Sample records for gusts

  1. Mean gust shapes

    Larsen, Gunner Chr.


    patterns of a wind turbine when a gust event is imposed. Methods exist to embed a gust of a prescribed appearance in a stochastic wind field. The present report deals with a method to derive realistic gustshapes based only on a few stochastic features of the relevant turbulence field. The investigation...... is limited to investigation of the longitudinal turbulence component, and consequently no attention is paid to wind direction gusts. A theoreticalexpression, based on level crossing statistics, is proposed for the description of a mean wind speed gust shape. The description also allows for information...

  2. Gust modelling for wind loading

    Verheij, F.J.; Cleijne, J.W.; Leene, J.A.


    In this paper the TNO gust analysis method and the resulting TNO gust model are described. The method has been applied to a set of 700 hours of stationary wind speed time series measured at the meteorological mast at Cabauw, The Netherlands. The results are discussed in this paper. The TNO gust mode

  3. Gust modelling for wind loading

    Verheij, F.J.; Cleijne, J.W.; Leene, J.A.


    In this paper the TNO gust analysis method and the resulting TNO gust model are described. The method has been applied to a set of 700 hours of stationary wind speed time series measured at the meteorological mast at Cabauw, The Netherlands. The results are discussed in this paper. The TNO gust

  4. Modelling of extreme gusts for design calculations (NewGust)

    Bierbooms, W.; Po-Wen Cheng [Delft Univ. of Technology, Inst. for Wind Energy, Delft (Netherlands); Larsen, G. [Risoe National Lab., Roskilde (Denmark); Juul Pedersen, B. [Vestas Wind Systems A/S, Lem (Denmark); Hansen, K. [Tecnical Univ. of Denmark (Denmark)


    The main objective of the NewGust project is to come to a realistic and verified description of extreme gusts based on the stochastic properties of wind. In this paper the first results of the project are presented. Theoretical considerations indicate that the shape of extreme gusts is very sharp. Based on simulated wind time series, mean gust shapes (for several amplitudes and mean wind speeds) are determined and compared with the theoretical curves. The resemblance turned out to be very good. Furthermore, the influence of the sampling rate and the dynamics of a cup anemometer on the empirical mean gust shape are examined. The promising results are confirmed by a (preliminary) verification based on measured wind time series, available from the database on wind characteristics. The mean shape of gusts, of certain amplitude, together with their probability of occurrence can be used to obtain the distribution of the extreme response of wind turbines to gust loading. (au)

  5. Modelling of extreme gusts for design calculations (NewGusts)

    Bierbooms, Wim; Cheng, Po-Weng; Larsen, Gunner;


    The main objective of the Newgust project is to come to a realistic and verified description of extreme gusts based on the stochastic properties of the wind. The mean shape of the gusts, of certain amplitude, together with their probability of occurence can be used to obtain the distribution of t...

  6. Forces on Airships in Gusts

    Burgess, C P


    In this report it is shown that determining the instantaneous angle of pitch, the acceleration of the gust is as important as its maximum velocity or yaw. Hitherto it has been assumed that the conditions encountered in gusts could be approximately represented by considering the airship to be at an instantaneous angle of yaw or pitch (according to whether the gust is horizontal or vertical), the instantaneous angle being tan to the (-1) power (v/v), where v is the component of the velocity of the gust at right angles to the longitudinal axis of the ship, and v is the speed of the ship. An expression is derived for this instantaneous angle in terms of the speed and certain aerodynamic characteristics of the airship, and of the maximum velocity and the acceleration of the gust, and the application of the expression to the determination of the forces on the ship is illustrated by numerical examples.

  7. Wind gust warning verification

    Primo, Cristina


    Operational meteorological centres around the world increasingly include warnings as one of their regular forecast products. Warnings are issued to warn the public about extreme weather situations that might occur leading to damages and losses. In forecasting these extreme events, meteorological centres help their potential users in preventing the damage or losses they might suffer. However, verifying these warnings requires specific methods. This is due not only to the fact that they happen rarely, but also because a new temporal dimension is added when defining a warning, namely the time window of the forecasted event. This paper analyses the issues that might appear when dealing with warning verification. It also proposes some new verification approaches that can be applied to wind warnings. These new techniques are later applied to a real life example, the verification of wind gust warnings at the German Meteorological Centre ("Deutscher Wetterdienst"). Finally, the results obtained from the latter are discussed.

  8. Review of gust model concepts

    Powell, D.C.


    Within the past two years Pacific Northwest Laboratory (PNL) has been associated directly or indirectly with several documents in which the authors set forth their concept of a wind component gust model. In this paper three models, each representing a somewhat different concept, are reviewed. A gust model can be defined as a mathematical model that begins by describing wind fluctuations in terms of discrete events and ends by defining statistics of those events. In the present models, all wind fluctuation is described in terms of either individual wind components with respect to a Cartesian coordinate system at a single point, or volume averages of these wind components.

  9. In search of a gust definition

    Kristensen, L.; Casanova, M.; Courtney, M.S.;


    We propose a simple gust definition based on the theory of excursions by Rice (1944 and 1945). We discuss the relation to the distribution of extreme events and demonstrate theoretically and experimentally that the most probable extreme event is very close to being identical to the gust according...... to our definition. We demonstrate how it is possible to predict the gust on the basis of the measured mean wind and variance rather than rely on actually measured extreme excursions. Our gust definition also allows us to predict the average duration of a gust....

  10. Towards spatially constrained gust models

    Bos, R.; Bierbooms, W.; Van Bussel, G.


    With the trend of moving towards 10-20MW turbines, rotor diameters are growing beyond the size of the largest turbulent structures in the atmospheric boundary layer. As a consequence, the fully uniform transients that are commonly used to predict extreme gust loads are losing their connection to rea

  11. On the vertical structure of wind gusts

    Suomi, I.; Gryning, Sven-Erik; Floors, Rogier Ralph


    The increasing size of wind turbines, their height and the area swept by their blades have revised the need for understanding the vertical structure of wind gusts. Information is needed for the whole profile. In this study, we analyzed turbulence measurements from a 100m high meteorological mast...... and the turbulence intensity, of which the turbulence intensity was found to dominate over the peak factor in determining the effects of stability and height above the surface on the gust factor. The peak factor only explained 15% or less of the vertical decrease of the gust factor, but determined the effect of gust...... duration on the gust factor. The statistical method to estimate the peak factor did not reproduce the observed vertical decrease in near-neutral and stable conditions and near-constant situation in unstable conditions. Despite this inconsistency, the theoretical method provides estimates for the peak...

  12. Initial Acceleration Suppression via Gust Alleviation Controller Using Prior Gust Information

    Sato, Masayuki; Yokoyama, Nobuhiro

    This paper first shows the performance limit of gust alleviation controllers without prior gust information. Since control devices, such as elevator, aileron, and thrust, cannot be driven at the same time as their commands are given, the initial acceleration due to wind gust cannot be alleviated with any controllers which do not detect the wind gust a priori. However, if wind gust information is obtained a priori, then the initial acceleration can be suppressed with some controller, which is the second topic of this paper. Designing such controllers is formulated as a design problem of model predictive controllers, which is formulated as a convex Quadratic Programming (QP) problem and is easily solved numerically. Several numerical examples demonstrate the effectiveness of model predictive controllers to suppress the initial acceleration due to wind gust.

  13. Dynamic Gust Load Analysis for Rotors

    Yuting Dai


    Full Text Available Dynamic load of helicopter rotors due to gust directly affects the structural stress and flight performance for helicopters. Based on a large deflection beam theory, an aeroelastic model for isolated helicopter rotors in the time domain is constructed. The dynamic response and structural load for a rotor under the impulse gust and slope-shape gust are calculated, respectively. First, a nonlinear Euler beam model with 36 degrees-of-freedoms per element is applied to depict the structural dynamics for an isolated rotor. The generalized dynamic wake model and Leishman-Beddoes dynamic stall model are applied to calculate the nonlinear unsteady aerodynamic forces on rotors. Then, we transformed the differential aeroelastic governing equation to an algebraic one. Hence, the widely used Newton-Raphson iteration algorithm is employed to simulate the dynamic gust load. An isolated helicopter rotor with four blades is studied to validate the structural model and the aeroelastic model. The modal frequencies based on the Euler beam model agree well with published ones by CAMRAD. The flap deflection due to impulse gust with the speed of 2m/s increases twice to the one without gust. In this numerical example, results indicate that the bending moment at the blade root is alleviated due to elastic effect.

  14. Extreme gust wind estimation using mesoscale modeling

    Larsén, Xiaoli Guo; Kruger, Andries


    through turbulent eddies. This process is modeled using the mesoscale Weather Forecasting and Research (WRF) model. The gust at the surface is calculated as the largest winds over a layer where the averaged turbulence kinetic energy is greater than the averaged buoyancy force. The experiments have been......Currently, the existing estimation of the extreme gust wind, e.g. the 50-year winds of 3 s values, in the IEC standard, is based on a statistical model to convert the 1:50-year wind values from the 10 min resolution. This statistical model assumes a Gaussian process that satisfies the classical...... done for Denmark and two areas in South Africa. For South Africa, the extreme gust atlases from South Africa were created from the output of the mesoscale modelling using Climate Forecasting System Reanalysis (CFSR) forcing for the period 1998 – 2010. The extensive measurements including turbulence...

  15. Gust loading on streamlined bridge decks

    Larose, Guy; Mann, Jakob


    The current analytical description of the buffeting action of wind on long-span bridges is based on the strip assumption. However, recent experiments on closed-box girder bridge decks have shown that this assumption is not valid and is the source of an important part of the error margin...... of the analytical prediction methods. In this paper, an analytical model that departs from the strip assumption is used to describe the gust loading on a thin airfoil. A parallel is drawn between the analytical model and direct measurements of gust loading on motionless closed-box girder bridge decks. Empirical...

  16. Surface-layer gusts for aircraft operation

    Young, G.S.; Kristensen, L.


    We use Monin-Obukhov similarity theory to extend the Kristensen et al. (1991) aviation gust estimation technique from the neutral to the diabatic surface layer. Example calculations demonstrate the importance of this correction. Simple stability class methods using only standard aviation surface ...

  17. Waterbehoefte van guste en drachtige zeugen

    Peet-Schwering, van der C.M.C.; Jongbloed, A.W.; Aarnink, A.J.A.; Blok, M.C.; Dijk, van A.J.; Eleveld, W.; Wesel, van A.A.M.


    Om meer inzicht te krijgen in de waterbehoefte van guste en drachtige zeugen en in factoren die de waterbehoefte beïnvloeden is door het ID-DLO en het Praktijkonderzoek Varkenshouderij gezamenlijk onderzoek hiernaar gedaan. Op het ID-DLO is nagegaan wat het effect is van verschillende water-/voerver

  18. Interaction of gusts with forest edges

    Ruck, Bodo; Tischmacher, Michael


    Experimental investigations in an atmospheric boundary layer wind tunnel were carried out in order to study the interaction of gusts with forest edges. Summarizing the state of knowledge in the field of forest damages generated by extreme storms, there is a strong indication that in many cases, windthrow of trees starts near the forest edge from where it spreads into the stand. The high-transient interaction between gusts and (porous) forest edges produce unsteady flow phenomena not known so far. From a fluid mechanical point of view, the flow type resembles a forward-facing porous step flow, which is significantly influenced by the characteristics of the oncoming atmospheric boundary layer flow and the shape and `porous properties' of the forest edge. The paper reports systematic investigations on the interaction of artificially generated gusts and forest edge models in an atmospheric boundary layer wind tunnel. The experimental investigations were carried out with a laser-based time-resolved PIV-system and high speed photography. Different flow phenomena like gust streching, vortex formation, Kelvin-Helmholtz instabilities or wake production of turbulence could be measured or visualized contributing to the understanding of the complex flow perfomance over the forest edge.

  19. Hanford Site peak gust wind speeds

    Ramsdell, J.V.


    Peak gust wind data collected at the Hanford Site since 1945 are analyzed to estimate maximum wind speeds for use in structural design. The results are compared with design wind speeds proposed for the Hanford Site. These comparisons indicate that design wind speeds contained in a January 1998 advisory changing DOE-STD-1020-94 are excessive for the Hanford Site and that the design wind speeds in effect prior to the changes are still appropriate for the Hanford Site.

  20. Methodology for obtaining wind gusts using Doppler lidar

    Suomi, Irene; Gryning, Sven-Erik; O'Connor, Ewan J.


    . This novel method also provides estimates for wind gusts at arbitrary gust durations, including those shorter than the temporal resolution of the Doppler lidar measurements. The input parameters for the scaling method are the measured wind-gust speed as well as the mean and standard deviation...... of the horizontal wind speed. The method was tested using WindCube V2 Doppler lidar measurements taken next to a 100 m high meteorological mast. It is shown that the method can provide realistic Doppler lidar estimates of the gust factor, i.e. the ratio of the wind-gust speed to the mean wind speed. The method...... speed. To assure the data quality in this study, we applied a filtering technique based on spike detection to remove possible outliers in the Doppler lidar data. We found that the spike detection-removal method clearly improved the wind-gust measurements, both with and without the scaling method. Spike...

  1. A Comprehensive Robust Adaptive Controller for Gust Load Alleviation

    Elisa Capello


    Full Text Available The objective of this paper is the implementation and validation of an adaptive controller for aircraft gust load alleviation. The contribution of this paper is the design of a robust controller that guarantees the reduction of the gust loads, even when the nominal conditions change. Some preliminary results are presented, considering the symmetric aileron deflection as control device. The proposed approach is validated on subsonic transport aircraft for different mass and flight conditions. Moreover, if the controller parameters are tuned for a specific gust model, even if the gust frequency changes, no parameter retuning is required.

  2. 14 CFR 25.679 - Control system gust locks.


    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Control system gust locks. 25.679 Section... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Design and Construction Control Systems § 25.679 Control system gust locks. (a) There must be a device to prevent damage to the control surfaces (including tabs...

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

    XU Xiaoping; ZHU Xiaoping; ZHOU Zhou; FAN Ruijun


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

  4. Gust response of aeroelastically tailored wind turbines

    Scott, S.; Capuzzi, M.; Langston, D.; Bossanyi, E.; McCann, G.; Weaver, PM; Pirrera, A.


    Some interesting challenges arise from the drive to build larger, more durable rotors that produce cheaper energy. The rationale is that, with current wind turbine designs, the power generated is theoretically proportional to the square of blade length. One enabling technology is aeroelastic tailoring that offers enhanced combined energy capture and system durability. The design of two adaptive, aeroelastically tailored blade configurations is considered here. One uses material bend-twist coupling; the other combines both material and geometric coupling. Each structural design meets a predefined coupling distribution, whilst approximately matching the stiffness of an uncoupled baseline blade. A gust analysis shows beneficial flapwise load alleviation for both adaptive blades, with the additional benefits of smoothing variations in electrical power and rotational speed.

  5. Nonlinear Gust Response Analysis of Free Flexible Aircraft

    Chen Shilu


    Full Text Available Gust response analysis plays a very important role in large aircraft design. This paper presents a methodology for calculating the flight dynamic characteristics and gust response of free flexible aircraft. A multidisciplinary coupled numerical tool is developed to simulate detailed aircraft models undergoing arbitrary free flight motion in the time domain, by Computational Fluid Dynamics (CFD, Computational Structure Dynamics (CSD and Computational Flight Mechanics (CFM coupling. To achieve this objective, a structured, time-accurate flow-solver is coupled with a computational module solving the flight mechanics equations of motion and a structural mechanics code determining the structural deformations. A novel method to determine the trim state of flexible aircraft is also stated. First, the field velocity approach is validated, after the trim state is attained, gust responses for the one-minus-cosine gust profile are analyzed for the longitudinal motion of a slender-wing aircraft configuration with and without the consideration of structural deformation.

  6. Characterization of vortical gusts produced by a heaving plate

    Hufstedler, Esteban; McKeon, Beverley J.


    To experimentally investigate the interaction between a wing and a spanwise vortical gust, a simple gust generator has been built and tested. This consists of a transversely heaving flat plate that changes direction to release a vortex, which then convects downstream to interact with a wing. Previous experiments have shown that, immediately downstream of the plate, the circulation of the generated vortex is proportional to the heaving speed of the plate. The forces that the gusts exert on a downstream wing were shown to be strongly repeatable and consistent with a passing vortex. This presentation will discuss the properties of the vortical gusts as they move downstream, and relate those properties to the important dimensionless parameters of the flow. These properties include the convection speed and circulation of the vortex, as well as the enstrophy due to the wake of the plate. This research is funded by the Gordon and Betty Moore Foundation through Grant GBMF#2645 to the California Institute of Technology.

  7. A probabilistic analysis of wind gusts using extreme value statistics

    Friederichs, Petra; Bentzien, Sabrina; Lenz, Anne; Krampitz, Rebekka [Meteorological Inst., Univ. of Bonn (Germany); Goeber, Martin [Deutscher Wetterdienst, Offenbach (Germany)


    The spatial variability of wind gusts is probably as large as that of precipitation, but the observational weather station network is much less dense. The lack of an area-wide observational analysis hampers the forecast verification of wind gust warnings. This article develops and compares several approaches to derive a probabilistic analysis of wind gusts for Germany. Such an analysis provides a probability that a wind gust exceeds a certain warning level. To that end we have 5 years of observations of hourly wind maxima at about 140 weather stations of the German weather service at our disposal. The approaches are based on linear statistical modeling using generalized linear models, extreme value theory and quantile regression. Warning level exceedance probabilities are estimated in response to predictor variables such as the observed mean wind or the operational analysis of the wind velocity at a height of 10 m above ground provided by the European Centre for Medium Range Weather Forecasts (ECMWF). The study shows that approaches that apply to the differences between the recorded wind gust and the mean wind perform better in terms of the Brier skill score (which measures the quality of a probability forecast) than those using the gust factor or the wind gusts only. The study points to the benefit from using extreme value theory as the most appropriate and theoretically consistent statistical model. The most informative predictors are the observed mean wind, but also the observed gust velocities recorded at the neighboring stations. Out of the predictors used from the ECMWF analysis, the wind velocity at 10 m above ground is the most informative predictor, whereas the wind shear and the vertical velocity provide no additional skill. For illustration the results for January 2007 and during the winter storm Kyrill are shown. (orig.)

  8. Dynamics of ultralight aircraft: Motion in vertical gusts

    Jones, R. T.


    Gust load calculations are extended to the range of conditions encountered by ultralight aircraft such as hang gliders. Having wing loadings of the order of 5 kg/sq m, these gliders acquire a substantial fraction of the motion of a gust within a distance of 1 or 2 m. Comparative loads and displacements for a small powered airplane having a wing loading of 50 kg sq m and for a commercial jet with 500 kg sq m are shown.

  9. Generation of vertical gusts in a transonic wind tunnel

    Brion, V.; Lepage, A.; Amosse, Y.; Soulevant, D.; Senecat, P.; Abart, J. C.; Paillart, P.


    This article reports on the qualification of a gust generator device in a transonic wind tunnel. A vanning apparatus has been installed in the contraction of the S3Ch transonic wind tunnel at the ONERA Meudon center in order to generate up and down air movements in the test section. The apparatus has been tested in a range of Strouhal number based on frequency and vane chord up to 0.15 and in a range of Mach number between 0.3 and 0.73. The amplitude of the gusts has been characterized by a fast-response two-hole pressure probe and phase-averaged PIV. The system delivers vertical velocity amplitude of 0.5 % of the freestream velocity at transonic speeds. For a constant vane oscillation angle, the gust strength is found to increase with the Strouhal and the Mach numbers. The gust exhibit a satisfying uniformity and a quasi-sinusoidal waveform. A simple dynamic point vortex model of the oscillating vanes and of the downstream wake has been developed in order to (1) compare the experimental results and (2) enrich the description of the flow induced by the gusts. In particular, the model is used to analyze the detrimental effect of the upper and lower walls. This simple unsteady model gives a valuable prediction of the amplitude of the gust obtained in the tunnel and the workable frequency range permitted by the present apparatus.

  10. A Bayesian hierarchical model for wind gust prediction

    Friederichs, Petra; Oesting, Marco; Schlather, Martin


    A postprocessing method for ensemble wind gust forecasts given by a mesoscale limited area numerical weather prediction (NWP) model is presented, which is based on extreme value theory. A process layer for the parameters of a generalized extreme value distribution (GEV) is introduced using a Bayesian hierarchical model (BHM). Incorporating the information of the COMSO-DE forecasts, the process parameters model the spatial response surfaces of the GEV parameters as Gaussian random fields. The spatial BHM provides area wide forecasts of wind gusts in terms of a conditional GEV. It models the marginal distribution of the spatial gust process and provides not only forecasts of the conditional GEV at locations without observations, but also uncertainty information about the estimates. A disadvantages of BHM model is that it assumes conditional independent observations. In order to incorporate the dependence between gusts at neighboring locations as well as the spatial random fields of observed and forecasted maximal wind gusts, we propose to model them jointly by a bivariate Brown-Resnick process.

  11. Evaluation of LRC Spectral Analyses of Simulated Gust Velocity Data

    Piersol, Allan G.


    The NASA Langley Research Center (LRC) has been computing power spectra of simulated atmospheric turbulence data by various techniques, in preparation for the B-57 gust velocity data analysis program. The results of these studies have confirmed earlier suspicions that conventional first-difference pre-whitening of gust velocity data can produce serious distortions in the spectral densities at very low frequencies (below the frequency of the gust velocity spectral "knee"). The results also indicate that the frequency averaging procedures have certain merits over ensemble averaging procedures in the computation of spectra by direct Fourier transform operations. Finally, the results do not reveal any significant difference in the spectral estimates obtained using Hann versus Parzen smoothing procedures.

  12. Dynamic decoupling nonlinear control method for aircraft gust alleviation

    Lv, Yang; Wan, Xiaopeng; Li, Aijun


    A dynamic decoupling nonlinear control method for MIMO system is presented in this paper. The dynamic inversion method is used to decouple the multivariable system. The nonlinear control method is used to overcome the poor decoupling effect when the system model is inaccurate. The nonlinear control method has correcting function and is expressed in analytic form, it is easy to adjust the parameters of the controller and optimize the design of the control system. The method is used to design vertical transition mode of active control aircraft for gust alleviation. Simulation results show that the designed vertical transition mode improves the gust alleviation effect about 34% comparing with the normal aircraft.

  13. Structure of Thunderstorm Gust Fronts with Topographic Effects


    Surface meteorological observations, associated with gust fronts produced by thunderstorm outflows over Tehran, an area surrounded by mountains, have been analyzed. Distinctive features are sudden drop in air temperature, up to 10℃, sharp increase in wind speed, up to 30 m s-1, with wind shift, to northwesterly, ressure jump, up to 4 hPa, humidity increase, up to 40%, and rain after some 20 min. Gust fronts which often occur in spring time, have a typical thickness of about 1.5 km and produce vertical wind shear of the order of 10-2s-1. Although these features seem to be common for most of the events, their intensities differ from one event to another, indicating that the gust fronts may occur in different sizes and shapes. Apart from a dominant effect on the formation of the original thunderstorms, topography appears to break up the frontal structure of the gust fronts. The internal Rossby radius of deformation for these flows is small enough (~ 100 km) for rotational effects to be minor.A laboratory model of the gust front (gravity current) also shows that it initially has a distinctive head with a turbulent wake, and can be broken up by topography. It is shown that when the environment is stratified, turbulence due to lobes and clefts instabilities near the nose of the current is suppressed. When the ground is rough, these instabilities are highly amplified and the internal Froude number of the flow is reduced. The bottom slope in the presence of rough topography leads to the break up of the current head and produces a broad and highly non-uniform head, recognized in the density signals.

  14. Wind Turbine Extreme Gust Control. Recognition and Control of extreme operation gusts and wind direction changes

    Kanev, S.K.; Van Engelen, T.G. [ECN Wind Energy, Petten (Netherlands)


    This report presents the research activities and achieved results on extreme event recognition (EER) and control (EEC). This work has been performed within the framework of WP3 of the SenterNovem project Sustainable Control (SusCon). An extreme wind gust with direction change can lead to large loads on the turbine (causing fatigue) and unnecessary turbine shut-downs by the supervisory system due to rotor overspeed. The proposed EER algorithm is based on a nonlinear observer (extended Kalman filter) that estimates the oblique wind inflow angle and the blade effective wind speed signals, which are then used by a detection algorithm (CUSUM test) to recognize extreme events. The nonlinear observer requires that blade root bending moments measurements (in-plane and out-of-plane) are available. Once an extreme event is detected, an EEC algorithm is activated that (1) tries to prevent the rotor speed from exceeding the overspeed limit by fast collective blade pitching, and (2) reduces 1p blade loads by means of individual pitch control algorithm, designed in an H1 optimal control setting. The method is demonstrated on a complex nonlinear test turbine model.

  15. Gust Load Alleviation with Robust Control for a Flexible Wing

    Xiang Liu


    Full Text Available Traditional methods for gust alleviation of aircraft are mostly proposed based on a specific flight condition. In this paper, robust control laws are designed for a large flexible wing with uncertainty in Mach number and dynamic pressure. To accurately describe the aeroelastic model over a large flight envelope, a nonlinear parameter-varying model is developed which is a function of both Mach number and dynamic pressure. Then a linear fractional transformation is established accordingly and a modified model order reduction technique is applied to reduce the size of the uncertainty block. The developed model, in which the statistic nature of the gust is considered by using the Dryden power spectral density function, enables the use of μ-synthesis procedures for controller design. The simulations show that the μ controller can always effectively reduce the wing root shear force and bending moment at a given range of Mach number and dynamic pressure.

  16. Wind Turbine Gust Prediction Using Remote Sensing Data

    Towers, Paul; Jones, Bryn


    Offshore wind energy is a growing energy source as governments around the world look for environmentally friendly solutions to potential future energy shortages. In order to capture more energy from the wind, larger turbines are being designed, leading to the structures becoming increasingly vulnerable to damage caused by violent gusts of wind. Advance knowledge of such gusts will enable turbine control systems to take preventative action, reducing turbine maintenance costs. We present a system which can accurately forecast the velocity profile of an oncoming wind, given only limited spatial measurements from light detection and ranging (LiDAR) units, which are currently operational in industry. Our method combines nonlinear state estimation techniques with low-order models of atmospheric boundary-layer flows to generate flow-field estimates. We discuss the accuracy of our velocity profile predictions by direct comparison to data derived from large eddy simulations of the atmospheric boundary layer.

  17. Two Empirical Models for Land-falling Hurricane Gust Factors

    Merceret, Franics J.


    Gaussian and lognormal models for gust factors as a function of height and mean windspeed in land-falling hurricanes are presented. The models were empirically derived using data from 2004 hurricanes Frances and Jeanne and independently verified using data from 2005 hurricane Wilma. The data were collected from three wind towers at Kennedy Space Center and Cape Canaveral Air Force Station with instrumentation at multiple levels from 12 to 500 feet above ground level. An additional 200-foot tower was available for the verification. Mean wind speeds from 15 to 60 knots were included in the data. The models provide formulas for the mean and standard deviation of the gust factor given the mean windspeed and height above ground. These statistics may then be used to assess the probability of exceeding a specified peak wind threshold of operational significance given a specified mean wind speed.

  18. Developing an Accurate CFD Based Gust Model for the Truss Braced Wing Aircraft

    Bartels, Robert E.


    The increased flexibility of long endurance aircraft having high aspect ratio wings necessitates attention to gust response and perhaps the incorporation of gust load alleviation. The design of civil transport aircraft with a strut or truss-braced high aspect ratio wing furthermore requires gust response analysis in the transonic cruise range. This requirement motivates the use of high fidelity nonlinear computational fluid dynamics (CFD) for gust response analysis. This paper presents the development of a CFD based gust model for the truss braced wing aircraft. A sharp-edged gust provides the gust system identification. The result of the system identification is several thousand time steps of instantaneous pressure coefficients over the entire vehicle. This data is filtered and downsampled to provide the snapshot data set from which a reduced order model is developed. A stochastic singular value decomposition algorithm is used to obtain a proper orthogonal decomposition (POD). The POD model is combined with a convolution integral to predict the time varying pressure coefficient distribution due to a novel gust profile. Finally the unsteady surface pressure response of the truss braced wing vehicle to a one-minus-cosine gust, simulated using the reduced order model, is compared with the full CFD.

  19. Wind and thermodynamic profiler observations of a late-mature gust front

    Haldun Karan


    High temporal and vertical resolutions of kinematic and thermodynamic characteristics of a late-mature gust front are presented using the Mobile Integrated Profiling System andWeather Surveillance Radar 88 Doppler data. As the gust front passed over the Mobile Integrated Profiling System vertical velocities and the horizontal wind field with 1 and 1.5 min temporal resolutions, respectively, were sampled within the gust front updrafts, gust frontal head and body structures. A 12-channel microwave profiling radiometer was used to delineate the thermodynamic properties with 5–6 min temporal and 100 m vertical resolution. Lidar backscatter from the 0.906 m ceilometer was also used to demonstrate the cloud field and the gust front depth. The gust front structurally and dynamically resembled laboratory simulated density current, and was composed of an elevated forward protrusion of a nose, and a turbulent mixing region at the top behind the head. The updrafts associated with the gust front that was moving into a stable layer were not surface rooted. Rather, the updrafts less than 3.5 ms−1 were observed 500 m above ground level during the gust front passage. These updrafts were present from above the nose level to top of the head. The observations indicated that kinematic and thermodynamic characteristics of the atmospheric boundary layer significantly influenced the propagation speed, updraft characteristics, and overall structural organization of the gust front. The observations validated that observed propagation speed of the gust front was in close agreement with the calculated propagation speed by integrating the buoyancy term within the gust front depth.

  20. Data Mining Methods to Generate Severe Wind Gust Models

    Subana Shanmuganathan


    Full Text Available Gaining knowledge on weather patterns, trends and the influence of their extremes on various crop production yields and quality continues to be a quest by scientists, agriculturists, and managers. Precise and timely information aids decision-making, which is widely accepted as intrinsically necessary for increased production and improved quality. Studies in this research domain, especially those related to data mining and interpretation are being carried out by the authors and their colleagues. Some of this work that relates to data definition, description, analysis, and modelling is described in this paper. This includes studies that have evaluated extreme dry/wet weather events against reported yield at different scales in general. They indicate the effects of weather extremes such as prolonged high temperatures, heavy rainfall, and severe wind gusts. Occurrences of these events are among the main weather extremes that impact on many crops worldwide. Wind gusts are difficult to anticipate due to their rapid manifestation and yet can have catastrophic effects on crops and buildings. This paper examines the use of data mining methods to reveal patterns in the weather conditions, such as time of the day, month of the year, wind direction, speed, and severity using a data set from a single location. Case study data is used to provide examples of how the methods used can elicit meaningful information and depict it in a fashion usable for management decision making. Historical weather data acquired between 2008 and 2012 has been used for this study from telemetry devices installed in a vineyard in the north of New Zealand. The results show that using data mining techniques and the local weather conditions, such as relative pressure, temperature, wind direction and speed recorded at irregular intervals, can produce new knowledge relating to wind gust patterns for vineyard management decision making.

  1. Gust prediction via artificial hair sensor array and neural network

    Pankonien, Alexander M.; Thapa Magar, Kaman S.; Beblo, Richard V.; Reich, Gregory W.


    Gust Load Alleviation (GLA) is an important aspect of flight dynamics and control that reduces structural loadings and enhances ride quality. In conventional GLA systems, the structural response to aerodynamic excitation informs the control scheme. A phase lag, imposed by inertia, between the excitation and the measurement inherently limits the effectiveness of these systems. Hence, direct measurement of the aerodynamic loading can eliminate this lag, providing valuable information for effective GLA system design. Distributed arrays of Artificial Hair Sensors (AHS) are ideal for surface flow measurements that can be used to predict other necessary parameters such as aerodynamic forces, moments, and turbulence. In previous work, the spatially distributed surface flow velocities obtained from an array of artificial hair sensors using a Single-State (or feedforward) Neural Network were found to be effective in estimating the steady aerodynamic parameters such as air speed, angle of attack, lift and moment coefficient. This paper extends the investigation of the same configuration to unsteady force and moment estimation, which is important for active GLA control design. Implementing a Recurrent Neural Network that includes previous-timestep sensor information, the hair sensor array is shown to be capable of capturing gust disturbances with a wide range of periods, reducing predictive error in lift and moment by 68% and 52% respectively. The L2 norms of the first layer of the weight matrices were compared showing a 23% emphasis on prior versus current information. The Recurrent architecture also improves robustness, exhibiting only a 30% increase in predictive error when undertrained as compared to a 170% increase by the Single-State NN. This diverse, localized information can thus be directly implemented into a control scheme that alleviates the gusts without waiting for a structural response or requiring user-intensive sensor calibration.

  2. Automatic Carrier Landing System with Gust-rejection Capability

    曹东; 杨一栋; 余勇; 范彦铭


    A new direct-lift control carrier landing mode is advanced, and it is proved to be very effective to keep the attitude angle and path angle constant when the aircraft is in the blind area of tracking radar and the guidance system is shut off. The direct-lift control mode is achieved with the symmetric deflection of the flaps and dynamic decoupling for minor disturbance of the angle of attack. This mode changes an aircraft' s model from a short-period oscillation model to a non-oscillation one, which could evidently increase the gust-rejection capability of the aircraft.

  3. Active gust load alleviation system for flexible aircraft: Mixed feedforward/feedback approach

    Alam, Mushfiqul; Hromcik, Martin; Hanis, Tomas


    Lightweight flexible blended-wing-body (BWB) aircraft concept seems as a highly promising configuration for future high capacity airliners which suffers from reduced stiffness for disturbance loads such as gusts. A robust feedforward gust load alleviation system (GLAS) was developed to alleviate ...

  4. Development, Verification and Use of Gust Modeling in the NASA Computational Fluid Dynamics Code FUN3D

    Bartels, Robert E.


    This paper presents the implementation of gust modeling capability in the CFD code FUN3D. The gust capability is verified by computing the response of an airfoil to a sharp edged gust. This result is compared with the theoretical result. The present simulations will be compared with other CFD gust simulations. This paper also serves as a users manual for FUN3D gust analyses using a variety of gust profiles. Finally, the development of an Auto-Regressive Moving-Average (ARMA) reduced order gust model using a gust with a Gaussian profile in the FUN3D code is presented. ARMA simulated results of a sequence of one-minus-cosine gusts is shown to compare well with the same gust profile computed with FUN3D. Proper Orthogonal Decomposition (POD) is combined with the ARMA modeling technique to predict the time varying pressure coefficient increment distribution due to a novel gust profile. The aeroelastic response of a pitch/plunge airfoil to a gust environment is computed with a reduced order model, and compared with a direct simulation of the system in the FUN3D code. The two results are found to agree very well.

  5. Gust alleviation of highly flexible UAVs with artificial hair sensors

    Su, Weihua; Reich, Gregory W.


    Artificial hair sensors (AHS) have been recently developed in Air Force Research Laboratory (AFRL) using carbon nanotube (CNT). The deformation of CNT in air flow causes voltage and current changes in the circuit, which can be used to quantify the dynamic pressure and aerodynamic load along the wing surface. AFRL has done a lot of essential work in design, manufacturing, and measurement of AHSs. The work in this paper is to bridge the current AFRL's work on AHSs and their feasible applications in flight dynamics and control (e.g., the gust alleviation) of highly flexible aircraft. A highly flexible vehicle is modeled using a strain-based geometrically nonlinear beam formulation, coupled with finite-state inflow aerodynamics. A feedback control algorithm for the rejection of gust perturbations will be developed. A simplified Linear Quadratic Regulator (LQR) controller will be implemented based on the state-space representation of the linearized system. All AHS measurements will be used as the control input, i.e., wing sectional aerodynamic loads will be defined as the control output for designing the feedback gain. Once the controller is designed, closed-loop aeroelastic simulations will be performed to evaluate the performance of different controllers with the force feedback and be compared to traditional controller designs with the state feedback. From the study, the feasibility of AHSs in flight control will be assessed. The whole study will facilitate in building a fly-by-feel simulation environment for autonomous vehicles.

  6. Aeroelastic scaling laws for gust load alleviation control system

    Tang Bo; Wu Zhigang; Yang Chao


    Gust load alleviation (GLA) tests are widely conducted to study the effectiveness of the control laws and methods. The physical parameters of models in these tests are aeroelastic scaled, while the scaling of GLA control system is always unreached. This paper concentrates on studying the scaling laws of GLA control system. Through theoretical demonstration, the scaling criterion of a classical PID control system has been come up and a scaling methodology is provided and veri-fied. By adopting the scaling laws in this paper, gust response of the scaled model could be directly related to the full-scale aircraft theoretically under both open-loop and closed-loop conditions. Also, the influences of different scaling choices of an important non-dimensional parameter, the Froude number, have been studied in this paper. Furthermore for practical application, a compen-sating method is given when the theoretical scaled actuators or sensors cannot be obtained. Also, the scaling laws of some non-linear elements in control system such as the rate and amplitude sat-urations in actuator have been studied and examined by a numerical simulation.

  7. Aeroelastic scaling laws for gust load alleviation control system

    Tang Bo


    Full Text Available Gust load alleviation (GLA tests are widely conducted to study the effectiveness of the control laws and methods. The physical parameters of models in these tests are aeroelastic scaled, while the scaling of GLA control system is always unreached. This paper concentrates on studying the scaling laws of GLA control system. Through theoretical demonstration, the scaling criterion of a classical PID control system has been come up and a scaling methodology is provided and verified. By adopting the scaling laws in this paper, gust response of the scaled model could be directly related to the full-scale aircraft theoretically under both open-loop and closed-loop conditions. Also, the influences of different scaling choices of an important non-dimensional parameter, the Froude number, have been studied in this paper. Furthermore for practical application, a compensating method is given when the theoretical scaled actuators or sensors cannot be obtained. Also, the scaling laws of some non-linear elements in control system such as the rate and amplitude saturations in actuator have been studied and examined by a numerical simulation.

  8. Gaussian and Lognormal Models of Hurricane Gust Factors

    Merceret, Frank


    A document describes a tool that predicts the likelihood of land-falling tropical storms and hurricanes exceeding specified peak speeds, given the mean wind speed at various heights of up to 500 feet (150 meters) above ground level. Empirical models to calculate mean and standard deviation of the gust factor as a function of height and mean wind speed were developed in Excel based on data from previous hurricanes. Separate models were developed for Gaussian and offset lognormal distributions for the gust factor. Rather than forecasting a single, specific peak wind speed, this tool provides a probability of exceeding a specified value. This probability is provided as a function of height, allowing it to be applied at a height appropriate for tall structures. The user inputs the mean wind speed, height, and operational threshold. The tool produces the probability from each model that the given threshold will be exceeded. This application does have its limits. They were tested only in tropical storm conditions associated with the periphery of hurricanes. Winds of similar speed produced by non-tropical system may have different turbulence dynamics and stability, which may change those winds statistical characteristics. These models were developed along the Central Florida seacoast, and their results may not accurately extrapolate to inland areas, or even to coastal sites that are different from those used to build the models. Although this tool cannot be generalized for use in different environments, its methodology could be applied to those locations to develop a similar tool tuned to local conditions.

  9. Gust factor based on research aircraft measurements: A new methodology applied to the Arctic marine boundary layer

    Suomi, Irene; Lüpkes, Christof; Hartmann, Jörg


    There is as yet no standard methodology for measuring wind gusts from a moving platform. To address this, we have developed a method to derive gusts from research aircraft data. First we evaluated four different approaches, including Taylor's hypothesis of frozen turbulence, to derive the gust...... in unstable conditions (R2=0.52). The mean errors for all methods were low, from -0.02 to 0.05, indicating that wind gust factors can indeed be measured from research aircraft. Moreover, we showed that aircraft can provide gust measurements within the whole boundary layer, if horizontal legs are flown...

  10. Benchmark Solution For The Category 3, Problem 2: Cascade - Gust Interaction

    Envia, Edmane


    The benchmark solution for the cascade-gust interaction problem is computed using a linearized Euler code called LINFLUX. The inherently three-dimensional code is run in the thin-annulus limit to compute the two-dimensional cascade response. The calculations are carried out in the frequency-domain and the unsteady response at each of the gust s three frequency component is computed. The results are presented on modal basis for pressure perturbations (i.e., acoustic modes) as well as velocity perturbations (i.e., convected gust modes) at each frequency.

  11. Influence of wind gusts in power quality on wind farms

    Gonzalo Guerrón


    Full Text Available (Received: 2014/04/30 - Accepted: 2014/09/22World energy matrix is changing due to the increase of energy consumption in the last years. Installation of unconventional renewable energy plants in many countries has become a solution to this event. Integration of this type of energy to the electric network causes interest in the study of phenomena that affects energy production. This document is a review of concepts and events occurring on energy quality and how they interact in a wind farm. The efficiency of wind turbines is affected by many factors, the most outstanding are: substations activities and weather issues such as wind gusts, which causes variations in the power curve. Constant monitoring on electric systems and data processing offers a high potential in improving the process of production and distribution of energy.

  12. Gust response analysis and wind tunnel test for a high-aspect ratio wing

    Liu Yi


    Full Text Available A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisciplinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter boundary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quantitative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flexible wings.

  13. nowCOAST's Map Service for NOAA NWS NDFD Gridded Forecasts of Surface Wind Gust (knots)

    National Oceanic and Atmospheric Administration, Department of Commerce — Map Information: This nowCOAST time-offsets map service provides maps depicting the NWS surface wind gust forecasts from the National Digital Forecast Database...

  14. Predictive Gust Load Alleviation Control Using Leading Edge Stagnation Point Sensor Project

    National Aeronautics and Space Administration — ZONA Technology, Inc proposes an R&D effort to develop a Gust Load Alleviation (GLA) control system using a novel Leading Edge Stagnation Point (LESP) sensor...

  15. Variation of the low level winds during the passage of a thunderstorm gust front

    Sinclair, R. W.; Anthes, R. A.; Panofsky, H. A.


    Three time histories of wind profiles in thunderstorm gust fronts at Cape Kennedy and three at Oklahoma City are analyzed. Wind profiles at maximum wind strength below 100 m follow logarithmic laws, so that winds above the surface layer can be estimated from surface winds once the roughness length is known. A statistical analysis of 81 cases of surface winds during thunderstorms at Tampa revealed no predictor with skill to predict the time of maximum gust. Some 34% of the variance of the strength of the gust is accounted for by a stability index and surface wind prior to the gust; the regression equations for these variables are given. The coherence between microscale wind speed variations at the different levels has the same proportions as in non-thunderstorm cases.

  16. Wind gust estimation for Mid-European winter storms: towards a probabilistic view

    Kai Born


    Full Text Available Three wind gust estimation (WGE methods implemented in the numerical weather prediction (NWP model COSMO-CLM are evaluated with respect to their forecast quality using skill scores. Two methods estimate gusts locally from mean wind speed and the turbulence state of the atmosphere, while the third one considers the mixing-down of high momentum within the planetary boundary layer (WGE Brasseur. One hundred and fifty-eight windstorms from the last four decades are simulated and results are compared with gust observations at 37 stations in Germany. Skill scores reveal that the local WGE methods show an overall better behaviour, whilst WGE Brasseur performs less well except for mountain regions. The here introduced WGE turbulent kinetic energy (TKE permits a probabilistic interpretation using statistical characteristics of gusts at observational sites for an assessment of uncertainty. The WGE TKE formulation has the advantage of a ‘native’ interpretation of wind gusts as result of local appearance of TKE. The inclusion of a probabilistic WGE TKE approach in NWP models has, thus, several advantages over other methods, as it has the potential for an estimation of uncertainties of gusts at observational sites.

  17. Gust Acoustic Response of a Single Airfoil Using the Space-Time CE/SE Method

    Scott, James (Technical Monitor); Wang, X. Y.; Chang, S. C.; Himansu, A.; Jorgenson, P. C. E.


    A 2D parallel Euler code based on the space-time conservation element and solution element (CE/SE) method is validated by solving the benchmark problem I in Category 3 of the Third CAA Workshop. This problem concerns the acoustic field generated by the interaction of a convected harmonic vortical gust with a single airfoil. Three gust frequencies, two gust configurations, and three airfoil geometries are considered. Numerical results at both near and far fields are presented and compared with the analytical solutions, a frequency-domain solver GUST3D solutions, and a time-domain high-order Discontinuous Spectral Element Method (DSEM) solutions. It is shown that the CE/SE solutions agree well with the GUST3D solution for the lowest frequency, while there are discrepancies between CE/SE and GUST3D solutions for higher frequencies. However, the CE/SE solution is in good agreement with the DSEM solution for these higher frequencies. It demonstrates that the CE/SE method can produce accurate results of CAA problems involving complex geometries by using unstructured meshes.

  18. Gust response modeling and alleviation scheme design for an elastic aircraft


    Time-domain approaches are presented for analysis of the dynamic response of aeroservoelastic systems to atmospheric gust excitations. The continuous and discrete gust inputs are defined in the time domain. The time-domain approach to continuous gust response uses a state-space formulation that requires the frequency-dependent aerodynamic coefficients to be approximated with the rational function of a Laplace variable. A hybrid method which combines the Fourier transform and time-domain approaches is used to calculate discrete gust response. The purpose of this approach is to obtain a time-domain state-space model without using rational function approximation of the gust columns. Three control schemes are designed for gust alleviation on an elastic aircraft, and three control surfaces are used: aileron, elevator and spoiler. The signals from the rate of pitch angle gyroscope or angle of attack sensor are sent to the elevator while the signals from accelerometers at the wing tip and center of gravity of the aircraft are sent to the aileron and spoiler, respectively. All the control laws are based on classical control theory. The results show that acceleration at the center of gravity of the aircraft and bending-moment at the wing-root section are mainly excited by rigid modes of the aircraft and the accelerations at the wing-tip are mainly excited by elastic modes of the aircraft. All the three control schemes can be used to alleviate the wing-root moments and the accelerations. The gust response can be alleviated using control scheme 3, in which the spoiler is used as a control surface, but the effects are not as good as those of control schemes 1 and 2.

  19. Effect of gust on force generation around a robotic hummingbird wing

    Marquez, Eloy; Tian, Ruijun; Shu, Fangjun


    Among the computational, theoretical and experimental studies on the high efficiency flapping flight, many are focused on the mystery of hovering. Most of these studies were conducted under steady in flow conditions. However, real-life ornithopters in the field have to routinely tackle gust and directional changes of the wind. These sudden perturbations could produce significant effect on humming bird hovering due to the small Reynolds numbers. Our experimental work was performed in a water channel using a two degree-of-freedom humming bird model. The dynamic response of the hovering motion to gust from different directions was investigated. PIV was used to measure the effect of the gust on the surrounding flow field including vortex evolution. In addition, a six-component force/torque sensor was used to measure the real-time lift and drag forces generated by the wing with and without gust. Results show that gust changes the magnitude of lift force in one stroke. However, the time-averaged lift force keeps approximately constant. Supported by Army High Performance Computing Center.

  20. Gusts and Shear Within Hurricane Eyewalls Can Exceed Offshore Wind-Turbine Design Standards

    Worsnop, Rochelle P; Bryan, George H; Damiani, Rick; Musial, Walt


    Offshore wind energy development is underway in the U.S., with proposed sites located in hurricane-prone regions. Turbine design criteria outlined by the International Electrotechnical Commission do not encompass the extreme wind speeds and directional shifts of hurricanes stronger than a Category 2. We examine the most turbulent portion of a hurricane (the eyewall) using large-eddy simulations with Cloud Model 1 (CM1). Gusts and mean wind speeds near the eyewall exceed the current design threshold of 50 m s-1 mean wind and 70 m s-1 gusts for Class I turbines. Gust factors are greatest at the eye-eyewall interface. Further, shifts in wind direction at wind turbine hub height suggest turbines must rotate into the wind faster than current practice. Although current design standards omit mention of wind direction change across the rotor layer, large values (15-50 deg) suggest that veer should be considered in design standards.

  1. Gusts and shear within hurricane eyewalls can exceed offshore wind turbine design standards

    Worsnop, Rochelle P.; Lundquist, Julie K.; Bryan, George H.; Damiani, Rick; Musial, Walt


    Offshore wind energy development is underway in the U.S., with proposed sites located in hurricane-prone regions. Turbine design criteria outlined by the International Electrotechnical Commission do not encompass the extreme wind speeds and directional shifts of hurricanes stronger than category 2. We examine a hurricane's turbulent eyewall using large-eddy simulations with Cloud Model 1. Gusts and mean wind speeds near the eyewall of a category 5 hurricane exceed the current Class I turbine design threshold of 50 m s-1 mean wind and 70 m s-1 gusts. Largest gust factors occur at the eye-eyewall interface. Further, shifts in wind direction suggest that turbines must rotate or yaw faster than current practice. Although current design standards omit mention of wind direction change across the rotor layer, large values (15-50°) suggest that veer should be considered.

  2. Optimality study of a gust alleviation system for light wing-loading STOL aircraft

    Komoda, M.


    An analytical study was made of an optimal gust alleviation system that employs a vertical gust sensor mounted forward of an aircraft's center of gravity. Frequency domain optimization techniques were employed to synthesize the optimal filters that process the corrective signals to the flaps and elevator actuators. Special attention was given to evaluating the effectiveness of lead time, that is, the time by which relative wind sensor information should lead the actual encounter of the gust. The resulting filter is expressed as an implicit function of the prescribed control cost. A numerical example for a light wing loading STOL aircraft is included in which the optimal trade-off between performance and control cost is systematically studied.

  3. Gust Acoustics Computation with a Space-Time CE/SE Parallel 3D Solver

    Wang, X. Y.; Himansu, A.; Chang, S. C.; Jorgenson, P. C. E.; Reddy, D. R. (Technical Monitor)


    The benchmark Problem 2 in Category 3 of the Third Computational Aero-Acoustics (CAA) Workshop is solved using the space-time conservation element and solution element (CE/SE) method. This problem concerns the unsteady response of an isolated finite-span swept flat-plate airfoil bounded by two parallel walls to an incident gust. The acoustic field generated by the interaction of the gust with the flat-plate airfoil is computed by solving the 3D (three-dimensional) Euler equations in the time domain using a parallel version of a 3D CE/SE solver. The effect of the gust orientation on the far-field directivity is studied. Numerical solutions are presented and compared with analytical solutions, showing a reasonable agreement.

  4. Gust load alleviation wind tunnel tests of a large-aspect-ratio flexible wing with piezoelectric control

    Ying Bi


    Full Text Available An active control technique utilizing piezoelectric actuators to alleviate gust-response loads of a large-aspect-ratio flexible wing is investigated. Piezoelectric materials have been extensively used for active vibration control of engineering structures. In this paper, piezoelectric materials further attempt to suppress the vibration of the aeroelastic wing caused by gust. The motion equation of the flexible wing with piezoelectric patches is obtained by Hamilton’s principle with the modal approach, and then numerical gust responses are analyzed, based on which a gust load alleviation (GLA control system is proposed. The gust load alleviation system employs classic proportional-integral-derivative (PID controllers which treat piezoelectric patches as control actuators and acceleration as the feedback signal. By a numerical method, the control mechanism that piezoelectric actuators can be used to alleviate gust-response loads is also analyzed qualitatively. Furthermore, through low-speed wind tunnel tests, the effectiveness of the gust load alleviation active control technology is validated. The test results agree well with the numerical results. Test results show that at a certain frequency range, the control scheme can effectively alleviate the z and x wingtip accelerations and the root bending moment of the wing to a certain extent. The control system gives satisfying gust load alleviation efficacy with the reduction rate being generally over 20%.

  5. Gust response analysis and wind tunnel test for a high-aspect ratio wing

    Liu Yi; Xie Changchuan; Yang Chao; Cheng Jialin


    A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisci-plinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter bound-ary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quanti-tative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flex-ible wings.

  6. Claustre Obert: 'El gust de llegir i el plaer d'escriure (en temps de canvis)'

    Serveis Audiovisuals Universitat de València


    Debat 'El gust de llegir i el plaer d'escriure (en temps de canvis)' amb l'escriptora Isabel Clara Simó, debat inclòs a l'espai 'Claustre Obert' en el Centre Cultural La Nau i en el qual es va presentar la nova Aula de Lectura i Escriptura de la Universitat de València.

  7. Measurements and Analysis of the Motion of a Canard Airplane Model in Gusts


    ation. An adverso pitching motion may arise to increaso further the acceleration increment. It is therefore felt that these factors should be taken...referred to o.,g. of model) Figure 6.- History of evento the 3.7-foot gust gradient. in Figure 7.- History of evente in :: the 8.2-f oot guBt gradient

  8. Unified aerodynamic-acoustic theory for a thin rectangular wing encountering a gust

    Martinez, R.; Widnall, S. E.


    A linear aerodynamic-acoustic theory is developed for the prediction of the surface pressure distribution and three-dimensional acoustic far-field for a flat plate rectangular wing encountering a stationary short-wavelength oblique gust. It is suggested that for an infinite-span wing, leading- and trailing-edge responses to a short-wavelength gust are essentially independent. This idea is used to solve for the two-dimensional pressure field due to the passage of an infinite-span wing through an oblique gust. By allowing the field point to come down to the wing's surface, one finds an expression for the surface pressure distribution which agrees with that given in the two-dimensional aerodynamic theories of Amiet and Adamczyk. Spanwise Fourier superposition of two-dimensional solutions to the infinite-span wing problem is used to approximate the three-dimensional acoustic field due to the interaction of a stationary oblique gust with a flat-plate rectangular wing traveling at a subsonic speed.

  9. Maximized Gust Loads of a Closed-Loop, Nonlinear Aeroelastic System Using Nonlinear Systems Theory

    Silva, Walter A.


    The problem of computing the maximized gust load for a nonlinear, closed-loop aeroelastic aircraft is discusses. The Volterra theory of nonlinear systems is applied in order to define a linearized system that provides a bounds on the response of the nonlinear system of interest. The method is applied to a simplified model of an Airbus A310.

  10. 78 FR 31851 - Harmonization of Airworthiness Standards-Gust and Maneuver Load Requirements


    ... turbulence design loads criteria; revise the application of gust loads to engine mounts, high lift devices.... 25.362) We propose to revise the engine loads design requirements for engine mounts, auxiliary power unit mounts, engine pylons, and adjacent supporting airframe structures. The proposed amendment...

  11. GPC-Based Gust Response Alleviation for Aircraft Model Adapting to Various Flow Velocities in the Wind Tunnel

    Yuting Dai


    Full Text Available A unified autoregressive (AR model is identified, based on the wind tunnel test data of open-loop gust response for an aircraft model. The identified AR model can be adapted to various flow velocities in the wind tunnel test. Due to the lack of discrete gust input measurement, a second-order polynomial function is used to approximate the gust input amplitude by flow velocity. Afterwards, with the identified online aeroelastic model, the modified generalized predictive control (GPC theory is applied to alleviate wing tip acceleration induced by sinusoidal gust. Finally, the alleviation effects of gust response at different flow velocities are estimated based on the comparison of simulated closed-loop acceleration with experimental open-loop one. The comparison indicates that, after gust response alleviation, the wing tip acceleration can be reduced up to 20% at the tested velocities ranging from 12 m/s to 24 m/s. Demonstratively, the unified control law can be adapted to varying wind tunnel velocities and gust frequencies. It does not need to be altered at different test conditions, which will save the idle time.

  12. Considerations about gust wind thresholds related to social impact: study of different regions in Catalonia

    Barberia, Laura; Amaro, Jéssica; Aran, Montserrat; Llasat, Maria del Carmen


    Severe weather events can cause several damages on a territory and its population, affecting urban infrastructure and housing, among others. In particular, wind is one of the most important phenomena which cause remarkable economic losses. Since 2008, different studies conducted by the Social Impact Research Group, in the frame of HYMEX project, determined that requests related to damage claims which are received in Meteorological Services are a good proxy indicator of social impact. However, the strong wind studies took into account a unique threshold, which proved to be insufficient. It was found that it was necessary to define a threshold for each area, according to its vulnerability and exposure. Therefore, the aim of this study is to define, for each county in Catalonia, thresholds of gust wind speed for which a remarkable social impact is observed. To accomplish this, the database of requests received in the Meteorological Service of Catalonia (SMC) between 2011 and 2015 has been used. For each request, the most representative automatic weather stations are associated. Statistical treatments of the gust wind data recorded by these stations have been carried out in order to determine which values are related to social impact. As an example, one of the first results shows that in a populated area like Barcelona, the average gust is approximately 70 km/h. On the contrary, in other less populated counties and usually more exposed to strong winds, the mean is over 85 km/h. Besides, the relation between gusts and requests has been analyzed to detect significant slope changes. In general, it has been detected an increase of requests at certain gust wind values. These results, which vary depending on the region's vulnerability and exposure, could be used to establish new thresholds for Civil Protection alarms. Therefore, a higher accuracy by region will be reached.

  13. Gusts detection in a horizontal wind turbine by monitoring of innovations error of an extended Kalman filter

    Recalde, L. F.; Hur, S.; Leithead, W. E.


    This paper presents a novel model-based detection scheme capable of detecting and diagnosing gusts. Detection is achieved by monitoring the innovations error (i.e., the difference between the estimated and measured outputs) of an extended discrete Kalman filter. It is designed to trigger a detection/confirmation alarm in the presence of wind anomalies. Simulation results are presented to demonstrate that both operating and coherent extreme wind gusts can successfully be detected. The wind anomaly is identified in magnitude and shape through maximum likelihood ratio and goodness of fit, respectively. The detector is capable of isolating extreme wind gusts before the turbine over speeds.

  14. Experimental investigation of a vibrating axial turbine cascade in presence of upstream generated aerodynamic gusts

    Rottmeier, Fabrice; Bölcs, Albin


    An experimental investigation has been conducted in the non-rotating annular test facility of the "Laboratoire de Thermique Appliquée et de Turbomachines" (LTT), "École Polytechnique Fédérale de Lausanne" (EPFL). During this investigation, the unsteady aerodynamic response of a turbine cascade was investigated for three different cases: (1) the clamped blades subjected to periodic, upstream generated aerodynamic gusts, (2) the cascade forced to vibrate in the travelling wave mode in a uniform...

  15. Experimental investigation of a vibrating axial turbine cascade in presence of upstream generated aerodynamic gusts

    Rottmeier, Fabrice


    An experimental investigation has been conducted in the non-rotating annular test facility of the "Laboratoire de Thermique Appliquée et de Turbomachines" (LTT), "École Polytechnique Fédérale de Lausanne" (EPFL). During this investigation, the unsteady aerodynamic response of a turbine cascade was investigated for three different cases: (1) the clamped blades subjected to periodic, upstream generated aerodynamic gusts, (2) the cascade forced to vibrate in the travelling wave mode in a uniform...

  16. Exploration of plasma-based control for low-Reynolds number airfoil/gust interaction

    Rizzetta, Donald P.; Visbal, Miguel R.


    Large-eddy simulation (LES) is employed to investigate the use of plasma-based actuation for the control of a vortical gust interacting with a wing section at a low Reynolds number. Flow about the SD7003 airfoil section at 4° angle of attack and a chord-based Reynolds number of 60,000 is considered in the simulation, which typifies micro air vehicle (MAV) applications. Solutions are obtained to the Navier-Stokes equations that were augmented by source terms used to represent body forces imparted by the plasma actuator on the fluid. A simple phenomenological model provided these body forces resulting from the electric field generated by the plasma. The numerical method is based upon a high-fidelity time-implicit scheme and an implicit LES approach which are used to obtain solutions on a locally refined overset mesh system. A Taylor-like vortex model is employed to represent a gust impinging upon the wing surface, which causes a substantial disruption to the undisturbed flow. It is shown that the fundamental impact of the gust on unsteady aerodynamic forces is due to an inviscid process, corresponding to variation in the effective angle of attack, which is not easily overcome. Plasma control is utilised to mitigate adverse effects of the interaction and improve aerodynamic performance. Physical characteristics of the interaction are described, and several aspects of the control strategy are explored. Among these are uniform and non-uniform spanwise variations of the control configuration, co-flow and counter-flow orientations of the directed force, pulsed and continuous operations of the actuator and strength of the plasma field. Results of the control situations are compared with regard to their effect upon aerodynamic forces. It was found that disturbances to the moment coefficient produced by the gust can be greatly reduced, which may be significant for stability and handling of MAV operations.

  17. Integrated Flight Mechanic and Aeroelastic Modelling and Control of a Flexible Aircraft Considering Multidimensional Gust Input


    INTEGRATED FLIGHT MECHANIC AND AEROELASTIC MODELLING AND CONTROL OF A FLEXIBLE AIRCRAFT CONSIDERING MULTIDIMENSIONAL GUST INPUT Patrick Teufel, Martin Hanel...the lateral separation distance have been developed by ’ = matrix of two dimensional spectrum function Eichenbaum 4 and are described by Bessel...Journal of Aircraft, Vol. 30, No. 5, Sept.-Oct. 1993 Relations to Risk Sensitivity, System & Control Letters 11, [4] Eichenbaum F.D., Evaluation of 3D

  18. Experimental investigation of a large aspect ratio flat plate encountering a steam-wise gust

    Mulleners, Karen; Mancini, Peter; Jones, Anya


    While humans are capable of mimicking, and even outperform, the kinematic capabilities of natural flyers, birds and insects are still way ahead of us when it comes to anticipating and dealing with turbulent and gusty flow conditions. To tailor and improve flight control capabilities of low Reynolds number flyers in real weather, we need to bridge this gap of knowledge. As a first step, we experimentally studied the aerodynamic influence of a simplified stream-wise gust on a large aspect ratio flat plate. The experiments were conduction in the 7 × 1 . 5 × 1 m3 towing tank at UMD which was equipped with a 4-axis computer-controlled motion system. The effect of a stream-wise gust was simulated by accelerating or decelerating the wing to a new constant velocity after an initial constant surge. A high-speed camera and light sheet optics were attached to the tow carriage allowing for time-resolved particle image velocimetry along the entire motion in addition to direct force measurements. A proper orthogonal decomposition of the flow field was carried out to study the time scales related to changes induced by the sudden acceleration or deceleration in addition to analyzing the size, position and trajectory of prominent vortices and associated forces during the gust encounter.

  19. Experimental Investigation of a Shrouded Rotor Micro Air Vehicle in Hover and in Edgewise Gusts

    Hrishikeshavan, Vikram

    flybarless rotor vehicle was conducted about hover. Controllability metrics were extracted based on controllability gramian treatment for the flybar and flybarless rotor. In edgewise gusts, the shrouded rotor generated up to 3 times greater pitching moment and 80% greater drag than an equivalent unshrouded rotor. In order to improve gust tolerance and control moments, rotor design optimizations were made by varying solidity, collective, operating RPM and planform. A rectangular planform rotor at a collective of 18 deg was seen to offer the highest control authority. The shrouded rotor produced 100% higher control moments due to pressure asymmetry arising from cyclic control of the rotor. It was seen that the control margin of the shrouded rotor increased as the disk loading increased, which is however deleterious in terms of hover performance. This is an important trade-off that needs to be considered. The flight performance of the vehicle in terms of edgewise gust disturbance rejection was tested in a series of bench top and free ight tests. A standard table fan and an open jet wind tunnel setup was used for bench top setup. The shrouded rotor had an edgewise gust tolerance of about 3 m/s while the unshrouded rotor could tolerate edgewise gusts greater than 5 m/s. Free flight tests on the vehicle, using VICON for position feedback control, indicated the capability of the vehicle to recover from gust impulse inputs from a pedestal fan at low gust values (up to 3 m/s).

  20. Wind gust estimation by combining numerical weather prediction model and statistical post-processing

    Patlakas, Platon; Drakaki, Eleni; Galanis, George; Spyrou, Christos; Kallos, George


    The continuous rise of off-shore and near-shore activities as well as the development of structures, such as wind farms and various offshore platforms, requires the employment of state-of-the-art risk assessment techniques. Such analysis is used to set the safety standards and can be characterized as a climatologically oriented approach. Nevertheless, a reliable operational support is also needed in order to minimize cost drawbacks and human danger during the construction and the functioning stage as well as during maintenance activities. One of the most important parameters for this kind of analysis is the wind speed intensity and variability. A critical measure associated with this variability is the presence and magnitude of wind gusts as estimated in the reference level of 10m. The latter can be attributed to different processes that vary among boundary-layer turbulence, convection activities, mountain waves and wake phenomena. The purpose of this work is the development of a wind gust forecasting methodology combining a Numerical Weather Prediction model and a dynamical statistical tool based on Kalman filtering. To this end, the parameterization of Wind Gust Estimate method was implemented to function within the framework of the atmospheric model SKIRON/Dust. The new modeling tool combines the atmospheric model with a statistical local adaptation methodology based on Kalman filters. This has been tested over the offshore west coastline of the United States. The main purpose is to provide a useful tool for wind analysis and prediction and applications related to offshore wind energy (power prediction, operation and maintenance). The results have been evaluated by using observational data from the NOAA's buoy network. As it was found, the predicted output shows a good behavior that is further improved after the local adjustment post-process.

  1. Statistical Downscaling of Gusts During Extreme European Winter Storms Using Radial-Basis-Function Networks

    Voigt, M.; Lorenz, P.; Kruschke, T.; Osinski, R.; Ulbrich, U.; Leckebusch, G. C.


    Winterstorms and related gusts can cause extensive socio-economic damages. Knowledge about the occurrence and the small scale structure of such events may help to make regional estimations of storm losses. For a high spatial and temporal representation, the use of dynamical downscaling methods (RCM) is a cost-intensive and time-consuming option and therefore only applicable for a limited number of events. The current study explores a methodology to provide a statistical downscaling, which offers small scale structured gust fields from an extended large scale structured eventset. Radial-basis-function (RBF) networks in combination with bidirectional Kohonen (BDK) maps are used to generate the gustfields on a spatial resolution of 7 km from the 6-hourly mean sea level pressure field from ECMWF reanalysis data. BDK maps are a kind of neural network which handles supervised classification problems. In this study they are used to provide prototypes for the RBF network and give a first order approximation for the output data. A further interpolation is done by the RBF network. For the training process the 50 most extreme storm events over the North Atlantic area from 1957 to 2011 are used, which have been selected from ECMWF reanalysis datasets ERA40 and ERA-Interim by an objective wind based tracking algorithm. These events were downscaled dynamically by application of the DWD model chain GME → COSMO-EU. Different model parameters and their influence on the quality of the generated high-resolution gustfields are studied. It is shown that the statistical RBF network approach delivers reasonable results in modeling the regional gust fields for untrained events.

  2. Active control of gust- and interference-induced vibration of tilt-rotor aircraft

    Ham, Norman D.; Wereley, Norman M.; Von Ellenrieder, Karl D.


    An active control system to suppress the response of the blade bending modes of a tilt-rotor aircraft to axial gusts and wing/rotor interference is described. The use of blade-mounted accelerometers as sensors is shown to permit the measurement and control of tilt-rotor blade modal responses and their associated vibratory loads directly. The feedback of modal acceleration, in addition to modal rate and displacement, is demonstrated to provide a control phase lead, in comparison with feedback of modal rate and displacement only, which makes higher system gains achievable.

  3. Large-Eddy Simulation of the Gust Index in an Urban Area Using the Lattice Boltzmann Method

    Ahmad, Nurul Huda; Inagaki, Atsushi; Kanda, Manabu; Onodera, Naoyuki; Aoki, Takayuki


    We used numerical simulations to investigate the general relationship between urban morphology and the intensity of wind gusts in built-up areas at the pedestrian level. The simulated urban boundary layer developed over a 19.2 km (length) × 4.8 km (width) × 1.0 km (height) simulation domain, with 2-m resolution in all directions, to explicitly resolve the detailed shapes of buildings and the flow at the pedestrian level. This complex computation was accomplished using the lattice Boltzmann method and by implementing a large-eddy simulation model. To generalize the results, a new parameter that expresses the intensity of gusts (the gust index, {\\tilde{U}}_{ max}) was defined as the local maximum wind speed divided by the freestream velocity. In addition, this parameter was decomposed into the mean wind-speed ratio, {\\tilde{U}} and turbulent gust ratio, {\\tilde{U}}^' }} to evaluate the qualities of gusts. These parameters were useful for quantitatively comparing the gust intensities within urban canopies at different locations or even among different experiments. In addition, the entire horizontal domain was subdivided into homogeneous square patches, in which both the simulated gust parameters and the morphological characteristics of building geometries were averaged. This procedure masked the detailed structure of individual buildings but retained the bulk characteristics of the urban morphology. At the pedestrian level, the gust index decreased with increasing building cover. Compared to {\\tilde{U}} , the quantity {\\tilde{U}}^' }} notably contributed to the index throughout the range of plan area index (λ _p) values. The dependences of all normalized wind-speed ratios transiently changed at λ _p = 0.28. In cases where λ _p constant. In cases where λ _p > 0.28, {\\tilde{U}} was almost constant and {\\tilde{U}}^' }} decreased with increasing λ _p . This was explained by the change in flow regimes within the building canyon. At a higher elevation above

  4. Large-Eddy Simulation of the Gust Index in an Urban Area Using the Lattice Boltzmann Method

    Ahmad, Nurul Huda; Inagaki, Atsushi; Kanda, Manabu; Onodera, Naoyuki; Aoki, Takayuki


    We used numerical simulations to investigate the general relationship between urban morphology and the intensity of wind gusts in built-up areas at the pedestrian level. The simulated urban boundary layer developed over a 19.2 km (length) × 4.8 km (width) × 1.0 km (height) simulation domain, with 2-m resolution in all directions, to explicitly resolve the detailed shapes of buildings and the flow at the pedestrian level. This complex computation was accomplished using the lattice Boltzmann method and by implementing a large-eddy simulation model. To generalize the results, a new parameter that expresses the intensity of gusts (the gust index, {tilde{U}}_{ max}) was defined as the local maximum wind speed divided by the freestream velocity. In addition, this parameter was decomposed into the mean wind-speed ratio, {tilde{U}} and turbulent gust ratio, {tilde{U}}^' }} to evaluate the qualities of gusts. These parameters were useful for quantitatively comparing the gust intensities within urban canopies at different locations or even among different experiments. In addition, the entire horizontal domain was subdivided into homogeneous square patches, in which both the simulated gust parameters and the morphological characteristics of building geometries were averaged. This procedure masked the detailed structure of individual buildings but retained the bulk characteristics of the urban morphology. At the pedestrian level, the gust index decreased with increasing building cover. Compared to {tilde{U}} , the quantity {tilde{U}}^' }} notably contributed to the index throughout the range of plan area index (λ _p) values. The dependences of all normalized wind-speed ratios transiently changed at λ _p = 0.28 . In cases where λ _p 0.28, {tilde{U}} was almost constant and {tilde{U}}^' }} decreased with increasing λ _p . This was explained by the change in flow regimes within the building canyon. At a higher elevation above the canopy layer, λ _p becomes less relevant to

  5. Spatial selection and grouping of raindrops by size in wind gusts

    Sterlyadkin, V. V.


    Results that indicate the grouping of droplets of the same size in certain regions of space have been obtained during in situ measurements of the instantaneous structure and spatial and temporal distribution of rains (using methods based on the effect of abnormally high modulation of the scattered light). Calculations that show that such a grouping can be associated with wind gusts and intense turbulence are presented. It is shown that a lateral wind gust leads to the grouping of drops of different sizes in different layers. The processes of spatial selection and grouping are considered for both the laminar flow in the case of droplets and for the turbulent flow regime in the case of the coarse fraction of drops. It is stated that the clustering of particles can lead to a sharp increase in the received signal strength and the anomalous dependence of the backscatter cross section on the wavelength. This means that not only the microstructure of scatterers, but also the dynamic state of the atmosphere should be considered in the interpretation of radar data, e.g., Z-I ratio. The considered clustering mechanism can cause the rapid formation of raindrops in the clouds.

  6. Using Buoy and Radar Data to Study Sudden Wind Gusts Over Coastal Regions

    Priftis, Georgios; Chronis, Themis; Lang, Timothy J.


    Significant sudden wind gusts can pose a threat to aviation near the coastline, as well as small (sailing) boats and commercial ships approaching the ports. Such cases can result in wind speed changes of more than an order of magnitude within 5 minutes, which can then last up to 20 minutes or more. Although the constellation of scatterometers is a good means of studying maritime convection, those sudden gusts are not easily captured because of the low time resolution. The National Data Buoy Center (NDBC) provides continuous measurements of wind speed and direction along the US coastal regions every 6 minutes. Buoys are platforms placed at specific places on the seas, especially along coastlines, providing data for atmospheric and oceanic studies. Next Generation Radars (NEXRADs), after the recent upgrade of the network to dual-pol systems, offer enhanced capabilities to study atmospheric phenomena. NEXRADs provide continuous full-volume scans approximately every 5 minutes and therefore are close to the time resolution of the buoy measurements. Use of single- Doppler retrievals might also provide a means of further validation.

  7. Application of dynamic decoupling fuzzy control method in aircraft gust alleviation

    Li, Aijun; Tan, Jian; Zhang, Weiguo; Sun, Xun


    Dynamic inversion method can not only remove a system's nonlinear factors, but also achieve the system's dynamic decoupling. But its decoupling effect completely depends on the accuracy of the mathematical model of the system. A dynamic decoupling fuzzy control method for MIMO system is presented in this paper, which employs the dynamic inversion method to decouple the multivariable system and introduces a fuzzy controller, without quantification, with correcting function, and expressed in analytic form to overcome the poor decoupling effect when the system model is inaccurate. It is feasible and convenient to compute, tune, and realize the control rules by computer, to adjust the parameters of the controller and to optimize the design of the control system, for the rules are described by analytical expression. The method is adopted to design vertical transition mode of an active control aircraft for gust alleviation. The control laws and simulation diagrams of the system are designed. Simulation results in MATLAB show that the vertical transition mode designed by dynamic decoupling fuzzy control method increases the gust-against effect by about 34% compared with that of a normal aircraft.

  8. The Impact of Natural Hazards such as Turbulent Wind Gusts on the Wind Energy Conversion Process

    Wächter, M.; Hölling, M.; Milan, P.; Morales, A.; Peinke, J.


    Wind turbines operate in the atmospheric boundary layer, where they are exposed to wind gusts and other types of natural hazards. As the response time of wind turbines is typically in the range of seconds, they are affected by the small scale intermittent properties of the turbulent wind. We show evidence that basic features which are known for small-scale homogeneous isotropic turbulence, and in particular the well-known intermittency problem, have an important impact on the wind energy conversion process. Intermittent statistics include high probabilities of extreme events which can be related to wind gusts and other types of natural hazards. As a summarizing result we find that atmospheric turbulence imposes its intermittent features on the complete wind energy conversion process. Intermittent turbulence features are not only present in atmospheric wind, but are also dominant in the loads on the turbine, i.e. rotor torque and thrust, and in the electrical power output signal. We conclude that profound knowledge of turbulent statistics and the application of suitable numerical as well as experimental methods are necessary to grasp these unique features and quantify their effects on all stages of wind energy conversion.

  9. Extreme-value time-series analysis of Australian Region A gust wind speeds to examine instrument bias

    Cechet, R. P.; Sanabria, L. A.


    Australian building codes through the Australia/New Zealand Wind Actions Standard as well as the wind engineering community in general rely to a significant extent on the peak gust wind speed observations collected over more than 70 years by the Australian Bureau of Meteorology (BoM). In the mid-1980's BoM commenced a program to replace the aging pressure tube Dines anemometers with cup anemometers. During the replacement procedure, many localities had more than one type of anemometer operating, recording extreme events. Systematic differences between instrument measurements during this overlap period raised serious concerns about the utility of the peak gust wind speed database. This paper presents the results of a reanalysis of the current BoM peak wind gust database for the non-cyclonic region (Region A) of the Australia/New Zealand Wind Actions Standard. The study utilises extreme value distribution analysis and compares estimates of the 500-year return-period (RP) peak gust wind exceedance level derived from segments of the record measured with the Dines and replacement anemometers. Results indicate that the later period appears to have a significant reduction in extreme events; 17 of 31 sites have a mean 500 year RP exceedance level for the replacement anemometer section of the record below the lower 95% confidence limit for the Dines anemometer part of the record. The 3PM mean wind speed time-series observations have also been examined, and they exhibit a similar trend.

  10. Springtime connections between the large-scale sea-level pressure field and gust wind speed over Iberia and the Balearics

    M. L. Martín


    Full Text Available This paper investigates, by means of Singular Value Decomposition analysis, the springtime relationships between the mean sea-level pressure field over the North Atlantic and the regional wind gusts over the Iberian Peninsula, identifying the main atmospheric circulation patterns linked to gust wind speed anomaly configurations. The statistical significance of the obtained modes is investigated by means of Monte Carlo approach. The analysis highlighted that the covariability is dominated by two main large-scale features of the atmospheric circulation over the North Atlantic. The first mode relates to Iberian gust wind speeds to the Scandinavian pattern (SCAND, linking the large-scale pattern to above-normal wind gusts. The second covariability mode, associated with the North Atlantic Oscillation (NAO pattern, correlates with maximum wind speeds over Iberia. An enhanced spring NAO pattern is related to positive (negative wind gust correlations over northern (southern Iberia. To find true relationships between large-scale atmospheric field and the gust wind speeds, composite maps were built up to give an average atmospheric circulation associated with coherent wind gust variability over Iberia.

  11. The passage of an infinite swept airfoil through an oblique gust. [approximate solution for aerodynamic response

    Adamczyk, J. L.


    An approximate solution is reported for the unsteady aerodynamic response of an infinite swept wing encountering a vertical oblique gust in a compressible stream. The approximate expressions are of closed form and do not require excessive computer storage or computation time, and further, they are in good agreement with the results of exact theory. This analysis is used to predict the unsteady aerodynamic response of a helicopter rotor blade encountering the trailing vortex from a previous blade. Significant effects of three dimensionality and compressibility are evident in the results obtained. In addition, an approximate solution for the unsteady aerodynamic forces associated with the pitching or plunging motion of a two dimensional airfoil in a subsonic stream is presented. The mathematical form of this solution approaches the incompressible solution as the Mach number vanishes, the linear transonic solution as the Mach number approaches one, and the solution predicted by piston theory as the reduced frequency becomes large.

  12. Analysis of Acceleration, Airspeed, and Gust-Velocity Data From a Four-Engine Transport Airplane Operating Over a Northwestern United States Alaska Route

    Engel, Jerome N.; Copp, Martin R.


    Acceleration, airspeed, and altitude data obtained with an NACA VGH recorder from a four-engine commercial transport airplane operating over a northwestern United States-Alaska route were evaluated to determine the magnitude and frequency of occurrence of gust and maneuver accelerations., operating airspeeds, and gust velocities. The results obtained were then compared with the results previously reported in NACA Technical Note 3475 for two similar airplanes operating over transcontinental routes in the United States. No large variations in the gust experience for the three operations were noted. The results indicate that the gust-load experience of the present operation closely approximated that of the central transcontinental route in the United States with which it is compared and showed differences of about 4 to 1 when compared with that of the southern transcontinental route in the United States. In general, accelerations due to gusts occurred much more frequently than those due to operational maneuvers. At a measured normal-acceleration increment of 0.5g, accelerations due to gusts occurred roughly 35 times more frequently than those due to operational maneuvers.

  13. Gust Acoustic Response of a Swept Rectilinear Cascade Using The Space-Time CE/SE Method

    Wang, X. Y.; Himansu, A.; Jorgenson, P. C.; Chang, S. C.


    The benchmark problem 3 in Category 3 of the third Computational Aero-Acoustics (CAA) Workshop sponsored by NASA Glenn Research Center is solved using the space-time conservation element and solution element (CE/SE) method. This problem concerns the unsteady response of a rectilinear swept cascade to an incident gust. The acoustic field generated by the interaction of the gust with swept at plates in the cascade is computed by solving the 3D nonlinear Euler equations using the space-time CE/SE method. A parallel version of the 3D CE/SE Euler solver is employed to obtain numerical solutions for several sweep angles. Numerical solutions are presented and compared with the analytical solutions.

  14. Requirements for large-eddy simulation of surface wind gusts in a mountain valley

    Revell, Michael J.; Purnell, Don; Lauren, Michael K.


    During the passage of a front, data from a light-weight cup anemometer and wind vane, sited in a steep-walled glacial valley of the Mt Cook region of the Southern Alps of New Zealand, were analysed to derive a power spectrum of the wind velocity for periods between 0.5 and 16 min. The energy spectrum roughly followed a -5/3 power law over the range of periods from 0.5 4 min — as might be expected in the case of an inertial subrange of eddies. However, any inertial subrange clearly does not extend to periods longer than this. We suggest that the observed eddies were generated in a turbulent wake associated with flow separation at the ridge crests, and large eddies are shed at periods of 4 8 min or more. A compressible fluid-dynamic model, with a Smagorinsky turbulence closure scheme and a “law of the wall” at the surface, was used to calculate flow over a cross section through this area in neutrally stratified conditions. A range of parameters was explored to assess some of the requirements for simulating surface wind gusts in mountainous terrain in New Zealand. In order to approximate the observed wind spectrum at Tasman aerodrome, Mount Cook, we found the model must be three-dimensional, with a horizontal resolution better than 250 m and with a Reynolds-stress eddy viscosity of less than 5 m2 s-1. In two-dimensional simulations, the eddies were too big in size and in amplitude and at the surface this was associated with reversed flow extending too far downstream. In contrast the three-dimensional simulations gave a realistic gusting effect associated with large scale “cat's paws” (a bigger variety of those commonly seen over water downstream of moderate hills), with reversed flow only at the steep part of the lee slope. The simulations were uniformly improved by better resolution, at all tested resolutions down to 250 m mesh size. The spectra of large eddies simulated in steep terrain were not very sensitive to the details of the eddy stress formulation

  15. The importance of the unsteady Kutta condition when modelling gust-aerofoil interaction

    Ayton, Lorna J.; Gill, J. R.; Peake, N.


    The Kutta condition is applied to aerofoils with sharp trailing edges to allow for viscous effects to be considered within a simplified system of equations that are inviscid. This paper discusses in detail the inclusion of an unsteady Kutta condition at a sharp trailing edge during gust-aerofoil interaction and illustrates how the analytic solution for the far-field noise generated by this interaction changes if the unsteady Kutta condition is neglected, or more precisely, if the unsteady pressure is permitted to be singular at the trailing edge. The analytic solution, both with and without the unsteady Kutta condition, is compared with numerical results that have no imposed unsteady Kutta condition. Importantly the results agree well only when the unsteady Kutta condition is neglected in the analytic solution. This paper highlights where the far-field acoustics are most affected by neglecting the unsteady Kutta condition for a variety of singularities that can occur in the unsteady pressure at the trailing edge and shows that results permitting different behaviour in the unsteady surface pressure at the trailing edge could give significantly different far-field noise predictions, even though the surface pressure elsewhere along the aerofoil surface agrees with benchmark solutions.

  16. Aeroservoelastic Testing of Free Flying Wind Tunnel Models Part 2: A Centerline Supported Fullspan Model Tested for Gust Load Alleviation

    Scott, Robert C.; Vetter, Travis K.; Penning, Kevin B.; Coulson, David A.; Heeg, Jennifer


    This is part 2 of a two part document. Part 1 is titled: "Aeroservoelastic Testing of Free Flying Wind Tunnel Models Part 1: A Sidewall Supported Semispan Model Tested for Gust Load Alleviation and Flutter Suppression." A team comprised of the Air Force Research Laboratory (AFRL), Boeing, and the NASA Langley Research Center conducted three aeroservoelastic wind tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, flexible vehicles. In the first of these three tests, a full-span, aeroelastically scaled, wind tunnel model of a joined wing SensorCraft vehicle was mounted to a force balance to acquire a basic aerodynamic data set. In the second and third tests, the same wind tunnel model was mated to a new, two degree of freedom, beam mount. This mount allowed the full-span model to translate vertically and pitch. Trimmed flight at10 percent static margin and gust load alleviation were successfully demonstrated. The rigid body degrees of freedom required that the model be flown in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort. The balance and free flying wind tunnel tests will be summarized. The design of the trim and gust load alleviation control laws along with the associated results will also be discussed.

  17. Reduction of vertical-gust induced loads on elastic airplane model with slotted-interceptor-type surfaces

    Mazutsky, A. Yu.


    Results of T-203 wind-tunnel tests of an elastic airplane model dynamically similar to Tu-204 aircraft equipped with a passive wing load reduction system are reported. The wing load reduction system comprised two auxiliary aerodynamic surfaces of the slotted-interceptor type installed symmetrically on the upper surface of the lifting wing at the boundary-layer height. It was found that, with the operating system, the additional bending moments induced by symmetric vertical discrete gusts in the wing root and at the fuselage mid-body decreased by 20%, with simultaneous increase observed in the flexure-pylon flutter speed.

  18. Comparative analysis of the Parent Attitudes about Childhood Vaccines (PACV) short scale and the five categories of vaccine acceptance identified by Gust et al.

    Oladejo, Omolade; Allen, Kristen; Amin, Avnika; Frew, Paula M; Bednarczyk, Robert A; Omer, Saad B


    There is a need to develop a standardized tool to aid in identifying, measuring and classifying the unique needs of vaccine-hesitant parents (VHPs). This will also assist in designing tailored interventions to address these needs. The Parental Attitude about Childhood Vaccines (PACV) short scale developed by Opel et al., and the Gust et al. vaccine acceptance categories have been acknowledged as potentially useful tools to measure parental vaccine hesitancy. The PACV short scale requires further validation. In our study, we evaluated how the Gust et al. vaccine acceptance categories correspond with the PACV short scale. As part of a larger study on vaccine attitudes, using the PACV short scale and Gust et al. vaccine acceptance categories, we assessed the correlation between the two measures using Spearman correlation coefficient, and the association between the two measures using the Cochran-Mantel-Haentszel test of association. We used logistic regression modelling to compare the association between a child's up-to-date immunization status and (a) PACV short scale and (b) Gust et al. vaccine acceptance categories. The PACV short scale and Gust et al. vaccine acceptance categories were positively correlated (r=0.6, df=198, pscales similarly predicted children's up-to-date immunization status for all recommended childhood vaccines. The ability of the PACV short scale to identify and classify parental vaccine hesitancy is similar to classification using Gust et al. vaccine acceptance categories, and both measure linear entities. The PACV short scale is recommended for screening parents at their first pediatric visit because it is easier to administer. A clearer understanding of how to classify parental vaccine hesitancy can be used to design tailored interventions based on these classifications, to address their specific needs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Code and Solution Verification of 3D Numerical Modeling of Flow in the Gust Erosion Chamber

    Yuen, A.; Bombardelli, F. A.


    Erosion microcosms are devices commonly used to investigate the erosion and transport characteristics of sediments at the bed of rivers, lakes, or estuaries. In order to understand the results these devices provide, the bed shear stress and flow field need to be accurately described. In this research, the UMCES Gust Erosion Microcosm System (U-GEMS) is numerically modeled using Finite Volume Method. The primary aims are to simulate the bed shear stress distribution at the surface of the sediment core/bottom of the microcosm, and to validate the U-GEMS produces uniform bed shear stress at the bottom of the microcosm. The mathematical model equations are solved by on a Cartesian non-uniform grid. Multiple numerical runs were developed with different input conditions and configurations. Prior to developing the U-GEMS model, the General Moving Objects (GMO) model and different momentum algorithms in the code were verified. Code verification of these solvers was done via simulating the flow inside the top wall driven square cavity on different mesh sizes to obtain order of convergence. The GMO model was used to simulate the top wall in the top wall driven square cavity as well as the rotating disk in the U-GEMS. Components simulated with the GMO model were rigid bodies that could have any type of motion. In addition cross-verification was conducted as results were compared with numerical results by Ghia et al. (1982), and good agreement was found. Next, CFD results were validated by simulating the flow within the conventional microcosm system without suction and injection. Good agreement was found when the experimental results by Khalili et al. (2008) were compared. After the ability of the CFD solver was proved through the above code verification steps. The model was utilized to simulate the U-GEMS. The solution was verified via classic mesh convergence study on four consecutive mesh sizes, in addition to that Grid Convergence Index (GCI) was calculated and based on

  20. Effect of Frontal Gusts and Stroke Deviation in Forward Flapping Flight and Deconstructing the Aerodynamics of a Fruit Bat

    Viswanath, Kamal

    This dissertation broadly seeks to understand the effect different kinematic parameters, external forces, and dynamic wing conformation have on the fluid dynamics of flapping flight. The primary motivation is to better grasp the fundamental fluid phenomena driving efficient flapping flight in the Reynolds number regime of birds, bats, and man made fliers of similar scale. The CFD solver (GenIDLEST) used is a Navier-Stokes solver in a finite volume formulation on non-staggered structured multiblock meshes. It has the capability for both body-fitted moving grid simulations and Immersed Boundary Method (IBM) for simulating complex bodies moving within a fluid. To that purpose we investigate the response of a rigid flapping thin surface planar wing in forward flight, at Re=10,000, subjected to frontal gusts. Gusts are a common ecological hazard for flapping fliers, especially in crowded environments. Among the various temporal and spatial scales of gust possible, we look at the phasing and duration of very large spatial scale gusts and their impact on the unsteady fluid dynamics of flapping within a single flapping cycle. The gust is characterized by a step function with time scale much smaller than the flapping time period. Having the advantage of prescribing the motion, as well as the timing and duration of the gust, this allowed the observation of the effect of angle of attack (AOA) and wing rotation on the evolution of the Leading Edge Vortex (LEV) and, hence the instantaneous lift and thrust profiles, by varying the parameters. During the downstroke, frontal gusts accelerated the flow development resulting in early separation of existing LEVs and formation of new ones on the wing surface which influenced the force generation by increasing the lift and thrust. These phenomena underscored the importance of the unsteady vortex structures as the primary force generators in flapping flight. The effect of the gust is observed to be diminished when it occurs during rapid

  1. Common aspects and differences in the behaviour of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage

    Octavian PREOTU


    Full Text Available The paper analyzes, in parallel, common aspects and differences in the behavior of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage. The effects of the main constructional dimensions of the horizontal empennage on lift cancelling and horizontal empennage control are being analyzed

  2. Automatic Identification and Alert of Gust Fronts%阵风锋自动识别与预警

    郑佳锋; 张杰; 朱克云; 刘艳霞; 张涛


    根据阵风锋的回波特征,该文设计了阵风锋自动识别算法.在速度场中,考虑辐合线识别;在强度场中,考虑窄带回波识别;根据窄带与辐合线的空间一致性,综合二者识别出阵风锋.基于该算法,以锋线闪烁和物理量输出两种方式实现了预警功能.最后利用地面自动气象站资料和2009年6月3日河南商丘、郑州及2009年6月5日安徽阜阳3个雷达站探测的阵风锋98个体扫样本资料检验了识别效果,并采用临界成功指数进行评估.结果表明:双向梯度法能有效滤除大范围降水回波而保留窄带回波;该算法只需考虑较低仰角层,大大提高识别效率.在速度场中采用的算法能有效识别出径向辐合线,同时也适用于低空径向风切变和辐合线的识别;利用临界成功指数对98个体扫样本进行识别率评估,识别率达到68.4%.%Gust fronts often cause serious ground gale and strong wind shear. Therefore, the short-term forecast, nowcasting and civil aviation department pay high attention to the research of gust fronts. Based on the echo characteristics of gust fronts in reflectivity field and velocity field of Doppler radar, an identification algorithm for gust fronts is designed. In the velocity field, the convergence line is identified by finding the consistent decreasing radial velocity and inspected by using a convergence parameter threshold, a grads threshold and a flux threshold. In the reflectivity field, the reflectivity data are classified into different levels. Then, the narrowband is identified by an algorithm called bilateral grads, which is designed by fully using the narrowband geometrical characteristic, the interval between narrowband and echo matrix. The bilateral grads algorithm can effectively filter out the wide range of precipitation echoes and reserve the narrowband in reflectivity image. Meanwhile, in order to filter out the remainder noise, length calculated and image thinning

  3. Identifying areas with high risk of wind gusts, precipitation and hail based on interpolated and recorded data in Hungary

    Lakatos, M.; Móring, A.; Szentimrey, T.; Németh, Á.; Bihari, Z.; Kovács, T.; Vincze, E.


    Risk identification, analysis and risk management measures are major components of the disaster prevention. Extreme climate events such as storms and heavy rain and hail are increasing weather phenomena in Hungary in the last decades. The set out of the especially hazardous settlements is introduced in this paper. The examinations were performed are based on observations are stored in the climate database of the Hungarian Meteorological Service. The daily maximum wind gusts, daily precipitation sums and the hail records were used in the analysis. The daily data are coming from the meteorological network. The network of settlements is different from the meteorological network, thus the first step was the interpolation of daily measurements for the network of the settlements referred their latitude and longitude. The method MISH (Meteorological Interpolation based on Surface Homogenized Data Basis, Szentimrey, Bihari) were used for the interpolation of the station data. The idea behind the MISH interpolation scheme stems from the following principles: interpolated data can be created at higher quality with respect to certain climate statistical parameters; and these parameters can be modelled by using the long climate data series. In the MISH procedure the modelling of the statistical parameters for a given location is based on the long term homogenized monthly data of neighbouring stations. Additive (e.g. temperature) or multiplicative (e.g. precipitation) model and interpolation formula can be used depending on the climate elements. In this work the multiplicative formula were used for wind gust and precipitation data as well. In the case of hail the station based frequency was interpolated for the specific locations. In the case of wind gust measurements the period of 2001-2010 and in the case of precipitation data and hail records the period of 1981-2010 were used in the calculations. The measure of the exposure to strong wind or heavy rain on a certain location

  4. Aeroservoelastic Testing of Free Flying Wind Tunnel Models Part 1: A Sidewall Supported Semispan Model Tested for Gust Load Alleviation and Flutter Suppression

    Scott, Robert C.; Vetter, Travis K.; Penning, Kevin B.; Coulson, David A.; Heeg, Jennifer.


    of a two part document. Part 2 is titled: "Aeroservoelastic Testing of Free Flying Wind Tunnel Models, Part 2: A Centerline Supported Fullspan Model Tested for Gust Load Alleviation." A team comprised of the Air Force Research Laboratory (AFRL), Northrop Grumman, Lockheed Martin, and the NASA Langley Research Center conducted three aeroservoelastic wind tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, flexible vehicles. In the first of these three tests, a semispan, aeroelastically scaled, wind tunnel model of a flying wing SensorCraft vehicle was mounted to a force balance to demonstrate gust load alleviation. In the second and third tests, the same wing was mated to a new, multi-degree of freedom, sidewall mount. This mount allowed the half-span model to translate vertically and pitch at the wing root, allowing better simulation of the full span vehicle's rigid body modes. Gust load alleviation (GLA) and Body freedom flutter (BFF) suppression were successfully demonstrated. The rigid body degrees-of-freedom required that the model be flown in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort.


    龚华军; 杨一栋


    阵风响应缓和研究对于具有强耦合和振动的直升机非常重要,阵风扰动不仅影响直升机的乘座品质和武器投放精度,而且影响直升机的疲劳载荷和强度.本文提出直升机抑制阵风扰动的最优控制律设计方法.优化性能指标要求在阵风扰动下驾驶员处法向过载、飞机姿态变化以及控制信号能量损耗最小.最终所综合的系统工程实现简便,只需在直升机姿态控制系统基础上增加垂直升降速率反馈通道即可.最后使用C语言实现控制律并进行半物理仿真, 仿真结果表明,控制律优化及数字化实现的效果是令人满意的.%Gust response alleviation is very important for helicopters which have strong coupling and vibration. Gust disturbance not only influences the ride quality and the precision of the weapon delivery, but also affects to the structural fatigue load and the strength. The method of an optimal control law to suppress the gust disturbance for helicopters is presented. The optimization requires the minimization of the vertical overload at the pilot′s seat, the attitude variation and the control energy consumption under the gust disturbance. Based on the original control system, the new system can be easily realized by adding a vertical speed feedback passage. In order to develop the real-time operational flight control system, the optimized control law is written in C language. The hybrid simulations prove that the performance of gust response alleviation and the efficiency of digitalization are satisfactory.

  6. 民用飞机阵风载荷及减缓技术的研究%esearch on Gust Load and its Load Alleviation Technology of Civil Aircrafts

    赵继伟; 胡赞远


    Due to the characteristic of large ratio wing of civil aircrafts, gust load often composes of the severe conditions of civil aircrafts. And it must be emphasized by all countries' airworthiness regulations. Moreover, owing to the elasticity of the aircraft structure, gust disturbance induces the elastic vibrations, reduces the structure stress, produces the fatigue damage, and even promote flutter. Thus it is of very importance and significance to investigate and research in gust load and gust load alleviation technologies in flight load design. This paper gives a brief introduction of gust load theories and the relevant technologies and also puts forward a type of gust load alleviation of method direct lift control to carry out gust load alleviation of the wing.%由于民用飞机机翼具有大展弦比的特点,因此阵风载荷经常成为民用飞机飞行载荷的严重情况,是各国适航标准重点考察的飞行情况。而且,阵风干扰还会因飞机机体的自身弹性引起结构弹性振动,使飞机结构刚度降低,造成机体疲劳损伤,甚至引起颤振。因此,在民用飞机载荷设计过程中对阵风载荷及其减缓技术进行研究具有非常重要的意义。介绍了民用飞机阵风载荷的原理及相关技术,以及阵风载荷减缓技术中用直接升力控制方法来实现机翼的阵风载荷减缓。

  7. Assessment of a sponge layer as a non-reflective boundary treatment with highly accurate gust-airfoil interaction results

    Crivellini, A.


    This paper deals with the numerical performance of a sponge layer as a non-reflective boundary condition. This technique is well known and widely adopted, but only recently have the reasons for a sponge failure been recognised, in analysis by Mani. For multidimensional problems, the ineffectiveness of the method is due to the self-reflections of the sponge occurring when it interacts with an oblique acoustic wave. Based on his theoretical investigations, Mani gives some useful guidelines for implementing effective sponge layers. However, in our opinion, some practical indications are still missing from the current literature. Here, an extensive numerical study of the performance of this technique is presented. Moreover, we analyse a reduced sponge implementation characterised by undamped partial differential equations for the velocity components. The main aim of this paper relies on the determination of the minimal width of the layer, as well as of the corresponding strength, required to obtain a reflection error of no more than a few per cent of that observed when solving the same problem on the same grid, but without employing the sponge layer term. For this purpose, a test case of computational aeroacoustics, the single airfoil gust response problem, has been addressed in several configurations. As a direct consequence of our investigation, we present a well documented and highly validated reference solution for the far-field acoustic intensity, a result that is not well established in the literature. Lastly, the proof of the accuracy of an algorithm for coupling sub-domains solved by the linear and non-liner Euler governing equations is given. This result is here exploited to adopt a linear-based sponge layer even in a non-linear computation.

  8. A modeling study of convection initiation prior to the merger of a sea-breeze front and a gust front

    Abulikemu, Abuduwaili; Xu, Xin; Wang, Yuan; Ding, Jinfeng; Zhang, Shushi; Shen, Wenqiang


    Convection initiation (CI) prior to the merger of a sea-breeze front (SBF) with a gust front (GF) in North China is investigated using a real-data Weather Research and Forecasting (WRF) simulation with a high resolution of 444.4 m. The overall evolution of the GF and SBF is well reproduced by the simulation. The GF was produced by the decaying convective storm over northern Beijing, while the SBF came from the Bohai Sea. Several convective cells were generated between the two fronts even though they were still about 25-30 km far away from each other. During the development of these cells, the low-level convergence and conditional instability averaged within the intermediate area between the two fronts were enhanced significantly, both of which favored the initiation of convection. Vertical momentum budgets were conducted in the intermediate area as well as along the backward trajectories of parcels within a selected convective cell. The vertical acceleration was decomposed into dynamic and buoyant components, respectively. The diagnostic results showed that the dynamic acceleration dominated in the low level, while buoyant acceleration became evident only when the parcel reached a high altitude above 2 km. Therefore the dynamic forcing appeared to be more relevant to CI. The dynamic acceleration was further decomposed into four terms based on anelastic approximation. The positive dynamic acceleration was mainly caused by fluid extension associated with the low-level convergence, while fluid twisting in the vertical contributed negatively to the dynamic acceleration. The other two terms related to horizontal curvature and height variation of density were negligibly small.

  9. János Kádár as an Economic Reformist And Gustáv Husák As An Antireformist

    Horbulák Zsolt


    This paper deals with both political and economic history. The main task was to try to compare the attitude of Gustáv Husák and János Kádár about economic reforms in their own countries. The comparison was based on their lives, interests and personalities. Historical evaluation and biographical material was also used. Taking into account that the political circumstances were very similar, the root of the differences between the acts of these politicians had to be the result of individual fact...

  10. Aeroservoelastic Wind-Tunnel Tests of a Free-Flying, Joined-Wing SensorCraft Model for Gust Load Alleviation

    Scott, Robert C.; Castelluccio, Mark A.; Coulson, David A.; Heeg, Jennifer


    A team comprised of the Air Force Research Laboratory (AFRL), Boeing, and the NASA Langley Research Center conducted three aeroservoelastic wind-tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, exible vehicles. In the first of these three tests, a full-span, aeroelastically scaled, wind-tunnel model of a joined-wing SensorCraft vehicle was mounted to a force balance to acquire a basic aerodynamic data set. In the second and third tests, the same wind-tunnel model was mated to a new, two-degree-of-freedom, beam mount. This mount allowed the full-span model to translate vertically and pitch. Trimmed flight at -10% static margin and gust load alleviation were successfully demonstrated. The rigid body degrees of freedom required that the model be own in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort. The balance and free ying wind-tunnel tests will be summarized. The design of the trim and gust load alleviation control laws along with the associated results will also be discussed.

  11. 基于模型预测控制的阵风减缓技术研究%Approach of Gust Load Alleviation Based on Model Prediction Control

    刘岳锋; 白俊强; 孙智伟


    针对传统控制方法在系统存在约束时性能下降的问题,采用了基于模型预测控制的阵风减缓方法。模型预测控制采用在线滚动优化策略,相比传统控制方法,能够应对由于约束和干扰等导致的系统性能恶化。系统以某大型飞机为例,对飞机进行了考虑阵风效应的动力学方程建模。分别采用模型预测和线性二次高斯控制方法设计阵风减缓控制系统,仿真结果表明,模型预测控制在无约束时性能与传统线性二次高斯控制基本一致;而当系统存在约束时,模型预测控制相比线性二次高斯控制器具有更优的性能。%Model prediction control technique is adopted in present analysis to solve the problem that the gust load alleviation system performance is influenced seriously by constraints.This method is based on receding optimization strategy.Comparing with traditional control laws,it can prevent worse performance which is induced by constraints,dis-turbance and so on.Some large aircraft is chosen and the state space form of aircraft gust model is proposed.The gust load alleviation system is de-signed by model predictive control and linear quad-ratic gauss method respectively,simulation result shows that the controller performance of model predictive control is almost the same as the linear quadratic gauss controller without constraints, while considering the constraints model predictive controller gets better performance than linear quadratic gauss controller.

  12. János Kádár as an Economic Reformist And Gustáv Husák As An Antireformist

    Horbulák Zsolt


    Full Text Available This paper deals with both political and economic history. The main task was to try to compare the attitude of Gustáv Husák and János Kádár about economic reforms in their own countries. The comparison was based on their lives, interests and personalities. Historical evaluation and biographical material was also used. Taking into account that the political circumstances were very similar, the root of the differences between the acts of these politicians had to be the result of individual factors. However, it cannot be denied that the difference between the development of Czechoslovakia and Hungary also played a significant role.

  13. Effects of establishment of mixed layer on a strong gust weather process%混合层建立对一次强阵风天气过程的影响

    汪靖; 赵玉洁; 吴振玲; 蔡子颖


    Based on the NCEP reanalysis data and conventionally observational data,influence mechanism of estab-lishment of mixed layer (ML)on a strong gust weather process on March 23,2012 in Tianjin was diagnosed and simulated .The results show that joint action of strong pressure and allobaric gradient in front of cold high is synop-tic background of formation of surface strong gusts.Strong gusts occur in the period of higher surface temperature, lower pressure and low relative humidity.In the afternoon,the hot and dry convection within the deep ML makes the upper-level momentum that is in the north side of upper jet easily propagate to ground layer effectively,which leads to enhancement of surface gusts.The establishment of deep ML is another reason leading to formation of strong surface gusts.Results simulated by a WRF model suggest that local intensity of the ML may cause local differences of downward propagation of momentum,which may be the important factor causing spatial differences of gusts intensity over Tianjin.%利用NCEP再分析资料和常规地面观测资料,分析混合层的建立对2012年3月23日天津地区强阵风天气过程的影响机理。结果表明:强气压梯度和强变压梯度的共同动力作用是地面强阵风形成的背景条件。强阵风出现在午后气温较高、湿度较低且地面气压较低的时段。午后深厚混合层内的干热对流使高空急流北侧下沉气流将动量下传至对流层中层后向近地面层进一步有效下传,导致地面阵风增大。深厚混合层的建立也是地面强阵风形成的一个重要原因。WRF模拟结果表明,局地混合层强度差异使高空动量下传产生局地差异,可能是天津各地区阵风强度存在空间差异的重要原因。

  14. Experimental investigation on the vertical gust response characteristics of the MAV with flexible structure%柔性翼微型飞行器垂直阵风响应特性的实验研究

    魏德宸; 史志伟; 彭仁明


    微型飞行器因其体积小、重量轻、使用灵活、成本低,广泛应用于军民领域的侦查、通讯、搜救等领域.在制约微型飞行器发展的诸多因素中,阵风对微型飞行器的稳定、安全飞行影响很大.在南京航空航天大学非定常风洞内,研制了一套垂直阵风装置,进行了垂直阵风的流场测试.设计制作了一种柔性翼徽7型飞行器,并制作了刚性翼与其对比,在国内首次进行了微型飞行器垂直阵风实验.结果表明:柔性翼能够提高微型飞行器的失速迎角,且具有更好的纵向稳定性,有一定的垂直阵风缓和能力,有利于安全、稳定飞行.%Micro aerial vehicle (MAV) is a new type of aircraft, which has traits of mini volume , light weight, higher flexibility, low cost, etc. So MAV could be extensively applied to military and civil fields, including reconnaissance, communication, and rescue, Concerned with several obstacles of restricting the MAV development, the gust is the most important factor that affects the MAV to flight safely and steadily. The equipment for generating vertical gust is developed and an angle surveying method which could be applied on the vertical gust flow field is studied. Then a rigid wing MAV and a flexible wing MAV of a flying wing configuration are designed and fabricated. The vertical gust experiment for MAV is carried out in unsteady wind tunnel of NUAA. The results'show that the flexible wing can increase the stall angle of attack. At the same time, it has better longitudinal stability. The flexible wing has the ability of alleviating the effects of vertical gust which benefits to safe and steady flight.

  15. Development of Aeroservoelastic Analytical Models and Gust Load Alleviation Control Laws of a SensorCraft Wind-Tunnel Model Using Measured Data

    Silva, Walter A.; Vartio, Eric; Shimko, Anthony; Kvaternik, Raymond G.; Eure, Kenneth W.; Scott,Robert C.


    Aeroservoelastic (ASE) analytical models of a SensorCraft wind-tunnel model are generated using measured data. The data was acquired during the ASE wind-tunnel test of the HiLDA (High Lift-to-Drag Active) Wing model, tested in the NASA Langley Transonic Dynamics Tunnel (TDT) in late 2004. Two time-domain system identification techniques are applied to the development of the ASE analytical models: impulse response (IR) method and the Generalized Predictive Control (GPC) method. Using measured control surface inputs (frequency sweeps) and associated sensor responses, the IR method is used to extract corresponding input/output impulse response pairs. These impulse responses are then transformed into state-space models for use in ASE analyses. Similarly, the GPC method transforms measured random control surface inputs and associated sensor responses into an AutoRegressive with eXogenous input (ARX) model. The ARX model is then used to develop the gust load alleviation (GLA) control law. For the IR method, comparison of measured with simulated responses are presented to investigate the accuracy of the ASE analytical models developed. For the GPC method, comparison of simulated open-loop and closed-loop (GLA) time histories are presented.

  16. Aeroelastic response for straight wing with high aspect ratio due to sharp edge gust%锐边突风对大展弦比机翼的气动弹性响应影响

    刘伏虎; 马晓平


    基于Theodorsen非定常气动力理论,以大展弦比均匀直机翼为研究对象,建立了系统的气动弹性响应方程.选取二阶弯曲和二阶扭转模态,采用V-g法求解了系统的颤振速度.基于Kussner函数,建立了锐边突风系统模型,并推导了在弯曲和扭转模态阶数为Nw和Na下的系统状态方程,仿真研究了加入突风后系统的气动弹性响应.结果表明,加入突风后翼尖响应振幅增大.%Based on Theodorsen unsteady aerodynamics theory, the equation of aeroelastic response for straight wing with high aspect ratio is established. Flutter speed is determined for two bending modes and two torsional modes using V-g methods. The sharp edge gust system model is established and the system state equations are derived with Nw bending modes and Na torsional modes wing systems based on the function Kussner. The aeroelastic response of system shows that the amplitude oscillation becomes higher. The modeling method may offer reference for research of gust response.

  17. 基于偶极子的连续突风响应改进算法%An Improved Algorithm of Continuous Gust Response Based on Doublet-Lattice Method

    张俐娜; 詹浩


    Aim. The introduction of the full paper reviews some relevant papers in the open literature, points out what we believe to be their shortcomings, and then proposes what we believe to be an improved algorithm mentioned in the title. Sections 1,2, and 3 explain our improved algorithm; their core consists of; "The increment of kernel function molecules is matched by quartic polynomial, which relaxes the restriction of the span-chord ratio in the calculation of unsteady aerodynamic force. It investigates the effect to the computation of an elastic wing gust response by the span-chord ratio and the number of aerodynamic grids. " The response results, obtained with classical algorithm and our improved one respectively, are presented in Figs. 4 through 9 and Tables 2 and 3. These results and their analysis show preliminarily that our improved algorithm is indeed feasible and effective.' This algorithm reduces the number of grids used in the high frequency aerodynamic force computation so that the calculating time and stored space are reduced; in addition, the accuracy is higher. It benefits the investigation of gust control and alleviation.%文章阐述了基于亚音速偶极子网格法的连续突风响应改进算法.采用四次多项式来近似增量核函数分子,放宽了非定常气动力计算中对气动网格展弦比的限制.以弹性机翼结构为例,探讨了气动网格单元展弦比和网格数对连续突风响应计算结果的影响.对比经典算法、改进算法计算结果,表明改进算法可行有效.该算法减少了高频气动力计算中所需的展向网格数目,可以节约计算时间或存储空间并提高计算精度,对突风控制与减缓研究有一定的指导作用.

  18. Importance sampling of severe wind gusts

    Bos, R.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.


    An important problem that arises during the design of wind turbines is estimating extreme loads with sufficient accuracy. This is especially difficult during iterative design phases when computational resources are scarce. Over the years, many methods have been proposed to extrapolate extreme load d

  19. Importance sampling of severe wind gusts

    Bos, R.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.


    An important problem that arises during the design of wind turbines is estimating extreme loads with sufficient accuracy. This is especially difficult during iterative design phases when computational resources are scarce. Over the years, many methods have been proposed to extrapolate extreme load d

  20. Extreme Vertical Gusts in the Atmospheric Boundary Layer


    with tornadogenesis [Mueller and Carbone (1987), Wilson (1986) and McCaul and Bluestein (1986)], although tornadoes are part of the hazard of...Burns, C. Nappo, R. Banta, R. Newsom and J. Cuxart (2002). CASES-99: A comprehensive investigation of the stable nocturnal boundary layer. Bulletin of...Meteorology 64(1-2): 55-74. Wilson , J. W. (1986). Tornadogenesis by nonprecipitation induced wind shear lines. Monthly Weather Review 114(2): 270-284

  1. Passive Gust Alleviation for a Flying Wing Aircraft


    66 E.1 CATIA Surface Model...with 20% of the volume measured in CATIA reserved to take into account the structure and systems. The final fuel and total mass distributions are...for the calculations, such as the wing box height, the rib pitch, were obtained from CATIA . The laminate engineering properties were derived from

  2. 5m RPV for Exploring Joined Wing Gust Response


    USED FOR DETERMINING TSFC OF JETCAT ENGINES ............................... 5 FIGURE 3 - LAMINATE SHEETS PRODUCED USING VARTM ...6 FIGURE 4 - LAMINATE SHEET IN VARTM PROCESS...spars and bulkheads. All of the required laminate sheets are produced using the Vacuum Assisted Resin Transfer Method ( VARTM ), some of which are shown

  3. No nos gustó: el transeúnte

    Daniel Samper Pizano


    Full Text Available Entendemos nosotros la crítica de arte -especialmente la crítica literaria- como un intento de interpretación o valoración objetiva de una serie de elementos subjetivos. Porque aunque en ocasiones se preste para una confrontación de cuestiones objetivas -sería el caso de los análisis gramaticales en una obra- la crítica será siempre un encuentro entre algo subjetivo, como es la obra literaria, con una pretendida visión objetiva -como es su análisis- de otro elemento subjetivo -como es el concepto del crítico-.

  4. Wind gust measurements using pulsed Doppler wind-lidar: comparison of direct and indirect techniques

    model, driven by the Doppler lidar measurements, which uses a non-linear particle filter to estimate the small-scale turbulent fluctuations. The first results show that the reconstruction method can reproduce the wind speed maxima measured by the sonic anemometer if a low-pass filter with a cut......-off frequency similar to the lidar measurement frequency is applied to the sonic data. These results from the reconstructed wind are better than the maxima derived directly from the wind lidar measurements. However, the maxima of the raw sonic anemometer signal are still higher than the maxima...

  5. Experimental Model Based Feedback Control for Flutter Suppression and Gust Load Alleviation Project

    National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes an R&D effort to develop an Experimental Model Based Feedback Control (EMBFC) Framework for the flutter suppression and...

  6. Gust response and cross wind performance of a hovercraft with vertical wings

    Kawahata, Nagakatu; Miura, Yosihiro

    The configurations of a radio-controlled hovercraft model with vertical wings are presented. The flight performance in cross wind is evaluated, and the difference between the target point and visual angular error is addressed.

  7. Gust Wind Effects on Stability and Ride Quality of Actively Controlled Maglev Guideway Systems

    Dong-Ju Min


    Full Text Available The purpose of this paper is to present a framework to analyze the interaction between an actively controlled magnetic levitation vehicle and a guideway structure under gusty wind. The equation of motion is presented for a 30-dof maglev vehicle model consisting of one cabin and four bogies. In addition, a lateral electromagnetic suspension (EMS system is introduced to improve the running safety and ride quality of the maglev vehicle subjected to turbulent crosswind. By using the developed simulation tools, the effects of various parameters on the dynamic response of the vehicle and guideway are investigated in the case of the UTM maglev vehicle running on a simply supported guideway and cable-stayed guideway. The simulation results show that the independent lateral EMS and associated control scheme are definitely helpful in improving the running safety and ride quality of the vehicle under gusty wind. In the case of the cable-stayed guideway, at low wind speed, vehicle speed is the dominant factor influencing the dynamic responses of the maglev vehicle and the guideway, but at wind speed over 10 m/s, wind becomes the dominant factor. For the ride quality of the maglev vehicle, wind is also the most influential factor.

  8. 14 CFR Appendix G to Part 25 - Continuous Gust Design Criteria


    ... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Pt. 25, App. G Appendix G to Part 25... appendix. (3) For each of the load and stress quantities selected, the frequency of exceedance must be.... y=net value of the load or stress. Yone=g=value of the load or stress in one-g level flight. N(y...

  9. Stabilization and trajectory tracking control for underactuated quadrotor helicopter subject to wind-gust disturbance

    Mohd Ariffanan Mohd Basri; Abdul Rashid Husain; Kumeresan A Danapalasingam


    The control of quadrotor helicopter has been a great challenge for control engineers and researchers since quadrotor is an underactuated and a highly unstable nonlinear system. In this paper, the dynamic model of quadrotor has been derived and a so-called robust optimal backstepping control (ROBC) is designed to address its stabilization and trajectory tracking problem in the existence of external disturbances. The robust controller is achieved by incorporating a prior designed optimal backstepping control (OBC) with a switching function. The control law design utilizes the switching function in order to attenuate the effects caused by external disturbances. In order to eliminate the chattering phenomenon, the sign function is replaced by the saturation function. A new heuristic algorithm namely Gravitational Search Algorithm (GSA) has been employed in designing the OBC. The proposed method is evaluated on a quadrotor simulation environment to demonstrate the effectiveness and merits of the theoretical development. Simulation results show that the proposed ROBC scheme can achieve favorable control performances compared to the OBC for autonomous quadrotor helicopter in the presence of external disturbances.

  10. Wind‐gust parametrizations at heights relevant for wind energy: a study based on mast observations

    Suomi, I.; Vihma, T.; Gryning, Sven-Erik;


    gustiness conditions were studied using observations from two coastal/archipelago weather masts in the Gulf of Finland (northern Europe) with observation heights between 30 and 143 m. Only moderate and strong wind cases were addressed. Both masts were located over relatively flat terrain but the local...

  11. Bibliography of Aircraft Gust Measurements in Australia and of Some Related Topics,


    cold fronts (b) deep southerly streams. Three examples were given, (1) A Qantas flying boat encountered a line squall near Rathmines, the aircraft...Viscount Aircraft VH-TVC, operated by Australian National Airways Pty. Ltd. Air Navigation Regulations, Accident Inquiry, August 1962. This is the report...only Australian data included in this report are the QANTAS Super Constellation data already reported by Heath-Smith (1959), and the 17 hours of

  12. Computation of Gust-Cascade Interaction Using the CE/SE Method

    Wang, X.-Y.; Himansu, A.; Chang, S.-C.; Jorgenson, P. C. E.


    The problem 2 in Category 3 of the 4th Computational Aeroacoustic(CAA) Workshop is solved using the space-time conservation element and solution element (CE/SE) method. This problem models rotor-stator interaction in a 2D cascade. It involves complex geometries and flow physics including vortex shedding and acoustic radiation. The parallel version of the 2D nonlinear Euler solver is used with an unstructured triangular mesh to solve this problem. The Giles approach is incorporated with the CE/SE method to handle non-equal pitches of the rotor and stator. Validation on the Giles approach is performed using Problem 3.1 in the 2nd CAA Workshop. The space-time CE/SE method is a finite volume method with second-order accuracy in both space and time. The flux conservation is enforced in both space and time instead of space only. It has low numerical dissipation and dispersion errors. It uses simple non-reflecting boundary conditions and is compatible with unstructured meshes. It is simple, flexible, and generate reasonably accurate solutions. The CE/SE method has been successfully applied to solve numerous practical problems, especially aeroacoustic problems. Some preliminary numerical results of the benchmark problem 3.2 of the 4th CAA Workshop are shown. The steady-state pressure contour is plotted. The mean pressure distribution on the blade surface is compared with Turbo solution showing a good agreement. The sound pressure level versus the rotor harmonic n at the six designated positions on the blade surface, three locations at inlet plane, and three locations at the outlet plane are plotted. It can be seen that the acoustic response exists only at the excitation frequencies (n = 1,2,3). On the blade surface, the acoustic wave at n = 1 is dominant, while at the inlet and outlet planes, the sound pressure level at n = 2 becomes the largest, which is similar to the results presented. The distribution of sound pressure level at different spatial modes along the z- direction is plotted for n = 1,2,3, respectively. It shows that the spatial modes m = -32 and 22 at n = 1 exponentially decay, and the spatial modes m = 10 at n = 2, m = -42 and 12 at n = 3 propagate both upstream and downstream, which agrees with the prediction based on the linearized theory. Some oscillations are observed, which needs to be investigated further. In the final paper, the numerical results will be compared with a frequency-domain solver LINFLUX solution if it is available.

  13. Horizontal gust response of `Tatara Bridge` under construction; `Tatara ohashi` kasetsuji no taifu anteisei

    Matsuda, K.; Iwasaki, T.; Tokushige, M.; Toriumi, R. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)


    Wind tunnel tests of a long-span cable-stayed bridge under construction were conducted with two types of turbulent boundary layer simulations. The level of agreement between the wind tunnel measurements and a wind buffeting analysis varied with the type of turbulent boundary layer. An investigation of this behavior found that the aerodynamic admittance used in the buffeting analysis was different from the measured aerodynamic admittance. Past research showed that buffeting analysis based on strip theory, which assumes a spanwise correlation between the fluctuating wind velocity and the fluctuating aerodynamic loads, does not always hold. (author)

  14. Effects of rotating frame turbulence and dynamic stall on gust response of helicopter blades

    Madhavan, R.; Gaonkar, G. H.


    The instantaneous or frequency-time spectrum of rotating frame turbulence (RFT) is presented. This spectrum makes it possible to predict the transfer of energy with respect to frequencies and the periodically varying nonstationarity with respect to time. Attention is also given to the RFT effects on the response statistics of an isolated rotor blade for low-advance-ratio and low-altitude conditions. It is noted that spectral density, rms values, and threshold-crossing expectation rates are significantly influenced by RFT.

  15. Random gust response statistics for coupled torsion-flapping rotor blade vibrations.

    Gaonkar, G. H.; Hohenemser, K. H.; Yin, S. K.


    An analysis of coupled torsion-flapping rotor blade vibrations in response to atmospheric turbulence revealed that at high rotor advance ratios anticipated for future high speed pure or convertible rotorcraft both flapping and torsional vibrations can be severe. While appropriate feedback systems can alleviate flapping, they have little effect on torsion. Dynamic stability margins have also no substantial influence on dynamic torsion loads. The only effective means found to alleviate turbulence caused torsional vibrations and loads at high advance ratio was a substantial torsional stiffness margin with respect to local static torsional divergence of the retreating blade.

  16. Urban Turbulence and Wind Gusts for Micro Air Vehicle Bio-inspired Designs


    Kundu , P. K. Fluid Mechanics , Academic Press, Inc.: San Diego, CA, 1990, pp. 638. Nelson, M. A.; Pardyjak, E. R.; Klewicki, J. C.; Pol, S. U...the fluid . It is heavily influenced by boundary conditions. There is no official definition of turbulence. Most modern textbooks just list some of...the properties of turbulent flow ( Kundu , 1990; Shivamoggi, 1998) such as the following: • Large fluctuations about the mean values • Enhanced rates

  17. Gust Response of a Light, Single-Engined, High-Wing Aircraft.


    Airworthiness Division .../cont. DISTRIBUTION (CONT.) Statutory & State Authorities and Industry Trans-Australia Airlines, Library Qantas Airways Limited ...i.e. at Log 71 = -1.39. However, for comparing the relative trends between the various cases, extending the cut-off limit to Log f 1-1 .00 (as done in...sted limitations thould be referred through ASDIS, Defence Infonmation Servine Branch DOertment of Defence, Cempbli Park, CANBERRA ACT 201 13.a. lThi

  18. Wind Tunnel Model and Test to Evaluate the Effectiveness of a Passive Gust Alleviation Device for a Flying Wing Aircraft


    Bisplinghoff, R. L., Ashley, H. and Halfman, R. L. (1955), Aeroelasticity, Addison - Wesley Publishing Co., Inc. [12] Banerjee, J. R. (1984...and Halfman, H. (1983), Aeroelasticity, Addison Wesley Publishing Co.Inc., Cambridge, Mass. [74] Samikkannu, R. and Upadhya, A. R. (2011), "Wind

  19. Distributed, Passivity-Based, Aeroservoelastic Control (DPASC) of Structurally Efficient Aircraft in the Presence of Gusts Project

    National Aeronautics and Space Administration — Control of extremely lightweight, long endurance aircraft poses a challenging aeroservoelastic (ASE) problem due to significantly increased flexibility, and...

  20. Horizontal gust response of 'Tatara Bridge' under construction. 'Tatara ohashi' kasetsuji no taifu anteisei

    Matsuda, K.; Iwasaki, T.; Tokushige, M.; Toriumi, R. (Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan))


    Wind tunnel tests of a long-span cable-stayed bridge under construction were conducted with two types of turbulent boundary layer simulations. The level of agreement between the wind tunnel measurements and a wind buffeting analysis varied with the type of turbulent boundary layer. An investigation of this behavior found that the aerodynamic admittance used in the buffeting analysis was different from the measured aerodynamic admittance. Past research showed that buffeting analysis based on strip theory, which assumes a spanwise correlation between the fluctuating wind velocity and the fluctuating aerodynamic loads, does not always hold. (author)

  1. CURRENT DIRECTION, WIND GUST and other data from FIXED PLATFORM from 1974-02-23 to 1974-04-25 (NCEI Accession 7601418)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and other data were collected from fixed platforms from 23 February 1974 to 25 April 1974. Data were collected by Oregon State University (OSU) as part...

  2. November 2009 tropical cyclone Phyan in the eastern Arabian Sea: Oceanic response along west India coast and Kavaratti lagoon

    Joseph, A.; Desai, R.G.P.; Mehra, P.; VijayKumar, K.; Agarvadekar, Y.; Ryan, L.; Rivankar, P.; Viegas, B.

    and finally made landfall at the northwest coast of India, is examined based on time-series measurements of seasurface wind (U sub(10)), gust, gust factor, barometric pressure, precipitation, atmospheric temperature, SST, and significant wave height from...

  3. Application of constrained stochastic simulation to determine the extreme response of wind turbines

    Bierbooms, W.A.A.M.; Peeringa, J.


    Up to now just deterministic gust shapes are specified in standards; e.g. the Extreme Operating Gust (IEC) is given by a Mexican hat like shape. In this paper gust shapes will be determined by application of so-called constrained stochastic simulation. This method specifies how to efficiently genera

  4. The Australian Implementation of AMDAR/ACARS (Aircraft Meteorological Data Relay/ARINC Communications Addressing and Reporting System) and the Use of Derived Equivalent Gust Velocity as a Turbulence Indicator,


    34.- Woodfield A.A. 1982 Windshear analysis by the RAE from British Airways B747 Flight MI Records. RAE Bedford paper dated 6 April 1982. Woodfield A.A... Qantas Airways Limited Aircraft Evaluation Engineer Director, Flight Operations (Capt. A I Terrell) Capt. G Molloy % • ;I... Capt. B Lofthouse K Lewis...REFERENCE TO THE 4 -- BOEING 767 4. ERROR ANALYSIS 6 5. RECOMMENDATION 7 REFERENCES 8 APPENDICES 1. THE AIRCRAFT METEOROLOGICAL DATA RELAY (AMDAR) SYS

  5. VAR Approach for 3-D Gust Wind Spectral Modeling and Simulation of Wind Turbine%风力发电机三维阵风谱建模与仿真的向量自回归法

    穆安乐; 刘宏昭; 张彦斌; 张明洪


    针对风力发电机空气动力学和结构分析的要求,提出一种新的向量自回归(vector autoregressive,VAR)三维阵风速 场仿真方法.在常规自回归(autoregressive,AR)法建模的基础上,根据维纳-辛钦公式,由协方差向量和功率谱求出自回归系数向量.其中输入参数为单点Davenport阵风功率谱(power spectral density, PSD)和互相关函数.基于此,推导出多维风速时程模型.算例采用一个3 桨叶风力发电机所在风场,其中心高为H=30 m,风力机转子半径R=11.6 m,沿风力机叶尖扫过圆周均布12个点,取其中3点进行仿真,并采用Burg算法进行功率谱估计.采样频率0~0.9 Hz,频率采用点数N=1800,时间间隔0.1s.仿真结果表明,适当选取采样频率点数与时间间隔,可以在保证模拟功率谱计算精度的同时,具有快速高效的特点,弥补了传统方法在模拟三维风速时耗时长、精度低的缺点.

  6. WAVE HEIGHT - SIGNIFICANT, WIND GUST and other data from FIXED PLATFORM in the Gray's Reef National Marine Sanctuary, Gulf of Mexico and other waters from 1998-08-01 to 1998-08-31 (NODC Accession 9800157)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind wave spectra and other data were collected from FIXED PLATFORMS. Data were collected by the National Data Buoy Center (NDBC) from 01 August 1998 to 31 August...

  7. Preparation, transport and disposal of ash from coal-fired power plant Kosovo B in the form of dense hydromixture; Priprema, transport i deponovanje pepela termoelektrane Kosovo B u vidu guste hidromesavine

    Drazovic, D.; Markovic, Z.; Stjepanovic, P.; Todorovtc, D. [Rudarski Institute, Beograd (Yugoslavia)


    The transportation of ash and slag from coal-fired power plants is mainly hydraulic. Until the eighties the most frequently applied technology was the transportation of ash and slag in the form of diluted hydromixture (concentration of solids below 10%). This method of ash and slag transportation became a rule in Yugoslavia's coal-fired power plants. It was not until 1988 that the transportation of dense hydromixture was introduced in the coal-fired power plant Gacko. This technology was not applied on account of its transportation advantages, but due to specific ash features that determine the conditions of disposal. Namely, the density of hydromixture is important for the solidification of disposed material. Considering the chemical and mineralogical properties of ash the same system was applied in the coal-fired power plant Kosovo B. In this paper two technological lines were installed and put to use in actual industrial conditions, and the results obtained indicate that all the designed parameters have been confirmed in practice and that the application of this technology has proven to be profitable in many ways. 7 refs., 8 figs., 13 tabs.

  8. An analytical study of the response of a constant-attitude aircraft to atmospheric turbulence

    Smetana, F. O.; Carden, R. K.


    A light airplane equipped with an automatic control system which drives large wing flaps and the stabilator so as to produce a constant pitch attitude in all flight modes was analyzed for its response to a specific gust. The aircraft was also equipped with a bank-angle steering, zero sideslip automatic control system which was studied for its effectiveness in suppressing a specific lateral gust. The gusts were assumed to be comprised of 200 lateral and 400 vertical sinusoids. Each was used to excite the controlled aircraft and the time response to the sum of all sinusoids was plotted. The assumption was that the gust may be treated as stationary in space but variable in time rather than the reverse. Results indicate that such a control system can suppress vertical gusts up to the limit of control authority. Either the lateral accelerations or the yawing velocity response to lateral gusts can be suppressed with this system but not both simultaneously.

  9. Information retrieval from wide-band meteorological data - An example

    Adelfang, S. I.; Smith, O. E.


    The methods proposed by Smith and Adelfang (1981) and Smith et al. (1982) are used to calculate probabilities over rectangles and sectors of the gust magnitude-gust length plane; probabilities over the same regions are also calculated from the observed distributions and a comparison is also presented to demonstrate the accuracy of the statistical model. These and other statistical results are calculated from samples of Jimsphere wind profiles at Cape Canaveral. The results are presented for a variety of wavelength bands, altitudes, and seasons. It is shown that wind perturbations observed in Jimsphere wind profiles in various wavelength bands can be analyzed by using digital filters. The relationship between gust magnitude and gust length is modeled with the bivariate gamma distribution. It is pointed out that application of the model to calculate probabilities over specific areas of the gust magnitude-gust length plane can be useful in aerospace design.

  10. Sources of Wind Variability at a Single Station in Complex Terrain During Tropical Cyclone Passage


    easterly and westerly directions. ......................50 Figure 38. Directional wind difference of the gust wind direction relative to the sustained...Southerly winds. That is, easterly and westerly winds had occurred much more frequently than any other directions during 1990 to 2000 (Figure 13...points of N and S, and lower gust factors from more easterly and westerly directions. Note that a strong majority of gust winds are in the same

  11. O-2A Aircraft Sea Flight Loads Recording Program


    When Government drawings, specifications, or other data are used for niy purpose other than in connection with a definitely related Government...Exceedances per Nautical Mile for Derived Equivalent Gust Velozity , Ude, by Altitude ........ 29 14 Exceedances per Nautical Mile for Derived Gust Velocity...period are detailed later in this report. To present the data reflecting the manuver and gust load spectra, the data processing consisted of

  12. Sphere anemometer - a faster alternative solution to cup anemometry

    Hölling, M.; Schulte, B.; Barth, S.; Peinke, J.


    We present an anemometer technique characterized by an instrument in a sealed enclosure without moving parts. Measurements taken with our improved sphere anemometer in comparison to cup anemometer and hot-wire anemometer data subjected to wind gusts are discussed. The hot-wire anemometer serves as a reference with high temporal and spacial resolution. A manually driven "gust generator" produced gusts at low frequencies of about 1Hz. All measurements were carried out in the wind tunnel at the University of Oldenburg.

  13. Analysis of VGH data from two types of four-engine airplanes in commercial cargo service

    Healy, F. M.


    Data are presented for derived gust velocities and for incremental normal accelerations due to gusts, maneuvers, and landing impacts. The data were obtained from NASA VGH recorders installed on three four-engine cargo airplanes operated by three airlines. Continental United States and trans-Pacific routes were covered.

  14. Strong wind climatic zones in South Africa

    Kruger, AC


    Full Text Available In this paper South Africa is divided into strong wind climate zones, which indicate the main sources of annual maximum wind gusts. By the analysis of wind gust data of 94 weather stations, which had continuous climate time series of 10 years...

  15. 14 CFR 25.345 - High lift devices.


    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High lift devices. 25.345 Section 25.345... STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Flight Maneuver and Gust Conditions § 25.345 High lift...) A head-on gust of 25 feet per second velocity (EAS). (c) If flaps or other high lift devices are to...

  16. Extreme wind conditions for a Danish offshore site

    Hansen, Kurt S.


    This paper presents an analysis of extreme wind speed gust values measured at a shallow water offshore site and at a coastal onshore site in Denmark. An estimate of 50-year extreme values has been evaluated using a new statistical method. In addition a mean gust shape is determined, based on a la...

  17. Joint Agency Turbulence Experiment.


    Time Series of Aircraft Longitudinal Gust Data For Penetration 1 on 1 July 1981 63 C5. Time Series of Turbulence Severity Estimates Derived From 400 m...spectral analysis of aircraft longitudinal gust data is shown in Figure B1. Figure B2 shows a modeled turbulence field. The model displays the expected...centered about Location C o %-. -. °,4 0- S E - oo -12 -4 - to 20 so O so s 7D -U. TIME (sec) Figure C4. Time Series of Aircraft Longitudinal Gust Data

  18. ZEUS-DO: A Design Oriented CFD-Based Unsteady Aerodynamic Capability for Flight Vehicle Multidisciplinary Configuration Shape Optimization Project

    National Aeronautics and Space Administration — In practically all air-vehicle MDO studies to date involving configuration shape optimization, dynamic Aeroservoelastic constraints had to be left out. Flutter, gust...

  19. Tower Winds - Cape Kennedy

    National Oceanic and Atmospheric Administration, Department of Commerce — Digitized data taken from Wind Gust Charts. Record contains hourly wind directions and speed with a peak wind recorded at the end of each day. Sorted by: station,...

  20. A marine meteorological data acquisition system

    Desai, R.G.P.; Desa, E.; Vithayathil, G.

    and was interfaced to a variety of sensors to assess relative performance of vector averaged winds, gusts, air temperature and barometric pressure. The inter-comparison of field data obtained from various sensors and their laboratory calibration were carried out...

  1. Modeling and investigation of Gulf El-Zayt wind farm for stability studying during extreme

    Omar Noureldeen


    Full Text Available This paper investigates the impact of extreme gust wind as a case of wind speed variation on a wind farm interconnected electrical grid. The impact of extreme gust wind speed variation on active and reactive power of the wind farms is studied for variable speed wind farm equipped with Doubly Fed Induction Generators (DFIGs. A simulation model of the under implementation 120 MW wind farm at Gulf El-Zayt region, Red Sea, Egypt, is simulated as a case study. A detailed model of extreme gust wind speed variation is implemented and simulated, using MATLAB/Simulink toolbox, based on International Electrotechnical Commission IEC 61400-1 and climate characteristic of Gulf El-Zayt site. The simulation results show the influence of different extreme gust wind speed variations on the fluctuation of active power and reactive power at the Point of Common Coupling (PCC of the studied wind farm.

  2. An analysis of airspeed, altitude, and acceleration data obtained from a twin-engine transport airplane operated over a feeder-line route in the Rocky Mountains

    Copp, Martin R; Fetner, Mary W


    Time-history data of airspeed, altitude, and acceleration obtained with the NACA VGH recorder from a twin-engine airplane operated by a regional feeder airline in the Rocky Mountains are evaluated to determine the magnitude and frequency of occurrence of gusts and gust accelerations and the operating airspeeds and altitudes. The results obtained are compared with the results previously obtained from a representative short-haul and long-haul operation.

  3. Nuclear Blast Response Computer Program. Volume I. Program Description.



  4. Analysis Regarding the Effects of Atmospheric Turbulence on Aircraft Dynamics

    Gabriela STROE


    Full Text Available This paper will analyze the Gust Load Alleviation (GLA systems which can be used to reduce the effects of atmospheric turbulences generated by wind gusts on vertical acceleration of aircraft. Their purpose is to reduce airframe loads and to improve passenger comfort. The dynamic model of the aircraft is more realistic than a rigid-body model, since it includes the structural flexibility; due to its complexity, such model can make feedback control design for gust load alleviation more challenging. The gust is generated with the Dryden power spectral density model. This kind of model lends itself well to frequency-domain performance specifications in the form of the weighting functions. Two classical analytical representations for the power spectral density (PSD function of atmospheric turbulence as given by Von Kármán and Dryden, were used. The analysis is performed for a set of specified values for flight velocity and altitude (as test cases, with different gust signals that must be generated with the required intensity, scale lengths and PSD functions.

  5. Influence of vane sweep on rotor-stator interaction noise

    Envia, Edmane; Kerschen, Edward J.


    The influence of vane sweep in rotor-stator interaction noise is investigated. In an analytical approach, the interaction of a convected gust representing the rotor viscous wake, with a cascade of cascade of finite span swept airfoils, representing the stator, is analyzed. The analysis is based on the solution of the exact linearized equations of motion. High frequency convected gusts for which noise generation is concentrated near the leading edge of airfoils is considered. In a preliminary study, the problem of an isolated finite span swept airfoil interacting with a convected gust is analyzed. Results indicate that sweep can substantially reduce the farfield noise levels for a single airfoil. Using the single airfoil model, an approximate solution to the problem of noise radiation from a cascade of finite span swept airfoils interacting with a convected gust is derived. A parametric study of noise generated by gust cascade interaction is carried out to assess the effectiveness of vane sweep in reducing rotor-stator interaction noise. The results show that sweep is beneficial in reducing noise levels. Rotor wake twist or circumferential lean substantially influences the effectiveness of vane sweep. The orientation of vane sweep must be chosen to enhance the natural phase lag caused by wake lean, in which case rather small sweep angles substantially reduce the noise levels.

  6. Survey on effect of surface winds on aircraft design and operation and recommendations for needed wind research

    Houbolt, J. C.


    A survey of the effect of environmental surface winds and gusts on aircraft design and operation is presented. A listing of the very large number of problems that are encountered is given. Attention is called to the many studies that have been made on surface winds and gusts, but development in the engineering application of these results to aeronautical problems is pointed out to be still in the embryonic stage. Control of the aircraft is of paramount concern. Mathematical models and their application in simulation studies of airplane operation and control are discussed, and an attempt is made to identify their main gaps or deficiencies. Key reference material is cited. The need for better exchange between the meteorologist and the aeronautical engineer is discussed. Suggestions for improvements in the wind and gust models are made.

  7. Rational Calibration of Four IEC 61400-1 Extreme External Conditions

    Larsen, Gunner Chr.; Hansen, Kurt Schaldemose


    Based on a set of asymptotic statistical models on closed form this paper presents a rational and consistent calibration of four extreme external conditions defined in the International Electrotechnical Commission (IEC) 61400-1 standard: extreme operating gust, extreme wind shear, extreme coherent...... gust with direction change and extreme wind direction change. These four extreme external conditions are used in the definition of six of the IEC 61400-1 ultimate load cases. The statistical models are based on simple and easily accessible mean wind speed and turbulence characteristics...... of the atmospheric boundary layer. Using the wind climate characteristics prescribed in the IEC 61400-1 standard as input to the set of statistical models ensures consistency between the specified wind climate and the proposed extreme gust magnitudes. Differences and equalities between the present IEC specifications...

  8. Relevant Criteria for Testing the Quality of Turbulence Models

    Frandsen, Sten; Jørgensen, Hans E.; Sørensen, John Dalsgaard


    turbines when seeking wind characteristics that correspond to one blade and the entire rotor, respectively. For heights exceeding 50-60m the gust factor increases with wind speed. For heights larger the 60-80m, present assumptions on the value of the gust factor are significantly conservative, both for 3......Seeking relevant criteria for testing the quality of turbulence models, the scale of turbulence and the gust factor have been estimated from data and compared with predictions from first-order models of these two quantities. It is found that the mean of the measured length scales is approx. 10......% smaller than the IEC model, for wind turbine hub height levels. The mean is only marginally dependent on trends in time series. It is also found that the coefficient of variation of the measured length scales is about 50%. 3sec and 10sec pre-averaging of wind speed data are relevant for MW-size wind...

  9. Test of a trail cryogenic balance in the ONERA T2 wind tunnel

    Blanchard, A.; Seraudie, A.; Plazanet, M.; Payry, M. J.


    The three component cryogenic balance designed and manufactured by the ONERA Large Means Directorate, was equipped with a light alloy schematic model and tested at the end of 1984 at the T2 wind tunnel in gusts at low temperatures up to 120 K. The tests pertained to the impact of the cryogenic conditions on the behavior of extensometric bridges while cooling the balance-model system mounted in the conditioning device and during gusts with models in the test section. A few tests with thermal disequilibrium between the flow and balance made it possible to confirm the proper operation in the range 120 to 300 K. This gust system showed that the balance, which was well compensated thermally, may be used in T2 with and without precooling. For any thermal gradient, the analysis was always performed with the same matrices and aerodynamic coefficients were obtained with the same precision.

  10. Roll paper pilot. [mathematical model for predicting pilot rating of aircraft in roll task

    Naylor, F. R.; Dillow, J. D.; Hannen, R. A.


    A mathematical model for predicting the pilot rating of an aircraft in a roll task is described. The model includes: (1) the lateral-directional aircraft equations of motion; (2) a stochastic gust model; (3) a pilot model with two free parameters; and (4) a pilot rating expression that is a function of rms roll angle and the pilot lead time constant. The pilot gain and lead time constant are selected to minimize the pilot rating expression. The pilot parameters are then adjusted to provide a 20% stability margin and the adjusted pilot parameters are used to compute a roll paper pilot rating of the aircraft/gust configuration. The roll paper pilot rating was computed for 25 aircraft/gust configurations. A range of actual ratings from 2 to 9 were encountered and the roll paper pilot ratings agree quite well with the actual ratings. In addition there is good correlation between predicted and measured rms roll angle.

  11. Microburst nowcasting applications of GOES

    Pryor, Kenneth L


    Recent testing and validation have found that the Geostationary Operational Environmental Satellite (GOES) microburst products are effective in the assessment and short-term forecasting of downburst potential and associated wind gust magnitude. Two products, the GOES sounder Microburst Windspeed Potential Index (MWPI) and a new bi-spectral GOES imager brightness temperature difference (BTD) product have demonstrated capability in downburst potential assessment. In addition, a comparison study between the GOES-R Convective Overshooting Top (OT) Detection and MWPI algorithms has been completed for cases that occurred during the 2007 to 2009 convective seasons over the southern Great Plains. Favorable results of the comparison study include a statistically significant negative correlation between the OT minimum temperature and MWPI values and associated measured downburst wind gust magnitude. The negative functional relationship between the OT parameters and wind gust speed highlights the importance of updraft s...

  12. B-737 Linear Autoland Simulink Model

    Belcastro, Celeste (Technical Monitor); Hogge, Edward F.


    The Linear Autoland Simulink model was created to be a modular test environment for testing of control system components in commercial aircraft. The input variables, physical laws, and referenced frames used are summarized. The state space theory underlying the model is surveyed and the location of the control actuators described. The equations used to realize the Dryden gust model to simulate winds and gusts are derived. A description of the pseudo-random number generation method used in the wind gust model is included. The longitudinal autopilot, lateral autopilot, automatic throttle autopilot, engine model and automatic trim devices are considered as subsystems. The experience in converting the Airlabs FORTRAN aircraft control system simulation to a graphical simulation tool (Matlab/Simulink) is described.

  13. Calibration and Lag of a Friez Type Cup Anemometer

    Pinkerton, Robert M


    Tests on a Friez type cup anemometer have been made in the variable density wind tunnel of the Langley Memorial Aeronautical Laboratory to calibrate the instrument and to determine its suitability for velocity measurements of wind gusts. The instrument was calibrated against a Pitot-static tube placed directly above the anemometer at air densities corresponding to sea level, and to an altitude of approximately 6000 feet. Air-speed acceleration tests were made to determine the lag in the instrument reading. The calibration results indicate that there should be an altitude correction. It is concluded that the cup anemometer is too sluggish for velocity measurements of wind gusts.

  14. The Shock and Vibration Digest. Volume 14, Number 7


    Houbolt and Eichenbaum [103-105] have dealt with GLA in three-dimensional gusts. But a number of ’^’estigations have been carried out with respect to...of an Active Control System for Helicopter Vibration Reduction and Gust Response Alleviation," NASA CR-152377 (1980). 103. Eichenbaum , F.D...Thesis, Polytechnic Inst. of New York (1978). 5. Martin , C.R., "A Modal Control Approach for Active Control of Multi-Story Structures," Ph.D. Thesis

  15. Aeronca C-2N Deluxe Scout


    Aeronca C-2N Deluxe Scout: Known as the 'Flying Bathtub,' the portly Aeronca C-2N Deluxe Scout was used during Langley's research into the stability of light planes. Gust structure and intensity at low altitude was also investigated with the C-2. This particular C-2 still exists, as part of the collection of the Experimental Aircraft Association's Museum in Oshkosh, Wisconsin.

  16. Continuous-time state-space unsteady aerodynamic modelling for efficient aeroelastic load analysis

    Werter, N.P.M.; De Breuker, R.; Abdalla, M.M.


    Over the years, wings have become lighter and more flexible, making them more prone to aeroelastic effects. Thus, aeroelasticity in design becomes more important. In order to determine the response of an aircraft to, for example, a gust, an unsteady aerodynamic model is required to determine the dyn

  17. Experimental and numerical study of an autonomous flap

    Bernhammer, L.O.; Navalkar, S.T.; Sodja, J.; De Breuker, R.; Karpel, M.


    This paper presents the experimental and numerical study of an autonomous load alleviation concept using trailing edge flaps. The flaps are autonomous units, which for instance can be used for gust load alleviation. The unit is self-powered and self-actuated through trailing edge tabs which are moun

  18. A New Xeromorphic Species of Clusia (Clusiaceae) from Dry Valleys of Northern Peru

    Gustafsson, Mats


    Clusia magnoliiflora M. H. G. Gust. is described as new for the Clusiaceae. It grows in dry scrub in the river valleys of the Marañón and its tributaries in northern Peru, a kind of habitat that harbors very few Clusia species. The species is distinct on account of its extremely thick, obovate...

  19. 晋风晋韵卷地来——“华夏文明看山西”活动在京引起较大反响



    A gust of “Shanxi Wind” swept across the capital region from December 3 to 10. The week-long cultural events, designed to create and promote cultural brands with modem concepts and market-based approaches,showcased what Shanxi had achieved in recent years in reinventing it through culture.

  20. The effects of atmospheric turbulence on a quadrotor heavy lift airship

    Tischler, M. B.; Jex, H. R.


    The response of a quadrotor heavy lift airship to atmospheric turbulence is evaluated using a four-point input model. Results show interaction between gust inputs and the characteristic modes of the vehicle's response. Example loop closures demonstrate tradeoffs between response regulation and structural loads. Vehicle responses to a tuned discrete wave front compare favorably with the linear results and illustrate characteristic HLA motion.

  1. Comparative evaluation of the effectiveness of manual and automatic control deflection vector airship to take off stage

    В.П. Гусинін


    Full Text Available  In paper, results of the comparative effectiveness evaluation of the manual and automatic thrust vector control of airship in the class of «Zeppelin NT» at the takeoff are shown. The gust influences on the airship characteristics and the process of airship takeoff with one out of service engine are considered.

  2. Control research in windpower project 506259-1 control FOA, stage 1

    Ulen, E.


    A simplified rotor blade control for engines with variable speed; resonance compensation; and turbulence and gust models for controller development are discussed. Control of windpowered generators, and the simulation of a stochastic process with nonrational spectrum are considered. Computer control programs for a windpowered electric power plant are mentioned.

  3. Simulation Of Probabilistic Wind Loads On A Building

    Chamis, Christos C.; Shah, Ashwin R.


    Method of simulating probabilistic windloads on building developed. Numerical results of simulation used to assess reliability of building and risk associated with tendencies of large gusts or high steady winds to cause building to sway, buckle, and/or overturn. Using method to analyze proposed design in iterative design cycle, building designed for specified reliability.

  4. Dependence of Weibull distribution parameters on the CNR threshold i wind lidar data

    Gryning, Sven-Erik; Batchvarova, Ekaterina; Floors, Rogier Ralph;


    The increase in height and area swept by the blades of wind turbines that harvest energy from the air flow in the lower atmosphere have raised a need for better understanding of the structure of the profiles of the wind, its gusts and the monthly to annual long-term, statistical distribution...

  5. Photogrammetric Verification of Fiber Optic Shape Sensors on Flexible Aerospace Structures

    Moore, Jason P.; Rogge, Matthew D.; Jones, Thomas W.


    Multi-core fiber (MCF) optic shape sensing offers the possibility of providing in-flight shape measurements of highly flexible aerospace structures and control surfaces for such purposes as gust load alleviation, flutter suppression, general flight control and structural health monitoring. Photogrammetric measurements of surface mounted MCF shape sensing cable can be used to quantify the MCF installation path and verify measurement methods.

  6. Airfoil noise prediction from 2D3C PIV data

    De Santana, L.D.; Schram, C.; Desmet, W.


    The noise emitted by incoming turbulence interacting with an airfoil has many technological applications, and has accordingly received much attention in the literature. While numerous developments are focused on the determination of the airfoil response to a given incoming gust, the characterization

  7. Hoe verder na beeindiging van het fokverbod?

    Vesseur, P.


    In de gebieden waar het fokverbod geldt staan op dit moment alle zeugen gust. Er is weinig bekend over hoe het verder zal gaan met die zeugen. Toch is het goed er tijdig bij stil te staan. Wat is de verwachting op theoretische basis en hoe kan daarop worden ingespeeld?

  8. Experimental Aeroelastic Models Design and Wind Tunnel Testing for Correlation with New Theory


    Full Text Available Several examples of experimental model designs, wind tunnel tests and correlation with new theory are presented in this paper. The goal is not only to evaluate a new theory, new computational method or new aeroelastic phonomenon, but also to provide new insights into nonlinear aeroelastic phenomena, flutter, limit cycle oscillation (LCO and gust response.

  9. On Flood Alert

    LI LI


    @@ Aseries of heavy storms since early May led to severe flooding and landslides in south and southwest China,causing heaw casualties and economic losses.Severe convective weather such as downpours,gusts,hail and thunderstorms attacked these areas over a week from May 5.

  10. Determination of unsteady loads on a DU96W180 airfoil with actuated flap using particle image velocimetry

    Lindeboom, R.C.J.; Sterenborg, J.J.H.M.; Simao Ferreira, C.J.


    The unsteady flow conditions experienced by wind turbine blades lead to fatigue loads due to gusts, that increase the cost of energy. The decrease of the impact of these unsteady loads will most certainly lead to a decrease of the cost of energy. In order to alleviate unsteady loads the Smart Rotor

  11. Efectos del huracán Georges en la composición de especies y estructura de un bosque secundario en el interior de Puerto Rico

    A.E. Lugo; C.M. Domínguez Cristóbal; N. Méndez Irizarry


    From 1995 to 2003 we studied species composition and structure in a secondary subtropical wet forest in Utuado Puerto Rico. During September 21-22, 1998, hurricane Georges passed through the stand with maximum sustained winds of 184 km/h and gusts of 240 km/h. Species richness increased after the hurricane. While native species Miconia prasina reduced its Importance...

  12. Optimal Estimator Synthesis for Ship Dynamic Object Control

    BIYA MOTTO Frederic


    Optimal estimator synthesis algorithm for dynamic ship system control is considered. Estimator is constructed in the form of Kalman gain as steady-state Kalman filter. Estimator design is realised by MATLAB codes using account of wind gust noise with a set spectral intensity

  13. A Note on Coastally Trapped Waves Generated by the Wind at the Northern Bight of Panama


    tide gauge observations. 1. Introduction Although the winds in the guffs of Tehuantepec and Papagayo can reach gusts of 35 m/s (Romero- Centeno etal...perature. Geophys. Res. Letters 30, 1410, doi: 10.1029/2002GL0 16794. Romero- Centeno R., J. Zavala-Hidalgo, A. Gallegos and J. J. O’Brien, 2003

  14. Wind Retrieval using Marine Radars


    Interaction (HiRes) DRI the NATO Undersea Research Center ( NURC ) wants to develop and validate methodologies to retrieve wind field parameters from X-band...marine radar. The main parameters NURC will focus on are the mean surface wind vector as well as the wind gusts in vicinity of the measurement platform

  15. Soft tissue artifact in canine kinematic gait analysis

    Schwencke, M.; Smolders, L.A.; Bergknut, N.; Gustas, P.; Meij, B.P.; Hazewinkel, H.A.W.


    Vet Surg. 2012 Oct;41(7):829-37. doi: 10.1111/j.1532-950X.2012.01021.x. Soft tissue artifact in canine kinematic gait analysis. Schwencke M, Smolders LA, Bergknut N, Gustås P, Meij BP, Hazewinkel HA. Source Department of Clinical Sciences of Companion Animals,, Faculty of Veterinary Medicine, Utrech

  16. Research in Biological and Medical Sciences Including Biochemistry, Communicable Disease and Immunology, Internal Medicine, Physiology, Psychiatry, Surgery, and Veterinary Medicine. Volume 2


    Toxorhynchites mosquitoes; Den-i Hawaiian strain at the 15th passage in suckling mouse brain (SMB); Den-3 H-87 strain at the 25th passage in SMB; Den-4...troop rotations between Au- gust 1979 and December 1981 among units to be folio- ( wed . Total strength estimates based on August 1979 figures. Ft. Ft. Ft

  17. Generating Excitement: Build Your Own Generator to Study the Transfer of Energy

    Fletcher, Kurt; Rommel-Esham, Katie; Farthing, Dori; Sheldon, Amy


    The transfer of energy from one form to another can be difficult to understand. The electrical energy that turns on a lamp may come from the burning of coal, water falling at a hydroelectric plant, nuclear reactions, or gusts of wind caused by the uneven heating of the Earth. The authors have developed and tested an exciting hands-on activity to…

  18. Proceedings of the 1989 Structural Integrity Program Conference Held in San Antonio, Texas on 5-7 Dec 1989


    ASD/ENF 0800-0830 A Procedure for Separation of Gust and Maneuver Loads Dr F. Eichenbaum and J. W. Chapman - Lockheed Aeronautical Systems Company D...Systems Research Laboratory Ward Rummel Martin Marietta / Denver Lindy Shambaugh Pratt & Whitney / Florida Bob Stone San Antonio-A LC/MMFR Sharon Vukelich

  19. Modelling economic losses of historic and present-day high-impact winter windstorms in Switzerland

    Christoph Welker


    Full Text Available This study investigates the wind gusts and associated economic loss patterns of high-impact winter windstorms in Switzerland between 1871 and 2011. A novel approach for simulating windstorm-related gusts and losses at regional to local scales is applied to a sample of 84 windstorms. The approach involves the dynamical downscaling of the Twentieth Century Reanalysis (20CR ensemble mean to 3-km horizontal grid size using the Weather Research and Forecasting (WRF model. Economic losses are simulated at municipal level for present-day asset distribution based on the downscaled (parameterised wind gusts at high spatiotemporal resolution using the open-source impact model climada. A comparison with insurance loss data for two recent windstorms (“Lothar” in 1999, “Joachim” in 2011 indicates that the loss simulation allows to realistically simulate the spatial patterns of windstorm losses. The loss amplitude is strongly underestimated for ‘Lothar’, while it is in reasonable agreement for ‘Joachim’. Possible reasons are discussed. Uncertainties concerning the loss simulation arise from the wind gust estimation method applied; estimates can differ considerably among the different methods, in particular over high orography. Furthermore, the quality of the loss simulation is affected by the underlying simplified assumptions regarding the distribution of assets and their susceptibilities to damage. For the whole windstorm sample, composite averages of simulated wind gust speed and loss are computed. Both composites reveal high values for the densely populated Swiss Plateau and lower values for south-eastern Switzerland; metropolitan areas stand out in the loss composite. Eight of the top 10 events concerning the losses simulated for present-day asset distribution and summed over all Swiss municipalities occurred after 1950. It remains uncertain whether this is due to decadal-scale changes of winter windstorms in Switzerland or merely due to a

  20. Epidemiology of injuries due to tropical cyclones in Hong Kong: a retrospective observational study.

    Rotheray, K R; Aitken, P; Goggins, W B; Rainer, T H; Graham, C A


    Tropical cyclones are huge circulating masses of wind which form over tropical and sub-tropical waters. They affect an average of 78 million people each year. Hong Kong is a large urban centre with a population of just over 7 million which is frequently affected by tropical cyclones. We aimed to describe the numbers and types of injuries due to tropical cyclones in Hong Kong, as well as their relation to tropical cyclone characteristics. The records of all patients presenting to Hong Kong's public hospital emergency departments from 1st January 2004 to 31st December 2009 with tropical cyclone related injuries were reviewed and information regarding patient and injury characteristics was collected. Meteorological records for the relevant periods were examined and data on wind speed, rainfall and timing of landfall and warning signals was recorded and compared with the timing of tropical cyclone related injuries. A total of 460 tropical cyclone related injuries and one fatality across 15 emergency departments were identified during the study period. The mean age of those injured was 48 years and 48% were female. 25.4% of injuries were work related. The head (33.5%) and upper limb (32.5%) were the most commonly injured regions, with contusions (48.6%) and lacerations (30.2%) being the most common injury types. Falls (42.6%) were the most common mechanism of injury, followed by being hit by a falling or flying object (22.0%). In univariable analysis the relative risk of injury increased with mean hourly wind speed and hourly maximum gust. Multivariable analysis, however, showed that relative risk of injury increased with maximum gust but not average wind speed, with relative risk of injury rising sharply above maximum gusts of greater than 20 m/s. Moderate wind speed with high gust (rather than high average and high gust) appears to be the most risky situation for injuries. Relative risk of injury was not associated with rainfall. The majority of injuries (56

  1. A study of key features of random atmospheric disturbance models for the approach flight phase

    Heffley, R. K.


    An analysis and brief simulator experiment were performed to identify and classify important features of random turbulence for the landing approach flight phase. The analysis of various wind models was carried out within the context of the longitudinal closed-loop pilot/vehicle system. The analysis demonstrated the relative importance of atmospheric disturbance scale lengths, horizontal versus vertical gust components, decreasing altitude, and spectral forms of disturbances versus the pilot/vehicle system. Among certain competing wind models, the analysis predicted no significant difference in pilot performance. This was confirmed by a moving base simulator experiment which evaluated the two most extreme models. A number of conclusions were reached: attitude constrained equations do provide a simple but effective approach to describing the closed-loop pilot/vehicle. At low altitudes the horizontal gust component dominates pilot/vehicle performance.

  2. A conceptual framework for using Doppler radar acquired atmospheric data for flight simulation

    Campbell, W.


    A concept is presented which can permit turbulence simulation in the vicinity of microbursts. The method involves a large data base, but should be fast enough for use with flight simulators. The model permits any pilot to simulate any flight maneuver in any aircraft. The model simulates a wind field with three-component mean winds and three-component turbulent gusts, and gust variation over the body of an aircraft so that all aerodynamic loads and moments can be calculated. The time and space variation of mean winds and turbulent intensities associated with a particular atmospheric phenomenon such as a microburst is used in the model. In fact, Doppler radar data such as provided by JAWS is uniquely suited for use with the proposed model. The concept is completely general and is not restricted to microburst studies. Reentry and flight in terrestrial or planetary atmospheres could be realistically simulated if supporting data of sufficient resolution were available.

  3. Modeling of steady motion and vertical-plane dynamics of a tunnel hull

    Chaney, Christopher S.; Matveev, Konstantin I.


    High-speed marine vehicles can take advantage of aerodynamically supported platforms or air wings to increase maximum speed or transportation efficiency. However, this also results in increased complexity of boat dynamics, especially in the presence of waves and wind gusts. In this study, a mathematical model based on the fully unsteady aerodynamic extreme-ground-effect theory and the hydrodynamic added-mass strip theory is applied for simulating vertical-plane motions of a tunnel hull in a disturbed environment, as well as determining its steady states in calm conditions. Calculated responses of the boat to wind gusts and surface waves are demonstrated. The present model can be used as a supplementary method for preliminary estimations of performance of aerodynamically assisted marine craft.

  4. Methane storms as a driver of Titan's dune orientation

    Charnay, Benjamin; Rafkin, Scot; Narteau, Clément; Lebonnois, Sébastien; Rodriguez, Sébastien; Pont, Sylvain Courrech du; Lucas, Antoine


    Titan's equatorial regions are covered by eastward propagating linear dunes. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs), which are oriented westward at these latitudes, similar to trade winds on Earth. Different hypotheses have been proposed to address this apparent contradiction, involving Saturn's gravitational tides, large scale topography or wind statistics, but none of them can explain a global eastward dune propagation in the equatorial band. Here we analyse the impact of equinoctial tropical methane storms developing in the superrotating atmosphere (i.e. the eastward winds at high altitude) on Titan's dune orientation. Using mesoscale simulations of convective methane clouds with a GCM wind profile featuring superrotation, we show that Titan's storms should produce fast eastward gust fronts above the surface. Such gusts dominate the aeolian transport, allowing dunes to extend eastward. This analysis therefore suggests a coupling between superrotation, tro...

  5. The power fluctuations of a wind turbine

    Rosen, A; Sheinman, Y [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)


    At the beginning of the paper the power fluctuations in the case of a sinusoidal gust are investigated. A quasi-steady model is derived. Then this model is corrected to account for the dynamic characteristics of the turbine. The correction is introduced using a special correction function which is obtained after running a complete dynamic model of the wind turbine. It is shown that for each value of average wind speed there is, for practical purposes, a linear relation between the intensity of power fluctuations and the product of the intensity of turbulence and the above-mentioned correction function. The derivation for a sinusoidal gust is the basis for the analysis of the power fluctuations in the case of a `real` wind. The model for `real` wind is validated by comparing its results with field measurements

  6. Investigation of Convective Downburst Hazards to Marine Transportation

    Mason, D


    Convective downbursts are known to produce potentially hazardous weather conditions. Currently, severity indices are used to estimate the strength of a potential downburst, but this information does not readily translate to the variables affected by downburst events. The effects of downbursts are often associated with aviation because of rapid changes in wind direction and speed, but can also be observed in marine conditions. Three recently observed downburst events have been selected as case studies to evaluate the effects of the downbursts on the marine environment. The information gathered on these events includes wind speed, gusts and direction at the surface, air temperature and pressure, water level, and Wet Microburst Severity Index (WMSI) values. Correlation between the WMSI values, the maximum wind gust, and the change in water level is suggested.

  7. Wind regime and wind power in North Patagonia, Argentina

    Palese, C.; Laessig, J.L.; Cogliati, M.G.; Bastanski, M.A. [Universidad Nacional del Comahue, Buenos Aires (Argentina). Facultad de Ingenieria


    The present paper discusses wind and wind power characteristics in a region north of 40{sup o}S (North Patagonia, Argentina) as well as wind power projects sustainability. Extreme wind episodes influence most economic and social regional activities. Mean flow pattern was studied in three North Patagonia sites: Neuquen, Mari Menuco and Cutral-Co, by sampling analysis of wind direction and intensity during a year. Gusts were quantified and strong winds were studied. Available meteorological power was also estimated. It was observed that North Patagonia is a place of great wind power potential. However, the energy available, which is related to prevailing strong winds, is also associated to high gust occurrence which certainly restricts exploitation. (Author)

  8. Modeling of steady motion and vertical-plane dynamics of a tunnel hull

    Chaney Christopher S.


    Full Text Available High-speed marine vehicles can take advantage of aerodynamically supported platforms or air wings to increase maximum speed or transportation efficiency. However, this also results in increased complexity of boat dynamics, especially in the presence of waves and wind gusts. In this study, a mathematical model based on the fully unsteady aerodynamic extreme-ground-effect theory and the hydrodynamic added-mass strip theory is applied for simulating vertical-plane motions of a tunnel hull in a disturbed environment, as well as determining its steady states in calm conditions. Calculated responses of the boat to wind gusts and surface waves are demonstrated. The present model can be used as a supplementary method for preliminary estimations of performance of aerodynamically assisted marine craft.

  9. Extreme wind estimate for Hornsea wind farm

    Larsén, Xiaoli Guo

    The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

  10. Aerodynamic performance prediction of Darrieus-type wind turbines

    Ion NILĂ


    Full Text Available The prediction of Darrieus wind turbine aerodynamic performances provides the necessarydesign and operational data base related to the wind potential. In this sense it provides the type ofturbine suitable to the area where it is to be installed. Two calculation methods are analyzed for arotor with straight blades. The first one is a global method that allows an assessment of the turbinenominal power by a brief calculation. This method leads to an overestimation of performances. Thesecond is the calculation method of the gust factor and momentum which deals with the pale as beingcomposed of different elements that don’t influence each other. This method, developed based on thetheory of the turbine blades, leads to values close to the statistical data obtained experimentally. Thevalues obtained by the calculation method of gust factor - momentum led to the concept of a Darrieusturbine, which will be tested for different wind values in the INCAS subsonic wind tunnel.

  11. Effects of automobile steering characteristics on driver vehicle system dynamics in regulation tasks

    Mcruer, D. T.; Klein, R.


    A regulation task which subjected the automobile to a random gust disturbance which is countered by driver control action is used to study the effects of various automobile steering characteristics on the driver/vehicle system. The experiments used a variable stability automobile specially configured to permit insertion of the simulated gust disturbance and the measurement of the driver/vehicle system characteristics. Driver/vehicle system dynamics were measured and interpreted as an effective open loop system describing function. Objective measures of system bandwidth, stability, and time delays were deduced and compared. These objective measures were supplemented by driver ratings. A tentative optimum range of vehicle dynamics for the directional regulation task was established.

  12. Sampled-Data Backstepping Control of a Quadrotor Unmanned Aerial Vehicle

    Abdul Jabbar


    Full Text Available Sampled-data backstepping control of a quadrotor UAV is presented in this paper. The discrete time controllers have been designed on the basis of a continuous time system model and an approximate discrete time equivalent system model (Euler Approximate model obtained using the Euler method. The performance of the controllers obtained using the two sampled-data approaches has been compared in the presence of wing gusts and modeling uncertainties. Simulations have revealed that the backstepping controller designed on the basis of an approximate discrete time model has better performance in the presence of wind gusts and modeling uncertainties. In addition, the closed loop system has a larger region of attraction.

  13. Benchmark Solutions for Computational Aeroacoustics (CAA) Code Validation

    Scott, James R.


    NASA has conducted a series of Computational Aeroacoustics (CAA) Workshops on Benchmark Problems to develop a set of realistic CAA problems that can be used for code validation. In the Third (1999) and Fourth (2003) Workshops, the single airfoil gust response problem, with real geometry effects, was included as one of the benchmark problems. Respondents were asked to calculate the airfoil RMS pressure and far-field acoustic intensity for different airfoil geometries and a wide range of gust frequencies. This paper presents the validated that have been obtained to the benchmark problem, and in addition, compares them with classical flat plate results. It is seen that airfoil geometry has a strong effect on the airfoil unsteady pressure, and a significant effect on the far-field acoustic intensity. Those parts of the benchmark problem that have not yet been adequately solved are identified and presented as a challenge to the CAA research community.

  14. Endurance and stability of some surface meteorological sensors under land- and ship-based operating environments

    Mehra, P.; Desai, R.G.P.; Joseph, A.; VijayKumar, K.; Dabholkar, N.; Prabhudesai, S.; Nagvekar, S.; Agarvadekar, Y.

    at NIO is presented in Fig. 2. TABLE 1. PARTICULARS OF SENSORS USED IN THE AWS SYSTEM Surface meteorological parameter Sensor type Specifications Wind speed & direction Propeller & Vane (Model: 05103 from R.M. Young, U.S.A) Speed range Gust... and Mrs. Vimala Damodaran. REFERENCES [1]. R. G. Prabhudesai, P. Mehra, E. Desa, S. Nagvekar, and V. Kumar, Weather Station for Scientific Data Collection, Second Indian National Conference on Harbour and Ocean Engineering (INCHOE-97), 1997...

  15. Integrated Airframe Design Technology (Les Technologies pour la Conception Integree des Cellules)


    tunnel results can be fened structure ( a variation of blade stiffened). The optimiza- applied to the structural model via the mapping process. tion...effect on loads and structures are - oscillating " acceptable Load Level and "runaway". (see Fig. 10) These have to be studied in their loads To a...Aileron- Oscillating Allowed Surface Deflection Acceptable by Static Loads Envelope Gust induced nicrer-rital load factor LODAILERON DEMAND ;;AILERON

  16. Random harmonic analysis program, L221 (TEV156). Volume 1: Engineering and usage

    Miller, R. D.; Graham, M. L.


    A digital computer program capable of calculating steady state solutions for linear second order differential equations due to sinusoidal forcing functions is described. The field of application of the program, the analysis of airplane response and loads due to continuous random air turbulence, is discussed. Optional capabilities including frequency dependent input matrices, feedback damping, gradual gust penetration, multiple excitation forcing functions, and a static elastic solution are described. Program usage and a description of the analysis used are presented.

  17. Statistical modeling of space shuttle environmental data

    Tubbs, J. D.; Brewer, D. W.


    Statistical models which use a class of bivariate gamma distribution are examined. Topics discussed include: (1) the ratio of positively correlated gamma varieties; (2) a method to determine if unequal shape parameters are necessary in bivariate gamma distribution; (3) differential equations for modal location of a family of bivariate gamma distribution; and (4) analysis of some wind gust data using the analytical results developed for modeling application.

  18. Characterization of vortical structures and loads based on time-resolved PIV for asymmetric hovering flapping flight

    Jardin, Thierry; David, Laurent; Farcy, Alain


    International audience; Flight agility, resistance to gusts, capability to hover coupled with a low noise generation might have been some of the reasons why insects are among the oldest species observed in nature. Biologists and aerodynamicists focused on analyzing such flight performances for diverse purposes: understanding the essence of flapping wings aerodynamics and applying this wing concept to the development of micro-air vehicles (MAVs). In order to put into evidence the fundamentally...

  19. Airport surveillance using a solid state coherent lidar

    Huffaker, R. Milton; Hannon, Stephen M.


    The utility of solid state coherent LIDAR was assessed in the following application areas: (1) wake vortices; (2) dry and wet microburst windshear; (3) gusts; (4) vertical and general wind profiling; and (5) cloud ceiling. The system performance model described was based on a concept definition, system sizing, measurement planning, and algorithm and graphics display development. Data were collected at the Kennedy Space Center and the National Weather Service site adjacent to Denver's Stapleton Airport.

  20. A Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics. Part 1. Analysis Development


    The perturbation velozity components are due to the blade degrees of freedom, the shaft motion, and the aerodynamic gust velocity: -tA 4- + V(. o ) -A...gimballed, and teetering rotors with an arbitrary number of blades. The rotor degrees of freedom included are blade flap/lag bending, rigid pitch and elastic...tunnel is also covered. The aircraft degrees of freedom included are the six rigid body motions, elastic airframe motions, and the rotor/engine speed

  1. Typhoon Havens Handbook for the Western Pacific and Indian Oceans. Change 3


    Command Facility, Yokosuka issues local wind warnings. The established procedures when hazardous weather is expected are given in SOPA (ADMIN...YOKOSUKA INSTRUCTION 5000.1. As directed by SOPA , wind from any direction with expected sustained speeds of 48 kt or gusts in excess of 55 kt is sufficient...sorties must be commenced early because of the restricted waters near Sasebo. Ordinarily SOPA will not order a general sortie from the harbor. Harbor

  2. The Interface of Nanoscale Inclusion Chemistry


    Omare Carrer Cluster Gusts ........................................... 000 I. Sodalite Based Hosts ................................................ 000...Ishihara, 1. Takahashi, and T. Goto, Phys. Rev. B: Condens. Matter, 42. 11099 (1990). 200. J. Calabrese , N. L. Jones, R. L. Harlow, N. Herron, D. L...Tam, and Y. Wang, J. Am. Chem. Soc.. 109, 1886 (1987). 227. W. Tam, D. F. Eaton, 1. C. Calabrese , I. D. Williams, Y. Wang, and A. G. Anderson. Chem

  3. Cartel Car Bombings in Mexico


    April and Au- gust 2006 were targeted against a “. . . busy restaurant in the Pacific coast town of Petatlán, Mexico . . .” and against “. . . the...understand military concepts, much less perceptions of an opposition force (OPFOR) that engages in proactive offensive operations, drawing upon throwing it into the bar. The grenade was South Korean made and had the same markings as grenades used against the U.S consulate in Monterey

  4. Into Turbulent Air: Hummingbird Aerodynamic Control in Unsteady Circumstances


    of this study, we also completed analysis of hummingbird kinematic responses to transient vertical gusts and to flight in sheared flows , and have...Distribution A - Approved for Public Release 13. SUPPLEMENTARY NOTES 14. ABSTRACT We have completed and published experimental results and analysis pertaining...enough to interact with both wings elicited the greatest changes in roll, pitch, and yaw fluctuations, and also induced major increases in metabolic

  5. Coevolution of Form and Function in the Design of Micro Air Vehicles


    controllers , which allow the user to control the aircraft by specifying only the turn rate values; the PID controllers adjust speed and altitude of...mentioned, the altitude and the speed of the plane are adjusted as necessary by underlying PID controllers . 5.3 Implementation of Evolution Due to...wind gusts, this initial study does not take advantage of these capabilities. The low-level control for the MAV is implemented using a number of PID

  6. Bitter taste receptors and α-gustducin regulate the secretion of ghrelin with functional effects on food intake and gastric emptying.

    Janssen, Sara; Laermans, Jorien; Verhulst, Pieter-Jan; Thijs, Theo; Tack, Jan; Depoortere, Inge


    Ghrelin is a hunger hormone with gastroprokinetic properties but the factors controlling ghrelin secretion from the stomach are unknown. Bitter taste receptors (T2R) and the gustatory G proteins, α-gustducin (gust) and α-transducin, are expressed in the gut and are involved in the chemosensation of nutrients. This study aimed to investigate whether T2R-agonists affect (i) ghrelin release via α-gustducin and (ii) food intake and gastric emptying via the release of ghrelin. The mouse stomach contains two ghrelin cell populations: cells containing octanoyl and desoctanoyl ghrelin, which were colocalized with α-gustducin and α-transducin, and cells staining for desoctanoyl ghrelin. Gavage of T2R-agonists increased plasma octanoyl ghrelin levels in WT mice but the effect was partially blunted in gust(-/-) mice. Intragastric administration of T2R-agonists increased food intake during the first 30 min in WT but not in gust(-/-) and ghrelin receptor knockout mice. This increase was accompanied by an increase in the mRNA expression of agouti-related peptide in the hypothalamus of WT but not of gust(-/-) mice. The temporary increase in food intake was followed by a prolonged decrease (next 4 h), which correlated with an inhibition of gastric emptying. The delay in emptying, which was partially counteracted by ghrelin, was not mediated by cholecystokinin and GLP-1 but involved a direct inhibitory effect of T2R-agonists on gastric contractility. This study is unique in providing functional evidence that activation of bitter taste receptors stimulates ghrelin secretion. Modulation of endogenous ghrelin levels by tastants may provide novel therapeutic applications for the treatment of weight -and gastrointestinal motility disorders.

  7. Roller-coaster Life in China

    Anthony; L.Iacono


    Our arrival in Changzhou in late Au- gust was the start of a roller-coaster ride.The stability and peace of a few days always gave away to the stress and frustration of the days after, only to return once again to calm in the following days.Adjusting to the local conditions is proved dif- ficult,and even now,after living in China for a year, negativity still arises in response to certain behav-

  8. Tropical Cyclones Affecting Guam (1671-1980).


    8217 .. , - - - " - "- - --..44,. . .-.-.-.-..- , .. ,:. .; .. . . .. - : L , I . . ucu~ IPtv CLASSIFICATION OF THIS PAGQIK(., Dd~ ate trot BLANK.PAGE z SECuRItY...powerlines destroyed, water system inoperative, new hospital roof, supply and public works center badly damaged. Total damage to public and (20 kt) tropical storm passed over Agana with brief gusts of 45-50 kt experienced over northern portion of island. Rainfall from system was

  9. Turbine-Mounted Lidar:The pulsed lidar as a reliable alternative.

    Braña, Isaac


    Expectations for turbine-mounted lidar are increasing. The installation of lidars in wind turbine nacelles for measuring incoming winds, preventing wind gusts and increasing energy productions is after recently studies, technically and economically feasible. Among available lidar types, the most studied were continuous wave lidars because they were the most reliable apparatus when this initiative began. However, after studying technical considerations and checking commercial lidars, it was fo...

  10. Warm-season severe wind events in Germany

    Gatzen, Christoph


    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.

  11. Solid State Research, 1980:4


    W. Geis D. A. Antoniadie D. J. Silversmith R. W. Mountain H. I. Smith 12th Conference on Solid State Devices, Tokyo. Japan, 26 Au- gust 1980...Lateral Epitaxial Over* growth of Silicon on St02 D.D. Jtathman D. J. Silversmith Electrochemical Society Mtg«. Hollywood. Florida. 6-10 Octo...qualitatively in agreement. DJ# silversmith B. E. Burke R. W. Mountain C. CHARGE-COUPLED DEVICES: PROGRAMMABLE TRANSVERSAL FILTER As previously

  12. Wind energy conversion. Progress report, July 15, 1975--February 15, 1976

    Miller, R.H.; Martinez-Sanchez, M.; Dugundji, J.; Larrabee, E.; Humes, T.; Chopra, I.; Smith, F.


    Information is presented concerning control strategies for maximum power; loading in the presence of wind shear and gusts; aeroelastic stability margins; performance comparison between constant rpm and constant velocity ratio operation; synchronous alternators for wind energy conversion; experimental vibration behavior of windmill; experimental wind turbine model description; development of solution for finite number of blades; aerodynamic design and performance of windmills; linear aeroelastic analysis of blade; and nonlinear analysis of a feathering-flapping-lagging rigid rotor blade without aerodynamics.

  13. Design Requirements for Weaponizing Man-Portable UAS in Support of Counter-Sniper Operations


    I Construction I System Retirement and Material Recycling /Disposal I • Construction, test , and verif ication of system I • System retirement and...27). The camera was rather easily integrated into the Raven avionics and GCS video and was bore sighted so that a cross- hair on the operator’s HUD...can be seen departing the barrel. The small cross- hair in the center of the screen is where the paintball actually struck the HMWWV. Wind gusts

  14. The new textiles GB to be implemented in August


    After a transitional period of one year, the new version of the National Textile Product General Safety Tech- nical Code will be implemented from August 1. Compared to the old GB, the new GB expanded the age range covered by the infant textile products, 2~3 years old children’s clothing pro- duced in accordance with the original standard will be off the shelf after Au- gust. According to reports, the mandatory

  15. Life-Cycle Cost Analysis for Small Unmanned Aircraft Systems Deployed Aboard Coast Guard Cutters


    of an sUAS Swarm ............................................................ 13 Figure 7.   Dr. Timothy Chung Testing sUAS Swarm Technology at the...Air Force Base (AFB), in 2011, Derek J. Snyder , in collaboration with United States Special Operations Command (USSOCOM), conducted a proof of...feet of the target. (Wind gusts were a significant factor in the paintballs’ accuracy.) Snyder found that a tactical sUAS could “at a minimum

  16. Innovative Wing Structures for Improved Aerodynamic and Aeroelastic Performance


    considered for many years in the design process as a certification requirement so as to avoid undesirable flutter/divergence behaviour or catastrophic...failure during a gust encounter[2]. Hence the control of aeroelastic behaviour was limited to consideration after the initial wing design, often resulting...have shown large positive impact on the aeroelastic performance in research work. However, since the initial work in the early 1980s, the idea of

  17. Control law design to meet constraints using SYNPAC-synthesis package for active controls

    Adams, W. M., Jr.; Tiffany, S. H.


    Major features of SYNPAC (Synthesis Package for Active Controls) are described. SYNPAC employs constrained optimization techniques which allow explicit inclusion of design criteria (constraints) in the control law design process. Interrelationships are indicated between this constrained optimization approach, classical and linear quadratic Gaussian design techniques. Results are presented that were obtained by applying SYNPAC to the design of a combined stability augmentation/gust load alleviation control law for the DAST ARW-2.

  18. Wind simulation for extreme and fatigue loads

    Nielsen, M.; Larsen, G.C.; Mann, J.; Ott, S.; Hansen, K.S.; Pedersen, B.J.


    Measurements of atmospheric turbulence have been studied and found to deviate from a Gaussian process, in particular regarding the velocity increments over small time steps, where the tails of the pdf are exponential rather than Gaussian. Principles for extreme event counting and the occurrence of cascading events are presented. Empirical extreme statistics agree with Rices exceedence theory, when it is assumed that the velocity and its time derivative are independent. Prediction based on the assumption that the velocity is a Gaussian process underpredicts the rate of occurrence of extreme events by many orders of magnitude, mainly because the measured pdf is non-Gaussian. Methods for simulation of turbulent signals have been developed and their computational efficiency are considered. The methods are applicable for multiple processes with individual spectra and probability distributions. Non-Gaussian processes are simulated by the correlation-distortion method. Non-stationary processes are obtained by Bezier interpolation between a set of stationary simulations with identical random seeds. Simulation of systems with some signals available is enabled by conditional statistics. A versatile method for simulation of extreme events has been developed. This will generate gusts, velocity jumps, extreme velocity shears, and sudden changes of wind direction. Gusts may be prescribed with a specified ensemble average shape, and it is possible to detect the critical gust shape for a given construction. The problem is formulated as the variational problem of finding the most probable adjustment of a standard simulation of a stationary Gaussian process subject to relevant event conditions, which are formulated as linear combination of points in the realization. The method is generalized for multiple correlated series, multiple simultaneous conditions, and 3D fields of all velocity components. Generalization are presented for a single non-Gaussian process subject to relatively

  19. United States Air Force Academy (USAFA) Vertical Axis Wind Turbine.


    Laboratories (Reference 9) resulted in the conclusion that a two-bucket Savonius -type arrangement with gaps at the rotating shaft was most efficient...and at some orientations of the Savonius buckets, the actual static torque produced may be as much as 35 percent less than above. Thus, a wind gust to...from the Savonius starting turbine alone. -63- SECTION VII CONCLUSIONS AND RECOMIENDATIONS 1. CONCLUSIONS One objective of the USAF Academy Wind

  20. Inlet Guide Vane Wakes Including Rotor Effects

    Johnston, R. T.; Fleeter, S.


    Fundamental experiments are described directed at the investigation of forcing functions generated by an inlet guide vane (IGV) row, including interactions with the downstream rotor, for application to turbomachine forced response design systems. The experiments are performed in a high-speed research fan facility comprised of an IGV row upstream of a rotor. IGV-rotor axial spacing is variable, with the IGV row able to be indexed circumferentially, thereby allowing measurements to be made across several IGV wakes. With an IGV relative Mach number of 0.29, measurements include the IGV wake pressure and velocity fields for three IGV-rotor axial spacings. The decay characteristics of the IGV wakes are compared to the Majjigi and Gliebe empirical correlations. After Fourier decomposition, a vortical-potential gust splitting analysis is implemented to determine the vortical and potential harmonic wake gust forcing functions both upstream and downstream of the rotor. Higher harmonics of the vortical gust component of the IGV wakes are found to decay at a uniform rate due to viscous diffusion.

  1. Determination of wind speed and associated loads over the sports facility collapsed during the severe windstorm of 24 January 2009 in Sant Boi de Llobregat (Barcelona

    J. Mazón


    Full Text Available The severe windstorm of 24 January 2009, caused by an explosive cyclogenesis, affected coastal and precoastal areas of the northeast of the Iberian Peninsula, where damages were numerous and significant, both in urban areas and in forests. One of the most important effects was the collapse of a sports facility in Sant Boi de Llobregat (10 km southwest of Barcelona, killing four children. The objective of this study is to estimate the wind speed over the sports facility and calculate the suction of the wind on the roof of the building, and the consequent collapse of the walls. To get a first approximation, a simulation of the episode around the time of maximum wind gust was inspected using the mesoscale model MM5. In the second part, the damage around the collapsed facility was analyzed, with which we note the fact that a truck was dragged and knocked over by the wind. This analysis allows for the conclusion that, in conjunction with the maximum wind gust, there was a sudden and very local shift in the wind, which caused the gust to hit the building head on. Based on this observation, the wind speed on surface and at 7 m (roof of the building was estimated, and the suction of the wind was calculated.

  2. On the estimation of wind comfort in a building environment by micro-scale simulation

    Günter Gross


    Full Text Available A three-dimensional micro-scale model is used to study some aspects of wind comfort in a built-up area. The equations for calculating the mean wind have been extended by a Markov approach for short-term wind fluctuations. The model components have been successfully verified against wind tunnel measurements and observations of a field experiment. The simulated time series are used to estimate wind comfort measures. It turns out that the frequency of exceedance of prescribed thresholds depends strongly on the specification of the gust duration time. It was also possible to calculate the spatial distribution of a gust factor g$g$ depending on local wind characteristics. The simulated range is much broader than a value of g=3–3.5$g=3\\text{--}3.5$ commonly used for wind comfort assessments. Again, the order of magnitude and the bandwidth of g$g$ depends strongly on the definition of a gust.

  3. Characterization of Surface Level Wind in the Centro de Lançamento de Alcântara for Use in Rocket Structure Loading and Dipersion Studies

    Edson R. Marciotto


    Full Text Available We present wind data collected for ten days during the dry season in 2008 during the Murici II Campaign, which was carried out in the area of the Centro de Lançamento de Alcântara (CLA. The main goals are to better understand processes governing the wind regime in the CLA and the development of tools for analyzing the impact of wind on rocket structure and on the dispersion of pollutants released during the launch. A set of 11 aerovanes (ten at 10-m height and one at 1.5-m height plus a sonic anemometer at 1.5-m height were deployed to measure wind speed and direction, which were stored as ten-minute data. Turbulence intensity, gust factor, and gust amplitude were computed from the available dataset. Statistical analysis shows that the wind direction is predominant from East-Northeast (ENE, with the mean vector wind direction of 60o, in agreement with the trade wind regime. The diurnal cycle of all statistical properties of the wind are strongly marked. Wind speed, turbulence intensity, and gusts are peaked at about 1000 LST. The presence of a non-diurnal cycle of four days has been noticed and might be associated with synoptic systems acting on the region. A simple heuristic formula was proposed to compute Lagrangian time-scale from Eulerian time-scale, and from which we compute the Lagragian standard deviation, a final product to be used as input in diffusion models.

  4. Relevant Criteria for Testing the Quality of Models for Turbulent Wind Speed Fluctuations

    Frandsen, Sten Tronæs; Ejsing Jørgensen, Hans; Sørensen, John Dalsgaard


    -size wind turbines when seeking wind characteristics that correspond to one blade and the entire rotor, respectively. For heights exceeding 50-60  m, the gust factor increases with wind speed. For heights larger than 60-80  m, present assumptions on the value of the gust factor are significantly......Seeking relevant criteria for testing the quality of turbulence models, the scale of turbulence and the gust factor have been estimated from data and compared with predictions from first-order models of these two quantities. It is found that the mean of the measured length scales is approximately...... 10% smaller than the IEC model for wind turbine hub height levels. The mean is only marginally dependent on trends in time series. It is also found that the coefficient of variation of the measured length scales is about 50%. 3  s and 10  s preaveraging of wind speed data are relevant for megawatt...

  5. The XWS open access catalogue of extreme European windstorms from 1979–2012

    J. F. Roberts


    Full Text Available The XWS (eXtreme WindStorms catalogue consists of storm tracks and model-generated maximum three-second wind-gust footprints for 50 of the most extreme winter windstorms to hit Europe over 1979–2012. The catalogue is intended to be a valuable resource for both academia and industries such as (reinsurance, for example allowing users to characterise extreme European storms, and validate climate and catastrophe models. Several storm severity indices were investigated to find which could best represent a list of known high loss (severe storms. The best performing index was Sft, which is a combination of storm area calculated from the storm footprint and maximum 925 hPa wind speed from the storm track. All the listed severe storms are included in the catalogue, and the remaining ones were selected using Sft. A comparison of the model footprint to station observations revealed that storms were generally well represented, although for some storms the highest gusts were underestimated due to the model not simulating strong enough pressure gradients. A new recalibration method was developed to estimate the true distribution of gusts at each grid point and correct for this underestimation. The recalibration model allows for storm-to-storm variation which is essential given that different storms have different degrees of model bias. The catalogue is available at http:///

  6. Symmetric airfoil geometry effects on leading edge noise.

    Gill, James; Zhang, X; Joseph, P


    Computational aeroacoustic methods are applied to the modeling of noise due to interactions between gusts and the leading edge of real symmetric airfoils. Single frequency harmonic gusts are interacted with various airfoil geometries at zero angle of attack. The effects of airfoil thickness and leading edge radius on noise are investigated systematically and independently for the first time, at higher frequencies than previously used in computational methods. Increases in both leading edge radius and thickness are found to reduce the predicted noise. This noise reduction effect becomes greater with increasing frequency and Mach number. The dominant noise reduction mechanism for airfoils with real geometry is found to be related to the leading edge stagnation region. It is shown that accurate leading edge noise predictions can be made when assuming an inviscid meanflow, but that it is not valid to assume a uniform meanflow. Analytic flat plate predictions are found to over-predict the noise due to a NACA 0002 airfoil by up to 3 dB at high frequencies. The accuracy of analytic flat plate solutions can be expected to decrease with increasing airfoil thickness, leading edge radius, gust frequency, and Mach number.

  7. European extra-tropical storm damage risk from a multi-model ensemble of dynamically-downscaled global climate models

    M. R. Haylock


    Full Text Available Uncertainty in the return levels of insured loss from European wind storms was quantified using storms derived from twenty-two 25 km regional climate model runs driven by either the ERA40 reanalyses or one of four coupled atmosphere-ocean global climate models. Storms were identified using a model-dependent storm severity index based on daily maximum 10 m wind speed. The wind speed from each model was calibrated to a set of 7 km historical storm wind fields using the 70 storms with the highest severity index in the period 1961–2000, employing a two stage calibration methodology. First, the 25 km daily maximum wind speed was downscaled to the 7 km historical model grid using the 7 km surface roughness length and orography, also adopting an empirical gust parameterisation. Secondly, downscaled wind gusts were statistically scaled to the historical storms to match the geographically-dependent cumulative distribution function of wind gust speed.

    The calibrated wind fields were run through an operational catastrophe reinsurance risk model to determine the return level of loss to a European population density-derived property portfolio. The risk model produced a 50-yr return level of loss of between 0.025% and 0.056% of the total insured value of the portfolio.

  8. The Gustatory Signaling Pathway and Bitter Taste Receptors Affect the Development of Obesity and Adipocyte Metabolism in Mice.

    Bert Avau

    Full Text Available Intestinal chemosensory signaling pathways involving the gustatory G-protein, gustducin, and bitter taste receptors (TAS2R have been implicated in gut hormone release. Alterations in gut hormone profiles may contribute to the success of bariatric surgery. This study investigated the involvement of the gustatory signaling pathway in the development of diet-induced obesity and the therapeutic potential of targeting TAS2Rs to induce body weight loss. α-gustducin-deficient (α-gust-/- mice became less obese than wild type (WT mice when fed a high-fat diet (HFD. White adipose tissue (WAT mass was lower in α-gust-/- mice due to increased heat production as a result of increases in brown adipose tissue (BAT thermogenic activity, involving increased protein expression of uncoupling protein 1. Intra-gastric treatment of obese WT and α-gust-/- mice with the bitter agonists denatonium benzoate (DB or quinine (Q during 4 weeks resulted in an α-gustducin-dependent decrease in body weight gain associated with a decrease in food intake (DB, but not involving major changes in gut peptide release. Both WAT and 3T3-F442A pre-adipocytes express TAS2Rs. Treatment of pre-adipocytes with DB or Q decreased differentiation into mature adipocytes. In conclusion, interfering with the gustatory signaling pathway protects against the development of HFD-induced obesity presumably through promoting BAT activity. Intra-gastric bitter treatment inhibits weight gain, possibly by directly affecting adipocyte metabolism.

  9. The Santa AnaWinds of Southern California in the context of Fire Weather

    Cao, Yang

    The Santa Ana winds represent a high-impact weather event owing to the intimate relationship between the extremely dry, fast winds and the wildfire threat. The winds can be locally gusty, particularly in the complex terrain of San Diego county, where the airflow has characteristics of downslope windstorms. These winds can cause and/or rapidly spread wildfires, the threat of which is particularly acute during the autumn season before the onset of winter rains. It remains a day-to-day challenge to accurately predict wind gust speed, especially in the mountainous regions. Our study employs large physics ensembles composed of high-resolution simulations of severe downslope windstorms that involve an exhaustive examination of available model physical parameterizations. Model results are calibrated and validated against the San Diego Gas and Electric (SDG&E) mesonet observations, a dense, homogenous, and well-positioned network with uniform high quality. Results demonstrate model horizontal resolution, model physics, random perturbations and landuse database can have a material effect on the strength, location and timing of Santa Ana winds in real-data simulations. A large model physics ensemble reveals the land surface model to be most crucial in skillful wind predictions, which are particularly sensitive to the surface roughness length. A surprisingly simple gust parameterization is proposed for the San Diego network, based on the discovery that this homogeneous mesonet has a nearly invariant network-averaged gust factor. The gust forecast technique is of special interest in the context of routine weather combined with atmospheric humidity and fuel moisture information. A real-time wildfire threat warning system, the Santa Ana Wildfire Threat Index (SAWTI), has been developed to effectively communicate the upcoming Santa Ana wind strength with respect to the anticipated fire danger to first responders and the public. In addition to the wind and gust forecast techniques

  10. Study on the Engineering Calculation Method for Vertical Tail Buffet Response%垂尾抖振响应工程计算方法研究

    吴谦; 李斌; 杨飞


    The differences between gust response computation and buffet response computation are analyzed,and a calculation method for buffet response by modifying gust response computational procedure of the NASTRAN software is proposed. This method uses the power spectral density of the fluctuation pressure obtained from the wind-tunnel test of a rigid model as the external excitation. and the aerodynamic forces due to vertical fin motion can be calculated using a subsonic doublet-lattice lifting surface method which has been involved in the gust response calculating module of NASTRAN solver. Base on the NASTRAN software. we re-developed a buffet response calculation software. which used the DMAP language to modify the computational procedure of NASTRAN gust response, and to shield the gust load calculation. and to realize the directly input of buffet force. Then,a numerical example was performed to validate the feasibility of the proposed method.%分析了突风响应计算与抖振响应计算在计算原理上的差异,并提出一种修改NASTRAN突风响应计算流程作为进行抖振响应计算的方法.该方法可以采用刚性模型风洞试验测得的参考点脉动压力数据作为输入激励,翼面运动产生非定常气动力贡献则可以突风响应计算中偶极网格法计算模块计算.在NASTRAN软件的基础上,应用DMAP语言进行SOL 146求解器求解流程的修改,实现了抖振响应计算程序的二次开发,实现了突风载荷计算的屏蔽和抖振激励载荷的表征和输入处理.算例验算表明了算法的可行性.

  11. Wind Tunnel Testing of Microtabs and Microjets for Active Load Control of Wind Turbine Blades

    Cooperman, Aubryn Murray

    Increases in wind turbine size have made controlling loads on the blades an important consideration for future turbine designs. One approach that could reduce extreme loads and minimize load variation is to incorporate active control devices into the blades that are able to change the aerodynamic forces acting on the turbine. A wind tunnel model has been constructed to allow testing of different active aerodynamic load control devices. Two such devices have been tested in the UC Davis Aeronautical Wind Tunnel: microtabs and microjets. Microtabs are small surfaces oriented perpendicular to an airfoil surface that can be deployed and retracted to alter the lift coefficient of the airfoil. Microjets produce similar effects using air blown perpendicular to the airfoil surface. Results are presented here for both static and dynamic performance of the two devices. Microtabs, located at 95% chord on the lower surface and 90% chord on the upper surface, with a height of 1% chord, produce a change in the lift coefficient of 0.18, increasing lift when deployed on the lower surface and decreasing lift when deployed on the upper surface. Microjets with a momentum coefficient of 0.006 at the same locations produce a change in the lift coefficient of 0.19. The activation time for both devices is less than 0.3 s, which is rapid compared to typical gust rise times. The potential of active device to mitigate changes in loads was tested using simulated gusts. The gusts were produced in the wind tunnel by accelerating the test section air speed at rates of up to 7 ft/s 2. Open-loop control of microtabs was tested in two modes: simultaneous and sequential tab deployment. Activating all tabs along the model span simultaneously was found to produce a change in the loads that occurred more rapidly than a gust. Sequential tab deployment more closely matched the rates of change due to gusts and tab deployment. A closed-loop control system was developed for the microtabs using a simple

  12. Coupling of Airway Smooth Muscle Bitter Taste Receptors to Intracellular Signaling and Relaxation Is via Gαi1,2,3.

    Kim, Donghwa; Woo, Jung A; Geffken, Ezekiel; An, Steven S; Liggett, Stephen B


    Bitter taste receptors (TAS2Rs) are expressed on human airway smooth muscle (HASM) and evoke marked relaxation. Agonist interaction with TAS2Rs activates phospholipase C and increases compartmentalized intracellular Ca(2+) ([Ca(2+)]i) via inositol 1,4,5 triphosphate. In taste cells, the G protein gustducin couples TAS2R to phospholipase C; however, we find very low levels of Gαgust mRNA or protein in HASM. We hypothesized that another G protein in HASM transmits TAS2R function. TAS2R signaling to [Ca(2+)]i, extracellular signal-regulated kinase (ERK) 1/2, and physiologic relaxation was sensitive to pertussis toxin, confirming a role for a member of the Gi family. α subunit expression in HASM was Gαi2 > Gαi1 = Gαi3 > Gαtrans1 ≈ Gαtrans2, with Gαgust and Gαo at the limits of detection (>100-fold lower than Gαi2). Small interfering RNA knockdowns in HASM showed losses of [Ca(2+)]i and ERK1/2 signaling when Gαi1, Gαi2, or Gαi3 were reduced. Gαtrans1 and Gαtrans2 knockdowns had no effect on [Ca(2+)]i and a minimal, transient effect on ERK1/2 phosphorylation. Furthermore, Gαgust and Gαo knockdowns did not affect any TAS2R signaling. In overexpression experiments in human embryonic kidney-293T cells, we confirmed an agonist-dependent physical interaction between TAS2R14 and Gαi2. ASM cells from transgenic mice expressing a peptide inhibitor of Gαi2 had attenuated relaxation to TAS2R agonist. These data indicate that, unlike in taste cells, TAS2Rs couple to the prevalent G proteins, Gαi1, Gαi2, and Gαi3, with no evidence for functional coupling to Gαgust. This absence of function for the "canonical" TAS2R G protein in HASM may be due to the very low expression of Gαgust, indicating that TAS2Rs can optionally couple to several G proteins in a cell type-dependent manner contingent upon G protein expression.

  13. Simulation and control of a helicopter operating in a ship airwake

    Lee, Dooyong

    This thesis describes a study in simulation and control of a helicopter operating in proximity to a ship. The helicopter/ship combination used in the study is a UH-60A helicopter operating off an LHA class ship. This represents the same aircraft ship combination used in the JSHIP program. The flight dynamics model is based on the GENHEL software and this flight dynamics model has been updated to include high-order dynamic inflow model and gust penetration effects of the ship airwake. To simulate the pilot control inputs for typical shipboard operations, an optimal control model of the human pilot is developed. The pilot model can be tuned to achieve different tracking performances based on a desired crossover frequency in each control axis and is designed to operate over a range of airspeeds using a simple gain scheduling algorithm. The pilot model is then used to predict pilot workload for shipboard operations in two different wind-over-deck conditions. Validation studies are conducted using both time and frequency domain analyses to understand the impact of a time-varying ship airwake on the pilot control activity for the approach and departure operations. The pilot control input autospectra predicted from the simulation model are compared to those of flight test data from the JSHIP program. It is found that the control activities are similar in low frequency range but underestimate in magnitude in the high frequency range (over 1.5 Hz). There is clear evidence that the human pilot is continually moving cyclic stick in the maneuver. At this stage of the study no attempt has been made to optimize the parameters of the human pilot model. The paper also discusses the application of a stochastic airwake model for more efficient simulation. This new airwake model is derived from the simulation with the full CFD airwake by extracting an equivalent six-dimensional gust vector. The spectral properties of the gust components are then analyzed, and shaping filters are

  14. Uncertainty management for aerial vehicles: Coordination, deconfliction, and disturbance rejection

    Panyakeow, Prachya

    The presented dissertation aims to develop control algorithms that deal with three types of uncertainties managements. First, we examine the situation when unmanned aerial vehicles (UAVs) fly through uncertain environments that contain both stationary and moving obstacles. Moreover, a guarantee of collision avoidance is necessary when UAVs operate in close proximity of each other. Second, we look at the communication uncertainty among the network of cooperative UAVs and the efforts to establish and maintain the connectivity throughout their entire missions. Third, we explore the scenario when the aircraft flies through wind gust. The introduction of an appropriate control scheme to actively alleviate the gust loads can result into weight reduction and consequently lower the fuel cost. In the first part of this dissertation, we develop a deconfliction algorithm that guarantees collision avoidance between a pair of constant speed unicycle-type UAVs as well as convergence to the desired destination for each UAV in presence of static obstacles. We use a combination of navigation and swirling functions to direct the unicycle vehicles along the planned trajectories while avoiding inter-vehicle collisions. The main feature of our contribution is proposing means of designing a deconfliction algorithm for unicycle vehicles that more closely capture the dynamics of constant speed UAVs as opposed to double integrator models. Specifically, we consider the issue of UAV turn-rate constraints and proceed to explore the selection of key algorithmic parameters in order to minimize undesirable trajectories and overshoots induced by the avoidance algorithm. The avoidance and convergence analysis of the proposed algorithm is then performed for two cooperative UAVs and simulation results are provided to support the viability of the proposed framework for more general mission scenarios. For the uncertainty of the UAV network, we provides two approaches to establish connectivity among a

  15. Aerostructural optimization of a morphing wing for airborne wind energy applications

    Fasel, U.; Keidel, D.; Molinari, G.; Ermanni, P.


    Airborne wind energy (AWE) vehicles maximize energy production by constantly operating at extreme wing loading, permitted by high flight speeds. Additionally, the wide range of wind speeds and the presence of flow inhomogeneities and gusts create a complex and demanding flight environment for AWE systems. Adaptation to different flow conditions is normally achieved by conventional wing control surfaces and, in case of ground generator-based systems, by varying the reel-out speed. These control degrees of freedom enable to remain within the operational envelope, but cause significant penalties in terms of energy output. A significantly greater adaptability is offered by shape-morphing wings, which have the potential to achieve optimal performance at different flight conditions by tailoring their airfoil shape and lift distribution at different levels along the wingspan. Hence, the application of compliant structures for AWE wings is very promising. Furthermore, active gust load alleviation can be achieved through morphing, which leads to a lower weight and an expanded flight envelope, thus increasing the power production of the AWE system. This work presents a procedure to concurrently optimize the aerodynamic shape, compliant structure, and composite layup of a morphing wing for AWE applications. The morphing concept is based on distributed compliance ribs, actuated by electromechanical linear actuators, guiding the deformation of the flexible—yet load-carrying—composite skin. The goal of the aerostructural optimization is formulated as a high-level requirement, namely to maximize the average annual power production per wing area of an AWE system by tailoring the shape of the wing, and to extend the flight envelope of the wing by actively alleviating gust loads. The results of the concurrent multidisciplinary optimization show a 50.7% increase of extracted power with respect to a sequentially optimized design, highlighting the benefits of morphing and the

  16. Small UAS-Based Wind Feature Identification System Part 1: Integration and Validation

    Leopoldo Rodriguez Salazar


    Full Text Available This paper presents a system for identification of wind features, such as gusts and wind shear. These are of particular interest in the context of energy-efficient navigation of Small Unmanned Aerial Systems (UAS. The proposed system generates real-time wind vector estimates and a novel algorithm to generate wind field predictions. Estimations are based on the integration of an off-the-shelf navigation system and airspeed readings in a so-called direct approach. Wind predictions use atmospheric models to characterize the wind field with different statistical analyses. During the prediction stage, the system is able to incorporate, in a big-data approach, wind measurements from previous flights in order to enhance the approximations. Wind estimates are classified and fitted into a Weibull probability density function. A Genetic Algorithm (GA is utilized to determine the shaping and scale parameters of the distribution, which are employed to determine the most probable wind speed at a certain position. The system uses this information to characterize a wind shear or a discrete gust and also utilizes a Gaussian Process regression to characterize continuous gusts. The knowledge of the wind features is crucial for computing energy-efficient trajectories with low cost and payload. Therefore, the system provides a solution that does not require any additional sensors. The system architecture presents a modular decentralized approach, in which the main parts of the system are separated in modules and the exchange of information is managed by a communication handler to enhance upgradeability and maintainability. Validation is done providing preliminary results of both simulations and Software-In-The-Loop testing. Telemetry data collected from real flights, performed in the Seville Metropolitan Area in Andalusia (Spain, was used for testing. Results show that wind estimation and predictions can be calculated at 1 Hz and a wind map can be updated at 0.4 Hz

  17. Computation of wind-induced vibrations of flexible shells and membranous structures

    Glück, M.; Breuer, M.; Durst, F.; Halfmann, A.; Rank, E.


    A partitioned coupling approach for time-dependent fluid-structure interactions is applied to thin shells and membranous structures with large displacements. The frame algorithm connects a three-dimensional, finite volume-based multi-block flow solver for incompressible fluids with a finite element code for geometrically nonlinear structural problems using a commercial coupling interface. Thus a high modularity is achieved and the whole range of opportunities with these two powerful codes - each of them highly adapted to its specific field of application - can be used also for coupled simulations. Two completely different configurations were investigated. First, the coupling algorithm was applied to an academic test configuration consisting of one, two, and three flexible L-shaped plates being loaded by a steady far-field flow. Various investigations were carried out at different Reynolds numbers /(Re=50,200, and 500) in order to study phenomena such as vortex shedding, resonance, influence of the interaction between several flexible plates, whereas the second and third plates were placed in the wake of the first. The second part of the paper shows that in principle the coupling procedure can also deal with real-life structures as they occur in civil engineering. A membranous roof of glass-fiber synthetics with a complex shape was exposed to a time-dependent wind gust from diagonally above which was superimposed on a constant basic wind flow parallel to the ground. The structural model contains the pre-stressed textile roof including the taut cables at its circumference which are fastened at the pylons. As a structural response, the wind gust led to a displacement of the textile roof which disappeared again when the gust subsided. With the coupled algorithm proposed in the paper it is possible to study dynamic interactions for engineering applications.

  18. Small UAS-Based Wind Feature Identification System Part 1: Integration and Validation

    Rodriguez Salazar, Leopoldo; Cobano, Jose A.; Ollero, Anibal


    This paper presents a system for identification of wind features, such as gusts and wind shear. These are of particular interest in the context of energy-efficient navigation of Small Unmanned Aerial Systems (UAS). The proposed system generates real-time wind vector estimates and a novel algorithm to generate wind field predictions. Estimations are based on the integration of an off-the-shelf navigation system and airspeed readings in a so-called direct approach. Wind predictions use atmospheric models to characterize the wind field with different statistical analyses. During the prediction stage, the system is able to incorporate, in a big-data approach, wind measurements from previous flights in order to enhance the approximations. Wind estimates are classified and fitted into a Weibull probability density function. A Genetic Algorithm (GA) is utilized to determine the shaping and scale parameters of the distribution, which are employed to determine the most probable wind speed at a certain position. The system uses this information to characterize a wind shear or a discrete gust and also utilizes a Gaussian Process regression to characterize continuous gusts. The knowledge of the wind features is crucial for computing energy-efficient trajectories with low cost and payload. Therefore, the system provides a solution that does not require any additional sensors. The system architecture presents a modular decentralized approach, in which the main parts of the system are separated in modules and the exchange of information is managed by a communication handler to enhance upgradeability and maintainability. Validation is done providing preliminary results of both simulations and Software-In-The-Loop testing. Telemetry data collected from real flights, performed in the Seville Metropolitan Area in Andalusia (Spain), was used for testing. Results show that wind estimation and predictions can be calculated at 1 Hz and a wind map can be updated at 0.4 Hz. Predictions

  19. Small UAV Research and Evolution in Long Endurance Electric Powered Vehicles

    Logan, Michael J.; Chu, Julio; Motter, Mark A.; Carter, Dennis L.; Ol, Michael; Zeune, Cale


    This paper describes recent research into the advancement of small, electric powered unmanned aerial vehicle (UAV) capabilities. Specifically, topics include the improvements made in battery technology, design methodologies, avionics architectures and algorithms, materials and structural concepts, propulsion system performance prediction, and others. The results of prototype vehicle designs and flight tests are discussed in the context of their usefulness in defining and validating progress in the various technology areas. Further areas of research need are also identified. These include the need for more robust operating regimes (wind, gust, etc.), and continued improvement in payload fraction vs. endurance.

  20. Performance comparison of control schemes for variable-speed wind turbines

    Bottasso, C. L.; Croce, A.; Savini, B.


    We analyze the performance of different control schemes when applied to the regulation problem of a variable-speed representative wind turbine. In particular, we formulate and compare a wind-scheduled PID, a LQR controller and a novel adaptive non-linear model predictive controller, equipped with observers of the tower states and wind. The simulations include gusts and turbulent winds of varying intensity in nominal as well as off-design operating conditions. The experiments highlight the possible advantages of model-based non-linear control strategies.

  1. Performance comparison of control schemes for variable-speed wind turbines

    Bottasso, C L; Croce, A; Savini, B [Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano, Via La Masa 34 I-20156 Milan (Italy)


    We analyze the performance of different control schemes when applied to the regulation problem of a variable-speed representative wind turbine. In particular, we formulate and compare a wind-scheduled PID, a LQR controller and a novel adaptive non-linear model predictive controller, equipped with observers of the tower states and wind. The simulations include gusts and turbulent winds of varying intensity in nominal as well as off-design operating conditions. The experiments highlight the possible advantages of model-based non-linear control strategies.

  2. Design of a digital ride quality augmentation system for a commuter aircraft

    Hammond, T. A.; Downing, D. R.; Amin, S. P.; Paduano, J.


    Commuter aircraft with low wing loading that operate at low altitudes are particularly susceptible to unwanted accelerations caused by atmospheric gusts. This paper describes the design and analysis of a longitudinal digital Ride Quality Augmentation System (RQAS). The RQAS designs were conducted for a Cessna 402B aircraft using the flaps and the elevator as the control surfaces. The designs are generated using linear quadratic Gaussian theory and analyzed in both the time and frequency domains. Nominal designs are presented at five flight conditions that cover a total mission. Trade-off studies are conducted to investigate the effect of sample time, computational delay time, servo bandwidth and control power.

  3. A Status Review of the Commercial Supersonic Technology (CST) Aeroservoelasticity (ASE) Project

    Silva, Walter A.; Sanetrik, Mark D.; Chwalowski, Pawel; Funk, Christy; Keller, Donald F.; Ringertz, Ulf


    An overview of recent progress regarding the computational aeroelastic and aeroservoelastic (ASE) analyses of a low-boom supersonic configuration is presented. The overview includes details of the computational models developed to date with a focus on unstructured CFD grids, computational aeroelastic analyses, sonic boom propagation studies that include static aeroelastic effects, and gust loads analyses. In addition, flutter boundaries using aeroelastic Reduced-Order Models (ROMs) are presented at various Mach numbers of interest. Details regarding a collaboration with the Royal Institute of Technology (KTH, Stockholm, Sweden) to design, fabricate, and test a full-span aeroelastic wind-tunnel model are also presented.

  4. A Temporal and Spatial Analysis of Wave-Generated Foam Patterns in the Surf Zone


    tilted downward in the offshore direction (Nadaoka et al. 1989). Nadaoka et al. (1989) also observed that the ODEs can reach the bottom and are a...150 200 250 300 350 12 (outlined in black in Figure 4). It is necessary to use a search box because the UAV moves slightly with wind gusts. Each...approximately 0.25 to 0.64 meters. The areas are also consistent between the top boxes, which are located farther offshore , and the bottom boxes, which

  5. Analyze Light in August by Lacan's Theory of Mirror Stage



    Being one of the greatest 20th century writers, William Faulkner was rewarded with the Nobel Prize for literature in 1949. For his whole life, he created many novels which were given high appraisal and remained popular up to today. Light in Au?gust, carrying as the representative of Faulkner's novels, is not an exception as to the digging about individual's formation about identity. In the light of Lacan's theory of Mirror Stage, this paper tries to evaluate Faulkner's discussion over the forma-tion of individual's identity with Joe Christmas as the example.

  6. Abstracts


    1.Changes Come from Turmoils, Hopes Reside in Stagnancy,by Zhu Feng a professor at the Schobl ofInternational t/elations, t'eklng University, anu a member oi ecutorlai Doaro oi Peaceand Development and a gust researcher of CDPS. In 2011, "the Arab Spring" changed the geopolitical ecology of the Middle East and North Africa. The U.S. stepped up readjustment to its global strategy with a high-sounding voice proclaimed its "return to Asia Pacific". A great surge was felt in the political trend of thoughts in the world, and the world was still faced with various terrorist threats.

  7. Branding, packaging o sabor? Relació entre el reconeixement de la marca de les begudes, el packaging i la percepció del sabor.

    Sánchez Ortega, Kevin


    Els cinc sentits, presents a l'ésser humà des del naixement, tenen funcions úniques que altres sentits no poden suplir. La vista, el gust i l'olfacte, sentits estudiats en aquesta investigació, son fonamentals per la publicitat, i més pel sector dels aliments i les begudes. Es pot reconèixer a cegues una marca de begudes? I un envàs sense colors ni elements identificatius? Quin paper té la memòria en els consumidors i com influeix en els sentits? Per què hi ha gent que escolta colors? I per q...

  8. Oscar Wilde como artesano: la mediación de la identidad a través de los objetos en "The picture of Dorian Gray" y "The importance of being Earnest"

    Zubieta Jarén, Bárbara


    Uno de los aspectos más documentados a la hora de estudiar las obras de Óscar Wilde en profundidad ha sido el concepto de máscara u ocultación. Este concepto fue tratado a su vez por el propio escritor en su ensayo titulado The Truth of Masks (1891), donde analiza, entre otras cosas, la puesta en escena y los objetos que aparecen a la hora de llevar a cabo la representación de las obras de teatro de Shakespeare. Por otra parte, no es necesario señalar que Wilde es harto reconocido por su gust...

  9. Nonlinear platoon control of Arduino cars with range-limited sensors

    Yue, Wei; Guo, Ge; Wang, Liyuan; Wang, Wei


    This paper investigates the problem of platoon control with sensor range limitation. A nonlinear vehicular platoon model is established, in which the sensing range constraint described by a piecewise nonlinear function is involved. Then a robust nonlinear control design method is proposed based on a disturbance observer and the backstepping technique. The results are obtained in the context of both individual vehicle stability and platoon string stability analysis, which can lead to substantially enhanced platoon control performance with a guaranteed level of attenuation of the disturbance caused by lead vehicle acceleration and wind gust. The effectiveness of the method has been shown by numerical simulations and experiments carried out with Arduino cars.

  10. Spectrum Fatigue of 7075-T651 Aluminum Alloy under Overloading and Underloading


    laboratory air of relative humidity about 50 percent and aqueous 1 percent NaCl solution of pH 2 at ambient temperature. The loading frequency was about 5 Hz...up. On the ground, the lower wing skin of the aircraft is under compression. During flight, variable loads due to gust are superimposed on a mean...and hence reduce the stress intensity range K. Nordmark and Fricke (18) produced strong evidence that this was the reason for crack arrest of 7475

  11. War casualties on the home front

    Brenda J. Flinn


    On May 12, 1942, at Christopher coal mine No. 3 in Osage, West Virginia, a continent away from the frontlines of World War II, Superintendent Ed O'Neil saw the mine ventilation fan suddenly run backwards, propelled by a strong gust of air that tore the belt off the huge blower. The second shift mantrip of 115 coal miners, traversing the drift mouth for the 3:00 p.m. shift, ground to an uneasy halt. The article recounts the tragic consequences of this incident. It also tells of other events affecting coal miners during World War I and World War II.

  12. Rational calibration of three IEC extreme load cases

    Larsen, Gunner Chr.; Hansen, Kurt Schaldemose


    This paper presents a rational and consistent calibration of the IEC 61400-1 extreme load cases EOG, EWS and ECD based on a system of asymptotic statistical models on closed form. The models are based on simple and easily accessible mean wind speed and turbulence characteristics of the atmospheric...... boundary layer. Using the wind climate characteristics prescribed in the IEC 61400-1 code as input to the statistical model complex ensures consistency between the specified wind climate and the proposed extreme gust amplitudes. Differences and equalities between the present IEC specifications and proposed...

  13. Single-sided natural ventilation driven by wind pressure and temperature difference

    Larsen, Tine Steen; Heiselberg, Per


    direction, the turbulence characteristics in the wind and the pressure variations caused by e.g. wind gusts. Finally, it also depends on the size, type and location of the opening. Many of these parameters are unsteady which makes the calculation of air-change rates even more complicated. In this work, full......-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending...

  14. Estudio Exploratorio de los Sistemas de Calidad en Escuelas Primarias

    Cabello Amaya, Lizbeth


    El progreso de una comunidad se mide por la calidad de la educación, de esta dependerá el bienestar de las comunidades, el nivel cultural y el desarrollo económico de los pueblos y a ella está supeditado el desempeño de excelencia que exige la competitividad de un mundo reducido, nos guste o no, a una pequeña aldea global. (Fernández 2003) Actualmente la calidad en la educación es un aspecto que está demandando mayor atención. Ya que de la calidad que reciben los estudiantes se fundamenta el ...

  15. Operating Cell Temperature Determination in Flat-Plate Photovoltaic Modules; Calculo de la Temperature de Operacion de Celulas Solares en un Panel Fotovoltaico Plano

    Chenlo, F.


    Two procedures (simplified and complete) to determine the operating cell temperature in photovoltaic modules operating in real conditions assuming isothermal stationary modules are presented in this work. Some examples are included that show the dependence of this temperature on several environment (sky, ground and ambient temperatures, solar irradiance, wind speed, etc.) and structural (module geometry and size, encapsulating materials, antirreflexive optical coatings, etc) factors and also on electrical module performance. In a further step temperature profiles for non-isothermal modules are analysed besides transitory effects due to variable irradiance and wind gusts. (Author)

  16. A Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics. Part 2. User’s Manual


    TGOV governor IGOV Control variables 100 90I 91& 91,---q)Q; rotor #1 ic is 200 a.aas QN2 rotor #2 2C1C 2C1S 2C4 DELF 64airframe ELE St, DELA & DELR ~ CT...rotor sY1 2110 orotor -i2 2C1S DELF aircraft DELE DELA DELR &r - CT a DELO pilot DELC DELS DELP DELT Gust components UG uG VG vG WG wG -75- For the

  17. Perturbation Dynamics and Its Application for Parachute-Munition System


    The nine-degree-freedom dynamic model of the parachute-munition system is developed by the theories and the analysis methods of parachute dynamics and multibody dynamics. On the basis of the above model, a linear five-degree-offreedom dynamic model is developed by linearization at the steady state. A new algorithm, which can be fused with submunition kinematics and used in target identification, is developed by the principle of parachute dynamics. The simulation program is developed and used to remove the influence of wind gust on hitting accuracy. The successful airdrop test demonstrates that the new method can be used in the guidance of smart munition.

  18. 2006年11月7日に北海道佐呂間町で発生した竜巻災害

    山本, 晴彦; Haruhiko, YAMAMOTO; 山口大学農学部; Faculty of Agriculture, Yamaguchi University


    Assocated with the passage of cumulonimbus cloud on Novmber 7, 2006, a tornado was spawned in Saroma Town. The recorded mean wind speed was 8m/s (13:30) at the Saroma AMeDAS station. The station is located only 1.5km away from the path of the tornado, however, the gust by the tornado was not observed. Air temperature drop of about 1℃/20minutes (13:30-50) was also recorded. The length of the tornad path was estimated as 1km and the maximum width 250m from damage survey. The number of dead pers...

  19. Rational calibration of three IEC extreme load cases

    Larsen, Gunner Chr.; Hansen, Kurt Schaldemose


    This paper presents a rational and consistent calibration of the IEC 61400-1 extreme load cases EOG, EWS and ECD based on a system of asymptotic statistical models on closed form. The models are based on simple and easily accessible mean wind speed and turbulence characteristics of the atmospheric...... boundary layer. Using the wind climate characteristics prescribed in the IEC 61400-1 code as input to the statistical model complex ensures consistency between the specified wind climate and the proposed extreme gust amplitudes. Differences and equalities between the present IEC specifications and proposed...

  20. El autismo social común denominador

    Castillo Cubillos, Luis Enrique


    Las megatendencias de finales del siglo XX, y comienzos del siglo XXI tienen su meridiano en la globalización, una transición, un nuevo orden, época. Las desigualdades a escala mundial del ingreso y el nivel de vida han llegado a proporciones grotescas, y las Naciones Unidas afirman que la mundialización es demasiado importante para dejarla sin gestión, gústenos o no nos guste el mercado, la tarea que les corresponde a los economistas es considerar como regularlo, desde la perspectiva de la j...

  1. Tropical Cyclone Report, 1986.


    Enewetak 3-08-1) at 120024Z July shows the tropical Atoll . It persisted into the next day when it was depression. The first warning was issued at...were 28 kt (14 m/sec) with nortn, formed a vortex 600 nm (1111 km) east of gusts to 48 kt (25 m/sec). There was limited damage Kwaj-diein Atoll in the...However, Ben did not track as forecast, but instead southeast of Kwajalein Atoll in the Marshall Islands. moved north-northwestward until the 20th at G00Z

  2. The use of differential pressure feedback in an automatic flight control system

    Levy, D. W.; Roskam, J.; Finn, P. D.


    A feasibility study has been performed to evaluate the performance of a system whereby a control surface is positioned with differential pressure as the feedback variable. Analogous to a position command system, the control surface is commanded to move until a certain differential pressure is achieved at a given point on the surface. Frequency response tests and theoretical considerations indicate that the pressure feedback transfer function is first order, with a break frequency up to 50 rad/sec. There exist applications to the outer loops of flight control systems as well. Stability augmentation, gust alleviation, and stall prevention appear to be possible by feeding back differential pressure across lifting and control surfaces.

  3. An approach to the synthesis of separate surface automatic flight control systems.

    Roskam, J.; Henry, S.


    A method is presented for the analysis of separate surface automatic flight control systems. The feasibility of such systems is demonstrated by the analysis of an example system, a separate surface wing-leveler for a Cessna 172. This example system employs a separate surface aileron with 15% of the basic airplane roll control power. A 90% reduction in bank-angle gust response can be obtained when compared with the basic airplane. The system does not feed back to the pilot's wheel. When failed (even hardover) the pilot retains more than adequate control of the airplane.

  4. Aircraft automatic flight control system with model inversion

    Smith, G. A.; Meyer, George


    A simulator study was conducted to verify the advantages of a Newton-Raphson model-inversion technique as a design basis for an automatic trajectory control system in an aircraft with highly nonlinear characteristics. The simulation employed a detailed mathematical model of the aerodynamic and propulsion system performance characteristics of a vertical-attitude takeoff and landing tactical aircraft. The results obtained confirm satisfactory control system performance over a large portion of the flight envelope. System response to wind gusts was satisfactory for various plausible combinations of wind magnitude and direction.

  5. Aircraft automatic flight control system with model inversion

    Smith, G. A.; Meyer, George


    A simulator study was conducted to verify the advantages of a Newton-Raphson model-inversion technique as a design basis for an automatic trajectory control system in an aircraft with highly nonlinear characteristics. The simulation employed a detailed mathematical model of the aerodynamic and propulsion system performance characteristics of a vertical-attitude takeoff and landing tactical aircraft. The results obtained confirm satisfactory control system performance over a large portion of the flight envelope. System response to wind gusts was satisfactory for various plausible combinations of wind magnitude and direction.

  6. Marketing sensorial en el punto de venta: el caso Hollister

    Romera Ferrera, Jennifer


    El present estudi tracta sobre l'anomenat màrqueting sensorial aplicat a un punt de venda, concretament en botigues de roba. S'hi repassen algunes teories, casos i estudis previs sobre la utilització de determinades tècniques de màrqueting aplicades al punt de venda general, relacionat amb l'experiència del consumidor. També s'analitzen les característiques i peculiaritats de cada sentit (excloent el gust). Posteriorment, es realitza un estudi pràctic i una prova experimental sobre el cas con...

  7. Elemental magic, v.2 the technique of special effects animation

    Gilland, Joseph


    Design beautiful, professional-level animated effects with these detailed step-by-step tutorials from former Disney animator and animated effects expert Joseph Gilland. Filled with beautiful, full-color artwork, Elemental Magic, Volume II, breaks down the animated effect process from beginning to end-including booming explosions, gusting winds, magical incantations, and raging fires. He also breaks down the process of effects ""clean-up,"" as well as timing and frame rates. The companion website includes real-time footage of the author lecturing as he animates the drawings from the

  8. Material matters: Controllable rubber trailing edge flap regulates load on wind turbine blades

    Aagaard Madsen, Helge


    In wind farms, nearby wind turbines exert considerable influence and generate turbulence on turbine blades. Because the blades are so long, there can be considerable differences in localized loading from the gusts along the blade. The Risø DTU researchers has developed a controllable rubber...... trailing edge flap, known as CRTEF. The trailing edge blade design is expected to help mitigate localized loading, and its molded rubber design, the sharp trailing edge, produces less noise and greater output. With CRTEF, the blade automatically has a completely sharp edge. The elastic flap tested...

  9. Maya Studio Projects Dynamics

    Palamar, Todd


    The only hands-on book devoted to mastering Maya's dynamics tools for water, wind, and fire. In the world of animation, the ability to create realistic water, wind, and fire effects is key. Autodesk Maya software includes powerful dynamics tools that have been used to design breathtaking effects for movies, games, commercials, and short films. This professional guide teaches you the primary techniques you need to make the most of Maya's toolkit, so you'll soon be creating water that ripples, gusting winds and gentle breezes, and flickering fires the way Hollywood pros do. The one-of-a-kind boo

  10. Optimal Vibration Control of Civil Engineering Structures

    Thesbjerg, Leo

    In designing large civil engineering structures, an important consideration is prospective dynamic loadings which may include earthquake ground motion, wind gusts, severe sea states and moving vehicles, rotating and reciprocating machinery and others. successful design of such structures requires...... providing for the safety and integrity of the structure, and in some cases also providing for a measure of comfort for the occupants during such loading which the structure and its occupants must endure. Due to these uncertainties, the civil engineering community has traditionally adopted a very...

  11. Algunos efectos de la precipitación del huracán Paulina en Acapulco, Guerrero

    Lucía Guadalupe Matías Ramírez


    Full Text Available During three days in October (6th-10th 1997, the hurricane Pauline affected the coastal areas of Chiapas, Oaxaca and Guerrero. The force of Shis hurricane graded 4 fn the Saffir-Simpson scale, thus reaching the category of extremely dangerous. Its winds were as strong as 210 kilometers per hour and gusts of 240 kilometers per hour. The associated rain registered the extraordinary amount of 400 mm in Acapulco, in only five hours. Among the major consequences of such rainfall worth mentioning are: runoffs, landslides, floods and 120 human losses. Total damage in this port was estimated at ca, 300 million pesos.

  12. Wing tucks are a response to atmospheric turbulence in the soaring flight of the steppe eagle Aquila nipalensis

    Reynolds, Kate V.; Thomas, Adrian L. R.; Taylor, Graham K.


    Turbulent atmospheric conditions represent a challenge to stable flight in soaring birds, which are often seen to drop their wings in a transient motion that we call a tuck. Here, we investigate the mechanics, occurrence and causation of wing tucking in a captive steppe eagle Aquila nipalensis, using ground-based video and onboard inertial instrumentation. Statistical analysis of 2594 tucks, identified automatically from 45 flights, reveals that wing tucks occur more frequently under conditions of higher atmospheric turbulence. Furthermore, wing tucks are usually preceded by transient increases in airspeed, load factor and pitch rate, consistent with the bird encountering a headwind gust. The tuck itself immediately follows a rapid drop in angle of attack, caused by a downdraft or nose-down pitch motion, which produces a rapid drop in load factor. Positive aerodynamic loading acts to elevate the wings, and the resulting aerodynamic moment must therefore be balanced in soaring by an opposing musculoskeletal moment. Wing tucking presumably occurs when the reduction in the aerodynamic moment caused by a drop in load factor is not met by an equivalent reduction in the applied musculoskeletal moment. We conclude that wing tucks represent a gust response precipitated by a transient drop in aerodynamic loading. PMID:25320064

  13. Design of Attitude Control System for UAV Based on Feedback Linearization and Adaptive Control

    Wenya Zhou


    Full Text Available Attitude dynamic model of unmanned aerial vehicles (UAVs is multi-input multioutput (MIMO, strong coupling, and nonlinear. Model uncertainties and external gust disturbances should be considered during designing the attitude control system for UAVs. In this paper, feedback linearization and model reference adaptive control (MRAC are integrated to design the attitude control system for a fixed wing UAV. First of all, the complicated attitude dynamic model is decoupled into three single-input single-output (SISO channels by input-output feedback linearization. Secondly, the reference models are determined, respectively, according to the performance indexes of each channel. Subsequently, the adaptive control law is obtained using MRAC theory. In order to demonstrate the performance of attitude control system, the adaptive control law and the proportional-integral-derivative (PID control law are, respectively, used in the coupling nonlinear simulation model. Simulation results indicate that the system performance indexes including maximum overshoot, settling time (2% error range, and rise time obtained by MRAC are better than those by PID. Moreover, MRAC system has stronger robustness with respect to the model uncertainties and gust disturbance.

  14. Shade Effects on the Dispersal of Airborne Hemileia vastatrix Uredospores.

    Boudrot, Audrey; Pico, Jimmy; Merle, Isabelle; Granados, Eduardo; Vílchez, Sergio; Tixier, Philippe; Filho, Elías de Melo Virginio; Casanoves, Fernando; Tapia, Ana; Allinne, Clémentine; Rice, Robert A; Avelino, Jacques


    Hemileia vastatrix caused a severe epidemic in Central America in 2012-13. The gradual development of that epidemic on nearly a continental scale suggests that dispersal at different scales played a significant role. Shade has been proposed as a way of reducing uredospore dispersal. The effect of shade (two strata: Erythrina poeppigiana below and Chloroleucon eurycyclum above) and full sun on H. vastatrix dispersal was studied with Burkard traps in relation to meteorological records. Annual and daily patterns of dispersal were observed, with peaks of uredospore capture obtained during wet seasons and in the early afternoon. A maximum of 464 uredospores in 1 day (in 14.4 m(3) of air) was recorded in October 2014. Interactions between shade/full sun and meteorological conditions were found. Rainfall, possibly intercepted by tree cover and redistributed by raindrops of higher kinetic energy, was the main driver of uredospore dispersal under shade. Wind gusts reversed this effect, probably by inhibiting water accumulation on leaves. Wind gusts also promoted dispersal under dry conditions in full sun, whereas they had no effect under shaded conditions, probably because the canopy blocked the wind. Our results indicate the importance of managing shade cover differentially in rainy versus dry periods to control the dispersal of airborne H. vastatrix uredospores.

  15. Transient Performance of a Vertical Axis Wind Turbine

    Onol, Aykut; Yesilyurt, Serhat


    A coupled CFD/rotor dynamics modeling approach is presented for the analysis of realistic transient behavior of a height-normalized, three-straight-bladed VAWT subject to inertial effects of the rotor and generator load which is manipulated by a feedback control under standardized wind gusts. The model employs the k- ɛ turbulence model to approximate unsteady Reynolds-averaged Navier-Stokes equations and is validated with data from field measurements. As distinct from related studies, here, the angular velocity is calculated from the rotor's equation of motion; thus, the dynamic response of the rotor is taken into account. Results include the following: First, the rotor's inertia filters large amplitude oscillations in the wind torque owing to the first-order dynamics. Second, the generator and wind torques differ especially during wind transients subject to the conservation of angular momentum of the rotor. Third, oscillations of the power coefficient exceed the Betz limit temporarily due to the energy storage in the rotor, which acts as a temporary buffer that stores the kinetic energy like a flywheel in short durations. Last, average of transient power coefficients peaks at a smaller tip-speed ratio for wind gusts than steady winds. This work was supported by the Sabanci University Internal Research Grant Program (SU-IRG-985).

  16. Calculation of design load for the MOD-5A 7.3 mW wind turbine system

    Mirandy, L.; Strain, J. C.


    Design loads are presented for the General Electric MOD-SA wind turbine. The MOD-SA system consists of a 400 ft. diameter, upwind, two-bladed, teetered rotor connected to a 7.3 mW variable-speed generator. Fatigue loads are specified in the form of histograms for the 30 year life of the machine, while limit (or maximum) loads have been derived from transient dynamic analysis at critical operating conditions. Loads prediction was accomplished using state of the art aeroelastic analyses developed at General Electric. Features of the primary predictive tool - the Transient Rotor Analysis Code (TRAC) are described in the paper. Key to the load predictions are the following wind models: (1) yearly mean wind distribution; (2) mean wind variations during operation; (3) number of start/shutdown cycles; (4) spatially large gusts; and (5) spatially small gusts (local turbulence). The methods used to develop statistical distributions from load calculations represent an extension of procedures used in past wind programs and are believed to be a significant contribution to Wind Turbine Generator analysis. Test/theory correlations are presented to demonstrate code load predictive capability and to support the wind models used in the analysis. In addition MOD-5A loads are compared with those of existing machines. The MOD-5A design was performed by the General Electric Company, Advanced Energy Program Department, under Contract DEN3-153 with NASA Lewis Research Center and sponsored by the Department of Energy.

  17. Aeroservoelastic Testing of a Sidewall Mounted Free Flying Wind-Tunnel Model

    Scott, Robert C.; Vetter, Travis K.; Penning, Kevin B.; Coulson, David A.; Heeg, Jennifer


    A team comprised of the Air Force Research Laboratory (AFRL), Northrop Grumman, Lockheed Martin, and the NASA Langley Research Center conducted three j wind-tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, exible vehicles. In the rst of these three tests, a semispan, aeroelastically scaled, wind-tunnel model of a ying wing SensorCraft vehi- cle was mounted to a force balance to demonstrate gust load alleviation. In the second and third tests, the same wing was mated to a new, multi-degree-of-freedom, sidewall mount. This mount allowed the half-span model to translate vertically and pitch at the wing root, allowing better simulation of the full span vehicle's rigid-body modes. Gust Load Alleviation (GLA) and Body Freedom Flutter (BFF) suppression were successfully demonstrated. The rigid body degrees-of-freedom required that the model be own in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort.

  18. Modified Adaptive Control for Region 3 Operation in the Presence of Wind Turbine Structural Modes

    Frost, Susan Alane; Balas, Mark J.; Wright, Alan D.


    Many challenges exist for the operation of wind turbines in an efficient manner that is reliable and avoids component fatigue and failure. Turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, possibly causing component fatigue and failure. Wind turbine manufacturers are highly motivated to reduce component fatigue and failure that can lead to loss of revenue due to turbine down time and maintenance costs. The trend in wind turbine design is toward larger, more flexible turbines that are ideally suited to adaptive control methods due to the complexity and expense required to create accurate models of their dynamic characteristics. In this paper, we design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed horizontal axis wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the excitation of structural modes in the wind turbine. The control objective is accomplished by collectively pitching the turbine blades. The adaptive collective pitch controller for Region 3 was compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller. The adaptive controller will demonstrate the ability to regulate generator speed in Region 3, while accommodating gusts, and reducing the excitation of certain structural modes in the wind turbine.

  19. Estimated wind speed feed forward control for wind turbine operation optimisation

    Van der Hooft, E.L.; Van Engelen, T.G. [ECN Wind Energy, Petten (Netherlands)


    For a pitch controlled variable speed wind turbine, a feed forward control structure based on the estimation of rotor averaged wind speed has been developed and analyzed. The additional control action will accelerate ordinary rotor speed feedback control to resist disturbances of wind speed turbulence and wind gusts. Wind speed estimation is based on reconstruction of aerodynamic torque from measurements and a priori knowledge of rotor behaviour. The theoretical base arises from the energy balance between captured aerodynamic energy from wind on the one hand and extracted electric energy (generator), stored kinetic energy (rotor inertia) and losses on the other hand. A tabular implementation for use in real-time control has been derived and evaluated by time domain simulations, stability analysis and parametric uncertainty studies. Without stability drawbacks, the proposed method has shown to be a powerful for reduction of rotor speed variations (30-40%) and wind gust suppression. Energy yield increase is feasible (0.9%) if temporarily torque excesses are not allowed.

  20. Effect of unsteady wind on drifting snow: first investigations

    J.-L. Michaux


    Full Text Available Wind is not always a steady flow. It can oscillate, producing blasts. However, most of the current numerical models of drifting snow are constrained by one major assumption: forcing winds are steady and uniform. Moreover, very few studies have been done to verify this hypothesis, because of the lack of available instrumentation and measurement difficulties. Therefore, too little is known about the possible role of wind gust in drifting snow. In order to better understand the effect of unsteady winds, we have performed both experiments at the climatic wind tunnel at the CSTB (Centre Scientifique et Technique des Bâtiments in Nantes, France, and in situ experiments on our experimental high-altitude site, at the Lac Blanc Pass. These experiments were carried out collaboratively with Cemagref (France, Météo-France, and the IFENA (Switzerland. Through the wind tunnel experiments, we found that drifting snow is in a state of permanent disequilibrium in the presence of fluctuating airflows. In addition, the in situ experiments show that the largest drifting snow episodes appear during periods of roughly constant strong wind, whereas a short but strong blast does not produce significant drifting snow.  Key words. Drifting snow, blowing snow, gust, blast, acoustic sensor

  1. Anticipatory and reactive crouching of pea aphids in response to environmental perturbations.

    Ben-Ari, Matan; Talal, Stav; Inbar, Moshe


    Animals use different strategies to deal with changing environmental conditions. While standing and feeding on their host plant, aphids (Hemiptera: Aphididae) may be exposed to detrimental environmental perturbations, such as strong winds. If aphids are forcibly blown off the plant and spend time on the ground, they will face additional dangers by both ground-dwelling predators and detrimental soil temperature. It is therefore adaptive for aphids to behave in a way that lowers the risk of being removed from the plant. We observed that pea aphids (Acyrthosiphon pisum (Harris)) display a specific crouched body posture, previously undescribed, which reduces their chance of being carried off from the plant by sudden winds. We exposed aphids in the laboratory to different cues indicative of a windy environment: wind, plant vibration, and visual stimuli. We found that aphids crouch in two situations: 1) reactively, when they are being pulled by a continuous gust of wind threatening to dislodge them. 2) Anticipatorily, when environmental cues, such as plant vibration or continuous movement near their host plant, may signify that sudden wind gusts are expected. Crouching aphids were less likely to be dislodged by a sudden air stream or plant vibration than were aphids that did not crouch. Crouching thus improves the aphids' chances of remaining on their host plant under unfavorable environmental conditions.

  2. Fixed membrane wings for micro air vehicles: Experimental characterization, numerical modeling, and tailoring

    Stanford, Bret; Ifju, Peter; Albertani, Roberto; Shyy, Wei


    Fixed wing micro air vehicles (wingspan between 10 and 15 cm) are aerodynamically challenging due to the low Reynolds number regime (10 4-10 5) they operate in. The low aspect ratio wings (typically used to maximize area under a size constraint) promote strong tip vortices, and are susceptible to rolling instabilities. Wind gusts can be of the same order of magnitude as the flight speed (10-15 m/s). Standard control surfaces on an empennage must be eliminated for size considerations and drag reduction, and the range of stable center of gravity locations is only a few millimeters long. Membrane aeroelasticity has been identified as a tenable method to alleviate these issues: flexible wing structures with geometric twist (adaptive washout for gust rejection, delayed stall) and aerodynamic twist (adaptive inflation for high lift, larger stability margins) are both considered here. Recent investigations in static aeroelastic characterization, including flight loads, wing deformation, flow structures, aeroelastic-tailoring studies through laminate orientation, as well as unconventional techniques based on membrane pre-tension, are reviewed. Multi-objective optimization aimed at improving lift, drag, and pitching moment considerations is also discussed.

  3. Flying Drosophila stabilize their vision-based velocity controller by sensing wind with their antennae.

    Fuller, Sawyer Buckminster; Straw, Andrew D; Peek, Martin Y; Murray, Richard M; Dickinson, Michael H


    Flies and other insects use vision to regulate their groundspeed in flight, enabling them to fly in varying wind conditions. Compared with mechanosensory modalities, however, vision requires a long processing delay (~100 ms) that might introduce instability if operated at high gain. Flies also sense air motion with their antennae, but how this is used in flight control is unknown. We manipulated the antennal function of fruit flies by ablating their aristae, forcing them to rely on vision alone to regulate groundspeed. Arista-ablated flies in flight exhibited significantly greater groundspeed variability than intact flies. We then subjected them to a series of controlled impulsive wind gusts delivered by an air piston and experimentally manipulated antennae and visual feedback. The results show that an antenna-mediated response alters wing motion to cause flies to accelerate in the same direction as the gust. This response opposes flying into a headwind, but flies regularly fly upwind. To resolve this discrepancy, we obtained a dynamic model of the fly's velocity regulator by fitting parameters of candidate models to our experimental data. The model suggests that the groundspeed variability of arista-ablated flies is the result of unstable feedback oscillations caused by the delay and high gain of visual feedback. The antenna response drives active damping with a shorter delay (~20 ms) to stabilize this regulator, in exchange for increasing the effect of rapid wind disturbances. This provides insight into flies' multimodal sensory feedback architecture and constitutes a previously unknown role for the antennae.

  4. Two cold-season derechoes in Europe

    Gatzen, Christoph; Púčik, Tomas; Ryva, David


    In this study, we apply for the first time the definition of a derecho (Johns and Hirt, 1987) to European cold-season convective storm systems. These occurred on 18 January 2007 and 1 March 2008, respectively, and they are shown to fulfill the criteria of a derecho. Damaging winds were reported over a distance of 1500 km and locally reached F3 intensity. Synoptic analysis for the events reveal strongly forced situations that have been described for cold-season derechoes in the United States. A comparison of swaths of damaging winds, radar structures, detected lightning, cold pool development, and cloud-top temperatures indicates that both derechoes formed along cold fronts that were affected by strong quasi-geostrophic forcing. It seems that the overlap of the cold front position with the strong differential cyclonic vorticity advection at the cyclonic flank of mid-level jet streaks favoured intense convection and high winds. The movement and path width of the two derechoes seemed to be related to this overlap. The wind gust intensity that was also different for both events is discussed and could be related to the component of the mid-level winds perpendicular to the gust fronts.

  5. Assimilating surface observations in a four-dimensional variational Doppler radar data assimilation system to improve the analysis and forecast of a squall line case

    Chen, Xingchao; Zhao, Kun; Sun, Juanzhen; Zhou, Bowen; Lee, Wen-Chau


    This paper examines how assimilating surface observations can improve the analysis and forecast ability of a fourdimensional Variational Doppler Radar Analysis System (VDRAS). Observed surface temperature and winds are assimilated together with radar radial velocity and reflectivity into a convection-permitting model using the VDRAS four-dimensional variational (4DVAR) data assimilation system. A squall-line case observed during a field campaign is selected to investigate the performance of the technique. A single observation experiment shows that assimilating surface observations can influence the analyzed fields in both the horizontal and vertical directions. The surface-based cold pool, divergence and gust front of the squall line are all strengthened through the assimilation of the single surface observation. Three experiments—assimilating radar data only, assimilating radar data with surface data blended in a mesoscale background, and assimilating both radar and surface observations with a 4DVAR cost function—are conducted to examine the impact of the surface data assimilation. Independent surface and wind profiler observations are used for verification. The result shows that the analysis and forecast are improved when surface observations are assimilated in addition to radar observations. It is also shown that the additional surface data can help improve the analysis and forecast at low levels. Surface and low-level features of the squall line—including the surface warm inflow, cold pool, gust front, and low-level wind—are much closer to the observations after assimilating the surface data in VDRAS.

  6. Acute Low Back Pain? Do Not Blame the Weather-A Case-Crossover Study.

    Beilken, Keira; Hancock, Mark J; Maher, Chris G; Li, Qiang; Steffens, Daniel


    To investigate the influence of various weather parameters on the risk of developing a low back pain (LBP) episode. Case-crossover study. Primary care clinics in Sydney, Australia. 981 participants with a new episode of acute LBP. Weather parameters were obtained from the Australian Bureau of Meteorology. Odds ratios (OR) and 95% confidence intervals (95% CI) were derived comparing two exposure variables in the case window-(1) the average of the weather variable for the day prior to pain onset and (2) the change in the weather variable from 2 days prior to 1 day prior to pain onset-with exposures in two control windows (1 week and 1 month before the case window). The weather parameters of precipitation, humidity, wind speed, wind gust, wind direction, and air pressure were not associated with the onset of acute LBP. For one of the four analyses, higher temperature slightly increased the odds of pain onset. Common weather parameters that had been previously linked to musculoskeletal pain, such as precipitation, humidity, wind speed, wind gust, wind direction, and air pressure, do not increase the risk of onset for LBP.

  7. Performance of a grid-connected wind generation system with a robust susceptance controller

    Rahim, A.H.M.A. [Department of Electrical Engineering, K.F. University of Petroleum and Minerals, KFUPM Box 349, Dhahran 31261 (Saudi Arabia); Nowicki, E.P. [Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB (Canada)


    Wind turbine driven induction generators are vulnerable to transient disturbances like wind gusts and low voltages on the system. The fixed capacitor at the generator terminal or the limited support from the grid may not be able to provide the requisite reactive power under these abnormal conditions. This paper presents a susceptance control strategy for a variable speed wound-rotor induction generator which can cater for the reactive power requirement. The susceptance is adjusted through a robust feedback controller included in the terminal voltage driven automatic excitation control circuit. The fixed parameter robust controller design is carried out in frequency domain using multiplicative uncertainty modeling and H{sub {infinity}} norms. The robustness of the controller has been evaluated through optimally tuned PID controllers. Simulation results show that the robust controller can effectively restore normal operation following emergencies like sudden load changes, wind gusts and low voltage conditions. The proposed robust controller has been shown to have adequate fault ride through capabilities in order to be able to meet connection requirements defined by transmission system operators. (author)

  8. Hanford Site climatological data summary 1995 with historical data

    Hoitink, D.J.; Burk, K.W.


    This document presents the climatological data measured at the US Department of Energy`s Hanford Site for calendar year 1995. Pacific Northwest National Laboratory operates the Hanford Meteorology Station and the Hanford Meteorological Monitoring Network from which these data were collected. The information contained herein includes updated historical climatologies for temperature, precipitation, normal and extreme values of temperature and precipitation, and other miscellaneous meteorological parameters. Further, the data are adjunct to and update Hoitink and Burk (1994, 1995); however, Appendix B--Wind Climatology (1994) is excluded. 1995 was warmer than normal, averaging 54.7 F, 1.4 F above normal (53.3 F). For the 12-month period, 8 months were warmer than normal, and 4 were cooler than normal. 1995 was the wettest year on record. Precipitation totaled 12.31 in., 197% of normal (6.26 in.); snowfall totaled 7.7 in., compared to the normal of 13.8 in. The average wind speed during 1995 was 7.8 mph, 0.1 mph above normal (7.7 mph). The peak gust during the year was 61 mph from the south-southwest on December 12. There were 27 days with peak gusts {ge} 40 mph, compared to a yearly average of 26.

  9. Poster 17: Methane storms as a driver of Titan's dune orientation.

    Charnay, Benjamin; Barth, Erika; Rafkin, Scot; Narteau, Clement; Lebonnois, Sebastien; Rodriguez, Sebastien; Courech Du Pont, Sylvain; Lucas, Antoine


    Titan's equatorial regions are covered by eastward oriented linear dunes [1,2]. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs) at these latitudes, oriented westward as trade winds on Earth. We propose that Titan's dune orientation is actually determined by equinoctial tropical methane storms producing a coupling with superrotation and dune formation [3]. Using meso-scale simulations of convective methane clouds [4] with a GCM wind profile featuring the superrotation [5,6], we show that Titan's storms should produce fast eastward gust fronts above the surface. Such gusts dominate the aeolian transport. Using GCM wind calculations and analogies with terrestrial dune fields [7], we show that Titan's dune propagation occurs eastward under these conditions. Finally, this scenario combining global circulation winds and methane storms can explain other major features of Titan's dunes as the divergence from the equator or the dune size and spacing. It also implies an equatorial origin of Titan's dune sand and a possible occurence of dust storms.

  10. Evaluation of a convective downburst prediction application for India

    Pryor, Kenneth L.; Johny, C. J.; Prasad, V. S.


    During the month of June 2015, the South Asian (or Southwest) monsoon advanced steadily from the southern to the northwestern states of India. The progression of the monsoon had an apparent effect on the relative strength of convective storm downbursts that occurred during June and July 2015. A convective downburst prediction algorithm, involving the Microburst Windspeed Potential Index (MWPI) and a satellite-derived three-band microburst risk product, and applied with meteorological geostationary satellite (KALPANA-1 VHRR and METEOSAT-7) and MODIS Aqua data, was evaluated and found to effectively indicate relative downburst intensity in both pre-monsoon and monsoon environments over various regions of India. The MWPI product, derived from T574L64 Global Forecast System (NGFS) model data, is being generated in real-time by National Center for Medium Range Weather Forecasting (NCMRWF), Ministry of Earth Sciences, India. The validation process entailed direct comparison of measured downburst-related wind gusts at airports and India Meteorological Department (IMD) observatories to adjacent MWPI values calculated from GFS and India NGFS model datasets. Favorable results include a statistically significant positive correlation between MWPI values and proximate measured downburst wind gusts with a confidence level near 100%. Case studies demonstrate the influence of the South Asian monsoon on convective storm environments and the response of the downburst prediction algorithm.

  11. Gravo-Aeroelastic Scaling for Extreme-Scale Wind Turbines

    Fingersh, Lee J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Loth, Eric [University of Virginia; Kaminski, Meghan [University of Virginia; Qin, Chao [University of Virginia; Griffith, D. Todd [Sandia National Laboratories


    A scaling methodology is described in the present paper for extreme-scale wind turbines (rated at 10 MW or more) that allow their sub-scale turbines to capture their key blade dynamics and aeroelastic deflections. For extreme-scale turbines, such deflections and dynamics can be substantial and are primarily driven by centrifugal, thrust and gravity forces as well as the net torque. Each of these are in turn a function of various wind conditions, including turbulence levels that cause shear, veer, and gust loads. The 13.2 MW rated SNL100-03 rotor design, having a blade length of 100-meters, is herein scaled to the CART3 wind turbine at NREL using 25% geometric scaling and blade mass and wind speed scaled by gravo-aeroelastic constraints. In order to mimic the ultralight structure on the advanced concept extreme-scale design the scaling results indicate that the gravo-aeroelastically scaled blades for the CART3 are be three times lighter and 25% longer than the current CART3 blades. A benefit of this scaling approach is that the scaled wind speeds needed for testing are reduced (in this case by a factor of two), allowing testing under extreme gust conditions to be much more easily achieved. Most importantly, this scaling approach can investigate extreme-scale concepts including dynamic behaviors and aeroelastic deflections (including flutter) at an extremely small fraction of the full-scale cost.

  12. Aerodynamic forces acting on a passive flow control equipped airfoil in turbulent inflow conditions

    Kampers, Gerrit; Peinke, Joachim; Hölling, Michael


    Wind turbines work within turbulent atmospheric flows, with their well known challenging features of intermittent two point statistics. These intermittent statistics have a big impact on wind turbines, concerning fluctuating mechanical loads. Flow control is a promising approach for the reduction of these fluctuations. In this project, an airfoil profile is equipped with mechanically coupled flexible leading and trailing edge flaps, enabling to passively adapt its camber. We expose the profile to different reproducible turbulent inflow conditions, generated with an active grid in a wind tunnel and study the profile's ability to alleviate lift fluctuations. The first experiment is concerned with repeated mexican hat shaped inflow gusts. The corresponding lift reactions of the profile show, that the adaptive camber mechanism is able to alleviate lift fluctuations caused by the inflow gust. In the second experiment, we use different grid excitations to vary the flatness of the inflow angle increments and study the influence of the statistics at different angles of attack. We propose a stochastic Langevin approach to decompose the lift dynamics into a deterministic response and a stochastic part, allowing for a quantitative analysis of the response dynamics. Funded by the German Research Foundation, Ref. No. PE 478/15-1.

  13. Measured Noise from Small Unmanned Aerial Vehicles

    Cabell, Randolph; McSwain, Robert; Grosveld, Ferdinand


    Proposed uses of small unmanned aerial vehicles (UAVs), including home package delivery, have the potential to expose large portions of communities to a new noise source. This paper discusses results of flyover noise measurements of four small UAVs, including an internal combustion-powered model airplane and three battery-powered multicopters. Basic noise characteristics of these vehicles are discussed, including spectral properties and sound level metrics such as sound pressure level, effective perceived noise level, and sound exposure level. The size and aerodynamic characteristics of the multicopters in particular make their flight path susceptible to atmospheric disturbances such as wind gusts. These gusts, coupled with a flight control system that varies rotor speed to maintain vehicle stability, create an unsteady acoustic signature. The spectral variations resulting from this unsteadiness are explored, in both hover and flyover conditions for the multicopters. The time varying noise, which differs from the relatively steady noise generated by large transport aircraft, may complicate the prediction of human annoyance using conventional sound level metrics.

  14. Explosive development of winter storm Xynthia over the subtropical North Atlantic Ocean

    M. L. R. Liberato


    Full Text Available In winter of 2009–2010 south-western Europe was hit by several destructive windstorms. The most important was Xynthia (26–28 February 2010, which caused 64 reported casualties and was classified as the 2nd most expensive natural hazard event for 2010 in terms of economic losses. In this work we assess the synoptic evolution, dynamical characteristics and the main impacts of storm Xynthia, whose genesis, development and path were very uncommon. Wind speed gusts observed at more than 500 stations across Europe are evaluated as well as the wind gust field obtained with a regional climate model simulation for the entire North Atlantic and European area. Storm Xynthia was first identified on 25 February around 30° N, 50° W over the subtropical North Atlantic Ocean. Its genesis occurred on a region characterized by warm and moist air under the influence of a strong upper level wave embedded in the westerlies. Xynthia followed an unusual SW–NE path towards Iberia, France and central Europe. The role of moist air masses on the explosive development of Xynthia is analysed by considering the evaporative sources. A lagrangian model is used to identify the moisture sources, sinks and moisture transport associated with the cyclone during its development phase. The main supply of moisture is located over an elongated region of the subtropical North Atlantic Ocean with anomalously high SST, confirming that the explosive development of storm Xynthia had a significant contribution from the subtropics.

  15. ¿Qué es la terapia de contexto?.

    Mara Selvini Palazzoli


    Full Text Available Uno de los más grandes, o tal vez el más gran estudioso contemporáneo del comportamiento humano, Gregory BATESON, en la introducción a su libro Steps to an Ecology of Mind (Pasos hacia una ecología de la mente, nos cuenta de sus esfuerzos para introducir a sus alumnos, jóvenes psiquiatras, a enfrentar los problemas del comportamiento humano de un modo diferente al tradicional. Para este fin había escogido un método didáctico particular, muy similar al método socrático. Les daba preguntas, aparentemente bizarras y observaba de qué manera los estudiantes buscaban la solución. Una de tales preguntas, que resultó la más estimulante, era la siguiente: «Una madre tiene el hábito de premiar a su hijo con un helado si él es capaz de comerse toda la espinaca. ¿Qué información ulterior necesitarán ustedes para poder predecir: si el niño terminará gustándole u odiando las espinacas, si el niño terminará gustándole u odiando el helado o si el niño terminará amando u odiando a su madre]».

  16. 舰载机弹射起飞上升段控制律研究%Control Law for Climbing Stage of Carrier-Based Aircraft in Catapult-Assisted Take-Off

    朱熠; 江驹; 甄子洋; 王新华; 焦鑫


    针对舰载机的安全弹射起飞要求,研究了弹射起飞上升段控制律设计问题.分析了常用弹射装置原理以及弹射起飞的工作流程.构建了弹射起飞过程中的上升段相关数学模型,包括某型舰载机的纵向模型、前起落架突伸结构和阵风模型.设计了舰载机起飞离舰后上升段的飞行姿态控制律,在仿真中将加速滑跑阶段的各种因素转化成初始条件,同时分析了阵风干扰对上升段飞机飞行特性的影响.仿真结果表明:设计的姿态控制律可以改善舰载机在离舰上升段的姿态,抵抗气流干扰等因素的影响,提高弹射起飞的安全性.%According to the safety requirements of catapult-assisted take-off,the control law design for the aircraft in the climbing stage was studied. The principle of a common catapult device was studied and the process of catapult-assisted take-off was introduced. The mathematic models in the climbing stage were established, including the model of longitudinal small perturbation equations of the aircraft, the sudden stretch structure of the nose gear and the gust disturbance. The attitude control law of the climbing stage was designed. In simulation, the initial value was based on the influence of different factors in speeding stage. The influence of the gust disturbance on flight performance of the aircraft in its climbing stage was also analyzed. The results of simulation showed that the designed control law can improve the aircraft attitude in the climbing stage, decrease the adverse effect of gust disturbance, and thus can enhance the security of the catapult-assisted take-off.

  17. Multi-Objective Flight Control for Drag Minimization and Load Alleviation of High-Aspect Ratio Flexible Wing Aircraft

    Nguyen, Nhan; Ting, Eric; Chaparro, Daniel; Drew, Michael; Swei, Sean


    As aircraft wings become much more flexible due to the use of light-weight composites material, adverse aerodynamics at off-design performance can result from changes in wing shapes due to aeroelastic deflections. Increased drag, hence increased fuel burn, is a potential consequence. Without means for aeroelastic compensation, the benefit of weight reduction from the use of light-weight material could be offset by less optimal aerodynamic performance at off-design flight conditions. Performance Adaptive Aeroelastic Wing (PAAW) technology can potentially address these technical challenges for future flexible wing transports. PAAW technology leverages multi-disciplinary solutions to maximize the aerodynamic performance payoff of future adaptive wing design, while addressing simultaneously operational constraints that can prevent the optimal aerodynamic performance from being realized. These operational constraints include reduced flutter margins, increased airframe responses to gust and maneuver loads, pilot handling qualities, and ride qualities. All of these constraints while seeking the optimal aerodynamic performance present themselves as a multi-objective flight control problem. The paper presents a multi-objective flight control approach based on a drag-cognizant optimal control method. A concept of virtual control, which was previously introduced, is implemented to address the pair-wise flap motion constraints imposed by the elastomer material. This method is shown to be able to satisfy the constraints. Real-time drag minimization control is considered to be an important consideration for PAAW technology. Drag minimization control has many technical challenges such as sensing and control. An initial outline of a real-time drag minimization control has already been developed and will be further investigated in the future. A simulation study of a multi-objective flight control for a flight path angle command with aeroelastic mode suppression and drag

  18. Modelling derecho dynamics and the direct radiative effect of wildfire smoke upon it with NWP model HARMONIE

    Toll, Velle; Männik, Aarne


    Convection permitting numerical weather prediction model HARMONIE was used to simulate the dynamics of the derecho that swept over Eastern Europe on August 8, 2010. The storm moved over Belarus, Lithuania, Latvia, Estonia and Finland and the strongest wind gusts (up to 36.5 m/s) were measured in Estonia. The storm path is recorded on the radar images where characteristic bow echo was observed. The model setup was similar to near-future operational, nearly kilometre-scale environments in European national weather services. Hindcast experiments show the ability of the HARMONIE model to predict the severe convective storm and forecast concurrent strong wind gusts. Wind gusts with very similar intensity to observed ones were simulated by the HARMONIE model and 2.5-km horizontal resolution appears sufficient for reliable forecast of the derecho event. The timing of the modelled storm was in good agreement with the observations. The simulated average storm propagation speed was 25 m/s, similar to the radar observations. Hindcast experiments suggest that more precise warning for the storm could have been issued if the HARMONIE model would have been utilised. The derecho event was accompanied by the remarkable smoke aerosol concentrations (maximum total aerosol optical depth more than 4 at 550 nm) originating from the wildfires from Russia. Smoke plume travelled clockwise around Moscow from August 5 to 9. On August 8, 2010, smoke plume was situated on the Eastern border of Estonia. The derecho occurred on the western side of the smoke plume path. HARMONIE experiments were performed to study the direct radiative effect of wildfire smoke on a severe convective storm. The impact of smoke aerosol on the derecho dynamics was investigated. Reduction in the shortwave radiation flux at the surface resulting from aerosol influence simulated by the HARMONIE model is up to 200 W/m2 in the area with the highest aerosol concentrations. This causes near surface cooling of up to 3 º

  19. Development and flight test of a multi-function controller for automated cruise flaps on an aircraft wing

    Cox, Craig Allen

    Cruise flaps are trailing-edge flaps which minimize the profile drag of a wing by moving the low-drag-region (or bucket) of a drag polar such that it spans the current coefficient of lift. Previous research has explored the use of a pressure-based technique for automating cruise flaps. Data obtained using this technique can be presented in a number of different formats, and different presentations of the same data tend to lead to the development of different types of automating controllers. The presentation used by previous researchers led to the development of a drag-minimizing controller that required a low-pass filter to prevent instability. This prevented the controller from being used for purposes which required a fast-acting flap. The presentation of pressure data used in this research led to the development of a multi-function controller that includes both slow-acting functionality (drag reduction) and fast-acting functionality (gust alleviation). The pressure-based technique developed by previous researchers using natural-laminar-flow (NLF) airfoils must be modified somewhat for the low Reynolds number SD7037 airfoil used in this research. Drag polars for low Reynolds number airfoils do not behave as predictably as those for NLF airfoils at much higher Reynolds numbers. A series of rigid-aircraft simulations were conducted to show the effectiveness of the multi-function controller, which was able to simultaneously reduce drag and alleviate the effects of vertical gusts. A flight controller was developed using low-cost microcontrollers and pressure transducers. The controller implemented a slow-acting drag-reduction function and a fast-acting function to handle pilot-commanded elevator inputs. Gust alleviation was not implemented due to limitations of the available hardware and flight test conditions. The controller was tested on an radio-controlled sailplane with a wingspan of 100 inches. Although direct measurement of the drag of an aircraft this size is

  20. Sensing of fatty acids for octanoylation of ghrelin involves a gustatory G-protein.

    Sara Janssen

    Full Text Available BACKGROUND: Ghrelin is an important regulator of energy--and glucose homeostasis. The octanoylation at Ser(3 is essential for ghrelin's biological effects but the mechanisms involved in the octanoylation are unknown. We investigated whether the gustatory G-protein, α-gustducin, and the free fatty acid receptors GPR40 and GPR120 are involved in the fatty acid sensing mechanisms of the ghrelin cell. METHODS: Wild-type (WT and α-gustducin knockout (gust(-/- mice were fed a glyceryl trioctanoate-enriched diet (OD during 2 weeks. Ghrelin levels and gastric emptying were determined. Co-localization between GPR40, GPR120 and ghrelin or α-gustducin/α-transducin was investigated by immunofluorescence staining. The role of GPR120 in the effect of medium and long chain fatty acids on the release of ghrelin was studied in the ghrelinoma cell line, MGN3-1. The effect of the GPR40 agonist, MEDICA16, and the GPR120 agonist, grifolic acid, on ghrelin release was studied both in vitro and in vivo. RESULTS: Feeding an OD specifically increased octanoyl ghrelin levels in the stomach of WT mice but not of gust(-/- mice. Gastric emptying was accelerated in WT but not in gust(-/- mice. GPR40 was colocalized with desoctanoyl but not with octanoyl ghrelin, α-gustducin or α-transducin positive cells in the stomach. GPR120 only colocalized with ghrelin in the duodenum. Addition of octanoic acid or α-linolenic acid to MGN3-1 cells increased and decreased octanoyl ghrelin levels, respectively. Both effects could not be blocked by GPR120 siRNA. MEDICA16 and grifolic acid did not affect ghrelin secretion in vitro but oral administration of grifolic acid increased plasma ghrelin levels. CONCLUSION: This study provides the first evidence that α-gustducin is involved in the octanoylation of ghrelin and shows that the ghrelin cell can sense long- and medium-chain fatty acids directly. GPR120 but not GPR40 may play a role in the lipid sensing cascade of the ghrelin cell.

  1. On the determination of the neutral drag coefficient in the convective boundary layer

    Grachev, A.A.; Fairall, C.W.; Larsen, Søren Ejling


    Based on the idea that free convection can be considered as a particular case of forced convection, where the gusts driven by the large-scale eddies are scaled with the Deardorff convective velocity scale, a new formulation for the neutral drag coefficient, C-Dn, in the convective boundary layer ...... for mean wind speed less than about 2 m s(-1). The new approach also clarifies several contradictory results from earlier works. Some aspects related to an alternate definition of the neutral drag coefficient and the wind speed and the stress averaging procedure are considered.......) the stratification Psi function used in the derivation of C-Dn should satisfy the theoretical free-convection limit. The new formulation is compared with the traditional relationship for C-Dn, and data collected over the sea (during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment...

  2. Data Mining of NASA Boeing 737 Flight Data: Frequency Analysis of In-Flight Recorded Data

    Butterfield, Ansel J.


    Data recorded during flights of the NASA Trailblazer Boeing 737 have been analyzed to ascertain the presence of aircraft structural responses from various excitations such as the engine, aerodynamic effects, wind gusts, and control system operations. The NASA Trailblazer Boeing 737 was chosen as a focus of the study because of a large quantity of its flight data records. The goal of this study was to determine if any aircraft structural characteristics could be identified from flight data collected for measuring non-structural phenomena. A number of such data were examined for spatial and frequency correlation as a means of discovering hidden knowledge of the dynamic behavior of the aircraft. Data recorded from on-board dynamic sensors over a range of flight conditions showed consistently appearing frequencies. Those frequencies were attributed to aircraft structural vibrations.

  3. Influence of wind on aerodynamic drag for the second case of the arrangement of the equipment on the LE 060EA locomotive bodywork

    Sorin ARSENE


    Full Text Available The electric power supply equipment of electric railways vehicles of surface is placed on the their body. The arrangement of the equipment on the vehicle body determines the variation of the aerodynamic drag. The gusts of wind occurring during the vehicle movement result in additional requests. The case of the locomotive of type LE 060 EA 5100kW moving with the second driving position is analyzed in this paper. For this particular case the components ensemble of the power supply system was geometric modelled in 3D format at 1:1 scale. The resulted model was placed in air flow simulation software to determine the aerodynamic resistance. The wind influence is analyzed for five point values of its speed. The wind direction is simulated by eight point values of the angle that it makes to the longitudinal axis of the vehicle.

  4. Unsteady flow past wings having sharp-edge separation

    Atta, E. H.; Kandil, O. A.; Mook, D. T.; Nayfeh, A. H.


    A vortex-lattice technique is developed to model unsteady, incompressible flow past thin wings. This technique predicts the shape of the wake as a function of time; thus, it is not restricted by planform, aspect ratio, or angle of attack as long as vortex bursting does not occur and the flow does not separate from the wing surface. Moreover, the technique can be applied to wings of arbitrary curvature undergoing general motion; thus, it can treat rigid-body motion, arbitrary wing deformation, gusts in the freestream, and periodic motions. Numerical results are presented for low-aspect rectangular wings undergoing a constant-rate, rigid-body rotation about the trailing edge. The results for the unsteady motion are compared with those predicted by assuming quasi-steady motion. The present results exhibit hysteretic behavior.

  5. A LIDAR-assisted model predictive controller added on a traditional wind turbine controller

    Mirzaei, Mahmood; Hansen, Morten Hartvig


    control and opens the market of retrofitting existing wind turbines with the new technology. In this paper, we suggest a model predictive controller (MPC) that is added to the basic gain scheduled PI controller of a WT to enhance the performance of the closed loop system using LIDAR measurements......LIDAR-assisted collective pitch control shows promising results for load reduction in the full load operating region of horizontal axis wind turbines (WT). Utilizing LIDARs in WT control can be approached in different ways; One method is to design the WT controller from ground up based on the LIDAR...... scenarios include the extreme operating gust and normal power production using stochastic wind field in the full load region. The results show superior performance compared to the PI controller and a performance marginally better compared to the FF+PI controller. The reason for a better performance against...

  6. Optic flow based station-keeping and wind rejection for small flying vehicles

    Patrick, Bryan

    Optic flow and Wide Field Integration (WFI) have shown potential for application to autonomous navigation of Unmanned Air Vehicles (UAVs). In this study the application of these same methods to other tasks, namely station-keeping and wind rejection, is examined. Theory surrounding optic flow, WFI and wind gust modeling is examined to provide a theoretical background. A controller based on a Hinfinity bounded formulation of the well known Linear Quadratic Regulator in designed to both mitigate wind disturbances and station-keep. The performance of this controller is assessed via simulation to determine both performance and trade-offs in implementation such as the method for optic flow calculation. Furthermore, flight tests are performed to examine the real world effectiveness of the controller. Finally, conclusions about potential improvement to implementation are drawn

  7. Sliding mode tracking control for miniature unmanned helicopters

    Bin Xian


    Full Text Available A sliding mode control design for a miniature unmanned helicopter is presented. The control objective is to let the helicopter track some predefined velocity and yaw trajectories. A new sliding mode control design method is developed based on a linearized dynamic model. In order to facilitate the control design, the helicopter’s dynamic model is divided into two subsystems, such as the longitudinal-lateral and the heading-heave subsystem. The proposed controller employs sliding mode control technique to compensate for the immeasurable flapping angles’ dynamic effects and external disturbances. The global asymptotic stability (GAS of the closed-loop system is proved by the Lyapunov based stability analysis. Numerical simulations demonstrate that the proposed controller can achieve superior tracking performance compared with the proportional-integral-derivative (PID and linear-quadratic regulator (LQR cascaded controller in the presence of wind gust disturbances.

  8. Sliding mode tracking control for miniature unmanned helicopters

    Xian Bin; Guo Jianchuan; Zhang Yao; Zhao Bo


    A sliding mode control design for a miniature unmanned helicopter is presented. The control objective is to let the helicopter track some predefined velocity and yaw trajectories. A new sliding mode control design method is developed based on a linearized dynamic model. In order to facilitate the control design, the helicopter’s dynamic model is divided into two subsystems, such as the longitudinal-lateral and the heading-heave subsystem. The proposed controller employs sliding mode control technique to compensate for the immeasurable flapping angles’ dynamic effects and external disturbances. The global asymptotic stability (GAS) of the closed-loop system is proved by the Lyapunov based stability analysis. Numerical simulations demonstrate that the proposed controller can achieve superior tracking performance compared with the proportional-integral-derivative (PID) and linear-quadratic regulator (LQR) cascaded controller in the presence of wind gust disturbances.

  9. Fault Tolerant Flight Control Using Sliding Modes and Subspace Identification-Based Predictive Control

    Siddiqui, Bilal A.


    In this work, a cascade structure of a time-scale separated integral sliding mode and model predictive control is proposed as a viable alternative for fault-tolerant control. A multi-variable sliding mode control law is designed as the inner loop of the flight control system. Subspace identification is carried out on the aircraft in closed loop. The identified plant is then used for model predictive controllers in the outer loop. The overall control law demonstrates improved robustness to measurement noise, modeling uncertainties, multiple faults and severe wind turbulence and gusts. In addition, the flight control system employs filters and dead-zone nonlinear elements to reduce chattering and improve handling quality. Simulation results demonstrate the efficiency of the proposed controller using conventional fighter aircraft without control redundancy.

  10. Downbursts and microbursts - An aviation hazard. [downdrafts beneath thunderstorms

    Fujita, T. T.


    Downburst and microburst phenomena occurring since 1975 are studied, based on meteorological analyses of aircraft accidents, aerial surveys of wind effects left behind downbursts, and studies of sub-mesoscale wind systems. It is concluded that microbursts beneath small, air mass thunderstorms are unpredictable in terms of weather forecast. Most aircraft incidents, however, were found to have occurred in the summer months, June through August. An intense microburst could produce 150 mph horizontal winds as well as 60 fps downflows at the tree-top level. The largest contributing factor to aircraft difficulties seemed to be a combination of the headwind decrease and the downflow. Anemometers and/or pressure sensors placed near runways were found effective for detecting gust fronts, but not for detecting downbursts. It is recommended that new detection systems placed on the ground or airborne, be developed, and that pilots be trained for simulated landing and go-around through microbursts.

  11. Flutter and Forced Response Analyses of Cascades using a Two-Dimensional Linearized Euler Solver

    Reddy, T. S. R.; Srivastava, R.; Mehmed, O.


    Flutter and forced response analyses for a cascade of blades in subsonic and transonic flow is presented. The structural model for each blade is a typical section with bending and torsion degrees of freedom. The unsteady aerodynamic forces due to bending and torsion motions. and due to a vortical gust disturbance are obtained by solving unsteady linearized Euler equations. The unsteady linearized equations are obtained by linearizing the unsteady nonlinear equations about the steady flow. The predicted unsteady aerodynamic forces include the effect of steady aerodynamic loading due to airfoil shape, thickness and angle of attack. The aeroelastic equations are solved in the frequency domain by coupling the un- steady aerodynamic forces to the aeroelastic solver MISER. The present unsteady aerodynamic solver showed good correlation with published results for both flutter and forced response predictions. Further improvements are required to use the unsteady aerodynamic solver in a design cycle.

  12. The genus Rubus (Rosaceae in South Africa. IV. Natural hybridiza­ tion

    J. J. Spies


    Full Text Available The genus  Rubus L. is represented in southern Africa by the subgenera  Eubatus Focke and  Idaeobatus Focke. A combination o f morphological data, data on the reproductive systems of some collections and meiotic chromosome behaviour indicates that a hybrid swarm in the eastern Transvaal was formed subsequent to the hybridization between R. cuneifolius Pursh. taxon B (subgenus Eubatus and R. longepedicellatus (C. E. Gust. C. H. Stirton (subgenus Idaeobatus. Other examples of intra- and intersubgeneric hybridization were found during this study of the South African material. These instances, with examples found in the literature, indicate that the subgeneric subdivisions of Rubus are artificial. Three different methods were used to analyse the meiotic chromosome configurations. The genome relationship system of Alonso & Kimber (1981 and Kimber & Alonso (1981 and the modification of the binomial system of Jackson & Casey (1980 by Spies (1984 proved to be the most sensitive for distinguishing between alio-, segmental alio- and autoploids.

  13. Simulation of Heavy Lift Airship dynamics over large ranges of incidence and speed

    Tischler, M. B.; Jex, H. R.; Ringland, R. F.


    A nonlinear, multibody, six-degrees-of-freedom digital simulation has been developed to study generic Heavy Lift Airship (HLA) dynamics and control. The basic aerodynamic functions developed to model the hull, tail, and rotor loads continuously over all incidence ranges are reviewed and applied to a Quadrotor HLA with a low fineness ratio hull and a small vee-tail. Trim calculations for a test vehicle suggest control power deficiencies in crosswind stationkeeping for the unloaded vehicle. Gust responses show the importance of correctly calculating loads due to accelerated relative motion of air and hull. Numerically linearized dynamics for the test vehicle show the existence of a divergent yaw mode, and an oscillatory pitch mode whose stability characteristics are sensitive to flight speed. A considerable improvement in the vehicle's stability and response results from a simple multi-axis closed-loop control system operating on the rotors and propeller blades.

  14. Determinació analítica de 2,4,6-ticloroanisole i altres cloroanisoles en vins i suros

    Riu Rusell, Marc


    La determinació de 2,4,6-tricloroanisole (TCA) i altres cloroanisoles en vins i taps de suro és de vital importància, tant en la industria enològica com en al surera, pel control d’un dels defectes organolèptics del vi que ha causat més prejudicis: l’olor a humitat, clàssicament conegut com a gust a suro. En aquesta tesi doctoral s’han desenvolupat i validat aquestes metodologies, tot aplicant la microextracció en fase sòlida i la cromatografia de gasos, ja sigui en detecció de captura electr...

  15. Pacific Northwest Storms Situation Report # 7



    Despite a small storm that came through the area last night with wind gusts peaking at 45 MPH, progress continues to be made in restoring power to customers who lost power during the December 14-15 storms which hit the Pacific Northwest region. Currently, 95,971 customers remain without power, down from 1.8 million customers. The wind storm which affected the area yesterday was not as bad as previously expected, with the majority of the customer outages in the BC Hydro region, and 3,000 additional customer outages in the Puget Sound Energy service area. The customers without power represent 5 percent of customers in the affected utility service areas of Washington. The majority of customers without power are served by Puget Sound Energy, BC Hydro, and Seattle City Light.

  16. Pacific Northwest Storms Situation Report # 1



    Severe wind and snow storms hit the Pacific Northwest region on December 14 – 15, 2006, following severe flooding during the past few days. The severe weather resulted in major power outages through the region. At peak there were 1.8 million customers without power which included BC Hydro in Canada. Currently, there are over 1.5 million outages in the region as a result of the Pacific Northwest Storms. This represents about 42 percent of customers in affected utility service areas in Oregon and Washington. See table below. Because the current wind and snow storms are coming on the heels of extensive flooding in the region, electric utilities are experiencing damage. Wind gusts reached close to 100 mph in some areas of the region. The storm is expected to bring its strong winds and heavy snow into Idaho, Montana and Wyoming Friday and into the weekend. There are currently no reported major impacts to the petroleum and natural gas infrastructure.

  17. Distribution of background equivalent static wind load on high-rise buildings

    Jianguo ZHANG; Ming GU


    In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel.Some typical methods proposed in some relative litera-tures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods,are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use.

  18. Turbulent Extreme Event Simulations for Lidar-Assisted Wind Turbine Control

    Schlipf, David; Raach, Steffen


    This work presents a wind field generator which allows to shape wind fields in the time domain while maintaining the spectral properties. This is done by an iterative generation of wind fields and by minimizing the error between wind characteristics of the generated wind fields and desired values. The method leads towards realistic ultimate load calculations for lidar-assisted control. This is demonstrated by fitting a turbulent wind field to an Extreme Operating Gust. The wind field is then used to compare a baseline feedback controller alone against a combined feedback and feedforward controller using simulated lidar measurements. The comparison confirms that the lidar-assisted controller is still able to significantly reduce the ultimate loads on the tower base under this more realistic conditions.

  19. Gusty, gaseous flows of FIRE: galactic winds in cosmological simulations with explicit stellar feedback

    Muratov, Alexander L; Faucher-Giguere, Claude-Andre; Hopkins, Philip F; Quataert, Eliot; Murray, Norman


    We present an analysis of the galaxy-scale gaseous outflows from the FIRE (Feedback in Realistic Environments) simulations. This suite of hydrodynamic cosmological zoom simulations provides a sample of halos where star-forming giant molecular clouds are resolved to z=0, and features an explicit stellar feedback model on small scales. In this work, we focus on quantifying the gas mass ejected out of galaxies in winds and how this material travels through the halo. We correlate these quantities to star formation in galaxies throughout cosmic history. Our simulations reveal that a significant portion of every galaxy's evolution, particularly at high redshift, is dominated by bursts of star formation, which are followed by powerful gusts of galactic outflow that sweep up a large fraction of gas in the interstellar medium and send it through the circumgalactic medium. The dynamical effect of these outflows can significantly limit the amount of star formation within the affected galaxy. At low redshift, however, su...

  20. Wind Power Meteorology

    Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

    : wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed......Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed...

  1. Field Measurement of Wind Speeds and Wind-Induced Responses atop the Shanghai World Financial Center under Normal Climate Conditions

    Yong Quan


    Full Text Available Field measurement data on wind velocities and wind-induced acceleration responses at the top of the 492 m high Shanghai World Financial Center (SWFC under normal climate conditions are studied. Characteristics of the mean wind speeds and turbulence intensities, gust factors, power spectral densities, and turbulence integral scales of the fluctuating wind speed are analyzed in different observation time intervals. Power spectral densities of wind-induced acceleration are also investigated. The basic natural frequencies and structural damping ratios of the building are identified based on Hilbert-Huang transform method and random decrement method. The field measurement results of wind-induced responses of the SWFC are finally compared with those from the corresponding high-frequency force balance wind tunnel test study.

  2. Single velocity-component modeling of leading edge turbulence interaction noise.

    Gill, J; Zhang, X; Joseph, P


    A computational aeroacoustics approach is used to predict leading edge turbulence interaction noise for real airfoils. One-component (transverse), two-component (transverse and streamwise), and three-component (transverse, streamwise, and spanwise) synthesized turbulence disturbances are modeled instead of harmonic transverse gusts, to which previous computational studies of leading edge noise have often been confined. The effects of the inclusion of streamwise and spanwise disturbances on the noise are assessed. It is shown that accurate noise predictions can be made by modeling only transverse disturbances which reduces the computational expense of simulations. The accuracy of using only transverse disturbances is assessed for symmetric and cambered airfoils, and also for airfoils at non-zero angle of attack.

  3. Multivariate max-stable spatial processes

    Genton, Marc G.


    Max-stable processes allow the spatial dependence of extremes to be modelled and quantified, so they are widely adopted in applications. For a better understanding of extremes, it may be useful to study several variables simultaneously. To this end, we study the maxima of independent replicates of multivariate processes, both in the Gaussian and Student-t cases. We define a Poisson process construction and introduce multivariate versions of the Smith Gaussian extreme-value, the Schlather extremal-Gaussian and extremal-t, and the Brown–Resnick models. We develop inference for the models based on composite likelihoods. We present results of Monte Carlo simulations and an application to daily maximum wind speed and wind gust.

  4. Assessment of Gearbox Operational Loads and Reliability under High Mean Wind Speeds

    Dabrowski, Dariusz; Natarajan, Anand


    wind turbine that operates in storm conditions with mean wind speeds less than 30 m/s is presented. In the study, normal shut-downs of a wind turbine in storm conditions were investigated. The analysis were conducted for two storm control strategies and different wind conditions from an extreme...... of the model was based on the experimental data provided by NREL for 750 kW prototype gearbox. Failures of gearboxes caused by high dynamic loads have a significant influence on the cost of operation of wind farms. For these reasons in the study, the probability of failure of the gearbox working in an offshore...... operating gust, normal turbulence model and extreme turbulence model. In the paper, loads in the planetary gear are quantified as well as the torsional moments in the main shaft. On the basis of simulation results the annual probability of failure of the gearbox in a wind turbine with soft storm controller...

  5. DOE SBIR Phase II Final Technical Report - Assessing Climate Change Effects on Wind Energy

    Whiteman, Cameron [Vertum Partners LP, Los Angeles, CA (United States); Capps, Scott [Vertum Partners LP, Los Angeles, CA (United States)


    Specialized Vertum Partners software tools were prototyped, tested and commercialized to allow wind energy stakeholders to assess the uncertainties of climate change on wind power production and distribution. This project resulted in three commercially proven products and a marketing tool. The first was a Weather Research and Forecasting Model (WRF) based resource evaluation system. The second was a web-based service providing global 10m wind data from multiple sources to wind industry subscription customers. The third product addressed the needs of our utility clients looking at climate change effects on electricity distribution. For this we collaborated on the Santa Ana Wildfire Threat Index (SAWTi), which was released publicly last quarter. Finally to promote these products and educate potential users we released “Gust or Bust”, a graphic-novel styled marketing publication.

  6. Attitude Control for an Aero-Vehicle Using Vector Thrusting and Variable Speed Control Moment Gyros

    Shin, Jong-Yeob; Lim, K. B.; Moerder, D. D.


    Stabilization of passively unstable thrust-levitated vehicles can require significant control inputs. Although thrust vectoring is a straightforward choice for realizing these inputs, this may lead to difficulties discussed in the paper. This paper examines supplementing thrust vectoring with Variable-Speed Control Moment Gyroscopes (VSCMGs). The paper describes how to allocate VSCMGs and the vectored thrust mechanism for attitude stabilization in frequency domain and also shows trade-off between vectored thrust and VSCMGs. Using an H2 control synthesis methodology in LMI optimization, a feedback control law is designed for a thrust-levitated research vehicle and is simulated with the full nonlinear model. It is demonstrated that VSCMGs can reduce the use of vectored thrust variation for stabilizing the hovering platform in the presence of strong wind gusts.

  7. Dynamic survey of wind turbine vibrations

    Chiang, Chih-Hung; Hsu, Keng-Tsang; Cheng, Chia-Chi; Pan, Chieh-Chen; Huang, Chi-Luen; Cheng, Tao-Ming


    Six wind turbines were blown to the ground by the wind gust during the attack of Typhoon Soudelor in August 2015. Survey using unmanned aerial vehicle, UAV, found the collapsed wind turbines had been broken at the lower section of the supporting towers. The dynamic behavior of wind turbine systems is thus in need of attention. The vibration of rotor blades and supporting towers of two wind turbine systems have been measured remotely using IBIS, a microwave interferometer. However the frequency of the rotor blade can be analyzed only if the microwave measurements are taken as the wind turbine is parked and secured. Time-frequency analyses such as continuous wavelet transform and reassigned spectrograms are applied to the displacement signals obtained. A frequency of 0.44Hz exists in both turbines B and C at various operating conditions. Possible links between dynamic characteristics and structural integrity of wind turbine -tower systems is discussed.

  8. Civil helicopter flight research. [for CH-53 helicopter

    Snyder, W. J.; Schoultz, M. B.


    The paper presents a description of the NASA CH-53 Civil Helicopter Research Aircraft and discusses preliminary results of the aircraft flight research performed to evaluate factors and requirements for future helicopter transport operations. The CH-53 equipped with a 16-seat airline-type cabin and instrumented for flight research studies in noise, vibration, handling qualities, passenger acceptance, fuel utilization, terminal area maneuvers, and gust response. Predicted fuel usage for typical short-haul missions is compared with actual fuel use. Pilot ratings for an IFR handling quality task for three levels of stability augmentation are presented, and the effects of internal noise, vibration, and motion on passenger acceptance are discussed. Future planned CH-53 flight research within the Civil Helicopter Technology Program is discussed.

  9. Wallada Bint al Mustakfi entre dos culturas

    shreen Mahmoud Al Refai


    La princesa cordobesa Wallada Bint al Mustakfi bil-lah, hija del califa al Mustakfi Muhammad Ibn Abdel Rahman Ibn Obaidil-lah Ibn Al Nasir lidin Al-lah era una poetisa estimable, a quien los grandes poetas no podían superar. Era una mujer única, guapa y decente. Mantenía una relación sentimental con el  poeta y visir Ibn Zaydún. Dicha pasión, narrada por los poemas escritos por ambos amantes, se terminó por la separación debida a los celos, también de ambos;  al poeta le gustó la voz de una e...

  10. Wind Turbines: Unsteady Aerodynamics and Inflow Noise

    Broe, Brian Riget

    ; and Graham, J. M. R.: 1970, Lifting surface theory for the problem of an arbitrarily yawed sinusoidal gust incident on a thin aerofoil in incompressible flow). Two of these models are investigated to find the unsteady lift distribution or pressure difference as function of chordwise position on the aerofoil...... (Sears, W. R.: 1941; and Graham, J. M. R.: 1970). An acoustic model is investigated using a model for the lift distribution as input (Amiet, R. K.: 1975, Acoustic radiation from an airfoil in a turbulent stream). The two models for lift distribution are used in the acoustic model. One of the models...... and the perfectly isotropic turbulent model. This indicates that the models capture the aerodynamics well. Thus the measurements suggest that the noise due to atmospheric turbulence can be described and modeled by the two models for lift distribution. It was not possible to test the acoustical model...

  11. Ten-Year Climatology of Summertime Diurnal Rainfall Rate Over the Conterminous U.S.

    Matsui, Toshihisa; Mocko, David; Lee, Myong-In; Tao, Wei-Kuo; Suarez, Max J.; Pielke, Roger A., Sr.


    Diurnal cycles of summertime rainfall rates are examined over the conterminous United States, using radar-gauge assimilated hourly rainfall data. As in earlier studies, rainfall diurnal composites show a well-defined region of rainfall propagation over the Great Plains and an afternoon maximum area over the south and eastern portion of the United States. Zonal phase speeds of rainfall in three different small domains are estimated, and rainfall propagation speeds are compared with background zonal wind speeds. Unique rainfall propagation speeds in three different regions can be explained by the evolution of latent-heat theory linked to the convective available potential energy, than by gust-front induced or gravity wave propagation mechanisms.

  12. Long-term field measurement and analysis of the natural wind characteristics at the site of Xi-hou-men Bridge

    Ming LIU; Hai-li LIAO; Ming-shui LI; Cun-ming MA; Mei YU


    In order to investigate the wind characteristics of coastal areas of China,a long-term field measurement of natural wind was carried out.Based on the field measurement results,this paper presents the natural wind characteristics of typhoons and strong monsoons at the site of Xi-hou-men Bridge,including mean wind speed,mean wind direction,mean wind elevation angle,turbulent intensity,gust factor,turbulence integral length scales,power spectrum of wind speed and spatial correlation of gusty wind,the profiles of mean wind speed and turbulent intensity,etc.The correlation among wind characteristics is analyzed in detail,and the similarities and differences of wind characteristics between typhoons and monsoons are analyzed.These results can provide detailed wind characteristics of coastal areas of China.

  13. Effectiveness of basic display augmentation in vehicular control by visual field cues

    Grunwald, A. J.; Merhav, S. J.


    The paper investigates the effectiveness of different basic display augmentation concepts - fixed reticle, velocity vector, and predicted future vehicle path - for RPVs controlled by a vehicle-mounted TV camera. The task is lateral manual control of a low flying RPV along a straight reference line in the presence of random side gusts. The man-machine system and the visual interface are modeled as a linear time-invariant system. Minimization of a quadratic performance criterion is assumed to underlie the control strategy of a well-trained human operator. The solution for the optimal feedback matrix enables the explicit computation of the variances of lateral deviation and directional error of the vehicle and of the control force that are used as performance measures.

  14. Potential and site evaluation for a wind energy project on the Grimsel pass; Potential- und Standortabklaerungen fuer ein Windenergieprojekt auf dem Grimselpass

    Kapp, Ch.; Schwer, P.; Brenni, R.


    This final report for the Swiss Federal Office of Energy (SFOE) presents the results of an evaluation made concerning the suitability of the Grimsel pass in Switzerland for the installation of wind turbines. The report presents wind and climate measurements made on-site and those extrapolated from data collected at the Grimsel weather station. The accuracy of the data is discussed and long-term extrapolations are made. The analysis of the data, including turbulence analysis, and the methods used to estimate wind conditions at hub height are discussed. The method used to model the wind conditions is described and the results discussed. The report makes recommendations on the requirements that are to be placed on the wind converters with respect to turbulence, wind-gusts and icing-up as well as on the foundations and accessibility of the turbines.

  15. Subsonic Indicial Aerodynamics for Aerofoil's Unsteady Loads via Numerical and Analytical Methods

    Berci, Marco


    This study deals with generating aerodynamic indicial-admittance functions for predicting the unsteady lift of two-dimensional aerofoils in subsonic flow, using approximate numerical and analytical formulations. Both a step-change in the angle of attack and a sharp-edge gust are suitably considered as small perturbations. Novel contributions concern both a systematic analysis of the computational simulations process and an effective theoretical synthesis of its outcome, providing with sound cross-validation. Good practice for generating the indicial-admittance functions via computational fluid dynamics is first investigated for several Mach numbers, angles of attack and aerofoil profiles. Convenient analytical approximations of such indicial functions are then obtained by generalising those available for incompressible flow, taking advantage of acoustic wave theory for the non-circulatory airload and Prandtl-Glauert's scalability rule for the circulatory airload. An explicit parametric formula is newly propos...

  16. Analyses of possible changes in intense and extreme wind speeds over northern Europe under climate change scenarios

    Pryor, Sara; Barthelmie, Rebecca Jane; Clausen, Niels-Erik;


    21st. Even then, significant changes are indicated only in the SW of the domain and across the central Baltic Sea where there is some evidence for relatively small magnitude increases in the 50 year return period wind speed (of up to 15%). There are marked differences in results based on the two...... Regional Climate Models. Additionally, internal (inherent) variability and initial conditions exert a strong impact on projected wind climates throughout the twenty-first century. Simulations of wind gusts by one of the RCMs (RCA3) indicate some evidence for increased magnitudes (of up to +10......%) in the southwest of the domain and across the central Baltic Sea by the end of the current century. As in prior downscaling of ECHAM4, dynamical downscaling of ECHAM5 indicates a tendency towards increased energy density and thus wind power generation potential over the course of the C21st. However, caution should...

  17. Lightning jump as a nowcast predictor: Application to severe weather events in Catalonia

    Farnell, C.; Rigo, T.; Pineda, N.


    Several studies reported sudden increases in the total lightning flash rate (intra-cloud+cloud-to-ground) preceding the occurrence of severe weather (large hail, wind gusts associated to thunderstorms and/or tornadoes). Named ;Lightning Jump;, this pattern has demonstrated to be of operational applicability in the forecasting of severe weather phenomena. The present study introduces the application of a lightning jump algorithm, with an identification of cells based solely on total lightning data, revealing that there is no need of radar data to trigger severe weather warnings. The algorithm was validated by means of a dataset severe weather events occurred in Catalonia in the period 2009-2014. Results obtained revealed very promising.

  18. Simulation for Grid Connected Wind Turbines with Fluctuating

    Ye, Ying; Fu, Yang; Wei, Shurong

    This paper establishes the whole dynamic model of wind turbine generator system which contains the wind speed model and DFIG wind turbines model .A simulation sample based on the mathematical models is built by using MATLAB in this paper. Research are did on the performance characteristics of doubly-fed wind generators (DFIG) which connected to power grid with three-phase ground fault and the disturbance by gust and mixed wind. The capacity of the wind farm is 9MW which consists of doubly-fed wind generators (DFIG). Simulation results demonstrate that the three-phase ground fault occurs on grid side runs less affected on the stability of doubly-fed wind generators. However, as a power source, fluctuations of the wind speed will run a large impact on stability of double-fed wind generators. The results also show that if the two disturbances occur in the meantime, the situation will be very serious.

  19. Closing Symposium of the German Research Initiative ComFliTe

    Radespiel, Rolf; Burg, Jan; Sørensen, Kaare


    This book reports on the German research initiative ComFliTe (Computational Flight Testing), the main goal of which was to enhance the capabilities of and tools for numerical simulation in flight physics to support future aircraft design and development. The initiative was coordinated by the German Aerospace Center (DLR) and promoted collaboration between the aircraft industry and academia. Activities focused on improving physical modeling for separated flows, developing advanced numerical algorithms for series computations and sensitivity predictions, as well as surrogate and reduced order modeling for aero data production and developing robust fluid-, structure- and flight mechanics coupling procedures. Further topics included more efficient handling of aircraft control surfaces and improving simulation methods for maneuvers, such as gust encounter. The important results of this three-year initiative were presented during the ComFliTe closing symposium, which took place at the DLR in Braunschweig, Germany, ...

  20. Comprehensive study of endurance for IAR-99 Hawk



    Full Text Available The paper presents some methods of on-ground and in-flight calibration for strain gauges, intended to the development of complex programs which analyze the endurance phenomena for aerospace structures, with direct application to the IAR-99 Hawk. The strain gauges have the advantage of being sensitive to load and therefore to aerodynamic phenomena, thereby providing indications of the loads supported by the structure. The effects size of loads type phenomena caused by wind gusts or buffet can be measured only by strain gauges or accelerometres70 and they cannot be recorded by flight or fatigue parameters counters. The installation of a strain gauge is made using a pattern (its position and orientation are crucial and the strain gauge selected for installation should not be fragile or unstable. Routines should be established for periodic inspection of strain gauges and those which are defective should be replaced immediately.

  1. Time series analysis of wind speed using VAR and the generalized impulse response technique

    Ewing, Bradley T. [Area of Information Systems and Quantitative Sciences, Rawls College of Business and Wind Science and Engineering Research Center, Texas Tech University, Lubbock, TX 79409-2101 (United States); Kruse, Jamie Brown [Center for Natural Hazard Research, East Carolina University, Greenville, NC (United States); Schroeder, John L. [Department of Geosciences and Wind Science and Engineering Research Center, Texas Tech University, Lubbock, TX (United States); Smith, Douglas A. [Department of Civil Engineering and Wind Science and Engineering Research Center, Texas Tech University, Lubbock, TX (United States)


    This research examines the interdependence in time series wind speed data measured in the same location at four different heights. A multiple-equation system known as a vector autoregression is proposed for characterizing the time series dynamics of wind. Additionally, the recently developed method of generalized impulse response analysis provides insight into the cross-effects of the wind series and their responses to shocks. Findings are based on analysis of contemporaneous wind speed time histories taken at 13, 33, 70 and 160 ft above ground level with a sampling rate of 10 Hz. The results indicate that wind speeds measured at 70 ft was the most variable. Further, the turbulence persisted longer at the 70-ft measurement than at the other heights. The greatest interdependence is observed at 13 ft. Gusts at 160 ft led to the greatest persistence to an 'own' shock and led to greatest persistence in the responses of the other wind series. (author)

  2. Recent developments in microburst nowcasting using GOES

    Pryor, Kenneth L


    Recent testing and validation have found that the Geostationary Operational Environmental Satellite (GOES) microburst products are effective in the assessment and short-term forecasting of downburst potential and associated wind gust magnitude. Two products, the GOES sounder Microburst Windspeed Potential Index (MWPI) and a new two-channel GOES imager brightness temperature difference (BTD) product have demonstrated capability in downburst potential assessment. The MWPI, a diagnostic nowcasting product, is designed to infer attributes of a favorable microburst environment: large CAPE and a convective mixed layer with a steep temperature lapse rate and low relative humidity in the surface layer. These conditions foster intense convective downdrafts due to evaporational cooling as precipitation descends in the sub-cloud layer. More recently, a new application of the brightness temperature difference (BTD) between GOES imager channels 3 and 4 has been developed. It has been found that the BTD between GOES infrar...

  3. Aerodynamic Design of a Tailless Aeroplan

    J. Friedl


    Full Text Available The paper presents an aerodynamic analysis of a one-seat ultralight (UL tailless aeroplane named L2k, with a very complicated layout. In the first part, an autostable airfoil with a low moment coefficient was chosen as a base for this problem. This airfoil was refined and modified to satisfy the design requirements. The computed aerodynamic characteristics of the airfoils for different Reynolds numbers (Re were compared with available experimental data. XFOIL code was used to perform the computations. In the second part, a computation of wing characteristics was carried out. All calculated cases were chosen as points on the manoeuvring and gust envelope. The vortex lattice method was used with consideration of fuselage and winglets for very complicated wing geometry. The PMW computer program developed at IAE was used to perform the computations. The computed results were subsequently used for structural and strength analysis and design.

  4. A note on the papers from the winter symposium of the Nordic Summer University held in Akureyri, Iceland, March, 1st-3rd 2013

    Jacob Dahl Rendtorff


    Full Text Available The study group “Towards a New Ethical Imagination. Political and social values in a Cosmopolitan World Society” of the Nordic Summer University had its winter meeting at the University of Akureyri, Iceland, March 1-3, 2013.We discussed different topics in the fields of moral, political, economic, and social philosophy, with the addition of a special theme i.e. ethical, political and legal issues in the Arctic region. It was a very fruitful meeting and we would like to thank the organisers at the University of Akureyri, in particular Águst Thor Árnason, the Icelandic NSU Coordinator, for all the hard work done in Akureyri.

  5. Electronic film with embedded micro-mirrors for solar energy concentrator systems

    Rabinowitz, Mario; Davidson, Mark


    A novel electronic film solar energy concentrator with embedded micro-mirrors that track the sun is described. The potential viability of this new concept is presented. Due to miniaturization, the amount of material needed for the optical system is minimal. Because it is light-weight and flexible, it can easily be attached to the land or existing structures. This presents an economic advantage over conventional concentrators which require the construction of a separate structure to support them, and motors to orient them to intercept and properly reflect sunlight. Such separate structures must be able to survive gusts, windstorms, earthquakes, etc. This concentrator utilizes the ground or existing edifices which are already capable of withstanding such vicissitudes of nature.

  6. De serpientes y de mujeres: a propósito de unos versos de quevedo

    Rafael M. Mérida Jiménez


    Full Text Available Para todo aquel que guste de la poesia castellana de los Siglos de Oro no habrá pasado desapercibido el ambivalente papel que interpreta la mujer como tema literario -ambi­ valencia de dilatada trayectoria, sin duda-. Si pudiéramos polarizar diríamos que esa mujer literaturizada, y por consiguiente tan irreal como extremadamente cotidiana, sufre por un lado la influencia de la lírica de tradición petrarquista (la dama idealizada, cúmulo de virtudes físicas y morales y, por otro, la difusión de los modelos de buena parte de Ia poesfa popu­ lar y de la religiosa (con una concepción más claramente terrena yen muchas ocasiones misógina.

  7. Material matters: Controllable rubber trailing edge flap regulates load on wind turbine blades

    Aagaard Madsen, Helge


    In wind farms, nearby wind turbines exert considerable influence and generate turbulence on turbine blades. Because the blades are so long, there can be considerable differences in localized loading from the gusts along the blade. The Risø DTU researchers has developed a controllable rubber...... trailing edge flap, known as CRTEF. The trailing edge blade design is expected to help mitigate localized loading, and its molded rubber design, the sharp trailing edge, produces less noise and greater output. With CRTEF, the blade automatically has a completely sharp edge. The elastic flap tested...... in an open jet wind tunnel shows promising results. In the wind tunnel, it is possible to regulate the wind speed as well as turn the blade profile to simulate a change in wind direction in relation to the profile....

  8. Characterisation and classification of RISØ P2546 cup anemometer

    Friis Pedersen, Troels


    The characteristics of the RISØ P2546 cup anemometer were investigated in detail by wind tunnel and laboratory tests. The characteristics include accredited calibration, tilt response measurements for tilt angles between -40° to 40°, gust responsemeasurements at 8m/s and turbulence intensities...... of 10%, 16% and 23%, step response measurements at step wind speeds 3,7, 8, 11,9 and 15,2m/s, measurement of torque characteristics at 8m/s, rotor inertia measurements and measurements of friction ofbearings at temperatures -20°C to 40°C. Characteristics were fitted to a time domain cup anemometer model....... The characteristics were transformed into the CLASSCUP classification scheme, and were related to the cup anemometer requirements in the Danishcertification system and in the IEC 61400-121 Committee Draft....

  9. Characterisation and classification of RISØ P2546 cup anemometer

    Friis Pedersen, Troels


    The characteristics of the RISØ P2546 cup anemometer were investigated in detail by wind tunnel and laboratory tests. The characteristics include accredited calibration, tilt response measurements for tilt angles between -40° to 40°, gust responsemeasurements at 8m/s and turbulence intensities...... of 10%, 16% and 23%, step response measurements at step wind speeds 3,7, 8, 11,9 and 15,2m/s, measurement of torque characteristics at 8m/s, rotor inertia measurements and measurements of friction ofbearings at temperatures -20°C to 40°C. Characteristics were fitted to a time domain cup anemometer model....... The characteristics were transformed into the CLASSCUP classification scheme, and were related to the cup anemometer requirements in the Danishcertification system and in the IEC 61400-121 Committee Draft....

  10. Maximum likelihood identification of aircraft stability and control derivatives

    Mehra, R. K.; Stepner, D. E.; Tyler, J. S.


    Application of a generalized identification method to flight test data analysis. The method is based on the maximum likelihood (ML) criterion and includes output error and equation error methods as special cases. Both the linear and nonlinear models with and without process noise are considered. The flight test data from lateral maneuvers of HL-10 and M2/F3 lifting bodies are processed to determine the lateral stability and control derivatives, instrumentation accuracies, and biases. A comparison is made between the results of the output error method and the ML method for M2/F3 data containing gusts. It is shown that better fits to time histories are obtained by using the ML method. The nonlinear model considered corresponds to the longitudinal equations of the X-22 VTOL aircraft. The data are obtained from a computer simulation and contain both process and measurement noise. The applicability of the ML method to nonlinear models with both process and measurement noise is demonstrated.

  11. Real-Time Embedded Control System for a Portable Meteorological Station

    Marcelo Moya


    Full Text Available The aim of this work is to design and code an embedded system for a portable automatic weather station. The portable station includes high performance sensors to measure parameters such as: i wind speed and direction, micro perturbations and wind gusts, ii air temperature, iii solar radiation, iv relative humidity, and v atmospheric pressure. The main contribution of this work is the development of an embedded control system operating in real time. This system is based on a Field Programmable Gate Array (FPGA device. The method developed guarantees high-resolution data acquisition of a number of samples in real time. The samples obtained are grouped and stored in a database, which will be used as a starting point for further analysis.

  12. Projection moire interferometry measurements of micro air vehicle wings

    Fleming, Gary A.; Bartram, Scott M.; Waszak, Martin R.; Jenkins, Luther N.


    Projection Moire Interferometry (PMI) has been used to measure the structural deformation of micro air vehicle (MAV) wings during a series of wind tunnel tests. The MAV wings had a highly flexible wing structure, generically reminiscent of a bat's wing, which resulted in significant changes in wing shape as a function of MAV angle-of-attack and simulated flight speed. This flow-adaptable wing deformation is thought to provide enhanced vehicle stability and wind gust alleviation compared to rigid wing designs. Investigation of the potential aerodynamic benefits of a flexible MAV wing required measurement of the wing shape under aerodynamic loads. PMI was used to quantify the aerodynamically induced changes in wing shape for three MAV wings having different structural designs and stiffness characteristics. This paper describes the PMI technique, its application to MAV testing, and presents a portion of the PMI data acquired for the three different MAV wings tested.

  13. Recent research and applications of GPS based technology for bridge health monitoring


    Today,long-span bridges are being designed to be more flexible and to resist extensive impacts from changes in temperature,severe wind gusts and earthquake tremors. Structural responses (especially displacement) of bridge structures are becoming increasingly important for the finite element (FE) modal updating,structural response prediction and safety evaluation. Methods of global displacement sensing were developed for these needs. This paper presents an overview of current research and development activities in the field of bridge health monitoring using the global positioning system (GPS). The GPS monitoring technology and its accuracy assessment method are also briefly described. Finally,existing problems and promising research efforts in the GPS based bridge health monitoring are discussed.

  14. De Voces ciudadanas a E-partedi : Comunicación, educación, discursos y estrategias al servicio de la participación ciudadana

    Marín Ochoa, Beatriz Elena


    Quince años, quince años cumplió el Grupo de Investigación en Comunicación Urbana, GICU, el año anterior, para celebrarlo realizamos un conversatorio que pretendía evaluar la manera como investigamos, invitamos a fundadores, expertos colegas para revisar los aprendizajes logrados durante estos años y lo que soñamos de cara a un país diferente, fruto de un proceso de postconflicto, y no es que no nos guste Colombia, no al contrario cada día encontramos más motivos que nos invitan a continuar l...

  15. ACCUWIND - Classification of five cup anemometers according to IEC61400-12-1

    Friis Pedersen, T.; Dahlberg, J.Aa.; Busche, P.


    The characteristics of five cup anemometers were investigated in detail, and data are presented in figures and tables. The characteristics include: normal wind tunnel calibrations; angular response measurements at 5, 8 and 11m/s; torque coefficient curve measurements from combined tilt and ramp-gust tests, torque coefficient curve measurements for non-tilted conditions; rotor inertia measurements and measurements of friction of bearings at temperatures -10 deg. C to 40 deg. C. The characteristics are fitted to two different time domain cup anemometer models, and simulations of the cup anemometers are made with artificial wind generators to make classifications according to annex I and J of the standard IEC 61400-12-1 on power performance measurements. Results of classification are shown in graphs of systematic deviations and class index tables. (au)

  16. Analysis of measurements of the Bora wind in Vipava valley

    Mole, Maruška; Bergant, Klemen; Honzak, Luka; Rakovec, Jože; Skok, Gregor; Stanič, Samo; Žabkar, Rahela; Škraba, Primož


    Bora wind is a phenomenon observed on the lee side of mountain chains, where the cold air-masses flowing over the barrier cause strong downslope winds. The relief profile of the SW Slovenia, which within 30 km of the coastal line first rises to a Karst plateau (300 m above sea level), then falls into the Vipava valley (100 m a.s.l.) and rises again to a mountainous barrier with maximum altitudes of about 1500 m a.s.l., creates an ideal setting for the occurrence of downslope winds in the Vipava valley. The occurrence of strong winds is correlated to the presence of cold NE air-flows in the higher, stably stratified layer, flowing over the SW-oriented orographic barrier, and warmer air on the lee side of the mountain range. These conditions lead to the flow of cold air from behind the barrier sinking into the valley bellow, generating very gusty and strong winds. Our data sample includes wind and gust speed measurements in the period from 27 January to 24 April 2012, which was selected due to strong Bora wind outbursts at that time. Wind speeds were measured using 15 wind sensors, out of which 5 were dedicated cup anemometers, positioned 4 meters above the ground and arranged in a two lines perpendicular to the barrier, line A consisting of 3 and line B of 2 instruments. The remaining wind sensors were ultrasonic, positioned at various heights above the ground at 10 different locations along the Vipava valley. The obtained gust speed measurements were analyzed in order to evaluate the frequency distribution of the wind gusts. In order to eliminate longer time intervals with light- or no wind, which can not be characterized as Bora and do not add any information to the gust frequency analysis, Fourier transform of the data was made for short time periods, taking into account single Bora wind outbursts only. Wind speed measurements were studied separately for each instrument line. In the line A, the first instrument was positioned in an elevated up-wind location on

  17. Characterisation and classification of RISOe P2546 cup anemometer

    Friis Pedersen, T.


    The characteristics of the RISOe P2546 cup anemometer were investigated in detail by wind tunnel and laboratory tests. The characteristics include accredited calibration, tilt response measurements for tilt angles between -40 degC to 40 degC, gust response measurements at 8m/s and turbulence intensities of 10%, 16% and 23%, step response measurements at step wind speeds 3,7, 8, 11,9 and 15,2m/s, measurement of torque characteristics at 8m/s, rotor inertia measurements and measurements of friction of bearings at temperatures -20 degC to 40 degC. Characteristics were fitted to a time domain cup anemometer model. The characteristics were transformed into the CLASSCUP classification scheme, and were related to the cup anemometer requirements in the Danish certification system and in the IEC 61400-121 Committee Draft. (au)

  18. Heaven’s Eyes Were Open Again (A Folk Tale of the She Ethnic Nationality)


    IN ancient times, the sky was as blue and clear as a large, round mirror. But one day a sudden gust of fierce wind blew in from the western sky and continued for days and days. On the ninth day, a cloud of smoke welled up from the west and covered the sun. The frightened people were left in terrible darkness. Yong Jian, a broad-shouldered youth who lived in Dongfeng Village at the foot of Fenghuang Mountain, made up his mind to remove the evil smoke and bring the sunshine back to the people. One day, Yong Jian met with an old man with a long beard. He told Yong Jian that there lived two nine-antler dragons in the western Shuanglong Mountain who had been preparing themselves for this moment for 9,990 years. The old man said that after the

  19. Thermal behavior optimization in multi-MW wind power converter by reactive power circulation

    Zhou, Dao; Blaabjerg, Frede; Lau, Mogens


    In the paper, an actively controlled reactive power influence to the thermal behavior of multi-MW wind power converter with Doubly-Fed Induction Generator (DFIG) is investigated. The allowable range of internal reactive power circulation is firstly mapped depending on the DC-link voltage as well...... as the induction generator and power device capacity. Then the effects of reactive power circulation towards current characteristic and thermal distribution of the two-level back-to-back power converter is analyzed and compared. Finally the thermal-oriented reactive power is introduced to the system...... in the conditions of constant wind speed and during wind gust. It is concluded that the thermal performance will be improved by injecting proper reactive power circulation in the wind turbine system and thereby be able to reduce the thermal cycling and enhance the reliability....

  20. Thermal Behavior Optimization in Multi-MW Wind Power Converter by Reactive Power Circulation

    Zhou, Dao; Blaabjerg, Frede; Lau, Mogens


    The influence of actively controlled reactive power on the thermal behavior of multi-MW wind power converter with a Doubly-Fed Induction Generator (DFIG) is investigated. First, the allowable range of internal reactive power circulation is mapped depending on the DC-link voltage as well...... as the induction generator and power device capacity. Then, the effects of reactive power circulation on current characteristic and thermal distribution of the two-level back-to-back power converter are analyzed and compared. Finally, the thermal-oriented reactive power control method is introduced to the system...... for the conditions of constant wind speed and during wind gust. It is concluded that the thermal performance will be improved by injecting proper reactive power circulation within the wind turbine system, thereby being able to reduce the thermal cycling and enhance the reliability of the power converter....

  1. F-8C digital CCV flight control laws

    Hartmann, G. L.; Hauge, J. A.; Hendrick, R. C.


    A set of digital flight control laws were designed for the NASA F-8C digital fly-by-wire aircraft. The control laws emphasize Control Configured Vehicle (CCV) benefits. Specific pitch axis objectives were improved handling qualities, angle-of-attack limiting, gust alleviation, drag reduction in steady and maneuvering flight, and a capability to fly with reduced static stability. The lateral-directional design objectives were improved Dutch roll damping and turn coordination over a wide range in angle-of-attack. An overall program objective was to explore the use of modern control design methodilogy to achieve these specific CCV benefits. Tests for verifying system integrity, an experimental design for handling qualities evaluation, and recommended flight test investigations were specified.

  2. Application of the concept of dynamic trim control to automatic landing of carrier aircraft. [utilizing digital feedforeward control

    Smith, G. A.; Meyer, G.


    The results of a simulation study of an alternative design concept for an automatic landing control system are presented. The alternative design concept for an automatic landing control system is described. The design concept is the total aircraft flight control system (TAFCOS). TAFCOS is an open loop, feed forward system that commands the proper instantaneous thrust, angle of attack, and roll angle to achieve the forces required to follow the desired trajector. These dynamic trim conditions are determined by an inversion of the aircraft nonlinear force characteristics. The concept was applied to an A-7E aircraft approaching an aircraft carrier. The implementation details with an airborne digital computer are discussed. The automatic carrier landing situation is described. The simulation results are presented for a carrier approach with atmospheric disturbances, an approach with no disturbances, and for tailwind and headwind gusts.

  3. Selection of sampling rate for digital control of aircrafts

    Katz, P.; Powell, J. D.


    The considerations in selecting the sample rates for digital control of aircrafts are identified and evaluated using the optimal discrete method. A high performance aircraft model which includes a bending mode and wind gusts was studied. The following factors which influence the selection of the sampling rates were identified: (1) the time and roughness response to control inputs; (2) the response to external disturbances; and (3) the sensitivity to variations of parameters. It was found that the time response to a control input and the response to external disturbances limit the selection of the sampling rate. The optimal discrete regulator, the steady state Kalman filter, and the mean response to external disturbances are calculated.

  4. MAMPs/PAMPs - elicitors of innate immunity in plants

    Erbs, Gitte; Newman, Mari-Anne


    Patterns (MAMPs or PAMPs), are recognised by the plant innate immune systems Pattern Recognition Receptors (PRRs). General bacterial elicitors, like lipopolysaccharides (LPS), flagellin (Flg), elongation factor Tu (EF-Tu), cold shock protein (CSP), peptidoglycan (PGN) and the enzyme superoxide dismutase...... (SodM) are known to act as MAMPs and induce immune responses in plants or plant cells (Gómez-Gómez and Boller, 2000; Erbs and Newman, 2003; Felix and Boller, 2003; Kunze et al., 2004; Watt et al., 2006, Gust et al., 2007; Erbs et al., unpublished). The corresponding PRRs for some of these bacterial...... elicitors have, in recent years, been identified. Here, the current knowledge regarding bacterial elicitors of innate immunity in plants is presented...

  5. Technical Note: A low cost unmanned aerial vehicle for ship based science missions

    E. Waugh


    Full Text Available A low-cost Unmanned Aerial Vehicle is compared with those already available and the motivation for its development is established. It is targeted at ship-based science missions and potential applications are described including a specific science case to measure white capping in the deep ocean. The current vehicle includes a range of more than 1000 Km, carrying a payload of 2 Kg and it can be launched and recovered from a coastal research vessel. The vehicle has flown successfully in Force 4 gusting Force 6–7 wind conditions, an important requirement for operation at sea. Data analysis is performed on images captured by the vehicle to provide a measurement of wave period and white capping fraction. The next stage of the project is to develop a suitable payload and perform a demonstration science mission.

  6. Probabilistic maximum-value wind prediction for offshore environments

    Staid, Andrea; Pinson, Pierre; Guikema, Seth D.


    , and probabilistic forecasts result in greater value to the end-user. The models outperform traditional baseline forecast methods and achieve low predictive errors on the order of 1–2 m s−1. We show the results of their predictive accuracy for different lead times and different training methodologies....... statistical models to predict the full distribution of the maximum-value wind speeds in a 3 h interval. We take a detailed look at the performance of linear models, generalized additive models and multivariate adaptive regression splines models using meteorological covariates such as gust speed, wind speed......, convective available potential energy, Charnock, mean sea-level pressure and temperature, as given by the European Center for Medium-Range Weather Forecasts forecasts. The models are trained to predict the mean value of maximum wind speed, and the residuals from training the models are used to develop...

  7. Combustion Properties of Biomass Flash Pyrolysis Oils: Final Project Report

    C. R. Shaddix; D. R. Hardesty


    Thermochemical pyrolysis of solid biomass feedstocks, with subsequent condensation of the pyrolysis vapors, has been investigated in the U.S. and internationally as a means of producing a liquid fuel for power production from biomass. This process produces a fuel with significantly different physical and chemical properties from traditional petroleum-based fuel oils. In addition to storage and handling difficulties with pyrolysis oils, concern exists over the ability to use this fuel effectively in different combustors. The report endeavors to place the results and conclusions from Sandia's research into the context of international efforts to utilize pyrolysis oils. As a special supplement to this report, Dr. Steven Gust, of Finland's Neste Oy, has provided a brief assessment of pyrolysis oil combustion research efforts and commercialization prospects in Europe.

  8. Planet-wide sand motion on mars

    Bridges, N.T.; Bourke, M.C.; Geissler, P.E.; Banks, M.E.; Colon, C.; Diniega, S.; Golombek, M.P.; Hansen, C.J.; Mattson, S.; McEwen, A.S.; Mellon, M.T.; Stantzos, N.; Thomson, B.J.


    Prior to Mars Reconnaissance Orbiter data, images of Mars showed no direct evidence for dune and ripple motion. This was consistent with climate models and lander measurements indicating that winds of sufficient intensity to mobilize sand were rare in the low-density atmosphere. We show that many sand ripples and dunes across Mars exhibit movement of as much as a few meters per year, demonstrating that Martian sand migrates under current conditions in diverse areas of the planet. Most motion is probably driven by wind gusts that are not resolved in global circulation models. A past climate with a thicker atmosphere is only required to move large ripples that contain coarse grains. ?? 2012 Geological Society of America.

  9. Estimation of rotor effective wind speeds using autoregressive models on Lidar data

    Giyanani, A.; Bierbooms, W. A. A. M.; van Bussel, G. J. W.


    Lidars have become increasingly useful for providing accurate wind speed measurements in front of the wind turbine. The wind field measured at distant meteorological masts changes its structure or was too distorted before it reaches the turbine. Thus, one cannot simply apply Taylor's frozen turbulence for representing this distant flow field at the rotor. Wind turbine controllers can optimize the energy output and reduce the loads significantly, if the wind speed estimates were known in advance with high accuracy and low uncertainty. The current method to derive wind speed estimations from aerodynamic torque, pitch angle and tip speed ratio after the wind field flows past the turbine and have their limitations, e.g. in predicting gusts. Therefore, an estimation model coupled with the measuring capability of nacelle based Lidars was necessary for detecting extreme events and for estimating accurate wind speeds at the rotor disc. Nacelle-mounted Lidars measure the oncoming wind field from utpo 400m(5D) in front of the turbine and appropriate models could be used for deriving the rotor effective wind speed from these measurements. This article proposes an auto-regressive model combined with a method to include the blockage factor in order to estimate the wind speeds accurately using Lidar measurements. An Armax model was used to determine the transfer function that models the physical evolution of wind towards the wind turbine, incorporating the effect of surface roughness, wind shear and wind variability at the site. The model could incorporate local as well as global effects and was able to predict the rotor effective wind speeds with adequate accuracy for wind turbine control actions. A high correlation of 0.86 was achieved as the Armax modelled signal was compared to a reference signal. The model could also be extended to estimate the damage potential during high wind speeds, gusts or abrupt change in wind directions, allowing the controller to act appropriately

  10. Comparing variable updraft melting layer heights to convective wind speeds using polarimetric radar data

    Harris, Ronald A., III

    The melting layer (ML) appears on vertical radar cross sections as a bright band of higher reflectivity values. Single polarization radars only detect this feature in stratiform precipitation events, whereas dual polarization radars offer the advantage of detecting the ML in both stratiform and convective precipitation events. The ML is known to be lifted higher locally within a convective updraft, so the goal of the present study was to determine if there is a correlation between the vertical displacement of the ML in an updraft (above the ambient ML) and the speed of the storm's reported wind gusts. Fourteen storms were investigated. Wind reports from the Storm Prediction Center (SPC) website were used and radar data were obtained from the National Climatic Data Center (NCDC) website for two dual polarization radar sites: Vance Air Force Base (KVNX) in Enid, OK, and Wichita, KS (KICT). Each storm was studied in detail using a combination of plan views of the cross correlation coefficient (rhoHV, which drops to anomalously low values within the ML) and vertical cross sections of reflectivity. Ultimately, no correlation was found between the height of the updraft ML and the speed of the convective wind gusts. This suggests that the height to which a parcel is lifted by an updraft does not affect the speed at which it descends in the ensuing downdraft. This is likely due to the fact that the mechanisms determining updraft strength are almost entirely separate from those that determine downdraft strength. For example, instability and lift govern updraft strength, whereas downdraft strength is predominantly governed by evaporational cooling and negative buoyancy.

  11. Investigation of Turbulence Effect on Dynamic Behaviour of Aircraft Through Use of JDYNASIM: A Platform Independent Simulation Software

    D. P. Coiro


    Full Text Available The need of fast and interactive tool to simulate aircraft behaviour is a demand of modern technology. This necessity is more evident when light aircraft and sailplanes are involved.. This paper presents an attempt to give simulation possibility almost to everyone through the use of JDynaSim code, written to meet this goal. JDynaSim is an interactive graphic flight simulation code written in JAVA and VRML languages which practically allows everyone to fly the aeroplane under investigation. This is true due to the fact that JAVA is a language born to work under a generic Internet browser (such as Microsoft Explorer or Netscape and thus it is independent from the operating system under which it is running. Dynamic motion equations are solved by 12 ordinary non-linear differential equations in which the non-linear forces are input in multidimensional matrix form and are interpolated at each time instant. Advancing in time is performed using a 4th order Runge-Kutta integration scheme. Translation equations of motion are written in a flight path axis system while rotational equations are written on body axis system. An on-purpose written pre-processor has to be used to transform forces to appropriate reference system. The code can interactively read mouse and keyboard inputs as well as files with command laws assigned in function of time. There is the possibility to record the interactive session performed and then to repeat the manoeuvre. This paper presents also the code extension for simulating the effect of gusts generated according to classical theories. In particular investigation has been performed to compare results coming from classical theories on aircraft responses to gusts inputs respect to those coming from JDynSim flight simulator. JDynaSim is available to everybody through Internet at the following URL:

  12. Astronomical site survey report on dust measurement, wind profile, optical turbulence, and their correlation with seeing over IAO-Hanle - Astronomical site survey report over IAO-Hanle

    Ningombam, Shantikumar S.; Kathiravan, S.; Parihar, P. S.; Larson, E. J. L.; Mohanan, Sharika; Angchuk, Dorje; Jorphel, Sonam; Rangarajan, K. E.; Prabhu, K.


    The present work discusses astronomical site survey reports on dust content, vertical distribution of atmospheric turbulence, precipitable water vapor (PWV), surface and upper-air data, and their effects on seeing over the Indian Astronomical Observatory (IAO) Hanle. Using Laser Particulate Counter, ambient dust measurements at various sizes (0.3 μm to 25 μm) were performed at various locations at the site during November 2015. Estimated volume concentration for the particle size at 0.5 μm was around 10,000 per cubic foot, which is equivalent to ten thousand class of clean room standard protocol. During the measurement, surface wind speed varied from 0-20 m s -1, while estimated aerosol optical depth (AOD) using Sky radiometer (Prede) varied from 0.02-0.04 at 500 nm, which indicates the site is fairly clean. The two independent measurements of dust content and aerosol concentrations at the site agreed well. The turbulence or wind gust at the site was studied with wind profiles at three different heights above the ground. The strength of the wind gust varies with time and altitude. Nocturnal temperature across seasons varied with a moderate at summer (6-8 ∘C) and lower in winter (4-5 ∘C). However, the contrast between the two is significantly small due to cold and extremely dry typical climatic conditions of the site. The present study also examined the effects of surface and upper-air data along with Planetary Boundary Layer (PBL) dynamics with seeing measurement over the site. Further, a comparative study of such observed parameters was conducted with other high altitude astronomical observatories across the globe.

  13. Targeted taste cell-specific overexpression of brain-derived neurotrophic factor in adult taste buds elevates phosphorylated TrkB protein levels in taste cells, increases taste bud size, and promotes gustatory innervation.

    Nosrat, Irina V; Margolskee, Robert F; Nosrat, Christopher A


    Brain-derived neurotrophic factor (BDNF) is the most potent neurotrophic factor in the peripheral taste system during embryonic development. It is also expressed in adult taste buds. There is a lack of understanding of the role of BDNF in the adult taste system. To address this, we generated novel transgenic mice in which transgene expression was driven by an α-gustducin promoter coupling BDNF expression to the postnatal expression of gustducin in taste cells. Immunohistochemistry revealed significantly stronger BDNF labeling in taste cells of high BDNF-expressing mouse lines compared with controls. We show that taste buds in these mice are significantly larger and have a larger number of taste cells compared with controls. To examine whether innervation was affected in Gust-BDNF mice, we used antibodies to neural cell adhesion molecule (NCAM) and ATP receptor P2X3. The total density of general innervation and specifically the gustatory innervation was markedly increased in high BDNF-expressing mice compared with controls. TrkB and NCAM gene expression in laser capture microdissected taste epithelia were significantly up-regulated in these mice. Up-regulation of TrkB transcripts in taste buds and elevated taste cell-specific TrkB phosphorylation in response to increased BDNF levels indicate that BDNF controls the expression and activation of its high affinity receptor in taste cells. This demonstrates a direct taste cell function for BDNF. BDNF also orchestrates and maintains taste bud innervation. We propose that the Gust-BDNF transgenic mouse models can be employed to further dissect the specific roles of BDNF in the adult taste system.

  14. Cyclones, windstorms and the IMILAST project

    Tim D. Hewson


    Full Text Available By way of introduction to the TELLUS thematic cluster on outcomes of the IMILAST project (Intercomparison of MId-LAtitude STorm diagnostics, this paper presents the results of new research that is fundamental for the correct interpretation of IMILAST results. Specifically we investigated the mesoscale structure of cyclonic windstorms, and the representation of those windstorms in re-analysis data. The paper concludes with an overview of the project itself. Twenty-nine historic windstorms are studied in detail, using wide-ranging observational data, and on this basis a conceptual model of the life cycle of a typical windstorm-generating cyclone is developed. The model delineates three wind phenomena, the warm jet, the sting jet and the cold jet, and maps out the typical damage footprint left by each. Focussing on the boundary layer, the physical processes at work in each jet zone are investigated. These include the impact of near-surface stability and exposure on gust strength. Based on numerous cases, a generic description of the sting jet is provided, with many new features highlighted. This phenomenon looks to be unique in that exceptional gusts can be realised well inland because destabilisation is activated from above. We next investigate how well the widely-referenced ERA-Interim re-analysis, that has been a primary data source for IMILAST, can represent windstorms. In many ways, performance is suboptimal. Compared to a benchmark manually-analysed dataset, windstorm-generating cyclones generally do not deepen rapidly enough. In part, this is a resolution limitation. For one medium-sized cyclone, it is shown, using other models, that horizontal resolution of order 20 km or better is required to capture the most damaging winds. In the context of IMILAST, which has used data at resolutions ≥80 km, this is a fundamental result. For this and other reasons, caution is clearly needed when inferring storm behaviour and severity from model

  15. A model for the estimation of storm losses and the identification of severe winter storms in Germany

    M. Klawa


    Full Text Available A storm loss model for Germany is presented. Input data to the model are the daily maximum gust wind speeds measured at stations distributed over the country. The individual daily peak gust values are scaled with the local climatological upper 2% quantile at each station. This scaling serves to take local conditions at the stations into account, and thus permits a simple spatial interpolation of the storm field. The next step is the computation of a loss index for each storm. It is based on the excess of (scaled wind speed over the upper 2% quantile, and on population numbers in the individual districts within Germany, with the latter serving as a proxy for the spatial distribution of values that could be affected by a storm. Using wind speeds in excess of the percentile value also serves to take spatial heterogeneity of vulnerability against storms into account. The aggregated storm index gives an estimate of the severity of an individual storm. Finally, the relation between actual loss produced by a storm and the index is estimated using published annual insurance loss due to windstorm in Germany. Index values are accumulated for each year, and the relation to actual loss is computed. The average ratio for the whole reference period is eventually used. It is shown that the interannual variability of storm-related losses can be reproduced with a correlation coefficient of r = 0.96, and even individual storm damages can be estimated. Based on these evaluations we found that only 50 storms account for about 80% of insured storm losses between 1970 and 1997.

  16. Forecasting challenges during the severe weather outbreak in Central Europe on 25 June 2008

    Púčik, Tomáš; Francová, Martina; Rýva, David; Kolář, Miroslav; Ronge, Lukáš


    On 25 June 2008, severe thunderstorms caused widespread damage and two fatalities in the Czech Republic. Significant features of the storms included numerous downbursts on a squall line that exhibited a bow echo reflectivity pattern, with sustained wind gusts over 32 m/s at several reporting stations. Moreover, a tornado and several downbursts of F2 intensity occurred within the convective system, collocated with the development of mesovortices within the larger scale bow echo. The extent of the event was sufficient to call it a derecho, as the windstorm had affected Eastern Germany, Southern Poland, Slovakia, Austria and Northern Hungary as well. Ahead of the squall line, several well-organized isolated cells occurred, exhibiting supercellular characteristics, both from a radar and visual perspective. These storms produced large hail and also isolated severe wind gusts. This paper deals mostly with the forecasting challenges that were experienced by the meteorologist on duty during the evolution of this convective scenario. The main challenge of the day was to identify the region that would be most affected by severe convection, especially as the numerical weather prediction failed to anticipate the extent and the progress of the derecho-producing mesoscale convective systems (MCSs). Convective storms developed in an environment conducive to severe thunderstorms, with strong wind shear confined mostly to the lower half of the troposphere. These developments also were strongly influenced by mesoscale factors, especially a mesolow centered over Austria and its trough stretching to Eastern Bohemia. The paper demonstrates how careful mesoscale analysis could prove useful in dealing with such convective situations. Remote-sensing methods are also shown to be useful in such situations, especially when they can offer sufficient lead time to issue a warning, which is not always the case.

  17. Astronomical site survey report on dust measurement, wind profile, optical turbulence, and their correlation with seeing over IAO-Hanle. Astronomical site survey report over IAO-Hanle

    Ningombam, Shantikumar S.; Kathiravan, S.; Parihar, P. S.; L. Larson, E. J.; Mohanan, Sharika; Angchuk, Dorje; Jorphel, Sonam; Rangarajan, K. E.; Prabhu, K.


    The present work discusses astronomical site survey reports on dust content, vertical distribution of atmospheric turbulence, precipitable water vapor (PWV), surface and upper-air data, and their effects on seeing over the Indian Astronomical Observatory (IAO) Hanle. Using Laser Particulate Counter, ambient dust measurements at various sizes (0.3 μm to 25 μm) were performed at various locations at the site during November 2015. Estimated volume concentration for the particle size at 0.5 μm was around 10,000 per cubic foot, which is equivalent to ten thousand class of clean room standard protocol. During the measurement, surface wind speed varied from 0-20 m s -1, while estimated aerosol optical depth (AOD) using Sky radiometer (Prede) varied from 0.02-0.04 at 500 nm, which indicates the site is fairly clean. The two independent measurements of dust content and aerosol concentrations at the site agreed well. The turbulence or wind gust at the site was studied with wind profiles at three different heights above the ground. The strength of the wind gust varies with time and altitude. Nocturnal temperature across seasons varied with a moderate at summer (6-8 ∘C) and lower in winter (4-5 ∘C). However, the contrast between the two is significantly small due to cold and extremely dry typical climatic conditions of the site. The present study also examined the effects of surface and upper-air data along with Planetary Boundary Layer (PBL) dynamics with seeing measurement over the site. Further, a comparative study of such observed parameters was conducted with other high altitude astronomical observatories across the globe.

  18. Site Characterization at a Tidal Energy Site in the East River, NY (usa)

    Gunawan, B.; Neary, V. S.; Colby, J.


    A comprehensive tidal energy site characterization is performed using ADV measurements of instantaneous horizontal current magnitude and direction at the planned hub centerline of a tidal turbine over a two month period, and contributes to the growing data base of tidal energy site hydrodynamic conditions. The temporal variation, mean current statistics, and turbulence of the key tidal hydrodynamic parameters are examined in detail, and compared to estimates from two tidal energy sites in Puget Sound. Tidal hydrodynamic conditions, including mean annual current (at hub height), the speed of extreme gusts (instantaneous horizontal currents acting normal to the rotor plane), and turbulence intensity (as proposed here, relative to a mean current of 2 m s-1) can vary greatly among tidal energy sites. Comparison of hydrodynamic conditions measured in the East River tidal straight in New York City with those reported for two tidal energy sites in Puget Sound indicate differences of mean annual current speeds, difference in the instantaneous current speeds of extreme gusts, and differences in turbulence intensities. Significant differences in these parameters among the tidal energy sites, and with the tidal resource assessment map, highlight the importance of conducting site resource characterization with ADV measurements at the machine scale. As with the wind industry, which adopted an International Electrotechnical Commission (IEC) wind class standard to aid in the selection of wind turbines for a particular site, it is recommended that the tidal energy industry adopt an appropriate standard for tidal current classes. Such a standard requires a comprehensive field campaign at multiple tidal energy sites that can identify the key hydrodynamic parameters for tidal current site classification, select a list of tidal energy sites that exhibit the range of hydrodynamic conditions that will be encountered, and adopt consistent measurement practices (standards) for site

  19. Exploring convective and sea-breeze dynamics using ensembles of idealised CRM simulations

    Robinson, F.; Sherwood, S.; Patterson, M.


    We report on continuing work using large ensembles of simulations by the WRF model in a CRM configuration with different idealised boundary and initial conditions, to work toward a better understanding of the role of mesoscale and boundary-layer dynamics in unorganised deep convection. Runs employ an idealised domain that is homogeneous except for a heated "island" in the middle, and are mostly 2-D. The WRF model with fully parameterised physics can successfully reproduce the greater intensity of land-based convection in general relative to that over oceans, a key benchmark. Heterogeneity of the surface appears to be the primary reason for the greater intensity, but is not accounted for in standard parameterisations of deep convection although some are beginning to account for cold-pool dynamics and gust front effects. Sea breeze and gust fronts created by this heterogeneity are crucial in determining the location of subsequent convective onset, and the timing of collisions strongly affects convective intensity. To better understand the propagation of these currents we use further simplified, dry runs of WRF with varying degrees of complexity in the boundary and initial conditions. These range from the most idealised, "lock-release" case common in laboratory studies, to more meteorological cases with realistic diurnal solar heating of a land surface. We find that the well-known Benjamin formula typically used to predict frontal propagation works for idealised currents studied previously, but fails badly for those with more realistic surface heating, due to the introduction of internal structure within the cold current as it evolves. We argue that this is the main reason that observed fronts often propagate much more slowly than predicted.

  20. Hanford Site climatological data summary 1999 with historical data

    DJ Hoitink; KW Burk; JV Ramsdell


    This document presents the climatological data measured at the US Department of Energy's Hanford Site for calendar year 1999. Pacific Northwest National Laboratory operates the Hanford Meteorology Station and the Hanford Meteorological Monitoring Network from which these data were collected. The information contained herein includes updated historical climatologies for temperature, precipitation, normal and extreme values of temperature and precipitation, and other miscellaneous meteorological parameters. Further, the data are adjunct to and update Hoitink et al. (1999), and Hoitink and Burk (1994, 1995, 1996, 1997, 1998); however, Appendix B-Wind Climatology (1994) is excluded. 1999 was warmer than normal at the Hanford Meteorology Station with an average temperature of 54.4 F, 1.1 F above normal (53.3 F). The hottest temperature was 105 F on July 28, while the coldest was 18 F on January 3. The maximum temperature of 64 F on August 30 was the lowest maximum temperature ever recorded in August, while the maximum temperature of 76 F on November 13 was the highest maximum temperature ever recorded in November. For the 12-month period, 6 months were warmer than normal and 6 were cooler than normal. 1999 was the fourth driest year on record. Precipitation totaled 3.75 inches, 60% of normal (6.26 inches); snowfall totaled 0.6 inch, the least calendar year snowfall on record (compared to the normal of 13.8 inches). 1999 was the windiest year on record with an average wind speed of 8.8 mph, 1.1 mph above normal (7.7 mph). There were 48 days with peak gust {ge} 40 mph, compared to a yearly average of 26 mph. The peak gust during the year was 65 mph on February 6. The heating-degree days for 1998--1999 were 4,802 (8% below the 5,231 normal). Cooling-degree days for 1999 were 891 (10% below the 994 normal).

  1. Evaluating the suitability of the SWAN/COSMO-2 model system to simulate short-crested surface waves for a narrow lake with complex bathymetry

    Michael Graf


    Full Text Available The spectral wave model SWAN (Simulating Waves Nearshore was applied to Lake Zurich, a narrow pre-Alpine lake in Switzerland. The aim of the study is to investigate whether the model system consisting of SWAN and the numerical weather prediction model COSMO-2 is a suitable tool for wave forecasts for the pre-Alpine Lake Zurich. SWAN is able to simulate short-crested wind-generated surface waves. The model was forced with a time varying wind field taken from COSMO-2 with hourly outputs. Model simulations were compared with measured wave data at one near-shore site during a frontal passage associated with strong on-shore winds. The overall course of the measured wave height is well captured in the SWAN simulation: the wave amplitude significantly increases during the frontal passage followed by a transient drop in amplitude. The wave pattern on Lake Zurich is quite complex. It strongly depends on the inherent variability of the wind field and on the external forcing due to the surrounding complex topography. The influence of the temporal wind resolution is further studied with two sensitivity experiments. The first one considers a low-pass filtered wind field, based on a 2-h running mean of COSMO-2 output, and the second experiment uses simple synthetic gusts, which are implemented into the SWAN model and take into account short-term fluctuations of wind speed at 1-sec resolution. The wave field significantly differs for the 1-h and 2-h simulations, but is only negligibly affected by the gusts.

  2. Horizontal geometrical reaction time model for two-beam nacelle LiDARs

    Beuth, Thorsten; Fox, Maik; Stork, Wilhelm


    Wind energy is one of the leading sustainable energies. To attract further private and state investment in this technology, a broad scaled drop of the cost of energy has to be enforced. There is a trend towards using Laser Doppler Velocimetry LiDAR systems for enhancing power output and minimizing downtimes, fatigue and extreme forces. Since most used LiDARs are horizontally setup on a nacelle and work with two beams, it is important to understand the geometrical configuration which is crucial to estimate reaction times for the actuators to compensate wind gusts. In the beginning of this article, the basic operating modes of wind turbines are explained and the literature on wind behavior is analyzed to derive specific wind speed and wind angle conditions in relation to the yaw angle of the hub. A short introduction to the requirements for the reconstruction of the wind vector length and wind angle leads to the problem of wind shear detection of angled but horizontal homogeneous wind fronts due to the spatial separation of the measuring points. A distance is defined in which the wind shear of such homogeneous wind fronts is not present which is used as a base to estimate further distance calculations. The reaction time of the controller and the actuators are having a negative effect on the effective overall reaction time for wind regulation as well. In the end, exemplary calculations estimate benefits and disadvantages of system parameters for wind gust regulating LiDARs for a wind turbine of typical size. An outlook shows possible future improvements concerning the vertical wind behavior.

  3. Effects of aerosol on evaporation, freezing and precipitation in a multiple cloud system

    Lee, Seoung Soo; Kim, Byung-Gon; Yum, Seong Soo; Seo, Kyong-Hwan; Jung, Chang-Hoon; Um, Jun Shik; Li, Zhanqing; Hong, JinKyu; Chang, Ki-Ho; Jeong, Jin-Yim


    Aerosol effects on clouds and precipitation account for a large portion of uncertainties in the prediction of the future course of global hydrologic circulations and climate. As a process of a better understanding of interactions between aerosol, clouds and precipitation, simulations are performed for a mixed-phase convective multiple-cloud system over the tropics. Studies on single-cloud systems have shown that aerosol-induced increases in freezing, associated increases in parcel buoyancy and thus the intensity of clouds (or updrafts) are a main mechanism which controls aerosol-cloud-precipitation interactions in convective clouds. However, in the multiple-cloud system that plays much more important roles in global hydrologic circulations and thus climate than single-cloud systems, aerosol effects on condensation play the most important role in aerosol-induced changes in the intensity of clouds and the effects on freezing play a negligible role in those changes. Aerosol-induced enhancement in evaporation intensifies gust fronts and increases the number of subsequently developing clouds, which leads to the substantial increases in condensation and associated intensity of convection. Although aerosol-induced enhancement in freezing takes part in the increases in condensation by inducing stronger convergence around cloud bottom, the increases in condensation are one order of magnitude larger than those in freezing. It is found that while aerosol-induced increases in freezing create intermittent extremely heavy precipitation, aerosol-induced increases in evaporation enhance light and medium precipitation in the multiple-cloud system here. This increase in light and medium precipitation makes it possible that cumulative precipitation increases with increasing aerosol concentration, although the increase is small. It is interesting that the altitude of the maximum of the time- and domain-averaged hydrometeor mass densities is quite robust to increases in aerosol

  4. A New Mechanism of Convective Cell Regeneration and Development Within a Two-Dimensional Multicell Storm

    BAO Xuwei; TAN Zhemin


    In this study, based on simulations of a two-dimensional multicell storm under a ground-layer upshear (Uz< 0) by a mesoscale numerical model, a new mechanism of cell regeneration and development within the multicell storm at the "less than optimal shear" proposed.In the presence of a ground-layer upshear, the circulation associated with the surface cold pool is not counteracted by that associated with the ambient wind shear, and the density current extends out faster, making the multicell storm stay at the "less than optimal shear" state. As a result, a new cell is triggered by the strong vertical perturbation ahead of the mature convection, rather than by the split-up from the updraft at the leading edge of the surface cold pool as well as the gust front. The latter is the mechanism at the "optimal" state proposed by Lin et al. in 1998. In the new mechanism, the regenerated cell grows fast with the incident warm moist air from the upstream of the multicell storm, and tends to cut off the moist airflow into the mature convection at its western sector. Consequently, the mature convection would weaken, be replaced, and eventually decay.Actually, these two different mechanisms come into play in a way depending on the relationship between the circulation of the low-level shear and that of the cold pool. When the circulation of the cold pool is stronger than that of the wind shear, the multicell storm is at the "less than optimal shear" state, and the new convective cell is produced by the disturbance ahead of the mature cell. When the circulation of the cold pool is weaker, the cell regeneration is dominated by the mechanism at the "optimal" state, and the new cell is split from the gust front updraft. Therefore, these two mechanisms are not contradictive. With a moderate ground-layer upsheax, they can alternately operate within a multicell storm.

  5. How do albatrosses fly around the world without flapping their wings?

    Richardson, Philip L.


    Albatrosses fly long distances over the Southern Ocean, even around the world, almost without flapping their wings; this has raised interest in how they perform such a feat. On a cruise to the South Atlantic I observed albatrosses soaring in a characteristic swooping zigzag flight that appears to combine two soaring techniques to gain energy-wind-shear soaring (dynamic soaring) using the vertical gradient of wind velocity and wave-slope soaring using updrafts over waves. The observed characteristic swooping flight is shown in a new illustration and interpreted in terms of the two soaring techniques. The energy gain estimated for “typical conditions” in the Southern Ocean suggests that wind-shear soaring provides around 80-90% of the total energy required for sustained soaring. A much smaller percentage is provided by wind shear in light winds and significant swell when wave-slope soaring dominates. A simple dynamical model of wind-shear soaring is proposed based on the concept of a bird flying across a sharp wind-shear layer as first described by Lord Rayleigh in 1883 and later developed with Pennycuick’s (2002) description of albatrosses “gust soaring.” In gust soaring a bird exploits structures in the wind field, such as separated boundary layers and eddies in the lee of wave crests, to obtain energy by climbing headed upwind and descending headed downwind across a thin wind-shear layer. Benefits of the model are that it is simple to understand, it captures the essential dynamics of wind-shear soaring, and it provides reasonable estimates of the minimum wind shear required for travel velocity in different directions with respect to the wind. Travel velocities, given in a travel velocity polar diagram, can be combined with tacking to fly in an upwind direction faster than the wind speed located at the top of the wind-shear layer.

  6. A two-dimensional iterative panel method and boundary layer model for bio-inspired multi-body wings

    Blower, Christopher J.; Dhruv, Akash; Wickenheiser, Adam M.


    The increased use of Unmanned Aerial Vehicles (UAVs) has created a continuous demand for improved flight capabilities and range of use. During the last decade, engineers have turned to bio-inspiration for new and innovative flow control methods for gust alleviation, maneuverability, and stability improvement using morphing aircraft wings. The bio-inspired wing design considered in this study mimics the flow manipulation techniques performed by birds to extend the operating envelope of UAVs through the installation of an array of feather-like panels across the airfoil's upper and lower surfaces while replacing the trailing edge flap. Each flap has the ability to deflect into both the airfoil and the inbound airflow using hinge points with a single degree-of-freedom, situated at 20%, 40%, 60% and 80% of the chord. The installation of the surface flaps offers configurations that enable advantageous maneuvers while alleviating gust disturbances. Due to the number of possible permutations available for the flap configurations, an iterative constant-strength doublet/source panel method has been developed with an integrated boundary layer model to calculate the pressure distribution and viscous drag over the wing's surface. As a result, the lift, drag and moment coefficients for each airfoil configuration can be calculated. The flight coefficients of this numerical method are validated using experimental data from a low speed suction wind tunnel operating at a Reynolds Number 300,000. This method enables the aerodynamic assessment of a morphing wing profile to be performed accurately and efficiently in comparison to Computational Fluid Dynamics methods and experiments as discussed herein.

  7. Atmospheric stability of surface boundary layer in coastal region of the Wol-Ryong site

    Lim, Hee-Chang


    In order to provide statistically reliable information of a wind energy site, accurate analysis on the atmospheric stability and climate characteristics in a certain area is a prerequisite. Two 2-D ultrasonic anemometers and one cup anemometer, located perpendicular to the prevailing wind direction, were used to measure the atmospheric wind environment at a height of 4.5 m in coastal region of the Wol-Ryong, Jeju, South Korea. The study is aiming to understand the atmospheric stability about a coastal region, and the effect of roughness length. We calculate the Monin-Obukhov length for division of atmospheric stability about unstable regime, neutral regime and stable regime. The distribution of diurnal Monin-Obukhov length is highly sporadic in the coastal region due to the effect of radiant heat from the surface or other environmental effects. In order to calculate the roughness length in coastal region, three different methods are applied in terms of the surface roughness, flow fluctuation and gust wind, which are called logarithmic profile, standard deviation and gust factor methods. In the study, the atmospheric stability was insignificant when applying these three methods. In the results, three different roughness length scales sufficiently showed the effect of obstacle and surface conditions around the measurement position. On the basis of an overall analysis of the short-term data measured in the Wol-Ryong area, Jeju Island, it is concluded that for the development of future wind energy resources, the Wol-Ryong site could be a good candidate for a future wind energy site.

  8. Characterising the relationship between weather extremes in Europe and synoptic circulation features

    S. Pfahl


    Full Text Available Extreme weather events in Europe are closely linked to anomalies of the atmospheric circulation and in particular to circulation features like cyclones and atmospheric blocking. In this study, this linkage is systematically characterised with the help of conditional cyclone and blocking frequencies during precipitation, wind gust and temperature extremes at various locations in Europe. Such conditional frequency fields can serve as a dynamical fingerprint of the extreme events and yield insights into their most important physical driving mechanisms. Precipitation extremes over the ocean and over flat terrain are shown to be closely related to cyclones in the vicinity and the associated dynamical lifting. For extreme precipitation over complex terrain, cyclone anomalies are found at more remote locations, favouring the flow of moist air towards the topography. Wind gust extremes are associated with cyclone and blocking anomalies in opposite directions, with the cyclones occurring mostly over the North and Baltic Seas for extreme events in central Europe. This setting is associated with pronounced surface pressure gradients and thus high near-surface wind velocities. Hot temperature extremes in northern and central Europe typically occur in the vicinity of a blocking anticyclone, where subsidence and radiative forcing are strong. Over southern Europe, blocking anomalies are shifted more to the north or northeast, indicating a more important role of warm air advection. Large-scale flow conditions for cold extremes are similar at many locations in Europe, with blocking anomalies over the North Atlantic and northern Europe and cyclone anomalies southeast of the cold extreme, both contributing to the advection of cold air masses. This characterisation of synoptic-scale forcing mechanisms can be helpful for better understanding and anticipating weather extremes and their long-term changes.

  9. 琼州海峡沿岸大风分布规律及影响系统分析%Analysis on Distribution Pattern of High Wind Events in Qiongzhou Strait Coastal Zones and Its Weather Systems

    郭冬艳; 姜涛; 陈有龙; 辛吉武


    Based on the data from automatic weather stations in the Qiongzhou Strait northern and southern coasts,the distribution patterns of high wind events in both coastal zones were analyzed.And the difference between them was also analyzed using weather systems.The high wind events are defined into two kinds:sustained winds and gust winds.The results are as follows:In southern coast,the high wind events are more frequent than in northern coast,but the speeds of gust winds are obviously bigger in northern coast than in southern coast.The high wind events in northern coastal zones and the sustained wind events in southern coastal zones mainly happen in autumn and winter but rare in other seasons,and the sustained wind events in both coastal zones mainly occurred by cold air.But the gust wind events in the southern coastal are quite special,which mainly happen in autumn and rarely occurred by cold air.In both coastal zones of the Qiongzhou Strait,the high wind events happen with more frequency and bigger speed on the east entrance than on the west entrance,and with the least in the middle of coastal zones.There exist pronounced phenomena that the northeast high wind was donsinant in both coasts of the strait.The high wind events are more easily occurred by cold air from east than from west.The Qiongzhou Strait can obviously make the turbulent intensity of cold air turning weak.%利用琼州海峡南北沿岸自动气象站2007年9月至2010年8月风向、风速资料,分析了最大风和极大风两种大风事件标准下的海峡沿岸大风分布规律,并基于大风天气影响系统分析南北沿岸大风的差异。结果表明:琼州海峡南侧沿岸大风事件多于北侧沿岸,其中最大风标准下的大风事件南侧沿岸明显多于北侧沿岸,但极大风标准下的大风事件北侧沿岸则多于南侧沿岸,且极大风风速明显偏大;北侧沿岸两种大风事件及南侧沿岸最大风事件均主要出现在秋冬季节,其中,两

  10. Analysis of physical parameter field and echo characteristics of Doppler radar in a thunderstorm process%一次雷暴大风的物理环境场和多普勒雷达回波特征

    阎访; 陈静; 卞韬; 廖颖慧; 张翠华


    A thunderstorm disaster appeared in Shijiazhuang region from 15:00 to 18:00 on August 27,2009. The mesoscale synoptic systems of this process such as gust front, squall line and mesocyclone and so on were detected by a Doppler radar at Xinle county of Shijiazhuang. The characteristics of physical parameter field of this process and Doppler radar product were analyzed. The results show that unstable stratification of temperature inversion in the low level and vertical wind shear in the middle and low levels provide favorable conditions for strong convec-tive development. Gust front has feedback action on the development of convective storm intensity. When gust front is moving away from the convective storm,the convective storm weakens or even dies out; when both are gradually close to each other,the convective storm strengthens or even develops into a supercell convective storm. Multiple single convective storm belt arrangement constitutes a squall line system, which brings wind speed spurt, wind zag,pressure upwelling and temperature falling. The supercell convective storm has the typical features of echoes with a "hook" shape,a "herringbone" shape,a "bow" shape,and deep lasting mesocyclone. The ground destructive wind is mainly brought by supercell convective storms.%2009年8月27日15-18时,石家庄地区出现雷暴大风灾害性强对流天气过程,石家庄北部新乐县多普勒雷达探测到了完整的阵风锋、飑线和中气旋等中尺度天气系统,对此次雷暴大风的环境场和多普勒雷达产品进行分析.结果表明:低层逆温、中低层垂直风切变较强的不稳定层结为强对流天气的发生发展提供了有利环境条件.阵风锋对对流风暴发展强度具有反馈作用,当二者逐渐远离时,对流风暴强度减弱甚至消亡;当二者逐渐靠近时,对流风暴发展加强,甚至发展为超级单体对流风暴.多单体对流风暴带状排列构成飑线系统,所经测站出现风速突增、风

  11. Numerical modeling of aerodynamics of airfoils of micro air vehicles in gusty environment

    Gopalan, Harish

    The superior flight characteristics exhibited by birds and insects can be taken as a prototype of the most perfect form of flying machine ever created. The design of Micro Air Vehicles (MAV) which tries mimic the flight of birds and insects has generated a great deal of interest as the MAVs can be utilized for a number of commercial and military operations which is usually not easily accessible by manned motion. The size and speed of operation of a MAV results in low Reynolds number flight, way below the flying conditions of a conventional aircraft. The insensitivity to wind shear and gust is one of the required factors to be considered in the design of airfoil for MAVs. The stability of flight under wind shear is successfully accomplished in the flight of birds and insects, through the flapping motion of their wings. Numerous studies which attempt to model the flapping motion of the birds and insects have neglected the effect of wind gust on the stability of the motion. Also sudden change in flight conditions makes it important to have the ability to have an instantaneous change of the lift force without disturbing the stability of the MAV. In the current study, two dimensional rigid airfoil, undergoing flapping motion is studied numerically using a compressible Navier-Stokes solver discretized using high-order finite difference schemes. The high-order schemes in space and in time are needed to keep the numerical solution economic in terms of computer resources and to prevent vortices from smearing. The numerical grid required for the computations are generated using an inverse panel method for the streamfunction and potential function. This grid generating algorithm allows the creation of single-block orthogonal H-grids with ease of clustering anywhere in the domain and the easy resolution of boundary layers. The developed numerical algorithm has been validated successfully against benchmark problems in computational aeroacoustics (CAA), and unsteady viscous

  12. Case study: A severe hailstorm and strong downbursts over northeastern Slovenia on June 16th 2009

    Korosec, M.


    Introduction A strong isolated storm complex with bow echo feature crossed northeastern Slovenia in the late afternoon hours and caused extensive damage due to severe wind gusts near 30m/s, excessive rainfalls and large hail. Synoptic situation On June 16th 2009, an upper-level ridge persists over southern Europe while a positively tilted short-wave trough, connected to a complex deep trough over northern Europe, crosses central Europe. Accompanied by this trough, a cold front is extending southwestwards towards the Alps. A relatively strong jet steak wraps around the trough axis and creates strong shear environment which overlaps with a narrow band of unstable airmass present ahead of the coming frontal boundary. Behind this trough/front over central Europe, a high pressure area is developing with stable conditions. Over Slovenia, strong surface heating was on going through the day but lack of near-surface convergence zones, limited moisture and strong capping inversion surpressed any storm initiation in the afternoon. Presentation of research This case study will go through a research of damaging bow echo which caused extensive damage due to severe winds, excessive rainfalls and large hail over much of northeastern Slovenia. Numerous trees were down or uprooted and numerous roofs were blown off or were seriously damaged due to severe wind gusts near or exceeding 30m/s. At first stages, when an isolated severe storm entered Slovenia, it had classic high precipitation supercell features while it transformed into a powerful bow echo later on. Very large hail up to 6cm in diameter was first observed in southeast Austria and near the border with Slovenia, while later on the main threat was very strong wind gusts and intense rainfalls. This research paper will show a detailed analysis of the synoptic situation including analysis of satellite, radar and surface observations. Radar imagery clearly showed isolated storm trailing along the near-surface frontal boundary as

  13. Origins of Aircraft-Damaging Clear-Air Turbulence during the 9 December 1992 Colorado Downslope Windstorm: Numerical Simulations and Comparison with Observations.

    Clark, Terry L.; Hall, William D.; Kerr, Robert M.; Middleton, Don; Radke, Larry; Ralph, F. Martin; Neiman, Paul J.; Levinson, David


    horizontal vortex tubes (HVTs) aligned with the mean flow. These HVTs remained aloft while they propagated downstream at about the elevation of the aircraft incident, and evidence for such a vortex was seen by the lidar. The model and observations suggest that one of these intense vortices may have caused the aircraft incident.Reports of strong surface gusts were intermittent along the Front Range during the period of this study. The model showed that interactions between the gravity waves and flow-aligned jet stream undulations result in isolated occurrences of strong surface gusts in line with observations. The simulations show that strong shears on the upper and bottom surfaces of the jet stream combine to provide an episodic `downburst of turbulence.' In the present case, the perturbations of the jet stream provide a funnel-shaped shear zone aligned with the mean flow that acts as a guide for the downward transport of turbulence resulting from breaking gravity waves. The physical picture for the upper levels is similar to the surface gusts described by Clark and Farley resulting from vortex tilting. The CAT feeding into this funnel came from all surfaces of the jet stream with more than half originating from the vertically inclined shear zones on the bottom side of the jet stream. Visually the downburst of turbulence looks similar to a rain shaft plummeting to the surface and propagating out over the plains leaving relatively quiescent conditions behind.

  14. Estimation of internal nutrient release in large shallow Lake Taihu, China


    ca. 10,000 ton/a, and PO43--P is ca. 900 ton/a. In the dynamic condition, nutrient release following sediment suspension was estimated according to three different intensities of wind forcing which were defined as "calm" (wind speed is less than 2 m/s), "gentle" (wind speed is greater than 2 m/s and less than 6 m/s) and "gust" (wind speed is greater than 6 m/s). The release rate in the condition of "calm" was estimated in terms of the nutrient release in the laboratory experimental static condition; whereas the release rate in conditions of "gentle" and "gust" was estimated in terms of measurement during sediment resuspension conducted in flume experiments. With the observation of wind velocity and frequency in 2001, each type of wind forcing took the frequency of 12%, 82% and 6% for "calm", "gentle" and "gust", respectively. The yearly release of nitrogen was 81,000 ton and phosphorus was 21,000 ton, which is about 2-6 folds of annual external loading, respectively.

  15. The Strong Wind event of 24th January 2009 in Catalonia: a social impact analysis

    Amaro, J.; Aran, M.; Barberia, L.; Llasat, M. C.


    Although strong winds are frequent in Catalonia, one of the events with the strongest impact in recent years was on January 24th 2009. An explosive cyclogenesis process took place in the Atlantic: pressure fell 30 hPa in less than 24 hours. The strong wind storm pounded the northern of Spain and the south of France with some fatalities and important economic losses in these regions. Several automatic weather stations recorded wind gusts higher than 100 km/h in Catalonia. Emergency services received more than 20.000 calls in 24 hours and there were 497 interventions in only 12 hours. As a consequence of fallen and uprooted trees railway and road infrastructures got damages and more than 30.000 customers had no electricity during 24 hours. Unfortunately there were a total of 6 fatalities, two of them because of fallen trees and the other ones when a sports centre collapsed over a group of children. In Spain, insurance policies cover damages due to strong winds when fixed thresholds are overcome and, according to the Royal Decree 300/2004 of 20th February, extraordinary risk are assumed by the Consorcio de Compensación de Seguros. Subsequently, Public Weather Services (PWS) had an increased on the number of requests received from people affected by this event and from insurance companies, for the corresponding indemnity or not. As an example, during the first month after the event, in the Servei Meteorològic de Catalunya (SMC) more than 600 requests were received only related to these damages (as an average PWS of SMC received a total of 400 requests per month). Following the research started by the Social Impact Research Group of MEDEX project, a good vulnerability indicator of a meteorological risk can be the number of requests reported. This study uses the information received in the PWS of the SMC during the six months after the event, according the criteria and methodology established in Gayà et al (2008). The objective is to compare the vulnerability with the

  16. Cloud albedo increase from carbonaceous aerosol

    W. R. Leaitch


    Full Text Available Airborne measurements from two consecutive days, analysed with the aid of an aerosol-adiabatic cloud parcel model, are used to study the effect of carbonaceous aerosol particles on the reflectivity of sunlight by water clouds. The measurements, including aerosol chemistry, aerosol microphysics, cloud microphysics, cloud gust velocities and cloud light extinction, were made below, in and above stratocumulus over the northwest Atlantic Ocean. On the first day, the history of the below-cloud fine particle aerosol was marine and the fine particle sulphate and organic carbon mass concentrations measured at cloud base were 2.4 μg m−3 and 0.9 μg m−3 respectively. On the second day, the below-cloud aerosol was continentally influenced and the fine particle sulphate and organic carbon mass concentrations were 2.3 μg m−3 and 2.6 μg m−3 respectively. Over the range 0.06–0.8 μm diameter, the shapes of the below-cloud size distributions were similar on both days and the number concentrations were approximately a factor of two higher on the second day. The cloud droplet number concentrations (CDNC on the second day were approximately three times higher than the CDNC measured on the first day. Using the parcel model to separate the influence of the differences in gust velocities, we estimate from the vertically integrated cloud light scattering measurements a 6% increase in the cloud albedo principally due to the increase in the carbonaceous components on the second day. Assuming no additional absorption by this aerosol, a 6% albedo increase translates to a local daytime radiative cooling of ∼12 W m−2. This result provides observational evidence that the role of anthropogenic carbonaceous components in the cloud albedo effect can be much larger than that of anthropogenic sulphate, as some global simulations have indicated.

  17. Research in aeroelasticity[Wind turbines

    Bak, C.


    In the Energy Research Project 'Program for Research in Applied Aeroelasticity' (EFP2005), Risoe National Laboratory (Risoe) and the Technical University of Denmark (DTU) have applied and further developed the tools in the aeroelastic design complex. The main results from the project are: 1) Adding a winglet to a wind turbine blade for minimizing the induced drag of the blade led to the biggest increase in power of 1.4%. 2) Transient wind loads during pitch motion are determined using CFD. Compared to the NREL/NASA Ames test, reasonably good agreement is seen. 3) A general method was developed for the determination of 3D angle of attack for rotating blades from either measurements or numerical computations using CFD. 4) A model of the far wake behind wind turbines was developed for stability studies of the tip vortices in the far wake. 5) Investigating the blade root region showed that the power efficiency, CP, locally can be increased significantly beyond the Betz limit, but that the global CP for the rotor cannot exceed the Betz limit. When including tip losses and a minimum blade drag coefficient, a maximum rotor CP in the range of 0.51-0.52 was obtained. 6) A new airfoil family was designed and a 3D airfoil design tool was developed. Compared to the Risoe-B1 family, the new airfoil family showed similar or improved aerodynamic and structural characteristics. 7) Four different airfoils were analyzed to reveal the differences between 2D and 3D CFD. The major conclusions are the dependency of computational results to transition modelling, and the ability of 3D DES calculations to realistically simulate the turbulent wake of an airfoil in stall. 8) The capability of a theory for simulation of Gaussian turbulence driven gust events was demonstrated by emulating a violent shear gust event from a complex site. An asymptotic model for the PDF of the largest excursion from the mean level, during an arbitrary recurrence period, has been derived for a stochastic

  18. Multidisciplinary Design Optimization of A Highly Flexible Aeroservoelastic Wing

    Haghighat, Sohrab

    A multidisciplinary design optimization framework is developed that integrates control system design with aerostructural design for a highly-deformable wing. The objective of this framework is to surpass the existing aircraft endurance limits through the use of an active load alleviation system designed concurrently with the rest of the aircraft. The novelty of this work is two fold. First, a unified dynamics framework is developed to represent the full six-degree-of-freedom rigid-body along with the structural dynamics. It allows for an integrated control design to account for both manoeuvrability (flying quality) and aeroelasticity criteria simultaneously. Secondly, by synthesizing the aircraft control system along with the structural sizing and aerodynamic shape design, the final design has the potential to exploit synergies among the three disciplines and yield higher performing aircraft. A co-rotational structural framework featuring Euler--Bernoulli beam elements is developed to capture the wing's nonlinear deformations under the effect of aerodynamic and inertial loadings. In this work, a three-dimensional aerodynamic panel code, capable of calculating both steady and unsteady loadings is used. Two different control methods, a model predictive controller (MPC) and a 2-DOF mixed-norm robust controller, are considered in this work to control a highly flexible aircraft. Both control techniques offer unique advantages that make them promising for controlling a highly flexible aircraft. The control system works towards executing time-dependent manoeuvres along with performing gust/manoeuvre load alleviation. The developed framework is investigated for demonstration in two design cases: one in which the control system simply worked towards achieving or maintaining a target altitude, and another where the control system is also performing load alleviation. The use of the active load alleviation system results in a significant improvement in the aircraft performance

  19. The European storm Kyrill in January 2007: synoptic evolution, meteorological impacts and some considerations with respect to climate change

    A. H. Fink


    Full Text Available The synoptic evolution and some meteorological impacts of the European winter storm Kyrill that swept across Western, Central, and Eastern Europe between 17 and 19 January 2007 are investigated. The intensity and large storm damage associated with Kyrill is explained based on synoptic and mesoscale environmental storm features, as well as on comparisons to previous storms. Kyrill appeared on weather maps over the US state of Arkansas about four days before it hit Europe. It underwent an explosive intensification over the Western North Atlantic Ocean while crossing a very intense zonal polar jet stream. A superposition of several favourable meteorological conditions west of the British Isles caused a further deepening of the storm when it started to affect Western Europe. Evidence is provided that a favourable alignment of three polar jet streaks and a dry air intrusion over the occlusion and cold fronts were causal factors in maintaining Kyrill's low pressure very far into Eastern Europe.

    Kyrill, like many other strong European winter storms, was embedded in a pre-existing, anomalously wide, north-south mean sea-level pressure (MSLP gradient field. In addition to the range of gusts that might be expected from the synoptic-scale pressure field, mesoscale features associated with convective overturning at the cold front are suggested as the likely causes for the extremely damaging peak gusts observed at many lowland stations during the passage of Kyrill's cold front. Compared to other storms, Kyrill was by far not the most intense system in terms of core pressure and circulation anomaly. However, the system moved into a pre-existing strong MSLP gradient located over Central Europe which extended into Eastern Europe. This fact is considered determinant for the anomalously large area affected by Kyrill.

    Additionally, considerations of windiness in climate change simulations using two state-of-the-art regional climate

  20. 小迎角纵向不稳定飞机起飞安全性分析%Take-off safety analysis of aircraft with longitudinal static instability at low angles of attack

    耿建中; 姚海林; 段卓毅


    由于螺旋桨滑流的影响,某运输机起飞构型在小迎角时纵向稳定性裕度不足,甚至不稳定,给飞机带来安全隐患.分析了某运输机起飞构型纵向力矩特性,讨论了螺旋桨滑流对纵向静稳定性的影响、影响飞机起飞时的安全因素和进入小迎角飞行的条件,建立了飞机起飞的数学仿真模型,通过大量的仿真计算,研究了突风和驾驶员误操纵对飞机起飞安全性的影响,给出了起飞时飞机所能抗御的最大突风速度.研究结果表明,某运输机小迎角稳定裕度不足,不稳定对飞机安全起飞的影响可以不予考虑.%The propeller slipstream result in longitudinal stability margin insufficient,even static instability at low angles of attack of an aircraft,which may cause potential problem. In order to study the effect of the static instability on take-off safety,the effect of propeller slipstream on longitudinal static stability was discussed. The pitching moment characteristic,the factor which has effect on safe take-off,and the con-ditons which may cause an aircraft flying at low angles attack were analyzed. Building dynamic model,the influence of gust and the pilot misoperation on the take-off safety were studied through computation and simulation. The maximum velocity of gust that an aircraft can resist was given. The result indicates the effect of the static instability on the take-off safety can be neglected.

  1. Coupled nonlinear aeroelasticity and flight dynamics of fully flexible aircraft

    Su, Weihua

    This dissertation introduces an approach to effectively model and analyze the coupled nonlinear aeroelasticity and flight dynamics of highly flexible aircraft. A reduced-order, nonlinear, strain-based finite element framework is used, which is capable of assessing the fundamental impact of structural nonlinear effects in preliminary vehicle design and control synthesis. The cross-sectional stiffness and inertia properties of the wings are calculated along the wing span, and then incorporated into the one-dimensional nonlinear beam formulation. Finite-state unsteady subsonic aerodynamics is used to compute airloads along lifting surfaces. Flight dynamic equations are then introduced to complete the aeroelastic/flight dynamic system equations of motion. Instead of merely considering the flexibility of the wings, the current work allows all members of the vehicle to be flexible. Due to their characteristics of being slender structures, the wings, tail, and fuselage of highly flexible aircraft can be modeled as beams undergoing three dimensional displacements and rotations. New kinematic relationships are developed to handle the split beam systems, such that fully flexible vehicles can be effectively modeled within the existing framework. Different aircraft configurations are modeled and studied, including Single-Wing, Joined-Wing, Blended-Wing-Body, and Flying-Wing configurations. The Lagrange Multiplier Method is applied to model the nodal displacement constraints at the joint locations. Based on the proposed models, roll response and stability studies are conducted on fully flexible and rigidized models. The impacts of the flexibility of different vehicle members on flutter with rigid body motion constraints, flutter in free flight condition, and roll maneuver performance are presented. Also, the static stability of the compressive member of the Joined-Wing configuration is studied. A spatially-distributed discrete gust model is incorporated into the time simulation

  2. Particulate Matter Concentration Levels in South Central Richmond, California (Invited)

    Bonner, B.; Byias, C.; Cuff, K. E.; Diaz, J.; Love, K.; Marks-Block, T.; McLane, F.; Mollique, Z.; Montes, E.; Ross, R.; Washington, B.


    South Central Richmond, California is the home of one of the nation’s most innovative green workforce training centers, Richmond BUILD - Green Jobs Training facility. A near constant stream of young people engaged in training activities, instructors, invited guests, and journalists of various ages can be seen moving in and out of the facility nearly every day of the week throughout a given year. Additionally, the comings and goings of young children and adults associated with a mid-sized elementary school just north of the facility contributes to the general area’s substantial human traffic. Unfortunately, however, a major highway, Interstate 580, a major thoroughfare, 23rd Street and a railway line operated by Burlington Northern Santa Fe, Union Pacific, and the Richmond Pacific Railroad frame the triangular area within which these two sites are situated. In addition, a major petrochemical complex and several shipping facilities are located less than three kilometers away north and west of this area. As part of a general assessment of air quality in this heavily human traveled area, we conducted a study of particulate matter (PM) concentrations over a five-month period beginning in August of 2009. Measurements were made at a variety of locations, and results were used to map the spatial distribution of PM of various sizes. Regions of high concentration levels were identified, and these particular areas then were monitored over time. Preliminary results of our study indicate that regions with high concentrations are consistent across the range of particle sizes measured, which suggests a common source for PM found in the study area. As these regions are located close to a major thoroughfare and railway line, we believe that diesel-burning vehicles are major contributors to the PM levels found in the study area. Time series results suggest a fairly strong correlation between higher than average PM concentrations and abnormally high wind gusts. On days when wind

  3. Riding and handling qualities of light aircraft: A review and analysis

    Smetana, F. O.; Summery, D. C.; Johnson, W. D.


    Design procedures and supporting data necessary for configuring light aircraft to obtain desired responses to pilot commands and gusts are presented. The procedures employ specializations of modern military and jet transport practice where these provide an improvement over earlier practice. General criteria for riding and handling qualities are discussed in terms of the airframe dynamics. Methods available in the literature for calculating the coefficients required for a linearized analysis of the airframe dynamics are reviewed in detail. The review also treats the relation of spin and stall to airframe geometry. Root locus analysis is used to indicate the sensitivity of airframe dynamics to variations in individual stability derivatives and to variations in geometric parameters. Computer programs are given for finding the frequencies, damping ratios, and time constants of all rigid body modes and for generating time histories of aircraft motions in response to control inputs. Appendices are included presenting the derivation of the linearized equations of motion; the stability derivatives; the transfer functions; approximate solutions for the frequency, damping ratio, and time constants; an indication of methods to be used when linear analysis is inadequate; sample calculations; and an explanation of the use of root locus diagrams and Bode plots.

  4. Calibration of NASA Turbulent Air Motion Measurement System

    Barrick, John D. W.; Ritter, John A.; Watson, Catherine E.; Wynkoop, Mark W.; Quinn, John K.; Norfolk, Daniel R.


    A turbulent air motion measurement system (TAMMS) was integrated onboard the Lockheed 188 Electra airplane (designated NASA 429) based at the Wallops Flight Facility in support of the NASA role in global tropospheric research. The system provides air motion and turbulence measurements from an airborne platform which is capable of sampling tropospheric and planetary boundary-layer conditions. TAMMS consists of a gust probe with free-rotating vanes mounted on a 3.7-m epoxy-graphite composite nose boom, a high-resolution inertial navigation system (INS), and data acquisition system. A variation of the tower flyby method augmented with radar tracking was implemented for the calibration of static pressure position error and air temperature probe. Additional flight calibration maneuvers were performed remote from the tower in homogeneous atmospheric conditions. System hardware and instrumentation are described and the calibration procedures discussed. Calibration and flight results are presented to illustrate the overall ability of the system to determine the three-component ambient wind fields during straight and level flight conditions.

  5. Statistic characteristics and weather significance of infrared TBB during May―August in Beijing and its vicinity


    In order to meet the demand of nowcasting convective storms in Beijing, the climatological characteristics of convective storms in Beijing and its vicinity were analyzed based on the infrared (IR) temperature of black body (TBB) data during May―August of 1997―2004. The climatological probabilities, the diurnal cycle and the spatial distribution of convective storms are given respectively in this paper. The results show that the climatological characteristics of convective storms denoted by TBB≤-52℃ are consistent with those statistic studies based on the surface and lightning observations. Furthermore, the climatological characteristics of May and June are very different from those of July and August, showing that there are two types of convective storms in this region. One occurs in the transient polar air mass on the midlatitude continent during the late spring and early summer. This type of convection arises with thunder, strong wind gust and hail over the mountainous area in the northern part of this region from afternoon to nightfall, the other occurs with heavy rainfall in the warm and moist air mass over the North China Plain and vicinity of Bohai Sea. This study also shows that the long-term data of IR TBB observed by geostationary satellite can complement the temporal and spatial limitation of the weather radar and surface observations.

  6. Tendon-Sheath Mechanisms in Flexible Membrane Wing Mini-UAVs: Control and Performance

    Tegoeh Tjahjowidodo


    Full Text Available Flexible membrane wings (FMWs are known for two inherent advantages, that is, adaptability to gusty airflow as the wings can flex according to the gust load to reduce the effective angle of attack and the ability to be folded for compact storage purposes. However, the maneuverability of UAV with FMWs is rather limited as it is impossible to install conventional ailerons. The maneuver relies only on the rudders. Some applications utilize torque rods to warp the wings, but this approach makes the FMW become unfoldable. In this research, we proposed the application of a tendon-sheath mechanism to manipulate the wing shape of UAV. Tendon-sheath mechanism is relatively flexible; thus, it can also be folded together with the wings. However, its severe nonlinearity in its dynamics makes the wing warping difficult to control. To compensate for the nonlinearity, a dedicated adaptive controller is designed and implemented. The proposed approach is validated experimentally in a wind tunnel facility with imitated gusty condition and subsequently tested in a real flight condition. The results demonstrate a stable and robust wing warping actuation, while the adaptive washout capability is also validated. Accurate wing warping is achieved and the UAV is easily controlled in a real flight test.

  7. Supervising Control for Unmanned Aerial Vehicles

    Saeed ur Rehman Sarwar


    Full Text Available A small UAV is considered as a test UAV, and its already published aerodynamic data is used for its modeling. Proportional Integral Differential (PID controller is designed for pitch attitude control. Atmospheric disturbances such as wind shear and turbulence significantly influence the attitude of UAVs. For this study rotary gust is considered as atmospheric disturbance. Pitch response in presence of atmospheric disturbance is presented. In order to improve the performance in presence of atmospheric disturbance, a supervisory mechanism is proposed. Supervisory mechanism is composed of two modules, “observer module” and “correction generator module.” The human thinking like logic is developed for observer module so that it keeps monitoring the status of flight through specified inputs and outputs from the system and instructs the correction generator module to augment main controller by adding compensation commands. Correction generator module works on fuzzy logic. Simulation results show significant reduction in pitch errors after augmenting the supervisory mechanism, hence proving the efficacy of proposed scheme.

  8. Hollow mesoporous silica nanoparticles facilitated drug delivery via cascade pH stimuli in tumor microenvironment for tumor therapy.

    Liu, Junjie; Luo, Zhong; Zhang, Jixi; Luo, Tiantian; Zhou, Jun; Zhao, Xiaojing; Cai, Kaiyong


    To efficiently deliver anti-cancer drug to tumor site and reduce its toxic side effects on normal tissues, a polyethylene glycol (PEG) shielding and tumor microenvironment triggering cascade pH-responsive hollow mesoporous silica nanoparticles (HMSNs) drug delivery system was fabricated. 3-(3, 4-dihydroxyphenyl) propionic acid (DHPA) functionalized beta-cyclodextrin (β-CD) was grafted onto the surfaces of HMSNs via boronic acid-catechol ester bonds. Then, PEG conjugated adamantane (Ada) was anchored on HMSNs-β-CD nanocarrier via host-gust interaction. Various techniques proved the successful fabrication of the system. The in vitro tests confirmed that the system was biocompatible. After the system permeating into tumor via enhanced permeability and retention (EPR) effect, the benzoic-imine bonds between the PEG and Ada were cleaved under weak acid condition in tumor microenvironment (pH 6.8), while the dissociated PEG protective layer facilitating cellular uptake of HMSNs system. Subsequently, the boronic acid-catechol ester bonds linkers further hydrolyzed under even low endosomal pH (4.5-6.5) condition for intracellular drug delivery, leading to efficient cell apoptosis. The in vivo results demonstrated that drug loaded HMSNs significantly inhibited tumor growth while only with minimal toxic side effects. The strategy provides new insight into the development of new generation of drug delivery carriers triggering by tumor microenvironment.

  9. Flight Loads Prediction of High Aspect Ratio Wing Aircraft Using Multibody Dynamics

    Michele Castellani


    Full Text Available A framework based on multibody dynamics has been developed for the static and dynamic aeroelastic analyses of flexible high aspect ratio wing aircraft subject to structural geometric nonlinearities. Multibody dynamics allows kinematic nonlinearities and nonlinear relationships in the forces definition and is an efficient and promising methodology to model high aspect ratio wings, which are known to be prone to structural nonlinear effects because of the high deflections in flight. The multibody dynamics framework developed employs quasi-steady aerodynamics strip theory and discretizes the wing as a series of rigid bodies interconnected by beam elements, representative of the stiffness distribution, which can undergo arbitrarily large displacements and rotations. The method is applied to a flexible high aspect ratio wing commercial aircraft and both trim and gust response analyses are performed in order to calculate flight loads. These results are then compared to those obtained with the standard linear aeroelastic approach provided by the Finite Element Solver Nastran. Nonlinear effects come into play mainly because of the need of taking into account the large deflections of the wing for flight loads computation and of considering the aerodynamic forces as follower forces.

  10. Aeroservoelastic model based active control for large civil aircraft


    A modeling and control approach for an advanced configured large civil aircraft with aeroservoelasticity via the LQG method and control allocation is presented.Mathematical models and implementation issues for the multi-input/multi-output(MIMO) aeroservoelastic system simulation developed for a flexible wing with multi control surfaces are described.A fuzzy logic based optimization approach is employed to solve the constrained control allocation problem via intelligently adjusting the components of output vector and find a proper vector in the attainable moment set(AMS) autonomously.The basic idea is to minimize the L2 norm of error between the desired moment and achievable moment using the designing freedom provided by redundantly allocated actuators and control surfaces.Considering the constraints of control surfaces,in order to obtain acceptable performance of aircraft such as stability and maneuverability,the fuzzy weights are updated by the learning algorithm,which makes the closed-loop system self-adaptation.Finally,an application example of flight control designing for the advanced civil aircraft is discussed as a demonstration.The studies we have performed showed that the advanced configured large civil aircraft has good performance with the proper designed control law designed via the proposed approach.The gust alleviation and flutter suppression are applied with the synergetic effects of elevator,ailerons,equivalent rudders and flaps.The results show good closed loop performance and meet the requirement of constraint of control surfaces.

  11. Estimation of droughts indicators in the Veguita zone, Cuba

    Cumbrera, Ramiro; Millán Vega, Humberto; Tarquis, Ana Maria; Alcolea Naranjo, Osvaldo


    This work has as essential objective the evaluation and analysis of the main indicators of hydrometeorology drought in Veguita, using series of daily precipitations, daily temperature and intensity of the rain. These data were contributed by the Station Agrometeorológica of Veguitas. The estimated indexes were the concentration of precipitations (CP) and the standardized index of precipitation and evapotranspiration (SPEI). The CP was calculated by means of the calculation of the index of Gini, based on the curve of Lorentz using data from 1994 until 2013. The SPEI was calculated with the software of the same name using the data from 2001 up to 2013. The main result obtained was that the precipitations in the area are concentrating, in accordance with the index of Gini and the exponential adjustment of the curve of Lorentz. Beside it, gusts dry superiors to one month were detected and the SPEI pointed out 35 months with drought, 40 humid and 81 with normal levels of rain in the last 13 years.

  12. Meteorological extremes and their impacts on forests in the czech republic

    Brázdil, Rudolf

    Meteorological extremes in the Czech Republic (CR) cause considerable damage to forest stands. The effects of such extremes has increased conspicuously in the latter half of the present century, with salvage felling due to meteorological factors accounting in some years for more than half of the total timber cut in the CR. The most important reason for this salvage felling is damage due to wind (61 %), followed by damage due to snow (16 %), drought, air pollution and ice deposits. Using data from four professionally-maintained weather stations and one special station, time series for maximum wind gusts are analysed as well as the frequencies of days with ice deposits, maximum mass of ice, heights of new snow 10 cm and, for areal precipitation series from Bohemia and Moravia, precipitation sums for the year, the summer half-year and the frequencies of occurrence of dry months. The problems of measuring these characteristics and their homogeneities are discussed. Their annual distribution and their long-term changes (fluctuations, trends) are studied. The main forest disasters of the 20th century attributable to the identified meteorological extremes are described. The analysis does not, however, permit reliable conclusions about the future behaviour of those extremes and their impact on forests under conditions of global warming.

  13. High resolution modelling results of the wind flow over Canary Islands during the meteorological situation of the extratropical storm Delta (28–30 November 2005

    J. M. Baldasano


    Full Text Available On 28–29 November 2005 an extratropical storm affected the Canary Islands causing significant damage related to high average wind speeds and intense gusts over some islands of the archipelago. Delta was the twenty-sixth tropical or subtropical storm of the 2005 Atlantic hurricane season. It represents an unusual meteorological phenomenon for that region, and its impacts were underestimated by the different operational meteorological forecasts during the previous days of the arrival of the low near Canary Islands. The aim of this study is to reproduce the local effects of the flow that were observed over the Canary Islands during the travel of the Delta storm near the region using high-resolution mesoscale meteorological simulations. The Advanced Research Weather Research & Forecasting Model (WRF-ARW is applied at 9, 3 and 1 km horizontal resolution using ECMWF forecasts as initial and boundary conditions. The high-resolution simulation will outline the main features that contributed to the high wind speeds observed in the archipelago. Variations in vertical static stability, vertical windshear and the intense synoptic winds of the southwestern part of Delta with a warm core at 850 hPa were the main characteristics that contributed to the development and amplification of intense gravity waves while the large-scale flow interacted with the complex topography of the islands.




    INTERNAL RAGATTE - BEST EVER ! If you missed Internal Regatta III on Sunday 11 July, you missed one of the best we can recall! The winds were about perfect, fairly stable Bf 2 with periodic gusts higher and the resulting capsizes to keep crews concentrating. It was extremely hot but we ran the usual three heats for keelboats and a record four for dinghies, catamarans - where there was another record, surely: a total of 11 boats in that class, of which three privately owned by members. And a final record: we calculate five boats were competing in their first-ever regatta. Results on the webpage. Surprisingly for those who remember regattas of a couple of years back, only three keelboats competed, so there would have been plenty of scope for less experienced members to come along regardless and probably find themselves a place. It is also noteworthy that the keelboat winner was Andrea Messina with an - ummm, may I say - less experienced crew himself! We hope this win bodes well for his forthcoming Transl&am...

  15. Sliding Mode Control of the X-33 with an Engine Failure

    Shtessel, Yuri B.; Hall, Charles E.


    Ascent flight control of the X-3 is performed using two XRS-2200 linear aerospike engines. in addition to aerosurfaces. The baseline control algorithms are PID with gain scheduling. Flight control using an innovative method. Sliding Mode Control. is presented for nominal and engine failed modes of flight. An easy to implement, robust controller. requiring no reconfiguration or gain scheduling is demonstrated through high fidelity flight simulations. The proposed sliding mode controller utilizes a two-loop structure and provides robust. de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of engine failure, bounded external disturbances (wind gusts) and uncertain matrix of inertia. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues. Conditions that restrict engine failures to robustness domain of the sliding mode controller are derived. Overall stability of a two-loop flight control system is assessed. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in the presence of external disturbances and vehicle inertia uncertainties, as well as the single engine failed case. The designed robust controller will significantly reduce the time and cost associated with flying new trajectory profiles or orbits, with new payloads, and with modified vehicles

  16. Linear and nonlinear models in wind resource assessment and wind turbine micro-siting in complex terrain

    Palma, J.M.L.M. [CEsA, Research Centre for Wind Energy and Atmospheric Flows, FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal); Castro, F.A. [CEsA, Research Centre for Wind Energy and Atmospheric Flows, ISEP, Instituto Superior de Engenharia do Porto, Rua Dr. Antonio Bernardino de Almeida 431, 4200-072 Porto (Portugal); Ribeiro, L.F. [CEsA, Research Centre for Wind Energy and Atmospheric Flows, IPB, Instituto Politecnico de Braganca, Campus de Santa Apolonia - Apartado 1038, 5301-854 Braganca (Portugal); Rodrigues, A.H.; Pinto, A.P. [CEsA, Research Centre for Wind Energy and Atmospheric Flows, INEGI, Instituto de Engenharia Mecanica e Gestao Industrial, Rua Dr. Roberto Frias s/n, 4200-465 Porto (Portugal)


    The current trend of increasing the electricity production from wind energy has led to the installation of wind farms in areas of greater orographic complexity, raising doubts on the use of simple, linear, mathematical models of the fluid flow equations, so common in the wind energy engineering. The present study shows how conventional techniques, linear models and cup anemometers, can be combined with flow simulation by computational fluid dynamics techniques (nonlinear models) and measurements by sonic anemometers, and discuss their relative merits in the characterisation of the wind over a coastal region - a cliff over the sea. The computational fluid dynamic techniques were particularly useful, providing a global view of the wind flow over the cliff and enabling the identification of separated flow regions, clearly unsuitable for installation of wind turbines. These locations display a pulsating flow, with periods between 1 and 7 min, in agreement with sonic anemometer measurements, and both a turbulence intensity and a gust factor well above the wind turbine design conditions. (author)

  17. Mesoscale dynamics, structure and predictability of a severe Adriatic bora case

    Belusic, D.; Klaic, Z.B. [Andrija Mohorovicic Geophysical Inst., Univ. of Zagreb (Croatia)


    The dynamics, structure and temporal evolution of a severe Adriatic bora, which occurred during 14 and 15 November 2004 was inspected. Numerical simulation of the investigated episode was performed by the mesoscale model MM5. The model was validated against radiosonde data and wind data from one automatic meteorological station and three ultrasonic anemometers. Two anemometers where located in the region extremely favorable for the bora occurrence (Senj and Vratnik Pass), while the third one was placed in the mainland (Zagreb-Horvatovac). The model reproduced well the onset and the strength of the investigated bora, as well as the establishment of bora-induced potential vorticity (PV) banners. On the other hand, surface turbulent kinetic energy (TKE) was poorly predicted. Inspection of gap wind characteristics indicated the absence of strong dissipation in the flow through a mountain pass, which gives rise to a horizontally elongated jet. Appearance of wave breaking in the lee of a mountain peak leads to the creation of a mountain wake. Shear lines between individual jets and wakes created in this way are then responsible for the generation of PV banners. Also, the ability of the model to predict hourly wind gusts was validated using a recently developed method. (orig.)

  18. Detailed design of a Ride Quality Augmentation System for commuter aircraft

    Suikat, Reiner; Donaldson, Kent E.; Downing, David R.


    The design of a Ride Quality Augmentation System (RQAS) for commuter aircraft is documented. The RQAS is designed for a Cessna 402B, an 8 passenger prop twin representative to this class of aircraft. The purpose of the RQAS is the reduction of vertical and lateral accelerations of the aircraft due to atmospheric turbulence by the application of active control. The detailed design of the hardware (the aircraft modifications, the Ride Quality Instrumentation System (RQIS), and the required computer software) is examined. The aircraft modifications, consisting of the dedicated control surfaces and the hydraulic actuation system, were designed at Cessna Aircraft by Kansas University-Flight Research Laboratory. The instrumentation system, which consist of the sensor package, the flight computer, a Data Acquisition System, and the pilot and test engineer control panels, was designed by NASA-Langley. The overall system design and the design of the software, both for flight control algorithms and ground system checkout are detailed. The system performance is predicted from linear simulation results and from power spectral densities of the aircraft response to a Dryden gust. The results indicate that both accelerations are possible.

  19. Plasma Aerodynamic Control Effectors for Improved Wind Turbine Performance

    Mehul P. Patel; Srikanth Vasudevan; Robert C. Nelson; Thomas C. Corke


    Orbital Research Inc is developing an innovative Plasma Aerodynamic Control Effectors (PACE) technology for improved performance of wind turbines. The PACE system is aimed towards the design of "smart" rotor blades to enhance energy capture and reduce aerodynamic loading and noise using flow-control. The PACE system will provide ability to change aerodynamic loads and pitch distribution across the wind turbine blade without any moving surfaces. Additional benefits of the PACE system include reduced blade structure weight and complexity that should translate into a substantially reduced initial cost. During the Phase I program, the ORI-UND Team demonstrated (proof-of-concept) performance improvements on select rotor blade designs using PACE concepts. Control of both 2-D and 3-D flows were demonstrated. An analytical study was conducted to estimate control requirements for the PACE system to maintain control during wind gusts. Finally, independent laboratory experiments were conducted to identify promising dielectric materials for the plasma actuator, and to examine environmental effects (water and dust) on the plasma actuator operation. The proposed PACE system will be capable of capturing additional energy, and reducing aerodynamic loading and noise on wind turbines. Supplementary benefits from the PACE system include reduced blade structure weight and complexity that translates into reduced initial capital costs.

  20. Regression Model to Predict Global Solar Irradiance in Malaysia

    Hairuniza Ahmed Kutty


    Full Text Available A novel regression model is developed to estimate the monthly global solar irradiance in Malaysia. The model is developed based on different available meteorological parameters, including temperature, cloud cover, rain precipitate, relative humidity, wind speed, pressure, and gust speed, by implementing regression analysis. This paper reports on the details of the analysis of the effect of each prediction parameter to identify the parameters that are relevant to estimating global solar irradiance. In addition, the proposed model is compared in terms of the root mean square error (RMSE, mean bias error (MBE, and the coefficient of determination (R2 with other models available from literature studies. Seven models based on single parameters (PM1 to PM7 and five multiple-parameter models (PM7 to PM12 are proposed. The new models perform well, with RMSE ranging from 0.429% to 1.774%, R2 ranging from 0.942 to 0.992, and MBE ranging from −0.1571% to 0.6025%. In general, cloud cover significantly affects the estimation of global solar irradiance. However, cloud cover in Malaysia lacks sufficient influence when included into multiple-parameter models although it performs fairly well in single-parameter prediction models.

  1. Solution to non-steady two-dimensional hydrofoil problems by using a simple panel method; Kantanna panel ho ni yoru hiteijo nijigen`yoku mondai no kaiho

    Maita, S.; Ando, J.; Nakatake, K. [Kyushu University, Fukuoka (Japan). Faculty of Engineering


    A simple panel method, the source and quasi continuous vortex lattice method (SQCM) was expanded to two-dimensional non-steady hydrofoil problems. Discussions were given on the results of calculations on two-dimensional hydrofoils making a simple non-steady motion. In calculating hydrofoils which move suddenly from a still state with angle of elevation {alpha} at a velocity U, the following results were obtained: the time differential item in a pressure equation gives a considerably strong effect on lifting power; and the lifting power converges to a steady state with lapse of time, and the lifting power coefficient in that state shows that the lifting power increases as hydrofoil thickness increases. This result agrees with the hydrofoil thickness effect in the two-dimensional steady problem, proving the reasonability of this calculation method. In the calculations of time history of the lifting power acting on hydrofoils passing a sinusoidal gust and hydrofoils in a pitching motion, the calculated values from the SQCM were found to approach analysis solution to thin hydrofoils as the hydrofoil thickness becomes thinner for both cases. This result also proves the result of calculations on non-steady state by using the SQCM reasonable. 11 refs., 10 figs.

  2. Simulation of the extreme waves generated by typhoon Bolaven (1215) in the East China Sea and Yellow Sea

    JUN Ki Cheon; JEONG Weon Mu; CHOI Jin Yong; PARK Kwang Soon; JUNG Kyung Tae; KIM Mee Kyung; CHAE Jang Won; QIAO Fangli


    Record-breaking high waves occurred during the passage of the typhoon Bolaven (1215) (TYB) in the East China Sea (ECS) and Yellow Sea (YS) although its intensity did not reach the level of a super typhoon. Winds and directional wave measurements were made using a range of in-situ instruments mounted on an ocean tower and buoys. In order to understand how such high waves with long duration occurred, analyses have been made through measurement and numerical simulations. TYB winds were generated using the TC96 typhoon wind model with the best track data calibrated with the measurements. And then the wind fields were blended with the reanalyzed synoptic-scale wind fields for a wave model. Wave fields were simulated using WAM4.5 with adjustment ofCd for gust of winds and bottom friction for the study area. Thus the accuracy of simulations is considerably enhanced, and the computed results are also in better agreement with measured data than before. It is found that the extremely high waves evolved as a result of the superposition of distant large swells and high wind seas generated by strong winds from the front/right quadrant of the typhoon track. As the typhoon moved at a speed a little slower than the dominant wave group velocity in a consistent direction for two days, the wave growth was significantly enhanced by strong wind input in an extended fetch and non-linear interaction.

  3. Broadband radio spectral observations of the solar eclipse on 2008-08-01 and its implications on the quiet Sun atmospheric model

    TAN BaoLin; CHEN LinJie; JI GuoShu; YAN YiHua; ZHANG Yin; TAN ChengMin; HUANG Jing; LIU YuYing; FU QiJun; CHEN ZhiJun; LIU Fei


    Based on the joint-observations of the radio broadband spectral emissions of the solar eclipse on Au-gust 1, 2008 at Jiuquan (total eclipse) and Huairou (partial eclipse) at the frequencies of 2.00-5.60 GHz (Jiuquan), 2.60-3.80 GHz (Chinese solar broadband radiospectrometer, SBRS/Huairou), and 5.20-7.60 GHz (SBRS/Huairou), the authors assemble a successive series of broadband spectra with a frequency of 2.60-7.60 GHz to observe the solar eclipse synchronously. This is the first attempt to analyze the solar eclipse radio emission under the two telescopes located at different places with broadband frequencies in the periods of total and partial eclipses. With these analyses, the authors made a semiempirical model of the coronal plasma density of the quiet Sun, which can be expressed as n_e≌1.42×10~9(r~(-2)+1.93r~(-5)) (cm~(-3)), in the space range of r=1.039-1.212 R_⊙, and made a comparison with the classic model.

  4. The support systems of unique high-rise buildings

    Shumeyko Victor


    Full Text Available Tall buildings and skyscrapers perceive significant vertical loads and, moreover, have to resist large lateral effects which form strong gusts of wind and seismic events. In the world for the high-rise buildings with the nuclei of the stiffness are using streamers – outriggers, which connect the external column and the core form the support system and resist lateral loads. High-rise buildings construction grows promptly around the world and causes new problems which shall be solved on the basis of the modern constructive opportunities, by means of exact engineering assessment. Systems of outrigers and belts are very important in the modern engineering, because they provide effective control over side shifts of a building. They play an important role in high-rise unique buildings constructions, being a link between the central kernel and outer columns. The article deals with the design scheme of conventional conveyor of belts and outriggers – bandages, explores their applications, advantages and disadvantages of various options, problems with their design. Presented material enables the design of unique high-rise buildings to choose the most optimal design solution.

  5. Analytical and Experimental Evaluation of Digital Control Systems for the Semi-Span Super-Sonic Transport (S4T) Wind Tunnel Model

    Wieseman, Carol D.; Christhilf, David; Perry, Boyd, III


    An important objective of the Semi-Span Super-Sonic Transport (S4T) wind tunnel model program was the demonstration of Flutter Suppression (FS), Gust Load Alleviation (GLA), and Ride Quality Enhancement (RQE). It was critical to evaluate the stability and robustness of these control laws analytically before testing them and experimentally while testing them to ensure safety of the model and the wind tunnel. MATLAB based software was applied to evaluate the performance of closed-loop systems in terms of stability and robustness. Existing software tools were extended to use analytical representations of the S4T and the control laws to analyze and evaluate the control laws prior to testing. Lessons were learned about the complex windtunnel model and experimental testing. The open-loop flutter boundary was determined from the closed-loop systems. A MATLAB/Simulink Simulation developed under the program is available for future work to improve the CPE process. This paper is one of a series of that comprise a special session, which summarizes the S4T wind-tunnel program.

  6. Augmented Adaptive Control of a Wind Turbine in the Presence of Structural Modes

    Frost, Susan A.; Balas, Mark J.; Wright, Alan D.


    Wind turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, potentially causing component fatigue and failure. Two key technology drivers for turbine manufacturers are increasing turbine up time and reducing maintenance costs. Since the trend in wind turbine design is towards larger, more flexible turbines with lower frequency structural modes, manufacturers will want to develop methods to operate in the presence of these modes. Accurate models of the dynamic characteristics of new wind turbines are often not available due to the complexity and expense of the modeling task, making wind turbines ideally suited to adaptive control. In this paper, we develop theory for adaptive control with rejection of disturbances in the presence of modes that inhibit the controller. We use this method to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the interference of certain structural modes in feedback. The control objective is accomplished by collectively pitching the turbine blades. The adaptive pitch controller for Region 3 is compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller.

  7. Incorporation of SemiSpan SuperSonic Transport (S4T) Aeroservoelastic Models into SAREC-ASV Simulation

    Christhilf, David M.; Pototzky, Anthony S.; Stevens, William L.


    The Simulink-based Simulation Architecture for Evaluating Controls for Aerospace Vehicles (SAREC-ASV) was modified to incorporate linear models representing aeroservoelastic characteristics of the SemiSpan SuperSonic Transport (S4T) wind-tunnel model. The S4T planform is for a Technology Concept Aircraft (TCA) design from the 1990s. The model has three control surfaces and is instrumented with accelerometers and strain gauges. Control laws developed for wind-tunnel testing for Ride Quality Enhancement, Gust Load Alleviation, and Flutter Suppression System functions were implemented in the simulation. The simulation models open- and closed-loop response to turbulence and to control excitation. It provides time histories for closed-loop stable conditions above the open-loop flutter boundary. The simulation is useful for assessing the potential impact of closed-loop control rate and position saturation. It also provides a means to assess fidelity of system identification procedures by providing time histories for a known plant model, with and without unmeasured turbulence as a disturbance. Sets of linear models representing different Mach number and dynamic pressure conditions were implemented as MATLAB Linear Time Invariant (LTI) objects. Configuration changes were implemented by selecting which LTI object to use in a Simulink template block. A limited comparison of simulation versus wind-tunnel results is shown.

  8. Model Predictive Wind Turbine Control with Move-Blocking Strategy for Load Alleviation and Power Leveling

    Jassmann, U.; Dickler, S.; Zierath, J.; Hakenberg, M.; Abel, D.


    This contribution presents a Model Predictive Controller (MPC) with moveblocking strategy for combined power leveling and load alleviation in wind turbine operation with a focus on extreme loads. The controller is designed for a 3 MW wind turbine developed by W2E Wind to Energy GmbH and compared to a baseline controller, using a classic control scheme, which currently operates the wind turbine. All simulations are carried out with a detailed multibody simulation turbine model implemented in alaska/Wind. The performance of the two different controllers is compared using a 50-year Extreme Operation Gust event, since it is one of the main design drivers for the wind turbine considered in this work. The implemented MPC is able to level electrical output power and reduce mechanical loads at the same time. Without de-rating the achieved control results, a move-blocking strategy is utilized and allowed to reduce the computational burden of the MPC by more than 50% compared to a baseline MPC implementation. This even allows to run the MPC on a state of the art Programmable Logic Controller.

  9. Modeling the transient aerodynamic effects during the motion of a flexible trailing edge

    Wolff, T.; Seume, J. R.


    Wind turbine blades have been becoming longer and more slender during the last few decades. The longer lever arm results in higher stresses at the blade root. Hence, the unsteady loads induced by turbulence, gust, or wind shear increase. One promising way to control these loads is to use flexible trailing edges near the blade tip. The unsteady effects which appear during the motion of a flexible trailing edge must be considered for the load calculation during the design process because of their high influence on aeroelastic effects and hence on the fatigue loads. This is not yet possible in most of the wind turbine simulation environments. Consequently, an empirical model is developed in the present study which accounts for unsteady effects during the motion of the trailing edge. The model is based on Fourier analyses of results generated with Reynolds-Averaged Navier-Stokes (RANS) simulations of a typical thin airfoil with a deformable trailing edge. The validation showed that the model fits Computational Fluid Dynamics (CFD) results simulated with a random time series of the deflection angle.

  10. Danos físicos em estufas plásticas causados pelo vento em Santa Maria, RS Plastic greenhouses damaged by wind in Santa Maria, RS. Case report

    Nereu Augusto Streck


    Full Text Available Foram observados danos físicos causados por rajadas de vento ocorridos na madrugada do dia 19/05/97 no plástico das estufas localizadas no Campus da Universidade Federal de Santa Maria. Os valores de intensidade e direção das rajadas máximas do vento foram registradas em um anemográfo universal tipo IH 1023 a 10m de altura, instalado a aproximadamente 100m ao sul das estufas. Os danos ocorreram quando a velocidade das rajadas máximas ultrapassou 20m s-1 (72km h-1Plastic greenhouses located at the Federal University of Santa Maria, Rio Grande do Sul State, Brazil were damaged by wind on May 19th, 1997. Wind speed and direction at 10m height were measured at the Climatological Station located approximatly 100m from the greenhouses. The damage in the greenhouses occured when the maximum gusts reached up speed higher than 20m s-1 (72km h-1.

  11. Validity of the assumption of Gaussian turbulence; Gyldighed af antagelsen om Gaussisk turbulence

    Nielsen, M.; Hansen, K.S.; Juul Pedersen, B.


    Wind turbines are designed to withstand the impact of turbulent winds, which fluctuations usually are assumed of Gaussian probability distribution. Based on a large number of measurements from many sites, this seems a reasonable assumption in flat homogeneous terrain whereas it may fail in complex terrain. At these sites the wind speed often has a skew distribution with more frequent lulls than gusts. In order to simulate aerodynamic loads, a numerical turbulence simulation method was developed and implemented. This method may simulate multiple time series of variable not necessarily Gaussian distribution without distortion of the spectral distribution or spatial coherence. The simulated time series were used as input to the dynamic-response simulation program Vestas Turbine Simulator (VTS). In this way we simulated the dynamic response of systems exposed to turbulence of either Gaussian or extreme, yet realistic, non-Gaussian probability distribution. Certain loads on turbines with active pitch regulation were enhanced by up to 15% compared to pure Gaussian turbulence. It should, however, be said that the undesired effect depends on the dynamic system, and it might be mitigated by optimisation of the wind turbine regulation system after local turbulence characteristics. (au)

  12. Dalt del tren

    Jaume Subirana


    Full Text Available Ens consta que la saviesa popular hi toca més del que a aquest temps d’enquestes, telèfons mòbils i targetes de crèdit li ve de gust admetre, per això em fa gràcia, en veure la pausada però continuada intrusió de la cultura catalana a Internet, recordar les cançons de quan era petit: “Dalt del tren, tots anem-hi dalt del tren, hi ha lloc per tota la gent”, dèiem, i “El tren pinxo de Banyoles és el més bonic que hi ha, ple de llaunes i cassoles i barrets de capellà”. I resulta que per una vegada a la vida hem pujat, efectivament, dalt del tren que passava per l’estació de Catalunya i en cinc anys hem passat de gairebé res a prou pàgines amb un contingut, a més, apreciable i, sobretot, a un petit teixit de persones i institucions que han entès la importància de la revolució comunicativa que Internet representa i que hi teixeixen i projecten webs amb el convenciment dels conversos.

  13. Development of a Smooth Trajectory Maneuver Method to Accommodate the Ares I Flight Control Constraints

    Pinson, Robin M.; Schmitt, Terri L.; Hanson, John M.


    Six degree-of-freedom (DOF) launch vehicle trajectories are designed to follow an optimized 3-DOF reference trajectory. A vehicle has a finite amount of control power that it can allocate to performing maneuvers. Therefore, the 3-DOF trajectory must be designed to refrain from using 100% of the allowable control capability to perform maneuvers, saving control power for handling off-nominal conditions, wind gusts and other perturbations. During the Ares I trajectory analysis, two maneuvers were found to be hard for the control system to implement; a roll maneuver prior to the gravity turn and an angle of attack maneuver immediately after the J-2X engine start-up. It was decided to develop an approach for creating smooth maneuvers in the optimized reference trajectories that accounts for the thrust available from the engines. A feature of this method is that no additional angular velocity in the direction of the maneuver has been added to the vehicle after the maneuver completion. This paper discusses the equations behind these new maneuvers and their implementation into the Ares I trajectory design cycle. Also discussed is a possible extension to adjusting closed-loop guidance.

  14. Nonlinear switched models for control of unsteady forces on a rapidly pitching airfoil

    Dawson, Scott; Brunton, Steven; Rowley, Clarence


    The unsteady aerodynamic forces incident on a pitching flat plate airfoil at a Reynolds number of 100 are investigated through direct numerical simulation. Linear state-space models, identified from impulse response data via the eigensystem realization algorithm, are used to accurately track rapid changes in lift coefficient through either feedback or feedforward control, even in the presence of gust disturbances. We develop a technique to project between states of linear models obtained at different angles of attack using primal and pseudo-adjoint balanced POD modes. This allows for the formation of a nonlinear switched model that is accurate over a wide range of angles of attack, in both pre- and post-stall regimes. We additionally investigate phenomena that are not captured by linear models, such as an increase in mean lift that occurs when vortex shedding frequencies are excited. The effect of changing the pitch axis is also investigated, where it is found that pitching aft of the mid-chord results in right half plane zeros that increase the difficulty of the control problem. This work was supported by AFOSR grant FA9550-12-1-0075.

  15. Modeling State-Space Aeroelastic Systems Using a Simple Matrix Polynomial Approach for the Unsteady Aerodynamics

    Pototzky, Anthony S.


    A simple matrix polynomial approach is introduced for approximating unsteady aerodynamics in the s-plane and ultimately, after combining matrix polynomial coefficients with matrices defining the structure, a matrix polynomial of the flutter equations of motion (EOM) is formed. A technique of recasting the matrix-polynomial form of the flutter EOM into a first order form is also presented that can be used to determine the eigenvalues near the origin and everywhere on the complex plane. An aeroservoelastic (ASE) EOM have been generalized to include the gust terms on the right-hand side. The reasons for developing the new matrix polynomial approach are also presented, which are the following: first, the "workhorse" methods such as the NASTRAN flutter analysis lack the capability to consistently find roots near the origin, along the real axis or accurately find roots farther away from the imaginary axis of the complex plane; and, second, the existing s-plane methods, such as the Roger s s-plane approximation method as implemented in ISAC, do not always give suitable fits of some tabular data of the unsteady aerodynamics. A method available in MATLAB is introduced that will accurately fit generalized aerodynamic force (GAF) coefficients in a tabular data form into the coefficients of a matrix polynomial form. The root-locus results from the NASTRAN pknl flutter analysis, the ISAC-Roger's s-plane method and the present matrix polynomial method are presented and compared for accuracy and for the number and locations of roots.

  16. Dynamic analysis of DATE5 based on the physically realistic environmental disturbances

    Wang, Hairen; Qian, Yuan; Lou, Zheng; Zuo, Yingxi; Yang, Ji; Kaercher, Hans


    The observation bands of the 5 meter Dome A Terahertz Explorer (DATE5) are primarily over the wavelength of 350 and 200 μm. However, the pointing performance of DATE5 is affected by the unsteady wind, which either acts directly on the telescope structure or transmits through the ice and foundation. According to the above performance requirements of DATE5, the pointing error caused by the wind disturbance must be less than 2 arcsec. The main influence of the disturbances acting on the telescope is forces and torques due to wind gusts. Alternating forces and torques cause displacements of the telescope as well as structural oscillations. Both effects lead to pointing errors and therefore have to be compensated as much as possible by the main axes servo controllers. Wind acting on the telescope can be treated as random event, whose expected values depend on the specific site. The wind velocity throughout a given time interval can be described as a randomly varying velocity superimposed upon a constant average or mean velocity. For the dynamic analysis, the two components are separated and only the fluctuating component is used. In this paper, the dynamic analysis (mode analysis and spectrum analysis) of DATE5 is carried out based on the physically realistic environmental disturbances of dome A.

  17. Environmental policies to protect pollinators: attributes and actions needed to avert climate borne crisis of oil seed agriculture in Pakistan

    A. Burhan


    Full Text Available The impact of climate change on oil seed crop is getting more and more pronounced with each passing day, resulting in reduced crop yields in Pakistan. Agriculture is the mainstay of Pakistan’s economy, however it is subjected to severe climatic vulnerabilities like floods, droughts, and changing rainfall patterns. Climate change has a marked influence on the population and distribution of pollinators. Extreme weather events can further aggravate the situation by causing high overwintering losses. Less roving pollinators, such as small beetles and ground nesting bees, may be among the most severely affected by flooding and gusts. Extreme conditions not only can disrupt the livelihoods of individual insects, but can also negatively impact entire colonies or local populations. It is recommended to take offensive measures to address these issues, otherwise the area under oil seed crops may decrease resulting in poor market stability index. Moreover, in this regard, there is desperate need to aggressively explore opportunities of capacity building and institutional strengthening to address the climate change issues in Pakistan. Through this review, it is hoped that a proactive risk assessment approach to climate change can assist the Government in making strategies against the losses of pollinator services in Pakistan.

  18. Analysis of the wind influence on the aerodynamic drag in the case of a certain emplacement of the pantograph on the electric rail vehicles

    Sorin ARSENE


    Full Text Available The wind gusts with high speed can negative affect the operation of the railway electric vehicles. These vehicles can achieve high performances, as long as the power supply is ensured, without discontinuities or interruptions in the process. This work aims at conducting an analysis regarding the wind influence with regard to the energy collector placed on the vehicle bodywork taking in account a certain positioning of the active pantograph. To this end, in a first step, the EP3 pantograph which was raised to its maximum working height was 3-D modeled. As regards the simulation, we consider the case in which the equipment is placed on the vehicle so that the angle formed by the articulation of the arms is pointing in the direction of the air flow. The simulation is carried out for different points of the angles ranging between [0o, 180o] at the relative velocity of the fluid of 0m / s, 10m / s, 20m / s and 30m / s.

  19. Feed forward control of estimated wind speed

    Van Engelen, T.G.; Van der Hooft, E.L. [ECN Wind Energy, Petten (Netherlands)


    A control structure 'feed forward of estimated wind speed' is described, as it were: 'the wind turbine rotor will be used as a wind meter'. The control structure is based on 'estimation' of wind speed as well as a non-linear compensation of a wind speed dependent pitch speed setpoint, which is optimised to maintain (stationary) rated electric power. It is required to know the rotor properties with moderate accuracy. In time domain simulations, inclusion of a feed forward of estimated wind speed control action has shown to be a powerful extension to current ECN wind turbine control structures: reduction of rotor speed variations: 0.2 rpm decreased standard deviation; improved turbine behaviour to large wind gusts; increase of energy yield of 0.9%; For reasons of simplicity and robustness, a tabular implementation approach is preferred above polynomial implementation. The resulting brief algorithm uses small sized tables, requires low hardware requirements and needs a minimum of easy interpretable parameters for design and tuning. Both stability, robustness and parametric uncertainties were observed. The addition control loop has a slightly positive effect on overall stability and robustness. Appeared offsets in the estimated wind speed value due to parameter uncertainties do not have impact on the effectuation of the wind speed feed forward loop.

  20. Army/NASA small turboshaft engine digital controls research program

    Sellers, J. F.; Baez, A. N.


    The emphasis of a program to conduct digital controls research for small turboshaft engines is on engine test evaluation of advanced control logic using a flexible microprocessor based digital control system designed specifically for research on advanced control logic. Control software is stored in programmable memory. New control algorithms may be stored in a floppy disk and loaded directly into memory. This feature facilitates comparative evaluation of different advanced control modes. The central processor in the digital control is an Intel 8086 16 bit microprocessor. Control software is programmed in assembly language. Software checkout is accomplished prior to engine test by connecting the digital control to a real time hybrid computer simulation of the engine. The engine currently installed in the facility has a hydromechanical control modified to allow electrohydraulic fuel metering and VG actuation by the digital control. Simulation results are presented which show that the modern control reduces the transient rotor speed droop caused by unanticipated load changes such as cyclic pitch or wind gust transients.

  1. Control and navigation system for a fixed-wing unmanned aerial vehicle

    Zhai, Ruiyong; Zhou, Zhaoying; Zhang, Wendong; Sang, Shengbo; Li, Pengwei


    This paper presents a flight control and navigation system for a fixed-wing unmanned aerial vehicle (UAV) with low-cost micro-electro-mechanical system (MEMS) sensors. The system is designed under the inner loop and outer loop strategy. The trajectory tracking navigation loop is the outer loop of the attitude loop, while the attitude control loop is the outer loop of the stabilization loop. The proportional-integral-derivative (PID) control was adopted for stabilization and attitude control. The three-dimensional (3D) trajectory tracking control of a UAV could be approximately divided into lateral control and longitudinal control. The longitudinal control employs traditional linear PID feedback to achieve the desired altitude of the UAV, while the lateral control uses a non-linear control method to complete the desired trajectory. The non-linear controller can automatically adapt to ground velocity change, which is usually caused by gust disturbance, thus the UAV has good wind resistance characteristics. Flight tests and survey missions were carried out with our self-developed delta fixed-wing UAV and MEMS-based autopilot to confirm the effectiveness and practicality of the proposed navigation method.

  2. An analysis of uncertainties and skill in forecasts of winter storm losses

    Pardowitz, Tobias; Osinski, Robert; Kruschke, Tim; Ulbrich, Uwe


    This paper describes an approach to derive probabilistic predictions of local winter storm damage occurrences from a global medium-range ensemble prediction system (EPS). Predictions of storm damage occurrences are subject to large uncertainty due to meteorological forecast uncertainty (typically addressed by means of ensemble predictions) and uncertainties in modelling weather impacts. The latter uncertainty arises from the fact that local vulnerabilities are not known in sufficient detail to allow for a deterministic prediction of damages, even if the forecasted gust wind speed contains no uncertainty. Thus, to estimate the damage model uncertainty, a statistical model based on logistic regression analysis is employed, relating meteorological analyses to historical damage records. A quantification of the two individual contributions (meteorological and damage model uncertainty) to the total forecast uncertainty is achieved by neglecting individual uncertainty sources and analysing resulting predictions. Results show an increase in forecast skill measured by means of a reduced Brier score if both meteorological and damage model uncertainties are taken into account. It is demonstrated that skilful predictions on district level (dividing the area of Germany into 439 administrative districts) are possible on lead times of several days. Skill is increased through the application of a proper ensemble calibration method, extending the range of lead times for which skilful damage predictions can be made.

  3. The 10-12 November 2001 Balearic Superstorm: An Assessment of Baroclinic and Diabatic Contributions Through Pv Diagnosis

    Romero, R.; Homar, V.; Ramis, C.; Alonso, S.

    From 10 to 12 November 2001 the western Mediterranean zone was affected by a hazardous cyclone. In the Balearic Islands the storm was particularly strong: wind gusts exceeded 140 km/h, heavy precipitation up to 400 mm in two days was recorded and sea waves up to 12 m reached the shoreline. Four casualties occurred, more than 100.000 trees were uprooted, many boats and coastal infrastructures were severely damaged and some crop fields were flooded. Surface and upper level weather maps suggest that the cyclone was consequence of an initial baroclinic development over north Africa and a further deepening over the western Mediterranean. Quasi- geostrophic diagnosis has been performed to study the baroclinic contribution to the cyclogenesis. A Potential Vorticity (PV) inversion technique has been applied to de- termine the role of three prominent PV positive anomalies over the region (associated with an upper level trough, a low level warm air intrusion over the Mediterranean from Africa and the latent heat release) to the cyclone intensity.

  4. Recent Advances in the Tempest UAS for In-Situ Measurements in Highly-Dynamic Environments

    Argrow, B. M.; Frew, E.; Houston, A. L.; Weiss, C.


    The spring 2010 deployment of the Tempest UAS during the VORTEX2 field campaign verified that a small UAS, supported by a customized mobile communications, command, and control (C3) architecture, could simultaneously satisfy Federal Aviation Administration (FAA) airspace requirements, and make in-situ thermodynamic measurements in supercell thunderstorms. A multi-hole airdata probe was recently integrated into the Tempest UAS airframe and verification flights were made in spring 2013 to collect in-situ wind measurements behind gust fronts produced by supercell thunderstorms in northeast Colorado. Using instantaneous aircraft attitude estimates from the autopilot, the in-situ measurements were converted to inertial wind estimates, and estimates of uncertainty in the wind measurements was examined. To date, the limited deployments of the Tempest UAS have primarily focused on addressing the engineering and regulatory requirements to conduct supercell research, and the Tempest UAS team of engineers and meteorologists is preparing for deployments with the focus on collecting targeted data for meteorological exploration and hypothesis testing. We describe the recent expansion of the operations area and altitude ceiling of the Tempest UAS, engineering issues for accurate inertial wind estimates, new concepts of operation that include the simultaneous deployment of multiple aircraft with mobile ground stations, and a brief description of our current effort to develop a capability for the Tempest UAS to perform autonomous path planning to maximize energy harvesting from the local wind field for increased endurance.

  5. Yachting club

    Yachting club


    Regattas everywhere (bis)! A fornight ago, we reported on imminent Match-Racing of the Surprises as the highlight of the season: it has now happened of course, and been written up on the Website Blog - along with the results of the Semaine du Soir of Versoix, which happened a week later, with many YCC teams competing: it is nice to report that our dinghies (either club-owned or skippered) wiped up the opposition! Sanja’s photo herewith from the Bol d’Or implies that there were some Surprises (and others) actually ahead of our Mic Mac - truth be told, there were, at different stages, but the event June 18/19 was a good regatta, if a very hard one as the wind strengths were Bf 6 with Bf7 gusts. Sanja reports that this regatta was more impressive and much harder than the SdS: skipper Thierry, on Mic Mac, did a great job, from an excellent start which kept her among the first ten Surprises for 4 hours - not bad, when they finished the regatta after ~13 hours, with 26th position out of 109 Su...

  6. Acoustic Data Processing and Transient Signal Analysis for the Hybrid Wing Body 14- by 22-Foot Subsonic Wind Tunnel Test

    Bahr, Christopher J.; Brooks, Thomas F.; Humphreys, William M.; Spalt, Taylor B.; Stead, Daniel J.


    An advanced vehicle concept, the HWB N2A-EXTE aircraft design, was tested in NASA Langley's 14- by 22-Foot Subsonic Wind Tunnel to study its acoustic characteristics for var- ious propulsion system installation and airframe con gurations. A signi cant upgrade to existing data processing systems was implemented, with a focus on portability and a re- duction in turnaround time. These requirements were met by updating codes originally written for a cluster environment and transferring them to a local workstation while en- abling GPU computing. Post-test, additional processing of the time series was required to remove transient hydrodynamic gusts from some of the microphone time series. A novel automated procedure was developed to analyze and reject contaminated blocks of data, under the assumption that the desired acoustic signal of interest was a band-limited sta- tionary random process, and of lower variance than the hydrodynamic contamination. The procedure is shown to successfully identify and remove contaminated blocks of data and retain the desired acoustic signal. Additional corrections to the data, mainly background subtraction, shear layer refraction calculations, atmospheric attenuation and microphone directivity corrections, were all necessary for initial analysis and noise assessments. These were implemented for the post-processing of spectral data, and are shown to behave as expected.

  7. An analytical approach for predicting the energy capture and conversion by impulsively-excited bistable vibration energy harvesters

    Harne, R. L.; Zhang, Chunlin; Li, Bing; Wang, K. W.


    Impulsive energies are abundant throughout the natural and built environments, for instance as stimulated by wind gusts, foot-steps, or vehicle-road interactions. In the interest of maximizing the sustainability of society's technological developments, one idea is to capture these high-amplitude and abrupt energies and convert them into usable electrical power such as for sensors which otherwise rely on less sustainable power supplies. In this spirit, the considerable sensitivity to impulse-type events previously uncovered for bistable oscillators has motivated recent experimental and numerical studies on the power generation performance of bistable vibration energy harvesters. To lead to an effective and efficient predictive tool and design guide, this research develops a new analytical approach to estimate the electroelastic response and power generation of a bistable energy harvester when excited by an impulse. Comparison with values determined by direct simulation of the governing equations shows that the analytically predicted net converted energies are very accurate for a wide range of impulse strengths. Extensive experimental investigations are undertaken to validate the analytical approach and it is seen that the predicted estimates of the impulsive energy conversion are in excellent agreement with the measurements, and the detailed structural dynamics are correctly reproduced. As a result, the analytical approach represents a significant leap forward in the understanding of how to effectively leverage bistable structures as energy harvesting devices and introduces new means to elucidate the transient and far-from-equilibrium dynamics of nonlinear systems more generally.

  8. Smac–Fdi: A Single Model Active Fault Detection and Isolation System for Unmanned Aircraft

    Ducard Guillaume J.J.


    Full Text Available This article presents a single model active fault detection and isolation system (SMAC-FDI which is designed to efficiently detect and isolate a faulty actuator in a system, such as a small (unmanned aircraft. This FDI system is based on a single and simple aerodynamic model of an aircraft in order to generate some residuals, as soon as an actuator fault occurs. These residuals are used to trigger an active strategy based on artificial exciting signals that searches within the residuals for the signature of an actuator fault. Fault isolation is carried out through an innovative mechanism that does not use the previous residuals but the actuator control signals directly. In addition, the paper presents a complete parameter-tuning strategy for this FDI system. The novel concepts are backed-up by simulations of a small unmanned aircraft experiencing successive actuator failures. The robustness of the SMAC-FDI method is tested in the presence of model uncertainties, realistic sensor noise and wind gusts. Finally, the paper concludes with a discussion on the computational efficiency of the method and its ability to run on small microcontrollers.

  9. Centrifuge modelling of the pushover failure of an electricity transmission tower

    Richards, D.J. [Southampton Univ. (United Kingdom). School of Civil Engineering and the Environment; White, D.J. [Western Australia Univ., Crawley, WA (Australia). Centre for Offshore Foundation Systems, Faculty of Engineering, Computing and Mathematics


    The foundation systems of broad-based lattice power transmission towers must be designed to resist uplift, lateral and downward forces arising from the tower's weight, and tension within the conductor wires and wind loadings. This study investigated foundation failure mechanisms during the rapid horizontal pushover of a power transmission tower. The centrifuge model tests were designed to simulate a wind gust loading or broken transmission line response. The tower was supported on 4 pad foundations set in clay and backfilled with sand. The loads at each foundation were measured during fast and flow pushover. The influence of tensile resistance mobilized at the underside of the footings was investigated. The measured performance of the tower footings showed good agreement with results obtained from a series of tests conducted to measure a single footing subjected to vertical loading. Tower response was back-analyzed as a simple push-pull model. The calculated uplift capacity of the footing backfill showed good agreement with the observed response of tower footings subjected to slow pushover. The additional capacity mobilized during fast pushover was caused by tensile resistance created by the reverse bearing capacity beneath the base of the footings. 30 refs., 3 tabs., 11 figs.

  10. A new low-turbulence wind tunnel for animal and small vehicle flight experiments

    Quinn, Daniel B.; Watts, Anthony; Nagle, Tony; Lentink, David


    Our understanding of animal flight benefits greatly from specialized wind tunnels designed for flying animals. Existing facilities can simulate laminar flow during straight, ascending and descending flight, as well as at different altitudes. However, the atmosphere in which animals fly is even more complex. Flow can be laminar and quiet at high altitudes but highly turbulent near the ground, and gusts can rapidly change wind speed. To study flight in both laminar and turbulent environments, a multi-purpose wind tunnel for studying animal and small vehicle flight was built at Stanford University. The tunnel is closed-circuit and can produce airspeeds up to 50 m s-1 in a rectangular test section that is 1.0 m wide, 0.82 m tall and 1.73 m long. Seamless honeycomb and screens in the airline together with a carefully designed contraction reduce centreline turbulence intensities to less than or equal to 0.030% at all operating speeds. A large diameter fan and specialized acoustic treatment allow the tunnel to operate at low noise levels of 76.4 dB at 20 m s-1. To simulate high turbulence, an active turbulence grid can increase turbulence intensities up to 45%. Finally, an open jet configuration enables stereo high-speed fluoroscopy for studying musculoskeletal control in turbulent flow.

  11. Study of Model Predictive Control for Path-Following Autonomous Ground Vehicle Control under Crosswind Effect

    Fitri Yakub


    Full Text Available We present a comparative study of model predictive control approaches of two-wheel steering, four-wheel steering, and a combination of two-wheel steering with direct yaw moment control manoeuvres for path-following control in autonomous car vehicle dynamics systems. Single-track mode, based on a linearized vehicle and tire model, is used. Based on a given trajectory, we drove the vehicle at low and high forward speeds and on low and high road friction surfaces for a double-lane change scenario in order to follow the desired trajectory as close as possible while rejecting the effects of wind gusts. We compared the controller based on both simple and complex bicycle models without and with the roll vehicle dynamics for different types of model predictive control manoeuvres. The simulation result showed that the model predictive control gave a better performance in terms of robustness for both forward speeds and road surface variation in autonomous path-following control. It also demonstrated that model predictive control is useful to maintain vehicle stability along the desired path and has an ability to eliminate the crosswind effect.

  12. The average output power of a wind turbine in a turbulent wind

    Rosen, A.; Sheinman, Y. (Faculty of Aerospace Engineering, Technion, Israel Institute of Technology, Haifa (Israel))


    Turbulence has an important influence on the average output power of a wind turbine taken over a certain period of time. The wind dynamics is coupled to the turbine dynamic characteristics and results in a fairly complicated behavior. Thus, the common 'static' model of calculating the average power, which is based on the turbine power curve and the average wind speed, may result in increasing errors. This paper presents three different models for calculating the average output power, taking into account the dynamic characteristics of the phenomenon. These models include direct time integration using accurate wind data and a detailed dynamic model of the turbine, a quasi-steady approach which is much simpler to apply and takes into account the wind dynamics, and an improved efficient model that also includes the influence of the dynamic characteristics of the turbine. The last improved model is based on a study of the turbine response to a sinusoidal gust. All models are compared with field measurements in order to study their accuracy. The comparison exhibits the importance of including all the dynamic effects in the calculations

  13. The Analysis of the Aerodynamic Character and Structural Response of Large-Scale Wind Turbine Blades

    Jie Zhu


    Full Text Available A process of detailed CFD and structural numerical simulations of the 1.5 MW horizontal axis wind turbine (HAWT blade is present. The main goal is to help advance the use of computer-aided simulation methods in the field of design and development of HAWT-blades. After an in-depth study of the aerodynamic configuration and materials of the blade, 3-D mapping software is utilized to reconstruct the high fidelity geometry, and then the geometry is imported into CFD and structure finite element analysis (FEA software for completely simulation calculation. This research process shows that the CFD results compare well with the professional wind turbine design and certification software, GH-Bladed. Also, the modal analysis with finite element method (FEM predicts well compared with experiment tests on a stationary blade. For extreme wind loads case that by considering a 50-year extreme gust simulated in CFD are unidirectional coupled to the FE-model, the results indicate that the maximum deflection of the blade tip is less than the distance between the blade tip (the point of maximum deflection and the tower, the material of the blade provides enough resistance to the peak stresses the occur at the conjunction of shear webs and center spar cap. Buckling analysis is also included in the study.

  14. Measured effect of wind generation on the fuel consumption of an isolated diesel power system

    Stiller, P. H.; Scott, G. W.; Shaltens, R. K.


    The Block Island Power Company (BIPCO), on Block Island, Rhode Island, operates an isolated electric power system consisting of diesel generation and an experimental wind turbine. The 150-kW wind turbine, designated MOD-OA by the U.S. Department of Energy is typically operated in parallel with two diesel generators to serve an average winter load of 350 kW. Wind generation serves up to 60 percent of the system demand depending on wind speed and total system load. Results of diesel fuel consumption measurements are given for the diesel units operated in parallel with the wind turbine and again without the wind turbine. The fuel consumption data are used to calculate the amount of fuel displaced by wind energy. Results indicate that the wind turbine displaced 25,700 lbs. of the diesel fuel during the test period, representing a calculated reduction in fuel consumption of 6.7 percent while generating 11 percent of the total electric energy. The amount of displaced fuel depends on operating conditions and system load. It is also shown that diesel engine throttle activity resulting from wind gusts which rapidly change the wind turbine output do not significantly influence fuel consumption.

  15. An Algorithm on Convective Weather Potential in the Early Rainy Season over the Pearl River Delta in China


    This paper describes the procedure and methodology to formulate the convective weather potential (CWP) algorithm. The data used in the development of the algorithm are the radar echoes at 0.5° elevation from Guangzhou Doppler Radar Station, surface observations from automatic weather stations (AWS) and outputs of numeric weather prediction (NWP) models. The procedure to develop the CWP algorithm consists of two steps: (1) identification of thunderstorm cells in accordance with specified statistical criteria;and (2) development of the algorithm based on multiple linear regression. The thunderstorm cells were automatically identified by radar echoes with intensity greater than or equal to 50 dB(Z) and of an area over 64 square kilometers. These cells are generally related to severe convective weather occurrences such as thunderstorm wind gusts, hail and tornados. In the development of the CWP algorithm, both echoand environment-based predictors are used. The predictand is the probability of a thunderstorm cell to generate severe convective weather events. The predictor-predictand relationship is established through a stepwise multiple linear regression approach. Verification with an independent dataset shows that the CWP algorithm is skillful in detecting thunderstorm-related severe convective weather occurrences in the Pearl River Delta (PRD) region of South China. An example of a nowcasting case for a thunderstorm process is illustrated.

  16. Derecho-like event in Bulgaria on 20 July 2011

    Gospodinov, Ilian; Dimitrova, Tsvetelina; Bocheva, Lilia; Simeonov, Petio; Dimitrov, Rumen


    In this work we analyze the development of a severe-convective-storm system in northwestern Bulgaria on 20 July 2011 which exhibited derecho-like characteristics. Prior to this event, a derecho had never been documented in Bulgaria. The convective system was associated with a cold front. We present a synoptic-scale analysis of the evolution of the cold front and an overview of the wind and the damage that has occurred in the region with the strongest impact. The convective system consisted of two multi-cell thunderstorms that are analyzed in some detail, based on radar data. The two storms merged and the convective system evolved into a bow-shape reflectivity structure with two rear inflow notches. The analysis of the radar data revealed cloud top heights of 17 km, with the formation of а bounded weak echo region, a maximum radar reflectivity factor of 63 dBZ, and wind speeds above 30 m/s. The field investigation revealed patterns in the damaged crops typical of strong wind gusts.

  17. A Mediterranean derecho: Catalonia (Spain), 17th August 2003

    López, J. Manuel


    At approximately 6:10 UTC in the morning of 17th August 2003, a squall line developed over south Catalonia (the northeast region of Spain). During the next 9 h, the squall moved rapidly northeast and crossed Catalonia and the French regions of Languedoc-Roussillon and Province, damaging and uprooting hundreds of trees and blocking trains in the region. Wind gusts reached were recoded up to 52 m/s with evidence of F2 intensity damage. This case study shows the characteristics of a derecho (widespread convectively induced windstorm). Radar observations of the evolving squall line show signatures often correlated with damaging surface winds, including: Bow echoes, Rear inflow notches, Rear inflow jets, Medium altitude radial convergence, Narrow gradient of very marked reflectivity, Development of isolated cells ahead of the convective line, A band of convection off the northern end of the line known as a "warm advection wing". When examining the different surface observations, satellite, radar imagery and cloud-to-ground lightning data, this case shows many similarities to those investigated in the United States. The derecho is a hybrid case, but has many characteristics of warm season derechoes. This emanates from a mesoscale convective complex (MCC) moving along a quasi-stationary, low-level thermal boundary in an environment characterized by high potential instability and relatively strong mid-tropospheric winds.

  18. Hindcast experiments of the derecho in Estonia on 08 August, 2010: Modelling derecho with NWP model HARMONIE

    Toll, Velle; Männik, Aarne; Luhamaa, Andres; Rõõm, Rein


    On August 8, 2010, a derecho swept over Northern Europe, causing widespread wind damage and more than 2 million Euros in economic loss in Estonia during its most destructive stage. This paper presents a modelling study of the derecho-producing storm utilising the Hirlam Aladin Research for Mesoscale Operational Numerical Weather Prediction in Europe (HARMONIE) model. The model setup is chosen to mimic near-future, nearly kilometre-scale, operational environments in European national weather services. The model simulations are compared to remote sensing and in situ observations. The HARMONIE model is capable of reproducing the wind gust severity and precipitation intensity. Moreover, 2.5-km grid spacing is shown to be sufficient for producing a reliable signal of the severe convective storm. Storm dynamics are well simulated, including the rear inflow jet. Although the model performance is promising, a strong dependence on the initial data, a weak trailing stratiform precipitation region and an incorrect timing of the storm are identified.

  19. Predicting Flutter and Forced Response in Turbomachinery

    VanZante, Dale E.; Adamczyk, John J.; Srivastava, Rakesh; Bakhle, Milind A.; Shabbir, Aamir; Chen, Jen-Ping; Janus, J. Mark; To, Wai-Ming; Barter, John


    TURBO-AE is a computer code that enables detailed, high-fidelity modeling of aeroelastic and unsteady aerodynamic characteristics for prediction of flutter, forced response, and blade-row interaction effects in turbomachinery. Flow regimes that can be modeled include subsonic, transonic, and supersonic, with attached and/or separated flow fields. The three-dimensional Reynolds-averaged Navier-Stokes equations are solved numerically to obtain extremely accurate descriptions of unsteady flow fields in multistage turbomachinery configurations. Blade vibration is simulated by use of a dynamic-grid-deformation technique to calculate the energy exchange for determining the aerodynamic damping of vibrations of blades. The aerodynamic damping can be used to assess the stability of a blade row. TURBO-AE also calculates the unsteady blade loading attributable to such external sources of excitation as incoming gusts and blade-row interactions. These blade loadings, along with aerodynamic damping, are used to calculate the forced responses of blades to predict their fatigue lives. Phase-lagged boundary conditions based on the direct-store method are used to calculate nonzero interblade phase-angle oscillations; this practice eliminates the need to model multiple blade passages, and, hence, enables large savings in computational resources.

  20. The passage of a distorted velocity field through a cascade of airfoils

    Adamczyk, J. J.


    An analysis has been developed to predict the unsteady force and moment generated by the passage of a timewise periodic total pressure distortion through an arbitrary cascade of airfoils. The mathematical formulation of this analysis is based on the assumption that the magnitudes of the timewise fluctuations of the variables which describe the flow field are small compared to their time average values. This assumption permits the development of a linear unsteady perturbation analysis about a steady flow field. In addition to this linearization assumption the fluid medium is assumed to be incompressible and inviscid. The mathematical development begins by decomposing the velocity field surrounding an infinite cascade of airfoils into its irrotational and rotational components. The rotational component is associated with an upstream unsteady total pressure distortion and is defined in terms of the vorticity field associated with the distortion pattern. The irrotational component is further decomposed into a steady and unsteady part. A combined analytical and numerical procedure has been developed to solve the field equations which govern the rotational and irrotational velocity fields. Results of this analysis show a strong influence of mean loading on the unsteady force generated by the passage of a one dimensional gust through a cascade of compressor blades.

  1. Wind velocity measurements under turbulent conditions using a sphere anemometer

    Heisselmann, Hendrik; Hoelling, Michael; Schulte, Bianca; Peinke, Joachim [Institute of Physics, University of Oldenburg (Germany)


    A well known problem of cup anemometry is the so-called overspeeding due to its momentum of inertia. As in nature turbulent flow conditions are predominant, cup anemometry leads to a wrong estimation of wind speeds. While cup anemometers do not provide the necessary time resolution to measure high frequency wind fluctuations, hot-wire anemometers are easily damaged under rough weather conditions. Therefore a robust, fast responding sphere anemometer was developed. The anemometer uses the thrust generated by the drag force on a sphere mounted on a flexible rod to detect wind velocities in two dimensions. The deflection of the rod is proportional to the drag force and can be measured either by means of a light pointer or by use of strain gauges. The two different measurement techniques were compared. The dynamic behaviour of the thrust anemometer was studied under laboratory conditions using a wind gust generator. The characteristics of different sphere-types and different rod materials were evaluated in order to optimize the setup. Results of open air measurements with hot-wire anemometer, sonic anemometer and sphere anemometer were compared by statistical methods.

  2. Monitoring Wind Turbine Loading Using Power Converter Signals

    Rieg, C. A.; Smith, C. J.; Crabtree, C. J.


    The ability to detect faults and predict loads on a wind turbine drivetrain's mechanical components cost-effectively is critical to making the cost of wind energy competitive. In order to investigate whether this is possible using the readily available power converter current signals, an existing permanent magnet synchronous generator based wind energy conversion system computer model was modified to include a grid-side converter (GSC) for an improved converter model and a gearbox. The GSC maintains a constant DC link voltage via vector control. The gearbox was modelled as a 3-mass model to allow faults to be included. Gusts and gearbox faults were introduced to investigate the ability of the machine side converter (MSC) current (I q) to detect and quantify loads on the mechanical components. In this model, gearbox faults were not detectable in the I q signal due to shaft stiffness and damping interaction. However, a model that predicts the load change on mechanical wind turbine components using I q was developed and verified using synthetic and real wind data.

  3. Variable structure strategy to avoid amplitude and rate saturation in pitch control of a wind turbine

    Garelli, Fabricio; Camocardi, Pablo [CONICET, LEICI, Depto. Electrotecnia, Facultad de Ingenieria, Universidad Nacional de La Plata, 1 y 47, CC 91 (1900), La Plata (Argentina); Mantz, Ricardo J. [CICpBA, LEICI, Depto. Electrotecnia, Facultad de Ingenieria, Universidad Nacional de La Plata, 1 y 47, CC 91 (1900), La Plata (Argentina)


    This work proposes the application of a recent compensation technique for input constraints avoidance to the pitch control of a wind turbine. The pitch angle actuators commonly present a hard limit on their rate of change together with the natural amplitude saturation, and a dynamics during their unconstrained operation that can be modeled as a first-order linear system. This dynamic behavior of the pitch actuator requires a particular design of the compensation method, which is based on variable structure systems to avoid both amplitude and rate input saturation by means of an auxiliary loop. The developed methodology reduces the pitch actuator activity necessary to regulate the generated power around its nominal value when facing sudden wind gusts. Another interesting feature of the proposal is that it allows the operator to fix conservative bounds for the actuator speed operation in order to increment the structural robustness of the wind turbine and to extend in this way the service life of the energy system. The effectiveness of the proposed strategy is evaluated by simulation results in an autonomous wind energy conversion system for water pumping with a brushless double feed induction generator (BDFIG). (author)

  4. 8000 Ways to Model a Vortex: A Review of Hindcast Wind Field Methodologies

    Sweeney, J.


    Hindcasts of cyclonic wind fields are crucial for extreme analysis in the oil and gas industry. Recent scientific developments have increased the number of parameterization options for tropical cyclone vortices, leading to well over 8000 permutations of model choices. Which is best? Also problematic is how best to blend modelled vortex winds into a global wind model (such as the Climate Forecast System Reanalysis (CFSR)) in order to resolve tropical cyclones to sufficient detail for wave modelling. Standard blending schemes can leave a 'moat' between the vortex and the CFSR circulation (see Figure 1 from TC Olivia 1996). Using a 35-year track database from the Australian Bureau of Meteorology, this study assesses model configurations and blending schemes against the most extensive measured meteorological dataset in the north-east Indian Ocean (largely commercial-in-confidence). The Holland profile models of 1980 and 2008 are two starting points, with other options examined for radius to maximum wind calculations, pressure-wind relationships, averaging periods, atmospheric profiles, gust factors, and asymmetry methods. Once a vortex is modelled, the winds are then fitted to the radius of gales and blended into the CFSR before further verification. Initial results support recent theoretical developments by Hu et al (2012), with additional results that call for a new asymmetry method and the separation of pressure and wind field modelling.

  5. A review of severe thunderstorms in Australia

    Allen, John T.; Allen, Edwina R.


    Severe thunderstorms are a common occurrence in Australia and have been documented since the first European settlement in 1788. These events are characterized by large damaging hail in excess of 2 cm, convective wind gusts greater than 90 km h- 1 and tornadoes, and contribute a quarter of all natural hazard-related losses in the country. This impact has lead to a growing body of research and insight into these events. In this article, the state of knowledge regarding their incidence, distribution, and the resulting hail, tornado, convective wind, and lightning risk will be reviewed. Applying this assessment of knowledge, the implications for forecasting, the warning process, and how these events may respond to climate change and variability will also be discussed. Based on this review, ongoing work in the field is outlined, and several potential avenues for future research and exploration are suggested. Most notably, the need for improved observational or proxy climatologies, the forecasting guidelines for tornadoes, and the need for a greater understanding of how severe thunderstorms respond to climate variability are highlighted.

  6. El ojo ajeno: Colombia por primera vez y hace medio siglo

    David Bushnell


    Full Text Available "Este país me va a gustar", fueron las palabras que estampé en la primera carta dirigida a mis padres después de pisar tierra colombiana. Había llegado a fines de diciembre de 1943, en vuelo de Panamá a Medellín, y mientras el avión de hélice daba vueltas para aterrizar en el angosto valle de Aburrá sufrí un ataque de mareo que lógicamente me habría inclinado a formarme una opinión menos optimista. Sin embargo, venía con unas expectativas muy positivas, basadas en mis lecturas de estudiante universitario, ya que por aquellos años, a diferencia de tiempos más recientes, gozaba Colombia de una imagen internacional muy de primera... es decir, entre las pocas personas que habían oído hablar del país. Se perfilaba como un oasis de paz y democracia, o como una especie de Costa Rica andina. Y en realidad me gustó; aunque no todo, por supuesto.

  7. Simulation of Inertial Navigation System Errors at Aerial Photography from Uav

    Shults, R.


    The problem of accuracy determination of the UAV position using INS at aerial photography can be resolved in two different ways: modelling of measurement errors or in-field calibration for INS. The paper presents the results of INS errors research by mathematical modelling. In paper were considered the following steps: developing of INS computer model; carrying out INS simulation; using reference data without errors, estimation of errors and their influence on maps creation accuracy by UAV data. It must be remembered that the values of orientation angles and the coordinates of the projection centre may change abruptly due to the influence of the atmosphere (different air density, wind, etc.). Therefore, the mathematical model of the INS was constructed taking into account the use of different models of wind gusts. For simulation were used typical characteristics of micro electromechanical (MEMS) INS and parameters of standard atmosphere. According to the simulation established domination of INS systematic errors that accumulate during the execution of photographing and require compensation mechanism, especially for orientation angles. MEMS INS have a high level of noise at the system input. Thanks to the developed model, we are able to investigate separately the impact of noise in the absence of systematic errors. According to the research was found that on the interval of observations in 5 seconds the impact of random and systematic component is almost the same. The developed model of INS errors studies was implemented in Matlab software environment and without problems can be improved and enhanced with new blocks.

  8. Cloud-Resolving Modeling Intercomparison Study of a Squall Line Case from MC3E - Properties of Convective Core

    Fan, J.; Han, B.; Varble, A.; Morrison, H.; North, K.; Kollias, P.; Chen, B.; Dong, X.; Giangrande, S. E.; Khain, A.; Lin, Y.; Mansell, E.; Milbrandt, J.; Stenz, R.; Thompson, G.; Wang, Y.


    The large spread in CRM model simulations of deep convection and aerosol effects on deep convective clouds (DCCs) makes it difficult to (1) further our understanding of deep convection and (2) define "benchmarks" and then limit their use in parameterization developments. A constrained model intercomparsion study on a mid-latitude mesoscale squall line is performed using the Weather Research & Forecasting (WRF) model at 1-km horizontal grid spacing with eight cloud microphysics schemes to understand specific processes that lead to the large spreads of simulated convection and precipitation. Various observational data are employed to evaluate the baseline simulations. All simulations tend to produce a wider convective area but a much narrower stratiform area. The magnitudes of virtual potential temperature drop, pressure rise, and wind speed peak associated with the passage of the gust front are significantly smaller compared with the observations, suggesting simulated cool pools are weaker. Simulations generally overestimate the vertical velocity and radar reflectivity in convective cores compared with the retrievals. The modeled updraft velocity and precipitation have a significant spread across eight schemes. The spread of updraft velocity is the combination of both low-level pressure perturbation gradient (PPG) and buoyancy. Both PPG and thermal buoyancy are small for simulations of weak convection but both are large for those of strong convection. Ice-related parameterizations contribute majorly to the spread of updraft velocity, while they are not the reason for the large spread of precipitation. The understandings gained in this study can help to focus future observations and parameterization development.

  9. Tool for Forecasting Cool-Season Peak Winds Across Kennedy Space Center and Cape Canaveral Air Force Station (CCAFS)

    Barrett, Joe H., III; Roeder, William P.


    Peak wind speed is important element in 24-Hour and Weekly Planning Forecasts issued by 45th Weather Squadron (45 WS). Forecasts issued for planning operations at KSC/CCAFS. 45 WS wind advisories issued for wind gusts greater than or equal to 25 kt. 35 kt and 50 kt from surface to 300 ft. AMU developed cool-season (Oct - Apr) tool to help 45 WS forecast: daily peak wind speed, 5-minute average speed at time of peak wind, and probability peak speed greater than or equal to 25 kt, 35 kt, 50 kt. AMU tool also forecasts daily average wind speed from 30 ft to 60 ft. Phase I and II tools delivered as a Microsoft Excel graphical user interface (GUI). Phase II tool also delivered as Meteorological Interactive Data Display System (MIDDS) GUI. Phase I and II forecast methods were compared to climatology, 45 WS wind advisories and North American Mesoscale model (MesoNAM) forecasts in a verification data set.




    Full Text Available Watermelon is a cucurbit, grown in almost all regions of the world, and it is enjoyed by most of the population. In Rio Grande do Norte the cultivation of watermelon has been increasing, because of the good climatic conditions in the region that provides adequate light and temperature throughout the year. In this con-text, the present study aimed at evaluating the yield and quality of watermelon cultivars in different planting dates in Mossoró-RN. The experiment was conducted in the garden didactic Department of Plant Sciences, Federal Rural University of the Semi-Arid in the period between June and December 2010. The experimental design was a randomized complete block in a split plot design with four 3 x 3 repetitions. The plots consisted of three cultivars of watermelon (Crimson Sweet, Olympia and Denver and subplots were planting (June, Au-gust and October. It is concluded that the yield and fruit quality were influenced by planting dates. The water-melon sowing in August resulted in higher average fruit weight and commercial productivity, and the fruits of lower acidity and better palatability were collected in the June planting.

  11. The 21st century decline in damaging European windstorms

    L. C. Dawkins


    of the footprint exceeding 20 ms−1 over land, A20, is shown to be a good predictor of windstorm damage. This damaging characteristic has decreased in the 21st century, due to a statistically significant decrease in the relative frequency of windstorms exceeding 20 ms−1 in north-western Europe, although an increase is observed in southern Europe. This is explained by a decrease in the quantiles of the footprint wind gust speed distribution above approximately 18 ms−1 at locations in this region. In addition, an increased variability in the number of windstorm events is observed in the 21st century. Much of the change in A20 is explained by the North Atlantic Oscillation (NAO. The correlation between winter total A20 and winter-averaged mean sea-level pressure resembles the NAO pattern, shifted eastwards over Europe, and a strong positive relationship (correlation of 0.715 exists between winter total A20 and winter-averaged NAO. The shifted correlation pattern, however, suggests that other modes of variability may also play a role in the variation in windstorm losses.

  12. Low-profile heliostat design for solar central receiver systems

    Fourakis, E.; Severson, A. M.


    Heliostat designs intended to reduce costs and the effect of adverse wind loads on the devices were developed. Included was the low-profile heliostat consisting of a stiff frame with sectional focusing reflectors coupled together to turn as a unit. The entire frame is arranged to turn angularly about a center point. The ability of the heliostat to rotate about both the vertical and horizontal axes permits a central computer control system to continuously aim the sun's reflection onto a selected target. An engineering model of the basic device was built and is being tested. Control and mirror parameters, such as roughness and need for fine aiming, are being studied. The fabrication of these prototypes is in process. The model was also designed to test mirror focusing techniques, heliostat geometry, mechanical functioning, and tracking control. The model can be easily relocated to test mirror imaging on a tower from various directions. In addition to steering and aiming studies, the tests include the effects of temperature changes, wind gusting and weathering. The results of economic studies on this heliostat are also presented.

  13. Case study of a severe windstorm over Slovakia and Hungary on 25 June 2008

    Simon, André; Kaňák, Ján; Sokol, Alois; Putsay, Mária; Uhrínová, Lucia; Csirmaz, Kálmán; Okon, Ľuboslav; Habrovský, Richard


    A system of thunderstorms approached the Slovakia and Hungary in the late evening hours of 25 June 2008, causing extensive damage and peak wind gusts up to 40 m/s. This study examines the macro- and mesosynoptic conditions for the windstorm using soundings, analyses, and forecasts of numerical models (ALADIN, ECMWF). A derecho-like character of the event is discussed. Meteosat Second Generation imagery and convective indices inferred from satellite and model data are used to assess the humidity distribution and the conditional instability of the thunderstorm environment. An intrusion of the environmental dry air into the convective system and intensification of downdrafts is considered to be one of the reasons for the damaging winds observed at some areas. This is supported by the radar imagery showing a sudden drop of radar reflectivity and creation of line echo wave patterns and bow echoes. A numerical simulation provided by the non-hydrostatic MM5 model indicated the development of meso-γ scale vortices embedded in the convective system. The genesis and a possible role of such vortices in creating rear-inflow jets and intensifying the low level winds are investigated with the help of the vorticity equation and several other diagnostic parameters. In addition, the effect of various physical parameterisations on the forecast of the windstorm is evaluated.

  14. SEEWIND - South-East European Wind Energy Exploitation. Wind energy research in South East Europe under the EC FP6 programme; SEEWIND - South-East European Wind Energy Exploitation. Windenergieforschung im 6. Rahmenprogramm der Europaeischen Union in Suedosteuropa

    Winkelmeier, H. [Verein Energiewerkstatt (Austria)


    Large areas in South East Europe offer perfect conditions for the Utilisation of Wind Energy. Local wind systems like ''Bora'', which occurs along the Adriatic Sea, or ''Koshava'', which flows between the ridge of the Carpathian Mountains and the Balkan Mountains from Romania over to Serbia, are generated through differences in pressure and temperature between the adjacent regions. Those wind systems therefore can be described as 'home made' and have very individual characteristics. Despite the excellent wind conditions of those locations, the mainly cliffy and complex terrain and the extreme wind conditions with turbulences and strong gusts make great demands on the design and operation of the wind turbines. Exactly those problems the European Commission asked to be investigated and therefore defined 'Complex terrain and local wind systems' as one of the research topics in the last call of the 6th Framework Programme. Under the lead management of Verein Energiewerkstatt, a consortium of ten partners from seven middle- and southeast European countries took part in this call for proposals and received acceptance for the submitted Project ''SEEWIND - South-East European Wind Energy Exploitation''. (orig.)

  15. A Look Inside Hurricane Alma


    Hurricane season in the eastern Pacific started off with a whimper late last month as Alma, a Category 2 hurricane, slowly made its way up the coast of Baja California, packing sustained winds of 110 miles per hour and gusts of 135 miles per hour. The above image of the hurricane was acquired on May 29, 2002, and displays the rainfall rates occurring within the storm. Click the image above to see an animated data visualization (3.8 MB) of the interior of Hurricane Alma. The images of the clouds seen at the beginning of the movie were retrieved from the National Oceanic and Atmospheric Association's (NOAA's) Geostationary Orbiting Environmental Satellite (GOES) network. As the movie continues, the clouds are peeled away to reveal an image of rainfall levels in the hurricane. The rainfall data were obtained by the Precipitation Radar aboard NASA's Tropical Rainfall Measuring Mission (TRMM) satellite. The Precipitation Radar bounces radio waves off of clouds to retrieve a reading of the number of large, rain-sized droplets within the clouds. Using these data, scientists can tell how much precipitation is occurring within and beneath a hurricane. In the movie, yellow denotes areas where 0.5 inches of rain is falling per hour, green denotes 1 inch per hour, and red denotes over 2 inches per hour. (Please note that high resolution still images of Hurricane Alma are available in the NASA Visible Earth in TIFF format.) Image and animation courtesy Lori Perkins, NASA Goddard Space Flight Center Scientific Visualization Studio

  16. Feasibility investigation of the giromill for generation of electrical power

    Brulle, R.V.


    The cyclogiro computer program, obtained from Prof. H. C. Larsen of the United States Air Force Institute of Technology, was modified to incorporate computation of blade loads for the normal operating and gust loading conditions. The program was also changed to allow computation of the effects of smoothing the blade rock angles in the region where they experienced large oscillations due to passing through a vortex shed by the previous blade. Using this program the various effects of rotor geometric parameters were investigated. Giromill configuration design concepts were explored. A baseline concept was adopted having an upper structural triangular tower extending through the lower support tower and supported by two main rotor bearings. Twenty-one different Giromill systems covering a power range of 120, 500 and 1500 kW were then synthesized. These were structurally analyzed and sized. An automatic electronic control concept built around existing equipment and employing state of the art techniques was developed. Preliminary cost estimates for generating electrical power from the Giromill systems were completed. Cost estimating relationships of the major items of equipment were formulated. 10 references. (auth)

  17. Semi-active vibration control in cable-stayed bridges under the condition of random wind load

    Heo, G.; Joonryong, Jeon


    This paper aims at an experimental study on the real-time vibration control of bridge structures using a semi-active vibration control method that has been in the spotlight recently. As structures are becoming larger and larger, structural harmful vibration caused by unspecified external forces such as earthquakes, gusts of wind, and collisions has been brought to attention as an important issue. These harmful vibrations can cause not only user anxiety but also severe structural damage or even complete failure of structures. Therefore, in view of structural safety and economical long-term maintenance, real-time control technology of the harmful structural vibration is urgently required. In this paper, a laboratory-scale model of a cable-stayed bridge was built, and a shear-type MR damper and a semi-active vibration control algorithm (Lyapunov and clipped optimal) were applied for the control of harmful vibration of the model bridge, in real time. On the basis of the test results, each semi-active control algorithm was verified quantitatively.

  18. Performance of tensor decomposition-based modal identification under nonstationary vibration

    Friesen, P.; Sadhu, A.


    Health monitoring of civil engineering structures is of paramount importance when they are subjected to natural hazards or extreme climatic events like earthquake, strong wind gusts or man-made excitations. Most of the traditional modal identification methods are reliant on stationarity assumption of the vibration response and posed difficulty while analyzing nonstationary vibration (e.g. earthquake or human-induced vibration). Recently tensor decomposition based methods are emerged as powerful and yet generic blind (i.e. without requiring a knowledge of input characteristics) signal decomposition tool for structural modal identification. In this paper, a tensor decomposition based system identification method is further explored to estimate modal parameters using nonstationary vibration generated due to either earthquake or pedestrian induced excitation in a structure. The effects of lag parameters and sensor densities on tensor decomposition are studied with respect to the extent of nonstationarity of the responses characterized by the stationary duration and peak ground acceleration of the earthquake. A suite of more than 1400 earthquakes is used to investigate the performance of the proposed method under a wide variety of ground motions utilizing both complete and partial measurements of a high-rise building model. Apart from the earthquake, human-induced nonstationary vibration of a real-life pedestrian bridge is also used to verify the accuracy of the proposed method.

  19. An Experimental High-Resolution Forecast System During the Vancouver 2010 Winter Olympic and Paralympic Games

    Mailhot, J.; Milbrandt, J. A.; Giguère, A.; McTaggart-Cowan, R.; Erfani, A.; Denis, B.; Glazer, A.; Vallée, M.


    Environment Canada ran an experimental numerical weather prediction (NWP) system during the Vancouver 2010 Winter Olympic and Paralympic Games, consisting of nested high-resolution (down to 1-km horizontal grid-spacing) configurations of the GEM-LAM model, with improved geophysical fields, cloud microphysics and radiative transfer schemes, and several new diagnostic products such as density of falling snow, visibility, and peak wind gust strength. The performance of this experimental NWP system has been evaluated in these winter conditions over complex terrain using the enhanced mesoscale observing network in place during the Olympics. As compared to the forecasts from the operational regional 15-km GEM model, objective verification generally indicated significant added value of the higher-resolution models for near-surface meteorological variables (wind speed, air temperature, and dewpoint temperature) with the 1-km model providing the best forecast accuracy. Appreciable errors were noted in all models for the forecasts of wind direction and humidity near the surface. Subjective assessment of several cases also indicated that the experimental Olympic system was skillful at forecasting meteorological phenomena at high-resolution, both spatially and temporally, and provided enhanced guidance to the Olympic forecasters in terms of better timing of precipitation phase change, squall line passage, wind flow channeling, and visibility reduction due to fog and snow.

  20. Toward controlling perturbations in robotic sensor networks

    Banerjee, Ashis G.; Majumder, Saikat R.


    Robotic sensor networks (RSNs), which consist of networks of sensors placed on mobile robots, are being increasingly used for environment monitoring applications. In particular, a lot of work has been done on simultaneous localization and mapping of the robots, and optimal sensor placement for environment state estimation1. The deployment of RSNs, however, remains challenging in harsh environments where the RSNs have to deal with significant perturbations in the forms of wind gusts, turbulent water flows, sand storms, or blizzards that disrupt inter-robot communication and individual robot stability. Hence, there is a need to be able to control such perturbations and bring the networks to desirable states with stable nodes (robots) and minimal operational performance (environment sensing). Recent work has demonstrated the feasibility of controlling the non-linear dynamics in other communication networks like emergency management systems and power grids by introducing compensatory perturbations to restore network stability and operation2. In this paper, we develop a computational framework to investigate the usefulness of this approach for RSNs in marine environments. Preliminary analysis shows promising performance and identifies bounds on the original perturbations within which it is possible to control the networks.