WorldWideScience

Sample records for wind flow lines

  1. Emission-line widths and stellar-wind flows in T Tauri stars

    International Nuclear Information System (INIS)

    Sa, C.; Lago, M.T.V.T.

    1986-01-01

    Spectra are reported of T Tauri stars taken with the IPCS on the Isaac Newton Telescope at the Observatorio del Roque de los Muchachos at a dispersion of l7 A mm -1 . These were taken in order to determine emission-line widths and hence flow velocities in the winds of these stars following the successful modelling of the wind from RU Lupi using such data. Line widths in RW Aur suggest a similar pattern to the wind flow as in RU Lupi with velocities rising in the inner chromosphere of the star and then entering a 'ballistic' zone. The wind from DFTau is also similar but velocities are generally much lower and the lines sharper. (author)

  2. Validation of the Actuator Line Model for Simulating Flows past Yawed Wind Turbine Rotors

    DEFF Research Database (Denmark)

    Shen, Wen Zhong; Zhu, Wei Jun; Yang, Hua

    2015-01-01

    The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of −2.3˚, wind speeds of 10, 15, 24 m/s and yaw angles of 15......˚, 30˚ and 45˚. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm......, a pitch angle of 3˚, a wind speed of 5 m/s and yaw angles of 10˚ and 30˚. The computed loads are compared to the loads measured from pressure measurement....

  3. Energy Absorption of Distribution Line Arresters due to Lightning Back Flow Current and Ground Potential Rise for Lightning Hit to Wind Turbine Generator System

    Science.gov (United States)

    Okamoto, Hiroshi; Sekioka, Shozo; Ebinuma, Yasumitsu; Yamamoto, Kazuo; Yasuda, Yoh; Funabashi, Toshihisa; Yokoyama, Shigeru

    In the coast of the Japan Sea which has many good places for wind turbine generator system, winter lightning occurs frequently. Many results of investigation have been reported not only damages of wind turbine generator system itself but also failures of distribution line arresters caused by part of the lightning current which flows into distribution lines when the customer's structure is struck by lightning. The lightning back flow current and ground potential rise are also important factors for a lightning protection design of distribution line arresters, which are connected to the wind turbine generator system struck by lightning. This paper describes simulation results of the energy absorption to estimate the lightning damages in the arresters considering the back flow current and the ground potential rise using the EMTP.

  4. Wind flow through shrouded wind turbines

    Science.gov (United States)

    2017-03-01

    velocity and model angle were varied . Additionally, static wall pressures and cross section flow were studied with the addition of a screen. The pressure...the geometry of a wind lens or flange on the shroud and a gradually diverging shape, proved to accelerate the flow through the duct. 14. SUBJECT...Tunnel velocity and model angle were varied . Additionally, static wall pressures and cross section flow were studied with the addition of a screen. The

  5. Blind test comparison of the performance and wake flow between two in-line wind turbines exposed to different turbulent inflow conditions

    Directory of Open Access Journals (Sweden)

    J. Bartl

    2017-02-01

    Full Text Available This is a summary of the results of the fourth blind test workshop that was held in Trondheim in October 2015. Herein, computational predictions on the performance of two in-line model wind turbines as well as the mean and turbulent wake flow are compared to experimental data measured at the wind tunnel of the Norwegian University of Science and Technology (NTNU. A detailed description of the model geometry, the wind tunnel boundary conditions and the test case specifications was published before the workshop. Expert groups within computational fluid dynamics (CFD were invited to submit predictions on wind turbine performance and wake flow without knowing the experimental results at the outset. The focus of this blind test comparison is to examine the model turbines' performance and wake development with nine rotor diameters downstream at three different turbulent inflow conditions. Aside from a spatially uniform inflow field of very low-turbulence intensity (TI = 0.23 % and high-turbulence intensity (TI = 10.0 %, the turbines are exposed to a grid-generated highly turbulent shear flow (TI = 10.1 %.Five different research groups contributed their predictions using a variety of simulation models, ranging from fully resolved Reynolds-averaged Navier–Stokes (RANS models to large eddy simulations (LESs. For the three inlet conditions, the power and the thrust force of the upstream turbine is predicted fairly well by most models, while the predictions of the downstream turbine's performance show a significantly higher scatter. Comparing the mean velocity profiles in the wake, most models approximate the mean velocity deficit level sufficiently well. However, larger variations between the models for higher downstream positions are observed. Prediction of the turbulence kinetic energy in the wake is observed to be very challenging. Both the LES model and the IDDES (improved delayed detached eddy simulation model, however

  6. Assessing the vegetation canopy influences on wind flow using wind ...

    Indian Academy of Sciences (India)

    The effectiveness of vegetation in reducing wind ... Wind erosion; roughness length; shear velocity ratio; shear stress ratio; roughness density; wind tunnel. J. Earth .... flow direction induced by its kinematic viscosity. An increase in shear stress causes a proportional increase in the height-dependent change in wind velocity.

  7. Simulation of wind turbine wakes using the actuator line technique

    Science.gov (United States)

    Sørensen, Jens N.; Mikkelsen, Robert F.; Henningson, Dan S.; Ivanell, Stefan; Sarmast, Sasan; Andersen, Søren J.

    2015-01-01

    The actuator line technique was introduced as a numerical tool to be employed in combination with large eddy simulations to enable the study of wakes and wake interaction in wind farms. The technique is today largely used for studying basic features of wakes as well as for making performance predictions of wind farms. In this paper, we give a short introduction to the wake problem and the actuator line methodology and present a study in which the technique is employed to determine the near-wake properties of wind turbines. The presented results include a comparison of experimental results of the wake characteristics of the flow around a three-bladed model wind turbine, the development of a simple analytical formula for determining the near-wake length behind a wind turbine and a detailed investigation of wake structures based on proper orthogonal decomposition analysis of numerically generated snapshots of the wake. PMID:25583862

  8. Simulation of wind turbine wakes using the actuator line technique

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming; Henningson, Dan S.

    2015-01-01

    The actuator line technique was introduced as a numerical tool to be employed in combination with large eddy simulations to enable the study of wakes and wake interaction in wind farms. The technique is today largely used for studying basic features of wakes as well as for making performance...... predictions of wind farms. In this paper, we give a short introduction to the wake problem and the actuator line methodology and present a study in which the technique is employed to determine the near-wake properties of wind turbines. The presented results include a comparison of experimental results...... of the wake characteristics of the flow around a three-bladed model wind turbine, the development of a simple analytical formula for determining the near-wake length behind a wind turbine and a detailed investigation of wake structures based on proper orthogonal decomposition analysis of numerically generated...

  9. Aeroacoustic Calculations of Wind Turbine Noise with the Actuator Line/ Navier-Stokes Technique

    DEFF Research Database (Denmark)

    Debertshäuser, Harald; Shen, Wen Zhong; Zhu, Wei Jun

    2016-01-01

    technique where the wind turbine flow is calculated by using the in-house actuator line/LES/Navier-Stokes technique and the acoustics is obtained by solving the acoustic perturbation equations. In the flow solver, the wind turbine blades are modelled by rotating lines with body forces determined according...

  10. Power-flow control and stability enhancement of four parallel-operated offshore wind farms using a line-commutated HVDC link

    DEFF Research Database (Denmark)

    Wang, Li; Wang, Kuo-Hua; Lee, Wei-Jen

    2010-01-01

    This paper presents an effective control scheme using a line-commutated high-voltage direct-current (HVDC) link with a designed rectifier current regulator (RCR) to simultaneously perform both power-fluctuation mitigation and damping improvement of four parallel-operated 80-MW offshore wind farms...... delivering generated power to a large utility grid. The proposed RCR of the HVDC link is designed by using modal control theory to contribute adequate damping to the studied four offshore wind farms under various wind speeds. A systematic analysis using a frequency-domain approach based on eigenvalue...... analysis and a time-domain scheme based on nonlinear model simulations is performed to demonstrate the effectiveness of the proposed control scheme. It can be concluded from the simulation results that the proposed HVDC link combined with the designed RCR can not only render adequate damping...

  11. Flow separation on wind turbines blades

    Science.gov (United States)

    Corten, G. P.

    2001-01-01

    In the year 2000, 15GW of wind power was installed throughout the world, producing 100PJ of energy annually. This contributes to the total electricity demand by only 0.2%. Both the installed power and the generated energy are increasing by 30% per year world-wide. If the airflow over wind turbine blades could be controlled fully, the generation efficiency and thus the energy production would increase by 9%. Power Control To avoid damage to wind turbines, they are cut out above 10 Beaufort (25 m/s) on the wind speed scale. A turbine could be designed in such a way that it converts as much power as possible in all wind speeds, but then it would have to be to heavy. The high costs of such a design would not be compensated by the extra production in high winds, since such winds are rare. Therefore turbines usually reach maximum power at a much lower wind speed: the rated wind speed, which occurs at about 6 Beaufort (12.5 m/s). Above this rated speed, the power intake is kept constant by a control mechanism. Two different mechanisms are commonly used. Active pitch control, where the blades pitch to vane if the turbine maximum is exceeded or, passive stall control, where the power control is an implicit property of the rotor. Stall Control The flow over airfoils is called "attached" when it flows over the surface from the leading edge to the trailing edge. However, when the angle of attack of the flow exceeds a certain critical angle, the flow does not reach the trailing edge, but leaves the surface at the separation line. Beyond this line the flow direction is reversed, i.e. it flows from the trailing edge backward to the separation line. A blade section extracts much less energy from the flow when it separates. This property is used for stall control. Stall controlled rotors always operate at a constant rotation speed. The angle of attack of the flow incident to the blades is determined by the blade speed and the wind speed. Since the latter is variable, it determines

  12. Wind Data Analysis and Wind Flow Simulation Over Large Areas

    Directory of Open Access Journals (Sweden)

    Terziev Angel

    2014-03-01

    Full Text Available Increasing the share of renewable energy sources is one of the core policies of the European Union. This is because of the fact that this energy is essential in reducing the greenhouse gas emissions and securing energy supplies. Currently, the share of wind energy from all renewable energy sources is relatively low. The choice of location for a certain wind farm installation strongly depends on the wind potential. Therefore the accurate assessment of wind potential is extremely important. In the present paper an analysis is made on the impact of significant possible parameters on the determination of wind energy potential for relatively large areas. In the analysis the type of measurements (short- and long-term on-site measurements, the type of instrumentation and the terrain roughness factor are considered. The study on the impact of turbulence on the wind flow distribution over complex terrain is presented, and it is based on the real on-site data collected by the meteorological tall towers installed in the northern part of Bulgaria. By means of CFD based software a wind map is developed for relatively large areas. Different turbulent models in numerical calculations were tested and recommendations for the usage of the specific models in flows modeling over complex terrains are presented. The role of each parameter in wind map development is made. Different approaches for determination of wind energy potential based on the preliminary developed wind map are presented.

  13. Simulation of wind turbine wakes using the actuator line technique.

    Science.gov (United States)

    Sørensen, Jens N; Mikkelsen, Robert F; Henningson, Dan S; Ivanell, Stefan; Sarmast, Sasan; Andersen, Søren J

    2015-02-28

    The actuator line technique was introduced as a numerical tool to be employed in combination with large eddy simulations to enable the study of wakes and wake interaction in wind farms. The technique is today largely used for studying basic features of wakes as well as for making performance predictions of wind farms. In this paper, we give a short introduction to the wake problem and the actuator line methodology and present a study in which the technique is employed to determine the near-wake properties of wind turbines. The presented results include a comparison of experimental results of the wake characteristics of the flow around a three-bladed model wind turbine, the development of a simple analytical formula for determining the near-wake length behind a wind turbine and a detailed investigation of wake structures based on proper orthogonal decomposition analysis of numerically generated snapshots of the wake. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  14. Wind flow around a church - Case study

    Science.gov (United States)

    Jamińska-Gadomska, Paulina; Lipecki, Tomasz; Podgórski, Jerzy

    2018-01-01

    The paper presents results of CFD analysis performed to check the influence of wind action on a bell tower of a church. The geometry of the structure is quite complex therefore it is very hard to calculate wind load basing only on codes recommendations. The modelled geometry contains whole structure of the church including the bell tower. Results presented in this paper are focused on co-called "Venturi-effect" represented by the flow around the bell tower. CFD simulations were performed for two inflow wind directions of opposite senses. This led to two cases of converging and diverging walls of the bell tower in relation to the wind flow direction. Such analysis was performed to check if the wind speed increases between the walls of the bell tower.

  15. Wake flow characteristics at high wind speed

    DEFF Research Database (Denmark)

    Aagaard Madsen, Helge; Larsen, Torben J.; Larsen, Gunner Chr.

    2016-01-01

    Wake flow characteristic at high wind speeds is the main subject of this paper. Although the wake losses decrease at high wind speeds it has been found in a recent study that for multiple wake inflow the increase in loading due to wake effects are substantial even at wind speeds well above rated...... power. In the present study we simulate the wake flow for a row of turbines with the wind aligned with the row using a simplified approach. The velocity deficit, being a function of the thrust coefficient, is simulated based on the BEM solution for wake expansion. An axis-symmetric boundary layer...... equation model (the same as implemented in the DWM model) is subsequently used to develop the deficit down to the next turbine, and then the approach is successively repeated. Simulation results for four different spacing’s in a row with eight turbines show that there are two major flow regimes...

  16. Wind Tunnel Modeling Of Wind Flow Over Complex Terrain

    Science.gov (United States)

    Banks, D.; Cochran, B.

    2010-12-01

    This presentation will describe the finding of an atmospheric boundary layer (ABL) wind tunnel study conducted as part of the Bolund Experiment. This experiment was sponsored by Risø DTU (National Laboratory for Sustainable Energy, Technical University of Denmark) during the fall of 2009 to enable a blind comparison of various air flow models in an attempt to validate their performance in predicting airflow over complex terrain. Bohlund hill sits 12 m above the water level at the end of a narrow isthmus. The island features a steep escarpment on one side, over which the airflow can be expected to separate. The island was equipped with several anemometer towers, and the approach flow over the water was well characterized. This study was one of only two only physical model studies included in the blind model comparison, the other being a water plume study. The remainder were computational fluid dynamics (CFD) simulations, including both RANS and LES. Physical modeling of air flow over topographical features has been used since the middle of the 20th century, and the methods required are well understood and well documented. Several books have been written describing how to properly perform ABL wind tunnel studies, including ASCE manual of engineering practice 67. Boundary layer wind tunnel tests are the only modelling method deemed acceptable in ASCE 7-10, the most recent edition of the American Society of Civil Engineers standard that provides wind loads for buildings and other structures for buildings codes across the US. Since the 1970’s, most tall structures undergo testing in a boundary layer wind tunnel to accurately determine the wind induced loading. When compared to CFD, the US EPA considers a properly executed wind tunnel study to be equivalent to a CFD model with infinitesimal grid resolution and near infinite memory. One key reason for this widespread acceptance is that properly executed ABL wind tunnel studies will accurately simulate flow separation

  17. Resonance Line Formation in Moving Gas Flows with High Porosity

    Science.gov (United States)

    Shulman, S. G.

    2017-06-01

    The formation of resonance lines in gas flows generated by interactions of circumstellar gas with a star's magnetosphere is examined. An effective method is proposed for calculating these lines when the magnetospheric wind is highly porous. The resonance sodium lines observed in the spectrum of UX Ori type star RZ Psc are modelled as an example. It is shown that the narrow absorptions observed in the short wavelength wings of these lines can be formed by scattering of the star's radiation in two gas jets that are semitransparent at the line frequencies when they cross the line of sight.

  18. Numerical simulations of flow fields through conventionally controlled wind turbines and wind farms

    International Nuclear Information System (INIS)

    Yilmaz, Ali Emre; Meyers, Johan

    2014-01-01

    In the current study, an Actuator-Line Model (ALM) is implemented in our in-house pseudo-spectral LES solver SP-WIND, including a turbine controller. Below rated wind speed, turbines are controlled by a standard-torque-controller aiming at maximum power extraction from the wind. Above rated wind speed, the extracted power is limited by a blade pitch controller which is based on a proportional-integral type control algorithm. This model is used to perform a series of single turbine and wind farm simulations using the NREL 5MW turbine. First of all, we focus on below-rated wind speed, and investigate the effect of the farm layout on the controller calibration curves. These calibration curves are expressed in terms of nondimensional torque and rotational speed, using the mean turbine-disk velocity as reference. We show that this normalization leads to calibration curves that are independent of wind speed, but the calibration curves do depend on the farm layout, in particular for tightly spaced farms. Compared to turbines in a lone-standing set-up, turbines in a farm experience a different wind distribution over the rotor due to the farm boundary-layer interaction. We demonstrate this for fully developed wind-farm boundary layers with aligned turbine arrangements at different spacings (5D, 7D, 9D). Further we also compare calibration curves obtained from full farm simulations with calibration curves that can be obtained at a much lower cost using a minimal flow unit

  19. Wind farm power optimization including flow variability

    DEFF Research Database (Denmark)

    Herp, Jürgen; Poulsen, Uffe Vestergaard; Greiner, Martin

    2015-01-01

    A model-based optimisation approach is used to investigate the potential gain of wind-farm power with a cooperative control strategy between the wind turbines. Based on the Jensen wake model with the Katic wake superposition rule, the potential gain for the Nysted offshore wind farm is calculated...... to be 1.4–5.4% for standard choices 0.4 ≥ k ≥ 0.25 of the wake expansion parameter. Wake model fits based on short time intervals of length 15sec ≤ T ≤ 10 min within three months of data reveal a strong wake flow variability, resulting in rather broad distributions for the wake expansion parameter. When...... an optimized wind-farm control strategy, derived from a fixed wake parameter, is facing this flow variability, the potential gain reduces to 0.3–0.5%. An omnipotent control strategy, which has real-time knowledge of the actual wake flow, would be able to increase the gain in wind-farm power to 4.9%....

  20. Prescribed wind shear modelling with the actuator line technique

    DEFF Research Database (Denmark)

    Mikkelsen, Robert Flemming; Sørensen, Jens Nørkær; Troldborg, Niels

    2007-01-01

    A method for prescribing arbitrary steady atmospheric wind shear profiles combined with CFD is presented. The method is furthermore combined with the actuator line technique governing the aerodynamic loads on a wind turbine. Computation are carried out on a wind turbine exposed to a representative...... steady atmospheric wind shear profile with and without wind direction changes up through the atmospheric boundary layer. Results show that the main impact on the turbine is captured by the model. Analysis of the wake behind the wind turbine, reveal the formation of a skewed wake geometry interacting...

  1. Base line studies North Sea wind farms

    NARCIS (Netherlands)

    Krijgsveld, K.L.; Lieshout, S.M.J.; Schekkerman, H.; Lensink, Rick; Poot, M.J.M.; Dirksen, S.

    2003-01-01

    The Dutch government has granted ‘Noordzeewind’ (Nuon Renewable Energy Projects and Shell Wind Energy) the possibility to build a wind farm consisting of 36 wind turbines off the coast of the Netherlands, near Egmond. This project serves to evaluate the economical, technical, ecological and social

  2. Wake Flow Simulation of a Vertical Axis Wind Turbine Under the Influence of Wind Shear

    Science.gov (United States)

    Mendoza, Victor; Goude, Anders

    2017-05-01

    The current trend of the wind energy industry aims for large scale turbines installed in wind farms. This brings a renewed interest in vertical axis wind turbines (VAWTs) since they have several advantages over the traditional Horizontal Axis Wind Tubines (HAWTs) for mitigating the new challenges. However, operating VAWTs are characterized by complex aerodynamics phenomena, presenting considerable challenges for modeling tools. An accurate and reliable simulation tool for predicting the interaction between the obtained wake of an operating VAWT and the flow in atmospheric open sites is fundamental for optimizing the design and location of wind energy facility projects. The present work studies the wake produced by a VAWT and how it is affected by the surface roughness of the terrain, without considering the effects of the ambient turbulence intensity. This study was carried out using an actuator line model (ALM), and it was implemented using the open-source CFD library OpenFOAM to solve the governing equations and to compute the resulting flow fields. An operational H-shaped VAWT model was tested, for which experimental activity has been performed at an open site north of Uppsala-Sweden. Different terrains with similar inflow velocities have been evaluated. Simulated velocity and vorticity of representative sections have been analyzed. Numerical results were validated using normal forces measurements, showing reasonable agreement.

  3. Two-Dimensional Rotorcraft Downwash Flow Field Measurements by Lidar-Based Wind Scanners with Agile Beam Steering

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Angelou, Nikolas; Hansen, Per

    2014-01-01

    for agile beam steering, a wind scanner—WindScanner—has been developed at the Department ofWind Energy at the Technical University of Denmark (DTU) Risø campus. The WindScanner measures the line-of-sight component of the airflow remotely and by rapid steering, the line-of-sight direction and the focus...... and rescue helicopter are presented. Since the line-of-sight directions of the two synchronized WindScanners were scanned within the plane of interest, the influence of the wind component perpendicular to the plane was avoided. The results also demonstrate the possibilities within less demanding flows...

  4. MATHEMATICAL MODELING OF FLOW PARAMETERS FOR SINGLE WIND TURBINE

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available It is known that on the territory of the Russian Federation the construction of several large wind farms is planned. The tasks connected with design and efficiency evaluation of wind farm work are in demand today. One of the possible directions in design is connected with mathematical modeling. The method of large eddy simulation developed within the direction of computational hydrodynamics allows to reproduce unsteady structure of the flow in details and to determine various integrated values. The calculation of work for single wind turbine installation by means of large eddy simulation and Actuator Line Method along the turbine blade is given in this work. For problem definition the numerical method in the form of a box was considered and the adapted unstructured grid was used.The mathematical model included the main equations of continuity and momentum equations for incompressible fluid. The large-scale vortex structures were calculated by means of integration of the filtered equations. The calculation was carried out with Smagorinsky model for determination of subgrid scale turbulent viscosity. The geometrical parametersof wind turbine were set proceeding from open sources in the Internet.All physical values were defined at center of computational cell. The approximation of items in equations was ex- ecuted with the second order of accuracy for time and space. The equations for coupling velocity and pressure were solved by means of iterative algorithm PIMPLE. The total quantity of the calculated physical values on each time step was equal to 18. So, the resources of a high performance cluster were required.As a result of flow calculation in wake for the three-bladed turbine average and instantaneous values of velocity, pressure, subgrid kinetic energy and turbulent viscosity, components of subgrid stress tensor were worked out. The re- ceived results matched the known results of experiments and numerical simulation, testify the opportunity

  5. Flow and wakes in large wind farms: Final report for UpWind WP8

    DEFF Research Database (Denmark)

    Barthelmie, Rebecca Jane; Frandsen, Sten Tronæs; Rathmann, Ole

    This report summarises the research undertaken through the European Commission funded project UpWind Wp8:Flow. The objective of the work was to develop understanding of flow in large wind farms and to evaluate models of power losses due to wind turbine wakes focusing on complex terrain and offsho...

  6. Wind turbine large-eddy simulations on very coarse grid resolutions using an actuator line model

    NARCIS (Netherlands)

    Martínez-Tossas, Luis A.; Stevens, Richard J.A.M.; Meneveau, Charles

    2016-01-01

    In this work the accuracy of the Actuator Line Model (ALM) in Large Eddy Simulations of wind turbine flow is studied under the specific conditions of very coarse spatial resolutions. For finely-resolved conditions, it is known that ALM provides better accuracy compared to the standard Actuator Disk

  7. Wind Farm Large-Eddy Simulations on Very Coarse Grid Resolutions using an Actuator Line Model

    NARCIS (Netherlands)

    Martinez, L.A.; Meneveau, C.; Stevens, Richard Johannes Antonius Maria

    2016-01-01

    In this work the accuracy of the Actuator Line Model (ALM) in Large Eddy Simula- tions of wind turbine flow is studied under the speci c conditions of very coarse spatial resolutions. For finely-resolved conditions, it is known that ALM provides better accuracy compared to the standard Actuator Disk

  8. Mooring line damping estimation for a floating wind turbine.

    Science.gov (United States)

    Qiao, Dongsheng; Ou, Jinping

    2014-01-01

    The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

  9. Mooring Line Damping Estimation for a Floating Wind Turbine

    Directory of Open Access Journals (Sweden)

    Dongsheng Qiao

    2014-01-01

    Full Text Available The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT. Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

  10. Resilience of electricity grids against transmission line overloads under wind power injection at different nodes.

    Science.gov (United States)

    Schiel, Christoph; Lind, Pedro G; Maass, Philipp

    2017-09-14

    A steadily increasing fraction of renewable energy sources for electricity production requires a better understanding of how stochastic power generation affects the stability of electricity grids. Here, we assess the resilience of an IEEE test grid against single transmission line overloads under wind power injection based on the dc power flow equations and a quasi-static grid response to wind fluctuations. Thereby we focus on the mutual influence of wind power generation at different nodes. We find that overload probabilities vary strongly between different pairs of nodes and become highly affected by spatial correlations of wind fluctuations. An unexpected behaviour is uncovered: for a large number of node pairs, increasing wind power injection at one node can increase the power threshold at the other node with respect to line overloads in the grid. We find that this seemingly paradoxical behaviour is related to the topological distance of the overloaded line from the shortest path connecting the wind nodes. In the considered test grid, it occurs for all node pairs, where the overloaded line belongs to the shortest path.

  11. Apparatus and method for using radar to evaluate wind flow fields for wind energy applications

    Science.gov (United States)

    Schroeder, John; Hirth, Brian; Guynes, Jerry

    2017-02-21

    The present invention provides an apparatus and method for obtaining data to determine one or more characteristics of a wind flow field using one or more radars. Data is collected from the one or more radars, and analyzed to determine the one or more characteristics of the wind flow field. The one or more radars are positioned to have a portion of the wind flow field within a scanning sector of the one or more radars.

  12. Measurement and Assessment of Flow Quality in Wind Tunnels Project

    Data.gov (United States)

    National Aeronautics and Space Administration — New wind tunnel flow quality test and analysis procedures have been developed and will be used to establish standardized turbulent flow quality measurement...

  13. Flow Structure and Turbulence in Wind Farms

    NARCIS (Netherlands)

    Stevens, Richard Johannes Antonius Maria; Meneveau, Charles

    2017-01-01

    Similar to other renewable energy sources, wind energy is characterized by a low power density. Hence, for wind energy to make considerable contributions to the world's overall energy supply, large wind farms (on- and offshore) consisting of arrays of ever larger wind turbines are being envisioned

  14. Overvoltage Propagation from Transmission Line into Transformer Winding

    Directory of Open Access Journals (Sweden)

    Vaclav Kotlan

    2015-01-01

    Full Text Available The paper deals with very fast transient phenomena in a system consisting of two parts: a cable line and a transformer winding. In this case an adequate model should be considered as a circuit with distributed parameters. Its description is given by a system of partial differential equations of hyperbolic type. Our approach is based on a numerical solution in the time domain and the method FDTD has been used. It allows obtaining results in a form of time-space voltage and current wave distribution along the cable line and the transformer winding. This distribution is depending on many factors some of them were studied in this paper.

  15. Flow adjustment inside large finite-size wind farms approaching the infinite wind farm regime

    Science.gov (United States)

    Wu, Ka Ling; Porté-Agel, Fernando

    2017-04-01

    Due to the increasing number and the growing size of wind farms, the distance among them continues to decrease. Thus, it is necessary to understand how these large finite-size wind farms and their wakes could interfere the atmospheric boundary layer (ABL) dynamics and adjacent wind farms. Fully-developed flow inside wind farms has been extensively studied through numerical simulations of infinite wind farms. The transportation of momentum and energy is only vertical and the advection of them is neglected in these infinite wind farms. However, less attention has been paid to examine the length of wind farms required to reach such asymptotic regime and the ABL dynamics in the leading and trailing edges of the large finite-size wind farms. Large eddy simulations are performed in this study to investigate the flow adjustment inside large finite-size wind farms in conventionally-neutral boundary layer with the effect of Coriolis force and free-atmosphere stratification from 1 to 5 K/km. For the large finite-size wind farms considered in the present work, when the potential temperature lapse rate is 5 K/km, the wind farms exceed the height of the ABL by two orders of magnitude for the incoming flow inside the farms to approach the fully-developed regime. An entrance fetch of approximately 40 times of the ABL height is also required for such flow adjustment. At the fully-developed flow regime of the large finite-size wind farms, the flow characteristics match those of infinite wind farms even though they have different adjustment length scales. The role of advection at the entrance and exit regions of the large finite-size wind farms is also examined. The interaction between the internal boundary layer developed above the large finite-size wind farms and the ABL under different potential temperature lapse rates are compared. It is shown that the potential temperature lapse rate plays a role in whether the flow inside the large finite-size wind farms adjusts to the fully

  16. Modelling and Measuring Flow and Wind Turbine Wakes in Large Wind Farms Offshore

    DEFF Research Database (Denmark)

    Barthelmie, Rebecca Jane; Hansen, Kurt Schaldemose; Frandsen, Sten Tronæs

    2009-01-01

    Average power losses due to wind turbine wakes are of the order of 10 to 20% of total power output in large offshore wind farms. Accurately quantifying power losses due to wakes is, therefore, an important part of overall wind farm economics. The focus of this research is to compare different types...... power losses due to wakes and loads. The research presented is part of the EC-funded UpWind project, which aims to radically improve wind turbine and wind farm models in order to continue to improve the costs of wind energy. Reducing wake losses, or even reduce uncertainties in predicting power losses...... from wakes, contributes to the overall goal of reduced costs. Here, we assess the state of the art in wake and flow modelling for offshore wind forms, the focus so for has been cases at the Horns Rev wind form, which indicate that wind form models require modification to reduce under-prediction of wake...

  17. Assessing the vegetation canopy influences on wind flow using wind ...

    Indian Academy of Sciences (India)

    Service. References. Brown S, Nickling W G and Gillies J A 2008 A wind tunnel examination of shear stress partitioning for an assortment of surface roughness distribution; J. Geophys. Res. 113. F02S06, doi: 10.1029/2007JF000790. Buckley R 1987 The effect of sparse vegetation on the transport of dune sand by wind; ...

  18. Flow and wakes in large wind farms. Final report for UpWind WP8

    Energy Technology Data Exchange (ETDEWEB)

    Barthelmie, R.J.; Frandsen, S.T.; Rathmann, O. (Risoe DTU (Denmark)); Hansen, K. (Technical Univ. of Denmark (DTU), Kgs. Lyngby (Denmark)); Politis, E.; Prospathopoulos, J. (CRES (Greece)); Schepers, J.G. (ECN, Petten (Netherlands)); Rados, K. (NTUA, Athens (Greece)); Cabezon, D. (CENER, Sarriguren (Spain)); Schlez, W.; Neubert, A.; Heath, M. (Garrad Hassan and Partners (Germany) (United Kingdom))

    2011-02-15

    This report summarises the research undertaken through the European Commission funded project UpWind Wp8:Flow. The objective of the work was to develop understanding of flow in large wind farms and to evaluate models of power losses due to wind turbine wakes focusing on complex terrain and offshore. A crosscutting activity was to improve and compare the performance of computational fluid dynamics models with wind farm models. The report contains 6 deliverable reports and guideline to wind farm wake analysis as appendices. (Author)

  19. Turbulent Flow Inside and Above a Wind Farm: A Wind-Tunnel Study

    Directory of Open Access Journals (Sweden)

    Leonardo P. Chamorro

    2011-11-01

    Full Text Available Wind-tunnel experiments were carried out to better understand boundary layer effects on the flow pattern inside and above a model wind farm under thermally neutral conditions. Cross-wire anemometry was used to characterize the turbulent flow structure at different locations around a 10 by 3 array of model wind turbines aligned with the mean flow and arranged in two different layouts (inter-turbine separation of 5 and 7 rotor diameters in the direction of the mean flow by 4 rotor diameters in its span. Results suggest that the turbulent flow can be characterized in two broad regions. The first, located below the turbine top tip height, has a direct effect on the performance of the turbines. In that region, the turbulent flow statistics appear to reach equilibrium as close as the third to fourth row of wind turbines for both layouts. In the second region, located right above the first one, the flow adjusts slowly. There, two layers can be identified: an internal boundary layer where the flow is affected by both the incoming wind and the wind turbines, and an equilibrium layer, where the flow is fully adjusted to the wind farm. An adjusted logarithmic velocity distribution is observed in the equilibrium layer starting from the sixth row of wind turbines. The effective surface roughness length induced by the wind farm is found to be higher than that predicted by some existing models. Momentum recovery and turbulence intensity are shown to be affected by the wind farm layout. Power spectra show that the signature of the tip vortices, in both streamwise and vertical velocity components, is highly affected by both the relative location in the wind farm and the wind farm layout.

  20. Transmission Line Series Compensation for Wind Energy Transmission

    International Nuclear Information System (INIS)

    Palanichamy, C; Wong, Y C

    2015-01-01

    Wind energy has demonstrated to be a clean, copious and absolutely renewable source of energy, and the large penetration of it into the power grid indicates that wind energy is considered an effective means of power generation, Transmission of wind energy from remote locations to load centers necessitates long transmission lines. Series compensation is a proven and economical transmission solution to address system power transfer strength, grid stability, and voltage profile issues of long transmission lines. In this paper, a programmable approach to determine the capacitive reactance of series capacitor and optimum location for its placement to achieve maximum power transfer gas been presented. The respective program with sample solutions has been provided for real-time applications. (paper)

  1. Downstream wind flow path diversion and its effects on the performance of vertical axis wind turbine

    International Nuclear Information System (INIS)

    Maganhar, A.L.

    2015-01-01

    In the present experimental study efforts have been made to analysis path diversion effect of downstream wind flow on performance of vertical axis wind turbine (VAWT). For the blockage of downstream wind flow path at various linear displaced positions, a normal erected flat wall, semi-circular and cylindrical shapes were tested for path diverting geometries. Performance of VAWT in terms of improved rotor speed up to 45% was achieved. (author)

  2. Uncertainty quantification in wind farm flow models

    DEFF Research Database (Denmark)

    Murcia Leon, Juan Pablo

    uncertainties through a model chain are presented and applied to several wind energy related problems such as: annual energy production estimation, wind turbine power curve estimation, wake model calibration and validation, and estimation of lifetime equivalent fatigue loads on a wind turbine. Statistical...

  3. Load flow analysis for variable speed offshore wind farms

    DEFF Research Database (Denmark)

    Chen, Zhe; Zhao, Menghua; Blaabjerg, Frede

    2009-01-01

    A serial AC-DC integrated load flow algorithm for variable speed offshore wind farms is proposed. It divides the electrical system of a wind farm into several local networks, and different load flow methods are used for these local networks sequentially. This method is fast, more accurate, and many...... factors such as the different wind farm configurations, the control of wind turbines and the power losses of pulse width modulation converters are considered. The DC/DC converter model is proposed and integrated into load flow algorithm by modifying the Jacobian matrix. Two iterative methods are proposed...... and integrated into the load flow algorithm: one takes into account the control strategy of converters and the other considers the power losses of converters. In addition, different types of variable speed wind turbine systems with different control methods are investigated. Finally, the method is demonstrated...

  4. Power Flow Simulations of a More Renewable California Grid Utilizing Wind and Solar Insolation Forecasting

    Science.gov (United States)

    Hart, E. K.; Jacobson, M. Z.; Dvorak, M. J.

    2008-12-01

    Time series power flow analyses of the California electricity grid are performed with extensive addition of intermittent renewable power. The study focuses on the effects of replacing non-renewable and imported (out-of-state) electricity with wind and solar power on the reliability of the transmission grid. Simulations are performed for specific days chosen throughout the year to capture seasonal fluctuations in load, wind, and insolation. Wind farm expansions and new wind farms are proposed based on regional wind resources and time-dependent wind power output is calculated using a meteorological model and the power curves of specific wind turbines. Solar power is incorporated both as centralized and distributed generation. Concentrating solar thermal plants are modeled using local insolation data and the efficiencies of pre-existing plants. Distributed generation from rooftop PV systems is included using regional insolation data, efficiencies of common PV systems, and census data. The additional power output of these technologies offsets power from large natural gas plants and is balanced for the purposes of load matching largely with hydroelectric power and by curtailment when necessary. A quantitative analysis of the effects of this significant shift in the electricity portfolio of the state of California on power availability and transmission line congestion, using a transmission load-flow model, is presented. A sensitivity analysis is also performed to determine the effects of forecasting errors in wind and insolation on load-matching and transmission line congestion.

  5. An Advanced Actuator Line Method for Wind Energy Applications and Beyond: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Churchfield, Matthew; Schreck, Scott; Martinez-Tossas, Luis A.; Meneveau, Charles; Spalart, Philippe R.

    2017-03-24

    The actuator line method to represent rotor aerodynamics within computational fluid dynamics has been in use for over a decade. This method applies a body force to the flow field along rotating lines corresponding to the individual rotor blades and employs tabular airfoil data to compute the force distribution. The actuator line method is attractive because compared to blade-resolved simulations, the required mesh is much simpler and the computational cost is lower. This work proposes a higher fidelity variant of the actuator line method meant to fill the space between current actuator line and blade-resolved simulations. It contains modifications in two key areas. The first is that of freestream velocity vector estimation along the line, which is necessary to compute the lift and drag along the line using tabular airfoil data. Most current methods rely on point sampling in which the location of sampling is ambiguous. Here we test a velocity sampling method that uses a properly weighted integral over space, removing this ambiguity. The second area of improvement is the function used to project the one-dimensional actuator line force onto the three-dimensional fluid mesh as a body force. We propose and test a projection function that spreads the force over a region that looks something like a real blade with the hope that it will produce the blade local and near wake flow features with more accuracy and higher fidelity. Our goal is that between these two improvements, not only will the flow field predictions be enhanced, but also the spanwise loading will be made more accurate. We refer to this combination of improvements as the advanced actuator line method. We apply these improvements to two different wind turbine cases. Although there is a strong wind energy motivation in our work, there is no reason these advanced actuator line ideas cannot be used in other applications, such as helicopter rotors.

  6. An Advanced Actuator Line Method for Wind Energy Applications and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Churchfield, Matthew J.; Schreck, Scott; Martinez-Tossas, Luis A.; Meneveau, Charles; Spalart, Philippe R.

    2017-01-09

    The actuator line method to represent rotor aerodynamics within computational fluid dynamics has been in use for over a decade. This method applies a body force to the flow field along rotating lines corresponding to the individual rotor blades and employs tabular airfoil data to compute the force distribution. The actuator line method is attractive because compared to blade-resolved simulations, the required mesh is much simpler and the computational cost is lower. This work proposes a higher fidelity variant of the actuator line method meant to fill the space between current actuator line and blade-resolved simulations. It contains modifications in two key areas. The first is that of freestream velocity vector estimation along the line, which is necessary to compute the lift and drag along the line using tabular airfoil data. Most current methods rely on point sampling in which the location of sampling is ambiguous. Here we test a velocity sampling method that uses a properly weighted integral over space, removing this ambiguity. The second area of improvement is the function used to project the one-dimensional actuator line force onto the three-dimensional fluid mesh as a body force. We propose and test a projection function that spreads the force over a region that looks something like a real blade with the hope that it will produce the blade local and near wake flow features with more accuracy and higher fidelity. Our goal is that between these two improvements, not only will the flow field predictions be enhanced, but also the spanwise loading will be made more accurate. We refer to this combination of improvements as the advanced actuator line method. We apply these improvements to two different wind turbine cases. Although there is a strong wind energy motivation in our work, there is no reason these advanced actuator line ideas cannot be used in other applications, such as helicopter rotors.

  7. Incorporation of a Wind Generator Model into a Dynamic Power Flow Analysis

    Directory of Open Access Journals (Sweden)

    Angeles-Camacho C.

    2011-07-01

    Full Text Available Wind energy is nowadays one of the most cost-effective and practical options for electric generation from renewable resources. However, increased penetration of wind generation causes the power networks to be more depend on, and vulnerable to, the varying wind speed. Modeling is a tool which can provide valuable information about the interaction between wind farms and the power network to which they are connected. This paper develops a realistic characterization of a wind generator. The wind generator model is incorporated into an algorithm to investigate its contribution to the stability of the power network in the time domain. The tool obtained is termed dynamic power flow. The wind generator model takes on account the wind speed and the reactive power consumption by induction generators. Dynamic power flow analysis is carried-out using real wind data at 10-minute time intervals collected for one meteorological station. The generation injected at one point into the network provides active power locally and is found to reduce global power losses. However, the power supplied is time-varying and causes fluctuations in voltage magnitude and power fl ows in transmission lines.

  8. Flow separation on wind turbines blades

    NARCIS (Netherlands)

    Corten, G.P.

    2001-01-01

    In the year 2000, 15GW of wind power was installed throughout the world, producing 100PJ of energy annually. This contributes to the total electricity demand by only 0.2%. Both the installed power and the generated energy are increasing by 30% per year world-wide. If the airflow over wind turbine

  9. Emission Line Correlations as Diagnostics of Quasar Winds

    Science.gov (United States)

    Sheldon, Keziah; Richards, Gordon

    2018-01-01

    We investigate correlations between UV and optical emission line properties for a sample of z~0.5 SDSS (Sloan Digital Sky Survey) quasars that have recently been observed by HST. The sample is designed to be comparable in luminosity to the existing reverberation mapping (RM) sample, but less biased in terms of their "eigenvector 1" properties. We seek to understand the conditions under which high-ionization emission lines become dominated by a wind. Our analysis takes advantage of spectral decomposition through Independent Component Analysis (ICA) and archival UV HST spectroscopy of SDSS quasars. With these data we will clarify the needs for RM analysis of quasars with wind-dominated emission features.

  10. Experimental Investigation of the Wind Turbine Blade Root Flow

    NARCIS (Netherlands)

    Akay, B.; Ferreira, C.S.; Van Bussel, G.J.W.

    2010-01-01

    Several methods from experimental to analytical are used to investigate the aerodynamics of a horizontal axis wind turbine. To understand 3D and rotational effects at the root region of a wind turbine blade, correct modeling of the flow field is essential. Aerodynamic models need to be validated by

  11. Chaos in the solar wind flow near Earth

    Indian Academy of Sciences (India)

    We have done a time series analysis of daily average data of solar wind velocity, density and temperature at 1 AU measured by ACE spacecraft for a period of nine years. We have used the raw data without filtering to give a faithful representation of the nonlinear behaviour of the solar wind flow which is a novel one.

  12. Chaos in the solar wind flow near Earth

    Indian Academy of Sciences (India)

    Abstract. We have done a time series analysis of daily average data of solar wind velocity, density and temperature at 1 AU measured by ACE spacecraft for a period of nine years. We have used the raw data without filtering to give a faithful representation of the nonlinear behaviour of the solar wind flow which is a novel one ...

  13. Numerical investigation of air flow in a supersonic wind tunnel

    Science.gov (United States)

    Drozdov, S. M.; Rtishcheva, A. S.

    2017-11-01

    In the framework of TsAGI’s supersonic wind tunnel modernization program aimed at improving flow quality and extending the range of test regimes it was required to design and numerically validate a new test section and a set of shaped nozzles: two flat nozzles with flow Mach number at nozzle exit M=4 and M=5 and two axisymmetric nozzles with M=5 and M=6. Geometric configuration of the nozzles, the test section (an Eiffel chamber) and the diffuser was chosen according to the results of preliminary calculations of two-dimensional air flow in the wind tunnel circuit. The most important part of the work are three-dimensional flow simulation results obtained using ANSYS Fluent software. The following flow properties were investigated: Mach number, total and static pressure, total and static temperature and turbulent viscosity ratio distribution, heat flux density at wind tunnel walls (for high-temperature flow regimes). It is demonstrated that flow perturbations emerging from the junction of the nozzle with the test section and spreading down the test section behind the boundaries of characteristic rhomb’s reverse wedge are nearly impossible to eliminate. Therefore, in order to perform tests under most uniform flow conditions, the model’s center of rotation and optical window axis should be placed as close to the center of the characteristic rhomb as possible. The obtained results became part of scientific and technical basis of supersonic wind tunnel design process and were applied to a generalized class of similar wind tunnels.

  14. Wind-Driven Ecological Flow Regimes Downstream from Hydropower Dams

    Science.gov (United States)

    Kern, J.; Characklis, G. W.

    2012-12-01

    Conventional hydropower can be turned on and off quicker and less expensively than thermal generation (coal, nuclear, or natural gas). These advantages enable hydropower utilities to respond to rapid fluctuations in energy supply and demand. More recently, a growing renewable energy sector has underlined the need for flexible generation capacity that can complement intermittent renewable resources such as wind power. While wind power entails lower variable costs than other types of generation, incorporating it into electric power systems can be problematic. Due to variable and unpredictable wind speeds, wind power is difficult to schedule and must be used when available. As a result, integrating large amounts of wind power into the grid may result in atypical, swiftly changing demand patterns for other forms of generation, placing a premium on sources that can be rapidly ramped up and down. Moreover, uncertainty in wind power forecasts will stipulate increased levels of 'reserve' generation capacity that can respond quickly if real-time wind supply is less than expected. These changes could create new hourly price dynamics for energy and reserves, altering the short-term financial signals that hydroelectric dam operators use to schedule water releases. Traditionally, hourly stream flow patterns below hydropower dams have corresponded in a very predictable manner to electricity demand, whose primary factors are weather (hourly temperature) and economic activity (workday hours). Wind power integration has the potential to yield more variable, less predictable flows at hydro dams, flows that at times could resemble reciprocal wind patterns. An existing body of research explores the impacts of standard, demand-following hydroelectric dams on downstream ecological flows; but weighing the benefits of increased reliance on wind power against further impacts to ecological flows may be a novel challenge for the environmental community. As a preliminary step in meeting this

  15. Data-Mining-Based Intelligent Differential Relaying for Transmission Lines Including UPFC and Wind Farms.

    Science.gov (United States)

    Jena, Manas Kumar; Samantaray, Subhransu Ranjan

    2016-01-01

    This paper presents a data-mining-based intelligent differential relaying scheme for transmission lines, including flexible ac transmission system device, such as unified power flow controller (UPFC) and wind farms. Initially, the current and voltage signals are processed through extended Kalman filter phasor measurement unit for phasor estimation, and 21 potential features are computed at both ends of the line. Once the features are extracted at both ends, the corresponding differential features are derived. These differential features are fed to a data-mining model known as decision tree (DT) to provide the final relaying decision. The proposed technique has been extensively tested for single-circuit transmission line, including UPFC and wind farms with in-feed, double-circuit line with UPFC on one line and wind farm as one of the substations with wide variations in operating parameters. The test results obtained from simulation as well as in real-time digital simulator testing indicate that the DT-based intelligent differential relaying scheme is highly reliable and accurate with a response time of 2.25 cycles from the fault inception.

  16. Narrow line profiles and interacting gas flows in active galaxies

    International Nuclear Information System (INIS)

    Mardaljevic, J.; Raine, D.J.; Smith, M.D.

    1986-01-01

    The 'catapult model' of the narrow line region involves both infalling and outflowing clouds interacting with an outflowing wind. The emission line profiles in this model are derived and the results compared with observation. Supersonic and subsonic winds in the interaction zone produce distinct line profiles, both of which are observed. Flat-topped profiles, the presence of broad wings, asymmetry and line shifts are discussed. A relationship between profile shape and X-ray properties is predicted. (author)

  17. Flow line asymmetric nonimaging concentrating optics

    Science.gov (United States)

    Jiang, Lun; Winston, Roland

    2016-09-01

    Nonimaging Optics has shown that it achieves the theoretical limits by utilizing thermodynamic principles rather than conventional optics. Hence in this paper the condition of the "best" design are both defined and fulfilled in the framework of thermodynamic arguments, which we believe has profound consequences for the designs of thermal and even photovoltaic systems, even illumination and optical communication tasks. This new way of looking at the problem of efficient concentration depends on probabilities, geometric flux field and radiative heat transfer while "optics" in the conventional sense recedes into the background. Some of the new development of flow line designs will be introduced and the connection between the thermodynamics and flow line design will be officially formulated in the framework of geometric flux field. A new way of using geometric flux to design nonimaging optics will be introduced. And finally, we discuss the possibility of 3D ideal nonimaing optics.

  18. Large Eddy Simulation of wind turbines using the actuator line model and immersed boundary method

    Science.gov (United States)

    Santoni, Christian; Carrasquillo-Solís, Kenneth; Leonardi, Stefano

    2014-11-01

    Despite the growth of the energy extracted from wind turbines, the flow physics is still not fully understood even under ideal operational conditions. Large Eddy Simulations of the turbulent flow past a wind turbine in a channel have been performed. The numerical setup reproduces the experiment performed in a wind tunnel at the Norwegian University of Science and Technology (NUST). The code is based on a finite difference scheme with a fractional step and Runge-Kutta, which couples the actuator line model (ALM) and the Immersed Boundary Method (IBM). Two simulations were performed, one neglecting the tower and nacelle resulting in the rotating blades only, the other modeling both the rotating blades as well as the tower and nacelle with IBM. Results relative to the simulation with tower and nacelle have a very good agreement with experiments. Profiles of turbulent kinetic energy shows that the effect of the tower and nacelle is not confined to the hub region but extend to the entire rotor. In addition we placed the wind turbine over an undulated topography to understand how it affects the performances and wake of a wind turbine. Comparison with the results obtained for the smooth wall show an interaction between the rough wall and the wake. The numerical simulations were performed on XSEDE TACC under Grant No. CTS070066. The present work is supported by the National Science Foundation (NSF), Grant IIA-1243482 (WINDINSPIRE).

  19. Adaptive settings of distance relay for MOV-protected series compensated line with distributed capacitance considering wind power

    Science.gov (United States)

    Sivov, Oleg Viktorovich

    Series compensated lines are protected from overvoltage by metal-oxide-varistors (MOVs) connected in parallel with the capacitor bank. The nonlinear characteristics of MOV devices add complexity to fault analysis and distance protection operation. During faults, the impedance of the line is modified by an equivalent impedance of the parallel MOV/capacitor circuit, which affects the distance protection. The intermittent wind generation introduces additional complexity to the system performance and distance protection. Wind variation affects the fault current level and equivalent MOV/capacitor impedance during a fault, and hence the distance relay operation. This thesis studies the impact of the intermittent wind power generation on the operation of MOV during faults. For the purpose of simulation, an equivalent wind farm model is proposed to generate a wind generation profile using wind farm generation from California independent system operator (ISO) as a guide for wind power variation to perform the study. The IEEE 12-bus test system is modified to include MOV-protected series capacitor and the equivalent wind farm model. The modified test system is simulated in the MATLAB/Simulink environment. The study has been achieved considering three phase and single line to ground (SLG) faults on the series compensated line to show the effect of wind variation on the MOV operation. This thesis proposes an adaptive setting method for the mho relay distance protection of series compensated line considering effects of wind power variation and MOV operation. The distributed parameters of a transmission line are taken into account to avoid overreaching and underreaching of distance relays. The study shows that variable wind power affects system power flow and fault current in the compensated line during a fault which affects the operation of MOVs for different fault conditions. The equivalent per-phase impedance of the MOV/capacitor circuit has an effect on the system operation

  20. Line width of Josephson flux flow oscillators

    DEFF Research Database (Denmark)

    Koshelets, V.P.; Dmitriev, P.N.; Sobolev, A.S.

    2002-01-01

    A combination of wide-band electronic tunability and moderate free-running line width makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated submillimeter-wave SIS receivers. The possibility of FFO phase locking at all frequencies of interest has...... to be proven before one initiates real FFO applications. To achieve this goal a comprehensive set of line width measurements of the FFO operating in different regimes has been performed. FFOs with tapered shape have been successfully implemented in order to avoid the superfine resonant structure with voltage...... spacing of about 20 nV and extremely low differential resistance, recently observed in the IVC of the standard rectangular geometry. The obtained results have been compared with existing theories and FFO models in order to understand and possibly eliminate excess noise in the FFO. The intrinsic line width...

  1. Mesoscale to microscale wind farm flow modeling and evaluation: Mesoscale to Microscale Wind Farm Models

    Energy Technology Data Exchange (ETDEWEB)

    Sanz Rodrigo, Javier [National Renewable Energy Centre (CENER), Sarriguren Spain; Chávez Arroyo, Roberto Aurelio [National Renewable Energy Centre (CENER), Sarriguren Spain; Moriarty, Patrick [National Renewable Energy Laboratory (NREL), Golden CO USA; Churchfield, Matthew [National Renewable Energy Laboratory (NREL), Golden CO USA; Kosović, Branko [National Center for Atmospheric Research (NCAR), Boulder CO USA; Réthoré, Pierre-Elouan [Technical University of Denmark (DTU), Roskilde Denmark; Hansen, Kurt Schaldemose [Technical University of Denmark (DTU), Lyngby Denmark; Hahmann, Andrea [Technical University of Denmark (DTU), Roskilde Denmark; Mirocha, Jeffrey D. [Lawrence Livermore National Laboratory, Livermore CA USA; Rife, Daran [DNV GL, San Diego CA USA

    2016-08-31

    The increasing size of wind turbines, with rotors already spanning more than 150 m diameter and hub heights above 100 m, requires proper modeling of the atmospheric boundary layer (ABL) from the surface to the free atmosphere. Furthermore, large wind farm arrays create their own boundary layer structure with unique physics. This poses significant challenges to traditional wind engineering models that rely on surface-layer theories and engineering wind farm models to simulate the flow in and around wind farms. However, adopting an ABL approach offers the opportunity to better integrate wind farm design tools and meteorological models. The challenge is how to build the bridge between atmospheric and wind engineering model communities and how to establish a comprehensive evaluation process that identifies relevant physical phenomena for wind energy applications with modeling and experimental requirements. A framework for model verification, validation, and uncertainty quantification is established to guide this process by a systematic evaluation of the modeling system at increasing levels of complexity. In terms of atmospheric physics, 'building the bridge' means developing models for the so-called 'terra incognita,' a term used to designate the turbulent scales that transition from mesoscale to microscale. This range of scales within atmospheric research deals with the transition from parameterized to resolved turbulence and the improvement of surface boundary-layer parameterizations. The coupling of meteorological and wind engineering flow models and the definition of a formal model evaluation methodology, is a strong area of research for the next generation of wind conditions assessment and wind farm and wind turbine design tools. Some fundamental challenges are identified in order to guide future research in this area.

  2. Calculation of Wind Power Limit adjusting the Continuation Power Flow

    International Nuclear Information System (INIS)

    Santos Fuentefria, Ariel; Castro Fernández, Miguel; Martínez García, Antonio

    2012-01-01

    The wind power insertion in the power system is an important issue and can create some instability problems in voltage and system frequency due to stochastic origin of wind. Know the Wind Power Limit is a very important matter. Existing in bibliography a few methods for calculation of wind power limit. The calculation is based in static constrains, dynamic constraints or both. In this paper is developed a method for the calculation of wind power limit using some adjust in the continuation power flow, and having into account the static constrains. The method is complemented with Minimal Power Production Criterion. The method is proved in the Isla de la Juventud Electric System. The software used in the simulations was the Power System Analysis Toolbox (PSAT). (author)

  3. Large Eddy Simulation of Turbulent Flows in Wind Energy

    DEFF Research Database (Denmark)

    Chivaee, Hamid Sarlak

    Reynolds numbers, and thereafter, the fully-developed infinite wind farm boundary later simulations are performed. Sources of inaccuracy in the simulations are investigated and it is found that high Reynolds number flows are more sensitive to the choice of the SGS model than their low Reynolds number......This research is devoted to the Large Eddy Simulation (LES), and to lesser extent, wind tunnel measurements of turbulent flows in wind energy. It starts with an introduction to the LES technique associated with the solution of the incompressible Navier-Stokes equations, discretized using a finite...... volume method. The study is followed by a detailed investigation of the Sub-Grid Scale (SGS) modeling. New SGS models are implemented into the computing code, and the effect of SGS models are examined for different applications. Fully developed boundary layer flows are investigated at low and high...

  4. Predictive models for moving contact line flows

    Science.gov (United States)

    Rame, Enrique; Garoff, Stephen

    2003-01-01

    Modeling flows with moving contact lines poses the formidable challenge that the usual assumptions of Newtonian fluid and no-slip condition give rise to a well-known singularity. This singularity prevents one from satisfying the contact angle condition to compute the shape of the fluid-fluid interface, a crucial calculation without which design parameters such as the pressure drop needed to move an immiscible 2-fluid system through a solid matrix cannot be evaluated. Some progress has been made for low Capillary number spreading flows. Combining experimental measurements of fluid-fluid interfaces very near the moving contact line with an analytical expression for the interface shape, we can determine a parameter that forms a boundary condition for the macroscopic interface shape when Ca much les than l. This parameter, which plays the role of an "apparent" or macroscopic dynamic contact angle, is shown by the theory to depend on the system geometry through the macroscopic length scale. This theoretically established dependence on geometry allows this parameter to be "transferable" from the geometry of the measurement to any other geometry involving the same material system. Unfortunately this prediction of the theory cannot be tested on Earth.

  5. Improving urban wind flow predictions through data assimilation

    Science.gov (United States)

    Sousa, Jorge; Gorle, Catherine

    2017-11-01

    Computational fluid dynamic is fundamentally important to several aspects in the design of sustainable and resilient urban environments. The prediction of the flow pattern for example can help to determine pedestrian wind comfort, air quality, optimal building ventilation strategies, and wind loading on buildings. However, the significant variability and uncertainty in the boundary conditions poses a challenge when interpreting results as a basis for design decisions. To improve our understanding of the uncertainties in the models and develop better predictive tools, we started a pilot field measurement campaign on Stanford University's campus combined with a detailed numerical prediction of the wind flow. The experimental data is being used to investigate the potential use of data assimilation and inverse techniques to better characterize the uncertainty in the results and improve the confidence in current wind flow predictions. We consider the incoming wind direction and magnitude as unknown parameters and perform a set of Reynolds-averaged Navier-Stokes simulations to build a polynomial chaos expansion response surface at each sensor location. We subsequently use an inverse ensemble Kalman filter to retrieve an estimate for the probabilistic density function of the inflow parameters. Once these distributions are obtained, the forward analysis is repeated to obtain predictions for the flow field in the entire urban canopy and the results are compared with the experimental data. We would like to acknowledge high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR.

  6. Research and analysis on response characteristics of bracket-line coupling system under wind load

    Science.gov (United States)

    Jiayu, Zhao; Qing, Sun

    2018-01-01

    In this paper, a three-dimensional finite element model of bracket-line coupling system is established based on ANSYS software. Using the wind velocity time series which is generated by MATLAB as a power input, by comparing and analyzing the influence of different wind speeds and different wind attack angles, it is found that when 0 degree wind acts on the structure, wires have a certain damping effect in the bracket-line coupling system and at the same wind speed, the 90 degree direction is the most unfavorable wind direction for the whole structure according to the three kinds of angle wind calculated at present. In the bracket-line coupling system, the bracket structure is more sensitive to the increase of wind speed while the conductors are more sensitive to the change of wind attack angle.

  7. 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).

  8. Comparison of the near-wake between actuator-line simulations and a simplified vortex model of a horizontal-axis wind turbine

    DEFF Research Database (Denmark)

    Sarmast, Sasan; Segalini, Antonio; Mikkelsen, Robert Flemming

    2016-01-01

    The flow around an isolated horizontal-axis wind turbine is estimated by means of a new vortex code based on the Biot–Savart law with constant circulation along the blades. The results have been compared with numerical simulations where the wind turbine blades are replaced with actuator lines. Two...... good, validating the analytical method for more general conditions. The present results show that a simple vortex code is able to provide an estimation of the flow around the wind turbine similar to the actuator-line approach but with a negligible computational effort. Copyright © 2015 John Wiley...

  9. Line Ratios for Solar Wind Charge Exchange with Comets

    Energy Technology Data Exchange (ETDEWEB)

    Mullen, P. D.; Cumbee, R. S.; Lyons, D.; Shelton, R. L.; Stancil, P. C. [Department of Physics and Astronomy and the Center for Simulational Physics, University of Georgia, Athens, GA 30602 (United States); Gu, L.; Kaastra, J., E-mail: pmullen2@illinois.edu [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands)

    2017-07-20

    Charge exchange (CX) has emerged in X-ray emission modeling as a significant process that must be considered in many astrophysical environments—particularly comets. Comets host an interaction between solar wind ions and cometary neutrals to promote solar wind charge exchange (SWCX). X-ray observatories provide astronomers and astrophysicists with data for many X-ray emitting comets that are impossible to accurately model without reliable CX data. Here, we utilize a streamlined set of computer programs that incorporate the multi-channel Landau–Zener theory and a cascade model for X-ray emission to generate cross sections and X-ray line ratios for a variety of bare and non-bare ion single electron capture (SEC) collisions. Namely, we consider collisions between the solar wind constituent bare and H-like ions of C, N, O, Ne, Na, Mg, Al, and Si and the cometary neutrals H{sub 2}O, CO, CO{sub 2}, OH, and O. To exemplify the application of this data, we model the X-ray emission of Comet C/2000 WM1 (linear) using the CX package in SPEX and find excellent agreement with observations made with the XMM-Newton RGS detector. Our analyses show that the X-ray intensity is dominated by SWCX with H, while H{sub 2}O plays a secondary role. This is the first time, to our knowledge, that CX cross sections have been implemented into a X-ray spectral fitting package to determine the H to H{sub 2}O ratio in cometary atmospheres. The CX data sets are incorporated into the modeling packages SPEX and Kronos .

  10. Fast Multilevel Panel Method for Wind Turbine Rotor Flow Simulations

    NARCIS (Netherlands)

    van Garrel, Arne; Venner, Cornelis H.; Hoeijmakers, Hendrik Willem Marie

    2017-01-01

    A fast multilevel integral transform method has been developed that enables the rapid analysis of unsteady inviscid flows around wind turbines rotors. A low order panel method is used and the new multi-level multi-integration cluster (MLMIC) method reduces the computational complexity for

  11. AC-DC integrated load flow calculation for variable speed offshore wind farms

    DEFF Research Database (Denmark)

    Zhao, Menghua; Chen, Zhe; Blaabjerg, Frede

    2005-01-01

    This paper proposes a sequential AC-DC integrated load flow algorithm for variable speed offshore wind farms. In this algorithm, the variable frequency and the control strategy of variable speed wind turbine systems are considered. In addition, the losses of wind turbine systems and the losses...... of converters are also integrated into the load flow algorithm. As a general algorithm, it can be applied to different types of wind farm configurations, and the load flow is related to the wind speed....

  12. Fan array wind tunnel: a multifunctional, complex environmental flow manipulator

    Science.gov (United States)

    Dougherty, Christopher; Veismann, Marcel; Gharib, Morteza

    2017-11-01

    The recent emergence of small unmanned aerial vehicles (UAVs) has reshaped the aerospace testing environment. Traditional closed-loop wind tunnels are not particularly suited nor easily retrofit to take advantage of these coordinated, controls-based rotorcraft. As such, a highly configurable, novel wind tunnel aimed at addressing the unmet technical challenges associated with single or formation flight performance of autonomous drone systems is presented. The open-loop fan array wind tunnel features 1296 individually controllable DC fans arranged in a 2.88m x 2.88m array. The fan array can operate with and without a tunnel enclosure and is able to rotate between horizontal and vertical testing configurations. In addition to standard variable speed uniform flow, the fan array can generate both unsteady and shear flows. Through the aid of smaller side fan array units, vortex flows are also possible. Conceptual design, fabrication, and validation of the tunnel performance will be presented, including theoretical and computational predictions of flow speed and turbulence intensity. Validation of these parameters is accomplished through standard pitot-static and hot-wire techniques. Particle image velocimetry (PIV) of various complex flows will also be shown. This material is based upon work supported by the Center for Autonomous Systems and Technologies (CAST) at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT).

  13. Experimental Study on the Wake Meandering Within a Scale Model Wind Farm Subject to a Wind-Tunnel Flow Simulating an Atmospheric Boundary Layer

    Science.gov (United States)

    Coudou, Nicolas; Buckingham, Sophia; Bricteux, Laurent; van Beeck, Jeroen

    2018-04-01

    The phenomenon of meandering of the wind-turbine wake comprises the motion of the wake as a whole in both horizontal and vertical directions as it is advected downstream. The oscillatory motion of the wake is a crucial factor in wind farms, because it increases the fatigue loads, and, in particular, the yaw loads on downstream turbines. To address this phenomenon, experimental investigations are carried out in a wind-tunnel flow simulating an atmospheric boundary layer with the Coriolis effect neglected. A 3 × 3 scaled wind farm composed of three-bladed rotating wind-turbine models is subject to a neutral boundary layer over a slightly-rough surface, i.e. corresponding to offshore conditions. Particle-image-velocimetry measurements are performed in a horizontal plane at hub height in the wakes of the three wind turbines occupying the wind-farm centreline. These measurements allow determination of the wake centrelines, with spectral analysis indicating the characteristic wavelength of the wake-meandering phenomenon. In addition, measurements with hot-wire anemometry are performed along a vertical line in the wakes of the same wind turbines, with both techniques revealing the presence of wake meandering behind all three turbines. The spectral analysis performed with the spatial and temporal signals obtained from these two measurement techniques indicates a Strouhal number of ≈ 0.20 - 0.22 based on the characteristic wake-meandering frequency, the rotor diameter and the flow speed at hub height.

  14. Measurement of rotor centre flow direction and turbulence in wind farm environment

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Demurtas, Giorgio; Sommer, A.

    2014-01-01

    The measurement of inflow to a wind turbine rotor was made with a spinner anemometer on a 2 MW wind turbine in a wind farm of eight wind turbines. The wind speed, yaw misalignment and flow inclination angle was measured during a five months measurement campaign. Angular measurements were calibrat...

  15. Using meteorological forecasts in on-line predictions of wind power

    DEFF Research Database (Denmark)

    Nielsen, Torben Skov; Nielsen, Henrik Aalborg; Madsen, Henrik

    1999-01-01

    This report describes a model investigation into wind power prediction model as well as a tool for predicting the power production from wind turbines in an area - the Wind Power Prediction Tool (WPPT). The predictions are based on on-line measurements of power production for a selected set...

  16. Reducing Turbine Mechanical Loads Using Flow Model-Based Wind Farm Controller

    DEFF Research Database (Denmark)

    Kazda, Jonas; Cutululis, Nicolaos Antonio

    WindFarm [2]. SimWindFarm allows for the simultaneous simulation of the turbulent hub height flow field in the wind farm, the turbine dynamics and the wind farm control. The tests show a reduction of loads when compared to other optimal wind farm control approaches. Future work shall enhance the controller......Cumulated O&M costs of offshore wind farms are comparable with wind turbine CAPEX of such wind farm. In wind farms, wake effects can result in up to 80% higher fatigue loads at downstream wind turbines [1] and consequently larger O&M costs. The present work therefore investigates to reduce...... these loads during the provision of grid balancing services using optimal model-based wind farm control. Wind farm controllers coordinate the operating point of wind turbines in a wind farm in order to achieve a given objective. The investigated objective of the control in this work is to follow a total wind...

  17. Wind tunnel study of a vertical axis wind turbine in a turbulent boundary layer flow

    Science.gov (United States)

    Rolin, Vincent; Porté-Agel, Fernando

    2015-04-01

    Vertical axis wind turbines (VAWTs) are in a relatively infant state of development when compared to their cousins the horizontal axis wind turbines. Very few studies have been carried out to characterize the wake flow behind VAWTs, and virtually none to observe the influence of the atmospheric boundary layer. Here we present results from an experiment carried out at the EPFL-WIRE boundary-layer wind tunnel and designed to study the interaction between a turbulent boundary layer flow and a VAWT. Specifically we use stereoscopic particle image velocimetry to observe and quantify the influence of the boundary layer flow on the wake generated by a VAWT, as well as the effect the VAWT has on the boundary layer flow profile downstream. We find that the wake behind the VAWT is strongly asymmetric, due to the varying aerodynamic forces on the blades as they change their position around the rotor. We also find that the wake adds strong turbulence levels to the flow, particularly on the periphery of the wake where vortices and strong velocity gradients are present. The boundary layer is also shown to cause greater momentum to be entrained downwards rather than upwards into the wake.

  18. Simulating wind and marine hydrokinetic turbines with actuator lines in RANS and LES

    Science.gov (United States)

    Bachant, Peter; Wosnik, Martin

    2015-11-01

    As wind and marine hydrokinetic (MHK) turbine designs mature, focus is shifting towards improving turbine array layouts for maximizing overall power output, i.e., minimizing wake interference for axial-flow or horizontal-axis turbines, or taking advantage of constructive wake interaction for cross-flow or vertical-axis turbines. Towards this goal, an actuator line model (ALM) was developed to provide a computationally feasible method for simulating full turbine arrays inside Navier-Stokes models. The ALM predicts turbine loading with the blade element method combined with sub-models for dynamic stall and flow curvature. The open-source software is written as an extension library for the OpenFOAM CFD package, which allows the ALM body force to be applied to their standard RANS and LES solvers. Turbine forcing is also applied to volume of fluid (VOF) models, e.g., for predicting free surface effects on submerged MHK devices. An additional sub-model is considered for injecting turbulence model scalar quantities based on actuator line element loading. Results are presented for the simulation of performance and wake dynamics of axial- and cross-flow turbines and compared with moderate Reynolds number experiments and body-fitted mesh, blade-resolving CFD. Work supported by NSF-CBET grant 1150797.

  19. CFD Calculations of the Flow Around a Wind Turbine Nacelle

    International Nuclear Information System (INIS)

    Varela, J.; Bercebal, D.

    1999-01-01

    The purpose of this work is to identify the influence of a MADE AE30 wind turbine nacelle on the site calibration anemometer placed on the upper back of the nacelle by means of flow simulations around the nacelle using FLUENT, a Commercial Computational Fluid Dynamics code (CFD), which provides modeling capabilities for the simulation of wide range laminar and turbulent fluid flow problems. Different 2D and 3D simulations were accomplished in order to estimate the effects of the complex geometry on the flow behavior. The speed up and braking values of the air flow at the anemometer position are presented for different flow conditions. Finally some conclusions about the accuracy of results are mentioned. (Author) 5 refs

  20. Computational Design and Analysis of a Transonic Natural Laminar Flow Wing for a Wind Tunnel Model

    Science.gov (United States)

    Lynde, Michelle N.; Campbell, Richard L.

    2017-01-01

    A natural laminar flow (NLF) wind tunnel model has been designed and analyzed for a wind tunnel test in the National Transonic Facility (NTF) at the NASA Langley Research Center. The NLF design method is built into the CDISC design module and uses a Navier-Stokes flow solver, a boundary layer profile solver, and stability analysis and transition prediction software. The NLF design method alters the pressure distribution to support laminar flow on the upper surface of wings with high sweep and flight Reynolds numbers. The method addresses transition due to attachment line contamination/transition, Gortler vortices, and crossflow and Tollmien-Schlichting modal instabilities. The design method is applied to the wing of the Common Research Model (CRM) at transonic flight conditions. Computational analysis predicts significant extents of laminar flow on the wing upper surface, which results in drag savings. A 5.2 percent scale semispan model of the CRM NLF wing will be built and tested in the NTF. This test will aim to validate the NLF design method, as well as characterize the laminar flow testing capabilities in the wind tunnel facility.

  1. Vertical axis wind turbine wake in boundary layer flow in a wind tunnel

    Science.gov (United States)

    Rolin, Vincent; Porté-Agel, Fernando

    2016-04-01

    A vertical axis wind turbine is placed in a boundary layer flow in a wind tunnel, and its wake is investigated. Measurements are performed using an x-wire to measure two components of velocity and turbulence statistics in the wake of the wind turbine. The study is performed at various heights and crosswind positions in order to investigate the full volume of the wake for a range of tip speed ratios. The velocity deficit and levels of turbulence in the wake are related to the performance of the turbine. The asymmetric incoming boundary layer flow causes the rate of recovery in the wake to change as a function of height. Higher shear between the wake and unperturbed flow occurs at the top edge of the wake, inducing stronger turbulence and mixing in this region. The difference in flow relative to the blades causes the velocity deficit and turbulence level to change as a function of crosswind position behind the rotor. The relative difference diminishes with increasing tip speed ratio. Therefore, the wake becomes more homogeneous as tip speed ratio increases.

  2. The predictability of large-scale wind-driven flows

    Directory of Open Access Journals (Sweden)

    A. Mahadevan

    2001-01-01

    Full Text Available The singular values associated with optimally growing perturbations to stationary and time-dependent solutions for the general circulation in an ocean basin provide a measure of the rate at which solutions with nearby initial conditions begin to diverge, and hence, a measure of the predictability of the flow. In this paper, the singular vectors and singular values of stationary and evolving examples of wind-driven, double-gyre circulations in different flow regimes are explored. By changing the Reynolds number in simple quasi-geostrophic models of the wind-driven circulation, steady, weakly aperiodic and chaotic states may be examined. The singular vectors of the steady state reveal some of the physical mechanisms responsible for optimally growing perturbations. In time-dependent cases, the dominant singular values show significant variability in time, indicating strong variations in the predictability of the flow. When the underlying flow is weakly aperiodic, the dominant singular values co-vary with integral measures of the large-scale flow, such as the basin-integrated upper ocean kinetic energy and the transport in the western boundary current extension. Furthermore, in a reduced gravity quasi-geostrophic model of a weakly aperiodic, double-gyre flow, the behaviour of the dominant singular values may be used to predict a change in the large-scale flow, a feature not shared by an analogous two-layer model. When the circulation is in a strongly aperiodic state, the dominant singular values no longer vary coherently with integral measures of the flow. Instead, they fluctuate in a very aperiodic fashion on mesoscale time scales. The dominant singular vectors then depend strongly on the arrangement of mesoscale features in the flow and the evolved forms of the associated singular vectors have relatively short spatial scales. These results have several implications. In weakly aperiodic, periodic, and stationary regimes, the mesoscale energy

  3. MHD Flows in Compact Astrophysical Objects Accretion, Winds and Jets

    CERN Document Server

    Beskin, Vasily S

    2010-01-01

    Accretion flows, winds and jets of compact astrophysical objects and stars are generally described within the framework of hydrodynamical and magnetohydrodynamical (MHD) flows. Analytical analysis of the problem provides profound physical insights, which are essential for interpreting and understanding the results of numerical simulations. Providing such a physical understanding of MHD Flows in Compact Astrophysical Objects is the main goal of this book, which is an updated translation of a successful Russian graduate textbook. The book provides the first detailed introduction into the method of the Grad-Shafranov equation, describing analytically the very broad class of hydrodynamical and MHD flows. It starts with the classical examples of hydrodynamical accretion onto relativistic and nonrelativistic objects. The force-free limit of the Grad-Shafranov equation allows us to analyze in detail the physics of the magnetospheres of radio pulsars and black holes, including the Blandford-Znajek process of energy e...

  4. Electromagnetic energy flow lines as possible paths of photons

    Energy Technology Data Exchange (ETDEWEB)

    Davidovic, M [Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade (Serbia); Sanz, A S; Miret-Artes, S [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, Serrano 123, 28006 Madrid (Spain); Arsenovic, D; Bozic, M [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)], E-mail: milena@grf.bg.ac.yu, E-mail: asanz@imaff.cfmac.csic.es, E-mail: arsenovic@phy.bg.ac.yu, E-mail: bozic@phy.bg.ac.yu, E-mail: s.miret@imaff.cfmac.csic.es

    2009-07-15

    Motivated by recent experiments where interference patterns behind a grating are obtained by accumulating single photon events, we provide here an electromagnetic energy flow-line description to explain the emergence of such patterns. We find and discuss an analogy between the equation describing these energy flow lines and the equation of Bohmian trajectories used to describe the motion of massive particles.

  5. Free flow wind speed from a blade-mounted flow sensor

    DEFF Research Database (Denmark)

    Pedersen, Mads Mølgaard; Larsen, Torben Juul; Aagaard Madsen, Helge

    2018-01-01

    This paper presents a method for obtaining the free-inflow velocities from a 3-D flow sensor mounted on the blade of a wind turbine. From its position on the rotating blade, e.g. one-third from the tip, a blade-mounted flow sensor (BMFS) is able to provide valuable information about the turbulent...... and procedures to estimate the induced velocities, i.e. the disturbance of the flow field caused by the wind turbine. These velocities are subtracted from the flow velocities measured by the BMFS to obtain the free-inflow velocities. Aeroelastic codes, like HAWC2, typically use a similar approach to calculate...... the induction, but they use it for the reversed process, i.e. they add the induction to the free inflow to get the flow velocities at the blades, which are required to calculate the resulting aerodynamic forces. The aerodynamic models included in the current method comprise models based on blade element...

  6. Line Capacity Expansion and Transmission Switching in Power Systems With Large-Scale Wind Power

    DEFF Research Database (Denmark)

    Villumsen, Jonas Christoffer; Bronmo, Geir; Philpott, Andy B.

    2013-01-01

    In 2020 electricity production from wind power should constitute nearly 50% of electricity demand in Denmark. In this paper we look at optimal expansion of the transmission network in order to integrate 50% wind power in the system, while minimizing total fixed investment cost and expected cost...... of power generation. We allow for active switching of transmission elements to reduce congestion effects caused by Kirchhoff's voltage law. Results show that actively switching transmission lines may yield a better utilization of transmission networks with large-scale wind power and increase wind power...... penetration. Furthermore, it is shown that transmission switching is likely to affect the optimal line capacity expansion plan....

  7. High-speed solar wind flow parameters at 1 AU

    International Nuclear Information System (INIS)

    Feldman, W.C.; Asbridge, J.R.; Bame, S.J.; Gosling, J.T.

    1976-01-01

    To develop a set of constraints for theories of solar wind high-speed streams, a detailed study was made of the fastest streams observed at 1 AU during the time period spanning March 1971 through July 1974. Streams were accepted for study only if (1) the maximum speed exceeded 650 km s -1 ; (2) effects of stream-stream dynamical interaction on the flow parameters could be safely separated from the intrinsic characteristics of the high-speed regions; (3) the full width at half maximum (FWHM) of the stream when mapped back to 20 solar radii by using a constant speed approximation was greater than 45degree in Carrington longitude; and (4) there were no obvious solar-activity-induced contaminating effects. Nineteen streams during this time interval satisfied these criteria. Average parameters at 1 AU for those portions of these streams above V=650 km s -1 are given.Not only is it not presently known why electrons are significantly cooler than the protons within high-speed regions, but also observed particle fluxes and convected energy fluxes for speed greater than 650 km s -1 are substantially larger than those values predicted by any of the existing theories of solar wind high-speed streams. More work is therefore needed in refining present solar wind models to see whether suitable modifications and/or combinations of existing theories based on reasonable coronal conditions can accommodate the above high-speed flow parameters

  8. Statistical Analysis of the Impact of Wind Power on Market Quantities and Power Flows

    DEFF Research Database (Denmark)

    Pinson, Pierre; Jónsson, Tryggvi; Zugno, Marco

    2012-01-01

    In view of the increasing penetration of wind power in a number of power systems and markets worldwide, we discuss some of the impacts that wind energy may have on market quantities and cross-border power flows. These impacts are uncovered through statistical analyses of actual market and flow da...... of load and wind power forecasts on Danish and German electricity markets....

  9. Performance analysis of flow lines with non-linear flow of material

    CERN Document Server

    Helber, Stefan

    1999-01-01

    Flow line design is one of the major tasks in production management. The decision to install a set of machines and buffers is often highly irreversible. It determines both cost and revenue to a large extent. In order to assess the economic impact of any possible flow line design, production rates and inventory levels have to be estimated. These performance measures depend on the allocation of buffers whenever the flow of material is occasionally disrupted, for example due to machine failures or quality problems. The book describes analytical methods that can be used to evaluate flow lines much faster than with simulation techniques. Based on these fast analytical techniques, it is possible to determine a flow line design that maximizes the net present value of the flow line investment. The flow of material through the line may be non-linear, for example due to assembly operations or quality inspections.

  10. Radiatively driven winds for different power law spectra. [for explaining narrow and broad quasar absorption lines

    Science.gov (United States)

    Beltrametti, M.

    1980-01-01

    The analytic solutions for radiatively driven winds are given for the case in which the winds are driven by absorption of line and continuum radiation. The wind solutions are analytically estimated for different parameters of the central source and for different power law spectra. For flat spectra, three sonic points can exist; it is shown, however, that only one of these sonic points is physically realistic. Parameters of the central source are given which generate winds of further interest for explaining the narrow and broad absorption lines in quasars. For the quasar model presented here, winds which could give rise to the narrow absorption lines are generated by central sources with parameters which are not realistic for quasars.

  11. Analysis of power enhancement for a row of wind turbines using the actuator line technique

    DEFF Research Database (Denmark)

    Mikkelsen, Robert Flemming; Sørensen, Jens Nørkær; Øye, Stig

    2007-01-01

    The effect of wake interaction for a row of three wind turbines in a wind farm is analysed using the actuator line technique. Both full wake and half wake situations are considered with the aim of deriving the optimal pitch setting of the foremost turbine, with respect to the total power from...

  12. Power flow studies in HVAC and HVDC transmission lines

    Energy Technology Data Exchange (ETDEWEB)

    Oyedokun, D.T.; Folly, K.A. [Cape Town Univ. (South Africa). Dept. of Electrical Engineering

    2008-07-01

    Flexible AC transmission system (FACTS) devices, additional high voltage AC (HVAC) lines, and additional HVDC transmission lines can all be used to increase the capacity of transmission infrastructure. In this paper, 3 case studies were presented to evaluate the different technologies. Power flow analyses were conducted in order to determine the most feasible method of increasing capacity. A 35 per cent increase in load demand was considered in relation to changes in power flow, rotor angle, loading, and reactive power compensation. The study showed that DC limits were reduced at the rectifier substation, and more power was routed via the HVAC line while less power was routed via the HVDC line. A comparison of the case studies showed that using an HVAC transmission line in parallel with an additional HVAC line was the most suitable method of increasing transmission infrastructure. Transmission losses for the double circuit HVAC lines were approximately 60 MW. 13 refs., 6 tabs., 6 figs.

  13. Optimal smoothing length scale for actuator line models of wind turbine blades based on Gaussian body force distribution: Wind energy, actuator line model

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Tossas, L. A. [Department of Mechanical Engineering, Johns Hopkins University, Baltimore 21218 MD USA; Churchfield, M. J. [National Renewable Energy Laboratory, Golden 80401 CO USA; Meneveau, C. [Department of Mechanical Engineering, Johns Hopkins University, Baltimore 21218 MD USA

    2017-01-20

    The actuator line model (ALM) is a commonly used method to represent lifting surfaces such as wind turbine blades within large-eddy simulations (LES). In the ALM, the lift and drag forces are replaced by an imposed body force that is typically smoothed over several grid points using a Gaussian kernel with some prescribed smoothing width e. To date, the choice of e has most often been based on numerical considerations related to the grid spacing used in LES. However, especially for finely resolved LES with grid spacings on the order of or smaller than the chord length of the blade, the best choice of e is not known. In this work, a theoretical approach is followed to determine the most suitable value of e, based on an analytical solution to the linearized inviscid flow response to a Gaussian force. We find that the optimal smoothing width eopt is on the order of 14%-25% of the chord length of the blade, and the center of force is located at about 13%-26% downstream of the leading edge of the blade for the cases considered. These optimal values do not depend on angle of attack and depend only weakly on the type of lifting surface. It is then shown that an even more realistic velocity field can be induced by a 2-D elliptical Gaussian lift-force kernel. Some results are also provided regarding drag force representation.

  14. Solar wind flows associated with hot heavy ions

    International Nuclear Information System (INIS)

    Fenimore, E.E.

    1980-05-01

    Solar wind heavy ion spectra measured with the Vela instrumentation have been studied with the goal of determining the solar origins of various solar wind structures which contain anomalously high ionization states. Since the ionization states freeze-in close to the sun they are good indicators of the plasma conditions in the low and intermediate corona. Heavy ion spectra from three different periods throughout the solar cycle have been analyzed. These data are consistent with freezing-in temperatures ranging from approx. 1.5 x 10 6 K to higher than 9 x 10 6 . The spectra indicating hot coronal conditions occur in roughly 1/7 of all measurements and almost exclusively in postshock flows (PSFs), nonshock related helium abundance enhancements (HAEs), or noncompressive density enhancements (NCDEs). The PSFs and HAEs are both probably interplanetary manifestations of solar flares. The observation of several flare-related HAEs which were not preceded by an interplanetary shock suggests that the flare-heated plasma can evolve into the solar wind without producing a noticeable shock at 1 AU. The NCDEs with hot heavy ions differ from the PSF-HAEs in several ways implying that they evolve from events or places with lower temperatures and less energy than those associated with the flares, but with higher temperatures and densities than the quiet corona. Active regions, coronal mass ejections, and equatorial streamers are possible sources for the NCDEs with spectra indicating hot coronal conditions. These events owe their enhanced densities to coronal processes as opposed to interplanetary dynamical processes. Models of the solar wind expansion demonstrate how some NCDEs can have extreme, nonequilibrium ionization distributions

  15. Line width of Josephson flux flow oscillators

    DEFF Research Database (Denmark)

    Koshelets, V.P.; Dmitriev, P.N.; Sobolev, A.S.

    2002-01-01

    spacing of about 20 nV and extremely low differential resistance, recently observed in the IVC of the standard rectangular geometry. The obtained results have been compared with existing theories and FFO models in order to understand and possibly eliminate excess noise in the FFO. The intrinsic line width...... increases considerably at voltages above the boundary voltage because of the abrupt increase of the internal damping due to Josephson self-coupling. The influence of FFO parameters, in particular the differential resistances associated both with the bias current and with the applied magnetic field...

  16. Modelling of resonance lines in ingomogeneous hot star winds

    Czech Academy of Sciences Publication Activity Database

    Šurlan, Brankica; Hamann, W.-R.; Kubát, Jiří; Oskinova, L.M.; Feldmeier, A.

    -, č. 92 (2013), s. 197-200 ISSN 0373-3742. [Future science with metre-class telescopes. Beograd, 18.09.2012-21.09.2012] R&D Projects: GA ČR GA205/08/0003 Institutional support: RVO:67985815 Keywords : stars winds * outflows stars * mass-loss stars Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  17. Radiation hydrodynamic simulations of line-driven disk winds for ultra-fast outflows

    Science.gov (United States)

    Nomura, Mariko; Ohsuga, Ken; Takahashi, Hiroyuki R.; Wada, Keiichi; Yoshida, Tessei

    2016-02-01

    Using two-dimensional radiation hydrodynamic simulations, we investigate the origin of the ultra-fast outflows (UFOs) that are often observed in luminous active galactic nuclei (AGNs). We found that the radiation force due to the spectral lines generates strong winds (line-driven disk winds) that are launched from the inner region of accretion disks (˜30 Schwarzschild radii). A wide range of black hole masses (MBH) and Eddington ratios (ε) was investigated to study the conditions causing the line-driven winds. For MBH = 106-109 M⊙ and ε = 0.1-0.7, funnel-shaped disk winds appear, in which dense matter is accelerated outward with an opening angle of 70°-80° and with 10% of the speed of light. If we observe the wind along its direction, the velocity, the column density, and the ionization state are consistent with those of the observed UFOs. As long as obscuration by the torus does not affect the observation of X-ray bands, the UFOs could be statistically observed in about 13%-28% of the luminous AGNs, which is not inconsistent with the observed ratio (˜40%). We also found that the results are insensitive to the X-ray luminosity and the density of the disk surface. Thus, we can conclude that UFOs could exist in any luminous AGNs, such as narrow-line Seyfert 1s and quasars with ε > 0.1, with which fast line-driven winds are associated.

  18. Simulation of a 7.7 MW onshore wind farm with the Actuator Line Model

    Science.gov (United States)

    Guggeri, A.; Draper, M.; Usera, G.

    2017-05-01

    Recently, the Actuator Line Model (ALM) has been evaluated with coarser resolution and larger time steps than what is generally recommended, taking into account an atmospheric sheared and turbulent inflow condition. The aim of the present paper is to continue these studies, assessing the capability of the ALM to represent the wind turbines’ interactions in an onshore wind farm. The ‘Libertad’ wind farm, which consists of four 1.9MW Vestas V100 wind turbines, was simulated considering different wind directions, and the results were compared with the wind farm SCADA data, finding good agreement between them. A sensitivity analysis was performed to evaluate the influence of the spatial resolution, finding acceptable agreement, although some differences were found. It is believed that these differences are due to the characteristics of the different Atmospheric Boundary Layer (ABL) simulations taken as inflow condition (precursor simulations).

  19. Flow lines and export lines of Sabalo Gas Field - the engineering of a complex job; Flow lines e export lines de Sabalo - a engenharia da complexidade

    Energy Technology Data Exchange (ETDEWEB)

    Serodio, Conrado Jose Morbach [GDK Engenharia, Salvador, BA (Brazil)

    2003-07-01

    The construction of the natural gas flow lines and export lines system of the Sabalo field, in the far South of Bolivia is an unique job in the pipeline construction area. Its execution is a turning point in terms of engineering and construction technology in this industry. Among the Aguarague Cordillera (mountains), it runs across rocky canyons for more than 5 km, a 2.100 mt long narrow tunnel to overcome the mountains and steep hills along all the ROW length, with a total extension of 70 km, in line pipes ranging from 10'' and 12'' for the flow lines, 28'' for the gas export line and 8' for the condensate line. An integrated construction work plan was settled in order to face and overcome the complex construction situations found in every feet of the pipeline. Four simultaneous work sites were mobilized, 8 independent work fronts, 700 professionals and more than 150 pieces of heavy construction equipment, brought from 3 different countries. Special techniques were adopted also to handle the challenging detail engineering . All in all, the correct conjunction of a sound engineering work, planning, human resources and equipment and the managing flexibility to create alternatives and solutions at the fast pace required by a dynamic work schedule were essential to succeed, in a job with no room for mistakes. The successfully job completion open new possibilities to other challenging projects alike.(author)

  20. Wind farm electrical power production model for load flow analysis

    International Nuclear Information System (INIS)

    Segura-Heras, Isidoro; Escriva-Escriva, Guillermo; Alcazar-Ortega, Manuel

    2011-01-01

    The importance of renewable energy increases in activities relating to new forms of managing and operating electrical power: especially wind power. Wind generation is increasing its share in the electricity generation portfolios of many countries. Wind power production in Spain has doubled over the past four years and has reached 20 GW. One of the greatest problems facing wind farms is that the electrical power generated depends on the variable characteristics of the wind. To become competitive in a liberalized market, the reliability of wind energy must be guaranteed. Good local wind forecasts are therefore essential for the accurate prediction of generation levels for each moment of the day. This paper proposes an electrical power production model for wind farms based on a new method that produces correlated wind speeds for various wind farms. This method enables a reliable evaluation of the impact of new wind farms on the high-voltage distribution grid. (author)

  1. LINCOM wind flow model: Application to complex terrain with thermal stratification

    DEFF Research Database (Denmark)

    Dunkerley, F.; Moreno, J.; Mikkelsen, T.

    2001-01-01

    LINCOM is a fast linearised and spectral wind flow model for use over hilly terrain. It is designed to rapidly generate mean wind field predictions which provide input to atmospheric dispersion models and wind engineering applications. The thermal module, LINCOM-T, has recently been improved to p...

  2. WINDING METHOD SELECTION FOR TECHNICAL IMPLEMENTATION OF FIBER OPTIC COMMUNICATION LINE FOR HIGH-SPEED OBJECT

    Directory of Open Access Journals (Sweden)

    Vyacheslav A. Loparev

    2017-07-01

    Full Text Available The paper deals with fiber-optical cable winding methods for realization of fiber-optic communication line with high-speed object. We consider possible options of coils for optical cable winding providing mobility of one of the cable ends on an object. It is shown that the choice of a winding process is caused by the need of ensuring the minimum deformation of fiber-optical micro cable in case of separation from a winding body. It is revealed that the minimum tension value and its unevenness are observed when reeling from coils with a rocket form. Design ratios for determination of winding parameters are given. It is shown that reduction of tension unevenness reduces the jumps of internal tension and probability of break and emergence of optical signal local attenuation. Decrease in internal stresses occurs due to the absence of overlapping of the coils of the underlying layers with the overlying ones. To confirm the operability and the possibility of constructive implementation of the selected winding scheme, experiments were carried out to perform rocket and other types of winding with the use of a specially designed machine model. It is shown that the application of line rocket winding enables to achieve stability when reeling a cable during the movement and excludes breaks. Attenuation of optical signal decreases due to the increase in the bend minimum radius. This phenomenon is explained by reduction of the internal stresses causing optical signal attenuation in the place of cable separation from the coil.

  3. Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

    Science.gov (United States)

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Jianwei; Gao, Xiaomeng; Wang, Wencai; Acharya, Kumud

    2017-07-01

    Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03 mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

  4. The end of the line for today's wind turbines

    OpenAIRE

    Kolios, Athanasios; Martinez-Luengo, Maria

    2016-01-01

    We need to start thinking today about the future of our wind turbines, according to Dr Athanasios Kolios and María Martínez-Luengo from Cranfield University. EDF's recent announcement that they will extend the life of 4 of their 8 UK-based nuclear power plants has focussed analyst's minds on the pros and cons of extending service life. There are numerous cost and engineering issues at play here. These obviously include balancing the initial investment cost against profits already made...

  5. Effect of Tower Shadow and Wind Shear in a Wind Farm on AC Tie-Line Power Oscillations of Interconnected Power Systems

    DEFF Research Database (Denmark)

    Tan, Jin; Hu, Weihao; Wang, Xiaoru

    2013-01-01

    This paper describes a frequency domain approach for evaluating the impact of tower shadow and wind shear effects (TSWS) on tie-line power oscillations. A simplified frequency domain model of an interconnected power system with a wind farm is developed. The transfer function, which relates the tie......-line power variation to the mechanical power variation of a wind turbine, and the expression of the maximum magnitude of tie-line power oscillations are derived to identify the resonant condition and evaluate the potential risk. The effects of the parameters on the resonant magnitude of the tie-line power...... are also discussed. The frequency domain analysis reveals that TSWS can excite large tie-line power oscillations if the frequency of TSWS approaches the tie-line resonant frequency, especially in the case that the wind farm is integrated into a relatively small grid and the tie-line of the interconnected...

  6. Hydrodynamical wind in magnetized accretion flows with convection

    International Nuclear Information System (INIS)

    Abbassi, Shahram; Mosallanezhad, Amin

    2012-01-01

    The existence of outflow and magnetic fields in the inner region of hot accretion flows has been confirmed by observations and numerical magnetohydrodynamic (MHD) simulations. We present self-similar solutions for radiatively inefficient accretion flows (RIAFs) around black holes in the presence of outflow and a global magnetic field. The influence of outflow is taken into account by adopting a radius that depends on mass accretion rate M-dot = M-dot 0 (r/r 0 ) s with s > 0. We also consider convection through a mixing length formula to calculate convection parameter α con . Moreover we consider the additional magnetic field parameters β r,φ,z [ = c 2 r,φ,z /(2c 2 s )], where c 2 r,φ,z are the Alfvén sound speeds in three directions of cylindrical coordinates. Our numerical results show that by increasing all components of the magnetic field, the surface density and rotational velocity increase, but the sound speed and radial infall velocity of the disk decrease. We have also found that the existence of wind will lead to reduction of surface density as well as rotational velocity. Moreover, the radial velocity, sound speed, advection parameter and the vertical thickness of the disk will increase when outflow becomes important in the RIAF. (research papers)

  7. Investigation of the stochastic subspace identification method for on-line wind turbine tower monitoring

    Science.gov (United States)

    Dai, Kaoshan; Wang, Ying; Lu, Wensheng; Ren, Xiaosong; Huang, Zhenhua

    2017-04-01

    Structural health monitoring (SHM) of wind turbines has been applied in the wind energy industry to obtain their real-time vibration parameters and to ensure their optimum performance. For SHM, the accuracy of its results and the efficiency of its measurement methodology and data processing algorithm are the two major concerns. Selection of proper measurement parameters could improve such accuracy and efficiency. The Stochastic Subspace Identification (SSI) is a widely used data processing algorithm for SHM. This research discussed the accuracy and efficiency of SHM using SSI method to identify vibration parameters of on-line wind turbine towers. Proper measurement parameters, such as optimum measurement duration, are recommended.

  8. Dynamics in the Modern Upper Atmosphere of Venus: Zonal Wind Transition to Subsolar-to-Antisolar Flow

    Science.gov (United States)

    Livengood, T. A.; Kostiuk, T.; Hewagama, T.; Fast, K. E.

    2017-12-01

    We observed Venus on 19-23 Aug 2010 (UT) to investigate equatorial wind velocities from above the cloud tops through the lower thermosphere. Measurements were made from the NASA Infrared Telescope Facility using the NASA Goddard Space Flight Center Heterodyne Instrument for Planetary Winds and Composition. High-resolution spectra were acquired on a CO2 pressure-broadened absorption feature that probes the lower mesosphere ( 70 km altitude) with a non-LTE core emission of the same transition that probes the lower thermosphere ( 110 km). The resolving power of λ/Δλ≈3×107 determines line-of-sight velocity from Doppler shifts to high precision. The altitude differential between the features enables investigating the transition from zonal wind flow near the cloud tops to subsolar-to-antisolar flow in the thermosphere. The fully-resolved carbon dioxide transition was measured near 952.8808 cm-1 (10.494 µm) rest frequency at the equator with 1 arcsec field-of-view on Venus (24 arcsec diameter) distributed about the central meridian and across the terminator at ±15° intervals in longitude. The non-LTE emission is solar-pumped and appears only on the daylight side, probing subsolar-to-antisolar wind velocity vector flowing radially from the subsolar point through the terminator, which was near the central meridian in these observations and had zero line-of-sight wind projection at the terminator. The velocity of the zonal flow is approximately uniform, with maximum line-of-sight projection at the limb, and can be measured by the frequency of the absorption line on both the daylight and dark side. Variations in Doppler shift between the observable features and the differing angular dependence of the contributing wind phenomena thus provide independent mechanisms to distinguish the dynamical processes at the altitude of each observed spectral feature. Winds up to >100 m/s were determined in previous investigations with uncertainties of order 10 m/s or less.

  9. Simulation of flow over double-element airfoil and wind tunnel test for use in vertical axis wind turbine

    DEFF Research Database (Denmark)

    Chougule, Prasad; Nielsen, Søren R.K.

    2014-01-01

    Nowadays, small vertical axis wind turbines are receiving more attention due to their suitability in micro-electricity generation. There are few vertical axis wind turbine designs with good power curve. However, the efficiency of power extraction has not been improved. Therefore, an attempt has...... been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade...... for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel...

  10. Non-radial solar wind flows and geomagnetic activity changes during 1973-2003

    Science.gov (United States)

    Pereira, B. F.; Girish, T. E.

    We have found an association between geomagnetic activity changes and non-radial solar wind flows during the period 1973-2003. The solar wind flow latitude in the GSE system is observed to be higher during intense geomagnetic storm periods. Northward-directed solar wind flows are observed to be higher and a correlation is obtained between this parameter and geomagnetic Ap index during the declining phases of the sunspot cycles. These results suggest an association of non-radial flows from coronal holes and geomagnetic activity during the declining phase of sunspot cycle.

  11. Using Satellite SAR to Characterize the Wind Flow around Offshore Wind Farms

    Directory of Open Access Journals (Sweden)

    Charlotte Bay Hasager

    2015-06-01

    Full Text Available Offshore wind farm cluster effects between neighboring wind farms increase rapidly with the large-scale deployment of offshore wind turbines. The wind farm wakes observed from Synthetic Aperture Radar (SAR are sometimes visible and atmospheric and wake models are here shown to convincingly reproduce the observed very long wind farm wakes. The present study mainly focuses on wind farm wake climatology based on Envisat ASAR. The available SAR data archive covering the large offshore wind farms at Horns Rev has been used for geo-located wind farm wake studies. However, the results are difficult to interpret due to mainly three issues: the limited number of samples per wind directional sector, the coastal wind speed gradient, and oceanic bathymetry effects in the SAR retrievals. A new methodology is developed and presented. This method overcomes effectively the first issue and in most cases, but not always, the second. In the new method all wind field maps are rotated such that the wind is always coming from the same relative direction. By applying the new method to the SAR wind maps, mesoscale and microscale model wake aggregated wind-fields results are compared. The SAR-based findings strongly support the model results at Horns Rev 1.

  12. Implementation of a Generalized Actuator Line Model for Wind Turbine Parameterization in the Weather Research and Forecasting Model

    Energy Technology Data Exchange (ETDEWEB)

    Lundquist, Julie [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Marjanovic, Nikola [University of California, Berkeley; Lawrence Livermore National Laboratory; Mirocha, Jeffrey D. [Lawrence Livermore National Laboratory; Kosovic, Branko [University Corporation for Atmospheric Research; Chow, Fotini Katopodes [University of California, Berkeley

    2017-12-22

    A generalized actuator line (GAL) wind turbine parameterization is implemented within the Weather Research and Forecasting model to enable high-fidelity large-eddy simulations of wind turbine interactions with boundary layer flows under realistic atmospheric forcing conditions. Numerical simulations using the GAL parameterization are evaluated against both an already implemented generalized actuator disk (GAD) wind turbine parameterization and two field campaigns that measured the inflow and near-wake regions of a single turbine. The representation of wake wind speed, variance, and vorticity distributions is examined by comparing fine-resolution GAL and GAD simulations and GAD simulations at both fine and coarse-resolutions. The higher-resolution simulations show slightly larger and more persistent velocity deficits in the wake and substantially increased variance and vorticity when compared to the coarse-resolution GAD. The GAL generates distinct tip and root vortices that maintain coherence as helical tubes for approximately one rotor diameter downstream. Coarse-resolution simulations using the GAD produce similar aggregated wake characteristics to both fine-scale GAD and GAL simulations at a fraction of the computational cost. The GAL parameterization provides the capability to resolve near wake physics, including vorticity shedding and wake expansion.

  13. Implementation and application of the actuator line model by OpenFOAM for a vertical axis wind turbine

    Science.gov (United States)

    Riva, L.; Giljarhus, K.-E.; Hjertager, B.; Kalvig, S. M.

    2017-12-01

    University of Stavanger has started The Smart Sustainable Campus & Energy Lab project, to gain knowledge and facilitate project based education in the field of renewable and sustainable energy and increase the research effort in the same area. This project includes the future installation of a vertical axis wind turbine on the campus roof. A newly developed Computational Fluid Dynamics (CFD) model by OpenFOAM have been implemented to study the wind behavior over the building and the turbine performance. The online available wind turbine model case from Bachant, Goude and Wosnik from 2016 is used as the starting point. This is a Reynolds-Averaged Navier-Stokes equations (RANS) case set up that uses the Actuator Line Model. The available test case considers a water tank with controlled external parameters. Bachant et al.’s model has been modified to study a VAWT in the atmospheric boundary layer. Various simulations have been performed trying to verify the models use and suitability. Simulation outcomes help to understand the impact of the surroundings on the turbine as well as its reaction to parameters changes. The developed model can be used for wind energy and flow simulations for both onshore and offshore applications.

  14. Evaluation of the Wind Flow Variability Using Scanning Doppler Lidar Measurements

    Science.gov (United States)

    Sand, S. C.; Pichugina, Y. L.; Brewer, A.

    2016-12-01

    Better understanding of the wind flow variability at the heights of the modern turbines is essential to accurately assess of generated wind power and efficient turbine operations. Nowadays the wind energy industry often utilizes scanning Doppler lidar to measure wind-speed profiles at high spatial and temporal resolution.The study presents wind flow features captured by scanning Doppler lidars during the second Wind Forecast and Improvement Project (WFIP 2) sponsored by the Department of Energy (DOE) and National Oceanic and Atmospheric Administration (NOAA). This 18-month long experiment in the Columbia River Basin aims to improve model wind forecasts complicated by mountain terrain, coastal effects, and numerous wind farms.To provide a comprehensive dataset to use for characterizing and predicting meteorological phenomena important to Wind Energy, NOAA deployed scanning, pulsed Doppler lidars to two sites in Oregon, one at Wasco, located upstream of all wind farms relative to the predominant westerly flow in the region, and one at Arlington, located in the middle of several wind farms.In this presentation we will describe lidar scanning patterns capable of providing data in conical, or vertical-slice modes. These individual scans were processed to obtain 15-min averaged profiles of wind speed and direction in real time. Visualization of these profiles as time-height cross sections allows us to analyze variability of these parameters with height, time and location, and reveal periods of rapid changes (ramp events). Examples of wind flow variability between two sites of lidar measurements along with examples of reduced wind velocity downwind of operating turbines (wakes) will be presented.

  15. Phased arrays: inline flow line hub inspection using phased arrays

    NARCIS (Netherlands)

    Bloom, J.G.P.; Chougrani, K.; Rundberg, H.; Oldenziel, G.; Deleye, X.; Martina, Q.

    2011-01-01

    The feasibility of the inspection of flow line hubs using the phased array technique was investigated to determine the surface area of the seal area degraded by corrosion. A clean model of the hub was simulated to gain insight into the geometrical echoes and to determine the area covered by the

  16. Examination of forced unsteady separated flow fields on a rotating wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Huyer, S [Univ. of Colorado, Boulder, CO (US)

    1993-04-01

    The wind turbine industry faces many problems regarding the construction of efficient and predictable wind turbine machines. Steady state, two-dimensional wind tunnel data are generally used to predict aerodynamic loads on wind turbine blades. Preliminary experimental evidence indicates that some of the underlying fluid dynamic phenomena could be attributed to dynamic stall, or more specifically to generation of forced unsteady separated flow fields. A collaborative research effort between the University of Colorado and the National Renewable Energy Laboratory was conducted to systematically categorize the local and global effects of three- dimensional forced unsteady flow fields.

  17. CFD and experimental data of closed-loop wind tunnel flow

    Directory of Open Access Journals (Sweden)

    John Kaiser Calautit

    2016-06-01

    Full Text Available The data presented in this article were the basis for the study reported in the research articles entitled ‘A validated design methodology for a closed loop subsonic wind tunnel’ (Calautit et al., 2014 [1], which presented a systematic investigation into the design, simulation and analysis of flow parameters in a wind tunnel using Computational Fluid Dynamics (CFD. The authors evaluated the accuracy of replicating the flow characteristics for which the wind tunnel was designed using numerical simulation. Here, we detail the numerical and experimental set-up for the analysis of the closed-loop subsonic wind tunnel with an empty test section.

  18. Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

    Directory of Open Access Journals (Sweden)

    M. M. Pedersen

    2017-11-01

    Full Text Available In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can be performed from a few hours or days of measurements.In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting.Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production. This is the research question addressed in this paper.The method is first tested using aeroelastic simulations where the dependence of the radial position and effect of multiple blade-mounted flow sensors are also investigated. Next the method is evaluated on the basis of full-scale measurements on a pitch-regulated, variable-speed 3.6 MW wind turbine.It is concluded that the wind speed derived from the blade-mounted flow sensor is highly correlated with the

  19. The role of radiative acceleration in outflows from broad absorption line QSOs. 1: Comparison with O star winds

    Science.gov (United States)

    Arav, Nahum; Li, Zhi-Yun

    1994-01-01

    We investigate the role of radiation pressure in accelerating the broad absorption line (BAL) outflows in QSOs by comparing their properties with those of radiatively driven O star winds. We find that, owing to their lower column densities and higher velocity spreads, BAL outflows have only a few tens of strong resonance lines that are dynamically important, as compared with 10(exp 3) - 10(exp 4) lines in O star winds. We show that the combined radiative force (the 'force multiplier') declines more rapidly as a function of column density for BAL outflows than for O star winds. This is mainly attributed to the absence of lines from excited states in the BAL region. The absorbing gas in BAL outflows must have a small filling factor in order for radiative acceleration to be important dynamically. This allows the absorbing material to remain at a high enough density to maintain the ion species necessary for efficient radiative acceleration as well (as those responsible for the observed absorption), without the average flow density becoming so large that the absorbing matter cannot be accelerated by an increment larger than its own sound speed. The latter condition is necessary if the outflow is to tap a large portion of the incident photon momentum. Once a small filling factor is assumed, radiative acceleration can be more efficient in BAL outflows than in O stars. We show that terminal velocities of a few times 10(exp 4) km/sec can be expected, provided that the absorbing matter does not have to drag with it a much heavier substrate.

  20. New Solutions to Line-Driven Winds of Hot Massive Stars

    Science.gov (United States)

    Gormaz-Matamala, Alex C.; Curé, Michel; Cidale, Lydia; Venero, Roberto

    2017-11-01

    In the frame of radiation driven wind theory (Castor et al.1975), we present self-consistent hydrodynamical solutions to the line-force parameters (k, α, δ) under LTE conditions. Hydrodynamic models are provided by HydWind (Curé 2004). We evaluate these results with those ones previously found in literature, focusing in different regions of the optical depth to be used to perform the calculations. The values for mass-loss rate and terminal velocity obtained from our calculations are also presented. We also examine the line-force parameters for the case when large changes in ionization throughout the wind occurs (δ-slow solutions, Curé et al.2011).

  1. Performance Evaluation on Transmission Tower-Line System with Passive Friction Dampers Subjected to Wind Excitations

    Directory of Open Access Journals (Sweden)

    Bo Chen

    2015-01-01

    Full Text Available The vibration control and performance evaluation on a transmission-tower line system by using friction dampers subjected to wind excitations are carried out in this study. The three-dimensional finite element (FE model of a transmission tower is firstly constructed. A two-dimensional lumped mass model of a transmission tower is developed for dynamic analysis. The analytical model of transmission tower-line system is proposed by taking the dynamic interaction between the tower and the transmission lines into consideration. The mechanical model of passive friction damper is presented by involving the effects of damper axial stiffness. The equation of motion of the transmission tower-line system incorporated with the friction dampers disturbed by wind excitations is established. A real transmission tower-line system is taken as an example to examine the feasibility and reliability of the proposed control approach. An extensive parameter study is carried out to find the optimal parameters of friction damper and to assess the effects of slipping force axial stiffness and hysteresis loop on control performance. The work on an example structure indicates that the application of friction dampers with optimal parameters could significantly reduce wind-induced responses of the transmission tower-line system.

  2. Wind Effects on Flow Patterns and Net Fluxes in Density-Driven High-Latitude Channel Flow

    Science.gov (United States)

    Huntley, Helga S.; Ryan, Patricia

    2018-01-01

    A semianalytic two-dimensional model is used to analyze the interplay between the different forces acting on density-driven flow in high-latitude channels. In particular, the balance between wind stress, viscous forces, baroclinicity, and sea surface slope adjustments under specified flux conditions is examined. Weak winds are found not to change flow patterns appreciably, with minimal (change the flow significantly, especially at the surface, by either strengthening the dual-jet pattern, established without wind, by a factor of 2-3 or initiating return flow at the surface. A nonzero flux does not result in the addition of a uniform velocity throughout the channel cross section, but modifies both along-channel and cross-channel velocities to become more symmetric, dominated by a down-channel jet centered in the domain and counter-clockwise lateral flow. We also consider formulations of the model that allow adjustments of the net flux in response to the wind. Flow patterns change, beyond uniform intensification or weakening, only for strong winds and high Ekman number. Comparisons of the model results to observational data collected in Nares Strait in the Canadian Archipelago in the summer of 2007 show rough agreement, but the model misses the upstream surface jet on the east side of the strait and propagates bathymetric effects too strongly in the vertical for this moderately high eddy viscosity. Nonetheless, the broad strokes of the observed high-latitude flow are reproduced.

  3. Tailoring of electron flow current in magnetically insulated transmission lines

    Directory of Open Access Journals (Sweden)

    J. P. Martin

    2009-03-01

    Full Text Available It is desirable to optimize (minimizing both the inductance and electron flow the magnetically insulated vacuum sections of low impedance pulsed-power drivers. The goal of low inductance is understandable from basic efficiency arguments. The goal of low electron flow results from two observations: (1 flowing electrons generally do not deliver energy to (or even reach most loads, and thus constitute a loss mechanism; (2 energetic electrons deposited in a small area can cause anode damage and anode plasma formation. Low inductance and low electron flow are competing goals; an optimized system requires a balance of the two. While magnetically insulated systems are generally forgiving, there are times when optimization is crucial. For example, in large pulsed-power drivers used to energize high energy density physics loads, the electron flow as a fraction of total current is small, but that flow often reaches the anode in relatively small regions. If the anode temperature becomes high enough to desorb gas, the resulting plasma initiates a gap closure process that can impact system performance. Magnetic-pressure driven (z pinches and material equation of state loads behave like a fixed inductor for much of the drive pulse. It is clear that neither fixed gap nor constant-impedance transmission lines are optimal for driving inductive loads. This work shows a technique for developing the optimal impedance profile for the magnetically insulated section of a high-current driver. Particle-in-cell calculations are used to validate the impedance profiles developed in a radial disk magnetically insulated transmission line geometry. The input parameters are the spacing and location of the minimum gap, the effective load inductance, and the desired electron flow profile. The radial electron flow profiles from these simulations are in good agreement with theoretical predictions when driven at relatively high voltage (i.e., V≥2  MV.

  4. TradeWind Deliverable 5.1: Effects of increasing wind power penetration on the power flows in European grids

    DEFF Research Database (Denmark)

    Lemström, Bettina; Uski-Joutsenvuo, Sanna; Holttinen, Hannele

    2008-01-01

    -border transmission. Risø has written section 4.2 about the impact of prediction errors of wind power production. VTT has carried out the model evaluation described in Chapter 3. Furthermore VTT has analysed the wind speed data, studied the moving weather effects and the capacity factor method presented in section 2...... flow simulations with a grid and market model developed in TradeWind Work Package 3, led by Sintef Energy Research. VTT, Sintef Energy Research and Risø have carried out the simulations of the different scenarios, analysed the results and written Chapter 4 about the impact of wind power on cross.......1, Chapter 5 and section 6.1, respectively. dena has made the calculations with the probabilistic method and written section 6.2....

  5. Correlations between wind flow and population location at 67 light water nuclear power plant sites. [USA

    Energy Technology Data Exchange (ETDEWEB)

    Sprung, J.L.; Steck, G.P.; Frazier, A.W.

    1978-10-01

    Because wind flow and population location are both likely to be influenced by topography, it has been suggested that wind distributions and population distributions ought to be correlated and that the neglect of these correlations in the calculations of the Reactor Safety Study could have resulted in significant underestimates of accident consequences. This paper presents the results of an investigation of correlations between wind roses and population locations at 67 of the 68 power plant sites included in the Reactor Safety Study.

  6. Remote Sensing of Complex Flows by Doppler Wind Lidar: Issues and Preliminary Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, Andrew [National Renewable Energy Lab. (NREL), Golden, CO (United States); Boquet, Matthieu [Leosphere, Orsay (France); Burin Des Roziers, Edward [UL International Gmbh, Freemont, CA (United States); Westerhellweg, Annette [UL International Gmbh, Freemont, CA (United States); Hofsass, Martin [Univ. of Stuttgart (Germany). Stuttgart Wind Energy; Klaas, Tobias [Fraunhofer Inst. for Wind Energy and Energy System Technology, Freiburg (Germany); Vogstad, Klaus [Meventus, Hamburg (Germany); Clive, Peter [Sgurr Energy, Glasgow (United Kingdom); Harris, Mike [ZephIR Limited, Kirkcudbrightshire (United Kingdom); Wylie, Scott [ZephIR Limited, Kirkcudbrightshire (United Kingdom); Osler, Evan [Renewable NRG Systems, Hinesburg, VT (United States); Banta, Bob [National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States); Choukulkar, Aditya [National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States); Lundquist, Julie [Univ. of Colorado, Boulder, CO (United States); Aitken, Matthew [Univ. of Colorado, Boulder, CO (United States)

    2015-12-01

    Remote sensing of winds using lidar has become popular and useful in the wind energy industry. Extensive experience has been gained with using lidar for applications including land-based and offshore resource assessment, plant operations, and turbine control. Prepared by members of International Energy Agency Task 32, this report describes the state of the art in the use of Doppler wind lidar for resource assessment in complex flows. The report will be used as input for future recommended practices on this topic.

  7. On-line sample processing methods in flow analysis

    DEFF Research Database (Denmark)

    Miró, Manuel; Hansen, Elo Harald

    2008-01-01

    In this chapter, the state of the art of flow injection and related approaches thereof for automation and miniaturization of sample processing regardless of the aggregate state of the sample medium is overviewed. The potential of the various generation of flow injection for implementation of in-line...... dilution, derivatization, separation and preconcentration methods encompassing solid reactors, solvent extraction, sorbent extraction, precipitation/coprecipitation, hydride/vapor generation and digestion/leaching protocols as hyphenated to a plethora of detection devices is discussed in detail...

  8. Wind dependence on the flow rate in a natural draught cooling tower

    International Nuclear Information System (INIS)

    Baer, E.; Ernst, G.; Wurz, D.

    1981-01-01

    The efficiency of a natural draught cooling tower depends, among other things, on the effect of the wind on the flow in the tower stack. Determinations were made on a natural draught wet cooling tower 100 metres high, for the purpose of studying this effects. As characteristic quantity, a typical height was determined, the values of which were worked out from the results of the measurements. The efficiency of the stack is affected the most in the case of average wind velocities (when the velocity of the wind is about equal to the mean velocity of the plume). This effect diminishes when the velocity of the wind increases. In the case of average wind velocities, the direction of the wind has an effect, owing to the neighbouring buildings; for slightly greater wind velocities, no effect could be found [fr

  9. Numerical methods for two-phase flow with contact lines

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Clauido

    2012-07-01

    This thesis focuses on numerical methods for two-phase flows, and especially flows with a moving contact line. Moving contact lines occur where the interface between two fluids is in contact with a solid wall. At the location where both fluids and the wall meet, the common continuum descriptions for fluids are not longer valid, since the dynamics around such a contact line are governed by interactions at the molecular level. Therefore the standard numerical continuum models have to be adjusted to handle moving contact lines. In the main part of the thesis a method to manipulate the position and the velocity of a contact line in a two-phase solver, is described. The Navier-Stokes equations are discretized using an explicit finite difference method on a staggered grid. The position of the interface is tracked with the level set method and the discontinuities at the interface are treated in a sharp manner with the ghost fluid method. The contact line is tracked explicitly and its dynamics can be described by an arbitrary function. The key part of the procedure is to enforce a coupling between the contact line and the Navier-Stokes equations as well as the level set method. Results for different contact line models are presented and it is demonstrated that they are in agreement with analytical solutions or results reported in the literature.The presented Navier-Stokes solver is applied as a part in a multiscale method to simulate capillary driven flows. A relation between the contact angle and the contact line velocity is computed by a phase field model resolving the micro scale dynamics in the region around the contact line. The relation of the microscale model is then used to prescribe the dynamics of the contact line in the macro scale solver. This approach allows to exploit the scale separation between the contact line dynamics and the bulk flow. Therefore coarser meshes can be applied for the macro scale flow solver compared to global phase field simulations

  10. OffWindSolver: Wind farm design tool based on actuator line/actuator disk concept in OpenFoam architecture

    Directory of Open Access Journals (Sweden)

    Panjwani Balram

    2014-01-01

    Full Text Available Wind energy is a good alternative to meet the energy requirements in some parts of the world; however the efficiency of wind farm depends on the optimized location of the wind turbines. Therefore a software tool that is capable of predicting the in-situ performance of multiple turbine installations in different operating conditions with reliable accuracy is needed. In present study wind farm layout design tool OffWindSolver is developed within the OpenFoam architecture. Unsteady PisoFoam solver is extended to account for wind turbines, where each turbine is modeled as a sink term in the momentum equation. Turbine modeling is based on actuator line concepts derived from SOWFA code, where each blade of the turbine is represented as a line. The loading on each line/blade of the turbine is estimated using the Blade Element Method (BEM. The inputs for the solver are tabulated airfoil aerodynamic data, dimension and height of the wind turbines, wind magnitude and direction. OffWindSolver is validated for a real wind farm – Lillgrund offshore facility in Sweden/Denmark operated by Vattenfall Vindkraft AB. Because of the scale of the computation, we only examine the effect of wind from one direction at one speed. In the absence of time dependent Marine Atmospheric Boundary Layer (MABL, a log wind profile with surface roughness of 0.04 is used at the inlet. The simulated power production of each turbine is compared to the field data and large-eddy simulation. The overall power of the wind farm is well predicted. The simulation shows the significant decreases of the power for those turbines that were in the wake.

  11. Mesoscale to microscale wind farm flow modeling and evaluation

    DEFF Research Database (Denmark)

    Sanz Rodrigo, Javier; Chávez Arroyo, Roberto Aurelio; Moriarty, Patrick

    2017-01-01

    The increasing size of wind turbines, with rotors already spanning more than 150m diameter and hub heights above 100m, requires proper modeling of the atmospheric boundary layer (ABL) from the surface to the free atmosphere. Furthermore, large wind farm arrays create their own boundary layer stru...

  12. Analysis of environmental dispersion in a wetland flow under the effect of wind: Extended solution

    Science.gov (United States)

    Wang, Huilin; Huai, Wenxin

    2018-02-01

    The accurate analysis of the contaminant transport process in wetland flows is essential for environmental assessment. However, dispersivity assessment becomes complicated when the wind strength and direction are taken into consideration. Prior studies illustrating the wind effect on environmental dispersion in wetland flows simply focused on the mean longitudinal concentration distribution. Moreover, the results obtained by these analyses are not accurate when done on a smaller scale, namely, the initial stage of the contaminant transport process. By combining the concentration moments method (the Aris' method) and Gill's expansion theory, the previous researches on environmental dispersion in wetland flows with effect of wind have been extended. By adopting up to 4th-order moments, the wind effect-as illustrated by dimensionless parameters Er (wind force) and ω (wind direction)-on kurtosis and skewness is discussed, the up to 4th-order vertical concentration distribution is obtained, and the two-dimensional concentration distribution is illustrated. This work demonstrates that wind intensity and direction can significantly affect the contaminant dispersion. Moreover, the study presents a more accurate analytical solution of environmental dispersion in wetland flows under various wind conditions.

  13. Design and numerical investigation of Savonius wind turbine with discharge flow directing capability

    DEFF Research Database (Denmark)

    Tahani, Mojtaba; Rabbani, Ali; Kasaeian, Alibakhsh

    2017-01-01

    Recently, Savonius vertical axis wind turbines due to their capabilities and positive properties have gained a significant attention. The objective of this study is to design and model a Savonius-style vertical axis wind turbine with direct discharge flow capability in order to ventilate building...

  14. Experimental and numerical studies of turbulent flow in an in-line tube bundles

    Directory of Open Access Journals (Sweden)

    Aounalah Mohamed

    2012-04-01

    Full Text Available In the present paper an experimental and a numerical simulation of the turbulent flow in an in-line tube bundles have been performed. The experiments were carried out using a subsonic wind tunnel. The pressure distributions along the tubes (22 circumferential pressure taping were determined for a variation of the azimuthal angle from 0 to 360deg. The drag and lift forces are measured using the TE 44 balance. The Navier-Stokes equations of the turbulent flow are solved using Reynolds Stress and K-ε, turbulence models (RANS provided by Fluent CFD code. An adapted grid using static pressure, pressure coefficient and velocity gradient, furthermore, a second order upwind scheme were used. The obtained results from the experimental and numerical studies show a satisfactory agreement.

  15. A global view of the accretion/ejection flow in AGN: the role of accretion disk winds

    Science.gov (United States)

    Giustini, M.; Done, C.; Proga, D.

    2017-10-01

    By merging theories and X-ray/UV observations we insert winds and failed winds into the geometrical and evolutionary scenarios for the inner regions of Active Galactic Nuclei (AGN). Physically and geometrically different mass accretion flow states onto supermassive black holes correspond to different photon outflows. The photon outflows determine the AGN spectral energy distribution intensity and shape, that affect the presence of different ejection flow states and the consequent mass outflows. The mass and photon accretion and ejection flows in AGN are coupled. We show how by mainly - but not only - varying the Eddington ratio, AGN display different accretion/ejection flows that can explain the observed phenomenology from LLAGN up to highly luminous, super-Eddington QSOs, going through e.g. Seyferts, mini-BAL and BAL QSOs. In particular, during the actively accreting Seyfert/QSO phase of AGN, the presence/absence of powerful line driven accretion disk winds is crucial to explain the observed X-ray/UV phenomenology, including the α_{ox}-L_{UV} correlation and the Baldwin effect.

  16. Analytical Derivation of Electrical-Side Maximum Power Line for Wind Generators

    Directory of Open Access Journals (Sweden)

    Sergei Kolesnik

    2017-09-01

    Full Text Available In order to enhance the maximum power point tracking (MPPT speed of solar generators, offline calculated maximum power line (MPL is often used as a feed-forward signal added to the output of MPPT controller. MPL is nonlinear static electrical characteristic of renewable energy generators connecting all the maximum power points for given temperature. In this letter, electrical side MPL is derived for a typical wind turbine generator (WTG. It is shown that MPLs of solar and wind generators possess similar structure, supporting the similarity between the two energy conversion processes.

  17. IEA-Task 31 WAKEBENCH: Towards a protocol for wind farm flow model evaluation. Part 2: Wind farm wake models

    International Nuclear Information System (INIS)

    Moriarty, Patrick; Rodrigo, Javier Sanz; Gancarski, Pawel; Chuchfield, Matthew; Naughton, Jonathan W; Hansen, Kurt S; Machefaux, Ewan; Maguire, Eoghan; Castellani, Francesco; Terzi, Ludovico; Breton, Simon-Philippe; Ueda, Yuko

    2014-01-01

    Researchers within the International Energy Agency (IEA) Task 31: Wakebench have created a framework for the evaluation of wind farm flow models operating at the microscale level. The framework consists of a model evaluation protocol integrated with a web-based portal for model benchmarking (www.windbench.net). This paper provides an overview of the building-block validation approach applied to wind farm wake models, including best practices for the benchmarking and data processing procedures for validation datasets from wind farm SCADA and meteorological databases. A hierarchy of test cases has been proposed for wake model evaluation, from similarity theory of the axisymmetric wake and idealized infinite wind farm, to single-wake wind tunnel (UMN-EPFL) and field experiments (Sexbierum), to wind farm arrays in offshore (Horns Rev, Lillgrund) and complex terrain conditions (San Gregorio). A summary of results from the axisymmetric wake, Sexbierum, Horns Rev and Lillgrund benchmarks are used to discuss the state-of-the-art of wake model validation and highlight the most relevant issues for future development

  18. Remote Sensing of Complex Flows by Doppler Wind Lidar: Summary of Issues and Preliminary Recommendations from IEA Wind Task 32 Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, Andrew

    2017-06-21

    IEA Wind Task 32 seeks to identify and mitigate the barriers to the adoption of lidar for wind energy applications. In Phase 1 of the task, a working group looked at the state of the art of wind lidar in complex flow conditions. This presentation is a short summary of that work, given at the start of Phase 2.

  19. Evaluation of wind flow with a nacelle-mounted, continuous wave wind lidar

    DEFF Research Database (Denmark)

    Medley, John; Barker, Will; Harris, Mike

    2014-01-01

    IR, increasing the confidence in the ZephIR for measuring wind parameters in this configuration. SCADA data from the turbine was combined with measured wind speeds and directions to derive power curves from the mast data (hub-height) and from ZephIR data (hub-height and rotor-equivalent). The rotor...

  20. Wind Energy Potential at Badin and Pasni Costal Line of Pakistan

    Directory of Open Access Journals (Sweden)

    Ghulam Sarwar Kaloi

    2017-06-01

    Full Text Available Unfortunately, Pakistan is facing an acute energy crisis since the past decade due to the increasing population growth and is heavily dependent on imports of fossil fuels. The shortage of the electricity is 14-18 hours in rural areas and 8-10 hours in urban areas. This situation has been significantly affecting the residential, industrial and commercial sectors in the country. At this time, it is immense challenges for the government to keep the power supply provision continue in the future for the country. In this situation, it has been the increased research to explore renewable energy resources in the country to fulfill the deficit scenario in the state. The renewable energy sector has not penetrated in the energy mix, currently in the upcoming markets. This paper highlights the steps taken by the country in the past and is taking steps at the present time to get rid of from the existing energy crisis when most urban areas are suffering from power outages for 12 hours on regular basis. Until 2009, no single grid interconnected wind established, but now the circumstances are changing significantly and wind farms are contributing to the national grid is the reality now. The initiation of the three wind farms interconnection network and many others in the pipeline are going to be operational soon. The federal policy on wind energy system has recently changed. Surprisingly, the continuing schemes of the wind farm are getting slow. This paper reviews developments in the wind energy sector in the country and lists some suggestions that can contribute to improving the penetration of wind energy in the national energy sector. Keywords: Wind energy, evolution of wind resource, Wind sites of Pakistan Article History: Received Dec 16th 2016; Received in revised form May 15th 2017; Accepted June 18th 2017; Available online How to Cite This Article: Kaloi,G.S., Wang, J., Baloch, M.H and Tahir, S. (2017 Wind Energy Potential at Badin and Pasni Costal Line

  1. Analysis of Power Enhancement for a Row of Wind Turbines Using the Actuator Line Technique

    International Nuclear Information System (INIS)

    Mikkelsen, Robert; Soerensen, Jens N; Oeye, Stig; Troldborg, Niels

    2007-01-01

    The effect of wake interaction for a row of three wind turbines in a wind farm is analysed using the actuator line technique. Both full wake and half wake situations are considered with the aim of deriving the optimal pitch setting of the foremost turbine, with respect to the total power from the row. The mutual distance between the turbines is 5 diameters and the turbines are considered to operate in a wind shear with an exponent of 0.15, with the rotor centre located at 1.4 radii from the ground. The main findings reveal clear effects of reducing the loading on the foremost turbine towards increased production of turbine 2 and 3 in a row

  2. Upper Meter Processes: Short Wind, Waves, Surface Flow and Turbulence

    National Research Council Canada - National Science Library

    Klinke, Jochen

    2001-01-01

    This work is an extension of the early works on measuring short wind waves that have been funded by ONR for seven years, During this seven-year period, we have collected the only available systematic...

  3. Operational and Strategic Implementation of Dynamic Line Rating for Optimized Wind Energy Generation Integration

    Energy Technology Data Exchange (ETDEWEB)

    Gentle, Jake Paul [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-12-01

    One primary goal of rendering today’s transmission grid “smarter” is to optimize and better manage its power transfer capacity in real time. Power transfer capacity is affected by three main elements: stability, voltage limits, and thermal ratings. All three are critical, but thermal ratings represent the greatest opportunity to quickly, reliably and economically utilize the grid’s true capacity. With the “Smarter Grid”, new solutions have been sought to give operators a better grasp on real time conditions, allowing them to manage and extend the usefulness of existing transmission infrastructure in a safe and reliable manner. The objective of the INL Wind Program is to provide industry a Dynamic Line Rating (DLR) solution that is state of the art as measured by cost, accuracy and dependability, to enable human operators to make informed decisions and take appropriate actions without human or system overloading and impacting the reliability of the grid. In addition to mitigating transmission line congestion to better integrate wind, DLR also offers the opportunity to improve the grid with optimized utilization of transmission lines to relieve congestion in general. As wind-generated energy has become a bigger part of the nation’s energy portfolio, researchers have learned that wind not only turns turbine blades to generate electricity, but can cool transmission lines and increase transfer capabilities significantly, sometimes up to 60 percent. INL’s DLR development supports EERE and The Wind Energy Technology Office’s goals by informing system planners and grid operators of available transmission capacity, beyond typical Static Line Ratings (SLR). SLRs are based on a fixed set of conservative environmental conditions to establish a limit on the amount of current lines can safely carry without overheating. Using commercially available weather monitors mounted on industry informed custom brackets developed by INL in combination with Computational

  4. Study of Flow Deformation around Wind-Vane Mounted Three-Dimensional Hot-Wire Probes

    DEFF Research Database (Denmark)

    Rømer Rasmussen, K.; Larsen, Søren Ejling; Jørgensen, F. E.

    1981-01-01

    Open wind tunnel tests on several different sensor systems consisting of triaxial hot-wire probes mounted on wind vanes (DISA and Riso vanes) have shown that flow deformation around the hot-wire sensor introduces errors in the measured velocity components. Though changes in the horizontal...... components proved to be negligible, flow deformation resulted in an overestimation of the vertical component from 1.1 to 1.5, depending on the direction of the vertical component. Turbulence and mean value data were adjusted by use of a linear correction derived from the wind tunnel tests. Wind vane...... construction must strike a compromise between minor flow disturbance and sufficient probe support. The final version of the DISA vane resulted in an acceptable vertical correction of about 10%....

  5. Line-driven disc wind model for ultrafast outflows in active galactic nuclei - scaling with luminosity

    Science.gov (United States)

    Nomura, M.; Ohsuga, K.

    2017-03-01

    In order to reveal the origin of the ultrafast outflows (UFOs) that are frequently observed in active galactic nuclei (AGNs), we perform two-dimensional radiation hydrodynamics simulations of the line-driven disc winds, which are accelerated by the radiation force due to the spectral lines. The line-driven winds are successfully launched for the range of MBH = 106-9 M⊙ and ε = 0.1-0.5, and the resulting mass outflow rate (dot{M_w}), momentum flux (dot{p_w}), and kinetic luminosity (dot{E_w}) are in the region containing 90 per cent of the posterior probability distribution in the dot{M}_w-Lbol plane, dot{p}_w-Lbol plane, and dot{E}_w-Lbol plane shown in Gofford et al., where MBH is the black hole mass, ε is the Eddington ratio, and Lbol is the bolometric luminosity. The best-fitting relations in Gofford et al., d log dot{M_w}/d log {L_bol}˜ 0.9, d log dot{p_w}/d log {L_bol}˜ 1.2, and d log dot{E_w}/d log {L_bol}˜ 1.5, are roughly consistent with our results, d log dot{M_w}/d log {L_bol}˜ 9/8, d log dot{p_w}/d log {L_bol}˜ 10/8, and d log dot{E_w}/d log {L_bol}˜ 11/8. In addition, our model predicts that no UFO features are detected for the AGNs with ε ≲ 0.01, since the winds do not appear. Also, only AGNs with MBH ≲ 108 M⊙ exhibit the UFOs when ε ∼ 0.025. These predictions nicely agree with the X-ray observations. These results support that the line-driven disc wind is the origin of the UFOs.

  6. 2.5 MHz Line-Width High-energy, 2 Micrometer Coherent Wind Lidar Transmitter

    Science.gov (United States)

    Petros, Mulugeta; Yu, Jirong; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Singh, Upendra N.; Reithmaier, Karl

    2007-01-01

    2 micron solid-state lasers are the primary choice for coherent Doppler wind detection. As wind lidars, they are used for wake vortex and clear air turbulence detection providing air transport safety. In addition, 2 micron lasers are one of the candidates for CO2 detection lidars. The rich CO2 absorption line around 2 micron, combined with the long upper state life of time, has made Ho based 2 micron lasers a viable candidate for CO2 sensing DIAL instrument. The design and fabrication of a compact coherent laser radar transmitter for Troposphere wind sensing is under way. This system is hardened for ground as well as airborne applications. As a transmitter for a coherent wind lidar, this laser has stringent spectral line width and beam quality requirements. Although the absolute wavelength does not have to be fixed for wind detection, to maximize return signal, the output wavelength should avoid atmospheric CO2 and H2O absorption lines. The base line laser material is Ho:Tm:LuLF which is an isomorph of Ho:Tm:YLF. LuLF produces 20% more output power than Ho:Tm:YLF. In these materials the Tm absorption cross-section, the Ho emission cross-section, the Tm to Ho energy transfer parameters and the Ho (sup 5) I (sub 7) radiative life time are all identical. However, the improved performance of the LuLF is attributed to the lower thermal population in the (sup 5) I (sub 8) manifold. It also provides higher normal mode to Q-switch conversion than YLF at high pump energy indicating a lower up-conversion. The laser architecture is composed of a seed laser, a ring oscillator, and a double pass amplifier. The seed laser is a single longitudinal mode with a line width of 13 KHz. The 100mJ class oscillator is stretched to 3 meters to accommodate the line-width requirement without compromising the range resolution of the instrument. The amplifier is double passed to produce greater than 300mJ energy.

  7. INVESTIGATION OF A DYNAMIC POWER LINE RATING CONCEPT FOR IMPROVED WIND ENERGY INTEGRATION OVER COMPLEX TERRAIN

    Energy Technology Data Exchange (ETDEWEB)

    Jake P. Gentle; Kurt S Myers; Tyler B Phillips; Inanc Senocak; Phil Anderson

    2014-08-01

    Dynamic Line Rating (DLR) is a smart grid technology that allows the rating of power line to be based on real-time conductor temperature dependent on local weather conditions. In current practice overhead power lines are generally given a conservative rating based on worst case weather conditions. Using historical weather data collected over a test bed area, we demonstrate there is often additional transmission capacity not being utilized with the current static rating practice. We investigate a new dynamic line rating methodology using computational fluid dynamics (CFD) to determine wind conditions along transmission lines at dense intervals. Simulated results are used to determine conductor temperature by calculating the transient thermal response of the conductor under variable environmental conditions. In calculating the conductor temperature, we use both a calculation with steady-state assumption and a transient calculation. Under low wind conditions, steady-state assumption predicts higher conductor temperatures that could lead to curtailments, whereas transient calculations produce conductor temperatures that are significantly lower, implying the availability of additional transmission capacity.

  8. Numerical Analysis of Flow Field in Generator End-Winding Region

    Directory of Open Access Journals (Sweden)

    Wei Tong

    2008-01-01

    Full Text Available Cooling in an end-winding region of a high-powered, large-sized generator still remains a challenge today because of a number of factors: a larger number of parts/components with irregular geometries, complexity in cooling flow paths, flow splitting and mixing, and interactions between rotor-induced rotating flows and nonrotating flows from stationary sections. One of the key challenges is to model cooling flows passing through armature bars, which are made up of bundles of strands of insulated copper wires and are bent oppositely to cross each other. This work succeeded in modeling a complex generator end-winding region with great efforts to simplify the model by treating the armature bar region as a porous medium. The flow and pressure fields at the end-winding region were investigated numerically using an axial symmetric computational fluid dynamics (CFD model. Based on the analysis, the cooling flow rate at each flow branch (rotor-stator gap, rotor subslot, outside space block, and small ventilation holes to the heat exchanger was determined, and the high-pressure gradient zones were identified. The CFD results have been successfully used to optimize the flow path configuration for improving the generator operation performance, and the control of the cooling flow, as well as minimizing windage losses and flow-introduced noises.

  9. Winds of Massive Magnetic Stars: Interacting Fields and Flow

    Science.gov (United States)

    Daley-Yates, S.; Stevens, I. R.

    2018-01-01

    We present results of 3D numerical simulations of magnetically confined, radiatively driven stellar winds of massive stars, conducted using the astrophysical MHD code Pluto, with a focus on understanding the rotational variability of radio and sub-mm emission. Radiative driving is implemented according to the Castor, Abbott and Klein theory of radiatively driven winds. Many magnetic massive stars posses a magnetic axis which is inclined with respect to the rotational axis. This misalignment leads to a complex wind structure as magnetic confinement, centrifugal acceleration and radiative driving act to channel the circumstellar plasma into a warped disk whose observable properties should be apparent in multiple wavelengths. This structure is analysed to calculate free-free thermal radio emission and determine the characteristic intensity maps and radio light curves.

  10. Using linear programming to analyze and optimize stochastic flow lines

    DEFF Research Database (Denmark)

    Helber, Stefan; Schimmelpfeng, Katja; Stolletz, Raik

    2011-01-01

    This paper presents a linear programming approach to analyze and optimize flow lines with limited buffer capacities and stochastic processing times. The basic idea is to solve a huge but simple linear program that models an entire simulation run of a multi-stage production process in discrete time......, to determine a production rate estimate. As our methodology is purely numerical, it offers the full modeling flexibility of stochastic simulation with respect to the probability distribution of processing times. However, unlike discrete-event simulation models, it also offers the optimization power of linear...

  11. Enhanced Kalman Filtering for a 2D CFD NS Wind Farm Flow Model

    International Nuclear Information System (INIS)

    Doekemeijer, B M; Van Wingerden, J W; Boersma, S; Pao, L Y

    2016-01-01

    Wind turbines are often grouped together for financial reasons, but due to wake development this usually results in decreased turbine lifetimes and power capture, and thereby an increased levelized cost of energy (LCOE). Wind farm control aims to minimize this cost by operating turbines at their optimal control settings. Most state-of-the-art control algorithms are open-loop and rely on low fidelity, static flow models. Closed-loop control relying on a dynamic model and state observer has real potential to further decrease wind's LCOE, but is often too computationally expensive for practical use. In this paper two time-efficient Kalman filter (KF) variants are outlined incorporating the medium fidelity, dynamic flow model “WindFarmSimulator” (WFSim). This model relies on a discretized set of Navier-Stokes equations in two dimensions to predict the flow in wind farms at low computational cost. The filters implemented are an Ensemble KF and an Approximate KF. Simulations in which a high fidelity simulation model represents the true wind farm show that these filters are 10"1 —10"2 times faster than a regular KF with comparable or better performance, correcting for wake dynamics that are not modeled in WFSim (noticeably, wake meandering and turbine hub effects). This is a first big step towards real-time closed-loop control for wind farms. (paper)

  12. WAsP engineering flow model for wind over land and sea

    DEFF Research Database (Denmark)

    Astrup, P.; Larsen, Søren Ejling

    1999-01-01

    This report presents the basic wind flow model of WAsP Engineering. The model consists in principle of three parts: the LINCOM model for neutrally stable flow over terrain with hills and varying surface roughness, a sea surface roughness model, and anobstacle model. To better predict flow over...... of literature data for the Charnock parameter as function of the so called wave age, the ratio between wave velocity and friction velocity, plus a correlation ofwave age to the geometrically obtainable water fetch. A model for the influence on the wind of multiple, finite size, interacting obstacles with any...

  13. Optimal Power Flow Management Control for Grid Connected Photovoltaic/Wind turbine/Diesel generator (GCPWD) Hybrid System with Batteries

    OpenAIRE

    Murugan, Bala; S., Manoharan

    2016-01-01

    This paper proposes a Optimal Power Flow Management control for Grid Connected Photovoltaic/Wind turbine/ Diesel generator (GCPWD) Hybrid System with hybrid storage system. The energy system having a photo voltaic (PV) panel, wind turbine (WT) and diesel generator (DG) for continuous power flow management. A diesel generator is added to ensure uninterrupted power supply due to the discontinuous nature of solar and wind resources. The developed Grid Connected Photovoltaic/Wind turbine/ Diesel ...

  14. Evaluation of power flow solutions with fixed speed wind turbine generating systems

    International Nuclear Information System (INIS)

    Haque, M.H.

    2014-01-01

    Highlights: • The model of a wind generator is modified and incorporated into a power flow program. • Unlike previous methods, modification to source codes of the program is not required. • The turbine power curve is mathematically expressed using manufacturer’s data. • The power flow of the IEEE 118-bus system is successfully solved with 12 wind farms for 1000 random cases of wind speeds. • For a simple system, the load flow results are also compared with the corresponding steady state values of dynamic responses. - Abstract: An increased penetration of wind turbine generating systems into power grid calls for proper modeling of the systems and incorporating the model into various computational tools used in power system operation and planning studies. This paper proposes a simple method of incorporating the exact equivalent circuit of a fixed speed wind generator into conventional power flow program. The method simply adds two internal buses of the generator to include all parameters of the equivalent circuit. For a given wind speed, the active power injection into one of the internal buses is determined through wind turbine power curve supplied by the manufacturers. The internal buses of the model can be treated as a traditional P–Q bus and thus can easily be incorporated into any standard power flow program by simply augmenting the input data files and without modifying source codes of the program. The effectiveness of the proposed method is then evaluated on a simple system as well as on the IEEE 30- and 118-bus systems. The results of the simple system are also compared with those found through Matlab/Simulink using dynamic model of wind generating system given in SimPowerSystems blockset

  15. Absorption lines from magnetically driven winds in X-ray binaries

    Science.gov (United States)

    Chakravorty, S.; Petrucci, P.-O.; Ferreira, J.; Henri, G.; Belmont, R.; Clavel, M.; Corbel, S.; Rodriguez, J.; Coriat, M.; Drappeau, S.; Malzac, J.

    2016-05-01

    Context. High resolution X-ray spectra of black hole X-ray binaries (BHBs) show blueshifted absorption lines suggesting the presence of outflowing winds. Furthermore, observations show that the disk winds are equatorial and they occur in the Softer (disk dominated) states of the outburst and are less prominent or absent in the Harder (power-law dominated) states. Aims: We want to test whether the self-similar magneto-hydrodynamic (MHD) accretion-ejection models can explain the observational results for accretion disk winds in BHBs. In our models, the density at the base of the outflow from the accretion disk is not a free parameter. This mass loading is determined by solving the full set of dynamical MHD equations without neglecting any physical term. Thus, the physical properties of the outflow depend on and are controlled by the global structure of the disk. Methods: We studied different MHD solutions characterized by different values of the disk aspect ratio (ɛ) and the ejection efficiency (p). We also generate two kinds of MHD solutions depending on the absence (cold solution) or presence (warm solution) of heating at the disk surface. Such heating could be either from dissipation of energy due to MHD turbulence in the disk or from illumination of the disk surface. Warm solutions can have large (>0.1) values of p, which would imply larger wind mass loading at the base of the outflow. We use each of these MHD solutions to predict the physical parameters (distance, density, velocity, magnetic field, etc.) of an outflow. Motivated by observational results, we have put limits on the ionization parameter (ξ), column density, and timescales. Further constraints were derived for the allowed values of ξ from thermodynamic instability considerations, particularly for the Hard SED. These physical constraints were imposed on each of these outflows to select regions within it, which are consistent with the observed winds. Results: The cold MHD solutions are found to be

  16. Multilevel panel method for wind turbine rotor flow simulations

    NARCIS (Netherlands)

    van Garrel, Arne

    2016-01-01

    Simulation methods of wind turbine aerodynamics currently in use mainly fall into two categories: the first is the group of traditional low-fidelity engineering models and the second is the group of computationally expensive CFD methods based on the Navier-Stokes equations. For an engineering

  17. Analysis of counter flow of corona wind for heat transfer enhancement

    Science.gov (United States)

    Shin, Dong Ho; Baek, Soo Hong; Ko, Han Seo

    2018-03-01

    A heat sink for cooling devices using the counter flow of a corona wind was developed in this study. Detailed information about the numerical investigations of forced convection using the corona wind was presented. The fins of the heat sink using the counter flow of a corona wind were also investigated. The corona wind generator with a wire-to-plate electrode arrangement was used for generating the counter flow to the fin. The compact and simple geometric characteristics of the corona wind generator facilitate the application of the heat sink using the counter flow, demonstrating the heat sink is effective for cooling electronic devices. Parametric studies were performed to analyze the effect of the counter flow on the fins. Also, the velocity and temperature were measured experimentally for the test mock-up of the heat sink with the corona wind generator to verify the numerical results. From a numerical study, the type of fin and its optimal height, length, and pitch were suggested for various heat fluxes. In addition, the correlations to calculate the mass of the developed heat sink and its cooling performance in terms of the heat transfer coefficient were derived. Finally, the cooling efficiencies corresponding to the mass, applied power, total size, and noise of the devices were compared with the existing commercial central processing unit (CPU) cooling devices with rotor fans. As a result, it was confirmed that the heat sink using the counter flow of the corona wind showed appropriate efficiencies for cooling electronic devices, and is a suitable replacement for the existing cooling device for high power electronics.

  18. A review of wind turbine-oriented active flow control strategies

    Science.gov (United States)

    Aubrun, Sandrine; Leroy, Annie; Devinant, Philippe

    2017-10-01

    To reduce the levelized cost of energy, the energy production, robustness and lifespan of horizontal axis wind turbines (HAWTs) have to be improved to ensure optimal energy production and operational availability during periods longer than 15-20 years. HAWTs are subject to unsteady wind loads that generate combinations of unsteady mechanical loads with characteristic time scales from seconds to minutes. This can be reduced by controlling the aerodynamic performance of the wind turbine rotors in real time to compensate the overloads. Mitigating load fluctuations and optimizing the aerodynamic performance at higher time scales need the development of fast-response active flow control (AFC) strategies located as close as possible to the torque generation, i.e., directly on the blades. The most conventional actuators currently used in HAWTs are mechanical flaps/tabs (similar to aeronautical accessories), but some more innovative concepts based on fluidic and plasma actuators are very promising since they are devoid of mechanical parts, have a fast response and can be driven in unsteady modes to influence natural instabilities of the flow. In this context, the present paper aims at giving a state-of-the-art review of current research in wind turbine-oriented flow control strategies applied at the blade scale. It provides an overview of research conducted in the last decade dealing with the actuators and devices devoted to developing AFC on rotor blades, focusing on the flow phenomena that they cause and that can lead to aerodynamic load increase or decrease. After providing some general background on wind turbine blade aerodynamics and on the atmospheric flows in which HAWTs operate, the review focuses on flow separation control and circulation control mainly through experimental investigations. It is followed by a discussion about the overall limitations of current studies in the wind energy context, with a focus on a few studies that attempt to provide a global

  19. Time variations of oxygen emission lines and solar wind dynamic parameters in low latitude region

    Science.gov (United States)

    Jamlongkul, P.; Wannawichian, S.; Mkrtichian, D.; Sawangwit, U.; A-thano, N.

    2017-09-01

    Aurora phenomenon is an effect of collision between precipitating particles with gyromotion along Earth’s magnetic field and Earth’s ionospheric atoms or molecules. The particles’ precipitation occurs normally around polar regions. However, some auroral particles can reach lower latitude regions when they are highly energetic. A clear emission from Earth’s aurora is mostly from atomic oxygen. Moreover, the sun’s activities can influence the occurrence of the aurora as well. This work studies time variations of oxygen emission lines and solar wind parameters, simultaneously. The emission’s spectral lines were observed by Medium Resolution Echelle Spectrograph (MRES) along with 2.4 meters diameter telescope at Thai National Observatory, Intanon Mountain, Chiang Mai, Thailand. Oxygen (OI) emission lines were calibrated by Dech-Fits spectra processing program and Dech95 2D image processing program. The correlations between oxygen emission lines and solar wind dynamics will be analyzed. This result could be an evidence of the aurora in low latitude region.

  20. Flow Simulation of Modified Duct System Wind Turbines Installed on Vehicle

    Science.gov (United States)

    Rosly, N.; Mohd, S.; Zulkafli, M. F.; Ghafir, M. F. Abdul; Shamsudin, S. S.; Muhammad, W. N. A. Wan

    2017-10-01

    This study investigates the characteristics of airflow with a flow guide installed and output power generated by wind turbine system being installed on a pickup truck. The wind turbine models were modelled by using SolidWorks 2015 software. In order to investigate the characteristic of air flow inside the wind turbine system, a computer simulation (by using ANSYS Fluent software) is used. There were few models being designed and simulated, one without the rotor installed and another two with rotor installed in the wind turbine system. Three velocities being used for the simulation which are 16.7 m/s (60 km/h), 25 m/s (90 km/h) and 33.33 m/s (120 km/h). The study proved that the flow guide did give an impact to the output power produced by the wind turbine system. The predicted result from this study is the velocity of the air inside the ducting system of the present model is better that reference model. Besides, the flow guide implemented in the ducting system gives a big impact on the characteristics of the air flow.

  1. On-Line Flutter Prediction Tool for Wind Tunnel Flutter Testing using Parameter Varying Estimation Methodology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes to develop an on-line flutter prediction tool for wind tunnel model using the parameter varying estimation (PVE) technique to...

  2. On-Line Flutter Prediction Tool for Wind Tunnel Flutter Testing using Parameter Varying Estimation Methodology, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes to develop an on-line flutter prediction tool for wind tunnel model using the parameter varying estimation (PVE) technique to...

  3. Efficient material flow in mixed model assembly lines.

    Science.gov (United States)

    Alnahhal, Mohammed; Noche, Bernd

    2013-01-01

    In this study, material flow from decentralized supermarkets to stations in mixed model assembly lines using tow (tugger) trains is investigated. Train routing, scheduling, and loading problems are investigated in parallel to minimize the number of trains, variability in loading and in routes lengths, and line-side inventory holding costs. The general framework for solving these problems in parallel contains analytical equations, Dynamic Programming (DP), and Mixed Integer Programming (MIP). Matlab in conjunction with LP-solve software was used to formulate the problem. An example was presented to explain the idea. Results which were obtained in very short CPU time showed the effect of using time buffer among routes on the feasible space and on the optimal solution. Results also showed the effect of the objective, concerning reducing the variability in loading, on the results of routing, scheduling, and loading. Moreover, results showed the importance of considering the maximum line-side inventory beside the capacity of the train in the same time in finding the optimal solution.

  4. Parameter Analysis on Wind-Induced Vibration of UHV Cross-Rope Suspension Tower-Line

    Directory of Open Access Journals (Sweden)

    Xilai Li

    2017-01-01

    Full Text Available This paper analyzes the influences of important structural design parameters on the wind-induced response of cross-rope suspension tower-line. A finite element model of cross-rope suspension tower-line system is established, and the dynamic time-history analysis with harmonic wave superposition method is conducted. The two important structural design parameters such as initial guy pretension and sag-span ratio of suspension-rope are studied, as well as their influences on the three wind-induced vibration responses such as tensile force on guys, the reaction force on mast supports, and the along-wind displacement of the mast top; the results show that the value of sag-span ratio of suspension-rope should not be less than 1/9 and the value of guy pretension should be less than 30% of its design bearing capacity. On this occasion, the tension in guys and compression in masts would be maintained in smaller values, which can lead to a much more reasonable structure.

  5. A numerical study on the flow upstream of a wind turbine on complex terran

    DEFF Research Database (Denmark)

    Meyer Forsting, Alexander Raul; Bechmann, Andreas; Troldborg, Niels

    2016-01-01

    The interaction of a wind turbine with the upstream flow-field in complex and flat terrain is studied using Reynolds-averaged Navier-Stokes (RANS) simulations with a two equation turbulence closure. The complex site modelled is Perdigao (Portugal), where a turbine is located on one of two parallel...... the wind turbine wake trajectory which in turn governs the orientation of the induction zone...

  6. MHD effects of the solar wind flow around planets

    Directory of Open Access Journals (Sweden)

    H. K. Biernat

    2000-01-01

    Full Text Available The study of the interaction of the solar wind with magnetized and unmagnetized planets forms a central topic of space research. Focussing on planetary magnetosheaths, we review some major developments in this field. Magnetosheath structures depend crucially on the orientation of the interplanetary magnetic field, the solar wind Alfvén Mach number, the shape of the obstacle (axisymmetric/non-axisymmetric, etc., the boundary conditions at the magnetopause (low/high magnetic shear, and the degree of thermal anisotropy of the plasma. We illustrate the cases of Earth, Jupiter and Venus. The terrestrial magnetosphere is axisymmetric and has been probed in-situ by many spacecraft. Jupiter's magnetosphere is highly non-axisymmetric. Furthermore, we study magnetohydrodynamic effects in the Venus magnetosheath.

  7. Utilizing a vanadium redox flow battery to avoid wind power deviation penalties in an electricity market

    International Nuclear Information System (INIS)

    Turker, Burak; Arroyo Klein, Sebastian; Komsiyska, Lidiya; Trujillo, Juan José; Bremen, Lueder von; Kühn, Martin; Busse, Matthias

    2013-01-01

    Highlights: • Vanadium redox flow battery utilized for wind power grid integration was studied. • Technical and financial analyses at single wind farm level were performed. • 2 MW/6 MW h VRFB is suitable for mitigating power deviations for a 10 MW wind farm. • Economic incentives might be required in the short-term until the VRFB prices drop. - Abstract: Utilizing a vanadium redox flow battery (VRFB) for better market integration of wind power at a single wind farm level was evaluated. A model which combines a VRFB unit and a medium sized (10 MW) wind farm was developed and the battery was utilized to compensate for the deviations resulting from the forecast errors in an electricity market bidding structure. VRFB software model which was introduced in our previous paper was integrated with real wind power data, power forecasts and market data based on the Spanish electricity market. Economy of the system was evaluated by financial assessments which were done by considering the VRFB costs and the amount of deviation penalty payments resulting from forecast inaccuracies

  8. Experimental and Theoretical Study of Air Flow with Obstruction Through Test Section of Wind Tunnel

    Directory of Open Access Journals (Sweden)

    Hayder Kraidy Rashid

    2016-03-01

    Full Text Available This paper estimates the sound and flow generated by a turbulent air flow in a duct from the knowledge of mean quantities (average velocity and sound pressure level.The sound excitation by fluid flow through duct can be used to predict fluid behavior. This behavior can be carried out by discovering the relation between sound excitation and fluid flow parameters like Reynolds number, Strouhal number and frequencies of turbulent fluid flow. However, the fluid flow container stability has to be taken in account simultaneously with fluid flow effect on sound generation and propagation. The experimental system used in this work is air flow through subsonic wind tunnel duct.The sound pressure levels of air flows through test section of subsonic wind tunnel (at three air flow velocities2.5, 7.3 and 12.5 m/s respectively were carried out experimentally. The sound excitation or generation by air flow throughout the test section of subsonic wind tunnel without any obstruction can't be used to imagine the fluid behavior. To predict fluid flow properties,an infinite cylinder was immersed in order to obstruct the air flow and generate a new source of sound.This case is relevant to a wide range of engineering applications including aircraft landing gear, rail pantographs and automotive side-mirrors. Sound measurements have been taken in an anechoic room at Babylon University. ANSYS program software is used to simulate all experimental results.The experimental and theoretical data that were presented in this paper will give further insight into the underlying sound generation mechanism.In the presented work, the linkage between sound generation and CFD results using thepresented work results and ANSYS simulation results was done.The results discuss the effects of fluid flow parameters such as Reynolds and Strouhal numbers on the sound generation, propagation features and vice-versa. The results are compared with other researchers which give good agreements.

  9. Non-radial solar wind flows and IMF B z during 1973-2003

    Science.gov (United States)

    Pereira, Felix B.; Girish, T. E.

    2009-03-01

    The characteristics of latitudinal angles of solar wind flow ( θv) observed near earth have been studied during the period 1973-2003. The average magnitude of θv shows distinct enhancements during the declining and maximum phases of the sunspot cycles. A close association of B z component of IMF in the GSE system and the orientation of meridional flows in the solar wind is found which depends on the IMF sector polarity. This effect has been studied in typical geomagnetic storm periods. The occurrence of non-radial flows is also found to exhibit heliolatitudinal dependence during the years 1975 and 1985 as a characteristic feature of non-radial solar wind expansion from polar coronal holes.

  10. Effect of Damaged Mooring Line on Response of Spar with Wind Turbine

    Science.gov (United States)

    Seebai, T.; Sundaravadivelu, R.

    2012-02-01

    Spar platforms have several advantages for deploying wind turbines in offshore for depth beyond 120 m. The merit of spar platform is large range of topside payloads, favourable motions compared to other floating structures and minimum hull/deck interface. This paper addresses the effect of mooring line damages in responses of spar platform subjected to regular waves. A 1:100 scale model of the spar with taut (intact), taut (damaged) and slack (intact) mooring line configuration was studied in the wave basin (30 × 30 × 3 m) in Ocean Engineering Department of IIT Madras. The heave and surge accelerations along with mooring line tension was measured and used. The surge and heave RAO comparison for all three mooring line conditions shows that the effect of damaged mooring line in surge response is negligible whereas in heave response, taut (damaged) will behave similar to slack (intact) condition. The normalized mooring line tension comparison between taut intact and taut damaged configuration is also presented.

  11. Deflection estimation of a wind turbine blade using FBG sensors embedded in the blade bonding line

    International Nuclear Information System (INIS)

    Kim, Sang-Woo; Kang, Woo-Ram; Jeong, Min-Soo; Lee, In; Kwon, Il-Bum

    2013-01-01

    Estimating the deflection of flexible composite wind turbine blades is very important to prevent the blades from hitting the tower. Several researchers have used fiber Bragg grating (FBG) sensors—a type of optical fiber sensor (OFS)—to monitor the structural behavior of the blades. They can be installed on the surface and/or embedded in the interior of composites. However, the typical installation positions of OFSs present several problems, including delamination of sensing probes and a higher risk of fiber breakage during installation. In this study, we proposed using the bonding line between the shear web and spar cap as a new installation position of embedded OFSs for estimating the deflection of the blades. Laboratory coupon tests were undertaken preliminarily to confirm the strain measuring capability of embedded FBG sensors in adhesive layers, and the obtained values were verified by comparison with results obtained by electrical strain gauges and finite element analysis. We performed static loading tests on a 100 kW composite wind turbine blade to evaluate its deflections using embedded FBG sensors positioned in the bonding line. The deflections were estimated by classical beam theory considering a rigid body rotation near the tip of the blade. The evaluated tip deflections closely matched those measured by a linear variable differential transformer. Therefore, we verified the capability of embedded FBG sensors for evaluating the deflections of wind turbine blades. In addition, we confirmed that the bonding line between the shear web and spar cap is a practical location to embed the FBG sensors. (paper)

  12. Magnetosonic Waveguide Model of Solar Wind Flow Tubes A. K. ...

    Indian Academy of Sciences (India)

    structured in the form of flow tubes has also been supported by the HELIOS spacecraft observations (Thieme et al. 1990). The wave propagation characteristics in such a magnetically-structured and inhomogeneous medium have been investigated by ...

  13. 77 FR 485 - Wind Plant Performance-Public Meeting on Modeling and Testing Needs for Complex Air Flow...

    Science.gov (United States)

    2012-01-05

    ... of Energy Efficiency and Renewable Energy Wind Plant Performance--Public Meeting on Modeling and... validation techniques for complex flow phenomena in and around off- shore and on-shore utility-scale wind power plants. DOE is requesting this information to support the development of cost-effective wind power...

  14. Solder flow over fine line PWB surface finishes

    Energy Technology Data Exchange (ETDEWEB)

    Hosking, F.M.; Hernandez, C.L.

    1998-08-01

    The rapid advancement of interconnect technology has stimulated the development of alternative printed wiring board (PWB) surface finishes to enhance the solderability of standard copper and solder-coated surfaces. These new finishes are based on either metallic or organic chemistries. As part of an ongoing solderability study, Sandia National Laboratories has investigated the solder flow behavior of two azole-based organic solderability preservations, immersion Au, immersion Ag, electroless Pd, and electroless Pd/Ni on fine line copper features. The coated substrates were solder tested in the as-fabricated and environmentally-stressed conditions. Samples were processed through an inerted reflow machine. The azole-based coatings generally provided the most effective protection after aging. Thin Pd over Cu yielded the best wetting results of the metallic coatings, with complete dissolution of the Pd overcoat and wetting of the underlying Cu by the flowing solder. Limited wetting was measured on the thicker Pd and Pd over Ni finishes, which were not completely dissolved by the molten solder. The immersion Au and Ag finishes yielded the lowest wetted lengths, respectively. These general differences in solderability were directly attributed to the type of surface finish which the solder came in contact with. The effects of circuit geometry, surface finish, stressing, and solder processing conditions are discussed.

  15. Probabilistic Approach to Optimizing Active and Reactive Power Flow in Wind Farms Considering Wake Effects

    Directory of Open Access Journals (Sweden)

    Yong-Cheol Kang

    2013-10-01

    Full Text Available This paper presents a novel probabilistic optimization algorithm for simultaneous active and reactive power dispatch in power systems with significant wind power integration. Two types of load and wind-speed uncertainties have been assumed that follow normal and Weibull distributions, respectively. A PV bus model for wind turbines and the wake effect for correlated wind speed are used to achieve accurate AC power flow analysis. The power dispatch algorithm for a wind-power integrated system is modeled as a probabilistic optimal power flow (P-OPF problem, which is operated through fixed power factor control to supply reactive power. The proposed P-OPF framework also considers emission information, which clearly reflects the impact of the energy source on the environment. The P-OPF was tested on a modified IEEE 118-bus system with two wind farms. The results show that the proposed technique provides better system operation performance evaluation, which is helpful in making decisions about power system optimal dispatch under conditions of uncertainty.

  16. 3D Modeling of Forbidden Line Emission in the Binary Wind Interaction Region of Eta Carinae

    Science.gov (United States)

    Madura, Thomas; Gull, T. R.; Owocki, S.; Okazaki, A. T.; Russell, C. M. P.

    2010-01-01

    We present recent work using three-dimensional (3D) Smoothed Particle Hydrodynamics (SPH) simulations to model the high ([Fe III], [Ar III], [Ne III] and [S III]) and low ([Fe II], [Ni II]) ionization forbidden emission lines observed in Eta Carinae using the HST/STIS. These structures are interpreted as the time-averaged, outer extensions of the primary wind and the wind-wind interaction region directly excited by the FUV of the hot companion star of this massive binary system. We discuss how analyzing the results of the 3D SPH simulations and synthetic slit spectra and comparing them to the spectra obtained with the HST/STIS helps us determine the absolute orientation of the binary orbit and helps remove the degeneracy inherent to models based solely on the observed RXTE X-ray light curve. A key point of this work is that spatially resolved observations like those with HST/STIS and comparison to 3D models are necessary to determine the alignment or misalignment of the orbital angular momentum axis with the Homunculus, or correspondingly, the alignment of the orbital plane with the Homunculus skirt.

  17. Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed

    Science.gov (United States)

    Zhang, Xin; Huang, Yong; Wang, WanBo; Wang, XunNian; Li, HuaXing

    2014-06-01

    The present paper described an experimental investigation of separation control of an Unmanned Aerial Vehicle (UAV) at high wind speeds. The plasma actuator was based on Dielectric Barrier Discharge (DBD) and operated in a steady manner. The flow over a wing of UAV was performed with smoke flow visualization in the ϕ0.75 m low speed wind tunnel to reveal the flow structure over the wing so that the locations of plasma actuators could be optimized. A full model of the UAV was experimentally investigated in the ϕ3.2 m low speed wind tunnel using a six-component internal strain gauge balance. The effects of the key parameters, including the locations of the plasma actuators, the applied voltage amplitude and the operating frequency, were obtained. The whole test model was made of aluminium and acted as a cathode of the actuator. The results showed that the plasma acting on the surface of UAV could obviously suppress the boundary layer separation and reduce the model vibration at the high wind speeds. It was found that the maximum lift coefficient of the UAV was increased by 2.5% and the lift/drag ratio was increased by about 80% at the wind speed of 100 m/s. The control mechanism of the plasma actuator at the test configuration was also analyzed.

  18. Characterization of the unsteady flow in the nacelle region of a modern wind turbine

    DEFF Research Database (Denmark)

    Zahle, Frederik; Sørensen, Niels N.

    2011-01-01

    A three-dimensional Navier–Stokes solver has been used to investigate the flow in the nacelle region of a wind turbine where anemometers are typically placed to measure the flow speed and the turbine yaw angle. A 500 kW turbine was modelled with rotor and nacelle geometry in order to capture...... the complex separated flow in the blade root region of the rotor. A number of steady state and unsteady simulations were carried out for wind speeds ranging from 6 m s−1 to 16 m s−1 as well as two yaw and tilt angles. The flow in the nacelle region was found to be highly unsteady, dominated by unsteady vortex...... anemometry showed significant dependence on both yaw and tilt angles with yaw errors of up to 10 degrees when operating in a tilted inflow. Copyright © 2010 John Wiley & Sons, Ltd....

  19. A Line Weighted Frequency Droop Controller for Decentralized Enforcement of Transmission Line Power Flow Constraints in Inverter-Based Networks

    Energy Technology Data Exchange (ETDEWEB)

    Ainsworth, Nathan G [ORNL; Grijalva, Prof. Santiago [Georgia Institute of Technology, Atlanta

    2013-01-01

    Recent works have shown that networks of voltagesource inverters implementing frequency droop control may be analyzed as consensus-like networks. Based on this understanding, we show that enforcement of network line power flows can be viewed as an edge-preservation problem in a -disk dynamic interaction graph. Inspired by other works solving similar problems in other domains, we propose a line weighted frequency droop controller such that a network of all active buses implementing this controller enforces the specified line power flow constraints without need for communication. We provide simulation results verifying that our proposed controller limits line power to enforce constraints, and otherwise acts as a traditional droop controller.

  20. Numerical simulation of flows around deformed aircraft model in a wind tunnel

    Science.gov (United States)

    Lysenkov, A. V.; Bosnyakov, S. M.; Glazkov, S. A.; Gorbushin, A. R.; Kuzmina, S. I.; Kursakov, I. A.; Matyash, S. V.; Ishmuratov, F. Z.

    2016-10-01

    To obtain accurate data of calculation method error requires detailed simulation of the experiment in wind tunnel with keeping all features of the model, installation and gas flow. Two examples of such detailed data comparison are described in this paper. The experimental characteristics of NASA CRM model obtained in the ETW wind tunnel (Cologne, Germany), and CFD characteristics of this model obtained with the use of EWT-TsAGI application package are compared. Following comparison is carried out for an airplane model in the T-128 wind tunnel (TsAGI, Russia). It is seen that deformation influence on integral characteristics grows with increasing Re number and, accordingly, the dynamic pressure. CFD methods application for problems of experimental research in the wind tunnel allows to separate viscosity and elasticity effects.

  1. Partial analysis of wind power limit in an electric micro system using continuation power flow

    International Nuclear Information System (INIS)

    Fiallo Guerrero, Jandry; Santos Fuentefria, Ariel; Castro Fernández, Miguel

    2013-01-01

    The wind power insertion in the power system is an important issue and can create some instability problems in voltage and system frequency due to stochastic origin of wind. Know the Wind Power Limit that can insert in an electric grid without losing stability is a very important matter. Existing in bibliography a few methods for calculation of wind power limit, some of them are based in static constrains, an example is a method based in a continuation power flow analysis. In the present work the method is applied in an electric micro system formed when the system is disconnected of the man grid, the main goal was prove the method in a weak and island network. The software used in the simulations was the Power System Analysis Toolbox (PSAT). (author)

  2. Calibration of the Flow in the Test Section of the Research Wind Tunnel at DST Group

    Science.gov (United States)

    2015-10-01

    the tunnel. The calibration data are presented and analysed and explanations of flow behaviour are given. 2. Mean-Velocity Measurements 2.1...1073. Defence Science and Technology Organisation , Melbourne, Australia. Erm, L. P. 2003 Calibration of the flow in the extended test section...of the low-speed wind tunnel at DSTO. DSTO-TR-1384. Defence Science and Technology Organisation , Melbourne, Australia. Erm, L. P. 2015

  3. Study on blade surface flow around wind turbine by using LDV measurements

    Science.gov (United States)

    Phengpom, Tinnapob; Kamada, Yasunari; Maeda, Takao; Murata, Junsuke; Nishimura, Shogo; Matsuno, Tasuku

    2015-04-01

    This paper has attempted to study a mechanism of three-dimensional flow around a horizontal axis wind turbine (HAWT) rotor blade. An experimental study of the flow phenomenon in the vicinity of the wind turbine blade is a challenging endeavor. In this research, the HAWT model with 2.4 m diameter was tested in the large wind tunnel. The flow around the rotating blade surface was measured simultaneously for three velocity components, and two probes were used for the synchronized measurement of three-dimensional flow components. The local velocity was detected for the single seeding particle measured in the point where three pairs of laser beams intersected. Blade sections of interest in this study are composed of radial positions r/R = 0.3, 0.5 and 0.7. Optimum and low tip speed ratio flow characteristics were also compared. The velocity flow vector, skin friction coefficient and bound circulation were calculated from LDV measurements, and the experimental research showed reasonably and clearly the experimental results.

  4. Granger causality estimate of information flow in temperature fields is consistent with wind direction

    Czech Academy of Sciences Publication Activity Database

    Jajcay, Nikola; Hlinka, Jaroslav; Hartman, David; Paluš, Milan

    2014-01-01

    Roč. 16, - (2014), EGU2014-12768 ISSN 1607-7962. [EGU General Assembly /11./. 27.04.2014-02.05.2014, Vienna] Institutional support: RVO:67985807 Keywords : Granger causality * climate * information flow * surface air temperature * wind Subject RIV: BB - Applied Statistics, Operational Research

  5. Influence of omni-directional guide vane on the performance of cross-flow rotor for urban wind energy

    Science.gov (United States)

    Wicaksono, Yoga Arob; Tjahjana, Dominicus Danardono Dwi Prija; Hadi, Syamsul

    2018-02-01

    Vertical axis wind turbine like cross-flow rotor have some advantage there are, high self-starting torque, low noise, and high stability; so, it can be installed in the urban area to produce electricity. But, the urban area has poor wind condition, so the cross-flow rotor needs a guide vane to increase its performance. The aim of this study is to determine experimentally the effect of Omni-Directional Guide Vane (ODGV) on the performance of a cross-flow wind turbine. Wind tunnel experiment has been carried out for various configurations. The ODGV was placed around the cross-flow rotor in order to increase ambient wind environment of the wind turbine. The maximum power coefficient is obtained as Cpmax = 0.125 at 60° wind direction. It was 21.46% higher compared to cross-flow wind turbine without ODGV. This result showed that the ODGV able to increase the performance of the cross-flow wind turbine.

  6. Investigation of gas particle flow in an erosion wind tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Tabakoff, W.; Hamed, A.; Beacher, B.

    1983-04-01

    Trajectories of small particles approaching the test specimen in an erosion tunnel are analytically determined. The two-dimensional equations of motion are solved for a spherical particle under the sole influence of aerodynamic drag. The two-dimensional gradients of gas properties in the flow field are determined by a numerical solution of the equations describing a compressible inviscid fluid. At one inlet condition, the trajectories are computed for coal ash particles of various sizes approaching test specimens at several orientations. Trends are identified in the approaching characteristics that may be related to the observed erosion. The results indicate that, for ash particles with diameters less than 10 ..mu..m, significant numbers are deflected away from the specimen. These particles would otherwise impact with the specimen if they had to resist the turning effect of the flow field.

  7. Line-driven disk winds in active galactic nuclei: The critical importance of ionization and radiative transfer

    Energy Technology Data Exchange (ETDEWEB)

    Higginbottom, Nick; Knigge, Christian; Matthews, James H. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ (United Kingdom); Proga, Daniel [Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002 (United States); Long, Knox S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Sim, Stuart A., E-mail: nick_higginbottom@fastmail.fm [School of Mathematics and Physics, Queens University Belfast, University Road, Belfast, BT7 1NN (United Kingdom)

    2014-07-01

    Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGNs) and quasi-stellar objects (QSOs). These outflows also represent a natural form of feedback between the central supermassive black hole and its host galaxy. The mechanism for driving this mass loss remains unknown, although radiation pressure mediated by spectral lines is a leading candidate. Here, we calculate the ionization state of, and emergent spectra for, the hydrodynamic simulation of a line-driven disk wind previously presented by Proga and Kallman. To achieve this, we carry out a comprehensive Monte Carlo simulation of the radiative transfer through, and energy exchange within, the predicted outflow. We find that the wind is much more ionized than originally estimated. This is in part because it is much more difficult to shield any wind regions effectively when the outflow itself is allowed to reprocess and redirect ionizing photons. As a result, the calculated spectrum that would be observed from this particular outflow solution would not contain the ultraviolet spectral lines that are observed in many AGN/QSOs. Furthermore, the wind is so highly ionized that line driving would not actually be efficient. This does not necessarily mean that line-driven winds are not viable. However, our work does illustrate that in order to arrive at a self-consistent model of line-driven disk winds in AGN/QSO, it will be critical to include a more detailed treatment of radiative transfer and ionization in the next generation of hydrodynamic simulations.

  8. Measurement Techniques for Flow Diagnostic in ITAM Impulse Wind Tunnels

    Science.gov (United States)

    2010-04-01

    inhomogeneity is focused by a lens in the plane of the Foucault knife where the slot image is formed. The so- called Toepler devices based on this principle...substantial constraints. In particular, the use of devices with the Foucault knife is ineffective in hypersonic flows, which are characterized by extremely...visualization transparent (AVT) instead of the Foucault knife [26, 27]. In this case, the transparent is made of a phototropic material (e.g., silica

  9. MHD-IPS analysis of relationship among solar wind density, temperature, and flow speed

    Science.gov (United States)

    Hayashi, Keiji; Tokumaru, Munetoshi; Fujiki, Ken'ichi

    2016-08-01

    The solar wind properties near the Sun are a decisive factor of properties in the rest of heliosphere. As such, determining realistic plasma density and temperature near the Sun is very important in models for solar wind, specifically magnetohydrodynamics (MHD) models. We had developed a tomographic analysis to reconstruct three-dimensional solar wind structures that satisfy line-of-sight-integrated solar wind speed derived from the interplanetary scintillation (IPS) observation data and nonlinear MHD equations simultaneously. In this study, we report a new type of our IPS-MHD tomography that seeks three-dimensional MHD solution of solar wind, matching additionally near-Earth and/or Ulysses in situ measurement data for each Carrington rotation period. In this new method, parameterized relation functions of plasma density and temperature at 50 Rs are optimized through an iterative forward model minimizing discrepancy with the in situ measurements. Satisfying three constraints, the derived 50 Rs maps of plasma quantities provide realistic observation-based information on the state of solar wind near the Sun that cannot be well determined otherwise. The optimized plasma quantities exhibit long-term variations over the solar cycles 21 to 24. The differences in plasma quantities derived from the optimized and original IPS-MHD tomography exhibit correlations with the source-surface magnetic field strength, which can in future give new quantitative constrains and requirements to models of coronal heating and acceleration.

  10. Relation of solar wind fluctuations to differential flow between protons and alphas

    Science.gov (United States)

    Neugebauer, M.

    1974-01-01

    An analysis is made of the difference between the alpha particle and proton flow velocities in the solar wind as observed by the OGO 5 satellite. The alpha and proton velocities from each of 962 spectral scans are compared with the variance of 32 solar wind flux measurements made during the scans. The average velocity difference is plotted for each of 10 logarithmic variance intervals and is seen to decrease and approach zero when the variance is high. It is shown that such an anticorrelation may be due to the fact the wave/particle interactions provide the drag force between two streams of different velocity in a collisionless plasma.

  11. On the flow, thermal field and winds along the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Shenoi, S.S.C.

    January 1991; in revised form 30 July 1991 ; accepted 5 March 1992) Abstract--Short duration current meter recordings during May 1984, March 1986 and November 1986 along with wind and hydrographic data at a point (15°08'N and 73°16'E) in the western... these moorings were restricted to short durations of 10-15 days only. In this paper we present the general features of the measured flow and its relationship with the local wind and the density (thermal) structure. A description of the time-dependent motions...

  12. Using Free Flow Energy Cumulation in Wind and Hydro Power Production

    Directory of Open Access Journals (Sweden)

    Lev Ktitorov

    2016-09-01

    Full Text Available When approaching a conventional wind turbine, the air flow is slowed down and widened. This results in a loss of turbine efficiency. In order to exploit wind or water flow power as effectively as possible, it was suggested that the turbine should be placed inside a shroud, which consists of 4 wing-shaped surfaces. Two internal airfoils improve the turbine performance by speeding up the flow acting on the turbine blades, two external wings create a field of low pressure behind the turbine, thus, helping to draw more mass flow to the turbine and avoid the loss of efficiency due to flow deceleration.  The system accumulates kinetic energy of the flow in a small volume where the smaller (and, therefore, cheaper turbine can be installed. A smaller system can be installed inside the bigger one, which would help to accumulate even more kinetic energy on the turbine. We call this method the kinetic energy summation with local flow redistribution. Both experiments and CFD simulations demonstrate a significant increase in velocity and generated mechanical power in comparison of those for a bare turbine.

  13. Perturbations of the solar wind flow by radial and latitudinal pick-up ion pressure gradients

    Directory of Open Access Journals (Sweden)

    H. J. Fahr

    2004-06-01

    Full Text Available It has been found that pick-up ions at their dynamical incorporation into the solar wind modify the original conditions of the asymptotic solar wind plasma flow. In this respect, it has meanwhile been revealed in many papers that these type of solar wind modifications, i.e. deceleration and decrease of effective Mach number, are not only due to the pick-up ion loading effects, but also to the action of pick-up ion pressure gradients. Up to now only the effects of radial pick-up ion pressure gradients were considered, however, analogously but latitudinal pressure gradients also appear to be important. Here we study the effects of radial and latitudinal pick-up ion pressure gradients, occurring especially during solar minimum conditions at mid-latitude regions where slow solar wind streams change to fast solar wind streams. First, we give estimates of the latitudinal wind components connected with these gradients, and then after revealing its importance, present a more quantitative calculation of solar wind velocity and density perturbations resulting from these pressure forces. It is shown that the relative density perturbations near and in the ecliptic increase with radial distance and thus may well explain the measured non-spherically symmetric density decrease with distance. We also show that the solar wind decelerations actually seen with Voyager-1/2 are in conciliation with interstellar hydrogen densities of nH∞≥0.1cm-3, in contrast to earlier claims for nH∞=0.05cm-3.

  14. Perturbations of the solar wind flow by radial and latitudinal pick-up ion pressure gradients

    Directory of Open Access Journals (Sweden)

    H. J. Fahr

    2004-06-01

    Full Text Available It has been found that pick-up ions at their dynamical incorporation into the solar wind modify the original conditions of the asymptotic solar wind plasma flow. In this respect, it has meanwhile been revealed in many papers that these type of solar wind modifications, i.e. deceleration and decrease of effective Mach number, are not only due to the pick-up ion loading effects, but also to the action of pick-up ion pressure gradients. Up to now only the effects of radial pick-up ion pressure gradients were considered, however, analogously but latitudinal pressure gradients also appear to be important. Here we study the effects of radial and latitudinal pick-up ion pressure gradients, occurring especially during solar minimum conditions at mid-latitude regions where slow solar wind streams change to fast solar wind streams. First, we give estimates of the latitudinal wind components connected with these gradients, and then after revealing its importance, present a more quantitative calculation of solar wind velocity and density perturbations resulting from these pressure forces. It is shown that the relative density perturbations near and in the ecliptic increase with radial distance and thus may well explain the measured non-spherically symmetric density decrease with distance. We also show that the solar wind decelerations actually seen with Voyager-1/2 are in conciliation with interstellar hydrogen densities of nH∞≥0.1cm-3, in contrast to earlier claims for nH∞=0.05cm-3.

  15. MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub-Alfvenic Flow

    Science.gov (United States)

    Farrugia, C. J.; Lugaz, N.; Alm, L.; Vasquez, B. J.; Argall, M. R.; Kucharek, H.; Matsui, H.; Torbert, R. B.; Lavraud, B.; Le Contel, O.; Shuster, J. R.; Burch, J. L.; Khotyaintsev, Y. V.; Giles, B. L.; Fuselier, S. A.; Gershman, D. J.; Ergun, R.; Eastwood, J. P.; Cohen, I. J.; Dorelli, J.; Lindqvist, P. A.; Strangeway, R. J.; Russell, C. T.; Marklund, G. T.; Paulson, K.; Petrinec, S.; Phan, T.; Pollock, C.

    2017-12-01

    We present MMS) observations during two dayside magnetopause crossingsunder hitherto unexamined conditions: (i) when the bow shock is weakening and the solar wind transitioning to sub-Alfvenic flow, and (ii) when it is reforming. Interplanetary conditions consist of a magnetic cloud with (i) a strong B ( 20 nT) pointing south, and (ii) a density profile with episodic decreases to values of 0.3 /cc followed by moderate recovery. During the crossings he magnetosheath magnetic field is stronger than the magnetosphere field by a factor of 2.2. As a result, during the outbound crossing through the ion diffusion region, MMS observed an inversion of relative positions of the X and stagnation (S) lines from that typically the case: the S line was closer to the magnetosheath side. The S-line appears in the form of a slow expansion fan near which most of the energy dissipation is taking place. While in the magnetosphere between the crossings, MMS observed strong field and flow perturbations, which we argue to be due kinetic Alfvén waves.During the reconnection interval, whistler mode waves generated by an electron temperature anisotropy (Tperp>Tpar) were observed. Another aim of the paper isto distinguish bow shock-induced field and flow perturbations from reconnection-related signatures.The high resolution MMS data together with 2D hybrid simulations of bow shock dynamics helped us to distinguish between the two sources. We show examples of bow shock-related effects (such as heating) and reconnection effects such as accelerated flows satisfying the Walen relation.

  16. Characterizing the turbulent porosity of stellar wind structure generated by the line-deshadowing instability

    Science.gov (United States)

    Owocki, Stanley P.; Sundqvist, Jon O.

    2018-03-01

    We analyse recent 2D simulations of the non-linear evolution of the line-deshadowing instability (LDI) in hot-star winds, to quantify how the associated highly clumped density structure can lead to a `turbulent porosity' reduction in continuum absorption and/or scattering. The basic method is to examine the statistical variations of mass column as a function of path length, and fit these to analytic forms that lead to simple statistical scalings for the associated mean extinction. A key result is that one can characterize porosity effects on continuum transport in terms of a single `turbulent porosity length', found here to scale as H ≈ (fcl - 1)a, where fcl ≡ 〈ρ2〉/〈ρ〉2 is the clumping factor in density ρ, and a is the density autocorrelation length. For continuum absorption or scattering in an optically thick layer, we find the associated effective reduction in opacity scales as ˜ 1/√{1+τ_H}, where τH ≡ κρH is the local optical thickness of this porosity length. For these LDI simulations, the inferred porosity lengths are small, only about a couple per cent of the stellar radius, H ≈ 0.02R*. For continuum processes like bound-free absorption of X-rays that are only marginally optically thick throughout the full stellar wind, this implies τH ≪ 1, and thus that LDI-generated porosity should have little effect on X-ray transport in such winds. The formalism developed here could however be important for understanding the porous regulation of continuum-driven, super-Eddington outflows from luminous blue variables.

  17. Coupled simulations and comparison with multi-lidar measurements of the wind flow over a double-ridge

    DEFF Research Database (Denmark)

    Veiga Rodrigues, C.; Palma, J.M.L.M.; Vasiljevic, Nikola

    2016-01-01

    The wind flow over a double-ridge site has been numerically simulated with a nested model- chain coupling, down to horizontal resolutions of 40 m. The results were compared with field measurements attained using a triple-lidar instrument, the long-range WindScanner system, which allowed measureme......The wind flow over a double-ridge site has been numerically simulated with a nested model- chain coupling, down to horizontal resolutions of 40 m. The results were compared with field measurements attained using a triple-lidar instrument, the long-range WindScanner system, which allowed...

  18. Monte Carlo simulations of the detailed iron absorption line profiles from thermal winds in X-ray binaries

    Science.gov (United States)

    Tomaru, Ryota; Done, Chris; Odaka, Hirokazu; Watanabe, Shin; Takahashi, Tadayuki

    2018-05-01

    Blueshifted absorption lines from highly ionized iron are seen in some high inclination X-ray binary systems, indicating the presence of an equatorial disc wind. This launch mechanism is under debate, but thermal driving should be ubiquitous. X-ray irradiation from the central source heats disc surface, forming a wind from the outer disc where the local escape velocity is lower than the sound speed. The mass-loss rate from each part of the disc is determined by the luminosity and spectral shape of the central source. We use these together with an assumed density and velocity structure of the wind to predict the column density and ionization state, then combine this with a Monte Carlo radiation transfer to predict the detailed shape of the absorption (and emission) line profiles. We test this on the persistent wind seen in the bright neutron star binary GX 13+1, with luminosity L/LEdd ˜ 0.5. We approximately include the effect of radiation pressure because of high luminosity, and compute line features. We compare these to the highest resolution data, the Chandra third-order grating spectra, which we show here for the first time. This is the first physical model for the wind in this system, and it succeeds in reproducing many of the features seen in the data, showing that the wind in GX13+1 is most likely a thermal-radiation driven wind. This approach, combined with better streamline structures derived from full radiation hydrodynamic simulations, will allow future calorimeter data to explore the detail wind structure.

  19. Monte-Carlo simulations of the detailed iron absorption line profiles from thermal winds in X-ray binaries

    Science.gov (United States)

    Tomaru, Ryota; Done, Chris; Odaka, Hirokazu; Watanabe, Shin; Takahashi, Tadayuki

    2018-02-01

    Blue-shifted absorption lines from highly ionised iron are seen in some high inclination X-ray binary systems, indicating the presence of an equatorial disc wind. This launch mechanism is under debate, but thermal driving should be ubiquitous. X-ray irradiation from the central source heats disc surface, forming a wind from the outer disc where the local escape velocity is lower than the sound speed. The mass loss rate from each part of the disc is determined by the luminosity and spectral shape of the central source. We use these together with an assumed density and velocity structure of the wind to predict the column density and ionisation state, then combine this with a Monte-Carlo radiation transfer to predict the detailed shape of the absorption (and emission) line profiles. We test this on the persistent wind seen in the bright neutron star binary GX 13+1, with luminosity L/LEdd ˜ 0.5. We approximately include the effect of radiation pressure because of high luminosity, and compute line features. We compare these to the highest resolution data, the Chandra third order grating spectra, which we show here for the first time. This is the first physical model for the wind in this system, and it succeeds in reproducing many of the features seen in the data, showing that the wind in GX13+1 is most likely a thermal-radiation driven wind. This approach, combined with better streamline structures derived from full radiation hydrodynamic simulations, will allow future calorimeter data to explore the detail wind structure.

  20. Robust optimization-based DC optimal power flow for managing wind generation uncertainty

    Science.gov (United States)

    Boonchuay, Chanwit; Tomsovic, Kevin; Li, Fangxing; Ongsakul, Weerakorn

    2012-11-01

    Integrating wind generation into the wider grid causes a number of challenges to traditional power system operation. Given the relatively large wind forecast errors, congestion management tools based on optimal power flow (OPF) need to be improved. In this paper, a robust optimization (RO)-based DCOPF is proposed to determine the optimal generation dispatch and locational marginal prices (LMPs) for a day-ahead competitive electricity market considering the risk of dispatch cost variation. The basic concept is to use the dispatch to hedge against the possibility of reduced or increased wind generation. The proposed RO-based DCOPF is compared with a stochastic non-linear programming (SNP) approach on a modified PJM 5-bus system. Primary test results show that the proposed DCOPF model can provide lower dispatch cost than the SNP approach.

  1. Blob formation and acceleration in the solar wind: role of converging flows and viscosity

    Directory of Open Access Journals (Sweden)

    G. Lapenta

    2008-10-01

    Full Text Available The effect of viscosity and of converging flows on the formation of blobs in the slow solar wind is analysed by means of resistive MHD simulations. The regions above coronal streamers where blobs are formed (Sheeley et al., 1997 are simulated using a model previously proposed by Einaudi et al. (1999. The result of our investigation is two-fold. First, we demonstrate a new mechanism for enhanced momentum transfer between a forming blob and the fast solar wind surrounding it. The effect is caused by the longer range of the electric field caused by the tearing instability forming the blob. The electric field reaches into the fast solar wind and interacts with it, causing a viscous drag that is global in nature rather than local across fluid layers as it is the case in normal uncharged fluids (like water. Second, the presence of a magnetic cusp at the tip of a coronal helmet streamer causes a converging of the flows on the two sides of the streamer and a direct push of the forming island by the fast solar wind, resulting in a more efficient momentum exchange.

  2. SNAKE LINE ANALYSIS FOR LAHAR FLOW WARNING SYSTEM (CASE STUDY IN PUTIH RIVER, MOUNT MERAPI

    Directory of Open Access Journals (Sweden)

    Nina Yulinsa

    2015-01-01

    Full Text Available Lahar flow in the region of Mount Merapi after an eruption of 2010 is still considered potentially to happen and threat the region along the river from the upstream. The development of warning criteria against the potential occurrence of lahar flow is a thing that should be done continuously to accommodate dynamics data availability (rainfall data and lahar flow occurrence data, although with limited data. This study aims to develop lahar warning system applying snake line as a rain phenomenon in Putih catchment area which will affect the occurrence of lahar flow and to evaluate the success rate of snake line for deciding the warning system. This study used the main reference from Guidelines for Development of Warning and Evacuation System against Sediment Disasters in Developing Countries released by Ministry of Land, Infrastructure and Transport Infrastructure Development Institute – Japan (2004. This research was conducted through several stages, i.e. secondary data collection in the form of rainfall data, lahar flow occurrence data, making correlation graph between rainfall intensity and working rainfall, determination of critical line, warning line and evacuation line. The results show that standard rainfall for warning and evacuation alert in Putih River are 22 mm, and 49 mm, respectively. The accuracy of warning criteria and the evacuation criteria against snake line for warning line is 30%, evacuation line is 61% and the critical line is 83%. The behavior of snake line that indicates lahar flow occurrence in Putih River forming an angle of 40o up to 45o.

  3. Numerical analysis of the flow around the Bach-type Savonius wind turbine

    International Nuclear Information System (INIS)

    Kacprzak, K; Sobczak, K

    2014-01-01

    The performance of the Bach-type Savonius wind turbine with a constant cross-section is examined by means of quasi 2D and 3D flow predictions obtained from ANSYS CFX. Simulations were performed in a way allowing for a comparison with the wind tunnel data presented by Kamoji et al. The comparison with the experiment has revealed that 2D solutions give much higher deviation from the reference data than the 3D ones, which guarantees a good solution quality. It can be stated that even simplified (lack of laminar-turbulence transition modelling and a coarser mesh) 3D simulations can yield more accurate results than complex 2D solutions for turbines with a low aspect ratio. The paper also presents a systematic analysis of the most characteristic flow structures which are identified in the rotor.

  4. Numerical analysis of the flow around the Bach-type Savonius wind turbine

    Science.gov (United States)

    Kacprzak, K.; Sobczak, K.

    2014-08-01

    The performance of the Bach-type Savonius wind turbine with a constant cross-section is examined by means of quasi 2D and 3D flow predictions obtained from ANSYS CFX. Simulations were performed in a way allowing for a comparison with the wind tunnel data presented by Kamoji et al. The comparison with the experiment has revealed that 2D solutions give much higher deviation from the reference data than the 3D ones, which guarantees a good solution quality. It can be stated that even simplified (lack of laminar-turbulence transition modelling and a coarser mesh) 3D simulations can yield more accurate results than complex 2D solutions for turbines with a low aspect ratio. The paper also presents a systematic analysis of the most characteristic flow structures which are identified in the rotor.

  5. What's in the Wind? Determining the Properties of Outflowing Gas in Powerful Broad Absorption Line Quasars

    Science.gov (United States)

    Leighly, Karen

    2017-08-01

    A significant fraction of quasars exhibits blueshifted broadabsorption lines (BALs) in their rest-UV spectra, indicating powerfuloutflows emerging from the central engine. These outflows may removeangular momentum to enable black hole growth, enrich the intergalacticmedium with metals, and trigger quenching of star formation ingalaxies. Despite years of study, the physical conditions of theoutflowing gas are poorly understood. The handful of objects that havebeen subjected to detailed analysis are atypical and characterized byrelatively narrow lines where blending is unimportant. However,investigating more powerful BAL quasars will give us better insightinto the types of outflows much more likely to impact galaxyevolution.SimBAL is a novel spectral synthesis fitting method for BAL quasarsthat uses Bayesian model calibration to compare synthetic to observedspectra. With the model inputs of ionization parameter, columndensity, and covering fraction specified, the gas properties givingrise to the BAL features can be determined. We propose to applySimBAL to archival spectra of a sample of 14 luminous BAL quasars to characterize their bulk outflow properties as a function of velocityfor the first time. Our results will show the range of parameterstypical of powerful outflows, an essential step towards constrainingthe physics behind quasar winds and thus their impact on theirenvironments.

  6. Asymmetrical flow field-flow fractionation with on-line detection for drug transfer studies: a feasibility study

    DEFF Research Database (Denmark)

    Hinna, A.; Steiniger, F.; Hupfeld, S.

    2014-01-01

    Knowledge about drug retention within colloidal carriers is of uppermost importance particularly if drug targeting is anticipated. The aim of the present study was to evaluate asymmetrical flow field-flow fractionation (AF4) with on-line UV/VIS drug quantification for its suitability to determine......-line absorbance measurements was found feasible for the chosen model drug, but careful (re-) evaluation of turbidity effects is crucial for other drug and carrier combinations....

  7. Millimeter-Gap Magnetically Insulated Transmission Line Power Flow Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Hutsel, Brian Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stoltzfus, Brian S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fowler, William E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); LeChien, Keith R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mazarakis, Michael G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Moore, James K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mulville, Thomas D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Savage, Mark E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stygar, William A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); McKenney, John L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jones, Peter A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); MacRunnels, Diego J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Long, Finis W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Porter, John L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    An experiment platform has been designed to study vacuum power flow in magnetically insulated transmission lines (MITLs). The platform was driven by the 400-GW Mykonos-V accelerator. The experiments conducted quantify the current loss in a millimeter-gap MITL with respect to vacuum conditions in the MITL for two different gap distances, 1.0 and 1.3 mm. The current loss for each gap was measured for three different vacuum pump down times. As a ride along experiment, multiple shots were conducted with each set of hardware to determine if there was a conditioning effect to increase current delivery on subsequent shots. The experiment results revealed large differences in performance for the 1.0 and 1.3 mm gaps. The 1.0 mm gap resulted in current loss of 40%-60% of peak current. The 1.3 mm gap resulted in current losses of less than 5% of peak current. Classical MITL models that neglect plasma expansion predict that there should be zero current loss, after magnetic insulation is established, for both of these gaps. The experiments result s indicate that the vacuum pressure or pump down time did not have a significant effect on the measured current loss at vacuum pressures between 1e-4 and 1e-5 Torr. Additionally, there was not repeatable evidence of a conditioning effect that reduced current loss for subsequent full-energy shots on a given set of hardware. It should be noted that the experiments conducted likely did not have large loss contributions due to ion emission from the anode due to the relatively small current densi-ties (25-40 kA/cm) in the MITL that limited the anode temperature rise due to ohmic heating. The results and conclusions from these experiments may have limited applicability to MITLs of high current density (>400 kA/cm) used in the convolute and load region of the Z which experience temperature increases of >400° C and generate ion emission from anode surfaces.

  8. Optical Flow for Flight and Wind Tunnel Background Oriented Schlieren Imaging

    Science.gov (United States)

    Smith, Nathanial T.; Heineck, James T.; Schairer, Edward T.

    2017-01-01

    Background oriented Schlieren images have historically been generated by calculating the observed pixel displacement between a wind-on and wind-o image pair using normalized cross-correlation. This work uses optical flow to solve the displacement fields which generate the Schlieren images. A well established method used in the computer vision community, optical flow is the apparent motion in an image sequence due to brightness changes. The regularization method of Horn and Schunck is used to create Schlieren images using two data sets: a supersonic jet plume shock interaction from the NASA Ames Unitary Plan Wind Tunnel, and a transonic flight test of a T-38 aircraft using a naturally occurring background, performed in conjunction with NASA Ames and Armstrong Research Centers. Results are presented and contrasted with those using normalized cross-correlation. The optical flow Schlieren images are found to provided significantly more detail. We apply the method to historical data sets to demonstrate the broad applicability and limitations of the technique.

  9. Ionospheric cusp flows pulsed by solar wind Alfvén waves

    Directory of Open Access Journals (Sweden)

    P. Prikryl

    2002-02-01

    Full Text Available Pulsed ionospheric flows (PIFs in the cusp foot-print have been observed by the SuperDARN radars with periods between a few minutes and several tens of minutes. PIFs are believed to be a consequence of the interplanetary magnetic field (IMF reconnection with the magnetospheric magnetic field on the dayside magnetopause, ionospheric signatures of flux transfer events (FTEs. The quasiperiodic PIFs are correlated with Alfvénic fluctuations observed in the upstream solar wind. It is concluded that on these occasions, the FTEs were driven by Alfvén waves coupling to the day-side magnetosphere. Case studies are presented in which the dawn-dusk component of the Alfvén wave electric field modulates the reconnection rate as evidenced by the radar observations of the ionospheric cusp flows. The arrival of the IMF southward turning at the magnetopause is determined from multipoint solar wind magnetic field and/or plasma measurements, assuming plane phase fronts in solar wind. The cross-correlation lag between the solar wind data and ground magnetograms that were obtained near the cusp footprint exceeded the estimated spacecraft-to-magnetopause propagation time by up to several minutes. The difference can account for and/or exceeds the Alfvén propagation time between the magnetopause and ionosphere. For the case of short period ( < 13 min PIFs, the onset times of the flow transients appear to be further delayed by at most a few more minutes after the IMF southward turning arrived at the magnetopause. For the case of long period (30 – 40 min PIFs, the observed additional delays were 10–20 min. We interpret the excess delay in terms of an intrinsic time scale for reconnection (Russell et al., 1997 which can be explained by the surface-wave induced magnetic reconnection mechanism (Uberoi et al., 1999. Here, surface waves with wavelengths larger than the thickness of the neutral layer induce a tearing-mode instability whose rise time explains the

  10. Hybrid Simulations of the Interaction Between Solar Wind Flow and the Hermean Magnetosphere

    Science.gov (United States)

    Travnicek, P.; Hellinger, P.; Schriver, D.; Ashour-Abdalla, M.

    2003-12-01

    We examine the magnetosphere of Mercury using global three dimensional hybrid plasma simulations. Hybrid simulations treat ions as particles and electrons as a fluid. Having ions as particles allows ion kinetic behavior and waves to be included in the physical treatment of the plasma as compared to magnetohydrodynamic (MHD) modeling that treats the plasma as a single magnetized fluid and does not include such kinetic effects. Kinetic effects are essential for understanding magnetospheric physics. Hybrid simulations scale to the ion inertial length and thus on a global scale are somewhat limited in spatial extent compared to an MHD simulation. We note effects caused by the scalling of the numerical model of the magnetized obstacle interacting with the solar wind flow with the full scale simulation. Hermean magnetosphere is estimated to be only a few times the planetary radius, it can fit within a hybrid simulation system. The overal structure of the interaction between a magnetized obstacle in the solar wind flow is determined by few basic parameters (namely the solar wind density, background magnetic field, and the speed of solar wind, and also the strength of the magnetic dipole of the obstacle and its radius). The structure of the interaction of the solar wind flow with Mercury is to a large extend unique when compared to other planets. For example, the magnetic moment of the Mercury is over 1000 times smaller than that of the Earth and also the solar wind is stronger nearby Mercury than at Earth's vicinity. The typical magnetosperic scales are comparable to the ion gyroradii and hence kinetic effects are important for the overall structure of the interaction between the Hermean magnetospere and the solar wind. In this paper we shall focus on the study of the overal structure of the bow shock and magnetosheath of Mercury. We shall examine the formation of the magnetospheric tail. We shall study particle distribution functions in different locations of the

  11. Ionospheric cusp flows pulsed by solar wind Alfvén waves

    Directory of Open Access Journals (Sweden)

    P. Prikryl

    Full Text Available Pulsed ionospheric flows (PIFs in the cusp foot-print have been observed by the SuperDARN radars with periods between a few minutes and several tens of minutes. PIFs are believed to be a consequence of the interplanetary magnetic field (IMF reconnection with the magnetospheric magnetic field on the dayside magnetopause, ionospheric signatures of flux transfer events (FTEs. The quasiperiodic PIFs are correlated with Alfvénic fluctuations observed in the upstream solar wind. It is concluded that on these occasions, the FTEs were driven by Alfvén waves coupling to the day-side magnetosphere. Case studies are presented in which the dawn-dusk component of the Alfvén wave electric field modulates the reconnection rate as evidenced by the radar observations of the ionospheric cusp flows. The arrival of the IMF southward turning at the magnetopause is determined from multipoint solar wind magnetic field and/or plasma measurements, assuming plane phase fronts in solar wind. The cross-correlation lag between the solar wind data and ground magnetograms that were obtained near the cusp footprint exceeded the estimated spacecraft-to-magnetopause propagation time by up to several minutes. The difference can account for and/or exceeds the Alfvén propagation time between the magnetopause and ionosphere. For the case of short period ( < 13 min PIFs, the onset times of the flow transients appear to be further delayed by at most a few more minutes after the IMF southward turning arrived at the magnetopause. For the case of long period (30 – 40 min PIFs, the observed additional delays were 10–20 min. We interpret the excess delay in terms of an intrinsic time scale for reconnection (Russell et al., 1997 which can be explained by the surface-wave induced magnetic reconnection mechanism (Uberoi et al., 1999. Here, surface waves with wavelengths larger than the thickness of the neutral layer induce a tearing-mode instability whose rise time explains the

  12. Flow field and load characteristics of the whole MEXICO wind turbine

    DEFF Research Database (Denmark)

    Xu, Haoran; Yang, Hua; Liu, Chao

    2017-01-01

    CFD(Computational Fluid Dynamics) method was used to perform steady numerical simulation investigation on the flow field and load characteristics of MEXICO(Model EXperiment In Controlled cOnditions) wind turbine under non-yawed condition. Circumferentially-Averaged method was used to extract...... the calculated axial, radial and tangential components of velocity along the axial direction, then these components were compared with the experimental data, the compared results show that the computational components agree well with the experimental data and the computational results are reliable. The flow...... characteristics around the blade was analyzed and the points of flow separation were found along the blade, the results show that the points of flow separation move towards trailing edge with the increase of radius. The distribution of vorticity in the wake of MEXICO rotor was also analyzed. The distribution...

  13. Imaging dipole flow sources using an artificial lateral-line system made of biomimetic hair flow sensors

    NARCIS (Netherlands)

    Dagamseh, A.M.K.; Wiegerink, Remco J.; Lammerink, Theodorus S.J.; Krijnen, Gijsbertus J.M.

    2013-01-01

    In Nature, fish have the ability to localize prey, school, navigate, etc., using the lateral-line organ. Artificial hair flow sensors arranged in a linear array shape (inspired by the lateral-line system (LSS) in fish) have been applied to measure airflow patterns at the sensor positions. Here, we

  14. Transient flows of the solar wind associated with small-scale solar activity in solar minimum

    Science.gov (United States)

    Slemzin, Vladimir; Veselovsky, Igor; Kuzin, Sergey; Gburek, Szymon; Ulyanov, Artyom; Kirichenko, Alexey; Shugay, Yulia; Goryaev, Farid

    The data obtained by the modern high sensitive EUV-XUV telescopes and photometers such as CORONAS-Photon/TESIS and SPHINX, STEREO/EUVI, PROBA2/SWAP, SDO/AIA provide good possibilities for studying small-scale solar activity (SSA), which is supposed to play an important role in heating of the corona and producing transient flows of the solar wind. During the recent unusually weak solar minimum, a large number of SSA events, such as week solar flares, small CMEs and CME-like flows were observed and recorded in the databases of flares (STEREO, SWAP, SPHINX) and CMEs (LASCO, CACTUS). On the other hand, the solar wind data obtained in this period by ACE, Wind, STEREO contain signatures of transient ICME-like structures which have shorter duration (<10h), weaker magnetic field strength (<10 nT) and lower proton temperature than usual ICMEs. To verify the assumption that ICME-like transients may be associated with the SSA events we investigated the number of weak flares of C-class and lower detected by SPHINX in 2009 and STEREO/EUVI in 2010. The flares were classified on temperature and emission measure using the diagnostic means of SPHINX and Hinode/EIS and were confronted with the parameters of the solar wind (velocity, density, ion composition and temperature, magnetic field, pitch angle distribution of the suprathermal electrons). The outflows of plasma associated with the flares were identified by their coronal signatures - CMEs (only in few cases) and dimmings. It was found that the mean parameters of the solar wind projected to the source surface for the times of the studied flares were typical for the ICME-like transients. The results support the suggestion that weak flares can be indicators of sources of transient plasma flows contributing to the slow solar wind at solar minimum, although these flows may be too weak to be considered as separate CMEs and ICMEs. The research leading to these results has received funding from the European Union’s Seventh Programme

  15. Implementation of the Actuator Cylinder Flow Model in the HAWC2 code for Aeroelastic Simulations on Vertical Axis Wind Turbines

    DEFF Research Database (Denmark)

    Aagaard Madsen, Helge; Larsen, Torben J.; Schmidt Paulsen, Uwe

    2013-01-01

    The paper presents the implementation of the Actuator Cylinder (AC) flow model in the HAWC2 aeroelastic code originally developed for simulation of Horizontal Axis Wind Turbine (HAWT) aeroelasticity. This is done within the DeepWind project where the main objective is to explore the competitivene...

  16. Non-axisymmetric line-driven disc winds - I. Disc perturbations

    Science.gov (United States)

    Dyda, Sergei; Proga, Daniel

    2018-04-01

    We study mass outflows driven from accretion discs by radiation pressure due to spectral lines. To investigate non-axisymmetric effects, we use the ATHENA++ code and develop a new module to account for radiation pressure driving. In 2D, our new simulations are consistent with previous 2D axisymmetric solutions by Proga et al., who used the ZEUS 2D code. Specifically, we find that the disc winds are time dependent, characterized by a dense stream confined to ˜45° relative to the disc mid-plane and bounded on the polar side by a less dense, fast stream. In 3D, we introduce a vertical, ϕ-dependent, subsonic velocity perturbation in the disc mid-plane. The perturbation does not change the overall character of the solution but global outflow properties such as the mass, momentum, and kinetic energy fluxes are altered by up to 100 per cent. Non-axisymmetric density structures develop and persist mainly at the base of the wind. They are relatively small, and their densities can be a few times higher than the azimuthal average. The structure of the non-axisymmetric and axisymmetric solutions differ also in other ways. Perhaps most importantly from the observational point of view are the differences in the so-called clumping factors, that serve as a proxy for emissivity due to two body processes. In particular, the spatially averaged clumping factor over the entire fast stream, while it is of a comparable value in both solutions, it varies about 10 times faster in the non-axisymmetric case.

  17. Passive Acoustic Detection of Wind Turbine In-Flow Conditions for Active Control and Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Murray, Nathan E.

    2012-03-12

    Wind is a significant source of energy; however, the human capability to produce electrical energy still has many hurdles to overcome. One of these is the unpredictability of the winds in the atmospheric boundary layer (ABL). The ABL is highly turbulent in both stable and unstable conditions (based on the vertical temperature profile) and the resulting fluctuations can have a dramatic impact on wind turbine operation. Any method by which these fluctuations could be observed, estimated, or predicted could provide a benefit to the wind energy industry as a whole. Based on the fundamental coupling of velocity fluctuations to pressure fluctuations in the nearly incompressible flow in the ABL, This work hypothesizes that a ground-based array of infrasonic pressure transducers could be employed to estimate the vertical wind profile over a height relevant for wind turbines. To analyze this hypothesis, experiments and field deployments were conducted. Wind tunnel experiments were performed for a thick turbulent boundary layer over a neutral or heated surface. Surface pressure and velocity probe measurements were acquired simultaneously. Two field deployments yielded surface pressure data from a 49 element array. The second deployment at the Reese Technology Center in Lubbock, TX, also included data from a smaller aperture, 96-element array and a 200-meter tall meteorological tower. Analysis of the data successfully demonstrated the ability to estimate the vertical velocity profile using coherence data from the pressure array. Also, dynamical systems analysis methods were successful in identifying and tracking a gust type event. In addition to the passive acoustic profiling method, this program also investigated a rapid response Doppler SODAR system, the optimization of wind turbine blades for enhanced power with reduced aeroacoustic noise production, and the implementation of a wireless health monitoring system for the wind turbine blades. Each of these other objectives

  18. The impacts of wind power integration on sub-daily variation in river flows downstream of hydroelectric dams.

    Science.gov (United States)

    Kern, Jordan D; Patino-Echeverri, Dalia; Characklis, Gregory W

    2014-08-19

    Due to their operational flexibility, hydroelectric dams are ideal candidates to compensate for the intermittency and unpredictability of wind energy production. However, more coordinated use of wind and hydropower resources may exacerbate the impacts dams have on downstream environmental flows, that is, the timing and magnitude of water flows needed to sustain river ecosystems. In this paper, we examine the effects of increased (i.e., 5%, 15%, and 25%) wind market penetration on prices for electricity and reserves, and assess the potential for altered price dynamics to disrupt reservoir release schedules at a hydroelectric dam and cause more variable and unpredictable hourly flow patterns (measured in terms of the Richards-Baker Flashiness (RBF) index). Results show that the greatest potential for wind energy to impact downstream flows occurs at high (∼25%) wind market penetration, when the dam sells more reserves in order to exploit spikes in real-time electricity prices caused by negative wind forecast errors. Nonetheless, compared to the initial impacts of dam construction (and the dam's subsequent operation as a peaking resource under baseline conditions) the marginal effects of any increased wind market penetration on downstream flows are found to be relatively minor.

  19. Incorporation of a wind generator model into a dynamic power flow analysis; Incorporacion de un modelo de generador eolico al analisis de flujos dinamicos de potencia

    Energy Technology Data Exchange (ETDEWEB)

    Angeles Camacho, C.; Banuelos Ruedas, F. [Instituto de Ingenieria, Universidad Nacional Autonoma de Mexico (Mexico)]. E-mail: cangelesc@iingen.unam.mx; fbanuelosr@iingen.unam.mx

    2011-07-15

    Wind energy is nowadays one of the most cost-effective and practical options for electric generation from renewable resources. However, increased penetration of wind generation causes the power networks to be more depend on, and vulnerable to, the varying wind speed. Modeling is a tool which can provide valuable information about the interaction between wind farms and the power network to which they are connected. This paper develops a realistic characterization of a wind generator. The wind generator model is incorporated into an algorithm to investigate its contribution to the stability of the power network in the time domain. The tool obtained is termed dynamic power flow. The wind generator model takes on account the wind speed and the reactive power consumption by induction generators. Dynamic power flow analysis is carried-out using real wind data at 10-minute time intervals collected for one meteorological station. The generation injected at one point into the network provides active power locally and is found to reduce global power losses. However, the power supplied is time-varying and causes fluctuations in voltage magnitude and power flows in transmission lines. [Spanish] La energia eolica es hoy en dia una de las opciones mas efectivas y practicas para la generacion de electricidad a partir de energias renovables. Sin embargo, el incremento de la penetracion de energia eolica provoca que los sistemas de potencia se vuelvan mas dependientes y vulnerables a las variaciones de la velocidad del viento. El modelado es una herramienta que provee informacion valiosa de la interaccion dinamica entre las turbinas eolicas y las redes de potencia a las que se conectan. El presente articulo desarrolla una caracterizacion realista de un modelo de la turbina eolica. El modelo de la turbina eolica se incorpora a un algoritmo para el analisis de su contribucion a la estabilidad de una red electrica en el dominio del tiempo. La herramienta obtenida se conoce como flujos

  20. Free-stream turbulence effects on the flow around an S809 wind turbine airfoil

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Nieves, Sheilla; Maldonado, Victor; Lebron, Jose [Rensselaer Polytechnic Institute, Troy, NY (United States); Kang, Hyung-Suk [United States Naval Academy, Annapolis, MD (United States); Meneveau, Charles [Johns Hopkins Univ., Baltimore, MD (United States); Castillo, Luciano [Texas Tech Univ., Lubbock, TX (United States)

    2012-07-01

    Two-dimensional Particle Image Velocimetry (2-D PIV) measurements were performed to study the effect of free-stream turbulence on the flow around a smooth and rough surface airfoil, specifically under stall conditions. A 0.25-m chord model with an S809 profile, common for horizontal-axis wind turbine applications, was tested at a wind tunnel speed of 10 m/s, resulting in Reynolds numbers based on the chord of Re{sub c} {approx} 182,000 and turbulence intensity levels of up to 6.14%. Results indicate that when the flow is fully attached, turbulence significantly decreases aerodynamic efficiency (from L/D {approx} 4.894 to L/D {approx} 0.908). On the contrary, when the flow is mostly stalled, the effect is reversed and aerodynamic performance is slightly improved (from L/D {approx} 1.696 to L/D {approx} 1.787). Analysis of the mean flow over the suction surface shows that, contrary to what is expected, free-stream turbulence is actually advancing separation, particularly when the turbulent scales in the free-stream are of the same order as the chord. This is a result of the complex dynamics between the boundary layer scales and the free-stream turbulence length scales when relatively high levels of active-grid generated turbulence are present. (orig.)

  1. Reduction of aerodynamic load fluctuation on wind turbine blades through active flow control

    Science.gov (United States)

    Velarde, John-Michael; Coleman, Thomas; Magstadt, Andrew; Aggarwal, Somil; Glauser, Mark

    2015-11-01

    The current set of experiments deals with implementing active flow control on a Bergey Excel 1, 1kW turbine. The previous work in our group demonstrated successfully that implementation of a simple closed-loop controller could reduce unsteady aerodynamic load fluctuation by 18% on a vertically mounted wing. Here we describe a similar flow control method adapted to work in the rotating frame of a 2.5m diameter wind turbine. Strain gages at the base of each blade measure the unsteady fluctuation in the blades and pressure taps distributed along the span of the blades feed information to the closed-loop control scheme. A realistic, unsteady flow field has been generated by placing a cylinder upstream of the turbine to induce shedding vortices at frequencies in the bandwidth of the first structural bending mode of the turbine blades. The goal of these experiments is to demonstrate closed-loop flow control as a means to reduce the unsteady fluctuation in the blades and increase the overall lifespan of the wind turbine.

  2. Field Test Results from a 10 kW Wind Turbine with Active Flow Control

    Science.gov (United States)

    Rice, Thomas; Bychkova, Veronika; Taylor, Keith; Clingman, Dan; Amitay, Michael

    2015-11-01

    Active flow control devices including synthetic jets and dynamic vortex generators were tested on a 10 kW wind turbine at RPI. Previous work has shown that load oscillations caused by dynamic stall could be modified through the use of active flow control by injecting momentum into the flow field near the leading edge of a dynamically pitching model. In this study, this work has been extended to its logical conclusion, field-testing active flow control on a real wind turbine. The blades in the current study have a 0.28m chord and 3.05m span, no twist or taper, and were retrofitted with six synthetic jets on one blade and ten dynamic vortex generators on a second blade. The third blade of this turbine was not modified, in order to serve as a control. Strain gauges were installed on each blade to measure blades' deflection. A simple closed loop control was demonstrated and preliminary results indicate reduced vibrational amplitude. Future testing will be conducted on a larger scale, 600kW machine at NREL, incorporating information collected during this study.

  3. Non-radial solar wind flows induced by the motion of interplanetary coronal mass ejections

    Directory of Open Access Journals (Sweden)

    M. Owens

    2004-12-01

    Full Text Available A survey of the non-radial flows (NRFs during nearly five years of interplanetary observations revealed the average non-radial speed of the solar wind flows to be ~30km/s, with approximately one-half of the large (>100km/s NRFs associated with ICMEs. Conversely, the average non-radial flow speed upstream of all ICMEs is ~100km/s, with just over one-third preceded by large NRFs. These upstream flow deflections are analysed in the context of the large-scale structure of the driving ICME. We chose 5 magnetic clouds with relatively uncomplicated upstream flow deflections. Using variance analysis it was possible to infer the local axis orientation, and to qualitatively estimate the point of interception of the spacecraft with the ICME. For all 5 events the observed upstream flows were in agreement with the point of interception predicted by variance analysis. Thus we conclude that the upstream flow deflections in these events are in accord with the current concept of the large-scale structure of an ICME: a curved axial loop connected to the Sun, bounded by a curved (though not necessarily circular cross section.

    Key words. Interplanetary physics (flare and stream dynamics; interplanetary magnetic fields; interplanetary shocks

  4. The effect of plasma flow on line-tied magnetohydrodynamic modes

    International Nuclear Information System (INIS)

    Arcudi, Francesco; Delzanno, Gian Luca; Finn, John M.

    2010-01-01

    The linear stability of a linear pinch to kink modes with line-tying boundary conditions and equilibrium axial flow is studied. Numerical results in visco-resistive magnetohydrodynamics show that for long plasmas, in which the line-tying stabilization effect is weak, plasma flow is stabilizing. For shorter plasmas, near the length at which line-tying stabilizes the mode for zero flow, the flow can be destabilizing. A simple model using reduced ideal magnetohydrodynamics with a step-function current density and an even simpler one-dimensional sound wave model with equilibrium flow elucidate these effects. It is concluded that: (1) The stabilization in long plasmas is due to convective stabilization; (2) the destabilization for short plasmas can be explained using a picture involving the coupling of two stable waves, one propagating in the forward direction and one in the backward direction; and (3) strong magnetic shear suppresses the flow destabilization for short plasmas.

  5. Structure of Turbulence in Katabatic Flows Below and Above the Wind-Speed Maximum

    Science.gov (United States)

    Grachev, Andrey A.; Leo, Laura S.; Sabatino, Silvana Di; Fernando, Harindra J. S.; Pardyjak, Eric R.; Fairall, Christopher W.

    2016-06-01

    Measurements of small-scale turbulence made in the atmospheric boundary layer over complex terrain during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured on four towers deployed along the east lower slope (2-4°) of Granite Mountain near Salt Lake City in Utah, USA. The multi-level (up to seven) observations made during a 30-day long MATERHORN field campaign in September-October 2012 allowed the study of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence statistics (e.g., fluxes, variances, spectra, and cospectra) and their variations in katabatic flow. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along-slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The momentum flux is directed downward (upward) whereas the along-slope heat flux is downslope (upslope) below (above) the wind maximum. This suggests that the position of the jet-speed maximum can be obtained by linear interpolation between positive and negative values of the momentum flux (or the along-slope heat flux) to derive the height where the flux becomes zero. It is shown that the standard deviations of all wind-speed components (and therefore of the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind-speed maximum. We report several cases when the destructive effect of vertical heat flux is completely cancelled by the generation of turbulence due to the along-slope heat flux. Turbulence above the wind

  6. Power generation and blade flow measurements of a full scale wind turbine

    Science.gov (United States)

    Gaunt, Brian

    Experimental research has been completed using a custom designed and built 4m wind turbine in a university operated wind facility. The primary goals of turbine testing were to determine the power production of the turbine and to apply the particle image velocimetry (PIV) technique to produce flow visualization images and velocity vector maps near the tip of a blade. These tests were completed over a wide range of wind speeds and turbine blade rotational speeds. This testing was also designed to be a preliminary study of the potential for future research using the turbine apparatus and to outline it's limitations. The goals and results of other large scale turbine tests are briefly discussed with a comparison outlining the unique aspects of the experiment outlined in this thesis. Power production tests were completed covering a range of mean wind speeds, 6.4 m/s to 11.1 m/s nominal, and rotational rates, 40 rpm to 220 rpm. This testing allowed the total power produced by the blades to be determined as a function of input wind speed, as traditionally found in power curves for commercial turbines. The coefficient of power, Cp, was determined as a function of the tip speed ratio which gave insight into the peak power production of the experimental turbine. It was found, as expected, that the largest power production occurred at the highest input wind speed, 11.1 m/s, and reached a mean value of 3080 W at a rotational rate of 220 rpm. Peak Cp was also found, as a function of the tip speed ratio, to approach 0.4 at the maximum measurable tip speed ratio of 8. Blade element momentum (BEM) theory was also implemented as an aerodynamic power and force prediction tool for the given turbine apparatus. Comparisons between the predictions and experimental results were made with a focus on the Cp power curve to verify the accuracy of the initial model. Although the initial predictions, based on lift and drag curves found in Abbot and Von Deonhoff 1, were similar to experimental

  7. Integrated Cantilever-Based Flow Sensors with Tunable Sensitivity for In-Line Monitoring of Flow Fluctuations in Microfluidic Systems

    Directory of Open Access Journals (Sweden)

    Nadine Noeth

    2013-12-01

    Full Text Available For devices such as bio-/chemical sensors in microfluidic systems, flow fluctuations result in noise in the sensor output. Here, we demonstrate in-line monitoring of flow fluctuations with a cantilever-like sensor integrated in a microfluidic channel. The cantilevers are fabricated in different materials (SU-8 and SiN and with different thicknesses. The integration of arrays of holes with different hole size and number of holes allows the modification of device sensitivity, theoretical detection limit and measurement range. For an average flow in the microliter range, the cantilever deflection is directly proportional to the flow rate fluctuations in the microfluidic channel. The SiN cantilevers show a detection limit below 1 nL/min and the thinnest SU-8 cantilevers a detection limit below 5 nL/min. Finally, the sensor is applied for in-line monitoring of flow fluctuations generated by external pumps connected to the microfluidic system.

  8. Integrated cantilever-based flow sensors with tunable sensitivity for in-line monitoring of flow fluctuations in microfluidic systems

    DEFF Research Database (Denmark)

    Noeth, Nadine-Nicole; Keller, Stephan Sylvest; Boisen, Anja

    2014-01-01

    For devices such as bio-/chemical sensors in microfluidic systems, flow fluctuations result in noise in the sensor output. Here, we demonstrate in-line monitoring of flow fluctuations with a cantilever-like sensor integrated in a microfluidic channel. The cantilevers are fabricated in different...... materials (SU-8 and SiN) and with different thicknesses. The integration of arrays of holes with different hole size and number of holes allows the modification of device sensitivity, theoretical detection limit and measurement range. For an average flow in the microliter range, the cantilever deflection...... is directly proportional to the flow rate fluctuations in the microfluidic channel. The SiN cantilevers show a detection limit below 1 nL/min and the thinnest SU-8 cantilevers a detection limit below 5 nL/min. Finally, the sensor is applied for in-line monitoring of flow fluctuations generated by external...

  9. Safety System for Controlling Fluid Flow into a Suction Line

    Science.gov (United States)

    England, John Dwight (Inventor); Kelley, Anthony R. (Inventor); Cronise, Raymond J. (Inventor)

    2015-01-01

    A safety system includes a sleeve fitted within a pool's suction line at the inlet thereof. An open end of the sleeve is approximately aligned with the suction line's inlet. The sleeve terminates with a plate that resides within the suction line. The plate has holes formed therethrough. A housing defining a plurality of distinct channels is fitted in the sleeve so that the distinct channels lie within the sleeve. Each of the distinct channels has a first opening on one end thereof and a second opening on another end thereof. The second openings reside in the sleeve. Each of the distinct channels is at least approximately three feet in length. The first openings are in fluid communication with the water in the pool, and are distributed around a periphery of an area of the housing that prevents coverage of all the first openings when a human interacts therewith.

  10. Solar wind stagnation near comets

    International Nuclear Information System (INIS)

    Galeev, A.A.; Cravens, T.E.; Gombosi, T.I.

    1983-03-01

    The nature of the solar wind flow near comets is examined analytically. In particular, the typical values for the stagnation pressure and magnetic barrier strength are estimated, taking into account the magnetic field line tension and the charge exchange cooling of the mass loaded solar wind. Knowledge of the strength of the magnetic barrier is required in order to determine the location of the contact discontinuity which separates the contaminated solar wind plasma and the outflowing plasma of the cometary ionosphere. (author)

  11. Solution of wind integrated thermal generation system for environmental optimal power flow using hybrid algorithm

    Directory of Open Access Journals (Sweden)

    Ambarish Panda

    2016-09-01

    Full Text Available A new evolutionary hybrid algorithm (HA has been proposed in this work for environmental optimal power flow (EOPF problem. The EOPF problem has been formulated in a nonlinear constrained multi objective optimization framework. Considering the intermittency of available wind power a cost model of the wind and thermal generation system is developed. Suitably formed objective function considering the operational cost, cost of emission, real power loss and cost of installation of FACTS devices for maintaining a stable voltage in the system has been optimized with HA and compared with particle swarm optimization algorithm (PSOA to prove its effectiveness. All the simulations are carried out in MATLAB/SIMULINK environment taking IEEE30 bus as the test system.

  12. Customized Pull Systems for Single-Product Flow Lines

    NARCIS (Netherlands)

    Gaury, E.G.A.; Kleijnen, J.P.C.; Pierreval, H.

    1998-01-01

    Traditionally pull production systems are managed through classic control systems such as Kanban, Conwip, or Base stock, but this paper proposes ‘customized’ pull control. Customization means that a given production line is managed through a pull control system that in principle connects each stage

  13. Flow Quality Measurements in the NASA Ames Upgraded 11-by 11-Foot Transonic Wind Tunnel

    Science.gov (United States)

    Amaya, Max A.; Murthy, Sreedhara V.; George, M. W. (Technical Monitor)

    2000-01-01

    Among the many upgrades designed and implemented in the NASA Ames 11-by 11-Foot Transonic Wind Tunnel over the past few years, several directly affect flow quality in the test section: a turbulence reduction system with a honeycomb and two screens, a flow smoothing system in the back leg diffusers, an improved drive motor control system, and a full replacement set of composite blades for the compressor. Prior to the shut-down of the tunnel for construction activities, an 8-foot span rake populated with flow instrumentation was traversed in the test section to fully document the flow quality and establish a baseline against which the upgrades could be characterized. A similar set of measurements was performed during the recent integrated system test trials, but the scope was somewhat limited in accordance with the primary objective of such tests, namely to return the tunnel to a fully operational status. These measurements clearly revealed substantial improvements in flow angularity and significant reductions in turbulence level for both full-span and semi-span testing configurations, thus making the flow quality of the tunnel one of the best among existing transonic facilities.

  14. Stability and transition of attachment-line flow

    NARCIS (Netherlands)

    Heeg, R.

    1998-01-01

    Moving vehicles, such as submarines and airplanes, are surrounded by a thin boundary layer in which the relative uid velocity drops rapidly to zero close to the solid walls of the vehicle. The transition of such boundary layers from laminar into turbulent flow is an interesting phenomenon. Moreover,

  15. Laminar Flow Processes of Fluid Energy Carries in Pipe Lines

    Directory of Open Access Journals (Sweden)

    R. I. Еsman

    2012-01-01

    Full Text Available The paper proposes methodology for analysis and calculation of laminar fluid flows in pipes and channels.  Various regimes of fluid motion in pipelines of heat-power units and equipment are considered in the paper.The presented dependencies can be used for practical calculations while transporting energy carriers for various application.

  16. On Variable Reverse Power Flow-Part I: Active-Reactive Optimal Power Flow with Reactive Power of Wind Stations

    Directory of Open Access Journals (Sweden)

    Aouss Gabash

    2016-02-01

    Full Text Available It has recently been shown that using battery storage systems (BSSs to provide reactive power provision in a medium-voltage (MV active distribution network (ADN with embedded wind stations (WSs can lead to a huge amount of reverse power to an upstream transmission network (TN. However, unity power factors (PFs of WSs were assumed in those studies to analyze the potential of BSSs. Therefore, in this paper (Part-I, we aim to further explore the pure reactive power potential of WSs (i.e., without BSSs by investigating the issue of variable reverse power flow under different limits on PFs in an electricity market model. The main contributions of this work are summarized as follows: (1 Introducing the reactive power capability of WSs in the optimization model of the active-reactive optimal power flow (A-R-OPF and highlighting the benefits/impacts under different limits on PFs. (2 Investigating the impacts of different agreements for variable reverse power flow on the operation of an ADN under different demand scenarios. (3 Derivation of the function of reactive energy losses in the grid with an equivalent-π circuit and comparing its value with active energy losses. (4 Balancing the energy curtailment of wind generation, active-reactive energy losses in the grid and active-reactive energy import-export by a meter-based method. In Part-II, the potential of the developed model is studied through analyzing an electricity market model and a 41-bus network with different locations of WSs.

  17. 76 FR 20006 - Wind Turbine Guidelines Advisory Committee; Teleconference Line Available for Public Meeting

    Science.gov (United States)

    2011-04-11

    ... SUPPLEMENTARY INFORMATION). FOR FURTHER INFORMATION CONTACT: Rachel London, Division of Habitat and Resource... filled room capacity. Dated: April 6, 2011. Rachel London, Alternate Designated Federal Officer, Wind...

  18. Nested separatrices in simple shear flows: the effect of localized disturbances on stagnation lines

    OpenAIRE

    Wilson, M.C.T.; Gaskell, P.H.; Savage, M.D.

    2005-01-01

    The effects of localized two-dimensional disturbances on the structure of shear flows featuring a stagnation line are investigated. A simple superposition of a planar Couette flow and Moffatt's [J. Fluid Mech. 18, 1--18 (1964)] streamfunction for the decay of a disturbance between infinite stationary parallel plates shows that in general the stagnation line is replaced by a chain of alternating elliptic and hyperbolic stagnation points with a separation equal to 2.78 times the half-gap betwee...

  19. Safety System for Controlling Fluid Flow into a Suction Line

    Science.gov (United States)

    England, John Dwight (Inventor); Kelley, Anthony R. (Inventor); Cronise, Raymond J. (Inventor)

    2018-01-01

    A safety system includes a sleeve fitted within a pool's suction line at its inlet. The sleeve terminates with a plate that resides within the suction line. The plate has holes formed therethrough. A housing defining distinct channels is fitted in the sleeve so that the distinct channels lie within the sleeve. Each of the distinct channels has a first opening on one end thereof and a second opening on another end thereof. The second openings reside in the sleeve. The first openings are in fluid communication with the water in the pool, and are distributed around a periphery of an area of the housing that prevents coverage of all the first openings when a human interacts therewith. A first sensor is coupled to the sleeve to sense pressure therein, and a second pressure sensor is coupled to the plate to sense pressure in one of the plates' holes.

  20. Accuracy of State-of-the-Art Actuator-Line Modeling for Wind Turbine Wakes

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Pankaj; Churchfield, Matthew; Moriarty, Patrick; Schmitz, Sven

    2013-01-14

    The current actuator line method (ALM) within an OpenFOAM computational fluid dynamics (CFD) solver was used to perform simulations of the NREL Phase VI rotor under rotating and parked conditions, two fixed-wing designs both with an elliptic spanwise loading, and the NREL 5-MW turbine. The objective of this work is to assess and improve the accuracy of the state-of-the-art ALM in predicting rotor blade loads, particularly by focusing on the method used to project the actuator forces onto the flow field as body forces. Results obtained for sectional normal and tangential force coefficients were compared to available experimental data and to the in-house performance code XTurb-PSU. It was observed that the ALM results agree well with measured data and results obtained from XTurb-PSU except in the root and tip regions if a three-dimensional Gaussian of width, ε, constant along the blade span is used to project the actuator force onto the flow field. A new method is proposed where the Gaussian width, ε, varies along the blade span following an elliptic distribution. A general criterion is derived that applies to any planform shape. It is found that the new criterion for ε leads to improved prediction of blade tip loads for a variety of blade planforms and rotor conditions considered.

  1. Flow and turbulence control in a boundary layer wind tunnel using passive hardware devices

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Ribičić, Mihael; Pospíšil, Stanislav; Plut, Mihael; Trush, Arsenii; Kozmar, H.

    2017-01-01

    Roč. 41, č. 6 (2017), s. 643-661 ISSN 0732-8818 R&D Projects: GA ČR(CZ) GA14-12892S; GA MŠk(CZ) LO1219 Keywords : turbulent flow * atmospheric boundary layer * wind-tunnel simulation * castellated barrier wall * Counihan vortex generators * surface roughness elements * hot-wire measurements Subject RIV: JM - Building Engineering OBOR OECD: Construction engineering, Municipal and structural engineering Impact factor: 0.932, year: 2016 https://link.springer.com/article/10.1007/s40799-017-0196-z

  2. Understanding IMF Bz and Space Weather Relations Near Geomagnetic Equator Related to Non-Radial Solar Wind Flows (P35)

    Science.gov (United States)

    Pereira, F.; Girish, T. E.

    2006-11-01

    We have reported earlier some new results related to the seasonal and solar cycle changes in the north-south component of IMF (Bz) observed near 1 A.U. A relationship between geomagnetic activity and non-radial solar wind flows were reported recently. In this connection, we are planning some studies for IHY 2007. We propose to identify non-radial flow structures in the interplanetary medium using IPS observations and predict the associated IMF Bz structures. The effect of geomagnetic storms near magnetic equator associated with non-radial solar wind flows will be studied using magnetometer observations in Trivandrum.

  3. Analysis and Countermeasures of Wind Power Accommodation by Aluminum Electrolysis Pot-Lines in China

    Science.gov (United States)

    Zhang, Hongliang; Ran, Ling; He, Guixiong; Wang, Zhenyu; Li, Jie

    2017-10-01

    The unit energy consumption and its price have become the main obstacles for the future development of the aluminum electrolysis industry in China. Meanwhile, wind power is widely being abandoned because of its instability. In this study, a novel idea for wind power accommodation is proposed to achieve a win-win situation: the idea is for nearby aluminum electrolysis plants to absorb the wind power. The features of the wind power distribution and aluminum electrolysis industry are first summarized, and the concept of wind power accommodation by the aluminum industry is introduced. Then, based on the characteristics of aluminum reduction cells, the key problems, including the bus-bar status, thermal balance, and magnetohydrodynamics instabilities, are analyzed. In addition, a whole accommodation implementation plan for wind power by aluminum reduction is introduced to explain the theoretical value of accommodation, evaluation of the reduction cells, and the industrial experiment scheme. A numerical simulation of a typical scenario proves that there is large accommodation potential for the aluminum reduction cells. Aluminum electrolysis can accommodate wind power and remain stable under the proper technique and accommodation scheme, which will provide promising benefits for the aluminum plant and the wind energy plant.

  4. Line filter design of parallel interleaved VSCs for high power wind energy conversion systems

    DEFF Research Database (Denmark)

    Gohil, Ghanshyamsinh Vijaysinh; Bede, Lorand; Teodorescu, Remus

    2015-01-01

    The Voltage Source Converters (VSCs) are often connected in parallel in a Wind Energy Conversion System (WECS) to match the high power rating of the modern wind turbines. The effect of the interleaved carriers on the harmonic performance of the parallel connected VSCs is analyzed in this paper. I...

  5. The Impact of Landscape Fragmentation on Atmospheric Flow: A Wind-Tunnel Study

    Science.gov (United States)

    Poëtte, Christopher; Gardiner, Barry; Dupont, Sylvain; Harman, Ian; Böhm, Margi; Finnigan, John; Hughes, Dale; Brunet, Yves

    2017-06-01

    Landscape discontinuities such as forest edges play an important role in determining the characteristics of the atmospheric flow by generating increased turbulence and triggering the formation of coherent tree-scale structures. In a fragmented landscape, consisting of surfaces of different heights and roughness, the multiplicity of edges may lead to complex patterns of flow and turbulence that are potentially difficult to predict. Here, we investigate the effects of different levels of forest fragmentation on the airflow. Five gap spacings (of length approximately 5 h, 10 h, 15 h, 20 h, 30 h, where h is the canopy height) between forest blocks of length 8.7 h, as well as a reference case consisting of a continuous forest after a single edge, were investigated in a wind tunnel. The results reveal a consistent pattern downstream from the first edge of each simulated case, with the streamwise velocity component at tree top increasing and turbulent kinetic energy decreasing as gap size increases, but with overshoots in shear stress and turbulent kinetic energy observed at the forest edges. As the gap spacing increases, the flow appears to change monotonically from a flow over a single edge to a flow over isolated forest blocks. The apparent roughness of the different fragmented configurations also decreases with increasing gap size. No overall enhancement of turbulence is observed at any particular level of fragmentation.

  6. Stand-alone excitation synchronous wind power generators with power flow management strategy

    Directory of Open Access Journals (Sweden)

    Tzuen-Lih Chern

    2014-09-01

    Full Text Available This study presents a stand-alone excitation synchronous wind power generator (SESWPG with power flow management strategy (PFMS. The rotor speed of the excitation synchronous generator tracks the utility grid frequency by using servo motor tracking technologies. The automatic voltage regulator governs the exciting current of generator to achieve the control goals of stable voltage. When wind power is less than the needs of the consumptive loading, the proposed PFMS increases motor torque to provide a positive power output for the loads, while keeping the generator speed constant. Conversely, during the periods of wind power greater than output loads, the redundant power of generator production is charged to the battery pack and the motor speed remains constant with very low power consumption. The advantage of the proposed SESWPG is that the generator can directly output stable alternating current (AC electricity without using additional DC–AC converters. The operation principles with software simulation for the system are described in detail. Experimental results of a laboratory prototype are shown to verify the feasibility of the system.

  7. Structural characterization of wind-sheared turbulent flow using self-organized mapping

    Science.gov (United States)

    Scott, Nicholas V.; Handler, Robert A.

    2016-05-01

    A nonlinear cluster analysis algorithm is used to characterize the spatial structure of a wind-sheared turbulent flow obtained from the direct numerical simulation (DNS) of the three-dimensional temperature and momentum fields. The application of self-organizing mapping to DNS data for data reduction is utilized because of the dimensional similitude in structure between DNS data and remotely sensed hyperspectral and multispectral data where the technique has been used extensively. For the three Reynolds numbers of 150, 180, and 220 used in the DNS, self-organized mapping is successful in the extraction of boundary layer streaky structures from the turbulent temperature and momentum fields. In addition, it preserves the cross-wind scale structure of the streaks exhibited in both fields which loosely scale with the inverse of the Reynolds number. Self-organizing mapping of the along wind component of the helicity density shows a layer of the turbulence field which is spotty suggesting significant direct coupling between the large and small-scale turbulent structures. The spatial correlation of the temperature and momentum fields allows for the possibility of the remote extrapolation of the momentum structure from thermal structure.

  8. Parametric Study of Tuned Mass Dampers for Long Span Transmission Tower-Line System under Wind Loads

    Directory of Open Access Journals (Sweden)

    Li Tian

    2016-01-01

    Full Text Available A parametric study of tuned mass dampers for a long span transmission tower-line system under wind loads is done in this paper. A three-dimensional finite element model of transmission tower-line system is established by SAP2000 software to numerically verify the effectiveness of the tuned mass damper device. The wind load time history is simulated based on Kaimal spectrum by the harmony superposition method. The equations of motion of a system with tuned mass damper under wind load excitation are proposed, and the schematic of tuned mass damper is introduced. The effects of mass ratio, frequency ratio, damping ratio, the change of the sag of transmission line, and the robustness of TMD are investigated, respectively. Results show that (1 the change of mass ratio has a greater effect on the vibration reduction ratio than those of frequency ratio and damping ratio, and the best vibration reduction ratio of TMD is not the frequency ratio of 1; (2 the sag-span ratio has an insignificant effect on the vibration reduction ratio of transmission tower when the change of sag-span ratio is not large; and (3 the effect of ice should be considered when the robustness study of TMD is carried out.

  9. Imposed Work of Breathing for Flow Meters with In-Line versus Flow-Through Technique during Simulated Neonatal Breathing.

    Directory of Open Access Journals (Sweden)

    Snorri Donaldsson

    Full Text Available The ability to determine airflow during nasal CPAP (NCPAP treatment without adding dead space or resistance would be useful when investigating the physiologic effects of different NCPAP systems on breathing. The aim of this study was to investigate the effect on pressure stability of different flow measuring devices at the in-line and flow-through position, using simulated neonatal breathing.Six different flow measure devices were evaluated by recording pressure changes and imposed work of breathing for breaths with 16 and 32 ml tidal volumes. The tests were performed initially with the devices in an in line position and with 5 and 10 L/min using flow through technique, without CPAP. The flow meters were then subsequently tested with an Infant Flow CPAP system at 3, 5 and 8 cm H2O pressure using flow through technique. The quality of the recorded signals was compared graphically.The resistance of the measuring devices generated pressure swings and imposed work of breathing. With bias flow, the resistance also generated CPAP pressure. Three of the devices had low resistance and generated no changes in pressure stability or CPAP pressure. The two devices intended for neonatal use had the highest measured resistance.The importance of pressure stability and increased work of breathing during non-invasive respiratory support are insufficiently studied. Clinical trials using flow-through technique have not focused on pressure stability. Our results indicate that a flow-through technique might be a way forward in obtaining a sufficiently high signal quality without the added effects of rebreathing and increased work of breathing. The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

  10. IEA-Task 31 WAKEBENCH: Towards a protocol for wind farm flow model evaluation. Part 2: Wind farm wake models

    DEFF Research Database (Denmark)

    Moriarty, Patrick; Rodrigo, Javier Sanz; Gancarski, Pawel

    2014-01-01

    .windbench.net). This paper provides an overview of the building-block validation approach applied to wind farm wake models, including best practices for the benchmarking and data processing procedures for validation datasets from wind farm SCADA and meteorological databases. A hierarchy of test cases has been proposed...

  11. Effect of weld line shape on material flow during friction stir welding of aluminum and steel

    International Nuclear Information System (INIS)

    Yasui, Toshiaki; Ando, Naoyuki; Morinaka, Shinpei; Mizushima, Hiroki; Fukumoto, Masahiro

    2014-01-01

    The effect of weld line shape on material flow during the friction stir welding of aluminum and steel was investigated. The material flow velocity was evaluated with simulated experiments using plasticine as the simulant material. The validity of the simulated experiments was verified by the marker material experiments on aluminum. The circumferential velocity of material around the probe increased with the depth from the weld surface. The effect is significant in cases where the advancing side is located on the outside of curve and those with higher curvature. Thus, there is an influence of weld line shape on material flow

  12. Wake effect on a uniform flow behind wind-turbine model

    DEFF Research Database (Denmark)

    Okulov, Valery; Naumov, I. V.; Mikkelsen, Robert Flemming

    2015-01-01

    LDA experiments were carried out to study the development of mean velocity profiles of the very far wake behind a wind turbine model in a water flume. The model of the rotor is placed in a middle of the flume. The initial flume flow is subjected to a very low turbulence level, limiting the influe......LDA experiments were carried out to study the development of mean velocity profiles of the very far wake behind a wind turbine model in a water flume. The model of the rotor is placed in a middle of the flume. The initial flume flow is subjected to a very low turbulence level, limiting...... the influence of external disturbances on the development of the inherent wake instability. The rotor is three-bladed and designed using Glauert’s optimum theory at a tip speed ratio λ =5 with a constant of the lift coefficient along the span, CL= 0.8. The wake development has been studied in the range of tip...

  13. Flow downstream of the heliospheric terminal shock: Magnetic field line topology and solar cycle imprint

    Science.gov (United States)

    Nerney, Steven; Suess, S. T.; Schmahl, E. J.

    1995-01-01

    The topology of the magnetic field in the heliosheath is illustrated using plots of the field lines. It is shown that the Archimedean spiral inside the terminal shock is rotated back in the heliosheath into nested spirals that are advected in the direction of the interstellar wind. The 22-year solar magnetic cycle is imprinted onto these field lines in the form of unipolar magnetic envelopes surrounded by volumes of strongly mixed polarity. Each envelope is defined by the changing tilt of the heliospheric current sheet, which is in turn defined by the boundary of unipolar high-latitude regions on the Sun that shrink to the pole at solar maximum and expand to the equator at solar minimum. The detailed shape of the envelopes is regulated by the solar wind velocity structure in the heliosheath.

  14. Stability of Contact Lines in Fluids: 2D Stokes Flow

    Science.gov (United States)

    Guo, Yan; Tice, Ian

    2018-02-01

    In an effort to study the stability of contact lines in fluids, we consider the dynamics of an incompressible viscous Stokes fluid evolving in a two-dimensional open-top vessel under the influence of gravity. This is a free boundary problem: the interface between the fluid in the vessel and the air above (modeled by a trivial fluid) is free to move and experiences capillary forces. The three-phase interface where the fluid, air, and solid vessel wall meet is known as a contact point, and the angle formed between the free interface and the vessel is called the contact angle. We consider a model of this problem that allows for fully dynamic contact points and angles. We develop a scheme of a priori estimates for the model, which then allow us to show that for initial data sufficiently close to equilibrium, the model admits global solutions that decay to equilibrium exponentially quickly.

  15. RAMSIM: A fast computer model for mean wind flow over hills

    Energy Technology Data Exchange (ETDEWEB)

    Corbett, J-F.

    2007-06-15

    The Riso Atmospheric Mixed Spectral-Integration Model (RAMSIM) is a micro-scale, linear flow model developed to quickly calculate the mean wind flow field over orography. It was designed to bridge the gap between WAsP and similar models that are fast but insufficiently accurate over steep slopes, and non-linear CFD models that are accurate but too computationally expensive for routine use on a PC. RAMSIM is governed by the RANS and E-{epsilon} turbulence closure equations, expressed in non-Cartesian coordinates. A terrain-following coordinate system is created from a simple analytical expression. The equations are linearized by a perturbation expansion about the flat-terrain case. The first-order equations, representing the spatial correction due to the presence of orography, are Fourier-transformed analytically in the two horizontal dimensions. The pressure and horizontal velocity components are eliminated, resulting in a set of four ordinary differential equations (ODEs). RAMSIM is currently implemented and tested in two-dimensional space; a 3D version has been formulated but not yet implemented. In the 2D case, there are only three ODEs, depending on only two non-dimensional parameters. This is exploited by solving the ODEs by Runge-Kutta integration for all useful combinations of these parameters, and storing the results in look-up tables (LUT). The flow field over any given orography is then quickly obtained by interpolating from the LUTs and scaling the value of the flow variables for each wavenumber component of the orography, and returning to real space by inverse Fourier transform. RAMSIM was tested against measurements, as well as other authors' flow models, in four test cases: two laboratory flows over idealized terrain, and two field experiments. RAMSIM calculations generally agree with measurements over upward slopes and hilltops, but overestimate the speed very near the ground at hilltops. RAMSIM appears to have an edge over other linear models

  16. A fish perspective: detecting flow features while moving using an artificial lateral line in steady and unsteady flow.

    Science.gov (United States)

    Chambers, L D; Akanyeti, O; Venturelli, R; Ježov, J; Brown, J; Kruusmaa, M; Fiorini, P; Megill, W M

    2014-10-06

    For underwater vehicles to successfully detect and navigate turbulent flows, sensing the fluid interactions that occur is required. Fish possess a unique sensory organ called the lateral line. Sensory units called neuromasts are distributed over their body, and provide fish with flow-related information. In this study, a three-dimensional fish-shaped head, instrumented with pressure sensors, was used to investigate the pressure signals for relevant hydrodynamic stimuli to an artificial lateral line system. Unsteady wakes were sensed with the objective to detect the edges of the hydrodynamic trail and then explore and characterize the periodicity of the vorticity. The investigated wakes (Kármán vortex streets) were formed behind a range of cylinder diameter sizes (2.5, 4.5 and 10 cm) and flow velocities (9.9, 19.6 and 26.1 cm s(-1)). Results highlight that moving in the flow is advantageous to characterize the flow environment when compared with static analysis. The pressure difference from foremost to side sensors in the frontal plane provides us a useful measure of transition from steady to unsteady flow. The vortex shedding frequency (VSF) and its magnitude can be used to differentiate the source size and flow speed. Moreover, the distribution of the sensing array vertically as well as the laterally allows the Kármán vortex paired vortices to be detected in the pressure signal as twice the VSF. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  17. A fish perspective: detecting flow features while moving using an artificial lateral line in steady and unsteady flow

    Science.gov (United States)

    Chambers, L. D.; Akanyeti, O.; Venturelli, R.; Ježov, J.; Brown, J.; Kruusmaa, M.; Fiorini, P.; Megill, W. M.

    2014-01-01

    For underwater vehicles to successfully detect and navigate turbulent flows, sensing the fluid interactions that occur is required. Fish possess a unique sensory organ called the lateral line. Sensory units called neuromasts are distributed over their body, and provide fish with flow-related information. In this study, a three-dimensional fish-shaped head, instrumented with pressure sensors, was used to investigate the pressure signals for relevant hydrodynamic stimuli to an artificial lateral line system. Unsteady wakes were sensed with the objective to detect the edges of the hydrodynamic trail and then explore and characterize the periodicity of the vorticity. The investigated wakes (Kármán vortex streets) were formed behind a range of cylinder diameter sizes (2.5, 4.5 and 10 cm) and flow velocities (9.9, 19.6 and 26.1 cm s−1). Results highlight that moving in the flow is advantageous to characterize the flow environment when compared with static analysis. The pressure difference from foremost to side sensors in the frontal plane provides us a useful measure of transition from steady to unsteady flow. The vortex shedding frequency (VSF) and its magnitude can be used to differentiate the source size and flow speed. Moreover, the distribution of the sensing array vertically as well as the laterally allows the Kármán vortex paired vortices to be detected in the pressure signal as twice the VSF. PMID:25079867

  18. Modulation of Jupiter's plasma flow, polar currents, and auroral precipitation by solar wind-induced compressions and expansions of the magnetosphere: a simple theoretical model

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2007-06-01

    Full Text Available We construct a simple model of the plasma flow, magnetosphere-ionosphere coupling currents, and auroral precipitation in Jupiter's magnetosphere, and examine how they respond to compressions and expansions of the system induced by changes in solar wind dynamic pressure. The main simplifying assumption is axi-symmetry, the system being modelled principally to reflect dayside conditions. The model thus describes three magnetospheric regions, namely the middle and outer magnetosphere on closed magnetic field lines bounded by the magnetopause, together with a region of open field lines mapping to the tail. The calculations assume that the system is initially in a state of steady diffusive outflow of iogenic plasma with a particular equatorial magnetopause radius, and that the magnetopause then moves rapidly in or out due to a change in the solar wind dynamic pressure. If the change is sufficiently rapid (~2–3 h or less the plasma angular momentum is conserved during the excursion, allowing the modified plasma angular velocity to be calculated from the radial displacement of the field lines, together with the modified magnetosphere-ionosphere coupling currents and auroral precipitation. The properties of these transient states are compared with those of the steady states to which they revert over intervals of ~1–2 days. Results are shown for rapid compressions of the system from an initially expanded state typical of a solar wind rarefaction region, illustrating the reduction in total precipitating electron power that occurs for modest compressions, followed by partial recovery in the emergent steady state. For major compressions, however, typical of the onset of a solar wind compression region, a brightened transient state occurs in which super-rotation is induced on closed field lines, resulting in a reversal in sense of the usual magnetosphere-ionosphere coupling current system. Current system reversal results in accelerated auroral electron

  19. On-line validation of feedwater flow rate in nuclear power plants using neural networks

    International Nuclear Information System (INIS)

    Khadem, M.; Ipakchi, A.; Alexandro, F.J.; Colley, R.W.

    1994-01-01

    On-line calibration of feedwater flow rate measurement in nuclear power plants provides a continuous realistic value of feedwater flow rate. It also reduces the manpower required for periodic calibration needed due to the fouling and defouling of the venturi meter surface condition. This paper presents a method for on-line validation of feedwater flow rate in nuclear power plants. The method is an improvement of the previously developed method which is based on the use of a set of process variables dynamically related to the feedwater flow rate. The online measurements of this set of variables are used as inputs to a neural network to obtain an estimate of the feedwater flow rate reading. The difference between the on-line feedwater flow rate reading, and the neural network estimate establishes whether there is a need to apply a correction factor to the feedwater flow rate measurement for calculation of the actual reactor power. The method was applied to the feedwater flow meters in the two feedwater flow loops of the TMI-1 nuclear power plant. The venturi meters used for flow measurements are susceptible to frequent fouling that degrades their measurement accuracy. The fouling effects can cause an inaccuracy of up to 3% relative error in feedwater flow rate reading. A neural network, whose inputs were the readings of a set of reference instruments, was designed to predict both feedwater flow rates simultaneously. A multi-layer feedforward neural network employing the backpropagation algorithm was used. A number of neural network training tests were performed to obtain an optimum filtering technique of the input/output data of the neural networks. The result of the selection of the filtering technique was confirmed by numerous Fast Fourier Transform (FFT) tests. Training and testing were done on data from TMI-1 nuclear power plant. The results show that the neural network can predict the correct flow rates with an absolute relative error of less than 2%

  20. Wind-type flows in astrophysical jets. I. The initial relativistic acceleration

    International Nuclear Information System (INIS)

    Ferrari, A.; Trussoni, E.; Rosner, R.; Tsinganos, K.; and Instituto di Cosmo-geofisica del Consiglio Nazionale delle Ricerche, Torino, Italy)

    1985-01-01

    We present transonic wind-type solutions of the relativistic quasi--two-dimensional Navier-Stokes fluid equations, which we assume to govern the initial acceleration of the plasma in astrophysical jets emerging from the funnel of an accretion disk orbiting a compact central object. The solutions depend on geometrical parameters characterizing the shape and height of the accretion funnel and on radiation parameters characterizing the luminosity and collimation of the radiation field inside this funnel. The two major results of our study are, first, that rapid expansion of the gas at the exit of the accretion funnel, which interacts synergistically with momentum deposition by radiation pressure, can lead to multiple critical points in the flow and to supersonic speeds very close to the central object; this main feature of our solution is consistent with observations that jets might already be accelerated to relativistic speeds on the sub--0.1 pc distance scale. Second, we show that for suitable values of the parameters characterizing the shape of the accretion funnel and its associated radiation field, multiple transonic solutions for the same initial conditions of the bulk flow speed are obtained, with shock transitions connecting some of these transonic solutions. Because of the sensitivity of the flow to slight variations of the disk and radiation parameters, such discontinuous transitions between distinct transonic flows might be related to the observed phenomenology and variability of active galactic nuclei

  1. Power Flow Management in a High Penetration Wind-Diesel Hybrid Power System with Short-Term Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Drouilhet, S. M.

    1999-07-29

    This paper is intended as an introduction to some of the control challenges faced by developers of high penetration wind-diesel systems, with a focus on the management of power flows in order to achieve precise regulation of frequency and voltage in the face of rapidly varying wind power input and load conditions. The control algorithms presented herein are being implemented in the National Renewable Energy Laboratory (NREL) high penetration wind-diesel system controller that will be installed in the village of Wales, Alaska, in early 2000.

  2. Challenges in Simulation of Aerodynamics, Hydrodynamics, and Mooring-Line Dynamics of Floating Offshore Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Matha, D.; Schlipf, M.; Cordle, A.; Pereira, R.; Jonkman, J.

    2011-10-01

    This paper presents the current major modeling challenges for floating offshore wind turbine design tools and describes aerodynamic and hydrodynamic effects due to rotor and platform motions and usage of non-slender support structures.

  3. Multi-Time Scale Coordinated Scheduling Strategy with Distributed Power Flow Controllers for Minimizing Wind Power Spillage

    Directory of Open Access Journals (Sweden)

    Yi Tang

    2017-11-01

    Full Text Available The inherent variability and randomness of large-scale wind power integration have brought great challenges to power flow control and dispatch. The distributed power flow controller (DPFC has the higher flexibility and capacity in power flow control in the system with wind generation. This paper proposes a multi-time scale coordinated scheduling model with DPFC to minimize wind power spillage. Configuration of DPFCs is initially determined by stochastic method. Afterward, two sequential procedures containing day-head and real-time scales are applied for determining maximum schedulable wind sources, optimal outputs of generating units and operation setting of DPFCs. The generating plan is obtained initially in day-ahead scheduling stage and modified in real-time scheduling model, while considering the uncertainty of wind power and fast operation of DPFC. Numerical simulation results in IEEE-RTS79 system illustrate that wind power is maximum scheduled with the optimal deployment and operation of DPFC, which confirms the applicability and effectiveness of the proposed method.

  4. Natural snowfall reveals large-scale flow structures in the wake of a 2.5-MW wind turbine.

    Science.gov (United States)

    Hong, Jiarong; Toloui, Mostafa; Chamorro, Leonardo P; Guala, Michele; Howard, Kevin; Riley, Sean; Tucker, James; Sotiropoulos, Fotis

    2014-06-24

    To improve power production and structural reliability of wind turbines, there is a pressing need to understand how turbines interact with the atmospheric boundary layer. However, experimental techniques capable of quantifying or even qualitatively visualizing the large-scale turbulent flow structures around full-scale turbines do not exist today. Here we use snowflakes from a winter snowstorm as flow tracers to obtain velocity fields downwind of a 2.5-MW wind turbine in a sampling area of ~36 × 36 m(2). The spatial and temporal resolutions of the measurements are sufficiently high to quantify the evolution of blade-generated coherent motions, such as the tip and trailing sheet vortices, identify their instability mechanisms and correlate them with turbine operation, control and performance. Our experiment provides an unprecedented in situ characterization of flow structures around utility-scale turbines, and yields significant insights into the Reynolds number similarity issues presented in wind energy applications.

  5. Optimal power flow based TU/CHP/PV/WPP coordination in view of wind speed, solar irradiance and load correlations

    International Nuclear Information System (INIS)

    Azizipanah-Abarghooee, Rasoul; Niknam, Taher; Malekpour, Mostafa; Bavafa, Farhad; Kaji, Mahdi

    2015-01-01

    Highlights: • Formulate probabilistic OPF with VPE, multi-fuel options, POZs, FOR of CHP units. • Propose a new powerful optimization method based on enhanced black hole algorithm. • Coordinate of TUs, WPPs, PVs and CHP units together in the proposed problem. • Evaluate the impacts of inputs’ uncertainties and their correlations on the POPF. • Use the 2m + 1 point estimated method. - Abstract: This paper addresses a novel probabilistic optimisation framework for handling power system uncertainties in the optimal power flow (OPF) problem that considers all the essential factors of great impact in the OPF problem. The object is to study and model the correlation and fluctuation of load demands, photovoltaic (PV) and wind power plants (WPPs) which have an important influence on transmission lines and bus voltages. Moreover, as an important tool of saving waste heat energy in the thermoelectric power plant, the power networks share of combined heat and power (CHP) has increased dramatically in the past decade. So, the probabilistic OPF (POPF) problem considering valve point effects, multi-fuel options and prohibited zones of thermal units (TUs) is firstly formulated. The PV, WPP and CHP units are also modeled. Then, a new method utilizing enhanced binary black hole (EBBH) algorithm and 2m + 1 point estimated method is proposed to solve this problem and to handle the random nature of solar irradiance, wind speed and load of consumers. The correlation between input random variables is considered using a correlation matrix. Finally, numerical results are presented and considered regarding the IEEE 118-busses, including PV, WPP, CHP and TU at several busses. The simulation and comparison results obtained demonstrate the broad advantages and feasibility of the suggested framework in the presence of dependent non-Gaussian distribution of random variables

  6. Multi-objective hybrid PSO-APO algorithm based security constrained optimal power flow with wind and thermal generators

    Directory of Open Access Journals (Sweden)

    Kiran Teeparthi

    2017-04-01

    Full Text Available In this paper, a new low level with teamwork heterogeneous hybrid particle swarm optimization and artificial physics optimization (HPSO-APO algorithm is proposed to solve the multi-objective security constrained optimal power flow (MO-SCOPF problem. Being engaged with the environmental and total production cost concerns, wind energy is highly penetrating to the main grid. The total production cost, active power losses and security index are considered as the objective functions. These are simultaneously optimized using the proposed algorithm for base case and contingency cases. Though PSO algorithm exhibits good convergence characteristic, fails to give near optimal solution. On the other hand, the APO algorithm shows the capability of improving diversity in search space and also to reach a near global optimum point, whereas, APO is prone to premature convergence. The proposed hybrid HPSO-APO algorithm combines both individual algorithm strengths, to get balance between global and local search capability. The APO algorithm is improving diversity in the search space of the PSO algorithm. The hybrid optimization algorithm is employed to alleviate the line overloads by generator rescheduling during contingencies. The standard IEEE 30-bus and Indian 75-bus practical test systems are considered to evaluate the robustness of the proposed method. The simulation results reveal that the proposed HPSO-APO method is more efficient and robust than the standard PSO and APO methods in terms of getting diverse Pareto optimal solutions. Hence, the proposed hybrid method can be used for the large interconnected power system to solve MO-SCOPF problem with integration of wind and thermal generators.

  7. Analysis of unsteady flow over Offshore Wind Turbine in combination with different types of foundations

    Science.gov (United States)

    Alesbe, Israa; Abdel-Maksoud, Moustafa; Aljabair, Sattar

    2017-06-01

    Environmental effects have an important influence on Offshore Wind Turbine (OWT) power generation efficiency and the structural stability of such turbines. In this study, we use an in-house Boundary Element (BEM)— panMARE code—to simulate the unsteady flow behavior of a full OWT with various combinations of aerodynamic and hydrodynamic loads in the time domain. This code is implemented to simulate potential flows for different applications and is based on a three-dimensional first-order panel method. Three different OWT configurations consisting of a generic 5 MW NREL rotor with three different types of foundations (Monopile, Tripod, and Jacket) are investigated. These three configurations are analyzed using the RANSE solver which is carried out using ANSYS CFX for validating the corresponding results. The simulations are performed under the same environmental atmospheric wind shear and rotor angular velocity, and the wave properties are wave height of 4 m and wave period of 7.16 s. In the present work, wave environmental effects were investigated firstly for the two solvers, and good agreement is achieved. Moreover, pressure distribution in each OWT case is presented, including detailed information about local flow fields. The time history of the forces at inflow direction and its moments around the mudline at each OWT part are presented in a dimensionless form with respect to the mean value of the last three loads and the moment amplitudes obtained from the BEM code, where the contribution of rotor force is lower in the tripod case and higher in the jacket case and the calculated hydrodynamic load that effect on jacket foundation type is lower than other two cases.

  8. A comparison and assessment of approaches for modelling flow over in-line tube banks

    International Nuclear Information System (INIS)

    Iacovides, Hector; Launder, Brian; West, Alastair

    2014-01-01

    Highlights: • We present wall-resolved LES and URANS simulations of periodic flow in heated in-line tube banks. • Simulations of flow in a confined in-line tube-bank are compared with experimental data. • When pitch-to-diameter (P/D) ratio becomes less than 1.6, the periodic flow becomes skewed. • URANS tested here unable to mimic the periodic flow at P/D = 1.6. • In confined tube banks URANS suggest alternate, in the axial direction, flow deflection. - Abstract: The paper reports experiences from applying alternative strategies for modelling turbulent flow and local heat-transfer coefficients around in-line tube banks. The motivation is the simulation of conditions in the closely packed cross-flow heat exchangers used in advanced gas-cooled nuclear reactors (AGRs). The main objective is the flow simulation in large-scale tube banks with confining walls. The suitability and accuracy of wall-resolved large-eddy simulation (LES) and Unsteady Reynolds-Averaged Navier–Stokes (URANS) approaches are examined for generic, square, in-line tube banks, where experimental data are limited but available. Within the latter approach, both eddy-viscosity and Reynolds-stress-transport models have been tested. The assumption of flow periodicity in all three directions is investigated by varying the domain size. It is found that the path taken by the fluid through the tube-bank configuration differs according to the treatment of turbulence and whether the flow is treated as two- or three-dimensional. Finally, the important effect of confining walls has been examined by making direct comparison with the experiments of the complete test rig of Aiba et al. (1982)

  9. Control of Wind-Induced Vibration of Transmission Tower-Line System by Using a Spring Pendulum

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2015-01-01

    Full Text Available The high-voltage power transmission tower-line system, which is a high flexible structure, is very susceptible to the wind-induced vibrations. This paper proposes the utilization of the internal resonance feature of the spring pendulum to reduce the wind-induced vibration of a transmission tower. The kinetic expression of the spring pendulum system is obtained through Lagrangian equation. The condition of the internal resonance is verified to be λ = 2, in which λ is the ratio of the spring mode frequency over the pendulum mode frequency. A 55 m tower in the Liaoning province is established in SAP2000 to numerically verify the effectiveness of the proposed device. The spring pendulum is modeled using Link element. The wind speed history is generated based on Kaimal spectrum using harmonic superposition method. Results show that, (1 compared with the suspended mass pendulum, the spring pendulum absorbs more energy and reduces the oscillation more effectively and (2 the vibration control performance of the proposed spring pendulum improves as the external wind load increases.

  10. On-line quantile regression in the RKHS (Reproducing Kernel Hilbert Space) for operational probabilistic forecasting of wind power

    International Nuclear Information System (INIS)

    Gallego-Castillo, Cristobal; Bessa, Ricardo; Cavalcante, Laura; Lopez-Garcia, Oscar

    2016-01-01

    Wind power probabilistic forecast is being used as input in several decision-making problems, such as stochastic unit commitment, operating reserve setting and electricity market bidding. This work introduces a new on-line quantile regression model based on the Reproducing Kernel Hilbert Space (RKHS) framework. Its application to the field of wind power forecasting involves a discussion on the choice of the bias term of the quantile models, and the consideration of the operational framework in order to mimic real conditions. Benchmark against linear and splines quantile regression models was performed for a real case study during a 18 months period. Model parameter selection was based on k-fold crossvalidation. Results showed a noticeable improvement in terms of calibration, a key criterion for the wind power industry. Modest improvements in terms of Continuous Ranked Probability Score (CRPS) were also observed for prediction horizons between 6 and 20 h ahead. - Highlights: • New online quantile regression model based on the Reproducing Kernel Hilbert Space. • First application to operational probabilistic wind power forecasting. • Modest improvements of CRPS for prediction horizons between 6 and 20 h ahead. • Noticeable improvements in terms of Calibration due to online learning.

  11. Influences of wind flow on stopover decisions: the case of the reed warbler Acrocephalus scirpaceus in the Western Mediterranean

    Science.gov (United States)

    Barriocanal, C.; Montserrat, D.; Robson, D.

    2002-06-01

    Wind directions measured at two different heights (850 hPa and 700 hPa) and at different hours of the night were analysed during the spring migration passage at a bird stopover site located in the western Mediterranean, in order to evaluate the importance of wind components for a stopover decision. From a huge ringing campaign of bird migration in north-east Spain, data from the reed warbler Acrocephalus scirpaceus have been used for the analysis. From a total of 2,478 reed warblers captured between 1993 and 1997 data recording significant days, with a high number of captures, and decrease days, with few captures, have been selected to develop an analysis of wind direction in relation to stopover and flight resumption. On days with a high capture the winds had mainly a fourth-quadrant flow (from the north, north-west and west), these being mainly head winds. Winds with westerly component (from the north-west, west and south-west), which enhance the flight, account for the majority of the days when there was a low capture of reed warblers. Wind direction therefore appears to be a determining factor for stopover decisions and resumption of flight for the reed warblers at an intermediate stage of their spring migration where topographical characteristics govern the winds.

  12. Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

    Energy Technology Data Exchange (ETDEWEB)

    Guntur, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Schreck, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sorensen, N. N. [Technical Univ. of Denmark, Lyngby (Denmark); Bergami, L. [Technical Univ. of Denmark, Lyngby (Denmark)

    2015-04-22

    It is well known that airfoils under unsteady flow conditions with a periodically varying angle of attack exhibit aerodynamic characteristics different from those under steady flow conditions, a phenomenon commonly known as dynamic stall. It is also well known that the steady aerodynamic characteristics of airfoils in the inboard region of a rotating blade differ from those under steady two-dimensional (2D) flow conditions, a phenomenon commonly known as rotational augmentation. This paper presents an investigation of these two phenomena together in the inboard parts of wind turbine blades. This analysis is carried out using data from three sources: (1) the National Renewable Energy Laboratory’s Unsteady Aerodynamics Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation, (2) data from unsteady Delayed Detached Eddy Simulations (DDES) carried out using the Technical University of Denmark’s in-house flow solver Ellipsys3D, and (3) data from a simplified model based on the blade element momentum method with a dynamic stall subroutine that uses rotationally augmented steady-state polars obtained from steady Phase VI experimental sequences, instead of the traditional 2D nonrotating data. The aim of this work is twofold. First, the blade loads estimated by the DDES simulations are compared to three select cases of the N sequence experimental data, which serves as a validation of the DDES method. Results show reasonable agreement between the two data in two out of three cases studied. Second, the dynamic time series of the lift and the moment polars obtained from the experiments are compared to those from the dynamic stall subroutine that uses the rotationally augmented steady polars. This allowed the differences between the stall phenomenon on the inboard parts of harmonically pitching blades on a rotating wind turbine and the classic dynamic stall representation in 2D flow to be

  13. Data report: the wake of a horizontal-axis wind turbine model, measurements in uniform approach flow and in a simulated atmospheric boundary layer

    NARCIS (Netherlands)

    Talmon, A.M.

    1985-01-01

    Wake effects will cause power loss when wínd turbínes are grouped in so called wind turbine parks. Wind tunnel measurements of the wake of a wind turbíne model are conducted in order to refine calculatíons of wake effects. Wake effects caused by tower and nacelle are studied in uniform flow. Wake

  14. Detailed analysis of the blade root flow of a horizontal axis wind turbine

    Directory of Open Access Journals (Sweden)

    I. Herráez

    2016-07-01

    Full Text Available The root flow of wind turbine blades is subjected to complex physical mechanisms that influence significantly the rotor aerodynamic performance. Spanwise flows, the Himmelskamp effect, and the formation of the root vortex are examples of interrelated aerodynamic phenomena that take place in the blade root region. In this study we address those phenomena by means of particle image velocimetry (PIV measurements and Reynolds-averaged Navier–Stokes (RANS simulations. The numerical results obtained in this study are in very good agreement with the experiments and unveil the details of the intricate root flow. The Himmelskamp effect is shown to delay the stall onset and to enhance the lift force coefficient Cl even at moderate angles of attack. This improvement in the aerodynamic performance occurs in spite of the negative influence of the mentioned effect on the suction peak of the involved blade sections. The results also show that the vortex emanating from the spanwise position of maximum chord length rotates in the opposite direction to the root vortex, which affects the wake evolution. Furthermore, the aerodynamic losses in the root region are demonstrated to take place much more gradually than at the tip.

  15. A Miniature Radial-Flow Wind Turbine Using Piezoelectric Transducers and Magnetic Excitation

    Science.gov (United States)

    Fu, H.; Yeatman, E. M.

    2015-12-01

    This paper presents a miniature radial-flow piezoelectric wind turbine for harvesting airflow energy. The turbine's transduction is achieved by magnetic “plucking”of a piezoelectric beam by the passing rotor. The magnetic coupling is formed by two magnets on the beam's free end and on the rotor plate. Frequency up-conversion is realized by the magnetic excitation, allowing the rotor to rotate at any low frequency while the beam can vibrate at its resonant frequency after each plucking. The operating range of the device is, therefore, expanded by this mechanism. Two arrangements of magnetic orientation have been investigated, showing that the repulsive arrangement has higher output power. The influence of the vertical gap between magnets was also examined, providing guidance for the final design. A prototype was built and tested in a wind tunnel. A peak power output of 159 μW was obtained with a 270 kΩ load at 2.7 m/s airflow speed. The device started working at 3.5 m/s and kept operating when the airflow speed fell to 1.84 m/s.

  16. Design of protective inductors for HVDC transmission line within DC grid offshore wind farms

    DEFF Research Database (Denmark)

    Deng, Fujin; Chen, Zhe

    2013-01-01

    This paper presents fault analysis and protective inductors design for an offshore wind farm, where the power collection system in the wind farm and the power transmission link to the grid adopt high-voltage direct-current (HVDC) technology. This paper focuses on dealing with short-circuit faults...... in the HVDC link between the offshore station and the onshore station. The transient characteristics of the transmission system are analyzed in detail. The criteria of selecting protective inductors are proposed to effectively limit the short-circuit current and avoid the damage to the converters. A dc grid...... offshore wind farm is simulated, and the results demonstrate the effectiveness of the proposed protective inductors design....

  17. Methods for the calculation of axial wave numbers in lined ducts with mean flow

    Science.gov (United States)

    Eversman, W.

    1981-01-01

    A survey is made of the methods available for the calculation of axial wave numbers in lined ducts. Rectangular and circular ducts with both uniform and non-uniform flow are considered as are ducts with peripherally varying liners. A historical perspective is provided by a discussion of the classical methods for computing attenuation when no mean flow is present. When flow is present these techniques become either impractical or impossible. A number of direct eigenvalue determination schemes which have been used when flow is present are discussed. Methods described are extensions of the classical no-flow technique, perturbation methods based on the no-flow technique, direct integration methods for solution of the eigenvalue equation, an integration-iteration method based on the governing differential equation for acoustic transmission, Galerkin methods, finite difference methods, and finite element methods.

  18. An Novel Continuation Power Flow Method Based on Line Voltage Stability Index

    Science.gov (United States)

    Zhou, Jianfang; He, Yuqing; He, Hongbin; Jiang, Zhuohan

    2018-01-01

    An novel continuation power flow method based on line voltage stability index is proposed in this paper. Line voltage stability index is used to determine the selection of parameterized lines, and constantly updated with the change of load parameterized lines. The calculation stages of the continuation power flow decided by the angle changes of the prediction of development trend equation direction vector are proposed in this paper. And, an adaptive step length control strategy is used to calculate the next prediction direction and value according to different calculation stages. The proposed method is applied clear physical concept, and the high computing speed, also considering the local characteristics of voltage instability which can reflect the weak nodes and weak area in a power system. Due to more fully to calculate the PV curves, the proposed method has certain advantages on analysing the voltage stability margin to large-scale power grid.

  19. AIR FLOW AND ENVIRONMENTAL WIND VISUALIZATION USING A CW DIODE PUMPED FREQUENCY DOUBLED Nd:YAG Laser

    Directory of Open Access Journals (Sweden)

    Mircea UDREA

    2009-09-01

    Full Text Available Preliminary results obtained in developing a visualisation technique for non-invasive analysis of air flow inside INCAS subsonic wind tunnel and its appendages are presented. The visualisation technique is based on using a green light sheet generated by a continuous wave (cw longitudinally diode pumped and frequency doubled Nd:YAG laser. The output laser beam is expanded on one direction and collimated on rectangular direction. The system is tailored to the requirements of qualitative analysis and vortex tracking requirements inside the INCAS 2.5m x 2.0m subsonic wind tunnel test section, for measurements performed on aircraft models. Also the developed laser techniques is used for non-invasive air flow field analysis into environmental facilities settling room (air flow calming area. Quantitative analysis is enabled using special image processing tools upon movies and pictures obtained during the experiments. The basic experimental layout in the wind tunnel takes advantage of information obtained from the investigation of various aircraft models using the developed visualisation technique. These results are further developed using a Particle Imaging Velocimetry (PIV experimental technique.The focus is on visualisation techniques to be used for wind flow characterization at different altitudes in indus-trial and civil buildings areas using a light sheet generated by a Nd:YAG cw pumped and doubled laser at 532 nm wave-length. The results are important for prevention of biological/chemical disasters such as spreading of extremely toxic pol-lutants due to wind. Numerical simulations of wind flow and experimental visualisation results are compared. A good agreement between these results is observed.

  20. Coping with flow: behavior, neurophysiology and modeling of the fish lateral line system.

    Science.gov (United States)

    Mogdans, Joachim; Bleckmann, Horst

    2012-12-01

    With the mechanosensory lateral line fish perceive water motions relative to their body surface and local pressure gradients. The lateral line plays an important role in many fish behaviors including the detection and localization of dipole sources and the tracking of prey fish. The sensory units of the lateral line are the neuromasts which are distributed across the surface of the animal. Water motions are received and transduced into neuronal signals by the neuromasts. These signals are conveyed by afferent nerve fibers to the fish brain and processed by lateral line neurons in parts of the brainstem, cerebellum, midbrain, and forebrain. In the cerebellum, midbrain, and forebrain, lateral line information is integrated with sensory information from other modalities. The present review introduces the peripheral morphology of the lateral line, and describes our understanding of lateral line physiology and behavior. It focuses on recent studies that have investigated: how fish behave in unsteady flow; what kind of sensory information is provided by flow; and how fish use and process this information. Finally, it reports new theoretical and biomimetic approaches to understand lateral line function.

  1. Sensorless Control for the EVT-Based New Dual Power Flow Wind Energy Conversion System

    Directory of Open Access Journals (Sweden)

    Ying Zhu

    2017-06-01

    Full Text Available The dual power flow wind energy conversion system (DPF-WECS is a novel system which is based on the electrical variable transmission (EVT machine. The proposed sensorless control for the DPF-WECS is based on the model reference adaptive system (MRAS observer by combining the sliding mode (SM theory. The SM-MRAS observer is on account of the calculations without the requirement of the proportional-integral (PI loop which exists in the classical MRAS observer. Firstly, the sensorless algorithm is applied in the maximum power point tracking (MPPT control considering the torque loss for the outer rotor of the EVT. Secondly, the sensorless control is adopted for the inner rotor control of the EVT machine. The proposed sensorless control method based on the SM-MRAS for the DPF-WECS is verified by the simulation and experimental results.

  2. Design and evaluation of an aeroacoustic wind tunnel for measurement of axial flow fans.

    Science.gov (United States)

    Bilka, M; Anthoine, J; Schram, C

    2011-12-01

    An anechoic wind tunnel dedicated to fan self-noise studies has been designed and constructed at the von Karman Institute The multi-chamber, mass flow driven design allows for all fan performance characteristics, aerodynamic quantities (e.g., wake turbulence measurements), and acoustic properties to be assessed in the same facility with the same conditions. The acoustic chamber performance is assessed using the optimum reference method and found to be within the ISO 3745 standards down to 150 Hz for pure tone and broadband source mechanisms. The additional influence of installation effects of an aerodynamic inlet was found to create a scattered sound field only near the source location, while still providing good anechoic results at more distant sound pressure measurement positions. It was found to have inflow properties, span-wise uniformity, and low turbulence intensity, consistent with those desired for fan self-noise studies. © 2011 Acoustical Society of America

  3. Research on Flow Field Perception Based on Artificial Lateral Line Sensor System

    Directory of Open Access Journals (Sweden)

    Guijie Liu

    2018-03-01

    Full Text Available In nature, the lateral line of fish is a peculiar and important organ for sensing the surrounding hydrodynamic environment, preying, escaping from predators and schooling. In this paper, by imitating the mechanism of fish lateral canal neuromasts, we developed an artificial lateral line system composed of micro-pressure sensors. Through hydrodynamic simulations, an optimized sensor structure was obtained and the pressure distribution models of the lateral surface were established in uniform flow and turbulent flow. Carrying out the corresponding underwater experiment, the validity of the numerical simulation method is verified by the comparison between the experimental data and the simulation results. In addition, a variety of effective research methods are proposed and validated for the flow velocity estimation and attitude perception in turbulent flow, respectively and the shape recognition of obstacles is realized by the neural network algorithm.

  4. Effect of Flow on Cultured Cell at Micro-Pattern of Ridge Lines

    Directory of Open Access Journals (Sweden)

    Haruka Hino

    2017-10-01

    Full Text Available A flow channel with a micro-pattern of ridge lines of a scaffold has been designed to study quantitatively the effect of flow on an oriented cell in vitro. The lines of parallel micro ridges (0.001 mm height, 0.003 mm width, and 0.003 mm interval are made by the lithography technique on the lower surface of the channel as the scaffold to make orientation of each cell. Variation is made about the angle between the longitudinal direction of the ridge line and the direction of the flow: zero, 0.79 and 1.6 rad. The suspension of C2C12 (mouse myoblast cell line was injected to the channel, and incubated for two hours on the micro ridges before the flow test for four hours. The flow rate of 3/hour is controlled by a syringe pump to make variation of the wall shear stress of < 3 Pa. The action of each cell adhered on the micro pattern was analyzed at the time lapse images. The experimental results show that both the migration and the deformation of each myoblast along the micro ridge are restricted by the wall shear stress higher than 3 Pa.

  5. IEA-Task 31 WAKEBENCH: Towards a protocol for wind farm flow model evaluation. Part 1: Flow-over-terrain models

    DEFF Research Database (Denmark)

    Rodrigo, Javier Sanz; Gancarski, Pawel; Arroyo, Roberto Chavez

    2014-01-01

    The IEA Task 31 Wakebench is setting up a framework for the evaluation of wind farm flow models operating at microscale level. The framework consists on a model evaluation protocol integrated on a web-based portal for model benchmarking (www.windbench.net). This paper provides an overview of the ...

  6. Experimental tests of the effect of rotor diameter ratio and blade number to the cross-flow wind turbine performance

    Science.gov (United States)

    Susanto, Sandi; Tjahjana, Dominicus Danardono Dwi Prija; Santoso, Budi

    2018-02-01

    Cross-flow wind turbine is one of the alternative energy harvester for low wind speeds area. Several factors that influence the power coefficient of cross-flow wind turbine are the diameter ratio of blades and the number of blades. The aim of this study is to find out the influence of the number of blades and the diameter ratio on the performance of cross-flow wind turbine and to find out the best configuration between number of blades and diameter ratio of the turbine. The experimental test were conducted under several variation including diameter ratio between outer and inner diameter of the turbine and number of blades. The variation of turbine diameter ratio between inner and outer diameter consisted of 0.58, 0.63, 0.68 and 0.73 while the variations of the number of blades used was 16, 20 and 24. The experimental test were conducted under certain wind speed which are 3m/s until 4 m/s. The result showed that the configurations between 0.68 diameter ratio and 20 blade numbers is the best configurations that has power coefficient of 0.049 and moment coefficient of 0.185.

  7. The lateral line is necessary for blind cavefish rheotaxis in non-uniform flow.

    Science.gov (United States)

    Kulpa, Matthew; Bak-Coleman, Joseph; Coombs, Sheryl

    2015-05-15

    When encountering a unidirectional flow, many fish exhibit an unconditioned orienting response known as rheotaxis. This multisensory behavior can reportedly involve visual, vestibular, tactile and lateral line cues. However, the precise circumstances under which different senses contribute are still unclear and there is considerable debate, in particular, about the contributions of the lateral line. In this study, we investigate the rheotactic behavior of blind cavefish under conditions of spatially non-uniform flow (a jet stream), which in theory, should promote reliance on lateral line cues. The behavior of individual lateral line enabled and disabled fish was videorecorded under IR light in a square arena that prevented streamwise biases and that contained a narrow jet stream in the center of the tank. Whereas the stream's peak velocity (8 cm s(-1)) declined very little in the streamwise direction, it declined steeply in the cross-stream direction (∼3-4.5 cm s(-1) cm(-1)). Lateral line enabled fish showed higher levels of orientation to the stream and its source (a 1-cm-wide nozzle) when in the central (jet stream) region of the tank compared with surrounding regions, whereas lateral line disabled fish showed random orientations in all regions of the tank. The results of this study indicate that the spatial characteristics of flow play a role in determining the sensory basis of rheotaxis. © 2015. Published by The Company of Biologists Ltd.

  8. Stochastic Dynamic AC Optimal Power Flow Based on a Multivariate Short-Term Wind Power Scenario Forecasting Model

    Directory of Open Access Journals (Sweden)

    Wenlei Bai

    2017-12-01

    Full Text Available The deterministic methods generally used to solve DC optimal power flow (OPF do not fully capture the uncertainty information in wind power, and thus their solutions could be suboptimal. However, the stochastic dynamic AC OPF problem can be used to find an optimal solution by fully capturing the uncertainty information of wind power. That uncertainty information of future wind power can be well represented by the short-term future wind power scenarios that are forecasted using the generalized dynamic factor model (GDFM—a novel multivariate statistical wind power forecasting model. Furthermore, the GDFM can accurately represent the spatial and temporal correlations among wind farms through the multivariate stochastic process. Fully capturing the uncertainty information in the spatially and temporally correlated GDFM scenarios can lead to a better AC OPF solution under a high penetration level of wind power. Since the GDFM is a factor analysis based model, the computational time can also be reduced. In order to further reduce the computational time, a modified artificial bee colony (ABC algorithm is used to solve the AC OPF problem based on the GDFM forecasting scenarios. Using the modified ABC algorithm based on the GDFM forecasting scenarios has resulted in better AC OPF’ solutions on an IEEE 118-bus system at every hour for 24 h.

  9. Effect of Wind Angle Direction on Carbon Monoxide (CO) Concentration Dispersion on Traffic Flow in Padang City

    Science.gov (United States)

    Bachtiar, V. S.; Purnawan, P.; Afrianita, R.; Dahlia, N.

    2018-01-01

    This study aims to analyze the relationship between CO concentration and wind direction. Wind direction in this context is the wind angle to the road on the traffic flow in Padang City. Sampling of CO concentration was conducted for 9 days at 3 monitoring points (each 3-day point) representing the wind angle to the road (a) i.e. at Jend. A. Yani road (0 degrees), Andalas road (30 degrees) and Prof. Dr. Hamka road (60 degrees), using impinger and analyzed by spectrophotometer. The results of the research in the three monitoring sites showed that the concentration of CO ranged between 137.217 and 600.525 μg/Nm3. The highest and lowest concentrations respectively on Prof. Dr. Hamka road and Jend. A. Yani road. The sampling showed that CO concentrations will be decreased if wind direction is changed from perpendicular wind direction (a 90°) to a 60°, 30°, and 0° respectively by 64.62%, 37.77% and 27.09%. It can be concluded that the wind angle direction to the road affects the CO concentrations in the roadside.

  10. Base line studies North Sea wind farms: Final report pelagic fish

    NARCIS (Netherlands)

    Grift, R.E.; Tulp, I.Y.M.; Ybema, M.S.; Couperus, A.S.

    2004-01-01

    The Dutch government has decided to allow the construction of a Near Shore Wind Farm (NSW) demonstration project under the condition that a monitoring programme on - among other things - the ecological impacts is carried out. The Dutch government is responsible for providing a thorough description

  11. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...... of windhe interaction between wind and structures, where it is shown that wind loading depends strongly on this interaction...

  12. A bio-inspired real-time capable artificial lateral line system for freestream flow measurements.

    Science.gov (United States)

    Abels, C; Qualtieri, A; De Vittorio, M; Megill, W M; Rizzi, F

    2016-06-03

    To enhance today's artificial flow sensing capabilities in aerial and underwater robotics, future robots could be equipped with a large number of miniaturized sensors distributed over the surface to provide high resolution measurement of the surrounding fluid flow. In this work we show a linear array of closely separated bio-inspired micro-electro-mechanical flow sensors whose sensing mechanism is based on a piezoresistive strain-gauge along a stress-driven cantilever beam, mimicking the biological superficial neuromasts found in the lateral line organ of fishes. Aiming to improve state-of-the-art flow sensing capability in autonomously flying and swimming robots, our artificial lateral line system was designed and developed to feature multi-parameter freestream flow measurements which provide information about (1) local flow velocities as measured by the signal amplitudes from the individual cantilevers as well as (2) propagation velocity, (3) linear forward/backward direction along the cantilever beam orientation and (4) periodicity of pulses or pulse trains determined by cross-correlating sensor signals. A real-time capable cross-correlation procedure was developed which makes it possible to extract freestream flow direction and velocity information from flow fluctuations. The computed flow velocities deviate from a commercial system by 0.09 m s(-1) at 0.5 m s(-1) and 0.15 m s(-1) at 1.0 m s(-1) flow velocity for a sampling rate of 240 Hz and a sensor distance of 38 mm. Although experiments were performed in air, the presented flow sensing system can be applied to underwater vehicles as well, once the sensors are embedded in a waterproof micro-electro-mechanical systems package.

  13. Optimal Allocation of Wind Turbines in Active Distribution Networks by Using Multi-Period Optimal Power Flow and Genetic Algorithms

    DEFF Research Database (Denmark)

    Siano, P.; Chen, Peiyuan; Chen, Zhe

    2012-01-01

    a hybrid optimization method that aims of maximizing the Net Present Value related to the Investment made by Wind Turbines developers in an active distribution network. The proposed network combines a Genetic Algorithm with a multi-period optimal power flow. The method, integrating active management...

  14. A Line Search Multilevel Truncated Newton Algorithm for Computing the Optical Flow

    Directory of Open Access Journals (Sweden)

    Lluís Garrido

    2015-06-01

    Full Text Available We describe the implementation details and give the experimental results of three optimization algorithms for dense optical flow computation. In particular, using a line search strategy, we evaluate the performance of the unilevel truncated Newton method (LSTN, a multiresolution truncated Newton (MR/LSTN and a full multigrid truncated Newton (FMG/LSTN. We use three image sequences and four models of optical flow for performance evaluation. The FMG/LSTN algorithm is shown to lead to better optical flow estimation with less computational work than both the LSTN and MR/LSTN algorithms.

  15. Transmission Line Ampacity Improvements of AltaLink Wind Plant Overhead Tie-Lines Using Weather-Based Dynamic Line Rating

    Energy Technology Data Exchange (ETDEWEB)

    Bhattarai, Bishnu P.; Gentle, Jake P.; Hill, Porter; McJunkin, Tim; Myers, Kurt S.; Abbound, Alex; Renwick, Rodger; Hengst, David

    2017-07-01

    Abstract—Overhead transmission lines (TLs) are conventionally given seasonal ratings based on conservative environmental assumptions. Such an approach often results in underutilization of the line ampacity as the worst conditions prevail only for a short period over a year/season. We presents dynamic line rating (DLR) as an enabling smart grid technology that adaptively computes ratings of TLs based on local weather conditions to utilize additional headroom of existing lines. In particular, general line ampacity state solver utilizes measured weather data for computing the real-time thermal rating of the TLs. The performance of the presented method is demonstrated from a field study of DLR technology implementation on four TL segments at AltaLink, Canada. The performance is evaluated and quantified by comparing the existing static and proposed dynamic line ratings, and the potential benefits of DLR for enhanced transmission assets utilization. For the given line segments, the proposed DLR results in real-time ratings above the seasonal static ratings for most of the time; up to 95.1% of the time, with a mean increase of 72% over static rating.

  16. Computer analysis of flow perturbations generated by placement of choke bumps in a wind tunnel

    Science.gov (United States)

    Campbell, R. L.

    1981-01-01

    An inviscid analytical study was conducted to determine the upstream flow perturbations caused by placing choke bumps in a wind tunnel. A computer program based on the stream-tube curvature method was used to calculate the resulting flow fields for a nominal free-stream Mach number range of 0.6 to 0.9. The choke bump geometry was also varied to investigate the effect of bump shape on the disturbance produced. Results from the study indicate that a region of significant variation from the free-stream conditions exists upstream of the throat of the tunnel. The extent of the disturbance region was, as a rule, dependent on Mach number and the geometry of the choke bump. In general, the upstream disturbance distance decreased for increasing nominal free-stream Mach number and for decreasing length-to-height ratio of the bump. A polynomial-curve choke bump usually produced less of a disturbance than did a circular-arc bump and going to an axisymmetric configuration (modeling choke bumps on all the tunnel walls) generally resulted in a lower disturbance than with the corresponding two dimensional case.

  17. Flow cytometric analysis of microbial contamination in food industry technological lines--initial study.

    Science.gov (United States)

    Józwa, Wojciech; Czaczyk, Katarzyna

    2012-04-02

    Flow cytometry constitutes an alternative for traditional methods of microorganisms identification and analysis, including methods requiring cultivation step. It enables the detection of pathogens and other microorganisms contaminants without the need to culture microbial cells meaning that the sample (water, waste or food e.g. milk, wine, beer) may be analysed directly. This leads to a significant reduction of time required for analysis allowing monitoring of production processes and immediate reaction in case of contamination or any disruption occurs. Apart from the analysis of raw materials or products on different stages of manufacturing process, the flow cytometry seems to constitute an ideal tool for the assessment of microbial contamination on the surface of technological lines. In the present work samples comprising smears from 3 different surfaces of technological lines from fruit and vegetable processing company from Greater Poland were analysed directly with flow cytometer. The measured parameters were forward and side scatter of laser light signals allowing the estimation of microbial cell contents in each sample. Flow cytometric analysis of the surface of food industry production lines enable the preliminary evaluation of microbial contamination within few minutes from the moment of sample arrival without the need of sample pretreatment. The presented method of fl ow cytometric initial evaluation of microbial state of food industry technological lines demonstrated its potential for developing a robust, routine method for the rapid and labor-saving detection of microbial contamination in food industry.

  18. Actuator Line/Navier-Stokes Computations for Flows past the Yawed MEXICO Rotor

    DEFF Research Database (Denmark)

    Shen, Wen Zhong; Sørensen, Jens Nørkær; Yang, H.

    2011-01-01

    In the paper the Actuator Line/Navier-Stokes model has been used to simulate flows past the yawed MEXICO rotor. The computed loads as well as the velocity field behind the yawed rotor are compared to detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project...

  19. In-line holography for flow and cavitation visualization on hydrofoils and for nuclei measurements

    NARCIS (Netherlands)

    Renesse, R.L. van; Meulen, J.H.J. van der

    1980-01-01

    The boundary layer flow about two hydrofoils and the appearance of cavitation are investigated by means of in-line holography. Practical details on the hologram resolution and data collection time for nuclei size analysis are given. It is shown that the appearance of cavitation on the hydrofoils is

  20. Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow.

    Science.gov (United States)

    Hu, L H; Huo, R; Yang, D

    2009-07-15

    The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

  1. Superluminous Transients at AGN Centers from Interaction between Black Hole Disk Winds and Broad-line Region Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Moriya, Takashi J.; Tanaka, Masaomi; Ohsuga, Ken [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Morokuma, Tomoki, E-mail: takashi.moriya@nao.ac.jp [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

    2017-07-10

    We propose that superluminous transients that appear at central regions of active galactic nuclei (AGNs) such as CSS100217:102913+404220 (CSS100217) and PS16dtm, which reach near- or super-Eddington luminosities of the central black holes, are powered by the interaction between accretion-disk winds and clouds in broad-line regions (BLRs) surrounding them. If the disk luminosity temporarily increases by, e.g., limit–cycle oscillations, leading to a powerful radiatively driven wind, strong shock waves propagate in the BLR. Because the dense clouds in the AGN BLRs typically have similar densities to those found in SNe IIn, strong radiative shocks emerge and efficiently convert the ejecta kinetic energy to radiation. As a result, transients similar to SNe IIn can be observed at AGN central regions. Since a typical black hole disk-wind velocity is ≃0.1 c , where c is the speed of light, the ejecta kinetic energy is expected to be ≃10{sup 52} erg when ≃1 M {sub ⊙} is ejected. This kinetic energy is transformed to radiation energy in a timescale for the wind to sweep up a similar mass to itself in the BLR, which is a few hundred days. Therefore, both luminosities (∼10{sup 44} erg s{sup −1}) and timescales (∼100 days) of the superluminous transients from AGN central regions match those expected in our interaction model. If CSS100217 and PS16dtm are related to the AGN activities triggered by limit–cycle oscillations, they become bright again in coming years or decades.

  2. Wind-tunnel study of the wake behind a vertical axis wind turbine in a boundary layer flow using stereoscopic particle image velocimetry

    Science.gov (United States)

    Rolin, V.; Porté-Agel, F.

    2015-06-01

    Stereo particle image velocimetry is used in a wind-tunnel to study boundary layer effects in the wake behind a vertical axis wind turbine. The turbine is a three-bladed giromill with a solidity of 1.18. The wake is studied for a tip speed ratio of 2 and an average chord Reynolds number of 1.6 × 104. The velocity deficit and turbulence levels in the horizontal plane are observed to be strongly asymmetrical with two strong peaks corresponding to the two halves of the rotor where blades move either towards the oncoming flow or away from it. The stronger peak is measured behind the blades moving upstream, however this region also benefits from a greater rate of re-energization. Due to the incoming boundary layer profile, momentum is also entrained downwards into the wake from above and aids with the recovery of the core of the wake.

  3. Velocity-intermittency structure for wake flow of the pitched single wind turbine under different inflow conditions

    Science.gov (United States)

    Crist, Ryan; Cal, Raul Bayoan; Ali, Naseem; Rockel, Stanislav; Peinke, Joachim; Hoelling, Michael

    2017-11-01

    The velocity-intermittency quadrant method is used to characterize the flow structure of the wake flow in the boundary layer of a wind turbine array. Multifractal framework presents the intermittency as a pointwise Hölder exponent. A 3×3 wind turbine array tested experimentally provided a velocity signal at a 21×9 downstream location, measured via hot-wire anemometry. The results show a negative correlation between the velocity and the intermittency at the hub height and bottom tip, whereas the top tip regions show a positive correlation. Sweep and ejection based on the velocity and intermittency are dominant downstream from the rotor. The pointwise results reflect large-scale organization of the flow and velocity-intermittency events corresponding to a foreshortened recirculation region near the hub height and the bottom tip.

  4. HB-Line Dissolver Dilution Flows and Dissolution Capability with Dissolver Charge Chute Cover Off

    International Nuclear Information System (INIS)

    Hallman, D.F.

    2003-01-01

    A flow test was performed in Scrap Recovery of HB-Line to document the flow available for hydrogen dilution in the dissolvers when the charge chute covers are removed. Air flow through the dissolver charge chutes, with the covers off, was measured. A conservative estimate of experimental uncertainty was subtracted from the results. After subtraction, the test showed that there is 20 cubic feet per minute (cfm) air flow through the dissolvers during dissolution with a glovebox exhaust fan operating, even with the scrubber not operating. This test also showed there is 6.6 cfm air flow through the dissolvers, after subtraction of experimental uncertainty if the scrubber and the glovebox exhaust fans are not operating. Three H-Canyon exhaust fans provide sufficient motive force to give this 6.6 cfm flow. Material charged to the dissolver will be limited to chemical hydrogen generation rates that will be greater than or equal to 25 percent of the Lower Flammability Limit (LFL) during normal operations. The H-Canyon fans will maintain hydrogen below LFL if electrical power is lost. No modifications are needed in HB-Line Scrap Recovery to ensure hydrogen is maintained less that LFL if the scrubber and glovebox exhaust fans are not operating

  5. Application of PSAT to Load Flow Analysis with STATCOM under Load Increase Scenario and Line Contingencies

    Science.gov (United States)

    Telang, Aparna S.; Bedekar, P. P.

    2017-09-01

    Load flow analysis is the initial and essential step for any power system computation. It is required for choosing better options for power system expansion to meet with ever increasing load demand. Implementation of Flexible AC Transmission System (FACTS) device like STATCOM, in the load flow, which is having fast and very flexible control, is one of the important tasks for power system researchers. This paper presents a simple and systematic approach for steady state power flow calculations with FACTS controller, static synchronous compensator (STATCOM) using command line usage of MATLAB tool-power system analysis toolbox (PSAT). The complexity of MATLAB language programming increases due to incorporation of STATCOM in an existing Newton-Raphson load flow algorithm. Thus, the main contribution of this paper is to show how command line usage of user friendly MATLAB tool, PSAT, can extensively be used for quicker and wider interpretation of the results of load flow with STATCOM. The novelty of this paper lies in the method of applying the load increase pattern, where the active and reactive loads have been changed simultaneously at all the load buses under consideration for creating stressed conditions for load flow analysis with STATCOM. The performance have been evaluated on many standard IEEE test systems and the results for standard IEEE-30 bus system, IEEE-57 bus system, and IEEE-118 bus system are presented.

  6. A multiphase flow meter for the on-line determination of the flow rates of oil, water and gas

    International Nuclear Information System (INIS)

    Roach, G.J.; Watt, J.S.

    1997-01-01

    Multiphase mixtures of crude oil, formation water and gas are carried in pipelines from oil wells to production facilities. Multiphase flow meters (MFMs) are being developed to determine the flow rates of each component of the heterogeneous mixture in the pipeline. CSIRO Minerals has developed and field tested a gamma-ray MFM for the on-line determination of the flow rates of heterogeneous mixtures of oil, water and gas in pipelines. It consists of two specialised gamma-ray transmission gauges, and pressure and temperature sensors, mounted on the pipeline carrying the full flow of the production stream. The MFM separately measures liquids and gas flow rates, and the volume ratio of water and liquids (water cut). The MFM has been trialled at three offshore production facilities in Australia. In each, the MFM was mounted on the pipeline between the test manifold and the test separator. The multiphase streams from the various wells feeding to the platform were sequentially routed past the MFM. The MFM and test separator outputs were compared using regression analysis. The flow rates of oil, water and gas were each determined to relative errors in the range of 5-10% . The MFM has been in routine use on the West Kingfish platform in the Bass Strait since November 1994. The MFM was recently tested over a wide range of flow conditions at a Texaco flow facility near Houston. Water cut, based on pre-trial calibration, was determined to 2% rms over the range 0-100% water cut. The liquids and gas flow results were interpreted based on slip correlations obtained from comparison of the MFM and Texaco flows. Using these, the relative errors were respectively 6.6% for liquid flow, 6.2% for gas, 8% for oil and 8% for water. The MFM is licensed to Kvaerner FSSL of Aberdeen. Kvaerner will supply the gamma-ray MFM for both platform and subsea use. Technology transfer commenced in December 1996, and Kvaerner completed the manufacture of the first MFM in August 1997

  7. A multiphase flow meter for the on-line determination of the flow rates of oil, water and gas

    Energy Technology Data Exchange (ETDEWEB)

    Roach, G.J.; Watt, J.S. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), Menai, NSW (Australia). Divsion of Minerals

    1997-10-01

    Multiphase mixtures of crude oil, formation water and gas are carried in pipelines from oil wells to production facilities. Multiphase flow meters (MFMs) are being developed to determine the flow rates of each component of the heterogeneous mixture in the pipeline. CSIRO Minerals has developed and field tested a gamma-ray MFM for the on-line determination of the flow rates of heterogeneous mixtures of oil, water and gas in pipelines. It consists of two specialised gamma-ray transmission gauges, and pressure and temperature sensors, mounted on the pipeline carrying the full flow of the production stream. The MFM separately measures liquids and gas flow rates, and the volume ratio of water and liquids (water cut). The MFM has been trialled at three offshore production facilities in Australia. In each, the MFM was mounted on the pipeline between the test manifold and the test separator. The multiphase streams from the various wells feeding to the platform were sequentially routed past the MFM. The MFM and test separator outputs were compared using regression analysis. The flow rates of oil, water and gas were each determined to relative errors in the range of 5-10% . The MFM has been in routine use on the West Kingfish platform in the Bass Strait since November 1994. The MFM was recently tested over a wide range of flow conditions at a Texaco flow facility near Houston. Water cut, based on pre-trial calibration, was determined to 2% rms over the range 0-100% water cut. The liquids and gas flow results were interpreted based on slip correlations obtained from comparison of the MFM and Texaco flows. Using these, the relative errors were respectively 6.6% for liquid flow, 6.2% for gas, 8% for oil and 8% for water. The MFM is licensed to Kvaerner FSSL of Aberdeen. Kvaerner will supply the gamma-ray MFM for both platform and subsea use. Technology transfer commenced in December 1996, and Kvaerner completed the manufacture of the first MFM in August 1997 4 refs., 7 figs.

  8. Solar line Lsub(α) profile and an interstellar wind dynamics

    International Nuclear Information System (INIS)

    Burgin, M.S.

    1978-01-01

    Analytical theory of interstellar hydrogen atom motion into the region of solar Lsub(α)-radiation is given. Hydrogen distribution in the Solar system is calculated with an account of the Lsub(α) solar line profile difference from a flat one. The effect of the profile form on the scattered radiation intensity is estimated. Calculation errors of the scattered radiation intensity, connected with the difference between a line profile and a flat one, do not exceed 5% for the real Lsub(α) solar line profile

  9. Raindrop and flow interactions for interrill erosion with wind-driven rain

    NARCIS (Netherlands)

    Erpul, G.; Gabriels, D.; Darell Norton, L.; Dennis, C.; Huang, C.H.; Visser, S.M.

    2013-01-01

    Wind-driven rain (WDR) experiments were conducted to evaluate the interrill component of the Water Erosion Prediction Project model with a two-dimensional experimental set-up in a wind tunnel. Synchronized wind and rain simulations were applied to soil surfaces on windward and leeward slopes of 7,

  10. Miniaturized compact water-cooled pitot-pressure probe for flow-field surveys in hypersonic wind tunnels

    Science.gov (United States)

    Ashby, George C.

    1988-01-01

    An experimental investigation of the design of pitot probes for flowfield surveys in hypersonic wind tunnels is reported. The results show that a pitot-pressure probe can be miniaturized for minimum interference effects by locating the transducer in the probe support body and water-cooling it so that the pressure-settling time and transducer temperature are compatible with hypersonic tunnel operation and flow conditions. Flowfield surveys around a two-to-one elliptical cone model in a 20-inch Mach 6 wind tunnel using such a probe show that probe interference effects are essentially eliminated.

  11. Dynamic Stability Enhancement and Power Flow Control of a Hybrid Wind and Marine-Current Farm Using SMES

    DEFF Research Database (Denmark)

    Wang, Li; Chen, Shiang-Shong; Lee, Wei-Jen

    2009-01-01

    This paper presents a control scheme based on a superconducting magnetic energy storage (SMES) unit to achieve both power flow control and damping enhancement of a novel hybrid wind and marine-current farm (MCF) connected to a large power grid. The performance of the studied wind farm (WF......) is simulated by an equivalent 80-MW induction generator (IG) while an equivalent 60-MW IG is employed to simulate the characteristics of theMCF. A damping controller for the SMES unit is designed by using modal control theory to contribute effective damping characteristics to the studied combined WF and MCF...

  12. Final Report for ALCC Allocation: Predictive Simulation of Complex Flow in Wind Farms

    Energy Technology Data Exchange (ETDEWEB)

    Barone, Matthew F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ananthan, Shreyas [National Renewable Energy Lab. (NREL), Golden, CO (United States); Churchfield, Matt [National Renewable Energy Lab. (NREL), Golden, CO (United States); Domino, Stefan P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Henry de Frahan, Marc [National Renewable Energy Lab. (NREL), Golden, CO (United States); Knaus, Robert C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Melvin, Jeremy [Univ. of Texas, Austin, TX (United States); Moser, Robert [Univ. of Texas, Austin, TX (United States); Sprague, Michael [National Renewable Energy Lab. (NREL), Golden, CO (United States); Thomas, Stephen [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-08-01

    This report documents work performed using ALCC computing resources granted under a proposal submitted in February 2016, with the resource allocation period spanning the period July 2016 through June 2017. The award allocation was 10.7 million processor-hours at the National Energy Research Scientific Computing Center. The simulations performed were in support of two projects: the Atmosphere to Electrons (A2e) project, supported by the DOE EERE office; and the Exascale Computing Project (ECP), supported by the DOE Office of Science. The project team for both efforts consists of staff scientists and postdocs from Sandia National Laboratories and the National Renewable Energy Laboratory. At the heart of these projects is the open-source computational-fluid-dynamics (CFD) code, Nalu. Nalu solves the low-Mach-number Navier-Stokes equations using an unstructured- grid discretization. Nalu leverages the open-source Trilinos solver library and the Sierra Toolkit (STK) for parallelization and I/O. This report documents baseline computational performance of the Nalu code on problems of direct relevance to the wind plant physics application - namely, Large Eddy Simulation (LES) of an atmospheric boundary layer (ABL) flow and wall-modeled LES of a flow past a static wind turbine rotor blade. Parallel performance of Nalu and its constituent solver routines residing in the Trilinos library has been assessed previously under various campaigns. However, both Nalu and Trilinos have been, and remain, in active development and resources have not been available previously to rigorously track code performance over time. With the initiation of the ECP, it is important to establish and document baseline code performance on the problems of interest. This will allow the project team to identify and target any deficiencies in performance, as well as highlight any performance bottlenecks as we exercise the code on a greater variety of platforms and at larger scales. The current study is

  13. Volumetric characterization of the flow over miniature wind farms: An experimental study

    Science.gov (United States)

    Wing, Lai; Troolin, Dan; Hyun, Jin Kim; Tobin, Nicolas; Zuniga Zamalloa, Carlo; Chamorro, Leonardo P.

    2014-11-01

    An internal boundary layer is known to develop from the interaction between wind farms and the atmospheric boundary layer. It possesses characteristic features able to modulate the turbulence dynamics over large regions and eventually modify the micro climate in the vicinity of the wind farm. In this study, we examine the structure of the turbulence above various miniature wind farm configurations using 3D Particle Image velocimetry (PIV). Each miniature wind farm is placed in the boundary-layer wind tunnel at the Mechanical Science Engineering, UIUC. The turbines are fabricated using 3D printing and have a loading system that controls their tip-speed ratio and allows for characterizing the loads. Volumetric PIV is performed at various locations over and downstream a series of wind farm layouts. High-order turbulence statistics, turbulence structure and characteristic coherent motions are obtained and discussed in terms of the wind farm layout.

  14. Two-phase flow phenomena in broken recirculation line of BWR

    International Nuclear Information System (INIS)

    Kato, Masami; Arai, Kenji; Narabayashi, Tadashi; Amano, Osamu.

    1986-01-01

    When a primary recirculation line of BWR is ruptured, a primary recirculation pump may be subjected to very high velocity two-phase flow and its speed may be accelerated by this flow. It is important for safety evaluation to estimate the pump behavior during blowdown. There are two problems involved in analyzing this behavior. One problem concerns the pump characteristics under two-phase flow. The other involves the two-phase conditions at the pump inlet. If the rupture occurs at a suction side of the pump, choking is considered to occur at a broken jet pump nozzle. Then, a void fraction becomes larger downstream from the jet pump nozzle and volumetric flow through the pump will be very high. However, there is little experimental data available on two-phase flow downstream from a choking plane. Blowdown tests were performed using a simulated broken recirculation line and measured data were analyzed by TRAC-PlA. Analytical results agreed with measured data. (author)

  15. Flow Analysis of Space Shuttle Feed Line 17-inch Disconnect Valve

    Science.gov (United States)

    Kandula, Max; Pearce, Daniel

    1988-01-01

    A steady incompressible three-dimensional viscous flow analysis has been conducted for the Space Shuttle External Tank/Orbiter propellant feed line disconnect flapper valves with upstream elbows. The full Navier-Stokes code, INS3D, is modified to handle interior obstacles. Grids are generated by SVTGD3D code. Two dimensional initial grids in the flow cross section with and without the flappers are improved by elliptic smoothing to provide better orthogonality, clustering and smoothness to the three dimensional grid. The flow solver is tested for stability and convergence in the presence of interior flappers. An under-relaxation scheme has been incorporated to improve the solution stability. Important flow characteristics such as secondary flows, recirculation, vortex and wake regions, and separated flows are observed. Computed values for forces, moments, and pressure drop are in satisfactory agreement with water flow test data covering a maximum tube Reynolds number of 3.5 x 10(exp 6). The results will serve as a guide to improved design and enhanced testing of the disconnect.

  16. Dynamic Stability Enhancement and Power Flow Control of a Hybrid Wind and Marine-Current Farm Using SMES

    DEFF Research Database (Denmark)

    Wang, Li; Chen, Shiang-Shong; Lee, Wei-Jen

    2009-01-01

    be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective to stabilize the studied combined WF and MCF under various wind speeds. The inherent fluctuations of the injected active power and reactive power of the WF and MCF to the power......This paper presents a control scheme based on a superconducting magnetic energy storage (SMES) unit to achieve both power flow control and damping enhancement of a novel hybrid wind and marine-current farm (MCF) connected to a large power grid. The performance of the studied wind farm (WF...... under different operating conditions. A frequency-domain approach based on a linearized system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed control scheme. It can...

  17. Power flow control and damping enhancement of a large wind farm using a superconducting magnetic energy storage unit

    DEFF Research Database (Denmark)

    Chen, S. S.; Wang, L.; Lee, W. J.

    2009-01-01

    A novel scheme using a superconducting magnetic energy storage (SMES) unit to perform both power flow control and damping enhancement of a large wind farm (WF) feeding to a utility grid is presented. The studied WF consisting of forty 2 MW wind induction generators (IGs) is simulated...... by an equivalent 80 MW IG. A damping controller of the SMES unit is designed based on the modal control theory to contribute proper damping characteristics to the studied WF under different wind speeds. A frequency-domain approach based on a linearised system model using eigen techniques and a time-domain scheme...... based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed SMES unit with the designed SMES damping controller. It can be concluded from the simulated results that the proposed SMES unit combined with the designed damping...

  18. A study on rarefied gas flows through in-line arrangements of cylinders

    OpenAIRE

    田口, 智清; Satoshi, Taguchi; 神大・研究環; Kobe University

    2007-01-01

    Rarefied gas flows through in-line arrangements of cylinders are considered on the basis of the Boltzmann equation employing the BGK collision operator for the gas phase and the heat-conduction equation for the temperature inside the cylinders. Under the condition where the size of the periodic unit cell is much smaller than the characteristic length of the global structure, a diffusion model describing the mass and heat transfer through the medium is obtained by homogenization in the case wh...

  19. Local heat transfer in an in-line tube bundle with asymmetrical flow

    DEFF Research Database (Denmark)

    Meyer, Knud Erik

    1999-01-01

    Measurements of the local heat transfer in themiddle of a small in-line tube bundle with longitudinal to transverse pitches of $1.5\\times 1.8$ are performed at a Reynolds number of $30\\,000$. Asymmetrical distributions of the local heat transfer are found. The distributions are in good agreement...... with earlier flow measurements. The mean heat transfer rate is only little affected bythe asymmetrical conditions....

  20. Loss of feed flow, steam generator tube rupture and steam line break thermohydraulic experiments

    Energy Technology Data Exchange (ETDEWEB)

    Mendler, O J; Takeuchi, K; Young, M Y

    1986-10-01

    The Westinghouse Model Boiler No. 2 (MB-2) steam generator test model at the Engineering Test Facility in Tampa, Florida, was reinstrumented and modified for performing a series of tests simulating steam generator accident transients. The transients simulated were: loss of feed flow, steam generator tube rupture, and steam line break events. This document presents a description of (1) the model boiler and the associated test facility, (2) the tests performed, and (3) the analyses of the test results.

  1. Development and evaluation of a meter for measuring return line fluid flow rates during drilling

    Energy Technology Data Exchange (ETDEWEB)

    Loeppke, G.E.; Schafer, D.M.; Glowka, D.A.; Scott, D.D.; Wernig, M.D. (Sandia National Labs., Albuquerque, NM (United States)); Wright, E.K. (Ktech Corp., Albuquerque, NM (United States))

    1992-06-01

    The most costly problem routinely encountered in geothermal drilling is lost circulation, which occurs when drilling fluid is lost to the formation rather than circulating back to the surface. The successful and economical treatment of lost circulation requires the accurate measurement of drilling fluid flow rate both into and out of the well. This report documents the development of a meter for measuring drilling fluid outflow rates in the return line of a drilling rig. The meter employs a rolling counterbalanced float that rides on the surface of the fluid in the return line. The angle of the float pivot arm is sensed with a pendulum potentiometer, and the height of the float is calculated from this measurement. The float height is closely related to the fluid height and, therefore, the flow rate in the line. The prototype rolling float meter was extensively tested under laboratory conditions in the Wellbore Hydraulics Flow Facility; results from these tests were used in the design of the field prototype rolling float meter. The field prototype meter was tested under actual drilling conditions in August and September 1991 at the Long Valley Exploratory Well near Mammoth Lakes, Ca. In addition, the performance of several other commercially available inflow and outflow meters was evaluated in the field. The tested inflow meters included conventional pump stroke counters, rotary pump speed counters, magnetic flowmeters, and an ultrasonic Doppler flowmeter. On the return flow line, a standard paddlemeter, an acoustic level meter, and the prototype rolling float meter were evaluated for measuring drilling fluid outflow rates.

  2. Loss of feed flow, steam generator tube rupture and steam line break thermohydraulic experiments

    International Nuclear Information System (INIS)

    Mendler, O.J.; Takeuchi, K.; Young, M.Y.

    1986-10-01

    The Westinghouse Model Boiler No. 2 (MB-2) steam generator test model at the Engineering Test Facility in Tampa, Florida, was reinstrumented and modified for performing a series of tests simulating steam generator accident transients. The transients simulated were: loss of feed flow, steam generator tube rupture, and steam line break events. This document presents a description of (1) the model boiler and the associated test facility, (2) the tests performed, and (3) the analyses of the test results

  3. Wind tunnel study of the wind turbine interaction with a boundary-layer flow: Upwind region, turbine performance, and wake region

    Science.gov (United States)

    Bastankhah, M.; Porté-Agel, F.

    2017-06-01

    Comprehensive wind tunnel experiments were carried out to study the interaction of a turbulent boundary layer with a wind turbine operating under different tip-speed ratios and yaw angles. Force and power measurements were performed to characterize the variation of thrust force (both magnitude and direction) and generated power of the wind turbine under different operating conditions. Moreover, flow measurements, collected using high-resolution particle-image velocimetry as well as hot-wire anemometry, were employed to systematically study the flow in the upwind, near-wake, and far-wake regions. These measurements provide new insights into the effect of turbine operating conditions on flow characteristics in these regions. For the upwind region, the results show a strong lateral asymmetry under yawed conditions. For the near-wake region, the evolution of tip and root vortices was studied with the use of both instantaneous and phase-averaged vorticity fields. The results suggest that the vortex breakdown position cannot be determined based on phase-averaged statistics, particularly for tip vortices under turbulent inflow conditions. Moreover, the measurements in the near-wake region indicate a complex velocity distribution with a speed-up region in the wake center, especially for higher tip-speed ratios. In order to elucidate the meandering tendency of far wakes, particular focus was placed on studying the characteristics of large turbulent structures in the boundary layer and their interaction with wind turbines. Although these structures are elongated in the streamwise direction, their cross sections are found to have a size comparable to the rotor area, so that they can be affected by the presence of the turbine. In addition, the study of spatial coherence in turbine wakes reveals that any statistics based on streamwise velocity fluctuations cannot provide reliable information about the size of large turbulent structures in turbine wakes due to the effect of wake

  4. Simulation of Time-Varying Spatially Uniform Pressure and Near-Surface Wind Flows on Building Components and Cladding

    Directory of Open Access Journals (Sweden)

    Seraphy Y. Shen

    2017-05-01

    Full Text Available This paper describes a new full-scale (FS testing apparatus for conducting performance evaluations of FS building envelope systems. The simulator can generate spatially uniform, time-varying pressure conditions associated with Saffir–Simpson Hurricane Wind Scale Category 5 winds while compensating for large air leakage through the specimen and also operate a high-speed wind tunnel, both with dynamic control. This paper presents system details, operating characteristics, and an early case study on the performance of large sectional door systems under wind pressure loading. Failure mechanisms are discussed, and finite element modeling is validated for two specimens. It demonstrates successful dynamic load control for large component and cladding systems, as well as simulation of flows near the building surface. These capabilities serve to complement other FS wind tunnel facilities by offering tools to generate ultimate load conditions on portions of the building. Further, the paper successfully demonstrates the utility of combining physical testing and computational analysis as a matter of routine, which underscores the potential of evolving FS testing to encompass cyber–physical approaches.

  5. Turbulent penetration in T-junction branch lines with leakage flow

    Energy Technology Data Exchange (ETDEWEB)

    Kickhofel, John, E-mail: kickhofel@lke.mavt.ethz.ch; Valori, Valentina, E-mail: v.valori@tudelft.nl; Prasser, H.-M., E-mail: prasser@lke.mavt.ethz.ch

    2014-09-15

    Highlights: • New T-junction facility designed for adiabatic high velocity ratio mixing studies. • Trends in scalar mixing RMS and average in branch line presented and discussed. • Turbulent penetration has unique power spectrum relevant to thermal fatigue. • Forced flow oscillations translate to peaks in power spectrum in branch line. - Abstract: While the study of T-junction mixing with branch velocity ratios of near 1, so called cross flow mixing, is well advanced, to the point of realistic reactor environment fluid–structure interaction experiments and CFD benchmarking, turbulent penetration studies remain an under-researched threat to primary circuit piping. A new facility has been constructed for the express purpose of studying turbulent penetration in branch lines of T-junctions in the context of the high cycle thermal fatigue problem in NPPs. Turbulent penetration, which may be the result of a leaking valve in a branch line or an unisolable branch with heat losses, induces a thermal cycling region which may result in high cycle fatigue damage and failures. Leakage flow experiments have been performed in a perpendicular T-junction in a horizontal orientation with 50 mm diameter main pipe and branch pipe at velocity ratios (main/branch) up to 400. Wire mesh sensors are used as a means of measuring the mixing scalar in adiabatic tests with deionized and tap water. The near-wall region of highest scalar fluctuations is seen to vary circumferentially and in depth in the branch a great deal depending on the velocity ratio. The power spectra of the mixing scalar in the region of turbulent penetration are found to be dominated by high amplitude fluctuations at low frequencies, of particular interest to thermal fatigue. Artificial velocity oscillations in the main pipe manifest in the mixing spectra in the branch line in the form of a peak, the magnitude of which grows with increasing local RMS.

  6. Modeling particle emission and power flow in pulsed-power driven, nonuniform transmission lines

    Directory of Open Access Journals (Sweden)

    Nichelle Bruner

    2008-04-01

    Full Text Available Pulsed-power driven x-ray radiographic systems are being developed to operate at higher power in an effort to increase source brightness and penetration power. Essential to the design of these systems is a thorough understanding of electron power flow in the transmission line that couples the pulsed-power driver to the load. In this paper, analytic theory and fully relativistic particle-in-cell simulations are used to model power flow in several experimental transmission-line geometries fielded on Sandia National Laboratories’ upgraded Radiographic Integrated Test Stand [IEEE Trans. Plasma Sci. 28, 1653 (2000ITPSBD0093-381310.1109/27.901250]. Good agreement with measured electrical currents is demonstrated on a shot-by-shot basis for simulations which include detailed models accounting for space-charge-limited electron emission, surface heating, and stimulated particle emission. Resonant cavity modes related to the transmission-line impedance transitions are also shown to be excited by electron power flow. These modes can drive oscillations in the output power of the system, degrading radiographic resolution.

  7. The necessary distance between large wind farms offshore - study

    DEFF Research Database (Denmark)

    Frandsen, S.; Barthelmie, R.J.; Pryor, S.C.

    2005-01-01

    the new Storpark Analytical Model has been developed and evaluated. As it is often the need for offshore wind farms, the model handles a regular array-geometry with straight rows of wind turbines and equidistantspacing between units in each row and equidistant spacing between rows. Firstly, the case...... with the flow direction being parallel to rows in a rectangular geometry is considered by defining three flow regimes. Secondly, when the flow is not in line withthe main rows, solutions are found for the patterns of wind turbine units emerging corresponding to each wind direction. The model complex...

  8. Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

    DEFF Research Database (Denmark)

    Pedersen, Mads M.; Larsen, Torben J.; Madsen, Helge Aa

    2017-01-01

    with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting. Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall...... assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production...

  9. Power Flow Analysis of HVAC and HVDC Transmission Systems for Offshore WindParks

    DEFF Research Database (Denmark)

    da Silva, Filipe Miguel Faria; Castro, Rui

    2009-01-01

    As the onshore wind resource is running shorter, wind power promoters are paying attention to the offshore resources. As in most cases there is no load offshore, wind power must be transmitted to the main land. To do so, two options are available: HVAC and HVDC transmission systems. In this paper...... that HVAC solution is limited by the distance to shore and by the wind transmitted power. HVDC options do not show these limitations, but are more expensive and more delicate to deal with, because there is a lack of operational experience, so far....

  10. Dielectrophoresis microsystem with integrated flow cytometers for on-line monitoring of sorting efficiency

    DEFF Research Database (Denmark)

    Wang, Zhenyu; Hansen, Ole; Petersen, Peter Kalsen

    2006-01-01

    Dielectrophoresis (DEP) and flow cytometry are powerful technologies and widely applied in microfluidic systems for handling and measuring cells and particles. Here, we present a novel microchip with a DEP selective filter integrated with two microchip flow cytometers (FCs) for on-line monitoring...... of cell sorting processes. On the microchip, the DEP filter is integrated in a microfluidic channel network to sort yeast cells by positive DER The two FCs detection windows are set upstream and downstream of the DEP filter. When a cell passes through the detection windows, the light scattered by the cell...... is measured by integrated polymer optical elements (waveguide, lens, and fiber coupler). By comparing the cell counting rates measured by the two FCs, the collection efficiency of the DEP filter can be determined. The chips were used for quantitative determination of the effect of flow rate, applied voltage...

  11. The effect of water temperature and synoptic winds on the development of surface flows over narrow, elongated water bodies

    Science.gov (United States)

    Segal, M.; Pielke, R. A.

    1985-01-01

    Simulations of the thermally induced breeze involved with a relatively narrow, elongated water body is presented in conjunction with evaluations of sensible heat fluxes in a stable marine atmospheric surface layer. The effect of the water surface temperature and of the large-scale synoptic winds on the development of surface flows over the water is examined. As implied by the sensible heat flux patterns, the simulation results reveal the following trends: (1) when the synoptic flow is absent or light, the induced surface breeze is not affected noticeably by a reduction of the water surface temperature; and (2) for stronger synoptic flow, the resultant surface flow may be significantly affected by the water surface temperature.

  12. Impact of Wind Power Generation on European Cross-Border Power Flows

    DEFF Research Database (Denmark)

    Zugno, Marco; Pinson, Pierre; Madsen, Henrik

    2013-01-01

    A statistical analysis is performed in order to investigate the relationship between wind power production and cross-border power transmission in Europe. A dataset including physical hourly cross-border power exchanges between European countries as dependent variables is used. Principal component...... wind power production and spot price in Germany have substantial nonlinear effects on power transmission on a European scale....

  13. Evaluation of wind flow with a nacelle-mounted continuous-wave lidar

    DEFF Research Database (Denmark)

    Medley, John; Slinger, Chris; Barker, Will

    IR, increasing the confidence in the ZephIR for measuring wind parameters in this configuration. SCADA data from the turbine was combined with measured wind speeds and directions to derive power curves from the mast data (hub-height) and from ZephIR data (hub-height and rotor-equivalent). The rotor...

  14. Enhanced Kalman filtering for a 2D CFD NS wind farm flow model

    NARCIS (Netherlands)

    Doekemeijer, B.M.; van Wingerden, J.W.; Boersma, S.; Pao, L.Y

    2016-01-01

    Wind turbines are often grouped together for financial reasons, but due to wake development this usually results in decreased turbine lifetimes and power capture, and thereby an increased levelized cost of energy (LCOE). Wind farm control aims to minimize this cost by operating turbines at their

  15. Quasar emission lines as probes of orientation: implications for disc wind geometries and unification

    Science.gov (United States)

    Matthews, J. H.; Knigge, C.; Long, K. S.

    2017-05-01

    The incidence of broad absorption lines (BALs) in quasar samples is often interpreted in the context of a geometric unification model consisting of an accretion disc and an associated outflow. We use the Sloan Digital Sky Survey quasar sample to test this model by examining the equivalent widths (EWs) of C IV 1550 Å, Mg II 2800 Å, [O III] 5007 Å and C III] 1909 Å. We find that the emission line EW distributions in BAL and non-BAL quasars are remarkably similar - a property that is inconsistent with scenarios in which a BAL outflow rises equatorially from a geometrically thin, optically thick accretion disc. We construct simple models to predict the distributions from various geometries; these models confirm the above finding and disfavour equatorial geometries. We show that obscuration, line anisotropy and general relativistic effects on the disc continuum are unlikely to hide an EW inclination dependence. We carefully examine the radio and polarization properties of BAL quasars. Both suggest that they are most likely viewed (on average) from intermediate inclinations, between type 1 and type 2 active galactic nuclei (AGN). We also find that the low-ionization BAL quasars in our sample are not confined to one region of the 'Eigenvector 1' parameter space. Overall, our work leads to one of the following conclusions, or some combination thereof: (I) the continuum does not emit like a geometrically thin, optically thick disc; (II) BAL quasars are viewed from similar angles to non-BAL quasars, that is, low inclinations and (III) geometric unification does not explain the fraction of BALs in quasar samples.

  16. The impact of non-stationary flows on the surface stress in the weak-wind stable boundary layer

    Science.gov (United States)

    Thomas, Christoph; Mahrt, Larry

    2016-04-01

    The behaviour of turbulent transport in the weak-wind stably stratified boundary layer is examined in terms of the non-stationarity of the wind field based upon field observations. Extensive sonic anemometer measurements from horizontal networks and vertical towers ranging from 12 to 20 m height and innovative fiber-optic distributed temperature sensing observations were collected from three field programs in moderately sloped terrain with a varying degree of surface heterogeneity, namely the Shallow Cold Pool (SCP) and the Flow Over Snow Surfaces (FLOSS) II experiments in Colorado (USA), and the Advanced Canopy Resolution Experiment (ARCFLO) in Oregon (USA). The relationship of the friction velocity to the stratification and small non-stationary submeso motions is studied from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected due to the important submeso-scale motions. Consequently, the roles of the wind speed and stratification are not adequately accommodated by a single non-dimensional combination, such as the bulk Richardson number. However, cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases of downward transport of momentum. The latter may be significant in explaining the small-scale weak turbulence during stable stratification and deviations from conventional flux-profile relationships. Contrary to expectations, the vertical coherence was strongest for weakest winds and declined fast with increasing velocities, which suggests that submeso-scale motions are much deeper than previously thought.

  17. Wind-tunnel investigation of aerodynamic efficiency of three planar elliptical wings with curvature of quarter-chord line

    Science.gov (United States)

    Mineck, Raymond E.; Vijgen, Paul M. H. W.

    1993-01-01

    Three planar, untwisted wings with the same elliptical chord distribution but with different curvatures of the quarter-chord line were tested in the Langley 8-Foot Transonic Pressure Tunnel (8-ft TPT) and the Langley 7- by 10-Foot High-Speed Tunnel (7 x 10 HST). A fourth wing with a rectangular planform and the same projected area and span was also tested. Force and moment measurements from the 8-ft TPT tests are presented for Mach numbers from 0.3 to 0.5 and angles of attack from -4 degrees to 7 degrees. Sketches of the oil-flow patterns on the upper surfaces of the wings and some force and moment measurements from the 7 x 10 HST tests are presented at a Mach number of 0.5. Increasing the curvature of the quarter-chord line makes the angle of zero lift more negative but has little effect on the drag coefficient at zero lift. The changes in lift-curve slope and in the Oswald efficiency factor with the change in curvature of the quarter-chord line (wingtip location) indicate that the elliptical wing with the unswept quarter-chord line has the lowest lifting efficiency and the elliptical wing with the unswept trailing edge has the highest lifting efficiency; the crescent-shaped planform wing has an efficiency in between.

  18. Wind Tunnel Test of a Risk-Reduction Wing/Fuselage Model to Examine Juncture-Flow Phenomena

    Science.gov (United States)

    Kegerise, Michael A.; Neuhart, Dan H.

    2016-01-01

    A wing/fuselage wind-tunnel model was tested in the Langley 14- by 22-foot Subsonic Wind Tunnel in preparation for a highly-instrumented Juncture Flow Experiment to be conducted in the same facility. This test, which was sponsored by the NASA Transformational Tool and Technologies Project, is part of a comprehensive set of experimental and computational research activities to develop revolutionary, physics-based aeronautics analysis and design capability. The objectives of this particular test were to examine the surface and off-body flow on a generic wing/body combination to: 1) choose a final wing for a future, highly instrumented model, 2) use the results to facilitate unsteady pressure sensor placement on the model, 3) determine the area to be surveyed with an embedded laser-doppler velocimetry (LDV) system, 4) investigate the primary juncture corner- flow separation region using particle image velocimetry (PIV) to see if the particle seeding is adequately entrained and to examine the structure in the separated region, and 5) to determine the similarity of observed flow features with those predicted by computational fluid dynamics (CFD). This report documents the results of the above experiment that specifically address the first three goals. Multiple wing configurations were tested at a chord Reynolds number of 2.4 million. Flow patterns on the surface of the wings and in the region of the wing/fuselage juncture were examined using oil- flow visualization and infrared thermography. A limited number of unsteady pressure sensors on the fuselage around the wing leading and trailing edges were used to identify any dynamic effects of the horseshoe vortex on the flow field. The area of separated flow in the wing/fuselage juncture near the wing trailing edge was observed for all wing configurations at various angles of attack. All of the test objectives were met. The staff of the 14- by 22-foot Subsonic Wind Tunnel provided outstanding support and delivered

  19. Evaluation of the Trajectory Sensitivity Analysis of the DFIG Control Parameters in Response to Changes in Wind Speed and the Line Impedance Connection to the Grid DFIG

    Directory of Open Access Journals (Sweden)

    Mehdi Fooladgar

    2015-01-01

    Full Text Available Economic and environmental conditions often make large stations and transmission lines, restrictions are placed. Small and medium-sized production units connected to existing systems as a strategy is in progress. These units are usually near the center of the load placed and distributed generators (DG famous are the DG are allowed types vary, such as induction generators rack squirrel-connected wind turbines, generators fed induction double mounted wind turbines, fuel cells connected to the system by power electronic converters or synchronous generator connected to the turbine combustion [10]. This way sensitivity analysis in systems of distributed generation (DG is assessed. It is shown that the method can detect the effect of control parameters listed wind turbine connected to a double-fed induction generator (DFIG Badoou the impedance of the changing the speed of on the stability of the transmission line useful system invested. The control parameters of the importance of influencing the behavior of DFIG are divided.

  20. Flow-driven simulation on variation diameter of counter rotating wind turbines rotor

    Directory of Open Access Journals (Sweden)

    Littik Y. Fredrika

    2018-01-01

    Full Text Available Wind turbines model in this paper developed from horizontal axis wind turbine propeller with single rotor (HAWT. This research aims to investigating the influence of front rotor diameter variation (D1 with rear rotor (D2 to the angular velocity optimal (ω and tip speed ratio (TSR on counter rotating wind turbines (CRWT. The method used transient 3D simulation with computational fluid dynamics (CFD to perform the aerodynamics characteristic of rotor wind turbines. The counter rotating wind turbines (CRWT is designed with front rotor diameter of 0.23 m and rear rotor diameter of 0.40 m. In this research, the wind velocity is 4.2 m/s and variation ratio between front rotor and rear rotor (D1/D2 are 0.65; 0.80; 1.20; 1.40; and 1.60 with axial distance (Z/D2 0.20 m. The result of this research indicated that the variation diameter on front rotor influence the aerodynamics performance of counter rotating wind turbines.

  1. Bird strike and electrocutions at power lines, communication towers, and wind turbines: state of the art and state of the science - next steps toward mitigation

    Science.gov (United States)

    Albert M. Manville II

    2005-01-01

    Migratory birds suffer considerable human-caused mortality from structures built to provide public services and amenities. Three such entities are increasing nationwide: communication towers, power lines, and wind turbines. Communication towers have been growing at an exponential rate over at least the past 6 years. The U.S. Fish and Wildlife Service is especially...

  2. Active Power Flow Optimization of Industrial Power Supply with Regard to the Transmission Line Conductor Heating

    Directory of Open Access Journals (Sweden)

    Leyzgold D.Yu.

    2015-04-01

    Full Text Available This article studies the problem of the transmission line conductor heating effect on the active power flows optimization in the local segment of industrial power supply. The purpose is to determine the optimal generation rating of the distributed power sources, in which the power flow values will correspond to the minimum active power losses in the power supply. The timeliness is the need to define the most appropriate rated power values of distributed sources which will be connected to current industrial power supply. Basing on the model of active power flow optimization, authors formulate the description of the nonlinear transportation problem considering the active power losses depending on the transmission line conductor heating. Authors proposed a new approach to the heating model parameters definition based on allowable current loads and nominal parameters of conductors as part of the optimization problem. Analysis of study results showed that, despite the relatively small active power losses reduction to the tune 0,45% due to accounting of the conductors heating effect for the present configuration of power supply, there are significant fluctuations in the required generation rating in nodes of the network to 9,32% within seasonal changes in the outer air temperature. This fact should be taken into account when selecting the optimum power of distributed generation systems, as exemplified by an arbitrary network configuration.

  3. Air flow around suspended cables

    Directory of Open Access Journals (Sweden)

    Gołębiowska Irena

    2017-01-01

    Full Text Available The impact of wind on construction structures is essential issue in design and operation. In particular, the wind can cause the dengerous vibrations of slender structures with low rigidity, eg. vibrations of cables of suspension and cable-stayed bridges or high voltage transmision lines, thus understanding of wind flow around such constructions is significant. In the paper the results of the analysis of wind flow around the cables for different Reynolds number is presented. The analysed flow meets the Navier-Stokes and continuity equations. The circle and elipse section of the cable is analysed. The discusion of vorticity, drag and lift coefficients and cases due to different angle of wind flow action is presented. The boundary layer and its infuence on total flow is analysed.

  4. Calibration of a spinner anemometer for flow angle measurements by use of wind turbine yawing

    DEFF Research Database (Denmark)

    Demurtas, Giorgio; Friis Pedersen, Troels

    The present report describes a method to calibrate a spinner anemometer ow angle measurements. The turbine is yawed several times (5 times approximately 60 with respect to the wind direction) in steady wind (> 6 m/s) and measurements of yaw position (measured by a yaw position sensor) and yaw...... misalignment (measured by the spinner anemometer under calibration) are recorded. The tangent of the two angles is plotted in a scatter plot. A linear fitting is made, and the slope coefficient is the correction factor Fα. The method applied to a Nordtank 500kW wind turbine erected at the Risø test site...

  5. Investigation of the Unsteady Flow Behaviour on a Wind Turbine Using a BEM and a RANSE Method

    Directory of Open Access Journals (Sweden)

    Israa Alesbe

    2016-01-01

    Full Text Available Analyses of the unsteady flow behaviour of a 5 MW horizontal-axis wind turbine (HAWT rotor (Case I and a rotor with tower (Case II are carried out using a panel method and a RANSE method. The panel method calculations are obtained by applying the in-house boundary element method (BEM panMARE code, which is based on the potential flow theory. The BEM is a three-dimensional first-order panel method which can be used for investigating various steady and unsteady flow problems. Viscous flow simulations are carried out by using the RANSE solver ANSYS CFX 14.5. The results of Case I allow for the calculation of the global integral values of the torque and the thrust and include detailed information on the local flow field, such as the pressure distribution on the blade sections and the streamlines. The calculated pressure distribution by the BEM is compared with the corresponding values obtained by the RANSE solver. The tower geometry is considered in the simulation in Case II, so the unsteady forces due to the interaction between the tower and the rotor blades can be calculated. The application of viscous and inviscid flow methods to predict the forces on the HAWT allows for the evaluation of the viscous effects on the calculated HAWT flows.

  6. Study of turbine and guide vanes integration to enhance the performance of cross flow vertical axis wind turbine

    Science.gov (United States)

    Wibowo, Andreas; Tjahjana, Dominicus Danardono Dwi Prija; Santoso, Budi; Situmorang, Marcelinus Risky Clinton

    2018-02-01

    The main purpose of this study is to investigate the best configuration between guide vanes and cross flow vertical axis wind turbine with variation of several parameters including guide vanes tilt angle and the number of turbine and guide vane blades. The experimental test were conducted under various wind speed and directions for testing cross flow wind turbine, consisted of 8, 12 and 16 blades. Two types of guide vane were developed in this study, employing 20° and 60° tilt angle. Both of the two types of guide vane had three variations of blade numbers which had same blade numbers variations as the turbines. The result showed that the configurations between 60° guide vane with 16 blade numbers and turbine with 16 blade numbers had the best configurations. The result also showed that for certain configuration, guide vane was able to increase the power generated by the turbine significantly by 271.39% compared to the baseline configuration without using of guide vane.

  7. Vegetation in drylands: Effects on wind flow and aeolian sediment transport

    Science.gov (United States)

    Drylands are characterised by patchy vegetation, erodible surfaces and erosive aeolian processes. Empirical and modelling studies have shown that vegetation elements provide drag on the overlying airflow, thus affecting wind velocity profiles and altering erosive dynamics on desert surfaces. However...

  8. Aerodynamic flow deflector to increase large scale wind turbine power generation by 10%.

    Science.gov (United States)

    2015-11-01

    The innovation proposed in this paper has the potential to address both the efficiency demands of wind farm owners as well as to provide a disruptive design innovation to turbine manufacturers. The aerodynamic deflector technology was created to impr...

  9. Intermittent heating of the corona as an alternative to generate fast solar wind flows

    International Nuclear Information System (INIS)

    Grappin, R.; Mangeney, A.; Schwartz, S.J.; Feldman, W.C.

    1999-01-01

    We discuss a new alternative to the generation of fast streams which does not require momentum addition beyond the critical point. We consider the consequences on the solar wind of temporally intermittent heat depositions at the base of the wind. With the help of 1d hydrodynamic simulations we show that the instantaneous wind velocity profile fluctuates around an average profile well above the one corresponding to the Parker solution with a coronal temperature equal to the average coronal temperature imposed at the bottom of the numerical domain. The origin of this result lies in a previously overlooked phenomenon, the overexpansion of hot plasma regions in the subsonic wind. copyright 1999 American Institute of Physics

  10. Testing Accretion Disk Wind Models of Broad Absorption Line Quasars with SDSS Spectra

    Science.gov (United States)

    Lindgren, Sean; Gabel, Jack

    2017-06-01

    We present an investigation of a large sample of broad absorption line (BAL) quasars (QSO) from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Properties of the BALs, such as absorption equivalent width, outflow velocities, and depth of BAL, are obtained from analysis by Gibson et al. We perform correlation analysis on these data to test the predictions made by the radiation driven, accretion disk streamline model of Murray and Chiang. We find the CIV BAL maximum velocity and the continuum luminosity are correlated, consistent with radiation driven models. The mean minimum velocity of CIV is lower in low ionization BALs (LoBALs), than highly ionized BALs (HiBALS), suggesting an orientation effect consistent with the Murray and Chiang model. Finally, we find that HiBALs greatly outnumber LoBALs in the general BAL population, supporting prediction of the Murray and Chiang model that HiBALs have a greater global covering factor than LoBALs.

  11. A prototype of on-line digital flow rate meter based on cross-correlation principle

    International Nuclear Information System (INIS)

    Sun Xiaodong; Dai Zhenxi; Xu Jijun

    1997-01-01

    An on-line, digital prototype of flow rate measurement system based on cross-correlation principle is developed. Laboratory measurements using the prototype show that sufficiently large temperature fluctuations exist naturally and that measurements are possible. Temperature fluctuations are detected by two identical thermocouples spaced along the flow direction and are pre-processed by a thermocouple signal amplifier. The pre-processed temperature fluctuations are analyzed by a cross-correlator which measures the transit time of temperature fluctuations between two thermocouples directly. Thus, the so-called correlation velocity can be determined by a chip microprocessor 8031. Experimental results with single-phase under steady conditions also show that the distance between two thermocouples and the Reynolds number of fluid are the most important parameters to the measurement

  12. Electrostatic potential in a collisionless plasma flow along open magnetic field lines

    International Nuclear Information System (INIS)

    Sato, Kunihiro; Katayama, Hideaki; Miyawaki, Fujio

    1992-06-01

    Formation of the steady-state potential in a collisionless plasma flow along nonuniform magnetic field lines terminated at a wall is studied theoretically under the condition that a particle source in a plasma can be neglected. It is found that the plasma flow is required to satisfy the generalized Bohm criterion over the whole region for the formation of the steady-state continuous potential in the divergent magnetic field. A monotonically falling potential can build up from the inside of the magnetic throat to the wall only if the Bohm criterion is marginally satisfied at the throat. Numerical solutions to Poisson's equation show that a potential profile outside the throat is strongly dependent upon the particle density of electrons trapped between the throat and the wall. Controllability of the potential by increasing the trapped-electron density is discussed briefly. (author)

  13. On-line automatic detection of wood pellets in pneumatically conveyed wood dust flow

    Science.gov (United States)

    Sun, Duo; Yan, Yong; Carter, Robert M.; Gao, Lingjun; Qian, Xiangchen; Lu, Gang

    2014-04-01

    This paper presents a piezoelectric transducer based system for on-line automatic detection of wood pellets in wood dust flow in pneumatic conveying pipelines. The piezoelectric transducer senses non-intrusively the collisions between wood pellets and the pipe wall. Wavelet-based denoising is adopted to eliminate environmental noise and recover the collision events. Then the wood pellets are identified by sliding a time window through the denoised signal with a suitable threshold. Experiments were carried out on a laboratory test rig and on an industrial pneumatic conveying pipeline to assess the effectiveness and operability of the system.

  14. Propagation of the initial value perturbation in a cylindrical lined duct carrying a gas flow

    Directory of Open Access Journals (Sweden)

    Agneta M. BALINT

    2013-03-01

    Full Text Available For the homogeneous Euler equation linearized around a non-slipping mean flow andboundary conditions corresponding to the mass-spring-damper impedance, smooth initial dataperturbations with compact support are considered. The propagation of this type of initial dataperturbations in a straight cylindrical lined duct is investigated. Such kind of investigations is missingin the existing literature. The mathematical tools are the Fourier transform with respect to the axialspatial variable and the Laplace transform with respect to the time variable. The functionalframework and sufficient conditions are researched that the so problem be well-posed in the sense ofHadamard and the Briggs-Bers stability criteria can be applied.

  15. Optimal surface segmentation using flow lines to quantify airway abnormalities in chronic obstructive pulmonary disease

    DEFF Research Database (Denmark)

    Petersen, Jens; Nielsen, Mads; Lo, Pechin Chien Pau

    2014-01-01

    are not well suited for surfaces with high curvature, we therefore propose to derive columns from properly generated, non-intersecting flow lines. This guarantees solutions that do not self-intersect. The method is applied to segment human airway walls in computed tomography images in three-dimensions. Phantom.......5%, the alternative approach in 11.2%, and in 20.3% no method was favoured. Airway abnormality measurements obtained with the method on 490 scan pairs from a lung cancer screening trial correlate significantly with lung function and are reproducible; repeat scan R(2) of measures of the airway lumen diameter and wall...

  16. A study on the possibility of cooling of schools by natural wind flow

    Energy Technology Data Exchange (ETDEWEB)

    Setodemaram, K. [West Azarbayjan Management Power Generation Co. (Iran, Islamic Republic of); Golneshan, A.A.; Jafarpur, Kh. [Shiraz Univ. (Iran, Islamic Republic of). Dept. of Mechanical Engineering

    2005-07-01

    Wind towers have been used for natural ventilation and passive cooling of buildings in traditional architecture in hot regions of Iran and neighbouring countries.This paper discussed the feasibility of using modern wind towers to cool air in schools. The value of the convective heat transfer coefficient in classrooms was determined. A 1:35 scale plexiglass model of a typical 8 class-room school was created. A series of experiments were conducted in a wind tunnel. Mass transfer analogy using naphthalene sublimation was employed to measure the convective heat transfer coefficient in the model. The plexiglass model was equipped with a wind tower in order to study the movement of air in the classrooms. The convective heat transfer coefficient was determined. The effect of students as well as night ventilation on temperature variations in the classrooms was studied through computerized simulation. The ambient temperature and pressure and naphthalene sublimated mass rate were evaluated. The exhausted wind tunnel air temperature between the mouth of the tower and windows in each class were measured in each of the tests. Air velocity in classrooms was determined using Reynolds number and air change per hour. A typical hot summer day in Shiraz was selected for a case study. It was concluded that the proposed design was suitable for hot and dry regions, and that a wind tower could significantly reduce the cooling load of the buildings. 9 refs., 10 figs.

  17. Touch at a distance sensing: lateral-line inspired MEMS flow sensors

    International Nuclear Information System (INIS)

    Prakash Kottapalli, Ajay Giri; Asadnia, Mohsen; Miao, Jianmin; Triantafyllou, Michael

    2014-01-01

    Evolution bestowed the blind cavefish with a resourcefully designed lateral-line of sensors that play an essential role in many important tasks including object detection and avoidance, energy-efficient maneuvering, rheotaxis etc. Biologists identified the two types of vital sensors on the fish bodies called the superficial neuromasts and the canal neuromasts that are responsible for flow sensing and pressure-gradient sensing, respectively. In this work, we present the design, fabrication and experimental characterization of biomimetic polymer artificial superficial neuromast micro-sensor arrays. These biomimetic micro-sensors demonstrated a high sensitivity of 0.9 mV/(m s −1 ) and 0.022 V/(m s −1 ) and threshold velocity detection limits of 0.1 m s −1 and 0.015 m s −1 in determining air and water flows respectively. Experimental results demonstrate that the biological canal inspired polymer encapsulation on the array of artificial superficial neuromast sensors is capable of filtering steady-state flows that could otherwise significantly mask the relevant oscillatory flow signals of high importance. (paper)

  18. Adjoint Method and Predictive Control for 1-D Flow in NASA Ames 11-Foot Transonic Wind Tunnel

    Science.gov (United States)

    Nguyen, Nhan; Ardema, Mark

    2006-01-01

    This paper describes a modeling method and a new optimal control approach to investigate a Mach number control problem for the NASA Ames 11-Foot Transonic Wind Tunnel. The flow in the wind tunnel is modeled by the 1-D unsteady Euler equations whose boundary conditions prescribe a controlling action by a compressor. The boundary control inputs to the compressor are in turn controlled by a drive motor system and an inlet guide vane system whose dynamics are modeled by ordinary differential equations. The resulting Euler equations are thus coupled to the ordinary differential equations via the boundary conditions. Optimality conditions are established by an adjoint method and are used to develop a model predictive linear-quadratic optimal control for regulating the Mach number due to a test model disturbance during a continuous pitch

  19. Optimal Power Flow Modelling and Analysis of Hybrid AC-DC Grids with Offshore Wind Power Plant

    DEFF Research Database (Denmark)

    Dhua, Debasish; Huang, Shaojun; Wu, Qiuwei

    2017-01-01

    , it is essential to develop a suitable model and apply optimization algorithms for different application scenarios. The objective of this work is to develop a generalized model and evaluate the Optimal Power Flow (OPF) solutions in a hybrid AC/DC system including HVDC (LCC based) and offshore WPP (VSC based......In order to develop renewables based energy systems, the installation of the offshore wind power plants (WPPs) is globally encouraged. However, wind power generation is intermittent and uncertain. An accurate modelling and evaluation reduces investment and provide better operation. Hence......). This paper also shows the significance and impact of control parameters in OPF applications. An integrated hybrid power system network is adopted in this paper and OPF techniques are applied on it by considering the impact of different control parameters. In addition to the impact of the control variables...

  20. Method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O2 fluorescence

    Science.gov (United States)

    Laufer, Gabriel; Mckenzie, Robert L.; Fletcher, Douglas G.

    1990-01-01

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations owing to turbulence can be measured in air flows associated with high-speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainties in the temperature and density measurements can be less than 2 percent, if the signal uncertainties are dominated by photon statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  1. A method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O2 fluorescence

    Science.gov (United States)

    Laufer, Gabriel; Fletcher, Douglas G.; Mckenzie, Robert L.

    1990-01-01

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations due to turbulence can be measured in air flows associated with high-speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainty in the temperature and density measurements can be less than 2 and 3 percent, respectively, if the signal uncertainties are dominated by photon-statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  2. The role of wind field induced flow velocities in destratification and hypoxia reduction at Meiling Bay of large shallow Lake Taihu, China.

    Science.gov (United States)

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Wencai; Wang, Jianwei; Gao, Xiaomeng; Khan, Hafiz Osama Sarwar; Pan, Baozhu; Acharya, Kumud

    2018-01-01

    Wind induced flow velocity patterns and associated thermal destratification can drive to hypoxia reduction in large shallow lakes. The effects of wind induced hydrodynamic changes on destratification and hypoxia reduction were investigated at the Meiling bay (N 31° 22' 56.4″, E 120° 9' 38.3″) of Lake Taihu, China. Vertical flow velocity profile analysis showed surface flow velocities consistency with the wind field and lower flow velocity profiles were also consistent (but with delay response time) when the wind speed was higher than 6.2 m/s. Wind field and temperature found the control parameters for hypoxia reduction and for water quality conditions at the surface and bottom profiles of lake. The critical temperature for hypoxia reduction at the surface and the bottom profile was ≤24.1C° (below which hypoxic conditions were found reduced). Strong prevailing wind field (onshore wind directions ESE, SE, SSE and E, wind speed ranges of 2.4-9.1 m/s) reduced the temperature (22C° to 24.1C°) caused reduction of hypoxia at the near surface with a rise in water levels whereas, low to medium prevailing wind field did not supported destratification which increased temperature resulting in increased hypoxia. Non-prevailing wind directions (offshore) were not found supportive for the reduction of hypoxia in study area due to less variable wind field. Daytime wind field found more variable (as compared to night time) which increased the thermal destratification during daytime and found supportive for destratification and hypoxia reduction. The second order exponential correlation found between surface temperature and Chlorophyll-a (R 2 : 0.2858, Adjusted R-square: 0.2144 RMSE: 4.395), Dissolved Oxygen (R 2 : 0.596, Adjusted R-square: 0.5942, RMSE: 0.3042) concentrations. The findings of the present study reveal the driving mechanism of wind induced thermal destratification and hypoxic conditions, which may further help to evaluate the wind role in eutrophication

  3. Man-made flows from a fish's perspective: autonomous classification of turbulent fishway flows with field data collected using an artificial lateral line.

    Science.gov (United States)

    Tuhtan, Jeffrey Andrew; Fuentes-Perez, Juan Francisco; Toming, Gert; Schneider, Matthias; Schwarzenberger, Richard; Schletterer, Martin; Kruusmaa, Maarja

    2018-04-09

    The lateral line system provides fish with advanced mechanoreception over a wide range of flow conditions. Inspired by the abilities of their biological counterparts, artificial lateral lines have been developed and tested exclusively under laboratory settings. Motivated by the lack of flow measurements taken in the field which consider fluid-body interactions, we built a fish-shaped lateral line probe. The device is outfitted with 11 high-speed (2.5 kHz) time-synchronized pressure transducers, and designed to capture and classify flows in fish passage structures. A total of 252 field measurements, each with a sample size of 132,000 discrete sensor readings were recorded in the slots and across the pools of vertical slot fishways. These data were used to estimate the time-averaged flow velocity (R² = 0.952), which represents the most common metric to assess fishway flows. The significant contribution of this work is the creation and application of hydrodynamic signatures generated by the spatial distribution of pressure fluctuations on the fish-shaped body. The signatures are based on the collection of the pressure fluctuations' probability distributions, and it is shown that they can be used to automatically classify distinct flow regions within the pools of three different vertical slot fishways. For the first time, field data from operational fishway measurements are sampled and classified using an artificial lateral line, providing a completely new source of bioinspired flow information. © 2018 IOP Publishing Ltd.

  4. Wind tunnel experimental study on effect of inland nuclear power plant cooling tower on air flow and dispersion of pollutant

    International Nuclear Information System (INIS)

    Qiao Qingdang; Yao Rentai; Guo Zhanjie; Wang Ruiying; Fan Dan; Guo Dongping; Hou Xiaofei; Wen Yunchao

    2011-01-01

    A wind tunnel experiment for the effect of the cooling tower at Taohuajiang nuclear power plant on air flow and dispersion of pollutant was introduced in paper. Measurements of air mean flow and turbulence structure in different directions of cooling tower and other buildings were made by using an X-array hot wire probe. The effects of the cooling tower and its drift on dispersion of pollutant from the stack were investigated through tracer experiments. The results show that the effect of cooling tower on flow and dispersion obviously depends on the relative position of stack to cooling towers, especially significant for the cooling tower parallel to stack along wind direction. The variation law of normalized maximum velocity deficit and perturbations in longitudinal turbulent intensity in cooling tower wake was highly in accordance with the result of isolated mountain measured by Arya and Gadiyaram. Dispersion of pollutant in near field is significantly enhanced and plume trajectory is changed due to the cooling towers and its drift. Meanwhile, the effect of cooling tower on dispersion of pollutant depends on the height of release. (authors)

  5. The profiles of Fe K α line from the inhomogeneous accretion flow

    Science.gov (United States)

    Yu, Xiao-Di; Ma, Ren-Yi; Li, Ya-Ping; Zhang, Hui; Fang, Tao-Tao

    2018-05-01

    The clumpy disc, or inhomogeneous accretion flow, has been proposed to explain the properties of accreting black hole systems. However, the observational evidence remains to be explored. In this work, we calculate the profiles of Fe K α lines emitted from the inhomogeneous accretion flow through the ray-tracing technique, in order to find possible observable signals of the clumps. Compared with the skewed double-peaked profile of the continuous standard accretion disc, the lines show a multipeak structure when the emissivity index is not very steep. The peaks and wings are affected by the position and size of the cold clumps. When the clump is small and is located in the innermost region, due to the significant gravitational redshift, the blue wing can overlap with the red wing of the outer cold disc/clump, forming a fake peak or greatly enhancing the red peak. Given high enough resolution, it is easier to constrain the clumps around the supermassive black holes than the clumps in stellar mass black holes due to the thermal Doppler effect.

  6. The Profiles of Fe Kα Line From the Inhomogeneous Accretion Flow

    Science.gov (United States)

    Yu, Xiao-Di; Ma, Ren-Yi; Li, Ya-Ping; Zhang, Hui; Fang, Tao-Tao

    2018-02-01

    The clumpy disc, or inhomogeneous accretion flow, has been proposed to explain the properties of accreting black hole systems. However, the observational evidences remain to be explored. In this work, we calculate the profiles of Fe Kα lines emitted from the inhomogeneous accretion flow through the ray-tracing technique, in order to find possible observable signals of the clumps. Compared with the skewed double-peaked profile of the continuous standard accretion disc, the lines show a multi-peak structure when the emissivity index is not very steep. The peaks and wings are affected by the position and size of the cold clumps. When the clump is small and is located in the innermost region, due to the significant gravitational redshift, the blue wing can overlap with the red wing of the outer cold disc/clump, forming a fake peak or greatly enhancing the red peak. Given high enough resolution, it is easier to constrain the clumps around the supermassive black holes than the clumps in stellar mass black holes due to the thermal Doppler effect.

  7. Air Flow Modeling in the Wind Tunnel of the FHWA Aerodynamics Laboratory at Turner-Fairbank Highway Research Center

    Energy Technology Data Exchange (ETDEWEB)

    Sitek, M. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Transportation Research and Analysis Computing Center (TRACC) Energy Systems Division; Lottes, S. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Transportation Research and Analysis Computing Center (TRACC) Energy Systems Division; Bojanowski, C. [Argonne National Lab. (ANL), Argonne, IL (United States). Transportation Research and Analysis Computing Center (TRACC) Energy Systems Division

    2017-09-01

    geometry and CFD model of the wind tunnel laboratory at TFHRC was built and tested. Results were compared against experimental wind velocity measurements at a large number of locations around the room. This testing included an assessment of the air flow uniformity provided by the tunnel to the test zone and assessment of room geometry effects, such as influence of the proximity the room walls, the non-symmetrical position of the tunnel in the room, and the influence of the room setup on the air flow in the room. This information is useful both for simplifying the computational model and in deciding whether or not moving, or removing, some of the furniture or other movable objects in the room will change the flow in the test zone.

  8. Study of process parameters effect on the filling phase of micro injection moulding using weld lines as flow markers

    DEFF Research Database (Denmark)

    Tosello, Guido; Gava, Alberto; Hansen, Hans Nørgaard

    2010-01-01

    , the relationships between the filling pattern and the different process parameter settings have to be established. In this paper, a novel approach based on the use of weld lines as flow markers to trace the development of the flow front during the filling is proposed. The effects on the filling stage of process...

  9. Aero-acoustic Computations of Wind Turbines

    DEFF Research Database (Denmark)

    Shen, Wen Zhong; Michelsen, Jess; Sørensen, Jens Nørkær

    2002-01-01

    A numerical algorithm for acoustic noise generation is extended to 3D flows. The approach involves two parts comprising a viscous incompressible flow part and an inviscid acoustic part. In order to simulate noise generated from a wind turbine, the incompressible and acoustic equations are written...... in polar coordinates. The developed algorithm is combined with a so-called actuator-line technique in which the loading is distributed along lines representing the blade forces. Computations are carried out for the 500kW Nordtank wind turbine equipped with three LM19 blades. ©2001 The American Institute...

  10. Blowing jets as a circulation flow control to enhancement the lift of wing or generated power of wind turbine

    Directory of Open Access Journals (Sweden)

    Alexandru DUMITRACHE

    2014-06-01

    Full Text Available The goal of this paper is to provide a numerical flow analysis based on RANS equations in two directions: the study of augmented high-lift system for a cross-section airfoil of a wing up to transonic regime and the circulation control implemented by tangentially blowing jet over a highly curved surface due to Coanda effect on a rotor blade for a wind turbine. This study were analyzed the performance, sensitivities and limitations of the circulation control method based on blowing jet for a fixed wing as well as for a rotating wing. Directions of future research are identified and discussed.

  11. Flow visualization techniques, new developments and modernization of the existing Schlieren system in the Trisonic Wind Tunnel

    Directory of Open Access Journals (Sweden)

    Marius PANAIT

    2011-06-01

    Full Text Available Schlieren flow visualization methods are an important part of high speed wind tunnel testing, being a fast and reliable method of graphically presenting complex dynamic phenomena that occur in high subsonic, transonic and supersonic regimes. Images can be processed and effects of configuration changes can be understood faster. Quantitative variations of the Schlieren method enable CFD simulations to use real data, resulting in greater precision and thus help improve efficiency of the re-design phase for the aerodynamic object. A modification of the classic Schlieren system is proposed, that would enable extraction of such data with minimal costs

  12. Experimental Vision Studies of Flow and Structural Effects on Wind Turbines

    DEFF Research Database (Denmark)

    Najafi, Nadia

    In the present thesis, two modern vision technologies are developed and used to study wind turbines: 1- Stereo vision to study vibrations and dynamics of the Vertical Axes Wind Turbine (VAWT) via operational modal analysis (OMA) 2- Background-oriented Schlieren (BOS) method to study the tip...... measurement sets in OMA. Therefore, the first four natural frequencies are identified and agreed fairly with classical modal analysis (EMA) and finite element simulation (FEM). The second experiment is conducted on a VAWT rotor in the wind tunnel in a more controlled and designed condition...... obtained with OMA are validated with the simulation and EMA, and then, the differences are explained with the aerodynamic effect and boundary conditions. The other frequencies obtained by OMA are interpreted via vortex shedding phenomena and guy wire effects. In the fifth chapter, the uncertainty...

  13. Pore-scale modeling of moving contact line problems in immiscible two-phase flow.

    Science.gov (United States)

    Kucala, A.; Noble, D.; Martinez, M. J.

    2016-12-01

    Two immiscible fluids in static equilibrium form a common interface along a solid surface, characterized as the static contact (wetting) angle and is a function of surface geometry, intermolecular forces, and interfacial surface energies manifested as interfacial tension. This static configuration may become perturbed due to external force imbalances (mass injection, pressure gradients, buoyancy, etc.) and the contact line location and interface curvature becomes dynamic. Accurate modeling of moving contact line (MCL) problems is imperative in predicting capillary pressure vs. saturation curves, permeability, and preferential flow paths for a variety of applications, including geological carbon storage (GCS) and enhanced oil recovery (EOR). Here, we present a model for the moving contact line using pore-scale computational fluid dynamics (CFD) which solves the full, time-dependent Navier-Stokes equations using the Galerkin finite-element method. The MCL is modeled as a surface traction force proportional to the surface tension, dependent on the static properties of the immiscible fluid/solid system. The moving two-phase interface is tracked using the level set method and discretized with the conformal decomposition finite element method (CDFEM), allowing for surface tension effects to be computed at the exact interface location. We present a variety of verification test cases for simple two- and three-dimensional geometries to validate the current model, including threshold pressure predictions in flows through pore-throats for a variety of wetting angles. Simulations involving more complex geometries are also presented to be used in future simulations for GCS and EOR problems. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000

  14. Simulation of ideal-gas flow by nitrogen and other selected gases at cryogenic temperatures. [transonic flow in cryogenic wind tunnels

    Science.gov (United States)

    Hall, R. M.; Adcock, J. B.

    1981-01-01

    The real gas behavior of nitrogen, the gas normally used in transonic cryogenic tunnels, is reported for the following flow processes: isentropic expansion, normal shocks, boundary layers, and interactions between shock waves and boundary layers. The only difference in predicted pressure ratio between nitrogen and an ideal gas which may limit the minimum operating temperature of transonic cryogenic wind tunnels occur at total pressures approaching 9 atm and total temperatures 10 K below the corresponding saturation temperature. These pressure differences approach 1 percent for both isentropic expansions and normal shocks. Alternative cryogenic test gases were also analyzed. Differences between air and an ideal diatomic gas are similar in magnitude to those for nitrogen and should present no difficulty. However, differences for helium and hydrogen are over an order of magnitude greater than those for nitrogen or air. It is concluded that helium and cryogenic hydrogen would not approximate the compressible flow of an ideal diatomic gas.

  15. A finite-element model for moving contact line problems in immiscible two-phase flow

    Science.gov (United States)

    Kucala, Alec

    2017-11-01

    Accurate modeling of moving contact line (MCL) problems is imperative in predicting capillary pressure vs. saturation curves, permeability, and preferential flow paths for a variety of applications, including geological carbon storage (GCS) and enhanced oil recovery (EOR). The macroscale movement of the contact line is dependent on the molecular interactions occurring at the three-phase interface, however most MCL problems require resolution at the meso- and macro-scale. A phenomenological model must be developed to account for the microscale interactions, as resolving both the macro- and micro-scale would render most problems computationally intractable. Here, a model for the moving contact line is presented as a weak forcing term in the Navier-Stokes equation and applied directly at the location of the three-phase interface point. The moving interface is tracked with the level set method and discretized using the conformal decomposition finite element method (CDFEM), allowing for the surface tension and the wetting model to be computed at the exact interface location. A variety of verification test cases for simple two- and three-dimensional geometries are presented to validate the current MCL model, which can exhibit grid independence when a proper scaling for the slip length is chosen. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

  16. Numerical Analysis of Thermal Mixing in a Swirler-Embedded Line-Heater for Flow Assurance in Subsea Pipelines

    Directory of Open Access Journals (Sweden)

    Jang Min Park

    2015-02-01

    Full Text Available Flow assurance issue in subsea pipelines arises mainly due to hydrate plugs. We present a new line-heater for prevention of hydrate plug formation in subsea pipelines. The line heater has modular compact design where an electrical heater and a swirl generator are embedded inside the housing pipe so that the stream can be heated efficiently and homogeneously. In this paper, flow and heat transfer characteristics of the line heater are investigated numerically, with a particular emphasis on the mixing effect due to the swirl generator.

  17. Wake characteristics of wind turbines in utility-scale wind farms

    Science.gov (United States)

    Yang, Xiaolei; Foti, Daniel; Sotiropoulos, Fotis

    2017-11-01

    The dynamics of turbine wakes is affected by turbine operating conditions, ambient atmospheric turbulent flows, and wakes from upwind turbines. Investigations of the wake from a single turbine have been extensively carried out in the literature. Studies on the wake dynamics in utility-scale wind farms are relatively limited. In this work, we employ large-eddy simulation with an actuator surface or actuator line model for turbine blades to investigate the wake dynamics in utility-scale wind farms. Simulations of three wind farms, i.e., the Horns Rev wind farm in Denmark, Pleasant Valley wind farm in Minnesota, and the Vantage wind farm in Washington are carried out. The computed power shows a good agreement with measurements. Analysis of the wake dynamics in the three wind farms is underway and will be presented in the conference. This work was support by Xcel Energy (RD4-13). The computational resources were provided by National Renewable Energy Laboratory.

  18. Wind field re-construction of 3D Wake measurements from a turbine-installed scanning lidar

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Herges, Tommy; Astrup, Poul

    High-resolution wake flow measurements obtained from a turbine-mounted scanning lidar have been obtained from 1D to 5D behind a V27 test turbine. The measured line-of-sight projected wind speeds have, in connection with a fast CFD wind field reconstruction model, been used to generate 3D wind fie...

  19. Wind Tunnel Model Design for Sonic Boom Studies of Nozzle Jet Flows with Shock Interactions

    Science.gov (United States)

    Cliff, Susan E.; Denison, Marie; Moini-Yekta, Shayan; Morr, Donald E.; Durston, Donald A.

    2016-01-01

    NASA and the U.S. aerospace industry are performing studies of supersonic aircraft concepts with low sonic boom pressure signatures. The computational analyses of modern aircraft designs have matured to the point where there is confidence in the prediction of the pressure signature from the front of the vehicle, but uncertainty remains in the aft signatures due to boundary layer and nozzle exhaust jet effects. Wind tunnel testing without inlet and nozzle exhaust jet effects at lower Reynolds numbers than in-flight make it difficult to accurately assess the computational solutions of flight vehicles. A wind tunnel test in the NASA Ames 9- by 7-Foot Supersonic Wind Tunnel is planned for February 2016 to address the nozzle jet effects on sonic boom. The experiment will provide pressure signatures of test articles that replicate waveforms from aircraft wings, tails, and aft fuselage (deck) components after passing through cold nozzle jet plumes. The data will provide a variety of nozzle plume and shock interactions for comparison with computational results. A large number of high-fidelity numerical simulations of a variety of shock generators were evaluated to define a reduced collection of suitable test models. The computational results of the candidate wind tunnel test models as they evolved are summarized, and pre-test computations of the final designs are provided.

  20. Three-dimensional flow field around and downstream of a subscale model rotating vertical axis wind turbine

    Science.gov (United States)

    Ryan, Kevin J.; Coletti, Filippo; Elkins, Christopher J.; Dabiri, John O.; Eaton, John K.

    2016-03-01

    Three-dimensional, three-component mean velocity fields have been measured around and downstream of a scale model vertical axis wind turbine (VAWT) operated at tip speed ratios (TSRs) of 1.25 and 2.5, in addition to a non-rotating case. The five-bladed turbine model has an aspect ratio (height/diameter) of 1 and is operated in a water tunnel at a Reynolds number based on turbine diameter of 11,600. Velocity fields are acquired using magnetic resonance velocimetry (MRV) at an isotropic resolution of 1/50 of the turbine diameter. Mean flow reversal is observed immediately behind the turbine for cases with rotation. The turbine wake is highly three-dimensional and asymmetric throughout the investigated region, which extends up to 7 diameters downstream. A vortex pair, generated at the upwind-turning side of the turbine, plays a dominant role in wake dynamics by entraining faster fluid from the freestream and aiding in wake recovery. The higher TSR case shows a larger region of reverse flow and greater asymmetry in the near wake of the turbine, but faster wake recovery due to the increase in vortex pair strength with increasing TSR. The present measurement technique also provides detailed information about flow in the vicinity of the turbine blades and within the turbine rotor. The details of the flow field around VAWTs and in their wakes can inform the design of high-density VAWT wind farms, where wake interaction between turbines is a principal consideration.

  1. Large-eddy simulation analysis of turbulent flow over a two-blade horizontal wind turbine rotor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Young [Dept. of Mechanical Engineering, Carnegie Mellon University, Pittsburgh (United States); You, Dong Hyun [Dept. of Mechanical Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of)

    2016-11-15

    Unsteady turbulent flow characteristics over a two-blade horizontal wind turbine rotor is analyzed using a large-eddy simulation technique. The wind turbine rotor corresponds to the configuration of the U.S. National Renewable Energy Laboratory (NREL) phase VI campaign. The filtered incompressible Navier-Stokes equations in a non-inertial reference frame fixed at the centroid of the rotor, are solved with centrifugal and Coriolis forces using an unstructured-grid finite-volume method. A systematic analysis of effects of grid resolution, computational domain size, and time-step size on simulation results, is carried out. Simulation results such as the surface pressure coefficient, thrust coefficient, torque coefficient, and normal and tangential force coefficients are found to agree favorably with experimental data. The simulation showed that pressure fluctuations, which produce broadband flow-induced noise and vibration of the blades, are especially significant in the mid-chord area of the suction side at around 70 to 95 percent spanwise locations. Large-scale vortices are found to be generated at the blade tip and the location connecting the blade with an airfoil cross section and the circular hub rod. These vortices propagate downstream with helical motions and are found to persist far downstream from the rotor.

  2. Transient stability and control of wind turbine generation based on Hamiltonian surface shaping and power flow control

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, David G.; Robinett, Rush D. III [Sandia National Laboratories, Albuquerque, NM (United States). Energy, Resources and Systems Analysis Center

    2010-07-01

    The swing equations for renewable generators connected to the grid are developed and a simple wind turbine with UPFC is used as an example. The swing equations for renewable generator are formulated as a natural Hamiltonian system with externally applied non-conservative forces. A two-step process referred to as Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) is used to analyze and design feedback controllers for the renewable generators system. This formulation extends previous results on the analytical verification of the Potential Energy Boundary Surface (PEBS) method to nonlinear control analysis and design and justifies the decomposition of the system into conservative and nonconservative systems to enable a two-step, serial analysis and design procedure. This paper presents the analysis and numerical simulation results for a nonlinear control design example that includes the One-Machine Infinite Bus (OMIB) system with a Unified Power Flow Control (UPEC) and applied to a simplified wind turbine generator. The needed power and energy storage/charging responses are also determined. (orig.)

  3. The on-line graph processing study on phase separation of two-phase flow in T-tube

    International Nuclear Information System (INIS)

    Qian Yong; Xu Jijun; Yang Zhilin; Chen Yifen

    1997-01-01

    The on-line graph processing measure system is equipped with and experimental study of phase separation of air-water bubbly flow in the horizontal T-junction is carried out. For the first time, the author have found and defined the new type of complete phase separation, by the visual experiment, which shows that under certain conditions, the air flow entering the T junction will flow into the run outlet completely, which had never been reported in the literature Also, the pressure wave feed back effect and the branch bubble flow reorganization effect were found and analyzed. The complexity of this phase separation phenomenon in the T junction has been further revealed via the on-line graph processing technology. Meanwhile the influences of the inlet mass flow rate W1, the inlet mass quality X1, and the mass extraction rate G3/G1 on phase separation were analyzed

  4. Groundwater flow, quality (2007-10), and mixing in the Wind Cave National Park area, South Dakota

    Science.gov (United States)

    Long, Andrew J.; Ohms, Marc J.; McKaskey, Jonathan D.R.G.

    2012-01-01

    A study of groundwater flow, quality, and mixing in relation to Wind Cave National Park in western South Dakota was conducted during 2007-11 by the U.S. Geological Survey in cooperation with the National Park Service because of water-quality concerns and to determine possible sources of groundwater contamination in the Wind Cave National Park area. A large area surrounding Wind Cave National Park was included in this study because to understand groundwater in the park, a general understanding of groundwater in the surrounding southern Black Hills is necessary. Three aquifers are of particular importance for this purpose: the Minnelusa, Madison, and Precambrian aquifers. Multivariate methods applied to hydrochemical data, consisting of principal component analysis (PCA), cluster analysis, and an end-member mixing model, were applied to characterize groundwater flow and mixing. This provided a way to assess characteristics important for groundwater quality, including the differentiation of hydrogeologic domains within the study area, sources of groundwater to these domains, and groundwater mixing within these domains. Groundwater and surface-water samples collected for this study were analyzed for common ions (calcium, magnesium, sodium, bicarbonate, chloride, silica, and sulfate), arsenic, stable isotopes of oxygen and hydrogen, specific conductance, and pH. These 12 variables were used in all multivariate methods. A total of 100 samples were collected from 60 sites from 2007 to 2010 and included stream sinks, cave drip, cave water bodies, springs, and wells. In previous approaches that combined PCA with end-member mixing, extreme-value samples identified by PCA typically were assumed to represent end members. In this study, end members were not assumed to have been sampled but rather were estimated and constrained by prior hydrologic knowledge. Also, the end-member mixing model was quantified in relation to hydrogeologic domains, which focuses model results on

  5. Evaluation of Available Transfer Capability Using Transient Stability Constrained Line Flows

    Science.gov (United States)

    Uzoechi, Lazarus Okechukwu; Mahajan, Satish M.

    2014-01-01

    This paper presents a methodology to evaluate transient stability constrained available transfer capability (ATC). A linear and fast line flow-based (LFB) method was adopted to optimize the ATC values. This enabled the direct determination of the system source-sink locations. This paper formulated different market transactions considering bilateral and multilateral impacts in the stability constrained ATC. The proposed method was demonstrated on the WECC 9-bus and IEEE 39-bus systems. The critical energy performance index (CEPI) enabled the direct identification of candidates for contingency screening based on ranking. This index helped to reduce the list of credible contingencies for ATC evaluation and, therefore, the computation time. The results of the proposed ATC method are consistent with the literature and can be deployed for fast assessment of the impact of transactions in an electric power system.

  6. Hybrid RANS/LES method for wind flow over complex terrain

    DEFF Research Database (Denmark)

    Bechmann, Andreas; Sørensen, Niels N.

    2010-01-01

    The use of Large Eddy Simulation (LES) to predict wall-bounded flows has presently been limited to low Reynolds number flows. Since the number of computational grid points required to resolve the near-wall turbulent structures increase rapidly with Reynolds number, LES has been unattainable...... for flows at high Reynolds numbers. To reduce the computational cost of traditional LES, a hybrid method is proposed in which the near-wall eddies are modelled in a Reynolds-averaged sense. Close to walls, the flow is treated with the Reynolds-averaged Navier-Stokes (RANS) equations (unsteady RANS......), and this layer acts as wall model for the outer flow handled by LES. The well-known high Reynolds number two-equation k - turbulence model is used in the RANS layer and the model automatically switches to a two-equation k - subgrid scale stress model in the LES region. The approach can be used for flow over...

  7. Contact Line Instability of Gravity-Driven Flow of Power-Law Fluids.

    Science.gov (United States)

    Hu, Bin; Kieweg, Sarah L

    2015-11-01

    The moving contact line of a thin fluid film can often corrugate into fingers, which is also known as a fingering instability. Although the fingering instability of Newtonian fluids has been studied extensively, there are few studies published on contact line fingering instability of non-Newtonian fluids. In particular, it is still unknown how shear-thinning rheological properties can affect the formation, growth, and shape of a contact line instability. Our previous study (Hu and Kieweg, 2012) showed a decreased capillary ridge formation for more shear-thinning fluids in a 2D model (i.e. 1D thin film spreading within the scope of lubrication theory). Those results motivated this study's hypothesis: more shear-thinning fluids should have suppressed finger growth and longer finger wavelength, and this should be evident in linear stability analysis (LSA) and 3D (i.e. 2D spreading) numerical simulations. In this study, we developed a LSA model for the gravity-driven flow of shear-thinning films, and carried out a parametric study to investigate the impact of shear-thinning on the growth rate of the emerging fingering pattern. A fully 3D model was also developed to compare and verify the LSA results using single perturbations, and to explore the result of multiple-mode, randomly imposed perturbations. Both the LSA and 3D numerical results confirmed that the contact line fingers grow faster for Newtonian fluids than the shear-thinning fluids on both vertical and inclined planes. In addition, both the LSA and 3D model indicated that the Newtonian fluids form fingers with shorter wavelengths than the shear-thinning fluids when the plane is inclined; no difference in the most unstable (i.e. emerging) wavelength was observed at vertical. This study also showed that the distance between emerging fingers was smaller on a vertical plane than on a less-inclined plane for shear-thinning fluids, as previously shown for Newtonian fluids. For the first time for shear

  8. Paraffin dispersant application for cleaning subsea flow lines in the deep water Gulf of Mexico cottonwood development

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, David; White, Jake; Pogoson, Oje [Baker Hughes Inc., Houston, TX (United States); Barros, Dalmo; Ramachandran, Kartik; Bonin, George; Waltrich, Paulo; Shecaira, Farid [PETROBRAS America, Houston, TX (United States); Ziglio, Claudio [Petroleo Brasileiro S.A. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisa e Desenvolvimento

    2012-07-01

    This paper discusses a paraffin dispersant (in seawater) application to clean paraffin deposition from a severely restricted 17.4-mile dual subsea flow line system in the Gulf of Mexico Cottonwood development. In principle, dispersant treatments are simple processes requiring effective dispersant packages and agitation to break-up and disperse deposition. Dispersants have been used onshore for treating wax deposition for decades. Implementation of a treatment in a long deep water production system, however, poses numerous challenges. The Cottonwood application was one of the first ever deep water dispersant applications. The application was designed in four separate phases: pre-treatment displacement for hydrate protection, dispersant treatment for paraffin deposition removal, pigging sequence for final flow line cleaning, and post-treatment displacement for hydrate protection. In addition, considerable job planning was performed to ensure the application was executed in a safe and environmentally responsible manner. Two dynamically positioned marine vessels were used for pumping fluids and capturing returns. The application was extremely successful in restoring the deep water flow lines back to near pre-production state. Final pigging operations confirmed the flow lines were cleaned of all restrictions. Significant paraffin deposition was removed in the application. Approximately 900 bbls of paraffin sludge was recovered from the 4000 bbl internal volume flow line loop. Furthermore, the application was completed with zero discharge of fluids. The application provided significant value for the Cottonwood development. It allowed production from wells to be brought on-line at a higher capacity, thereby generating increased revenue. It also allowed resumption of routine pigging operations. As such, the Cottonwood dispersant application illustrates that with proper planning and execution, paraffin dispersant treatments can be highly effective solutions for cleaning

  9. A quasi-one-dimensional theory of sound propagation in lined ducts with mean flow

    Science.gov (United States)

    Dokumaci, Erkan

    2018-04-01

    Sound propagation in ducts with locally-reacting liners has received the attention of many authors proposing two- and three-dimensional solutions of the convected wave equation and of the Pridmore-Brown equation. One-dimensional lined duct models appear to have received less attention. The present paper proposes a quasi-one-dimensional theory for lined uniform ducts with parallel sheared mean flow. The basic assumption of the theory is that the effects of refraction and wall compliance on the fundamental mode remain within ranges in which the acoustic fluctuations are essentially uniform over a duct section. This restricts the model to subsonic low Mach numbers and Helmholtz numbers of less than about unity. The axial propagation constants and the wave transfer matrix of the duct are given by simple explicit expressions and can be applied with no-slip, full-slip or partial slip boundary conditions. The limitations of the theory are discussed and its predictions are compared with the fundamental mode solutions of the convected wave equation, the Pridmore-Brown equation and measurements where available.

  10. Computer-controlled flow injection analysis system for on-line determination of distribution ratios

    International Nuclear Information System (INIS)

    Nekimken, H.L.; Smith, B.F.; Jarvinen, G.D.; Peterson, E.J.; Jones, M.M.

    1988-01-01

    An automated flow injection analysis (FIA) system has been developed for the rapid acquisition of liquid/liquid, metal ion distribution ratios (D). The system features automatic switching between aqueous metal sample and wash solutions, on-line solvent extraction, phase separation, and the simultaneous detection of the separated phases by diode-array spectrophotometry. A comparative study of manual, single-stage liquid/liquid extractions with the flow injection system was completed by using a new extraction system UO 2 2+ /benzene/TOPO (trioctylphosphine oxide)/HBMPPT (4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione). The batch and FIA methods yielded results generally within 5% of each other. The major differences between the two systems are that the FIA system is at least twice as fast, is less labor intensive, is more reproducible, and yields better statistics (a result of the FIA's speed and automation features). Slope analysis of the plotted data from the uranyl extraction studies indicates that the extraction complex is UO 2 (BMPPT) 2 (TOPO)

  11. Signal analysis of acoustic and flow-induced vibrations of BWR main steam line

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa-Paredes, G., E-mail: gepe@xanum.uam.mx [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Prieto-Guerrero, A. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Núñez-Carrera, A. [Comisión Nacional de Seguridad Nuclear y Salvaguardias, Doctor Barragán 779, Col. Narvarte, México, D.F. 03020 (Mexico); Vázquez-Rodríguez, A. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Centeno-Pérez, J. [Instituto Politécnico Nacional, Escuela Superior de Física y Matemáticas Unidad Profesional “Adolfo López Mateos”, Av. IPN, s/n, México, D.F. 07738 (Mexico); Espinosa-Martínez, E.-G. [Departamento de Sistemas Energéticos, Universidad Nacional Autónoma de México, México, D.F. 04510 (Mexico); and others

    2016-05-15

    Highlights: • Acoustic and flow-induced vibrations of BWR are analyzed. • BWR performance after extended power uprate is considered. • Effect of acoustic side branches (ASB) is analyzed. • The ASB represents a reduction in the acoustic loads to the steam dryer. • Methodology developed for simultaneous analyzing the signals in the MSL. - Abstract: The aim of this work is the signal analysis of acoustic waves due to phenomenon known as singing in Safety Relief Valves (SRV) of the main steam lines (MSL) in a typical BWR5. The acoustic resonance in SRV standpipes and fluctuating pressure is propagated from SRV to the dryer through the MSL. The signals are analyzed with a novel method based on the Multivariate Empirical Mode Decomposition (M-EMD). The M-EMD algorithm has the potential to find common oscillatory modes (IMF) within multivariate data. Based on this fact, we implement the M-EMD technique to find the oscillatory mode in BWR considering the measurements obtained collected by the strain gauges located around the MSL. These IMF, analyzed simultaneously in time, allow obtaining an estimation of the effects of the multiple-SRV in the MSL. Two scenarios are analyzed: the first is the signal obtained before the installation of the acoustic dampers (ASB), and the second, the signal obtained after installation. The results show the effectiveness of the ASB to damp the strong resonances when the steam flow increases, which represents an important reduction in the acoustic loads to the steam dryer.

  12. LINES

    Directory of Open Access Journals (Sweden)

    Minas Bakalchev

    2015-10-01

    Full Text Available The perception of elements in a system often creates their interdependence, interconditionality, and suppression. The lines from a basic geometrical element have become the model of a reductive world based on isolation according to certain criteria such as function, structure, and social organization. Their traces are experienced in the contemporary world as fragments or ruins of a system of domination of an assumed hierarchical unity. How can one release oneself from such dependence or determinism? How can the lines become less “systematic” and forms more autonomous, and less reductive? How is a form released from modernistic determinism on the new controversial ground? How can these elements or forms of representation become forms of action in the present complex world? In this paper, the meaning of lines through the ideas of Le Corbusier, Leonidov, Picasso, and Hitchcock is presented. Spatial research was made through a series of examples arising from the projects of the architectural studio “Residential Transformations”, which was a backbone for mapping the possibilities ranging from playfulness to exactness, as tactics of transformation in the different contexts of the contemporary world.

  13. Distributed flow estimation and closed-loop control of an underwater vehicle with a multi-modal artificial lateral line.

    Science.gov (United States)

    DeVries, Levi; Lagor, Francis D; Lei, Hong; Tan, Xiaobo; Paley, Derek A

    2015-03-25

    Bio-inspired sensing modalities enhance the ability of autonomous vehicles to characterize and respond to their environment. This paper concerns the lateral line of cartilaginous and bony fish, which is sensitive to fluid motion and allows fish to sense oncoming flow and the presence of walls or obstacles. The lateral line consists of two types of sensing modalities: canal neuromasts measure approximate pressure gradients, whereas superficial neuromasts measure local flow velocities. By employing an artificial lateral line, the performance of underwater sensing and navigation strategies is improved in dark, cluttered, or murky environments where traditional sensing modalities may be hindered. This paper presents estimation and control strategies enabling an airfoil-shaped unmanned underwater vehicle to assimilate measurements from a bio-inspired, multi-modal artificial lateral line and estimate flow properties for feedback control. We utilize potential flow theory to model the fluid flow past a foil in a uniform flow and in the presence of an upstream obstacle. We derive theoretically justified nonlinear estimation strategies to estimate the free stream flowspeed, angle of attack, and the relative position of an upstream obstacle. The feedback control strategy uses the estimated flow properties to execute bio-inspired behaviors including rheotaxis (the tendency of fish to orient upstream) and station-holding (the tendency of fish to position behind an upstream obstacle). A robotic prototype outfitted with a multi-modal artificial lateral line composed of ionic polymer metal composite and embedded pressure sensors experimentally demonstrates the distributed flow sensing and closed-loop control strategies.

  14. Impact of the surface wind flow on precipitation characteristics over the southern Himalayas: GPM observations

    Science.gov (United States)

    Zhang, Aoqi; Fu, Yunfei; Chen, Yilun; Liu, Guosheng; Zhang, Xiangdong

    2018-04-01

    The distribution and influence of precipitation over the southern Himalayas have been investigated on regional and global scales. However, previous studies have been limited by the insufficient emphasis on the precipitation triggers or the lack of droplet size distribution (DSD) data. Here, precipitating systems were identified using Global Precipitation Mission dual-frequency radar data, and then categorized into five classes according to surface flow from the European Centre for Medium-Range Weather Forecast Interim data. The surface flow is introduced to indicate the precipitation triggers, which is validated in this study. Using case and statistical analysis, we show that the precipitating systems with different surface flow had different precipitation characteristics, including spatio-temporal features, reflectivity profile, DSD, and rainfall intensity. Furthermore, the results show that the source of the surface flow influences the intensity and DSD of precipitation. The terrain exerts different impacts on the precipitating systems of five categories, leading to various distributions of precipitation characteristics over the southern Himalayas. Our results suggest that the introduction of surface flow and DSD for precipitating systems provides insight into the complex precipitation of the southern Himalayas. The different characteristics of precipitating systems may be caused by the surface flow. Therefore, future study on the orographic precipitations should take account the impact of the surface flow and its relevant dynamic mechanism.

  15. Experimental investigation of the flow instability near the attachment-line boundary layer on a yawed cylinder

    International Nuclear Information System (INIS)

    Nishizawa, Akira; Tokugawa, Naoko; Takagi, Shohei

    2009-01-01

    The behavior of small disturbances in a 3-D laminar boundary layer on a yawed cylinder was experimentally investigated. This setup simulates the flow around the leading edge of swept wings. Since multiple instability modes appear near the attachment-line region, a point-source disturbance was artificially introduced to separate these modes. Amplitude and phase distributions of the disturbances originating from the point source were measured using a hotwire probe near the attachment-line flow to test existing theoretical predictions. Hotwire measurements show that two instability modes definitely coexist and overlap in the middle portion of the wedge-shaped region developing downstream of the point source. Decomposition by 2-D fast Fourier transform (FFT) analysis enables us to separate one oblique wave from the other. One of the oblique waves belongs to the cross-flow instability mode, which travels to the attachment line and grows even at Reynolds numbers that are slightly lower than the critical Reynolds number for the attachment-line instability. The origin of the other mode is not identifiable, because it has peculiar characteristics different from both the streamline-curvature instability mode and the cross-flow instability mode. This mode decays in the downstream direction for all frequencies examined. By investigating the spatial characteristics of the small disturbance, the critical Reynolds number for cross-flow instability was successfully determined in the off-attachment-line region. The value, R c = 543, was lower than the critical Reynolds number of R c = 583 for the attachment-line flow. Furthermore, the critical frequency and wavenumber were in good agreement with existing predictions based on linear stability theory.

  16. Ulysses near-ecliptic observations of differential flow between protons and alphas in the solar wind

    Science.gov (United States)

    Neugebauer, M.; Goldstein, B. E.; Bame, S. J.; Feldman, W. C.

    1994-01-01

    The evolution of differential streaming between protons and alpha particles in the solar wind was observed with the solar wind plasma experiment on the Ulysses spacecraft over the solar range of 1.15 to 5.40 AU between November 18, 1990, and May 5, 1992. The correlation of the difference in ion speeds, Delta V = the absolute value of V(sub alpha) - the absolute value of V(sub p), with the proton speed V(sub p) observed by other spacecraft at solar distances less than or equal to 1 AU disappeared at approximately 2 AU. At solar distances greater than or equal to 2.85 AU, the largest values of both V(sub alpha p) = the absolute value of V(sub alpha p) = the absolute value of V(sub alpha) - V(sub p) and the absolute value of Delta V were found in the interaction regions on the leading edges of high-speed streams. The differential streaming was typically enhanced just downstream of strong forward and reverse shocks, and large negative values of Delta V were frequently encountered in the interaction regions. A correlation between V(sub alpha p) and the ratio tau(sub zero)/tau(sub e) of Coulomb collision time to expansion time was observed at all distances, but it is suggested that at the larger values of tau(sub zero)/tau(sub e) observed correlation may arise from enhanced production of differential streaming by processes that also increase the entropy of the solar wind protons.

  17. Ultra-high-speed digital in-line holography system applied to particle-laden supersonic underexpanded jet flows

    DEFF Research Database (Denmark)

    Ingvorsen, Kristian Mark; Buchmann, Nicolas A.; Soria, Julio

    2012-01-01

    -fluid interactions in these high-speed flows special high performance techniques are required. The present work is an investigation into the applicability of magnified digital in-line holography with ultra-high-speed recording for the study of three-dimensional supersonic particle-laden flows. An optical setup...... for magnified digital in-line holography is created, using an ultra-high-speed camera capable of frame rates of up to 1.0MHz. To test the new technique an axisymmetric supersonic underexpanded particle-laden jet is investigated. The results show that the new technique allows for the acquisition of time resolved...

  18. Flow visualization system for wind turbines without blades applied to micro reactors

    International Nuclear Information System (INIS)

    Santos, G.S.B.; Guimarães, L.N.F.; Placco, G.M.

    2017-01-01

    Flow visualization systems is a tool used in science and industry for characterization of projects that operate with drainage. This work presents the design and construction of a flow visualization system for passive turbines used in advanced fast micro reactors. In the system were generated images where it is possible to see the supersonic and transonic flow through the turbine disks. A test bench was assembled to generate images of the interior of the turbine where the flow is supersonic, allowing the study of the behavior of the boundary layer between disks. It is necessary to characterize the boundary layer of this type of turbine because its operation occurs in the transfer of kinetic energy between the fluid and the disks. The images generated, as well as their analyzes are presented as a result of this work

  19. Load Flow Analysis of Hybrid AC-DC Power System with Offshore Wind Power

    DEFF Research Database (Denmark)

    Dhua, Debasish; Huang, Shaojun; Wu, Qiuwei

    2017-01-01

    is to model such hybrid AC-DC systems including the interfacing converters, which have several control parameters that can change the load flow of the hybrid systems. Then, the paper proposes a Load Flow algorithm based on the Newton-Raphson method, which covers three different section types...... of the transmission system: the AC parts, the DC parts and the interfacing converters. Finally, this paper validates this algorithm through a detailed case study with a typical hybrid network...

  20. Soil slip/debris flow localized by site attributes and wind-driven rain in the San Francisco Bay region storm of January 1982

    Science.gov (United States)

    Pike, R.J.; Sobieszczyk, S.

    2008-01-01

    GIS analysis at 30-m resolution reveals that effectiveness of slope-destabilizing processes in the San Francisco Bay area varies with compass direction. Nearly half the soil slip/debris flows mapped after the catastrophic rainstorm of 3-5 January 1982 occurred on slopes that face S to WSW, whereas fewer than one-quarter have a northerly aspect. Azimuthal analysis of hillside properties for susceptible terrain near the city of Oakland suggests that the skewed aspect of these landslides primarily reflects vegetation type, ridge and valley alignment, and storm-wind direction. Bedrock geology, soil expansivity, and terrain height and gradient also were influential but less so; the role of surface curvature is not wholly resolved. Normalising soil-slip aspect by that of the region's NNW-striking topography shifts the modal azimuth of soil-slip aspect from SW to SE, the direction of origin of winds during the 1982 storm-but opposite that of the prevailing WNW winds. Wind from a constant direction increases rainfall on windward slopes while diminishing it on leeward slopes, generating a modelled difference in hydrologically effective rainfall of up to 2:1 on steep hillsides in the Oakland area. This contrast is consistent with numerical simulations of wind-driven rain and with rainfall thresholds for debris-flow activity. We conclude that storm winds from the SE in January 1982 raised the vulnerability of the Bay region's many S-facing hillsides, most of which are covered in shallow-rooted shrub and grass that offer minimal resistance to soil slip. Wind-driven rainfall also appears to have controlled debris-flow location in a major 1998 storm and probably others. Incorporating this overlooked influence into GIS models of debris-flow likelihood would improve predictions of the hazard in central California and elsewhere.

  1. Aircraft dynamics, wind tunnel testing, and CFD flow visualization of two linked UAVs flying at close proximity

    Science.gov (United States)

    Cuji, Edgar A.; Lukaczyk, Trent W.; Garcia, Ephrahim

    2010-04-01

    This paper presents an analysis of close proximity aerodynamics and aircraft dynamics of two Linked UAVs. As the UAVs approach each other for wingtip docking there will be strong aerodynamic coupling between their wings tips. Lifting line and Computational Fluid Dynamics (CFD) simulation as well as wind tunnel testing of close proximity effects on lift, drag, roll, pitch and yaw moments for two UAV wings has been performed. The proximity aerodynamics effects between the UAVs wings were analyzed as a function of its relative position in all three directions. A look-up library of aerodynamic forces and moments for relative positions and angles of attack between the two UAVs has been developed. In this study we examined how the close proximity aerodynamics affects the dynamics and stability of the UAVs. The aircraft dynamics analysis is done in Simulink, which will include the close proximity aerodynamic look-up library. An aerodynamic disturbance intensity field will be generated, utilizing both simulation and wind tunnel data, to determine a trajectory for the two UAVs to approach each other for docking.

  2. ILS - a passive insulation solution to answer cool down time challenges on ultra deep water flow lines

    Energy Technology Data Exchange (ETDEWEB)

    Hallot, R.; Couprie, St. [Bouygues Offshore, Montigny-le-Bretonneux, 78 - St-Quentin-Yvelines (France); Chomard, A. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France)

    2002-12-01

    Flow assurance issues are more and more driving the design of Deep Water Flow-lines and Cool Down Time requirement has a major impact on the global system design for most West African sub-sea field developments. Bouygues Offshore and IFP have developed a new thermal insulation solution, named ILS (Liquid solid Insulation), based on the use of phase change materials (PCM). In normal flowing conditions, the PCM liquefied by the oil's heat flux acts as a heat accumulator. During production shutdowns and resulting cool down, the phase change material's crystallization restores partially this stored heat to the flow-line. Therefore, such an insulated coating produces a significant thermal inertia to the flow-line and the cool down delay before hydrates formation is 2 to 4 tunes longer in regard to the existing insulation technologies. Due to the incompressibility, the low density and the low cost of chosen phase change materials, ILS is able to deal with deep-water and ultra deep-water flow assurance requirements and to compete with existing pipe-in-pipe or syntactic thermal insulation. This paper presents the principle of the ILS solution and the main results achieved through the development program, from the theoretical analysis to the qualification tests. (authors)

  3. Flow measurement behind a pair of vertical-axis wind turbines

    Science.gov (United States)

    Parker, Colin M.; Hummels, Raymond; Leftwich, Megan C.

    2017-11-01

    The wake from a pair of vertical-axis wind turbines (VAWTs) is measured using particle imaging velocimetry (PIV). The VAWT models are mounted in a low-speed wind tunnel and driven using a motor control system. The rotation of the turbines is synced using a proportional controller that allows the turbine's rotational position to be set relative to each other. The rotation of the turbines is also synced with the PIV system for taking phase averaged results. The VAWTs are tested for both co- and counter-rotating cases over a range of relative phase offsets. Time averaged and phase averaged results are measured at the horizontal mid-plane in the near wake. The time-averaged results compare the bulk wake profiles from the pair of turbines. Phase averaged results look at the vortex interactions in the near wake of the turbines. By changing the phase relation between the turbines we can see the impact of the structure interactions in both the phase and time averaged results.

  4. in the wind clothes dance on a line. Performative inquiry: A (re)search methodology. Possibilities and absences within a space-moment of imagining a universe

    Science.gov (United States)

    Fels, Lynn Margaret

    in the wind clothes dance on a line is the conceptualization and articulation of performative inquiry as a research methodology within the field of education. Performative inquiry invites innovative and non-linear investigations, playing upon the multiple realities and interpretations of co-evolving worlds realized and recognized through creative action and interaction between researcher/teacher and participants/students within individual and shared, existing and imagined environments through motivating (im)pulse(s) of inquiry. Performative inquiry is elusively and momentarily balanced on the "edge of chaos" within the interstices of enactivism, complexity, interpretation, and performance. In articulating an ecological-cognitive reading of performance, I am in company with curricular theorists who envision curriculum as a journey and expression of students' and teachers' shared investigations within co-evolving landscapes of action and interaction. in the wind clothes dance on a line is a playful response to current conversations among researchers seeking recognition and articulation of arts-based processes as legitimate site(s) and praxis of research. Performative inquiry offers researchers---in drama education, in particular, and in education, in general---a theoretical and practical venue to investigate their fields of inquiry through an integrated vehicle of body, mind and imagination. This dissertation is informed by a three year science education research project (1995--1997) conducted with science educator, Karen Meyer. Our research investigated the teaching and learning of science education through drama and storytelling, culminating in a performance piece, Light Sound Movin' Around: What Are Monsters Made Of? Follow-up interviews with pre-service teachers speak eloquently to the possibility and power of performative inquiry as a research tool and learning vehicle in science education. in the wind clothes dance on a line has been imagined "in the air

  5. An experimental study on a suction flow control method to reduce the unsteadiness of the wind loads acting on a circular cylinder

    Science.gov (United States)

    Chen, Wen-Li; Li, Hui; Hu, Hui

    2014-04-01

    An experimental investigation was conducted to assess the effectiveness of a suction flow control method for vortex-induced vibration (VIV) suppression. The flow control method uses a limited number of isolated suction holes to manipulate the vortex shedding in the wake behind a circular cylinder in order to reduce the unsteadiness of the dynamic wind loads acting on the cylinder. The experimental study was performed at Re ≈ 3.0 × 104, i.e., in the typical Reynolds number range of VIV for the cables of cable-stayed bridges. In addition to measuring the surface pressure distributions to determine the resultant dynamic wind loads acting on the test model, a digital particle image velocimetry system was used to conduct detailed flow field measurements to reveal the changes in the shedding process of the unsteady wake vortex structures from the test model with and without the suction flow control. The effects of important controlling parameters (i.e., the azimuthal locations of the suction holes in respect to the oncoming airflow, the spanwise spacing between the suction holes, and the suction flow rate through the suction holes) on the wake flow characteristics, the surface pressure distributions, and the resultant dynamic wind loads were assessed quantitatively. While a higher suction flow rate and smaller spanwise spacing between the suction holes were beneficial to the effectiveness of the suction flow control, the azimuthal locations of the suction holes were found to be very critical for reducing the fluctuating amplitudes of the dynamic wind loads acting on the test model using the suction flow control method. With the suction holes located at the proper azimuthal locations on the test model (i.e., at the azimuthal angle of θ = 90° and 270° for the present study), the characteristics of the wake flow behind the test model were found to change significantly along the entire span of the test model, even though only a limited number of the isolated suction

  6. PROBABILISTIC HAZARD ASSESSMENT FOR TORNADOES, STRAIGHT-LINE WIND, AND EXTREME PRECIPITATION AT THE SAVANNAH RIVER SITE

    Energy Technology Data Exchange (ETDEWEB)

    Werth, D.; (NOEMAIL), A.; Shine, G.

    2013-12-04

    Recent data sets for three meteorological phenomena with the potential to inflict damage on SRS facilities - tornadoes, straight winds, and heavy precipitation - are analyzed using appropriate statistical techniques to estimate occurrence probabilities for these events in the future. Summaries of the results for DOE-mandated return periods and comparisons to similar calculations performed in 1998 by Weber, et al., are given. Using tornado statistics for the states of Georgia and South Carolina, we calculated the probability per year of any location within a 2⁰ square area surrounding SRS being struck by a tornado (the ‘strike’ probability) and the probability that any point will experience winds above set thresholds. The strike probability was calculated to be 1.15E-3 (1 chance in 870) per year and wind speeds for DOE mandated return periods of 50,000 years, 125,000 years, and 1E+7 years (USDOE, 2012) were estimated to be 136 mph, 151 mph and 221 mph, respectively. In 1998 the strike probability for SRS was estimated to be 3.53 E-4 and the return period wind speeds were 148 mph every 50,000 years and 180 mph every 125,000 years. A 1E+7 year tornado wind speed was not calculated in 1998; however a 3E+6 year wind speed was 260 mph. The lower wind speeds resulting from this most recent analysis are largely due to new data since 1998, and to a lesser degree differences in the models used. By contrast, default tornado wind speeds taken from ANSI/ANS-2.3-2011 are somewhat higher: 161 mph for return periods of 50,000 years, 173 mph every 125,000 years, and 230 mph every 1E+7 years (ANS, 2011). Although the ANS model and the SRS models are very similar, the region defined in ANS 2.3 that encompasses the SRS also includes areas of the Great Plains and lower Midwest, regions with much higher occurrence frequencies of strong tornadoes. The SRS straight wind values associated with various return periods were calculated by fitting existing wind data to a Gumbel

  7. Wall modeled LES of wind turbine wakes with geometrical effects

    Science.gov (United States)

    Bricteux, Laurent; Benard, Pierre; Zeoli, Stephanie; Moureau, Vincent; Lartigue, Ghislain; Vire, Axelle

    2017-11-01

    This study focuses on prediction of wind turbine wakes when geometrical effects such as nacelle, tower, and built environment, are taken into account. The aim is to demonstrate the ability of a high order unstructured solver called YALES2 to perform wall modeled LES of wind turbine wake turbulence. The wind turbine rotor is modeled using an Actuator Line Model (ALM) while the geometrical details are explicitly meshed thanks to the use of an unstructured grid. As high Reynolds number flows are considered, sub-grid scale models as well as wall modeling are required. The first test case investigated concerns a wind turbine flow located in a wind tunnel that allows to validate the proposed methodology using experimental data. The second test case concerns the simulation of a wind turbine wake in a complex environment (e.g. a Building) using realistic turbulent inflow conditions.

  8. On-line monitoring system development for single-phase flow accelerated corrosion

    International Nuclear Information System (INIS)

    Lee, Na Young; Lee, Seung Gi; Ryu, Kyung Ha; Hwang, Il Soon

    2007-01-01

    Aged nuclear piping has been reported to undergo corrosion-induced accelerated failures, often without giving signatures to current inspection campaigns. Therefore, we need diverse sensors which can cover a wide area in an on-line application. We suggest an integrated approach to monitor the flow accelerated corrosion (FAC) susceptible piping. Since FAC is a combined phenomenon, we need to monitor as many parameters as possible and that cover wide area, since we do not know where the FAC occurs. For this purpose, we introduce the wearing rate model which focuses on the electrochemical parameters. Using this model, we can predict the wearing rate and then compare testing results. Through analysis we identified feasibility and then developed electrochemical sensors for high temperature application; we also introduced a mechanical monitoring system which is still under development. To support the validation of the monitored results, we adopted high temperature ultrasonic transducer (UT), which shows good resolution in the testing environment. As such, all the monitored results can be compared in terms of thickness. Our validation tests demonstrated the feasibility of sensors. To support direct thickness measurement for a wide-area, the direct current potential drop (DCPD) method will be researched to integrate into the developed framework

  9. Comparison of AI techniques to solve combined economic emission dispatch problem with line flow constraints

    International Nuclear Information System (INIS)

    Jacob Raglend, I.; Veeravalli, Sowjanya; Sailaja, Kasanur; Sudheera, B.; Kothari, D.P.

    2010-01-01

    A comparative study has been made on the solutions obtained using combined economic emission dispatch (CEED) problem considering line flow constraints using different intelligent techniques for the regulated power system to ensure a practical, economical and secure generation schedule. The objective of the paper is to minimize the total production cost of the power generation. Economic load dispatch (ELD) and economic emission dispatch (EED) have been applied to obtain optimal fuel cost of generating units. Combined economic emission dispatch (CEED) is obtained by considering both the economic and emission objectives. This bi-objective CEED problem is converted into single objective function using price penalty factor approach. In this paper, intelligent techniques such as genetic algorithm (GA), evolutionary programming (EP), particle swarm optimization (PSO), differential evolution (DE) are applied to obtain CEED solutions for the IEEE 30-bus system and 15-unit system. This proposed algorithm introduces an efficient CEED approach that obtains the minimum operating cost satisfying unit, emission and network constraints. The proposed algorithm has been tested on two sample systems viz the IEEE 30-bus system and a 15-unit system. The results obtained by the various artificial intelligent techniques are compared with respect to the solution time, total production cost and convergence criteria. The solutions obtained are quite encouraging and useful in the economic emission environment. The algorithm and simulation are carried out using Matlab software. (author)

  10. Evaluation of numerical flow and dispersion simulations for street canyons with avenue-like tree planting by comparison with wind tunnel data

    OpenAIRE

    Gromke, CB Christof; Buccolieri, R; Sabatino, S Di; Ruck, B

    2008-01-01

    Abstract: Flow and traffic-originated pollutant dispersion in an urban street canyon with avenue-like tree planting have been studied by means of wind tunnel and CFD investigations. The study comprises tree planting of different crown porosity, planted in two rows within a canyon of street width to building height ratio W/H = 2 and street length to building height ratio L/H = 10 exposed to a perpendicular approaching boundary layer flow. Numerical simulations have been performed with...

  11. Fluid flow and thin-film evolution near the triple line during droplet evaporation of self-rewetting fluids.

    Science.gov (United States)

    Yang, Yang; Zhou, Leping; Du, Xiao-Ze; Yang, Yongping

    2018-03-07

    The microscopic region near the triple line plays an important role in the heat and mass transfer of droplets, while the mechanisms of evaporation and internal flow remain unclear. This paper describes an experimental study of fluid flow and thin-film evolution near the triple line in sessile droplets of self-rewetting fluids, aqueous solutions of alcohols with number of carbon atoms varies from 1 to 7, to analyze the influence of various factors on the mesoscale flows. The mechanism of internal flow for self-rewetting fluid droplets was different from that of conventional fluids, and hence a novel expression of in-plane average velocity was fitted for them. The temporal and spatial evolution of thin-film thickness near the triple line during droplet evaporation was obtained by using a proposed sub-region method, which was developed from an evanescent wave based multilayer nanoparticle image velocimetry technique. The self-rewetting fluids are conducive to increase the microscopic critical contact angle and the energy barrier of contact line, which reduces the rate of thin-film thickness variation. The inhibited impact of self-rewetting fluids on the evaporation increases gradually with increasing number of carbon atoms.

  12. Computational issues and applications of line-elements to model subsurface flow governed by the modified Helmholtz equation

    Science.gov (United States)

    Bakker, Mark; Kuhlman, Kristopher L.

    2011-09-01

    Two new approaches are presented for the accurate computation of the potential due to line elements that satisfy the modified Helmholtz equation with complex parameters. The first approach is based on fundamental solutions in elliptical coordinates and results in products of Mathieu functions. The second approach is based on the integration of modified Bessel functions. Both approaches allow evaluation of the potential at any distance from the element. The computational approaches are applied to model transient flow with the Laplace transform analytic element method. The Laplace domain solution is computed using a combination of point elements and the presented line elements. The time domain solution is obtained through a numerical inversion. Two applications are presented to transient flow fields, which could not be modeled with the Laplace transform analytic element method prior to this work. The first application concerns transient single-aquifer flow to wells near impermeable walls modeled with line-doublets. The second application concerns transient two-aquifer flow to a well near a stream modeled with line-sinks.

  13. AFM AND XPS Characterization of Zinc-Aluminum Alloy Coatings with Attention to Surface Dross and Flow Lines

    Science.gov (United States)

    Harding, Felipe A.; Alarcon, Nelson A.; Toledo, Pedro G.

    Surfaces of various zinc-aluminum alloy (Zn-Al) coated steel samples are studied with attention to foreign surface dross by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS/ESCA). AFM topographic maps of zinc-aluminum alloy surfaces free of dross reveal the perfect nanoscale details of two kinds of dendrites: branched and globular. In all magnifications the dendrites appear smooth and, in general, very clean. XPS analysis of the extreme surface of a Zn-Al sample reveals Al, Zn, Si and O as the main components. The XPS results show no segregation or separation of phases other than those indicated by the ternary Al-Zn-Si diagram. For surfaces of Zn-Al plagued with impurities, high resolution AFM topographic maps reveal three situations: (1) areas with well-defined dendrites, relatively free of dross; (2) areas with small, millimeter-sized black spots known as dross; and (3) areas with large black stains, known as flow lines. Dendrite deformation and dross accumulation increase notably in the neighborhood, apparently clean to the naked eye, of dross or flow lines. XPS results of areas with dross and flow lines indicate unacceptable high concentration of Si and important Si phase separation. These results, in the light of AFM work, reveal that dross and flow lines are a consequence of a high local concentration of Si from high melting point silica and silicate impurities in the Zn-Al alloy source.

  14. Trends and perspectives of flow injection/sequential injection on-line sample-pretreatment schemes coupled to ETAAS

    DEFF Research Database (Denmark)

    Wang, Jianhua; Hansen, Elo Harald

    2005-01-01

    Flow injection (FI) analysis, the first generation of this technique, became in the 1990s supplemented by its second generation, sequential injection (SI), and most recently by the third generation (i.e.,Lab-on-Valve). The dominant role played by FI in automatic, on-line, sample pretreatments in ...

  15. The dynamics of buoyant jets in a linearly stratified ambient cross-flow: Implications for the interaction between volcanic plumes and wind

    Science.gov (United States)

    Carazzo, Guillaume; Girault, Frédéric; Aubry, Thomas; Bouquerel, Hélène; Kaminski, Édouard

    2014-05-01

    Volcanic plumes produced by explosive eruptions commonly interact with atmospheric wind causing plume bending and a reduction of its maximum rise height. It is well known that the maximum height reached by a buoyant plume rising in a cross-flow with uniform velocity is controlled by the plume buoyancy flux at the source, the strength of the initial environmental density stratification, the wind velocity and the efficiency of turbulent entrainment. Although numerous studies have been carried out to understand the effects of variations of environmental and source conditions on the plume maximum height, turbulent entrainment has not been taken into account with the same level of detailed analysis. Here, we present new laboratory experiments aimed at better understanding the contribution of the turbulent entrainment to determining the plume maximum height. The experiments consist in injecting downward fresh water in a tank containing an aqueous NaCl solution with linear density stratification. The jet source is towed at a constant speed through the stationary fluid in order to produce a cross-flow. According to the range of source and environmental conditions, the buoyant jet is distorted or bent-over and its maximum rise height is reduced up to a factor of 2 when wind speed is high. We quantify the efficiency of turbulent entrainment due to wind in our experiments and we show that the dynamical regime strongly depends on the ratio of the horizontal wind speed and the vertical plume velocity, and on the Richardson number defined at the source. Our results provide a robust framework to characterize the entrainment coefficient due to wind in a 1D model of turbulent jet rising in a linearly stratified ambient cross-flow, and hence can be used for the assessment of the impact of atmospheric winds on the dynamics of explosive volcanic plumes.

  16. Numerical simulation of flow through cascade in wind tunnel test section and stand-alone configurations

    Czech Academy of Sciences Publication Activity Database

    Fořt, J.; Fürst, J.; Halama, J.; Hric, V.; Louda, P.; Luxa, Martin; Šimurda, David

    2018-01-01

    Roč. 319, February (2018), s. 633-646 ISSN 0096-3003 Institutional support: RVO:61388998 Keywords : numerical simulation * experimental investigation * transonic flow Subject RIV: BK - Fluid Dynamics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 1.738, year: 2016 https://www. science direct.com/ science /article/pii/S0096300317305015

  17. A mixed spectral-integration model for neutral mean wind flow over hills

    DEFF Research Database (Denmark)

    Corbett, Jean-Francois; Ott, Søren; Landberg, Lars

    2008-01-01

    A linear model for neutral surface-layer flow over orography is presented. The Reynolds-Averaged Navier-Stokes and E - epsilon turbulence closure equations are expressed in a terrain-following coordinate system created from a simple analytical expression in the Fourier domain. The perturbation eq...

  18. A novel spectral analysis algorithm to obtain local scalar field statistics from line-of-sight measurements in turbulent flows

    International Nuclear Information System (INIS)

    Kolhe, Pankaj S; Agrawal, Ajay K

    2009-01-01

    Statistical tomography to obtain local field variables from non-intrusive line-of-sight measurements in turbulent flows has been an intriguing subject for some time. In this study, a novel algorithm is presented to obtain statistical information on the local scalar field in axisymmetric turbulent flows. The algorithm uses line-of-sight transverse deflection angle measurements in only one view direction to greatly simplify the optical configuration. The validity of the algorithm is examined using noise-free synthetically generated scalar data that simulate the concentration field of a turbulent helium jet. Results show that the proposed algorithm provides excellent reconstruction of integral length scale and variance of refractive index difference, which can be related to scalar physical properties such as density, temperature and/or species concentrations. Good reconstruction accuracy and the need for a simple optical configuration make the proposed algorithm a promising method to characterize the scalar field in turbulent flows using path-integrated measurements

  19. Transient and steady state performance analysis of power flow control in a DFIG variable speed wind turbine

    Science.gov (United States)

    Nwosu, Cajethan M.; Oti, Stephen E.; Ogbuka, Cosmas U.

    2017-01-01

    This paper presents transient and steady state performance analysis of power flow control in a 5.0 kW Doubly-Fed Induction Generator (DFIG) Variable Speed Wind Turbine (VSWT) under sub synchronous speed, super synchronous speed and synchronous speed modes of operation. Stator flux orientation is used for the control of the rotor-side converter (RSC) and DFIG whereas the grid (or stator) voltage orientation is the preferred choice for the control of the grid-side converter (GSC). In each of the three speeds modes, power is always supplied to the grid through the stator of the DFIG. The magnitude of net power (stator power plus rotor power) is less than stator power during the sub synchronous speed mode; it is greater than stator power during the super synchronous speed mode while it is equal to the stator power during the synchronous speed mode. In synchronous speed mode, the rotor power is zero indicating that power is neither supplied to the grid from the rotor nor supplied to the rotor from the grid; here the magnitude of net power is equal to stator power. The simulation results thus obtained in a MATLAB/SIMULINK environment laid credence to the controllability of power flow reversal in a DFIG-VSWT through back-to-back power electronic converter.

  20. Electromagnetic, flow and thermal study of a miniature planar spiral transformer with planar, spiral windings

    Directory of Open Access Journals (Sweden)

    J. B. DUMITRU

    2014-04-01

    Full Text Available This paper presents mathematical modeling and numerical simulation results for a miniature, planar, spiral transformer (MPST fabricated in micro-electromechanical MEMS technology. When the MPST is magnetic nanofluid cored, magnetization body forces occur, entraining it into a complex flow. This particular MPST design is then compared with other competing solutions concerning the lumped (circuit parameters. Finally, the heat transfer problem is solved for different electromagnetic working conditions to assess the thermal loads inside the MPST.

  1. Probabilistic Constrained Load Flow Considering Integration of Wind Power Generation and Electric Vehicles

    DEFF Research Database (Denmark)

    Vlachogiannis, Ioannis (John)

    2009-01-01

    are incorporated into load flow studies. In the resulted PCLF formulation, discrete and continuous control parameters are engaged. Therefore, a hybrid learning automata system (HLAS) is developed to find the optimal offline control settings over a whole planning period of power system. The process of HLAS...... integration of WT generation in correlation with EV demand/supply into the electricity grids are also introduced, resulting in the first benchmark. Novel conclusions for EV portfolio management are drawn....

  2. Visualization of Flow in Pressurizer Spray Line Piping and Estimation of Thermal Stress Fluctuation Caused by Swaying of Water Surface

    Science.gov (United States)

    Oumaya, Toru; Nakamura, Akira; Onojima, Daisuke; Takenaka, Nobuyuki

    The pressurizer spray line of PWR plants cools reactor coolant by injecting water into pressurizer. Since the continuous spray flow rate during commercial operation of the plant is considered insufficient to fill the pipe completely, there is a concern that a water surface exists in the pipe and may periodically sway. In order to identify the flow regimes in spray line piping and assess their impact on pipe structure, a flow visualization experiment was conducted. In the experiment, air was used substituted for steam to simulate the gas phase of the pressurizer, and the flow instability causing swaying without condensation was investigated. With a full-scale mock-up made of acrylic, flow under room temperature and atmospheric pressure conditions was visualized, and possible flow regimes were identified based on the results of the experiment. Three representative patterns of swaying of water surface were assumed, and the range of thermal stress fluctuation, when the surface swayed instantaneously, was calculated. With the three patterns of swaying assumed based on the visualization experiment, it was confirmed that the thermal stress amplitude would not exceed the fatigue endurance limit prescribed in the Japanese Design and Construction Code.

  3. Turbulence and wind turbines

    DEFF Research Database (Denmark)

    Brand, Arno J.; Peinke, Joachim; Mann, Jakob

    2011-01-01

    The nature of turbulent flow towards, near and behind a wind turbine, the effect of turbulence on the electricity production and the mechanical loading of individual and clustered wind turbines, and some future issues are discussed.......The nature of turbulent flow towards, near and behind a wind turbine, the effect of turbulence on the electricity production and the mechanical loading of individual and clustered wind turbines, and some future issues are discussed....

  4. Comoving frame models of hot star winds I. Test of the Sobolev approximation in the case of pure line transitions

    Czech Academy of Sciences Publication Activity Database

    Krtička, J.; Kubát, Jiří

    2010-01-01

    Roč. 519, September (2010), A50/1-A50/9 ISSN 0004-6361 R&D Projects: GA ČR GA205/07/0031 Institutional research plan: CEZ:AV0Z10030501 Keywords : stars * winds * outflows Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.410, year: 2010

  5. Complex Flow Workshop Report

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2012-05-01

    This report documents findings from a workshop on the impacts of complex wind flows in and out of wind turbine environments, the research needs, and the challenges of meteorological and engineering modeling at regional, wind plant, and wind turbine scales.

  6. Modeling and simulations for molecular scale hydrodynamics of the moving contact line in immiscible two-phase flows

    KAUST Repository

    Qian, Tiezheng

    2009-10-29

    This paper starts with an introduction to the Onsager principle of minimum energy dissipation which governs the optimal paths of deviation and restoration to equilibrium. Then there is a review of the variational approach to moving contact line hydrodynamics. To demonstrate the validity of our continuum hydrodynamic model, numerical results from model calculations and molecular dynamics simulations are presented for immiscible Couette and Poiseuille flows past homogeneous solid surfaces, with remarkable overall agreement. Our continuum model is also used to study the contact line motion on surfaces patterned with stripes of different contact angles (i.e. surfaces of varying wettability). Continuum calculations predict the stick-slip motion for contact lines moving along these patterned surfaces, in quantitative agreement with molecular dynamics simulation results. This periodic motion is tunable through pattern period (geometry) and contrast in wetting property (chemistry). The consequence of stick-slip contact line motion on energy dissipation is discussed. © 2009 IOP Publishing Ltd.

  7. Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

    DEFF Research Database (Denmark)

    Guntur, Srinivas; Sørensen, Niels N.; Schreck, Scott

    2016-01-01

    Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation; (2) data from unsteady delayed detached eddy simulations (DDES) carried out using the Technical University of Denmark’s in-house flow solver Ellipsys3D; and (3) data from...... agreement between the model and the experimental data in many cases, which suggests that the current two-dimensional dynamic stall model as used in blade element momentum-based aeroelastic codes may provide a reasonably accurate representation of three-dimensional rotor aerodynamics when used in combination...

  8. Wind-Tunnel Survey of an Oscillating Flow Field for Application to Model Helicopter Rotor Testing

    Science.gov (United States)

    Mirick, Paul H.; Hamouda, M-Nabil H.; Yeager, William T., Jr.

    1990-01-01

    A survey was conducted of the flow field produced by the Airstream Oscillator System (AOS) in the Langley Transonic Dynamics Tunnel (TDT). The magnitude of a simulated gust field was measured at 15 locations in the plane of a typical model helicopter rotor when tested in the TDT using the Aeroelastic Rotor Experimental System (ARES) model. These measurements were made over a range of tunnel dynamic pressures typical of those used for an ARES test. The data indicate that the gust field produced by the AOS is non-uniform across the tunnel test section, but should be sufficient to excite a model rotor.

  9. Warm-season severe wind events in Germany

    Science.gov (United States)

    Gatzen, Christoph

    2013-04-01

    A 15-year data set of wind measurements was analyzed with regard to warm season severe wind gusts in Germany. For April to September of the years 1997 to 2011, 1035 wind measurements of 26 m/s or greater were found. These wind reports were associated with 268 wind events. In total, 252 convective wind events contributed to 837 (81%) of the wind reports, 16 non-convective synoptic-scale wind events contributed to 198 reports (19%). Severe wind events were found with synoptic situations characterized by rather strong mid-level flow and advancing mid-level troughs. Severe convective wind events were analyzed using radar images and classified with respect to the observed radar structure. The most important convective mode was squall lines that were associated with one third of all severe wind gusts, followed by groups, bow echo complexes, and bow echoes. Supercells and cells were not associated with many wind reports. The low contribution of isolated cells indicates that rather large-scale forcing by synoptic-scale features like fronts is important for German severe wind events. Bow echoes were found to be present for 58% of all wind reports. The movement speed of bow echoes indicated a large variation with a maximum speed of 33 m/s. Extreme wind events as well as events with more than 15 wind reports were found to be related to higher movement speeds. Concentrating on the most intense events, derechos seem to be very important to the warm season wind threat in Germany. Convective events with a path length of more than 400 km contributed to 36% of all warm-season wind gusts in this data set. Furthermore, eight of nine extreme gusts exceeding 40 m/s were recorded with derecho events.

  10. Large eddy simulation of flow across in-line tube bundles

    International Nuclear Information System (INIS)

    Sofiane Benhamadouche; Dominique Laurence; Nicolas Jarrin

    2005-01-01

    Previously, Benhamadouche and Laurence (2003) produced very good results for the flow in a staggered tube bundle, using Large Eddy Simulation with EDF in-house finite volume code code-Saturne (Archambeau et al. (2004)). The discretization is based on a collocated arrangement for unstructured grids. A second order scheme in space and time is used with a standard Smagorinsky model. All the wall boundary cells are in the viscous layer, thus, no wall function is applied. The same numerical scheme is tested on a square in-line tube bundle with P/D = 1,44 and Re = 70000 (P is the vertical and horizontal tube spacing, D is the diameter of a tube and the Reynolds number is based on the gap velocity). The tube bundle is assumed infinite; periodic conditions are used in the three directions with an imposed flow rate. The dimensions of the computational domain have to be chosen (the computational cell, see figure 1 and the 3D elevation L z ). Three computations are carried out (see table 1). Case 1 (1200000 cells) gives a non-symmetrical mean solution that impacts the tubes alternatively on the top and the bottom depending on the considered column (see figure 2). Case 2 gives the same behavior with fewer tubes. Case 3 gives a different solution in which the flow impacts the tubes on the same way whatever the column of the tubes (see figure 3). Note that the solution in also non-symmetrical in this case. A comparison of the total mean drag and lift coefficients and their rms values is given in table 2. The qualitative behavior is good for both cases; the rms value of the drag is between 30% to 50% lower than the rms value of the lift. However, Case 3 results are more realistic as the mean of the lift is almost zero and the other values are of the order of magnitude of the ones obtained for other tube bundles (P/D = 1,75 in Chen (1987)). One can conclude that the elevation in the third direction has a more important effect then the domain size and can impact seriously the

  11. LED-Based High-Voltage Lines Warning System

    Directory of Open Access Journals (Sweden)

    Eldar MUSA

    2013-04-01

    Full Text Available LED-based system, running with the current of high-voltage lines and converting the current flowing through the line into the light by using a toroid transformer, has been developed. The transformer’s primary winding is constituted by the high voltage power line. Toroidal core consists of two equal parts and the secondary windings are evenly placed on these two parts. The system is mounted on the high-voltage lines as a clamp. The secondary winding ends are connected in series by the connector on the clamp. LEDs are supplied by the voltage at the ends of secondary. Current flowing through highvoltage transmission lines is converted to voltage by the toroidal transformer and the light emitting LEDs are supplied with this voltage. The theory of the conversion of the current flowing through the line into the light is given. The system, running with the current of the line and converting the current into the light, has been developed. System has many application areas such as warning high voltage lines (warning winches to not hinder the high-voltage lines when working under the lines, warning planes to not touch the high-voltage lines, remote measurement of high-voltage line currents, and local illumination of the line area

  12. Experimental analysis of flow of ductile cast iron in stream lined gating systems

    DEFF Research Database (Denmark)

    Skov-Hansen, Søren; Green, Nick; Tiedje, Niels Skat

    2008-01-01

    Streamlined gating systems have been developed for production of high integrity ductile cast iron parts. Flow of ductile cast iron in streamlined gating systems was studied in glass fronted sand moulds where flow in the gating system and casting was recorded by a digital video camera. These results...... are compared with real time x-ray recordings of melt flow. Results show that flow patterns are the same using both techniques. The glass fronted moulds give global information on flow in the whole gating system and casting while the x-ray analysis gives detailed information on specific areas. The experiments...... show how the quality of pouring, design of ingates, design of bends and flow over cores influence melt flow and act to determine the quality of the castings....

  13. Base-line investigations of birds in relation to an offshore wind farm at Horns Rev, and results from the year of construction

    International Nuclear Information System (INIS)

    Kjaer Christensen, T.; Clausager, I.; Krag Petersen, I.

    2003-01-01

    The present report presents the base-line investigations of birds conducted during August 1999-April 2001 in relation to construction of an offshore wind farm at Horns Rev, 14 km west-south-west of Blaevandshuk, in the Danish North Sea. The report also presents data collected during the period September 2001-April 2002, when construction of the wind farm was in progress. The wind farm will consist of 80 wind turbines, each of 2 MW, and cover an area of c. 20 km 2 . The eastern part of the North Sea constitutes major staging and wintering grounds for huge numbers of water- and seabirds. The area is also known to be an important site for migrating birds, which especially in autumn pass in large numbers. As Denmark has obligations to protect and maintain the bird populations it was laid down in the approval for erection of the wind farm that the impact on birds should be investigated. According to the 1% criteria defined in the Ramsar Convention, the eastern part of the North Sea including the wind farm area is of international importance to divers, Common Tern, and Sandwich Tern. A number of other species, e.g. Common Eider, Common Scoter, Guillemot and Razorbill, are present in the area in significant numbers as well, though these numbers do not make up 1% of the populations. Detailed distributions of birds in the area around and at Horns Rev were virtually unknown until initiation of this project. Previous bird counts in this area have been carried out almost exclusively from the coast and detailed knowledge exists concerning the numbers of roosting at and migrating birds from the westernmost point of Jutland, Blaevandshuk. To describe the numbers and distributions of birds staging and wintering in the Horns Rev area, bird investigations were initiated in 1999 by using standardised transect counts from aircraft. Up to April 2002, 18 aerial counts have been carried out over an area of c. 1,700 km 2 centred on the Horns Rev project area. (au)

  14. Base-line investigations of birds in relation to an offshore wind farm at Horns Rev, and results from the year of construction

    Energy Technology Data Exchange (ETDEWEB)

    Kjaer Christensen, T.; Clausager, I.; Krag Petersen, I.

    2003-04-15

    The present report presents the base-line investigations of birds conducted during August 1999-April 2001 in relation to construction of an offshore wind farm at Horns Rev, 14 km west-south-west of Blaevandshuk, in the Danish North Sea. The report also presents data collected during the period September 2001-April 2002, when construction of the wind farm was in progress. The wind farm will consist of 80 wind turbines, each of 2 MW, and cover an area of c. 20 km{sup 2}. The eastern part of the North Sea constitutes major staging and wintering grounds for huge numbers of water- and seabirds. The area is also known to be an important site for migrating birds, which especially in autumn pass in large numbers. As Denmark has obligations to protect and maintain the bird populations it was laid down in the approval for erection of the wind farm that the impact on birds should be investigated. According to the 1% criteria defined in the Ramsar Convention, the eastern part of the North Sea including the wind farm area is of international importance to divers, Common Tern, and Sandwich Tern. A number of other species, e.g. Common Eider, Common Scoter, Guillemot and Razorbill, are present in the area in significant numbers as well, though these numbers do not make up 1% of the populations. Detailed distributions of birds in the area around and at Horns Rev were virtually unknown until initiation of this project. Previous bird counts in this area have been carried out almost exclusively from the coast and detailed knowledge exists concerning the numbers of roosting at and migrating birds from the westernmost point of Jutland, Blaevandshuk. To describe the numbers and distributions of birds staging and wintering in the Horns Rev area, bird investigations were initiated in 1999 by using standardised transect counts from aircraft. Up to April 2002, 18 aerial counts have been carried out over an area of c. 1,700 km{sup 2} centred on the Horns Rev project area. (au)

  15. Industrial application of ultrasound based in-line rheometry: From stationary to pulsating pipe flow of chocolate suspension in precrystallization process

    Science.gov (United States)

    Ouriev, Boris; Windhab, Erich; Braun, Peter; Birkhofer, Beat

    2004-10-01

    In-line visualization and on-line characterization of nontransparent fluids becomes an important subject for process development in food and nonfood industries. In our work, a noninvasive Doppler ultrasound-based technique is introduced. Such a technique is applied for investigation of nonstationary flow in the chocolate precrystallization process. Unstable flow conditions were induced by abrupt flow interruption and were followed up by strong flow pulsations in the piping system. While relying on available process information, such as absolute pressures and temperatures, no analyses of flow conditions or characterization of suspension properties could possibly be done. It is obvious that chocolate flow properties are sensitive to flow boundary conditions. Therefore, it becomes essential to perform reliable structure state monitoring and particularly in application to nonstationary flow processes. Such flow instabilities in chocolate processing can often lead to failed product quality with interruption of the mainstream production. As will be discussed, a combination of flow velocity profiles, on-line fit into flow profiles, and pressure difference measurement are sufficient for reliable analyses of fluid properties and flow boundary conditions as well as monitoring of the flow state. Analyses of the flow state and flow properties of chocolate suspension are based on on-line measurement of one-dimensional velocity profiles across the flow channel and their on-line characterization with the power-law model. Conclusions about flow boundary conditions were drawn from a calculated velocity standard mean deviation, the parameters of power-law fit into velocity profiles, and volumetric flow rate information.

  16. Analysis of Precipitation (Rain and Snow) Levels and Straight-line Wind Speeds in Support of the 10-year Natural Phenomena Hazards Review for Los Alamos National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Elizabeth J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dewart, Jean Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Deola, Regina [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-12-10

    This report provides site-specific return level analyses for rain, snow, and straight-line wind extreme events. These analyses are in support of the 10-year review plan for the assessment of meteorological natural phenomena hazards at Los Alamos National Laboratory (LANL). These analyses follow guidance from Department of Energy, DOE Standard, Natural Phenomena Hazards Analysis and Design Criteria for DOE Facilities (DOE-STD-1020-2012), Nuclear Regulatory Commission Standard Review Plan (NUREG-0800, 2007) and ANSI/ ANS-2.3-2011, Estimating Tornado, Hurricane, and Extreme Straight-Line Wind Characteristics at Nuclear Facility Sites. LANL precipitation and snow level data have been collected since 1910, although not all years are complete. In this report the results from the more recent data (1990–2014) are compared to those of past analyses and a 2004 National Oceanographic and Atmospheric Administration report. Given the many differences in the data sets used in these different analyses, the lack of statistically significant differences in return level estimates increases confidence in the data and in the modeling and analysis approach.

  17. Wind speed dynamical model in a wind farm

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam; Wisniewski, Rafal

    2010-01-01

    , the dynamic model for wind flow will be established. The state space variables are determined based on a fine mesh defined for the farm. The end goal of this method is to assist the development of a dynamical model of a wind farm that can be engaged for better wind farm control strategies.......This paper presents a model for wind speed in a wind farm. The basic purpose of the paper is to calculate approximately the wind speed in the vicinity of each wind turbine in a farm. In this regard the governing equations of flow will be solved for the whole wind farm. In ideal circumstances...

  18. Microsystem Aeromechanics Wind Tunnel

    Data.gov (United States)

    Federal Laboratory Consortium — The Microsystem Aeromechanics Wind Tunnel advances the study of fundamental flow physics relevant to micro air vehicle (MAV) flight and assesses vehicle performance...

  19. Effect of variable winds on current structure and Reynolds stresses in a tidal flow: analysis of experimental data in the eastern English Channel

    Directory of Open Access Journals (Sweden)

    K. A. Korotenko

    2012-11-01

    Full Text Available Wind and wave effects on tidal current structure and turbulence throughout the water column are examined using an upward-looking acoustic Doppler current profiler (ADCP. The instrument has been deployed on the seafloor of 18-m mean depth, off the north-eastern French coast in the eastern English Channel, over 12 tidal cycles, and covered the period of the transition from mean spring to neap tide, and forcing regimes varied from calm to moderate storm conditions. During storms, we observed gusty winds with magnitudes reaching 15 m s−1 and wave heights reaching up to 1.3 m. Analysis of velocity spectra revealed a noticeable contribution of wind-induced waves to spectral structure of velocity fluctuations within the subsurface layer. Near the surface, stormy winds and waves produced a significant intensification of velocity fluctuations, particularly when the sustained wind blew against the ebb tide flow. As during wavy periods, the variance-derived Reynolds stress estimates might include a wave-induced contamination, we applied the Variance Fit method to obtain unbiased stresses and other turbulent quantities. Over calm periods, the turbulent quantities usually decreased with height above the seabed. The stresses were found to vary regularly with the predominantly semidiurnal tidal flow. The along-shore stress being generally greater during the flood flow (~2.7 Pa than during the ebb flow (~−0.6 Pa. The turbulent kinetic energy production rate, P, and eddy viscosity, Az, followed a nearly regular cycle with close to a quarter-diurnal period. As for the stresses, near the seabed, we found the maximum values of estimated quantities of P and Az to be 0.1 Wm−3 and 0.5 m2 s−1, respectively, during the flood flow. Over the storm periods, we found the highest unbiased stress values (~−2.6 Pa during ebb when tidal currents were opposite to the

  20. O Star Wind Mass-Loss Rates and Shock Physics from X-ray Line Profiles in Archival XMM RGS Data

    Science.gov (United States)

    Cohen, David

    O stars are characterized by their dense, supersonic stellar winds. These winds are the site of X-ray emission from shock-heated plasma. By analyzing high-resolution X-ray spectra of these O stars, we can learn about the wind-shock heating and X-ray production mechanism. But in addition, the X-rays can also be used to measure the mass-loss rate of the stellar wind, which is a key observational quantity whose value affects stellar evolution and energy, momentum, and mass input to the Galactic interstellar medium. We make this X-ray based mass-loss measurement by analyzing the profile shapes of the X-ray emission lines observed at high resolution with the Chandra and XMM-Newton grating spectrometers. One advantage of our method is that it is insensitive to small-scale clumping that affects density-squared diagnostics. We are applying this analysis technique to O stars in the Chandra archive, and are finding mass-loss rates lower than those traditionally assumed for these O stars, and in line with more recent independent determinations that do account for clumping. By extending this analysis to the XMM RGS data archive, we will make significant contributions to the understanding of both X-ray production in O stars and to addressing the issue of the actual mass-loss rates of O stars. The XMM RGS data archive provides several extensions and advantages over the smaller Chandra HETGS archive: (1) there are roughly twice as many O and early B stars in the XMM archive; (2) the longer wavelength response of the RGS provides access to diagnostically important lines of nitrogen and carbon; (3) the very long, multiple exposures of zeta Pup provide the opportunity to study this canonical O supergiant's X-ray spectrum in unprecedented detail, including looking at the time variability of X-ray line profiles. Our research team has developed a sophisticated empirical line profile model as well as a computational infrastructure for fitting the model to high-resolution X-ray spectra

  1. Significance of Dungey-cycle flows in Jupiter's and Saturn's magnetospheres, and their identification on closed equatorial field lines

    Directory of Open Access Journals (Sweden)

    S. V. Badman

    2007-05-01

    Full Text Available We consider the contribution of the solar wind-driven Dungey-cycle to flux transport in Jupiter's and Saturn's magnetospheres, the associated voltages being based on estimates of the magnetopause reconnection rates recently derived from observations of the interplanetary medium in the vicinity of the corresponding planetary orbits. At Jupiter, the reconnection voltages are estimated to be ~150 kV during several-day weak-field rarefaction regions, increasing to ~1 MV during few-day strong-field compression regions. The corresponding values at Saturn are ~25 kV for rarefaction regions, increasing to ~150 kV for compressions. These values are compared with the voltages associated with the flows driven by planetary rotation. Estimates of the rotational flux transport in the "middle" and "outer" magnetosphere regions are shown to yield voltages of several MV and several hundred kV at Jupiter and Saturn respectively, thus being of the same order as the estimated peak Dungey-cycle voltages. We conclude that under such circumstances the Dungey-cycle "return" flow will make a significant contribution to the flux transport in the outer magnetospheric regions. The "return" Dungey-cycle flows are then expected to form layers which are a few planetary radii wide inside the dawn and morning magnetopause. In the absence of significant cross-field plasma diffusion, these layers will be characterized by the presence of hot light ions originating from either the planetary ionosphere or the solar wind, while the inner layers associated with the Vasyliunas-cycle and middle magnetosphere transport will be dominated by hot heavy ions originating from internal moon/ring plasma sources. The temperature of these ions is estimated to be of the order of a few keV at Saturn and a few tens of keV at Jupiter, in both layers.

  2. A Dynamic Multi Agent based scheduling for flexible flow line manufacturing system accompanied by dynamic customer demand

    OpenAIRE

    Roudi, Daniral; Barenji, Ali Vatankhah; Barenji, Reza Vatankhah; Hashemipour, Majid

    2016-01-01

    Dynamic rescheduling decision-making problem is an important issue in modern manufacturing system with the feature of combinational computation complexity. This paper introduces a multi-agent based approach using the detailed process, provided by Prometheus methodology, which used for the design of a simultaneous dynamic rescheduling decision making for flexible flow line manufacturing system that working under dynamic customer demand. The application has been completely modeled with the Prom...

  3. Purged window apparatus. [On-line spectroscopic analysis of gas flow systems

    Science.gov (United States)

    Ballard, E.O.

    1982-04-05

    A purged window apparatus is described which utilizes tangentially injected heated purge gases in the vicinity of electromagnetic radiation transmitting windows and a tapered external mounting tube to accelerate these gases to provide a vortex flow on the window surface and a turbulent flow throughout the mounting tube thereby preventing backstreaming of flowing gases under investigation in a chamber to which a plurality of similar purged apparatus is attached with the consequent result that spectroscopic analyses can be undertaken for lengthy periods without the necessity of interrupting the flow for cleaning or replacing the windows due to contamination.

  4. A Generalised Porosity Formalism for Isotropic and Anisotropic Effective Opacity and Its Effects on X-ray Line Attenuation in Clumped O Star Winds

    Science.gov (United States)

    Sundqvist, Jon O.; Owocki, Stanley P.; Cohen, David H.; Leutenegger, Maurice A.; Townsend, Richard H. D.

    2002-01-01

    We present a generalised formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealised model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of bound-free absorption of X- rays in hot star winds, a process not directly affected by clumping in the optically thin limit. We find that the Markov model gives surprisingly similar results to those found previously for the single clump model, suggesting that porous opacity is not very sensitive to details of the assumed clump distribution function. Further, an anisotropic effective opacity favours escape of X-rays emitted in the tangential direction (the venetian blind effect), resulting in a bump of higher flux close to line centre as compared to profiles computed from isotropic porosity models. We demonstrate how this characteristic line shape may be used to diagnose the clump geometry, and we confirm previous results that for optically thick clumping to significantly influence X-ray line profiles, very large porosity lengths, defined as the mean free path between clumps, are required. Moreover, we present the first X-ray line profiles computed directly from line-driven instability simulations using a 3-D patch method, and find that porosity effects from such models also are very small. This further supports the view that porosity has, at most, a marginal effect on X-ray line diagnostics in O stars, and therefore that these diagnostics do indeed provide a good clumping insensitive method for deriving O star mass-loss rates.

  5. On-Line Flutter Prediction Tool for Wind Tunnel Flutter Testing using Parameter Varying Estimation Methodology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes to develop an on-line flutter prediction tool using the parameter varying estimation (PVE) methodology, called the PVE Toolbox,...

  6. Experiments on one-phase thermally stratified flows in nuclear reactor pipe lines

    International Nuclear Information System (INIS)

    Rezende, Hugo Cesar; Navarro, Moyses Alberto; Jordao, Elizabete; Santos, Andre Augusto Campagnole dos

    2009-01-01

    The phenomenon of thermal stratified flows occurs when two different layers of the same liquid at different temperatures flow separately in horizontal pipes without appreciable mixing. This phenomenon was not considered in the design stage of most of the operating nuclear power plants, but in last two decades it has become apparent due to the temperature monitoring of piping systems. The occurrence of temperature differences of about 200 deg C have been found in a narrow band around the hot and cold water interface in components under stratified flows. Loadings due to thermal stratification affected the integrity of safety related piping systems. This paper presents the results of a range of experiments performed to simulate one phase thermally stratified flows in geometry and flow condition representing a nuclear reactor steam generator injection nozzle. They have the objective of studying the flow configurations and understanding the evolution of the thermal stratification process. The driving parameter considered to characterize flow under stratified regime due to difference in specific masses is the Froude number. Different Froude numbers, from 0.018 to 0.22, were obtained in different testes by setting injection cold water flow rates and hot water initial temperatures as planned in the test matrix. Results are presented showing the influence of Froude number on the hot and cold water interface position, temperature gradients and striping phenomenon. (author)

  7. Computational fluid dynamics modeling patterns and force characteristics of flow over in-line four square cylinders

    Directory of Open Access Journals (Sweden)

    Song Yidan

    2017-01-01

    Full Text Available The flow over four square cylinders in an in-line, square arrangement was numerically investigated by using the finite volume method with CFD techniques. The working fluid is an incompressible ideal gas. The length of the sides of the array, L, is equal. The analysis is carried out for a Reynolds number of 300, with center-to-center distance ratios, L/D, ranging from 1.5 to 8.0. To fully understand the flow mechanism, details in terms of lift and drag coefficients and Strouhal numbers of the unsteady wake frequencies are analyzed, and the vortex shedding patterns around the four square cylinders are described. It is concluded that L/D has important effects on the drag and lift coefficients, vortex shedding frequencies, and flow field characteristics.

  8. A mathematical model to predict the optimal test line location and sample volume for lateral flow immunoassays.

    Science.gov (United States)

    Ragavendar, M S; Anmol, Chopra M

    2012-01-01

    Lateral flow immunoassay (LFIA) platform is one of the most relevant technologies for screening and diagnosing clinical conditions. However due to low sensitivity and poor repeatability of the platform it has been used only for limited and non-critical tests. Mathematical models have been used to understand the principles of capillary flow and antibody antigen based immunoreactions in nitrocellulose membrane typically seen in LFIA. The model presented in this paper predicts the optimized location of test line on LFIA strip, sample volume and total reaction time that is needed to achieve the required sensitivity for different analytes on a case to case basis. The membrane properties like capillary flow time (s/cm), concentration and affinity constants of antibodies can be varied and the corresponding effect on strip design can be found. Hence this model can be used as a design tool to optimize the LFIA strip construction and reagent development processes.

  9. THE RISE OF AN IONIZED WIND IN THE NARROW-LINE SEYFERT 1 GALAXY Mrk 335 OBSERVED BY XMM-NEWTON AND HST

    Energy Technology Data Exchange (ETDEWEB)

    Longinotti, A. L. [European Space Astronomy Centre of ESA, Madrid (Spain); Krongold, Y. [Departamento de Astrofisica Extragalactica y Cosmologia, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-264, 04510 Mexico (Mexico); Kriss, G. A.; Ely, J. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gallo, L. [Department of Astronomy and Physics, Saint Mary' s University, Halifax (Canada); Grupe, D. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Komossa, S. [Max Planck Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Mathur, S.; Pradhan, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210-1173 (United States)

    2013-04-01

    We present the discovery of an outflowing ionized wind in the Seyfert 1 galaxy Mrk 335. Despite having been extensively observed by most of the largest X-ray observatories in the last decade, this bright source was not known to host warm absorber gas until recent XMM-Newton observations in combination with a long-term Swift monitoring program have shown extreme flux and spectral variability. High-resolution spectra obtained by the XMM-Newton Reflection Grating Spectrometer (RGS) detector reveal that the wind consists of three distinct ionization components, all outflowing at a velocity of {approx}5000 km s{sup -1}. This wind is clearly revealed when the source is observed at an intermediate flux state (2-5 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1}). The analysis of multi-epoch RGS spectra allowed us to compare the absorber properties at three very different flux states of the source. No correlation between the warm absorber variability and the X-ray flux has been determined. The two higher ionization components of the gas (log {xi} {approx} 2.3 and 3.3) may be consistent with photoionization equilibrium, but we can exclude this for the only ionization component that is consistently present in all flux states (log {xi} {approx} 1.8). We have included archival, non-simultaneous UV data from Hubble Space Telescope (FOS, STIS, COS) with the aim of searching for any signature of absorption in this source that so far was known for being absorption-free in the UV band. In the Cosmic Origins Spectrograph (COS) spectra obtained a few months after the X-ray observations, we found broad absorption in C IV lines intrinsic to the active galactic nucleus and blueshifted by a velocity roughly comparable to the X-ray outflow. The global behavior of the gas in both bands can be explained by variation of the covering factor and/or column density, possibly due to transverse motion of absorbing clouds moving out of the line of sight at broad line region scale.

  10. The dependence of C IV broad absorption line properties on accompanying Si IV and Al III absorption: relating quasar-wind ionization levels, kinematics, and column densities

    Energy Technology Data Exchange (ETDEWEB)

    Filiz Ak, N.; Brandt, W. N.; Schneider, D. P.; Trump, J. R. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Hall, P. B. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3 (Canada); Anderson, S. F. [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Hamann, F. [Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Pâris, I. [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Petitjean, P. [Institut d' Astrophysique de Paris, Universite Paris 6, F-75014 Paris (France); Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Shen, Yue [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); York, Don, E-mail: nfilizak@astro.psu.edu [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)

    2014-08-20

    We consider how the profile and multi-year variability properties of a large sample of C IV Broad Absorption Line (BAL) troughs change when BALs from Si IV and/or Al III are present at corresponding velocities, indicating that the line of sight intercepts at least some lower ionization gas. We derive a number of observational results for C IV BALs separated according to the presence or absence of accompanying lower ionization transitions, including measurements of composite profile shapes, equivalent width (EW), characteristic velocities, composite variation profiles, and EW variability. We also measure the correlations between EW and fractional-EW variability for C IV, Si IV, and Al III. Our measurements reveal the basic correlated changes between ionization level, kinematics, and column density expected in accretion-disk wind models; e.g., lines of sight including lower ionization material generally show deeper and broader C IV troughs that have smaller minimum velocities and that are less variable. Many C IV BALs with no accompanying Si IV or Al III BALs may have only mild or no saturation.

  11. Polysaccharide characterization by hollow-fiber flow field-flow fractionation with on-line multi-angle static light scattering and differential refractometry.

    Science.gov (United States)

    Pitkänen, Leena; Striegel, André M

    2015-02-06

    Accurate characterization of the molar mass and size of polysaccharides is an ongoing challenge, oftentimes due to architectural diversity but also to the broad molar mass (M) range over which a single polysaccharide can exist and to the ultra-high M of many polysaccharides. Because of the latter, many of these biomacromolecules experience on-column, flow-induced degradation during analysis by size-exclusion and, even, hydrodynamic chromatography (SEC and HDC, respectively). The necessity for gentler fractionation methods has, to date, been addressed employing asymmetric flow field-flow fractionation (AF4). Here, we introduce the coupling of hollow-fiber flow field-flow fractionation (HF5) to multi-angle static light scattering (MALS) and differential refractometry (DRI) detection for the analysis of polysaccharides. In HF5, less stresses are placed on the macromolecules during separation than in SEC or HDC, and HF5 can offer a higher sensitivity, with less propensity for system overloading and analyte aggregation, than generally found in AF4. The coupling to MALS and DRI affords the determination of absolute, calibration-curve-independent molar mass averages and dispersities. Results from the present HF5/MALS/DRI experiments with dextrans, pullulans, and larch arabinogalactan were augmented with hydrodynamic radius (RH) measurements from off-line quasi-elastic light scattering (QELS) and by RH distribution calculations and fractogram simulations obtained via a finite element analysis implementation of field-flow fractionation theory by commercially available software. As part of this study, we have investigated analyte recovery in HF5 and also possible reasons for discrepancies between calculated and simulated results vis-à-vis experimentally determined data. Published by Elsevier B.V.

  12. On-Line Detection of Distributed Attacks from Space-Time Network Flow Patterns

    National Research Council Canada - National Science Library

    Baras, J. S; Cardenas, A. A; Ramezani, V

    2003-01-01

    .... The directionality of the change in a network flow is assumed to have an objective or target. The particular problem of detecting distributed denial of service attacks from distributed observations is presented as a working framework...

  13. PIV measurements of acoustic and flow-induced vibration in main stream lines

    International Nuclear Information System (INIS)

    Li, Yanrong; Someya, Satoshi; Okamoto, Koji

    2009-01-01

    Systems with closed side-branches are liable to an excitation of sound, as called cavity tone. In this study, flow-induced acoustic resonances of piping systems containing closed side-branches were investigated experimentally. The present investigation on the coaxial closed side-branches is the first rudimentary study to measure the pressure at the downstream side opening of the cavity by microphone and to visualize the fluid flow in the cross-section by using PIV. High-time-resolved PIV has a possibility to analyze the velocity field and the relation between sound propagation and flow field. The fluid flows at different points in the cavity interact with some phase differences and the relation can be clarified. (author)

  14. Hydrodynamic pressure sensing with an artificial lateral line in steady and unsteady flows

    International Nuclear Information System (INIS)

    Venturelli, Roberto; Akanyeti, Otar; Visentin, Francesco; Fiorini, Paolo; Ježov, Jaas; Toming, Gert; Kruusmaa, Maarja; Chambers, Lily D; Brown, Jennifer; Megill, William M

    2012-01-01

    With the overall goal being a better understanding of the sensing environment from the local perspective of a situated agent, we studied uniform flows and Kármán vortex streets in a frame of reference relevant to a fish or swimming robot. We visualized each flow regime with digital particle image velocimetry and then took local measurements using a rigid body with laterally distributed parallel pressure sensor arrays. Time and frequency domain methods were used to characterize hydrodynamically relevant scenarios in steady and unsteady flows for control applications. Here we report that a distributed pressure sensing mechanism has the capability to discriminate Kármán vortex streets from uniform flows, and determine the orientation and position of the platform with respect to the incoming flow and the centre axis of the Kármán vortex street. It also enables the computation of hydrodynamic features which may be relevant for a robot while interacting with the flow, such as vortex shedding frequency, vortex travelling speed and downstream distance between vortices. A Kármán vortex street was distinguished in this study from uniform flows by analysing the magnitude of fluctuations present in the sensor measurements and the number of sensors detecting the same dominant frequency. In the Kármán vortex street the turbulence intensity was 30% higher than that in the uniform flow and the sensors collectively sensed the vortex shedding frequency as the dominant frequency. The position and orientation of the sensor platform were determined via a comparative analysis between laterally distributed sensor arrays; the vortex travelling speed was estimated via a cross-correlation analysis among the sensors. (paper)

  15. Actuator line/Navier–Stokes computations for the MEXICO rotor: comparison with detailed measurements

    DEFF Research Database (Denmark)

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

    2012-01-01

    line/Navier–Stokes (AL/NS) model developed at the Technical University of Denmark. The AL/NS model was combined with a large eddy simulation technique and used to compute the flow past the MEXICO rotor in free air and in the DNW German‐Dutch wind tunnel for three commonly defined test cases at wind...

  16. In-line monitoring and optimization of powder flow in a simulated continuous process using transmission near infrared spectroscopy.

    Science.gov (United States)

    Alam, Md Anik; Shi, Zhenqi; Drennen, James K; Anderson, Carl A

    2017-06-30

    In-line monitoring of continuous powder flow is an integral part of the continuous manufacturing process of solid oral dosage forms in the pharmaceutical industry. Specifically, monitoring downstream from loss-in-weight (LIW) feeders and/or continuous mixers provides important data about the state of the process. Such measurements support control of the process and thereby enhance product quality. Near Infrared Spectroscopy (NIRS) is a potential PAT tool to monitor the homogeneity of a continuous powder flow stream in pharmaceutical manufacturing. However, the association of analytical results from NIR sampling of the powder stream and the homogeneity (content uniformity) of the resulting tablets provides several challenges; appropriate sampling strategies, adequately robust modeling techniques and poor sensitivities (for low dose APIs) are amongst them. Information from reflectance-based NIRS sampling is limited. The region of the powder bed that is interrogated is confined to the surface where the measurement is made. This potential bias in sampling may, in turn, limit the ability to predict the homogeneity of the finished dosage form. Further, changes to the processing parameters (e.g., rate of powder flow) often have a significant effect on the resulting data. Sample representation, interdependence between process parameters and their effects on powder flow behavior are critical factors for NIRS monitoring of continuous powder flow system. A transmission NIR method was developed as an alternative technique to monitor continuous powder flow and quantify API in the powder stream. Transmission NIRS was used to determine the thickness of the powder stream flowing from a loss-in-weight feeder. The thickness measurement of the powder stream provided an in-depth understanding about the effects of process parameters such as tube angles and powder flow rates on powder flow behaviors. This knowledge based approach helped to define an analytical design space that was

  17. Control voltage and power fluctuations when connecting wind farms

    International Nuclear Information System (INIS)

    Berinde, Ioan; Bălan, Horia; Oros, Teodora Susana

    2015-01-01

    Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve

  18. The flow upstream of a row of aligned wind turbine rotors and its effect on power production

    DEFF Research Database (Denmark)

    Meyer Forsting, Alexander Raul; Troldborg, Niels; Gaunaa, Mac

    2017-01-01

    The blockage developing in front of a laterally aligned row of wind turbines and its impact on power production over a single turbine was analysed using two different numerical methods. The inflow direction was varied from orthogonal to the row until 45◦, with the turbines turning into the wind, ...

  19. Operation and Equivalent Loads of Wind Turbines in Large Wind Farms

    Science.gov (United States)

    Andersen, Soren Juhl; Sorensen, Jens Norkaer; Mikkelsen, Robert Flemming

    2017-11-01

    Wind farms continue to grow in size and as the technology matures, the design of wind farms move towards including dynamic effects besides merely annual power production estimates. The unsteady operation of wind turbines in large wind farms has been modelled with EllipSys3D(Michelsen, 1992, and Sørensen, 1995) for a number of different scenarios using a fully coupled large eddy simulations(LES) and aero-elastic framework. The turbines are represented in the flow fields using the actuator line method(Sørensen and Shen, 2002), where the aerodynamic forces and deflections are derived from an aero-elastic code, Flex5(Øye, 1996). The simulations constitute a database of full turbine operation in terms of both production and loads for various wind speeds, turbulence intensities, and turbine spacings. The operating conditions are examined in terms of averaged power production and thrust force, as well as 10min equivalent flapwise bending, yaw, and tilt moment loads. The analyses focus on how the performance and loads change throughout a given farm as well as comparing how various input parameters affect the operation and loads of the wind turbines during different scenarios. COMWIND(Grant 2104-09- 067216/DSF), Nordic Consortium on Optimization and Control of Wind Farms, Eurotech Greentech Wind project, Winds2Loads, and CCA LES. Ressources Granted on SNIC and JESS. The Vestas NM80 turbine has been used.

  20. Collision Avoidance for UAVs Using Optic Flow Measurement With Line of Sight Rate Equalization and Looming

    National Research Council Canada - National Science Library

    Shelnutt, Paul J

    2008-01-01

    .... The obstacles appear in the field of view of a single forward looking camera. First a 2-D analysis is presented where the rate of the line of sight from the vehicle to each of the obstacles to be avoided is measured...

  1. Visualization of boundary layer separation and passive flow control on airfoils and bodies in wind-tunnel and in-flight experiments

    Directory of Open Access Journals (Sweden)

    Matejka Milan

    2012-04-01

    Full Text Available Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow. Wind-tunnels and in-flight measurements on sailplanes were carried out and effect of passive flow control devices - vortex generators - was surveyed; namely counter-rotating vortex generators and Zig-zag type turbulators were applied. Separation suppression and consequent drag coefficient reduction of test aircrafts was reached. PIV investigation was further extended by Time-Resolved techniques. An important study on structure of the turbulent flow in the lower atmosphere, creating an environment of the soaring flight, was presented.

  2. Visualization of boundary layer separation and passive flow control on airfoils and bodies in wind-tunnel and in-flight experiments

    Science.gov (United States)

    Popelka, Lukas; Kuklova, Jana; Simurda, David; Souckova, Natalie; Matejka, Milan; Uruba, Vaclav

    2012-04-01

    Infrared camera, Particle Image Velocimetry, smoke-wire, tuft filaments and oil-flow visualization techniques were used for wind-tunnel and in-flight investigation of boundary layer separation, both stall and separation bubbles, related to the low-Reynolds numbers transition mechanism. Airfoils of Wortmann FX66 series and FX66 series wing-fuselage interaction, as well as modern airfoils and their wing-fuselage geometry were subject to study. The presence of previously identified structures in the CFD modelling, such as horse-shoe vortices, was confirmed in the flow. Wind-tunnels and in-flight measurements on sailplanes were carried out and effect of passive flow control devices - vortex generators - was surveyed; namely counter-rotating vortex generators and Zig-zag type turbulators were applied. Separation suppression and consequent drag coefficient reduction of test aircrafts was reached. PIV investigation was further extended by Time-Resolved techniques. An important study on structure of the turbulent flow in the lower atmosphere, creating an environment of the soaring flight, was presented.

  3. Optimal Power Flow Control by Rotary Power Flow Controller

    Directory of Open Access Journals (Sweden)

    KAZEMI, A.

    2011-05-01

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

  4. Automated flow-injection method for cadmium determination with pre-concentration and reagent preparation on-line

    Directory of Open Access Journals (Sweden)

    María S. Di Nezio

    2005-02-01

    Full Text Available The spectrophotometric determination of Cd(II using a flow injection system provided with a solid-phase reactor for cadmium preconcentration and on-line reagent preparation, is described. It is based on the formation of a dithizone-Cd complex in basic medium. The calibration curve is linear between 6 and 300 µg L-1 Cd(II, with a detection limit of 5.4 µg L-1, an RSD of 3.7% (10 replicates in duplicate and a sample frequency of 11.4 h-1. The proposed method was satisfactorily applied to the determination of Cd(II in surface, well and drinking waters.

  5. Validation of the actuator disc and actuator line techniques for yawed rotor flows using the New Mexico experimental data

    DEFF Research Database (Denmark)

    Breton, S. P.; Shen, Wen Zhong; Ivanell, S.

    2017-01-01

    Experimental data acquired in the New Mexico experiment on a yawed 4.5m diameter rotor model turbine are used here to validate the actuator line (AL) and actuator disc (AD) models implemented in the Large Eddy Simulation code EllipSys3D in terms of loading and velocity field. Even without modelling...... the AD model can reproduce the averaged features of the flow. The importance of using high quality airfoil data (including 3D corrections) as well as a fine grid resolution is highlighted by the results obtained. Overall, it is found that both models can satisfactorily predict the 3D velocity field...

  6. Validation of the Eddy Viscosity and Lange Wake Models using Measured Wake Flow Characteristics Behind a Large Wind Turbine Rotor

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Sang Hyeon; Kim, Bum Suk; Huh, Jong Chul [Jeju National Univ., Jeju (Korea, Republic of); Go, Young Jun [Hanjin Ind, Co., Ltd., Yangsan (Korea, Republic of)

    2016-01-15

    The wake effects behind wind turbines were investigated by using data from a Met Mast tower and the SCADA (Supervisory Control and Data Acquisition) system for a wind turbine. The results of the wake investigations and predicted values for the velocity deficit based on the eddy viscosity model were compared with the turbulence intensity from the Lange model. As a result, the velocity deficit and turbulence intensity of the wake increased as the free stream wind speed decreased. In addition, the magnitude of the velocity deficit for the center of the wake using the eddy viscosity model was overestimated while the turbulence intensity from the Lange model showed similarities with measured values.

  7. 3D flow investigation near the denticles of biomimetic shark skin model using Digital In-line Holographic Microscopy

    Science.gov (United States)

    Toloui, Mostafa; Hong, Jiarong

    2013-11-01

    It has been hypothesised that the complex microscopic denticles on a shark skin reduce the total drag for a swimming shark. However, the fundamental mechanism of this hydrodynamic function is not fully understood due to the inability to reproduce the complex shark surface and resolve the detailed flow around the skin denticles. Here we report a preliminary experiment using a 3D printed transparent rough surface replicating the morphological features of real shark skin. The model skin consists of closely-packed denticles of 2 mm in scale, i.e. ~ 10 times of the real size. Particle image velocimetry based on digital in-line holography is employed to measure 3D flow structures. To reduce optical abberration and enable imaging around the denticles, we use a fluid medium that has the same optical refractive index as that of the skin model. The experiment is conducted in 2'' ×2'' square channel at a moderate Re number matching the general flow around a cruising shark. Several samples of the 3D velocity field amid and above the denticles are obtained. The follow-up research envisions a large dataset of these samples over the rigid/deformable model operated in stationary/undulating mode to ellucidate the dominant flow structures generated by the denticals. This research is collaborated with Prof. George Lauder's group.

  8. Ion diode performance on a positive polarity inductive voltage adder with layered magnetically insulated transmission line flow

    International Nuclear Information System (INIS)

    Hinshelwood, D. D.; Schumer, J. W.; Allen, R. J.; Commisso, R. J.; Jackson, S. L.; Murphy, D. P.; Phipps, D.; Swanekamp, S. B.; Weber, B. V.; Ottinger, P. F.; Apruzese, J. P.; Cooperstein, G.; Young, F. C.

    2011-01-01

    A pinch-reflex ion diode is fielded on the pulsed-power machine Mercury (R. J. Allen, et al., 15th IEEE Intl. Pulsed Power Conf., Monterey, CA, 2005, p. 339), which has an inductive voltage adder (IVA) architecture and a magnetically insulated transmission line (MITL). Mercury is operated in positive polarity resulting in layered MITL flow as emitted electrons are born at a different potential in each of the adder cavities. The usual method for estimating the voltage by measuring the bound current in the cathode and anode of the MITL is not accurate with layered flow, and the interaction of the MITL flow with a pinched-beam ion diode load has not been studied previously. Other methods for determining the diode voltage are applied, ion diode performance is experimentally characterized and evaluated, and circuit and particle-in-cell (PIC) simulations are performed. Results indicate that the ion diode couples efficiently to the machine operating at a diode voltage of about 3.5 MV and a total current of about 325 kA, with an ion current of about 70 kA of which about 60 kA is proton current. It is also found that the layered flow impedance of the MITL is about half the vacuum impedance.

  9. Profile of the horizontal wind variance near the ground in near neutral flow – K-theory and the transport of the turbulent kinetic energy

    Directory of Open Access Journals (Sweden)

    S. Yahaya

    2009-05-01

    Full Text Available This paper deals with the characteristics of the atmospheric turbulent flow in the vicinity of the ground, and particularly with the profile of the horizontal wind variance. The study is based on experimental measurements performed with fast cup anemometers located near the ground at 5 different levels (from 0.25 to 4 m and sampled at 1 Hz. The experiment was carried over two agricultural plots with various tillage treatments in a fallow semiarid area (Central Aragon, Spain. The results of this study reveal that near the ground surface and under moderate wind, the horizontal wind variance logarithmically increases with height, in direct relationship with the friction velocity and the roughness length scale. A theoretical development has allowed us to link this behaviour to the modeling of the turbulent kinetic energy (TKE transport through the eddy diffusivity. Thus, the study proposes a formulation of the similarity universal function of the horizontal wind variance. Besides, the formulation offers a new method for the determination of the friction velocity and the roughness length scale and can be used for the evaluation of the TKE transport rate.

  10. Climatic wind tunnel for wind engineering tasks

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil

    2015-01-01

    Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf

  11. LHCb base-line level-0 trigger 3D-Flow implementation

    International Nuclear Information System (INIS)

    Crosetto, Dario B.

    1999-01-01

    The LHCb Level-0 trigger implementation with the 3D-Flow system offers full programmability, allowing it to adapt to unexpected operating conditions and enabling new, unpredicted physics. The implementation is described in detail and refers to components and technology available today. The 3D-Flow Processor system is a new, technology-independent concept in very fast, real-time system architectures. Based on the replication of a single type of circuit of 100k gates, which communicates in six directions: bi-directional with North, East, West, and South neighbors, unidirectional from Top to Bottom, the system offers full programmability, modularity, ease of expansion and adaptation to the latest technology. A complete study of its applicability to the LHCb calorimeter triggers is presented. Full description of the input data handling, either in digital or mixed digital-analog form, of the data processing, and the transmission of results to the global level-0 trigger decision unit are provided. Any level-0 trigger algorithm (2x2, 3x3, 4x4, etc.) with up to 20 steps, can be implemented with zero dead-time, while sustaining input data rate (up to 32-bit per input channel, per bunch crossing) at 40 MHz. For each step, each 3D-Flow processor can execute up to 26 operations, inclusive of compare, ranging, finding local maxima, and efficient data exchange with neighboring channels. (One-to-one correspondence between input channel and trigger tower.) Populated with only two main types of components, front-end FPGAs and 3D-Flow processors, a single type of board, it is shown how the whole Level-0 calorimeter trigger can be accommodated into six crates (9U), each containing 16 identical boards. All 3D-Flow inter-chip Bottom to Top ports connection are all contained on the board (data are multiplexed 2 : 1, PCB traces are shorter than 6 cm); all 3D-flow inter-chip North, East, West, and South ports connections, between boards and crates, are multiplexed (8+2) : 1 and are

  12. Challenges in wind farm optimization

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.

    for the wind turbine modeling, where aeroelastic models are required, and for the wind farm flow field description, where in-stationary flow field modeling is needed to capture the complicated mixture of atmospheric boundary layer (ABL) flows and upstream emitted meandering wind turbine wakes, which together...... dictates the fatigue loading of the individual wind turbines. Within an optimization context, the basic challenge in describing the in-stationary wind farm flow field is computational speed. The Dynamic Wake Meandering (DWM) model includes the basic features of a CFD Large Eddy Simulation approach...

  13. Hydrology and Water Quality of the Rio Chama River, Northern New Mexico: Establishing a Base Line to Manage Flows

    Science.gov (United States)

    Salvato, L.; Crossey, L. J.

    2013-12-01

    The Rio Chama is the largest stream tributary to the Rio Grande in northern New Mexico. The river's geographic location in a semiarid region results in high rates of evapotranspiration and highly variable streamflow. The Rio Chama is part of the San Juan-Chama Drinking Water Project, in which water from the San Juan River, southern Colorado, is diverted across the continental divide to the Rio Chama. Surface water moves through Abiquiu, El Vado and Heron Reservoirs to the Rio Grande to supply Albuquerque with potable drinking water. The results of these anthropogenic influences are a modified flow regime, less variability, greater base-flows, and smaller peak flows. We examined selected locations throughout the Rio Chama system to provide base-line water quality data for ongoing studies. This information will contribute to the development of the best plan to optimize flow releases and maximize benefits of the stakeholders and especially the riparian and stream ecosystems. We report results of two sampling trips representing extremes of the hydrograph in summer 2012 and fall 2012. We collected field parameters, processed water samples, and analyzed them for major anions and cations. The geochemistry enables us to better understand the impact of monthly releases of San Juan river water. We captured two points of the river's streamflow range, 54 cubic feet per second in October 2012 and 1,000 cubic feet per second in August 2012 and looked for variability within the results. We found that the reservoirs exhibit varying anion concentrations from samples taken at different depths. We compared stream waters and selected well samples at a stream transect. These samples allowed us to compare shallow ground water with the stream, and they indicated that the changes in ground water are attributed to sulfate reduction. The anion and cation inputs were most likely derived from gypsum, calcite, and salts, as there are many creeks discharging into the Rio Chama whose drainage

  14. Effects of wind turbine wake on atmospheric sound propagation

    DEFF Research Database (Denmark)

    Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong

    2017-01-01

    In this paper, we investigate the sound propagation from a wind turbine considering the effects of wake-induced velocity deficit and turbulence. In order to address this issue, an advanced approach was developed in which both scalar and vector parabolic equations in two dimensions are solved. Flow...... field input was obtained using the actuator line (AL) technique with Large Eddy Simulation (LES) to model the wind turbine and its wake and from an analytical wake model. The effect of incoming wind speed and atmospheric stability was investigated with the analytical wake input using a single point...

  15. Multi Parameter Flow Meter for On-Line Measurement of Gas Mixture Composition

    Directory of Open Access Journals (Sweden)

    Egbert van der Wouden

    2015-04-01

    Full Text Available In this paper we describe the development of a system and model to analyze the composition of gas mixtures up to four components. The system consists of a Coriolis mass flow sensor, density, pressure and thermal flow sensor. With this system it is possible to measure the viscosity, density, heat capacity and flow rate of the medium. In a next step the composition can be analyzed if the constituents of the mixture are known. This makes the approach universally applicable to all gasses as long as the number of components does not exceed the number of measured properties and as long as the properties are measured with a sufficient accuracy. We present measurements with binary and ternary gas mixtures, on compositions that range over an order of magnitude in value for the physical properties. Two platforms for analyses are presented. The first platform consists of sensors realized with MEMS fabrication technology. This approach allows for a system with a high level of integration. With this system we demonstrate a proof of principle for the analyses of binary mixtures with an accuracy of 10%. In the second platform we utilize more mature steel sensor technology to demonstrate the potential of this approach. We show that with this technique, binary mixtures can be measured within 1% and ternary gas mixtures within 3%.

  16. An Axisymmetric Hydrodynamical Model for the Torus Wind in AGN. 2; X-ray Excited Funnel Flow

    Science.gov (United States)

    Dorodnitsyn, A.; Kallman, T.; Proga, D.

    2008-01-01

    We have calculated a series of models of outflows from the obscuring torus in active galactic nuclei (AGN). Our modeling assumes that the inner face of a rotationally supported torus is illuminated and heated by the intense X-rays from the inner accretion disk and black hole. As a result of such heating a strong biconical outflow is observed in our simulations. We calculate 3-dimensional hydrodynamical models, assuming axial symmetry, and including the effects of X-ray heating, ionization, and radiation pressure. We discuss the behavior of a large family of these models, their velocity fields, mass fluxes and temperature, as functions of the torus properties and X-ray flux. Synthetic warm absorber spectra are calculated, assuming pure absorption, for sample models at various inclination angles and observing times. We show that these models have mass fluxes and flow speeds which are comparable to those which have been inferred from observations of Seyfert 1 warm absorbers, and that they can produce rich absorption line spectra.

  17. Photonic Low Cost Micro-Sensor for in-Line Wear Particle Detection in Flowing Lube Oils

    Directory of Open Access Journals (Sweden)

    Jon Mabe

    2017-03-01

    Full Text Available The presence of microscopic particles in suspension in industrial fluids is often an early warning of latent or imminent failures in the equipment or processes where they are being used. This manuscript describes work undertaken to integrate different photonic principles with a micro- mechanical fluidic structure and an embedded processor to develop a fully autonomous wear debris sensor for in-line monitoring of industrial fluids. Lens-less microscopy, stroboscopic illumination, a CMOS imager and embedded machine vision technologies have been merged to develop a sensor solution that is able to detect and quantify the number and size of micrometric particles suspended in a continuous flow of a fluid. A laboratory test-bench has been arranged for setting up the configuration of the optical components targeting a static oil sample and then a sensor prototype has been developed for migrating the measurement principles to real conditions in terms of operating pressure and flow rate of the oil. Imaging performance is quantified using micro calibrated samples, as well as by measuring real used lubricated oils. Sampling a large fluid volume with a decent 2D spatial resolution, this photonic micro sensor offers a powerful tool at very low cost and compacted size for in-line wear debris monitoring.

  18. Photonic Low Cost Micro-Sensor for in-Line Wear Particle Detection in Flowing Lube Oils.

    Science.gov (United States)

    Mabe, Jon; Zubia, Joseba; Gorritxategi, Eneko

    2017-03-14

    The presence of microscopic particles in suspension in industrial fluids is often an early warning of latent or imminent failures in the equipment or processes where they are being used. This manuscript describes work undertaken to integrate different photonic principles with a micro- mechanical fluidic structure and an embedded processor to develop a fully autonomous wear debris sensor for in-line monitoring of industrial fluids. Lens-less microscopy, stroboscopic illumination, a CMOS imager and embedded machine vision technologies have been merged to develop a sensor solution that is able to detect and quantify the number and size of micrometric particles suspended in a continuous flow of a fluid. A laboratory test-bench has been arranged for setting up the configuration of the optical components targeting a static oil sample and then a sensor prototype has been developed for migrating the measurement principles to real conditions in terms of operating pressure and flow rate of the oil. Imaging performance is quantified using micro calibrated samples, as well as by measuring real used lubricated oils. Sampling a large fluid volume with a decent 2D spatial resolution, this photonic micro sensor offers a powerful tool at very low cost and compacted size for in-line wear debris monitoring.

  19. Improved detection of bovine viral diarrhea virus in bovine lymphoid cell lines using PrimeFlow RNA assay.

    Science.gov (United States)

    Falkenberg, Shollie M; Dassanayake, Rohana P; Neill, John D; Ridpath, Julia F

    2017-09-01

    Bovine viral diarrhea virus (BVDV) infections, whether as acute, persistent or contributing to co-infections, result in significant losses for cattle producers. Although, BVDV can be identified readily by real-time PCR and ELISA, detection and quantification of viral infection at the single cell level is extremely difficult. Detection at the single lymphoid cell level is important due to the immunomodulation that accompanies BVDV infection. A novel PrimeFlow RNA assay using in-situ detection of BVDV was evaluated. The model used to develop this technique included three BL-3 cell lines with different infection statuses, one not infected with BVDV, one infected with BVDV and one dual infected with BVDV and bovine leukosis virus. Using RNA probes specific for the BVDV-2a N pro -E rns coding region, BVDV RNA was detected from both contaminated BL-3 cell lines by flow cytometry and fluorescent microscopy. This is the first report on in-situ detection of BVDV at the single-cell level. Published by Elsevier Inc.

  20. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  1. Hot-wire measurement in turbulent flow behind a parallel-line heat source

    Czech Academy of Sciences Publication Activity Database

    Antoš, Pavel; Uruba, Václav

    2012-01-01

    Roč. 12, č. 1 (2012), s. 493-494 ISSN 1617-7061. [Annual Meeting of the International Association of Applied Mathematics and Mechanics /83./. Darmstadt, 26.03.2012-30.03.2012] R&D Projects: GA ČR GPP101/10/P556; GA ČR GAP101/12/1271 Institutional research plan: CEZ:AV0Z20760514 Keywords : nonisotermal flow * hot wire anemometry Subject RIV: BK - Fluid Dynamics http://onlinelibrary.wiley.com/doi/10.1002/pamm.201210235/abstract

  2. Influence of observers and stream flow on northern two-lined salamander (Eurycea bislineata bislineata) relative abundance estimates in Acadia and Shenandoah National Parks, USA

    Science.gov (United States)

    Crocker, J.B.; Bank, M.S.; Loftin, C.S.; Jung Brown, R.E.

    2007-01-01

    We investigated effects of observers and stream flow on Northern Two-Lined Salamander (Eurycea bislineata bislineata) counts in streams in Acadia (ANP) and Shenandoah National Parks (SNP). We counted salamanders in 22 ANP streams during high flow (May to June 2002) and during low flow (July 2002). We also counted salamanders in SNP in nine streams during high flow (summer 2003) and 11 streams during low flow (summers 2001?02, 2004). In 2002, we used a modified cover-controlled active search method with a first and second observer. In succession, observers turned over 100 rocks along five 1-m belt transects across the streambed. The difference between observers in total salamander counts was not significant. We counted fewer E. b. bislineata during high flow conditions, confirming that detection of this species is reduced during high flow periods and that assessment of stream salamander relative abundance is likely more reliable during low or base flow conditions.

  3. Evaluation Of Method Of Line (MOL For Solution Of Soil Water Flow Equations And Comparison With Finite Element Method (FEM

    Directory of Open Access Journals (Sweden)

    ISAM M. Mahammed

    2012-03-01

    Full Text Available The objective of this research is to evaluate Method of Line (MOL used for solution of  water flow equations through porous media using MATLAB package functions for solution of ordinary differential equations ODE,s  , instead of writing long programs codes.  sink & source term to MOL model were included. Then Comparing MOL model with another model that uses finite element method in solving water flow equations (FEM in one dimensional flow using computer program code in FORTRAN.  Two cases were examined for evaluation and comparison of these two models. Firstly, infiltration phenomena using sandy soil was studied with the same parameter for both models.  Results show that there is a divergence between the two models along time of 60 minutes of infiltration. Changes of moisture content with soil depth were sharp with FEM model. Second case, data of  the volume  of water content for wheat field where used taking irrigation and evaporation into account, along the growth period of wheat crop and different depths up to  100 cm. Results show that output of  FEM model has  high degree of agreement with  the measured data for all depths and along all period of growth. Data given by MOL model were less in values than measured data for all depths and along all period of wheat growth time.

  4. LHCb base-line level-0 trigger 3D-flow implementation

    CERN Document Server

    Crosetto, D

    1999-01-01

    The LHCb Level-0 trigger implementation with the 3D-Flow system offers full programmability, allowing it to adapt to unexpected operating conditions and enabling new, unpredicted physics. The implementation is described in detail and refers to components and technology available today. The 3D-Flow Processor system is a new, technology-independent concept in very fast, real-time system architectures. Based on the replication of a single type of circuit of 100 k gates, which communicates in six directions: bi-directional with North, East, West, and South neighbors, unidirectional from Top to Bottom, the system offers full programmability, modularity, ease of expansion and adaptation to the latest technology. A complete study of its applicability to the LHCb calorimeter triggers is presented. Full description of the input data handling, either in digital or mixed digital-analog form, of the data processing, and the transmission of results to the global level-0 trigger decision unit are provided. Any level-0 trig...

  5. Novel simplified hourly energy flow models for photovoltaic power systems

    International Nuclear Information System (INIS)

    Khatib, Tamer; Elmenreich, Wilfried

    2014-01-01

    Highlights: • We developed an energy flow model for standalone PV system using MATLAB line code. • We developed an energy flow model for hybrid PV/wind system using MATLAB line code. • We developed an energy flow model for hybrid PV/diesel system using MATLAB line code. - Abstract: This paper presents simplified energy flow models for photovoltaic (PV) power systems using MATLAB. Three types of PV power system are taken into consideration namely standalone PV systems, hybrid PV/wind systems and hybrid PV/diesel systems. The logic of the energy flow for each PV power system is discussed first and then the MATLAB line codes for these models are provided and explained. The results prove the accuracy of the proposed models. Such models help modeling and sizing PV systems

  6. Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

    Directory of Open Access Journals (Sweden)

    Colin C. Triplett

    2017-01-01

    Full Text Available The meteorological control of gravity wave activity through filtering by winds and generation by spontaneous adjustment of unbalanced flows is investigated. This investigation is based on a new analysis of Rayleigh LiDAR measurements of gravity wave activity in the upper stratosphere-lower mesosphere (USLM,40–50kmon 152 nights at Poker Flat Research Range (PFRR, Chatanika, Alaska (65◦ N, 147◦ W, over 13 years between 1998 and 2014. The LiDAR measurements resolve inertia-gravity waves with observed periods between 1 h and 4 h and vertical wavelengths between 2 km and 10 km. The meteorological conditions are defined by reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA. The gravity wave activity shows large night-to-night variability, but a clear annual cycle with a maximum in winter,and systematic interannual variability associated with stratospheric sudden warming events. The USLM gravity wave activity is correlated with the MERRA winds and is controlled by the winds in the lower stratosphere through filtering by critical layer filtering. The USLM gravity wave activity is also correlated with MERRA unbalanced flow as characterized by the residual of the nonlinear balance equation. This correlation with unbalanced flow only appears when the wind conditions are taken into account, indicating that wind filtering is the primary control of the gravity wave activity.

  7. Does an Open Recirculation Line Affect the Flow Rate and Pressure in a Neonatal Extracorporeal Life Support Circuit With a Centrifugal or Roller Pump?

    Science.gov (United States)

    Wang, Shigang; Spencer, Shannon B; Woitas, Karl; Glass, Kristen; Kunselman, Allen R; Ündar, Akif

    2017-01-01

    The objective of this study is to evaluate the impact of an open or closed recirculation line on flow rate, circuit pressure, and hemodynamic energy transmission in simulated neonatal extracorporeal life support (ECLS) systems. The two neonatal ECLS circuits consisted of a Maquet HL20 roller pump (RP group) or a RotaFlow centrifugal pump (CP group), Quadrox-iD Pediatric oxygenator, and Biomedicus arterial and venous cannulae (8 Fr and 10 Fr) primed with lactated Ringer's solution and packed red blood cells (hematocrit 35%). Trials were conducted at flow rates ranging from 200 to 600 mL/min (200 mL/min increments) with a closed or open recirculation line at 36°C. Real-time pressure and flow data were recorded using a custom-based data acquisition system. In the RP group, the preoxygenator flow did not change when the recirculation line was open while the prearterial cannula flow decreased by 15.7-20.0% (P pump, but did not change perfusion flow in the circuit using a centrifugal pump. An additional flow sensor is needed to monitor perfusion flow in patients if any shunts exist in the ECLS circuit. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  8. Common Envelope Wind Tunnel: Coefficients of Drag and Accretion in a Simplified Context for Studying Flows around Objects Embedded within Stellar Envelopes

    Science.gov (United States)

    MacLeod, Morgan; Antoni, Andrea; Murguia-Berthier, Ariadna; Macias, Phillip; Ramirez-Ruiz, Enrico

    2017-03-01

    This paper examines the properties of flows around objects embedded within common envelopes in the simplified context of a “wind tunnel.” We establish characteristic relationships between key common envelope flow parameters like the Mach number and density scale height. Our wind tunnel is a three-dimensional, Cartesian geometry hydrodynamic simulation setup that includes the gravity of the primary and secondary stars and allows us to study the coefficients of drag and accretion experienced by the embedded object. Accretion and drag lead to a transformation of an embedded object and its orbit during a common envelope phase. We present two suites of simulations spanning a range of density gradients and Mach numbers—relevant for flow near the limb of a stellar envelope to the deep interior. In one suite, we adopt an ideal gas adiabatic exponent of γ =5/3, in the other, γ =4/3. We find that coefficients of drag rise in flows with steeper density gradients and that coefficients of drag and accretion are consistently higher in the more compressible, γ =4/3 flow. We illustrate the impact of these newly derived coefficients by integrating the inspiral of a secondary object through the envelopes of 3{M}⊙ (γ ≈ 5/3) and 80{M}⊙ (γ ≈ 4/3) giants. In these examples, we find a relatively rapid initial inspiral because, near the stellar limb, dynamical friction drag is generated mainly from dense gas focused from deeper within the primary-star’s envelope. This rapid initial inspiral timescale carries potential implications for the timescale of transients from early common envelope interaction.

  9. General aspects of meteorology and wind flow patterns at the National Medical Cyclotron site, Camperdown, NSW, Australia

    International Nuclear Information System (INIS)

    Clark, G.H.; Bartsch, F.J.K.

    1994-06-01

    As part of an assessment into the consequences of a potential accident at the National Medical Cyclotron, Camperdown, NSW., Australia, two meteorological stations were installed to monitor the winds, temperatures and atmospheric dispersion conditions. The data will be used to assess environmental impacts of the Cyclotron's operation. In spite of the relatively poor performance of the stations, the wind data indicated significant effects of local buildings and the general urban surface roughness features. The prevailing winds during the study were from the north-north-west at night and south-south-west or north-east sea breezes during the day. Atmospheric stability/dispersion categories were typical of an urban heat island location. 11 refs., 10 tabs, 6 figs

  10. Flow injection on-line spectrophotometric determination of thorium(IV) after preconcentration on XAD-4 resin impregnated with oxytetracycline

    Energy Technology Data Exchange (ETDEWEB)

    Shahida, Shabnam; Khan, Muhammad Haleem [Univ. of Azad Jammu and Kashmir, Muzaffarabad (Pakistan). Dept. of Chemistry; Ali, Akbar [Pakistan Institute of Nuclear Science and Technology, Islamabad (Pakistan). Chemistry Div.

    2014-02-15

    A very sensitive, selective and simple flow injection time-based method was developed for on-line preconcentration and determination of thorium(IV) at micro g L{sup -1} levels in environmental samples. The system operation was based on thorium(IV) ion retention at pH 4.0 in the minicolumn at a flow rate of 15.2 mL min{sup -1}. The trapped complex was then eluted with 3.6 mol L{sup -1} HCl at a flow rate of 4.9 mL min{sup -1}. The amount of thorium(IV) in the eluate was measured spectrophotometrically at 651 nm using arsenazo-III solution (0.05 % in 3.6 mol L{sup -1} HCl stabilized with 1 % triton X-100, 4.9 mL min{sup -1}) as colorimetric reagent. All chemical, and flow injection variables were optimized for the quantitative preconcentration of metal and a study of interference level of various ions was also carried out. The system offered low backpressure and improved sensitivity and selectivity. At a preconcentration time of 60 s and a sample frequency of 40 h{sup -1}, the enhancement factor was 97, the detection limit was 0.25 μg L{sup -1}, and the precision expressed as relative standard deviation was 1.08 % (at 50 μg L{sup -1}), whereas for 300 s of the preconcentration time and a sample frequency of 10 h{sup -1}, the enhancement factor of 357, the detection limit (3s) of 0.069 μg L{sup -1} and the precision of 1.32 % (at 10 μg L{sup -1}) was reported. The accuracy of the developed method was sufficient and evaluated by the analysis of certified reference material IAEA-SL-1 (Lake Sediment) and spiked water samples.

  11. Martian Dune Ripples as Indicators of Recent Surface Wind Patterns

    Science.gov (United States)

    Johnson, M.; Zimbelman, J. R.

    2015-12-01

    Sand dunes have been shown to preserve the most recent wind patterns in their ripple formations. This investigation continues the manual documentation of ripples on Martian dunes in order to assess surface wind flow. Study sites investigated must have clear HiRISE frames and be able to represent diverse locations across the surface, decided primarily by their spread of latitude and longitude values. Additionally, frames with stereo pairs are preferred because of their ability to create digital terrain models. This will assist in efforts to relate dune slopes and obstacles to ripple patterns. The search and analysis period resulted in 40 study sites with mapped ripples. Lines were drawn perpendicular to ripple crests across three adjacent ripples in order to document both ripple wavelength from line length and inferred wind direction from azimuth. It is not possible to infer a unique wind direction from ripple orientation alone and therefore these inferred directions have a 180 degree ambiguity. Initial results from all study sites support previous observations that the Martian surface has many dune types in areas with adequate sand supply. The complexity of ripple patterns varies greatly across sites as well as within individual sites. Some areas of uniform directionality for hundreds of kilometers suggest a unimodal wind regime while overlapping patterns suggest multiple dominant winds or seasonally varying winds. In most areas, form flow related to dune shape seems to have a large effect on orientation and must be considered along with the dune type. As long as the few steep slip faces on these small dunes are avoided, form flow can be considered the dominant cause of deviation from the regional wind direction. Regional results, wind roses, and comparisons to previous work will be presented for individual sites.

  12. European Wind Atlas and Wind Resource Research in Denmark

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling

    to estimate the actual wind climate at any specific site and height within this region. The Danish and European Wind Atlases are examples of how the wind atlas methodology can be employed to estimate the wind resource potential for a country or a sub-continent. Recently, the methodology has also been used...... - from wind measurements at prospective sites to wind tunnel simulations and advanced flow modelling. Among these approaches, the wind atlas methodology - developed at Ris0 National Laboratory over the last 25 years - has gained widespread recognition and is presently considered by many as the industry......-standard tool for wind resource assessment and siting of wind turbines. The PC-implementation of the methodology, the Wind Atlas Analysis and Application Program (WAsP), has been applied in more than 70 countries and territories world-wide. The wind atlas methodology is based on physical descriptions and models...

  13. Kinetics of Fe(II)-catalyzed transformation of 6-line ferrihydrite under anaerobic flow conditions

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L.; Steefel, C.I.; Marcus, M.A.; Bargar, J.R.

    2010-04-01

    The readsorption of ferrous ions produced by the abiotic and microbially-mediated reductive dissolution of iron oxy-hydroxides drives a series of transformations of the host minerals. To further understand the mechanisms by which these transformations occur and their kinetics within a microporous flow environment, flow-through experiments were conducted in which capillary tubes packed with ferrihydrite-coated glass spheres were injected with inorganic Fe(II) solutions under circumneutral pH conditions at 25 C. Synchrotron X-ray diffraction was used to identify the secondary phase(s) formed and to provide data for quantitative kinetic analysis. At concentrations at and above 1.8 mM Fe(II) in the injection solution, magnetite was the only secondary phase formed (no intermediates were detected), with complete transformation following a nonlinear rate law requiring 28 hours and 150 hours of reaction at 18 and 1.8 mM Fe(II), respectively. However, when the injection solution consisted of 0.36 mM Fe(II), goethite was the predominant reaction product and formed much more slowly according to a linear rate law, while only minor magnetite was formed. When the rates are normalized based on the time to react half of the ferrihydrite on a reduced time plot, it is apparent that the 1.8 mM and 18 mM input Fe(II) experiments can be described by the same reaction mechanism, while the 0.36 input Fe(II) experiment is distinct. The analysis of the transformation kinetics suggest that the transformations involved an electron transfer reaction between the aqueous as well as sorbed Fe(II) and ferrihydrite acting as a semiconductor, rather than a simple dissolution and recrystallization mechanism. A transformation mechanism involving sorbed inner sphere Fe(II) alone is not supported, since the essentially equal coverage of sorption sites in the 18 mM and 1.8 mM Fe(II) injections cannot explain the difference in the transformation rates observed.

  14. Development of on-line monitoring system for flow accelerated corrosion

    International Nuclear Information System (INIS)

    Lee, N.Y.; Lee, S.G.; Hwang, I.S.; Kim, J.T.; Luk, V.K.

    2005-01-01

    Aged nuclear piping has been reported to undergo corrosion-induced accelerated failures, often without giving signatures to current inspection campaigns. Therefore, we need diverse sensors which can cover wide area in the on-line application. We suggested integrated approach to monitor the FAC-susceptible piping. Since FAC is a combined phenomenon, we need to monitor as many parameters as possible, and that cover wide area, since we don't know where the FAC occurs. For this purpose, we introduced wearing rate model, which concentrates on the electrochemical parameters. By the model, we can predict the wearing rate and then can compare the testing result. After we identified feasibility by analytical way, we developed electrochemical sensors for high temperature application, and introduced mechanical monitoring system, which is still under development. To support the validation of the monitored results, we adopted high temperature UT, which shows good resolution in the testing environment. By this way, all the monitored results can be compared in terms of thickness. Validation test shows the feasibility of sensors. To support direct thickness measurement for wide-area, Direct Current Potential Drop method will be researched to integrate to the developed framework. (authors)

  15. Data-driven wind plant control

    NARCIS (Netherlands)

    Gebraad, P.M.O.

    2014-01-01

    Each wind turbine in a cluster of wind turbines (a wind power plant) can influence the performance of other turbines through the wake that forms downstream of its rotor. The wake has a reduced wind velocity, since the turbine extracts energy from the flow, and the obstruction by the wind turbine

  16. Fluorimetric determination of arsanilic acid by flow-injection analysis using on-line photo-oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Ruiz, Tomas; Martinez-Lozano, Carmen; Tomas, Virginia; Martin, Jesus [Department of Analytical Chemistry, University of Murcia (Spain)

    2002-01-01

    A flow-injection-fluorimetric method for the determination of arsanilic acid is proposed. The assay is based on the on-line decomposition of arsanilic acid in the presence of peroxydisulfate on irradiation with UV light. The arsenate generated in the photochemical reaction was reacted with molybdate in dilute nitric acid to form arsenomolybdic acid, which oxidised thiamine to thiochrome. The thiochrome was monitored fluorimetrically at 440 nm with excitation at 375 nm. The calibration graph was linear in the range 0.10-10.8 {mu}g mL{sup -1} with a correlation coefficient of 0.999. The detection limit was 0.01 {mu}g mL{sup -1} and the sample throughput was 55 samples h{sup -1}. The applicability of the method was demonstrated by determining arsanilic acid in animal foodstuffs and water. (orig.)

  17. A multisyringe flow-through sequential extraction system for on-line monitoring of orthophosphate in soils and sediments

    DEFF Research Database (Denmark)

    Buanuam, Janya; Miró, Manuel; Hansen, Elo Harald

    2007-01-01

    of extracted organic phosphorus and condensed inorganic phosphates within the time frame of the assay. The potential of the novel system for accommodation of the harmonized protocol from the Standards, Measurement and Testing (SMT) Program of the Commission of the European Communities for inorganic phosphorus.......5 mol l-1 HCl as extractants according to the Hietjles-Lijklema (HL) scheme for fractionation of phosphorus associated with different geological phases, and on-line processing of the extracts via the Molybdenum Blue (MB) reaction by exploiting multisyringe flow injection as the interface between...... of the operational times from days to hours, highly temporal resolution of the leaching process, and the capability for immediate decision for stopping or proceeding with the ongoing extraction. Very importantly, accurate determination of the various orthophosphate pools is ensured by minimization of the hydrolysis...

  18. Flow injection on-line preconcentration of low levels of Cr(VI) with detection by ETAAS

    DEFF Research Database (Denmark)

    Som-aum, Waraporn; Liawruangrath, Saisunee; Hansen, Elo Harald

    2002-01-01

    A flow injection (FI) on-line sorption preconcentration procedure utilizing a packed column reactor and combined with electrothermal atomic absorption spectrometry (ETAAS) is proposed for the determination of low levels of Cr(VI) in water samples. Polytetrafluoroethylene (PTFE) beads packed...... in a mini-column is used as sorbent material. The complex formed between Cr(VI) and ammonium pyrrolidine dithiocarbamate (APDC) is sorbed on the PTFE beads, and is subsequently eluted by an air-monosegmented discrete zone of absolute ethanol (35mul), the analyte being quantified by ETAAS....... The preconcentration procedure using the proposed column significantly enhances the preconcentration efficiency as compared with the preconcentration approach incorporating an open tubular PTFE knotted reactor (KR). Comparing the two procedure for equal surface sorption area, the advantages of using a packed column...

  19. On-line study of growth kinetics of single hyphae of Aspergillus oryzae in a flow-through cell

    DEFF Research Database (Denmark)

    Christiansen, Torben; Spohr, Anders Bendsen; Nielsen, Jens Bredal

    1999-01-01

    Using image analysis the growth kinetics of the single hyphae of the filamentous fungus Aspergillus oryzae has been determined on-line in a flow-through cell at different glucose concentrations in the range from 26 mg L-1 to 20 g L-1. The tip extension rate of the individual hyphae can be described...... with saturation type kinetics with respect to the length of the hyphae. The maximum tip extension rate is constant for all hyphae measured at the same glucose concentration, whereas the saturation constant for the hyphae varies significantly between the hyphae even within the same hyphal element. When apical...... branching occurs, it is observed that the tip extension rate decreases temporarily. The number of branches formed on a hypha is proportional to the length of the hypha that exceeds a certain minimum length required to support the growth of a new branch. The observed kinetics has been used to simulate...

  20. Multiplex flow cytometry barcoding and antibody arrays identify surface antigen profiles of primary and metastatic colon cancer cell lines.

    Directory of Open Access Journals (Sweden)

    Kumar Sukhdeo

    Full Text Available Colon cancer is a deadly disease affecting millions of people worldwide. Current treatment challenges include management of disease burden as well as improvements in detection and targeting of tumor cells. To identify disease state-specific surface antigen signatures, we combined fluorescent cell barcoding with high-throughput flow cytometric profiling of primary and metastatic colon cancer lines (SW480, SW620, and HCT116. Our multiplexed technique offers improvements over conventional methods by permitting the simultaneous and rapid screening of cancer cells with reduced effort and cost. The method uses a protein-level analysis with commercially available antibodies on live cells with intact epitopes to detect potential tumor-specific targets that can be further investigated for their clinical utility. Multiplexed antibody arrays can easily be applied to other tumor types or pathologies for discovery-based approaches to target identification.