some highlights for practical implementations of trailing edge flap to a wind turbine rotor blade

Novel Active Combustion Control Concept for High-Frequency Modulation of Atomized Fuel Flow, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This proposal by Jansen's Aircraft Systems Controls, Inc presents an innovative solution for Active Combustion Control. Relative to the state of the art, this...

Active Boundary Layer Control on a Highly Loaded Turbine Exit Case Profile

Directory of Open Access Journals (Sweden)

Julia Kurz

2018-03-01

Full Text Available A highly loaded turbine exit guide vane with active boundary layer control was investigated experimentally in the High Speed Cascade Wind Tunnel at the University of the German Federal Armed Forces, Munich. The experiments include profile Mach number distributions, wake traverse measurements as well as boundary layer investigations with a flattened Pitot probe. Active boundary layer control by fluidic oscillators was applied to achieve improved performance in the low Reynolds number regime. Low solidity, which can be applied to reduce the number of blades, increases the risk of flow separation resulting in increased total pressure losses. Active boundary layer control is supposed to overcome these negative effects. The experiments show that active boundary layer control by fluidic oscillators is an appropriate way to suppress massive open separation bubbles in the low Reynolds number regime.

Cavitating flow control through continuous tangential mass injection on a 2D hydrofoil at a small attack angle

Directory of Open Access Journals (Sweden)

Timoshevskiy Mikhail V.

2016-01-01

Full Text Available We studied cavitating flow over the suction side of a symmetric 2D foil – a scaled-down model of high-pressure hydroturbine guide vanes (GV – in different cavitation regimes at the attack angle of 3°. High-speed imaging was used to analyze spatial patterns and time dynamics of the gas-vapour cavities. A hydroacoustic pressure transducer was employed to register time-spectra of pressure fluctuations nearby the hydrofoil. A PIV technique was applied to measure the velocity fields and its fluctuations. The active flow control was implemented by means of a continuous liquid supply with different flow rates through a slot channel located in the GV surface. It was found that the active mass injection does not influence the primary flow upstream of the slot channel position. For the cavitation-free and cavitation inception cases, the injection was shown to make the turbulent wake past the GV section more intense. However, at the developed cavitation regimes the active flow management made it possible to reduce substantially the amplitude or even totally suppress the periodic cavity length oscillations and pressure pulsations associated with them.

Power flow analysis for islanded microgrid in hierarchical structure of control system using optimal control theory

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Thang Diep Thanh

2017-12-01

Full Text Available In environmental uncertainties, the power flow problem in islanded microgrid (MG becomes complex and non-trivial. The optimal power flow (OPL problem is described in this paper by using the energy balance between the power generation and load demand. The paper also presents the hierarchical control structure which consists of primary, secondary, tertiary, and emergency controls. Clearly, optimal power flow (OPL which implements a distributed tertiary control in hierarchical control. MG consists of diesel engine generator (DEG, wind turbine generator (WTG, and photovoltaic (PV power. In the control system considered, operation planning is realized based on profiles such that the MG, load, wind and photovoltaic power must be forecasted in short-period, meanwhile the dispatch source (i.e., DEG needs to be scheduled. The aim of the control problem is to find the dispatch output power by minimizing the total cost of energy that leads to the Hamilton-Jacobi-Bellman equation. Experimental results are presented, showing the effectiveness of optimal control such that the generation allows demand profile.

Numerical Characterisation of Active Drag and Lift Control for a Circular Cylinder in Cross-Flow

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Philip McDonald

2017-11-01

Full Text Available Synthetic jet actuators have shown promise to control drag and lift for a bluff body in cross-flow. Using unsteady RANS CFD modelling, a significant modification of the drag coefficient for a circular cylinder in cross-flow at R e = 3900 is achieved by varying the actuation frequency. The variation in actuation frequency corresponds to a range in Stokes number of 2.4 < S t o < 6.4. The trends in drag coefficient modification largely agree with the findings of past publications, achieving a maximum drag reduction at S t o = 4.9 for a fixed jet Reynolds number of the synthetic jet of R e U ¯ o = 12. A decrease in the adverse pressure gradient near the jet orifice correlated with a momentum increase in the viscous sublayer and stronger vortical structures at the rear of the cylinder. In these same conditions, a decrease in turbulence intensity was observed in the far field wake, which is a relevant finding in the context of wind and tidal turbine arrays.

Global regularizing flows with topology preservation for active contours and polygons.

Science.gov (United States)

Sundaramoorthi, Ganesh; Yezzi, Anthony

2007-03-01

Active contour and active polygon models have been used widely for image segmentation. In some applications, the topology of the object(s) to be detected from an image is known a priori, despite a complex unknown geometry, and it is important that the active contour or polygon maintain the desired topology. In this work, we construct a novel geometric flow that can be added to image-based evolutions of active contours and polygons in order to preserve the topology of the initial contour or polygon. We emphasize that, unlike other methods for topology preservation, the proposed geometric flow continually adjusts the geometry of the original evolution in a gradual and graceful manner so as to prevent a topology change long before the curve or polygon becomes close to topology change. The flow also serves as a global regularity term for the evolving contour, and has smoothness properties similar to curvature flow. These properties of gradually adjusting the original flow and global regularization prevent geometrical inaccuracies common with simple discrete topology preservation schemes. The proposed topology preserving geometric flow is the gradient flow arising from an energy that is based on electrostatic principles. The evolution of a single point on the contour depends on all other points of the contour, which is different from traditional curve evolutions in the computer vision literature.

ac power control in the Core Flow Test Loop

International Nuclear Information System (INIS)

McDonald, D.W.

1980-01-01

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

Thermodynamic framework for discrete optimal control in multiphase flow systems

Science.gov (United States)

Sieniutycz, Stanislaw

1999-08-01

Bellman's method of dynamic programming is used to synthesize diverse optimization approaches to active (work producing) and inactive (entropy generating) multiphase flow systems. Thermal machines, optimally controlled unit operations, nonlinear heat conduction, spontaneous relaxation processes, and self-propagating wave fronts are all shown to satisfy a discrete Hamilton-Jacobi-Bellman equation and a corresponding discrete optimization algorithm of Pontryagin's type, with the maximum principle for a Hamiltonian. The extremal structures are always canonical. A common unifying criterion is set for all considered systems, which is the criterion of a minimum generated entropy. It is shown that constraints can modify the entropy functionals in a different way for each group of the processes considered; thus the resulting structures of these functionals may differ significantly. Practical conclusions are formulated regarding the energy savings and energy policy in optimally controlled systems.

Flow shop scheduling algorithm to optimize warehouse activities

Directory of Open Access Journals (Sweden)

P. Centobelli

2016-01-01

Full Text Available Successful flow-shop scheduling outlines a more rapid and efficient process of order fulfilment in warehouse activities. Indeed the way and the speed of order processing and, in particular, the operations concerning materials handling between the upper stocking area and a lower forward picking one must be optimized. The two activities, drops and pickings, have considerable impact on important performance parameters for Supply Chain wholesaler companies. In this paper, a new flow shop scheduling algorithm is formulated in order to process a greater number of orders by replacing the FIFO logic for the drops activities of a wholesaler company on a daily basis. The System Dynamics modelling and simulation have been used to simulate the actual scenario and the output solutions. Finally, a t-Student test validates the modelled algorithm, granting that it can be used for all wholesalers based on drop and picking activities.

Inter-eNB Flow Control for Heterogeneous Networks with Dual Connectivity

DEFF Research Database (Denmark)

Wang, Hua; Rosa, Claudio; Pedersen, Klaus I.

2015-01-01

the gain provided by DC, an efficient flow control of data between the involved macro and small cell eNBs is proposed. It is demonstrated how proper configuration of the proposed flow control algorithm offers efficient trade-offs between reducing the probability that one of the eNBs involved in the DC runs...

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.

Developments in Pulsed Neutron Activation for Determination of Water Flow in Pipes

CERN Document Server

Mattsson, H

2003-01-01

In PNA (pulsed neutron activation) it is important that the measured data can be related to the total mass flow. In this thesis two fundamental problems of the measurement technique and data treatment have been investigated: transport/mixing and background radiation. The principle of PNA is to introduce a radioactive substance into a pipe by bombarding fluid in the pipe with neutron pulses. The fluid in the pipe is activated and subsequently transported and mixed with the flow. Gamma radiation emitted from the activity is measured with one or two detectors downstream from the activation point. The time-resolved signal from the detectors is used to calculate the average velocity of the water flow. Due to the short distance between the neutron generator and the pipe the activity in the pipe becomes highly inhomogeneous. The transport and mixing of the activity were simulated using colour which was injected into the flow. It was found that the inhomogeneous activity distribution must be taken into account if the...

Final Technical Report: Numerical and Experimental Investigation of Turbulent Transport Control via Shaping of Radial Plasma Flow Profiles

Energy Technology Data Exchange (ETDEWEB)

Schuster, Eugenio

2014-05-02

The strong coupling between the different physical variables involved in the plasma transport phenomenon and the high complexity of its dynamics call for a model-based, multivariable approach to profile control where those predictive models could be exploited. The overall objective of this project has been to extend the existing body of work by investigating numerically and experimentally active control of unstable fluctuations, including fully developed turbulence and the associated cross-field particle transport, via manipulation of flow profiles in a magnetized laboratory plasma device. Fluctuations and particle transport can be monitored by an array of electrostatic probes, and Ex B flow profiles can be controlled via a set of biased concentric ring electrodes that terminate the plasma column. The goals of the proposed research have been threefold: i- to develop a predictive code to simulate plasma transport in the linear HELCAT (HELicon-CAThode) plasma device at the University of New Mexico (UNM), where the experimental component of the proposed research has been carried out; ii- to establish the feasibility of using advanced model-based control algorithms to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles, iii- to investigate the fundamental nonlinear dynamics of turbulence and transport physics. Lehigh University (LU), including Prof. Eugenio Schuster and one full-time graduate student, has been primarily responsible for control-oriented modeling and model-based control design. Undergraduate students have also participated in this project through the National Science Foundation Research Experience for Undergraduate (REU) program. The main goal of the LU Plasma Control Group has been to study the feasibility of controlling turbulence-driven transport by shaping the radial poloidal flow profile (i.e., by controlling flow shear) via biased concentric ring electrodes.

Correlation between unstimulated salivary flow, pH and streptococcus mutans, analysed with real time PCR, in caries-free and caries-active children.

Science.gov (United States)

Abbate, G M; Borghi, D; Passi, A; Levrini, L

2014-03-01

Evaluate the correlations between unstimulated salivary flow, pH and level of S. mutans, analysed through real time PCR, in caries-free and caries-active children. Thirty healthy children were divided into 2 groups: test group (DMFT/dmft ≥ 3 and at least 1 active caries lesion) and control group (DMFT/dmft=0). Un-stimulated saliva was collected, pH was measured and S. mutans and total bacterial amount were evaluated with real-time PCR analysis. Unstimulated salivary flow in the test group was significantly lower (p = 0.0269) compared to group control. The level of S. mutans was higher in the test group (p = 0.176), and an inverse correlation was recorded between total bacterial amount and un-stimulated salivary flow (p = 0.063). In the control group a positive relationship was found between total bacterial amount and S. mutans (p = 0.045) and an inverse correlation between pH and S. mutans (p = 0.088). A t-test and a linear regression analysis were performed. A higher salivary flow and an increased salivary pH seem to represent protective factors against caries in children, while high levels of S. mutans are correlated with caries active lesions. Caries risk assessment should be performed considering all parameters involved in the development of the disease.

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

Modeling generalized interline power-flow controller (GIPFC using 48-pulse voltage source converters

Directory of Open Access Journals (Sweden)

Amir Ghorbani

2018-05-01

Full Text Available Generalized interline power-flow controller (GIPFC is one of the voltage-source controller (VSC-based flexible AC transmission system (FACTS controllers that can independently regulate the power-flow over each transmission line of a multiline system. This paper presents the modeling and performance analysis of GIPFC based on 48-pulsed voltage-source converters. This paper deals with a cascaded multilevel converter model, which is a 48-pulse (three levels voltage source converter. The voltage source converter described in this paper is a harmonic neutralized, 48-pulse GTO converter. The GIPFC controller is based on d-q orthogonal coordinates. The algorithm is verified using simulations in MATLAB/Simulink environment. Comparisons between unified power flow controller (UPFC and GIPFC are also included. Keywords: Generalized interline power-flow controller (GIPFC, Voltage source converter (VCS, 48-pulse GTO converter

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.

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

2017-12-01

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.

Orifice design for the control of coupled region flow

International Nuclear Information System (INIS)

Atherton, R.; Spadaro, P.R.; Brummerhop, F.G.

1975-01-01

A fluid system arrangement for nuclear reactors is described comprising a triplate orifice apparatus which simultaneously controls core flow distribution, flow rate ratio between hydraulically coupled regions of the blanket and radial static pressure gradients entering and leaving the blanket fuel region. The design of the apparatus is based on the parameters of the diameter of the orifice holes, the friction factor, and expansion, contraction and turning pressure loss coefficients of the geometry of each orifice region. These above parameters are properly matched to provide the desired pressure drop, flow split and negligible cross flow at the interface of standard and power-flattened open lattice blanket regions. (U.S.)

Active Control of Separation From the Flap of a Supercritical Airfoil

Science.gov (United States)

Melton, LaTunia Pack; Yao, Chung-Sheng; Seifert, Avi

2006-01-01

Zero-mass-flux periodic excitation was applied at several regions on a simplified high-lift system to delay the occurrence of flow separation. The NASA Energy Efficient Transport (EET) supercritical airfoil was equipped with a 15% chord simply hinged leading edge flap and a 25% chord simply hinged trailing edge flap. Detailed flow features were measured in an attempt to identify optimal actuator placement. The measurements included steady and unsteady model and tunnel wall pressures, wake surveys, arrays of surface hot-films, flow visualization, and particle image velocimetry (PIV). The current paper describes the application of active separation control at several locations on the deflected trailing edge flap. High frequency (F(+) approximately equal to 10) and low frequency amplitude modulation (F(+) sub AM approximately equal to 1) of the high frequency excitation were used for control. It was noted that the same performance gains were obtained with amplitude modulation and required only 30% of the momentum input required by pure sine excitation.

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....

Drag reduction in channel flow using nonlinear control

Science.gov (United States)

Keefe, Laurence R.

1993-01-01

Two nonlinear control schemes have been applied to the problem of drag reduction in channel flow. Both schemes have been tested using numerical simulations at a mass flux Reynolds numbers of 4408, utilizing 2D nonlinear neutral modes for goal dynamics. The OGY-method, which requires feedback, reduces drag to 60-80 percent of the turbulent value at the same Reynolds number, and employs forcing only within a thin region near the wall. The H-method, or model-based control, fails to achieve any drag reduction when starting from a fully turbulent initial condition, but shows potential for suppressing or retarding laminar-to-turbulent transition by imposing instead a transition to a low drag, nonlinear traveling wave solution to the Navier-Stokes equation. The drag in this state corresponds to that achieved by the OGY-method. Model-based control requires no feedback, but in experiments to date has required the forcing be imposed within a thicker layer than the OGY-method. Control energy expenditures in both methods are small, representing less than 0.1 percent of the uncontrolled flow's energy.

Demonstration of robust micromachined jet technology and its application to realistic flow control problems

International Nuclear Information System (INIS)

Chang, Sung Pil

2006-01-01

This paper describes the demonstration of successful fabrication and initial characterization of micromachined pressure sensors and micromachined jets (microjets) fabricated for use in macro flow control and other applications. In this work, the microfabrication technology was investigated to create a micromachined fluidic control system with a goal of application in practical fluids problems, such as UAV (Unmanned Aerial Vehicle)-scale aerodynamic control. Approaches of this work include : (1) the development of suitable micromachined synthetic jets (microjets) as actuators, which obviate the need to physically extend micromachined structures into an external flow ; and (2) a non-silicon alternative micromachining fabrication technology based on metallic substrates and lamination (in addition to traditional MEMS technologies) which will allow the realization of larger scale, more robust structures and larger array active areas for fluidic systems. As an initial study, an array of MEMS pressure sensors and an array of MEMS modulators for orifice-based control of microjets have been fabricated, and characterized. Both pressure sensors and modulators have been built using stainless steel as a substrate and a combination of lamination and traditional micromachining processes as fabrication technologies

Demonstration of robust micromachined jet technology and its application to realistic flow control problems

Energy Technology Data Exchange (ETDEWEB)

Chang, Sung Pil [Inha University, Incheon (Korea, Republic of)

2006-04-15

This paper describes the demonstration of successful fabrication and initial characterization of micromachined pressure sensors and micromachined jets (microjets) fabricated for use in macro flow control and other applications. In this work, the microfabrication technology was investigated to create a micromachined fluidic control system with a goal of application in practical fluids problems, such as UAV (Unmanned Aerial Vehicle)-scale aerodynamic control. Approaches of this work include : (1) the development of suitable micromachined synthetic jets (microjets) as actuators, which obviate the need to physically extend micromachined structures into an external flow ; and (2) a non-silicon alternative micromachining fabrication technology based on metallic substrates and lamination (in addition to traditional MEMS technologies) which will allow the realization of larger scale, more robust structures and larger array active areas for fluidic systems. As an initial study, an array of MEMS pressure sensors and an array of MEMS modulators for orifice-based control of microjets have been fabricated, and characterized. Both pressure sensors and modulators have been built using stainless steel as a substrate and a combination of lamination and traditional micromachining processes as fabrication technologies.

Controlled synthesis of colloidal silver nanoparticles in capillary micro-flow reactor

International Nuclear Information System (INIS)

He Shengtai; Liu Yulan; Maeda, Hideaki

2008-01-01

In this study, using a polytetrafluoroethylene (PTFE) capillary tube as a micro-flow reactor, well-dispersed colloidal silver nanoparticles were controllably synthesized with different flow rates of precursory solution. Scanning transmission electron microscopy images and UV-visible absorbance spectra showed that silver nanoparticles with large size can be prepared with slow flow rate in the PTFE capillary reactor. The effects of tube diameters on the growth of colloidal silver nanoparticles were investigated. Experiment results demonstrated that using tube with small diameter was more propitious for the controllable synthesis of silver nanoparticles with different sizes.

A Calculus for Control Flow Analysis of Security Protocols

DEFF Research Database (Denmark)

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

2004-01-01

The design of a process calculus for anaysing security protocols is governed by three factors: how to express the security protocol in a precise and faithful manner, how to accommodate the variety of attack scenarios, and how to utilise the strengths (and limit the weaknesses) of the underlying...... 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...

A model for investigating the control of muscle blood flow: the masseteric artery in conscious rabbits

International Nuclear Information System (INIS)

Roatta, S; Mohammed, M; Turturici, M; Milano, L; Passatore, M

2010-01-01

The complex interplay of neural, metabolic, myogenic and mechanical mechanisms that regulate blood flow in skeletal muscle (MBF) is still incompletely understood. For the first time, a method is presented for high time-resolution recording of MBF from a purely muscular artery in physiological conditions. Ultrasound perivascular flow probes were implanted (n = 15) mono- or bilaterally around the masseteric branch of the facial artery in nine rabbits and tested up to 16 days after implant. Reliable and stable recordings were achieved in 50% of implants. Blood flow was observed to increase from a resting level of 0.2–0.3 ml min −1 up to 4.0–6.0 ml min −1 during spontaneous masticatory activity. In addition, within single masticatory cycles marked back flow transients could be observed (peak flow = −10 ml min −1 ) during powerful masticatory strokes but not during mild mastication. The possibility of (1) surgically removing the sympathetic supply to the relevant vascular bed and of (2) bilaterally monitoring the perfusion of masseter muscles thus allowing to use one side as control side for different types of interventions makes this model a useful tool for disentangling the different mechanisms involved in the control of MBF. (note)

The effect of flow limitation on the cardiorespiratory response to arousal from sleep under controlled conditions of chemostimulation in healthy older adults.

Science.gov (United States)

Goff, Elizabeth A; Nicholas, Christian L; Kleiman, Jan; Spear, Owen; Morrell, Mary J; Trinder, John

2012-12-01

The influence of flow limitation on the magnitude of the cardiorespiratory response to arousal from sleep is of interest in older people, because they experience considerable flow limitation and frequent arousals from sleep. We studied older flow-limiting subjects, testing the hypothesis that the cardiorespiratory activation response would be larger when arousal occurred during flow limitation, compared to no flow limitation, and chemical stimuli were controlled. In 11 older adults [mean ± standard deviation (SD) age: 68 ± 5 years] ventilation was stabilized using continuous positive airway pressure, and flow limitation was induced by dialling down the pressure. Partial pressure of end-tidal carbon dioxide (PetCO(2)) was maintained by titration of the inspired CO(2) and hyperoxia was maintained using 40% O(2) balanced with nitrogen. Flow limitation at the time of arousal did not augment cardiovascular activation response (heart rate P = 0.7; systolic blood pressure P = 0.6; diastolic blood pressure P = 0.3), whereas ventilation was greater following arousals during flow limitation compared to no flow limitation (P sleep is not influenced by flow limitation at the time of arousal, when chemical stimuli are controlled in older adults. This finding may contribute to the decreased cardiovascular burden associated with sleep-disordered breathing reported in older adults, although our data do not exclude the possibility that flow limitation in the presence of mild hypoxic hypercapnia could increase the cardiovascular response to arousal. © 2012 European Sleep Research Society.

Field-effect Flow Control in Polymer Microchannel Networks

Science.gov (United States)

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

2003-01-01

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

Predictive Flow Control to Minimize Convective Time Delays

Science.gov (United States)

2013-08-19

external flows around air vehicles or ground based systems such as bridges and buildings, internal flows in pipes and propulsion systems, acoustical...3437, 1977. [4] Bridges , D. H., "The Asymmetric Vortex Wake Problem - Asking the Right Question," A/AA Paper 2006-3553, 2006. [5) Deng, X. Y., Tian, W...Aircraft, Vol. 42, No. 2, 2003, pp. 42~23. [8] Darden, L. and Komerath, N., "Forebody Vortex Control at High Incidence using a Moveable Nose Stagnation

Active Control of Flow Separation Over an Airfoil

Science.gov (United States)

Ravindran, S. S.

1999-01-01

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing on airfoils. The unsteady suction and blowing is introduced at the leading edge of the airfoil in the form of tangential jet. Numerical solutions are obtained using Reynolds-Averaged viscous compressible Navier-Stokes equations. Unsteady suction and blowing is investigated as a means of separation control to obtain lift on airfoils. The effect of blowing coefficients on lift and drag is investigated. The numerical simulations are compared with experiments from the Tel-Aviv University (TAU). These results indicate that unsteady suction and blowing can be used as a means of separation control to generate lift on airfoils.

Power flow control strategy in distribution network for dc type distributed energy resource at load bus

International Nuclear Information System (INIS)

Hanif, A.; Choudhry, M.A.

2013-01-01

This research work presents a feed forward power flow control strategy in the secondary distribution network working in parallel with a DC type distributed energy resource (DER) unit with SPWM-IGBT Voltage Source Converter (VSC). The developed control strategy enables the VSC to be used as power flow controller at the load bus in the presence of utility supply. Due to the investigated control strategy, power flow control from distributed energy resource (DER) to common load bus is such that power flows to the load without facing any power quality problem. The technique has an added advantage of controlling power flow without having a dedicated power flow controller. The SPWM-IGBT VSC is serving the purpose of dc-ac converter as well as power flow controller. Simulations for a test system using proposed power flow control strategy are carried out using SimPower Systems toolbox of MATLAB at the rate and Simulink at the rate. The results show that a reliable, effective and efficient operation of DC type DER unit in coordination with main utility network can be achieved. (author)

Precision flow-controlled Rb-82 generator for bolus or constant-infusion studies of the heart and brain

International Nuclear Information System (INIS)

Yano, Y.; Cahoon, J.L.; Budinger, T.F.

1981-01-01

A precision flow-controlled rubidium-82 generator has been constructed to deliver 76-sec Rb-82 at either fast or slow flow rates for bolus or constant-infusion studies. A stepping motor drive is interfaced to a microprocessor for pulsed control of flow rate to deliver the saline eluant solution from a large-volume (150 ml) machined pumping syringe through an alumina column that retains the 25-day Sr-82 parent. The generator system delivers 70-90% of the maximum Rb-82 activity in a 20-25 ml bolus elution of 2% NaCl. The Sr-82/Sr-85 breakthrough is 10 -7 - 10 -6 . Both yield and breakthrough are functions of column length and flow rate. Six separate Sr-82 loadings of the generator were evaluated over a period of nearly 2 yr in studies of myocardial blood perfusion and permeability changes in the blood-brain barrier. Sterility and apyrogenicity of the Rb-82 eluate were maintained during multiple elutions and long-term use of 3-4 mo for each generator loading

Control of Networked Traffic Flow Distribution - A Stochastic Distribution System Perspective

Energy Technology Data Exchange (ETDEWEB)

Wang, Hong [Pacific Northwest National Laboratory (PNNL); Aziz, H M Abdul [ORNL; Young, Stan [National Renewable Energy Laboratory (NREL); Patil, Sagar [Pacific Northwest National Laboratory (PNNL)

2017-10-01

Networked traffic flow is a common scenario for urban transportation, where the distribution of vehicle queues either at controlled intersections or highway segments reflect the smoothness of the traffic flow in the network. At signalized intersections, the traffic queues are controlled by traffic signal control settings and effective traffic lights control would realize both smooth traffic flow and minimize fuel consumption. Funded by the Energy Efficient Mobility Systems (EEMS) program of the Vehicle Technologies Office of the US Department of Energy, we performed a preliminary investigation on the modelling and control framework in context of urban network of signalized intersections. In specific, we developed a recursive input-output traffic queueing models. The queue formation can be modeled as a stochastic process where the number of vehicles entering each intersection is a random number. Further, we proposed a preliminary B-Spline stochastic model for a one-way single-lane corridor traffic system based on theory of stochastic distribution control.. It has been shown that the developed stochastic model would provide the optimal probability density function (PDF) of the traffic queueing length as a dynamic function of the traffic signal setting parameters. Based upon such a stochastic distribution model, we have proposed a preliminary closed loop framework on stochastic distribution control for the traffic queueing system to make the traffic queueing length PDF follow a target PDF that potentially realizes the smooth traffic flow distribution in a concerned corridor.

Internal hydraulic control in the Little Belt, Denmark - observations of flow configurations and water mass formation

Science.gov (United States)

Holtegaard Nielsen, Morten; Vang, Torben; Chresten Lund-Hansen, Lars

2017-12-01

Internal hydraulic control, which occurs when stratified water masses are forced through an abrupt constriction, plays an enormous role in nature on both large and regional scales with respect to dynamics, circulation, and water mass formation. Despite a growing literature on this subject surprisingly few direct observations have been made that conclusively show the existence of and the circumstances related to internal hydraulic control in nature. In this study we present observations from the Little Belt, Denmark, one of three narrow straits connecting the Baltic Sea and the North Sea. The observations (comprised primarily of along-strait, detailed transects of salinity and temperature; continuous observations of flow velocity, salinity, and temperature at a permanent station; and numerous vertical profiles of salinity, temperature, fluorescence, and flow velocity in various locations) show that internal hydraulic control is a frequently occurring phenomenon in the Little Belt. The observations, which are limited to south-going flows of approximately two-layered water masses, show that internal hydraulic control may take either of two configurations, i.e. the lower or the upper layer being the active, accelerating one. This is connected to the depth of the pycnocline on the upstream side and the topography, which is both deepening and contracting toward the narrow part of the Little Belt. The existence of two possible flow configurations is known from theoretical and laboratory studies, but we believe that this has never been observed in nature and reported before. The water masses formed by the intense mixing, which is tightly connected with the presence of control, may be found far downstream of the point of control. The observations show that these particular water masses are associated with chlorophyll concentrations that are considerably higher than in adjacent water masses, showing that control has a considerable influence on the primary production and

Simulation of corrosion product activity in pressurized water reactors under flow rate transients

International Nuclear Information System (INIS)

Mirza, Anwar M.; Mirza, Nasir M.; Mir, Imran

1998-01-01

Simulation of coolant activation due to corrosion products and impurities in a typical pressurized water reactor has been done under flow rate transients. Employing time dependent production and losses of corrosion products in the primary coolant path an approach has been developed to calculate the coolant specific activity. Results for 24 Na, 56 Mn, 59 Fe, 60 Co and 99Mo show that the specific activity in primary loop approaches equilibrium value under normal operating conditions fairly rapidly. Predominant corrosion product activity is due to Mn-56. Parametric studies at full power for various ramp decreases in flow rate show initial decline in the activity and then a gradual rise to relatively higher saturation values. The minimum value and the time taken to reach the minima are strong functions of the slope of linear decrease in flow rate. In the second part flow rate coastdown was allowed to occur at different flow half-times. The reactor scram was initiated at 90% of the normal flow rate. The results show that the specific activity decreases and the rate of decrease depends on pump half time and the reactor scram conditions

Heat-flow and temperature control in Tian–Calvet microcalorimeters: toward higher detection limits

International Nuclear Information System (INIS)

Vilchiz-Bravo, L E; Pacheco-Vega, A; Handy, B E

2010-01-01

Strategies based on the principle of heat flow and temperature control were implemented, and experimentally tested, to increase the sensitivity of a Tian–Calvet microcalorimeter for measuring heats of adsorption. Here, both heat-flow and temperature control schemes were explored to diminish heater-induced thermal variations within the heat sink element, hence obtaining less noise in the baseline signal. PID controllers were implemented within a closed-loop system to perform the control actions in a calorimetric setup. The experimental results demonstrate that the heat flow control strategy provided a better baseline stability when compared to the temperature control. The effects on the results stemming from the type of power supply used were also investigated

Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients.

Science.gov (United States)

Matimati, Ignatious; Verboom, G Anthony; Cramer, Michael D

2014-01-01

Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 μm mesh from which nutrients could move by diffusion or mass-flow (termed 'mass-flow' treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed 'interception' treatment). 'Mass-flow' plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (gs), 1.2-fold higher intercellular [CO2] (Ci), and 3.4-fold lower water use efficiency than 'interception' plants, despite comparable values of photosynthetic rate (A). E, gs, and Ci first increased and then decreased with increasing distance from the N source to values even lower than those of 'interception' plants. 'Mass-flow' plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties.

Comparison of platelet activation through hinge vs bulk flow in mechanical heart valves

Science.gov (United States)

Hedayat, Mohammadali; Borazjani, Iman

2017-11-01

Bileaflet mechanical heart valves increase the risk of thrombus formation in patients which is believed to be initiated by platelet activation. Platelets can be activated by the elevated shear stresses in the bulk flow during the systole phase or the flow through the hinge during the diastole. However, the importance of platelet activation by the bulk flow vs the hinge in MHVs has yet to be studied. Here, we investigate the contribution of each of the above mechanisms to the activation of platelets in MHs by performing simulation of the flow through a 25mm St. Jude Medical valve placed in a straight aorta. Two different gap sizes (250 and 150 micrometer) are used in this study. The simulations are done using a sharp interface curvilinear immersed boundary method along with a strong-coupling algorithm for FSI solver on overset grids. The platelet activation through the hinge for different gap sizes is compared to the activation in the bulk flow using two platelet activation models to ensure the consistency of the results. Our results for all gap sizes using different activation models show that the integration of platelet activation caused by the bulk flow is several times higher in comparison to the activation through the hinge. This work is supported by the American Heart Association Grant 13SDG17220022, and the computational resources were partly provided by Center for Computational Research (CCR) at University at Buffalo.

The effects of autonomy-supportive and controlling teaching behaviour in biology lessons with primary and secondary experiences on students' intrinsic motivation and flow-experience

Science.gov (United States)

Hofferber, Natalia; Basten, Melanie; Großmann, Nadine; Wilde, Matthias

2016-09-01

Self-Determination Theory and Flow Theory propose that perceived autonomy fosters the positive qualities of motivation and flow-experience. Autonomy-support can help to maintain students' motivation in very interesting learning activities and may lead to an increase in the positive qualities of motivation in less interesting learning activities. This paper investigates whether autonomy-supportive or controlling teaching behaviour influence students' motivation and flow-experience in biology class. In study 1, 158 students of grade six worked on the adaptations of Harvest Mice (Micromys minutus) with living animals. The 153 sixth graders of study 2 dealt with the same content but instead worked with short films on laptops. Previous studies have shown that students perceive film sequences as less interesting than working with living animals. Students' intrinsic motivation and flow-experience were measured at the end of the first and the third lesson. In study 1, autonomy-supportive teaching behaviour led to significant differences in students' intrinsic motivation and flow-experience when compared to controlling teaching behaviour. In study 2, motivation and flow-experience were not always in line with theory. The positive effects of autonomy-supportive and the non-beneficial effects of the controlling teaching behaviour seem to be dependent on the interestingness of the teaching material.

Topographic control of oceanic flows in deep passages and straits

Science.gov (United States)

Whitehead, J. A.

1998-08-01

Saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next, depending on the source of bottom water. Flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next. Examples in the Atlantic include flow in the Romanche Fracture Zone, the Vema Channel, the Ceara Abyssal Plain, the Anegada-Jungfern passage, and the Discovery Gap, but there are many more. Theoretical predictions of volume flux using a method that requires only conductivity-temperature-depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and/or geostrophic estimates for seven cases. The ratio of prediction to volume flux estimate ranges from 1.0 to 2.7. Some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins. Theory of the influence of rotation on such critical flows is reviewed. Predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods.

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

Flow measurement and control in the defense waste process

International Nuclear Information System (INIS)

Heckendorn, F.M. II.

1985-01-01

The Defense Waste Processing Facility (DWPF) for immobilizing Savannah River Plant (SRP) high-level radioactive waste is now under construction. Previously stored waste is retrieved and processed into a glass matrix for permanent storage. The equipment operates in an entirely remote environment for both processing and maintenance due to the highly radioactive nature of the waste. A fine powdered glass frit is mixed with the waste prior to its introduction as a slurry into an electric glass furnace. The slurry is Bingham plastic in nature and of high viscosity. This combination of factors has created significant problems in flow measurement and control. Specialized pieces of equipment have been demonstrated that will function properly in a highly abrasive environment while receiving no maintenance during their lifetime. Included are flow meters, flow control technology, flow switching, and remote connections. No plastics or elastomers are allowed in contact with fluids and all electronic components are mounted remotely. Both two- and three-way valves are used. Maintenance is by crane replacement of process sections, utilizing specialized connectors. All portions of the above are now operating full scale (radioactively cold) at the test facility at SRP. 4 references, 8 figures

Synthetic Jet Interactions with Flows of Varying Separation Severity and Spanwise Flow Magnitude

Science.gov (United States)

Monastero, Marianne; Lindstrom, Annika; Amitay, Michael

2017-11-01

Flow physics associated with the interactions of synthetic jet actuators with a highly three-dimensional separated flow over a flapped airfoil were investigated experimentally and analyzed using stereo particle image velocimetry (SPIV) and surface pressure data. Increased understanding of active flow control devices in flows which are representative of airplane wings or tails can lead to actuator placement (i.e., chordwise location, spanwise spacing) with the greatest beneficial effect on performance. An array of discrete synthetic jets was located just upstream of the control surface hingeline and operated at a blowing ratio of 1 and non-dimensional frequency of 48. Detailed flowfield measurements over the control surface were conducted, where the airfoil's sweep angle and the control surface deflection angle were fixed at 20°. Focus was placed on the local and global flowfields as spanwise actuator spacing was varied. Moreover, surface pressure measurement for several sweep angles, control surface deflection angles, and angles of attack were also performed. Actuation resulted in an overall separation reduction and a dependence of local flowfield details (i.e. separation severity, spanwise flow magnitude, flow structures, and jet trajectory) on spanwise jet spacing. The Boeing Company.

DIVERGENT HORIZONTAL SUB-SURFACE FLOWS WITHIN ACTIVE REGION 11158

Energy Technology Data Exchange (ETDEWEB)

Jain, Kiran; Tripathy, S. C.; Hill, F., E-mail: kjain@nso.edu, E-mail: stripathy@nso.edu, E-mail: fhill@nso.edu [National Solar Observatory, 950 N Cherry Avenue, Tucson, AZ 85719 (United States)

2015-07-20

We measure the horizontal subsurface flow in a fast emerging active region (AR; NOAA 11158) using the ring-diagram technique and the Helioseismic and Magnetic Imager high spatial resolution Dopplergrams. This AR had a complex magnetic structure and displayed significant changes in morphology during its disk passage. Over a period of six days from 2011 February 11 to 16, the temporal variation in the magnitude of the total velocity is found to follow the trend of magnetic field strength. We further analyze regions of individual magnetic polarity within AR 11158 and find that the horizontal velocity components in these sub-regions have significant variation with time and depth. The leading and trailing polarity regions move faster than the mixed-polarity region. Furthermore, both zonal and meridional components have opposite signs for trailing and leading polarity regions at all depths showing divergent flows within the AR. We also find a sharp decrease in the magnitude of total horizontal velocity in deeper layers around major flares. It is suggested that the re-organization of magnetic fields during flares, combined with the sunspot rotation, decreases the magnitude of horizontal flows or that the flow kinetic energy has been converted into the energy released by flares. After the decline in flare activity and sunspot rotation, the flows tend to follow the pattern of magnetic activity. We also observe less variation in the velocity components near the surface but these tend to increase with depth, further demonstrating that the deeper layers are more affected by the topology of ARs.

Flow and active mixing have a strong impact on bacterial growth dynamics in the proximal large intestine

Science.gov (United States)

Cremer, Jonas; Segota, Igor; Yang, Chih-Yu; Arnoldini, Markus; Groisman, Alex; Hwa, Terence

2016-11-01

More than half of fecal dry weight is bacterial mass with bacterial densities reaching up to 1012 cells per gram. Mostly, these bacteria grow in the proximal large intestine where lateral flow along the intestine is strong: flow can in principal lead to a washout of bacteria from the proximal large intestine. Active mixing by contractions of the intestinal wall together with bacterial growth might counteract such a washout and allow high bacterial densities to occur. As a step towards understanding bacterial growth in the presence of mixing and flow, we constructed an in-vitro setup where controlled wall-deformations of a channel emulate contractions. We investigate growth along the channel under a steady nutrient inflow. Depending on mixing and flow, we observe varying spatial gradients in bacterial density along the channel. Active mixing by deformations of the channel wall is shown to be crucial in maintaining a steady-state bacterial population in the presence of flow. The growth-dynamics is quantitatively captured by a simple mathematical model, with the effect of mixing described by an effective diffusion term. Based on this model, we discuss bacterial growth dynamics in the human large intestine using flow- and mixing-behavior having been observed for humans.

Polyoxometalate active charge-transfer material for mediated redox flow battery

Energy Technology Data Exchange (ETDEWEB)

Anderson, Travis Mark; Hudak, Nicholas; Staiger, Chad; Pratt, Harry

2017-01-17

Redox flow batteries including a half-cell electrode chamber coupled to a current collecting electrode are disclosed herein. In a general embodiment, a separator is coupled to the half-cell electrode chamber. The half-cell electrode chamber comprises a first redox-active mediator and a second redox-active mediator. The first redox-active mediator and the second redox-active mediator are circulated through the half-cell electrode chamber into an external container. The container includes an active charge-transfer material. The active charge-transfer material has a redox potential between a redox potential of the first redox-active mediator and a redox potential of the second redox-active mediator. The active charge-transfer material is a polyoxometalate or derivative thereof. The redox flow battery may be particularly useful in energy storage solutions for renewable energy sources and for providing sustained power to an electrical grid.

TRPV4 activation mediates flow-induced nitric oxide production in the rat thick ascending limb

Science.gov (United States)

Garvin, Jeffrey L.

2014-01-01

Nitric oxide (NO) regulates renal function. Luminal flow stimulates NO production in the thick ascending limb (TAL). Transient receptor potential vanilloid 4 (TRPV4) is a mechano-sensitive channel activated by luminal flow in different types of cells. We hypothesized that TRPV4 mediates flow-induced NO production in the rat TAL. We measured NO production in isolated, perfused rat TALs using the fluorescent dye DAF FM. Increasing luminal flow from 0 to 20 nl/min stimulated NO from 8 ± 3 to 45 ± 12 arbitrary units (AU)/min (n = 5; P < 0.05). The TRPV4 antagonists, ruthenium red (15 μmol/l) and RN 1734 (10 μmol/l), blocked flow-induced NO production. Also, luminal flow did not increase NO production in the absence of extracellular calcium. We also studied the effect of luminal flow on NO production in TALs transduced with a TRPV4shRNA. In nontransduced TALs luminal flow increased NO production by 47 ± 17 AU/min (P < 0.05; n = 5). Similar to nontransduced TALs, luminal flow increased NO production by 39 ± 11 AU/min (P < 0.03; n = 5) in TALs transduced with a control negative sequence-shRNA while in TRPV4shRNA-transduced TALs, luminal flow did not increase NO production (Δ10 ± 15 AU/min; n = 5). We then tested the effect of two different TRPV4 agonists on NO production in the absence of luminal flow. 4α-Phorbol 12,13-didecanoate (1 μmol/l) enhanced NO production by 60 ± 11 AU/min (P < 0.002; n = 7) and GSK1016790A (10 ηmol/l) increased NO production by 52 ± 15 AU/min (P < 0.03; n = 5). GSK1016790A (10 ηmol/l) did not stimulate NO production in TRPV4shRNA-transduced TALs. We conclude that activation of TRPV4 channels mediates flow-induced NO production in the rat TAL. PMID:24966090

Performance Evaluation, Emulation, and Control of Cross-Flow Hydrokinetic Turbines

Science.gov (United States)

Cavagnaro, Robert J.

Cross-flow hydrokinetic turbines are a promising option for effectively harvesting energy from fast-flowing streams or currents. This work describes the dynamics of such turbines, analyzes techniques used to scale turbine properties for prototyping, determines and demonstrates the limits of stability for cross-flow rotors, and discusses means and objectives of turbine control. Novel control strategies are under development to utilize low-speed operation (slower than at maximum power point) as a means of shedding power under rated conditions. However, operation in this regime may be unstable. An experiment designed to characterize the stability of a laboratory-scale cross-flow turbine operating near a critically low speed yields evidence that system stall (complete loss of ability to rotate) occurs due, in part, to interactions with turbulent decreases in flow speed. The turbine is capable of maintaining 'stable' operation at critical speed for short duration (typically less than 10 s), as described by exponential decay. The presence of accelerated 'bypass' flow around the rotor and decelerated 'induction' region directly upstream of the rotor, both predicted by linear momentum theory, are observed and quantified with particle image velocimetry (PIV) measurements conducted upstream of the turbine. Additionally, general agreement is seen between PIV inflow measurements and those obtained by an advection-corrected acoustic Doppler velocimeter (ADV) further upstream. Performance of a turbine at small (prototype) geometric scale may be prone to undesirable effects due to operation at low Reynolds number and in the presence of high channel blockage. Therefore, testing at larger scale, in open water is desirable. A cross-flow hydrokinetic turbine with a projected area (product of blade span and rotor diameter) of 0.7 m2 is evaluated in open-water tow trials at three inflow speeds ranging from 1.0 m/s to 2.1 m/s. Measurements of the inflow velocity, the rotor mechanical

Synthetic Jets Flow Control on a vertical stabilizer

Science.gov (United States)

Rathay, Nicholas; Boucher, Matthew; Amitay, Michael

2011-11-01

The vertical stabilizer on most commercial transport aircraft is much larger than required for stability and control. The tail is significantly oversized in order to maintain controllability in the event of asymmetric engine failure and meet flying qualities requirements related to dynamic motion. Using aerodynamic flow control techniques, it may be possible to reduce the size of the tail while maintaining similar control authority during inclement flight conditions. Reducing the size of the tail decreases the weight and the drag of the airplane, which results in considerable savings in fuel costs. In this work, it is shown that synthetic jet (zero-net-mass-flux) actuators are capable of reattaching the separated flow on the rudder and augmenting the performance of the stabilizer. Experiments were conducted in an open-return wind tunnel on a 1/25th scale model of a vertical stabilizer and a partial fuselage section. The surface pressure, aerodynamic loads and data acquired with a Stereo PIV system were used to investigate the effectiveness of this technology as well as provide a more detailed analysis of the flowfield and showed that the synthetic jets are capable of augmenting the side-force by up to 20%.

RETROFITTING CONTROL FACILITIES FOR WET-WEATHER FLOW TREATMENT

Science.gov (United States)

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

Suboptimal RED Feedback Control for Buffered TCP Flow Dynamics in Computer Network

Directory of Open Access Journals (Sweden)

N. U. Ahmed

2007-01-01

Full Text Available We present an improved dynamic system that simulates the behavior of TCP flows and active queue management (AQM system. This system can be modeled by a set of stochastic differential equations driven by a doubly stochastic point process with intensities being the controls. The feedback laws proposed monitor the status of buffers and multiplexor of the router, detect incipient congestion by sending warning signals to the sources. The simulation results show that the optimal feedback control law from the class of linear as well as quadratic polynomials can improve the system performance significantly in terms of maximizing the link utilization, minimizing congestion, packet losses, as well as global synchronization. The optimization process used is based on random recursive search technique known as RRS.

Participative planning and information flow within management control

Directory of Open Access Journals (Sweden)

Tomasz Dyczkowski

2016-09-01

Full Text Available The paper examines the relationships between two different approaches to planning processes (participa- tive and non-participative and information flows within management control in companies. It augments the existing theoretical and empirical research by coupling management control and management infor- mation with participative planning, not only in operational but also in the strategic perspective. The re- sults presented in the paper stem from two consecutive studies, conducted between November 2010 and January 2012 and between November 2013 and January 2014. The studies comprised 397 and 179 Polish companies respectively. The authors formulated two hypotheses linking participative planning with upward and downward management information flows. The paper employed a quantitative approach, using the Spearman rank correlation analysis and hierarchical clustering using the Ward method, which enabled comparative analyses both in reference to various groups of companies included in particular research samples and over time. The results obtained showed the positive influence of participative plan- ning both on upward and downward information flows in enterprises. In particular, participative planning reduced information imbalances between top (the management and lower (employees of functional departments tiers in organisation structures.

Measurement and control systems for an imaging electromagnetic flow metre.

Science.gov (United States)

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

2014-03-01

Electromagnetic flow metres based on the principles of Faraday's laws of induction have been used successfully in many industries. The conventional electromagnetic flow metre can measure the mean liquid velocity in axisymmetric single phase flows. However, in order to achieve velocity profile measurements in single phase flows with non-uniform velocity profiles, a novel imaging electromagnetic flow metre (IEF) has been developed which is described in this paper. The novel electromagnetic flow metre which is based on the 'weight value' theory to reconstruct velocity profiles is interfaced with a 'Microrobotics VM1' microcontroller as a stand-alone unit. The work undertaken in the paper demonstrates that an imaging electromagnetic flow metre for liquid velocity profile measurement is an instrument that is highly suited for control via a microcontroller. © 2013 ISA Published by ISA All rights reserved.

CFD Simulations of a Finned Projectile with Microflaps for Flow Control

Directory of Open Access Journals (Sweden)

Jubaraj Sahu

2017-01-01

Full Text Available This research describes a computational study undertaken to determine the effect of a flow control mechanism and its associated aerodynamics for a finned projectile. The flow control system consists of small microflaps located between the rear fins of the projectile. These small microflaps alter the flow field in the aft finned region of the projectile, create asymmetric pressure distributions, and thus produce aerodynamic control forces and moments. A number of different geometric parameters, microflap locations, and the number of microflaps were varied in an attempt to maximize the control authority generated by the flaps. Steady-state Navier-Stokes computations were performed to obtain the control aerodynamic forces and moments associated with the microflaps. These results were used to optimize the control authority at a supersonic speed, M=2.5. Computed results showed not only the microflaps to be effective at this speed, but also configurations with 6 and 8 microflaps were found to generate 25%–50% more control force than a baseline 4-flap configuration. These results led to a new optimized 8-flap configuration that was further investigated for a range of Mach numbers from M=0.8 to 5.0 and was found to be a viable configuration effective in providing control at all of these speeds.

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 m......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...... as well as when parameter uncertainties and noise are present. The proposed controller lowers the grinding power consumption while in most cases exhibiting superior performance in comparison with the PID controller....

Development of linear flow rate control system for eccentric butter-fly valve

International Nuclear Information System (INIS)

Kwak, K. K.; Cho, S. W.; Park, J. S.; Cho, J. H.; Song, I. T.; Kim, J. G.; Kwon, S. J.; Kim, I. J.; Park, W. K.

1999-12-01

Butter-fly valves are advantageous over gate, globe, plug, and ball valves in a variety of installations, particularly in the large sizes. The purpose of this project development of linear flow rate control system for eccentric butter-fly valve (intelligent butter-fly valve system). The intelligent butter-fly valve system consist of a valve body, micro controller. The micro controller consist of torque control system, pressure censor, worm and worm gear and communication line etc. The characteristics of intelligent butter-fly valve system as follows: Linear flow rate control function. Digital remote control function. guard function. Self-checking function. (author)

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...

Effect of strict metabolic control on regulation of subcutaneous blood flow in insulin-dependent diabetic patients

DEFF Research Database (Denmark)

Kastrup, J; Mathiesen, E R; Saurbrey, Nina

1987-01-01

washout technique. Mean arterial blood pressure was reduced by a maximum of 23 mmHg by elevating the limb above heart level and elevated to a maximum of 65 mmHg by head-up tilt; in the latter position venous pressure was kept constantly low by activation of the leg muscle vein pump (heel raising......The effect of 10 weeks of improved metabolic control on the impaired autoregulation of the subcutaneous blood flow was studied at the level of the lateral malleolus in eight long-term insulin-dependent diabetic patients with clinical microangiopathy. Blood flow was measured by the local 133-Xenon......). Improved metabolic control was achieved using either continuous subcutaneous insulin infusion or multiple insulin injections. The blood glucose concentration declined from (median) 12.7 to 6.8 mmol/l and the HbA1C level from 10.1 to 7.5% during strict metabolic control (p less than 0.01 and p less than 0...

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......An approach to modelling unsteady compressible flow that is primarily one dimensional is presented. The approach was developed for creating distributed models of machines with reciprocating pistons but it is not limited to this application. The approach is based on the integral form of the unsteady...... 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...

Model-based Fuel Flow Control for Fossil-fired Power Plants

DEFF Research Database (Denmark)

Niemczyk, Piotr

2010-01-01

-fired power plants represent the largest reserve of such controllable power sources in several countries. However, their production take-up rates are limited, mainly due to poor fuel flow control. The thesis presents analysis of difficulties and potential improvements in the control of the coal grinding...

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.

Multi-fluid modelling of pulsed discharges for flow control applications

Science.gov (United States)

Poggie, J.

2015-02-01

Experimental evidence suggests that short-pulse dielectric barrier discharge actuators are effective for speeds corresponding to take-off and approach of large aircraft, and thus are a fruitful direction for flow control technology development. Large-eddy simulations have reproduced some of the main fluid dynamic effects. The plasma models used in such simulations are semi-empirical, however, and need to be tuned for each flowfield under consideration. In this paper, the discharge physics is examined in more detail with multi-fluid modelling, comparing a five-moment model (continuity, momentum, and energy equations) to a two-moment model (continuity and energy equations). A steady-state, one-dimensional discharge was considered first, and the five-moment model was found to predict significantly lower ionisation rates and number densities than the two-moment model. A two-dimensional, transient discharge problem with an elliptical cathode was studied next. Relative to the two-moment model, the five-moment model predicted a slower response to the activation of the cathode, and lower electron velocities and temperatures as the simulation approached steady-state. The primary reason for the differences in the predictions of the two models can be attributed to the effects of particle inertia, particularly electron inertia in the cathode layer. The computational cost of the five-moment model is only about twice that of the simpler variant, suggesting that it may be feasible to use the more sophisticated model in practical calculations for flow control actuator design.

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.

Flow control and routing techniques for integrated voice and data networks

Science.gov (United States)

Ibe, O. C.

1981-10-01

We consider a model of integrated voice and data networks. In this model the network flow problem is formulated as a convex optimization problem. The objective function comprises two types of cost functions: the congestion cost functions, which limit the average input traffic to values compatible with the network conditions; and the rate limitation cost functions, which ensure that all conversations are fairly treated. A joint flow control and routing algorithm is constructed which determines the routes for each conversation, and effects flow control by setting voice packet lengths and data input rates in a manner that achieves optimal tradeoff between each user's satisfaction and the cost of network congestion. An additional congestion control protocol is specified which could be used in conjunction with the algorithm to make the latter respond more dynamically to network congestion.

NADPH oxidase 4-derived superoxide mediates flow-stimulated NKCC2 activity in thick ascending limbs.

Science.gov (United States)

Saez, Fara; Hong, Nancy J; Garvin, Jeffrey L

2018-05-01

Luminal flow augments Na + reabsorption in the thick ascending limb more than can be explained by increased ion delivery. This segment reabsorbs 30% of the filtered load of Na + , playing a key role in its homeostasis. Whether flow elevations enhance Na + -K + -2Cl - cotransporter (NKCC2) activity and the second messenger involved are unknown. We hypothesized that raising luminal flow augments NKCC2 activity by enhancing superoxide ([Formula: see text]) production by NADPH oxidase 4 (NOX4). NKCC2 activity was measured in thick ascending limbs perfused at either 5 or 20 nl/min with and without inhibitors of [Formula: see text] production. Raising luminal flow from 5 to 20 nl/min enhanced NKCC2 activity from 4.8 ± 0.9 to 6.3 ± 1.2 arbitrary fluorescent units (AFU)/s. Maintaining flow at 5 nl/min did not alter NKCC2 activity. The superoxide dismutase mimetic manganese (III) tetrakis (4-benzoic acid) porphyrin chloride blunted NKCC2 activity from 3.5 ± 0.4 to 2.5 ± 0.2 AFU/s when flow was 20 nl/min but not 5 nl/min. When flow was 20 nl/min, NKCC2 activity showed no change with time. The selective NOX1/4 inhibitor GKT-137831 blunted NKCC2 activity when thick ascending limbs were perfused at 20 nl/min from 7.2 ± 1.1 to 4.5 ± 0.8 AFU/s but not at 5 nl/min. The inhibitor also prevented luminal flow from elevating [Formula: see text] production. Allopurinol, a xanthine oxidase inhibitor, had no effect on NKCC2 activity when flow was 20 nl/min. Tetanus toxin prevents flow-induced stimulation of NKCC2 activity. We conclude that elevations in luminal flow enhance NaCl reabsorption in thick ascending limbs by stimulating NKCC2 via NOX4 activation and increased [Formula: see text]. NKCC2 activation is primarily the result of insertion of new transporters in the membrane.

Device for passive flow control around vertical axis marine turbine

Science.gov (United States)

Coşoiu, C. I.; Georgescu, A. M.; Degeratu, M.; Haşegan, L.; Hlevca, D.

2012-11-01

The power supplied by a turbine with the rotor placed in a free stream flow may be increased by augmenting the velocity in the rotor area. The energy of the free flow is dispersed and it may be concentrated by placing a profiled structure around the bare turbine in order to concentrate more energy in the rotor zone. At the Aerodynamic and Wind Engineering Laboratory (LAIV) of the Technical University of Civil Engineering of Bucharest (UTCB) it was developed a concentrating housing to be used for hydro or aeolian horizontal axis wind turbines, in order to increase the available energy in the active section of turbine rotor. The shape of the concentrating housing results by superposing several aero/hydro dynamic effects, the most important being the one generated by the passive flow control devices that were included in the housing structure. Those concentrating housings may be also adapted for hydro or aeolian turbines with vertical axis. The present paper details the numerical research effectuated at the LAIV to determine the performances of a vertical axis marine turbine equipped with such a concentrating device, in order to increase the energy quantity extracted from the main flow. The turbine is a Darrieus type one with three vertical straight blades, symmetric with respect to the axis of rotation, generated using a NACA4518 airfoil. The global performances of the turbine equipped with the concentrating housing were compared to the same characteristics of the bare turbine. In order to validate the numerical approach used in this paper, test cases from the literature resulting from experimental and numerical simulations for similar situations, were used.

Device for passive flow control around vertical axis marine turbine

International Nuclear Information System (INIS)

Coşoiu, C I; Georgescu, A M; Degeratu, M; Haşegan, L; Hlevca, D

2012-01-01

The power supplied by a turbine with the rotor placed in a free stream flow may be increased by augmenting the velocity in the rotor area. The energy of the free flow is dispersed and it may be concentrated by placing a profiled structure around the bare turbine in order to concentrate more energy in the rotor zone. At the Aerodynamic and Wind Engineering Laboratory (LAIV) of the Technical University of Civil Engineering of Bucharest (UTCB) it was developed a concentrating housing to be used for hydro or aeolian horizontal axis wind turbines, in order to increase the available energy in the active section of turbine rotor. The shape of the concentrating housing results by superposing several aero/hydro dynamic effects, the most important being the one generated by the passive flow control devices that were included in the housing structure. Those concentrating housings may be also adapted for hydro or aeolian turbines with vertical axis. The present paper details the numerical research effectuated at the LAIV to determine the performances of a vertical axis marine turbine equipped with such a concentrating device, in order to increase the energy quantity extracted from the main flow. The turbine is a Darrieus type one with three vertical straight blades, symmetric with respect to the axis of rotation, generated using a NACA4518 airfoil. The global performances of the turbine equipped with the concentrating housing were compared to the same characteristics of the bare turbine. In order to validate the numerical approach used in this paper, test cases from the literature resulting from experimental and numerical simulations for similar situations, were used.

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.

A flow-control mechanism for distributed systems

Science.gov (United States)

Maitan, J.

1991-01-01

A new approach to the rate-based flow control in store-and-forward networks is evaluated. Existing methods display oscillations in the presence of transport delays. The proposed scheme is based on the explicit use of an embedded dynamic model of a store-and-forward buffer in a controller's feedback loop. It is shown that the use of the model eliminates the oscillations caused by the transport delays. The paper presents simulation examples and assesses the applicability of the scheme in the new generation of high-speed photonic networks where transport delays must be considered.

Numerical Studies of a Supersonic Fluidic Diverter Actuator for Flow Control

Science.gov (United States)

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

2010-01-01

The analysis of the internal flow structure and performance of a specific fluidic diverter actuator, previously studied by time-dependent numerical computations for subsonic flow, is extended to include operation with supersonic actuator exit velocities. The understanding will aid in the development of fluidic diverters with minimum pressure losses and advanced designs of flow control actuators. The self-induced oscillatory behavior of the flow is successfully predicted and the calculated oscillation frequencies with respect to flow rate have excellent agreement with our experimental measurements. The oscillation frequency increases with Mach number, but its dependence on flow rate changes from subsonic to transonic to supersonic regimes. The delay time for the initiation of oscillations depends on the flow rate and the acoustic speed in the gaseous medium for subsonic flow, but is unaffected by the flow rate for supersonic conditions

Enhancement of Arterial Pressure Pulsatility by Controlling Continuous-Flow Left Ventricular Assist Device Flow Rate in Mock Circulatory System.

Science.gov (United States)

Bozkurt, Selim; van de Vosse, Frans N; Rutten, Marcel C M

Continuous-flow left ventricular assist devices (CF-LVADs) generally operate at a constant speed, which reduces pulsatility in the arteries and may lead to complications such as functional changes in the vascular system, gastrointestinal bleeding, or both. The purpose of this study is to increase the arterial pulse pressure and pulsatility by controlling the CF-LVAD flow rate. A MicroMed DeBakey pump was used as the CF-LVAD. A model simulating the flow rate through the aortic valve was used as a reference model to drive the pump. A mock circulation containing two synchronized servomotor-operated piston pumps acting as left and right ventricles was used as a circulatory system. Proportional-integral control was used as the control method. First, the CF-LVAD was operated at a constant speed. With pulsatile-speed CF-LVAD assistance, the pump was driven such that the same mean pump output was generated. Continuous and pulsatile-speed CF-LVAD assistance provided the same mean arterial pressure and flow rate, while the index of pulsatility increased significantly for both arterial pressure and pump flow rate signals under pulsatile speed pump support. This study shows the possibility of improving the pulsatility of CF-LVAD support by regulating pump speed over a cardiac cycle without reducing the overall level of support.

Movable shark scales act as a passive dynamic micro-roughness to control flow separation

International Nuclear Information System (INIS)

Lang, Amy W; Bradshaw, Michael T; Smith, Jonathon A; Wheelus, Jennifer N; Motta, Philip J; Habegger, Maria L; Hueter, Robert E

2014-01-01

Shark scales on fast-swimming sharks have been shown to be movable to angles in excess of 50°, and we hypothesize that this characteristic gives this shark skin a preferred flow direction. During the onset of separation, flow reversal is initiated close to the surface. However, the movable scales would be actuated by the reversed flow thereby causing a greater resistance to any further flow reversal and this mechanism would disrupt the process leading to eventual flow separation. Here we report for the first time experimental evidence of the separation control capability of real shark skin through water tunnel testing. Using skin samples from a shortfin mako Isurus oxyrinchus, we tested a pectoral fin and flank skin attached to a NACA 4412 hydrofoil and separation control was observed in the presence of movable shark scales under certain conditions in both cases. We hypothesize that the scales provide a passive, flow-actuated mechanism acting as a dynamic micro-roughness to control flow separation. (paper)

Calculated viscosity-distance dependence for some actively flowing lavas

International Nuclear Information System (INIS)

Pieri, D.

1987-01-01

The importance of viscosity as a gauge of the various energy and momentum dissipation regimes of lava flows has been realized for a long time. Nevertheless, despite its central role in lava dynamics and kinematics, it remains among the most difficult of flow physical properties to measure in situ during an eruption. Attempts at reconstructing the actual emplacement viscosities of lava flows from their solidified topographic form are difficult. Where data are available on the position of an advancing flow front as a function of time, it is possible to calculate the effective viscosity of the front as a function of distance from the vent, under the assumptions of a steady state regime. As an application and test of an equation given, relevant parameters from five recent flows on Mauna Loa and Kilauea were utilized to infer the dynamic structure of their aggregate flow front viscosity as they advanced, up to cessation. The observed form of the viscosity-distance relation for the five active Hawaiian flows examined appears to be exponential, with a rapid increase just before the flows stopped as one would expect

Effect Of Steel Flow Control Devices On Flow And Temperature Field In The Tundish Of Continuous Casting Machine

Directory of Open Access Journals (Sweden)

Sowa L.

2015-06-01

Full Text Available The mathematical model and numerical simulations of the liquid steel flow in a tundish are presented in this paper. The problem was treated as a complex and solved by the finite element method. One takes into consideration in the mathematical model the changes of thermophysical parameters depending on the temperature. The single-strand tundish is used to casting slabs. The internal work space of the tundish was modified by flow control devices. The first device was a pour pad situated in the pouring tundish zone. The second device was a dam. The third device was a baffle with three holes. The dam and baffle were placed in the tundish at different positions depending on the variant. The main purpose of using these was to put barriers in the steel flow path as well as give directional metal flow upwards which facilitated inclusion floatation. The interaction of flow control devices on hydrodynamic conditions was received from numerical simulations. As a result of the computations carried out, the liquid steel flow and steel temperature fields were obtained. The influences of the tundish modifications on the velocity fields in liquid phase of the steel were estimated, because these have essential an influence on high-quality of a continuous steel cast slab.

Field Effect Flow Control in a Polymer T-Intersection Microfluidic Network

Science.gov (United States)

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

2003-01-01

We present a study of induced pressure pumping in a polymer microchannel due to differential electroosmotic flow @OF) rates via field-effect flow control (FEFC). The experimental results demonstrate that the induced pressure pumping is dependent on the distance of the FEFC gate from the cathodic gate. A proposed flow model based on a linearly-decaying zeta potential profile is found to successfully predict experimental trends.

Evaluation of the FAA Advanced Flow Control Procedures.

Science.gov (United States)

1972-01-01

The report is an evaluation of the present FAA Advanced Flow Control Procedures (AFCP), based on data gathered from its implementation on February 5, 1971 and on a fast-time digital simulation of traffic feeding into the NY airports on that day. The ...

Automatic coolant flow control device for a nuclear reactor assembly

Science.gov (United States)

Hutter, Ernest

1986-01-01

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

Steady flow torques in a servo motor operated rotary directional control valve

International Nuclear Information System (INIS)

Wang, He; Gong, Guofang; Zhou, Hongbin; Wang, Wei

2016-01-01

Highlights: • A novel servo motor operated rotary directional control valve is proposed. • Steady flow torque is a crucial issue that affects rotary valve performance. • Steady flow torque is analyzed on the aspects of theory, simulation and experiment. • Change law of the steady flow torque with spool rotation angle is explored. • Effect of pressure drop and flow rate on the steady flow torque is studied. - Abstract: In this paper, a servo motor operated rotary directional control valve is proposed, and a systematic analysis of steady flow torques in this valve is provided by theoretical calculation, CFD simulation and experimental test. In the analysis, spool rotation angle corresponding to the maximum orifice opening is tagged as 0°. Over a complete change cycle of the orifice, the range of spool rotation angle is symmetric about 0°. The results show that the direction of steady flow torques in this valve is always the direction of orifice closing. The steady flow torques serve as resistances to the spool rotation when the orifice opening increases, while impetuses to the spool rotation when the orifice opening decreases. At a certain pressure drop or flow rate, steady flow torques are approximately equal and opposite when at spool rotation angles which are symmetric about 0°. When the spool rotates from 0°, at a certain pressure drop, their values increase first then decrease with the spool rotation and reach their maximum values at an angle corresponding to about 1/2 of the maximum orifice opening, and at a certain flow rate, their values increase with the spool rotation. The steady flow torques in this valve are the sums of those in the meter-in and meter-out valve chambers. At a certain spool rotation angle, steady flow torques in the meter-in and meter-out valve chambers are approximately proportional to the pressure drop and the second power of the flow rate through the orifice. Theoretical calculation and CFD simulation can be validated by

CRITICAL CONTROL POINTS ON THE TECHNOLOGICAL FLOW OF PANIFICATION

Directory of Open Access Journals (Sweden)

Gigel PARASCHIV

2013-05-01

Full Text Available Bread and panification products are intended for direct human consumption and underlying nutritional pyramid, it can affect the consumers health in case of biological, chemical or physical contamination, immediate or delayed, by noxious accumulation in the human organism. Only by rigorous compliance of the production rules throughout the technological process can ensure the quality and food safety of these products. If the risk can be prevented, eliminated or reduce to an acceptable level, as a result of a control actions made at that stage, it is considered a Critical Control Point (CCP. There can be checkpoints where it can exert a control action. Thus, the checkpoint is represented by any stage in which the risk factors, biological, chemical or physical, can be controlled in order to prevent, disrupt or reduce them to an acceptable level. This paper is referring to the control points on the technological flow of the bread fabrication, in all phases of this technological flow, laying stress on that points (or phases which can affect security and food safety, through the influence of parameters of any kind on the quality of finished products.

AN ACTIVE FRACTURE MODEL FOR UNSATURATED FLOW AND TRANSPORT

International Nuclear Information System (INIS)

HUI-HAI LIU, GUDMUNDUR S. BODVARSSON AND CHRISTINE DOUGHTY

1999-01-01

Fracture/matrix (F/M) interaction is a key factor affecting flow and transport in unsaturated fractured rocks. In classic continuum approaches (Warren and Root, 1963), it is assumed that flow occurs through all the connected fractures and is uniformly distributed over the entire fracture area, which generally gives a relatively large F/M interaction. However, fractures seem to have limited interaction with the surrounding matrix at Yucca Mountain, Nevada, as suggested by geochemical nonequilibrium between the perched water (resulting mainly from fracture flow) and pore water in the rock matrix. Because of the importance of the F/M interaction and related issues, there is a critical need to develop new approaches to accurately consider the interaction reduction inferred from field data at the Yucca Mountain site. Motivated by this consideration, they have developed an active fracture model based on the hypothesis that not all connected fractures actively conduct water in unsaturated fractured rocks

Development of the flow control irradiation facility for JOYO

International Nuclear Information System (INIS)

Soroi, Masatoshi; Miyakawa, Shun-ichi

1998-05-01

This report describes the present situation and problems with the development of the flow control irradiation facility (FLORA). The purpose of FLORA is to run the cladding breach (RTCB) irradiation test under loss of flow conditions in the experimental fast reactor 'JOYO'. FLORA is a facility like FPTF (Fuel Performance Test Facility) plus BFTF (Breached Fuel Test Facility) in EBR-II, USA. The technical feature of FLORA is its annular linear induction pump (A-LIP), which was developed in response to a need identified through the experiences in the mechanical flow control of FPTF. We have already designed the basic system facility of FLORA for the JOYO MK-II core. However, to put FLORA to practical use in the future, we have to confirm the stability of the JOYO MK-III core condition, solve problems and improve the design. We are going to freeze and review the FLORA project, taking into consideration the fuel development situation and the research project of JOYO MK-III core. (J.P.N.)

Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines

International Nuclear Information System (INIS)

Zheng Ming; Reader, Graham T.

2004-01-01

The use of three way catalytic converters in stoichiometric burn reciprocating internal combustion engine systems has proved to be an effective and efficient method for reducing the level of criteria pollutants. However, such passive systems have not been as successful in emission amelioration when combined with lean burn engines. This is because of the thermochemical nature of the exhaust gases generated by such engines. The high content of exhaust oxygen largely negates the effectiveness of three way catalytic converters, and the comparatively low temperature of the combusted gases means that supplemental energy has to be added to these gases to enable the converter to function correctly. This requirement severely reduces the energy efficiency of conventional passive aftertreatment systems. However, initial empirical studies have indicated that a possible means of improving the performance of aftertreatment devices when used with lean burn engine systems is to use active flow control of the exhaust gases. These results are reported in this paper. This concept has been further investigated by developing an energy efficiency analysis that enables the effects on aftertreatment performance of different gas flow rates, flow reversal frequencies and monolith solid properties to be investigated. Simulation results indicate that through active thermal management, the supplemental energy consumption can be drastically reduced

A stochastic programming approach to manufacturing flow control

OpenAIRE

Haurie, Alain; Moresino, Francesco

2012-01-01

This paper proposes and tests an approximation of the solution of a class of piecewise deterministic control problems, typically used in the modeling of manufacturing flow processes. This approximation uses a stochastic programming approach on a suitably discretized and sampled system. The method proceeds through two stages: (i) the Hamilton-Jacobi-Bellman (HJB) dynamic programming equations for the finite horizon continuous time stochastic control problem are discretized over a set of sample...

History of Suction-Type Laminar-Flow Control with Emphasis on Flight Resrearch: Monographs in Aerospace History Number 13