Abstracts of Some Journals

7/28/2019 Abstracts of Some Journals

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Abstracts of some journals1. Modern estimation of the parameters of the Weibull wind speed distribution for wind energy

analysis

March 2000

J.V. Seguro | T.W. Lambert

AbstractThree methods for calculating the parameters of the Weibull wind speed distribution for wind energy

analysis are presented: the maximum likelihood method, the proposed modified maximum likelihood

method, and the commonly used graphical method. The application of each method is demonstrated using a

sample wind speed data set, and a comparison of the accuracy of each method is also performed. The

maximum likelihood method is recommended for use with time series wind data, and the modified maximum

likelihood method is recommended for use with wind data in frequency distribution format.

2. Exploitation of wind as an energy source to meet the world's electricity demand

1 April 1998

Ezio Sesto | Claudio Casale

AbstractThis paper provides an introduction to the basic aspects of the exploitation of wind energy for

electricity generation, as regards both the characteristics of the source and the features and state-of-the-art

of today's wind energy conversion systems. It also provides an overview of worldwide applications of wind

energy and of the various factors currently driving the wind turbine market. Possible restraints to and

benefits from wind plant integration in utility systems are considered, as well as the use of stand-alone wind

systems. Some possible forecasts on the role of wind energy in the next two decades are also given.

3. Wind pressures on multi-level flat roofs of medium-rise buildings

April 2012

Jinxin Cao | Yukio Tamura | Akihito Yoshida

AbstractSince there is limited information on design of wind pressures on multi-level flat roofs from previous

studies and in wind loading codes, a wind tunnel experiment was carried out on 1:67 scaled models of a

series of medium-rise buildings. Using an assembled cubic plexiglass model and uniformly distributed

pressure taps, multi-level flat roofs with different configurations were easily fabricated and pressures on theroofs measured. Mean and fluctuating, local peak and area-averaged pressure coefficients were mainly

investigated and stochastic characteristics of wind pressures on multi-level flat roofs were determined.

Parameters of step geometry such as the effects of step dimension and configuration were considered. The

results showed no significant difference between minimum values of negative peak pressures on simple flat

roofs and on multi-level flat roofs, while negative pressure distributions and maximum values of positive
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peak pressures on the low-roof of multi-level flat roofs were highly dependent on step parameters. A

comparison with ASCE/SEI7-10 indicates that negative values with small tributary areas are larger than

those in related contents in the code, while negative values in other zones and positive values agree closely

with the code. Gaussian and negative-skewed non-Gaussian PDFs, as well as positive-skewed non-Gaussian

ones, were measured for multi-level flat roofs.

4. The starting and low wind speed behaviour of a small horizontal axis wind turbine

December 2004

A.K. Wright | D.H. Wood

AbstractIn order to extract the maximum possible power, it is important that the blades of small wind

turbines start rotating at the lowest possible wind speed. The starting performance of a three-bladed, 2m

diameter horizontal axis wind turbine was measured in field tests, and compared with calculations employing

a quasi-steady blade element analysis. Accurate predictions of rotor acceleration were made for a largerange of wind speeds, using a combination of interpolated aerofoil data and generic equations for lift and

drag at high angles of incidence. Also, significantly different values for the wind speeds at which the turbine

rotor starts and ceases to rotate were determined, indicating limitations in the traditional method of

describing starting performance with a single cut-in wind speed based on 10-min averages of wind speed

and turbine power. The blade element calculations suggest that most of the starting torque is generated

near the hub, whereas most power-producing torque comes from the tip region. The significance of these

results for blade design is discussed.

5. Wind tunnel blockage corrections: Review and application to Savonius vertical-axis wind

turbines

May 2011

Ian Ross | Aaron Altman

AbstractAn investigation into wake and solid blockage effects of vertical axis wind turbines (VAWTs) in

closed test-section wind tunnel testing is described. Static wall pressures have been used to derive velocity

increments along wind tunnel test section which in turn are applied to provide evidence of wake interference

characteristics of rotating bodies interacting within this spatially restricted domain. Vertical-axis wind

turbines present a unique aerodynamic obstruction in wind tunnel testing, whose blockage effects have not

yet extensively investigated. The flowfield surrounding these wind turbines is asymmetric, periodic,

unsteady, separated and highly turbulent. Static pressure measurements are taken along a test-section

sidewall to provide a pressure signature of the test models under varying rotor tip-speed ratios (freestream

conditions and model RPMs). Wake characteristics and VAWT performance produced by the same vertical-

axis wind turbine concept tested at different physical scales and in two different wind tunnels are

investigated in an attempt to provide some guidance on the scaling of the combined effects on blockage.
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This investigation provides evidence of the effects of large wall interactions and wake propagation caused by

these models at well below generally accepted standard blockage figures.

6. Large-eddy simulation of atmospheric boundary layer flow through wind turbines and wind

farms

April 2011

Fernando Port-Agel | Yu-Ting Wu | Hao Lu | Robert J. Conzemius

AbstractAccurate prediction of atmospheric boundary layer (ABL) flow and its interactions with wind turbines

and wind farms is critical for optimizing the design (turbine siting) of wind energy projects. Large-eddy

simulation (LES) can potentially provide the kind of high-resolution spatial and temporal information needed

to maximize wind energy production and minimize fatigue loads in wind farms. However, the accuracy of

LESs of ABL flow with wind turbines hinges on our ability to parameterize subgrid-scale (SGS) turbulent

fluxes as well as turbine-induced forces. This paper focuses on recent research efforts to develop and

validate an LES framework for wind energy applications. SGS fluxes are parameterized using tuning-free

Lagrangian scale-dependent dynamic models. These models optimize the local value of the model

coefficients based on the dynamics of the resolved scales. The turbine-induced forces (e.g., thrust, lift and

drag) are parameterized using two types of models: actuator-disk models that distribute the force loading

over the rotor disk, and actuator-line models that distribute the forces along lines that follow the position of

the blades. Simulation results are compared to wind-tunnel measurements collected with hot-wire

anemometry in the wake of a miniature three-blade wind turbine placed in a boundary layer flow. In

general, the characteristics of the turbine wakes simulated with the proposed LES framework are in good

agreement with the measurements in the far-wake region. Near the turbine, up to about five rotor

diameters downwind, the best performance is obtained with turbine models that induce wake-flow rotation

and account for the non-uniformity of the turbine-induced forces. Finally, the LES framework is used to

simulate atmospheric boundary-layer flow through an operational wind farm.

7. Experimental and numerical investigations of flow fields behind a small wind turbine with a

flanged diffuser

December 2005

K. Abe | M. Nishida | A. Sakurai | Y. Ohya | H. Kihara | E. Wada | K. Sato

AbstractExperimental and numerical investigations were carried out for flow fields of a small wind turbine

with a flanged diffuser. The present wind-turbine system gave a power coefficient higher than the Betz limit

(=16/27) owing to the effect of the flanged diffuser. To elucidate the flow mechanism, mean velocity profiles

behind a wind turbine were measured using a hot-wire technique. By processing the obtained data,

characteristic values of the flow fields were estimated and compared with those for a bare wind turbine. In

addition, computations corresponding to the experimental conditions were made to assess the predictive
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performance of the simulation model presently used and also to investigate the flow field in more detail. The

present experimental and numerical results gave useful information about the flow mechanism behind a

wind turbine with a flanged diffuser. In particular, a considerable difference was seen in the destruction

process of the tip vortex between the bare wind turbine and the wind turbine with a flanged diffuser.

8. Optimization method for wind turbine rotors

1 March 1999

P. Fuglsang | H.A. Madsen

AbstractThis paper presents a recently developed numerical multi-disciplinary optimization method for

design of horizontal axis wind turbines. The method allows multiple constraints. The objective was minimum

cost of energy, determined by the design giving fatigue and extreme loads and the annual production of

energy. Time domain aeroelastic calculations and Rainflow counting provided the life time equivalent fatigue

loads. A semi-empirical approach was developed for their sensitivities. This resulted in substantial savings incomputing time. An optimization of a 1.5MW stall regulated rotor demonstrated the design method, and the

results showed that constraints on loads are important for the applicability of the optimization results. Shape

optimization of the rotor resulted in maximum strain on more than 80% of the blade span and hence more

efficient use of material. The cost of energy was reduced compared to a traditional design with the same

swept area. The optimum specific power was found to 460W/m2, which is lower than that of modern Danish

wind turbines. Studies for optimum airfoil characteristics showed that the airfoil sections should have a

relative high maximum lift at the entire span including the tip region. An increase in the swept area should

therefore involve a complete redesign of the rotor blades, and avoid the use of low maximum lift airfoils at

the tip, which so far has been widely used to control peak power.

9. The methodology for aerodynamic study on a small domestic wind turbine with scoop

January 2008

F. Wang | L. Bai | J. Fletcher | J. Whiteford | D. Cullen

AbstractThe aim of this study is to investigate the possibility of improving wind energy capture, under low

wind speed conditions, in a built-up area, and the design of a small wind generator for domestic use in such

areas. This paper reports the first part of this study: the development of the methodology using physical

tests conducted in a boundary layer wind tunnel and computer modelling using commercial computationalfluid dynamics (CFD) code. The activities reported in this paper are optimisation of a scoop design and

validation of the CFD model. The final design of scoop boosts the airflow speed by a factor of 1.5 times

equivalent to an increase in power output of 2.2 times with the same swept area. Wind tunnel tests show

that the scoop increases the output power of the wind turbine. The results also indicate that, by using a

scoop, energy capture can be improved at lower wind speeds. The experimentally determined power curves

of the wind generator located in the scoop are in good agreement with those predicted by the CFD model.
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This suggests that first the developed computer model was robust and could be used later for design

purposes. Second the methodology developed here could be validated in a future study for a new rotor blade

system to function well within the scoop. The power generation of such a new wind turbine is expected to be

increased, particularly at locations where average wind speed is lower and more turbulent. The further study

will be reported elsewhere.

10. Wind models for simulation of power fluctuations from wind farms

December 2002

Poul Srensen | Anca D. Hansen | Pedro Andr Carvalho Rosas

AbstractThis paper presents a wind model, which has been developed for studies of the dynamic interaction

between wind farms and the power system to which they are connected. The wind model is based on a

power spectral description of the turbulence, which includes the coherence between wind speeds at different

wind turbines in a wind farm, together with the effect of rotational sampling of the wind turbine blades inthe rotors of the individual wind turbines. Both the spatial variations of the turbulence and the shadows

behind the wind turbine towers are included in the model for rotational sampling. The model is verified using

measured wind speeds and power fluctuations from wind turbines.

11. Optimal frequency design of wind turbine blades

August 2002

Karam Y. Maalawi | Hani M. Negm

AbstractAn optimization model for the design of a typical blade structure of horizontal-axis wind turbines is

presented. The main spar is represented by thin-walled tubular beam composed of uniform segments each

of which has different cross-sectional properties and length. The optimization variables are chosen to be the

cross-sectional area, radius of gyration and length of each segment. The optimal design is pursued with

respect to maximum frequency design criterion. Global optimality is attainable by the proposed model and a

novel mathematical concept is given for placing the system frequencies. The problem is formulated as a

non-linear mathematical programming problem solved by multi-dimensional search techniques. Structural

analysis is restricted to the case of uncoupled flapping motion of the rotating blade, where an exact method

of solution is given for calculating the natural vibration characteristics. Aeroelastic stability boundaries and

steady-state response are calculated using Floquet's transition matrix theory. The results show that theapproach used in this study is efficient and produces improved designs as compared with a reference or

baseline design.

12. Small wind turbine power control in intermittent wind gusts

May 2011

J. Bystryk | P.E. Sullivan
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AbstractThis paper analyzes control strategies for a small scale wind turbine in intermittent winds using a

computer model based on wind data collected on-site and computer simulation data. Standard generator

control with a lowered gain was found to produce the greatest power capture by biasing the rotational speed

towards high energy wind gusts. Optimal gain was able to be determined by calculating an estimated wind

speed using physical and measured quantities. An augmentation to the standard control provides a method

for capturing power safely beyond the rated wind speed.

13. Energy output estimation for small-scale wind power generators using Weibull-representative

wind data

April 2003

Ali Naci Celik

AbstractEstimation of energy output for small-scale wind power generators is the subject of this article.

Monthly wind energy production is estimated using the Weibull-representative wind data for a total of 96

months, from 5 different locations in the world. The Weibull parameters are determined based on the wind

distribution statistics calculated from the measured data, using the gamma function. The wind data in

relative frequency format is obtained from these calculated Weibull parameters. The wind speed data in

time-series format and the Weibull-representative wind speed data are used to calculate the wind energy

output of a specific wind turbine. The monthly energy outputs calculated from the time-series and the

Weibull-representative data are compared. It is shown that the Weibull-representative data estimate the

wind energy output very accurately. The overall error in estimation of monthly energy outputs for the total

96 months is 2.79%.

14. Wind tunnel study of the wake meandering downstream of a modelled wind turbine as an

effect of large scale turbulent eddies

February 2012

G. Espaa | S. Aubrun | S. Loyer | P. Devinant

AbstractExperimental results on the unsteady behaviour of the wake of a modelled wind turbine in an

atmospheric boundary layer (ABL) wind tunnel are presented. Tests were performed by modelling in the

wind tunnel an ABL above a neutral moderately rough terrain at a geometric scale of 1:400, and a wind

turbine with the help of the actuator disk concept. In order to characterise the meandering properties of its

wake, velocity spectra and spacetime correlations were measured through hot wire anemometry, both in

the wake of the modelled wind turbine and in the wake of a solid disk. Comparing these two configurations

allowed the examination of the differences between the random motion of the whole wind turbine wake

characterising the meandering in the first case, and the periodic oscillations of the well-known vortex

shedding, which appears behind a bluff-body, in the second case. Finally, the same experiments were
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performed in homogeneous and isotropic turbulent flows to exhibit the role of the large atmospheric

turbulent scales in the meandering process.

15. Rotational and turbulence effects on a wind turbine blade. Investigation of the stall

mechanisms

AugustSeptember 2008

C. Sicot | P. Devinant | S. Loyer | J. Hureau

AbstractThe aim of this study was to evaluate experimentally rotation and turbulence effects on a wind

turbine blade aerodynamics, focusing particularly on stall mechanisms. The wind tunnel tests consisted in

surface pressure measurements on a horizontal axis wind turbine airfoil subjected to freestream turbulence

levels varying from 4.5% to 12%. A method to determine the position of the separation point on the

rotating blade, based on the chordwise pressure gradient in the separated area, is proposed. The results

showed an influence of the freestream turbulence level on the separation point position. Experimental

results in the literature showed lift augmentation for a rotating blade. In our case, the study of the

separation point position coupled with the pressure distributions on the airfoil shows that this lift

augmentation seems related to a lower value of the pressure in the separated area rather than to a stall

delay phenomenon.

16. An extended k model for turbulent flow through horizontal-axis wind turbines

January 2008

Amina El Kasmi | Christian Masson

AbstractThis paper proposes a new model for simulating flow through a horizontal-axis wind turbine. The

proposed model uses an extra term added to the approximate transport equation for the turbulence energy

dissipation rate. The term presents the role of the energy transfer rate from large-scale turbulence to small-

scale turbulence in the turbine's near-wake region. This term significantly improves agreement with

experimental data. To validate the model, results are presented for the Nibe wind turbine B, the Danwin

180/23, and the MOD-0A.

17. Experimental study of wind-turbine airfoil aerodynamics in high turbulence

June 2002

Ph. Devinant | T. Laverne | J. Hureau

AbstractWind turbines very often have to operate in high turbulence related, for example, with lower layers

atmospheric turbulence or wakes of other wind turbines. Most available data on airfoil aerodynamics

concerns mainly aeronautical applications, which are characterized by a low level of turbulence (generally

less than 1%) and low angles of attack. This paper presents wind tunnel test data for the aerodynamic

propertieslift, drag, pitching moment, pressure distributionsof an airfoil used on a wind turbine when
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subjected to incident flow turbulence levels of 0.516% and placed at angles of attack up to 90. The results

show that the aerodynamic behavior of the airfoil can be strongly affected by the turbulence level both

qualitatively and quantitatively. This effect is especially evidenced in the angle of attack range corresponding

to airfoil stall, as the boundary layer separation point advances along the leeward surface of the airfoil.

18. CFD simulation of cross-ventilation flow for different isolated building configurations:

Validation with wind tunnel measurements and analysis of physical and numerical diffusion

effects

MayJuly 2012

R. Ramponi | B. Blocken

AbstractComputational Fluid Dynamics (CFD) has become one of the most important tools for the

assessment of natural cross-ventilation of buildings. To ensure the accuracy and reliability of CFD

simulations, solution verification and validation studies are needed, as well as detailed sensitivity studies to

analyse the impact of computational parameters on the results. In a previous study by the present authors,

the impact of a wide range of computational parameters on the cross-ventilation flow in a generic isolated

single-zone building was investigated. This paper presents the follow-up study that focuses in more detail on

validation with wind tunnel measurements and on the effects of physical and numerical diffusion on the

cross-ventilation flow. The CFD simulations are performed with the 3D steady Reynolds-Averaged Navier

Stokes (RANS) approach with the SST k model to provide closure. Validation of the coupled outdoor wind

flow and indoor airflow simulations is performed based on Particle Image Velocimetry (PIV) measurements

for four different building configurations. The analysis of numerical diffusion effects is performed in two

parts. First, the effect of physical diffusion is analysed by changing the inlet profiles of turbulent kinetic

energy within a realistic range. Second, the effect of numerical diffusion is investigated by changing the grid

resolution and by applying both first-order and second-order discretisation schemes. The results of the

validation study show a good to a very good agreement for three of the four configurations, while a

somewhat less good agreement is obtained for the fourth configuration. The results of the diffusion study

show that the effects of physical and numerical diffusion are very similar. Along the centreline between the

openings, these effects are most pronounced inside the building, and less pronounced outside the building.

The velocity-vector fields however show that increased physical and numerical diffusion decreases the size

of the upstream standing vortex and increase the spread of the jet entering the buildings. It is concluded

that diffusion is an important transport mechanism in cross-ventilation of buildings, and that special care is

needed to select the right amount of physical diffusion and to reduce the numerical diffusion, using high-

resolution grids and using at least second-order accurate discretisation schemes.

19. Optimum design configuration of Savonius rotor through wind tunnel experiments
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AugustSeptember 2008

U.K. Saha | S. Thotla | D. Maity

AbstractWind tunnel tests were conducted to assess the aerodynamic performance of single-, two- and

three-stage Savonius rotor systems. Both semicircular and twisted blades have been used in either case. A

family of rotor systems has been manufactured with identical stage aspect ratio keeping the identical

projected area of each rotor. Experiments were carried out to optimize the different parameters like number

of stages, number of blades (two and three) and geometry of the blade (semicircular and twisted). A further

attempt was made to investigate the performance of two-stage rotor system by inserting valves on the

concave side of blade.

20. Spectral coherence model for power fluctuations in a wind farm

March 2012

A. Vigueras-Rodrguez | P. Srensen | A. Viedma | M.H. Donovan | E. Gmez Lzaro

AbstractThis paper provides a model for the coherence between wind speeds located in a horizontal plane

corresponding to hub height of wind turbines in a large wind farm.The model has been developed using wind

speed and power measurements from the 72 Wind Turbines and two of the meteorological masts from

Nysted offshore wind farm during 9 months.The coherence model developed in this paper is intended for use

of power fluctuations in large offshore wind farms. In this way, analysing the current coherence models it is

shown the needing of a new one, adapted to the characteristic distances and the related time scale.

21. A CFD approach for modeling the rime-ice accretion process on a horizontal-axis wind turbine

AprilMay 2010

Ping Fu | Masoud Farzaneh

AbstractThe main objective of this paper is to model the rime-ice accretion process on a horizontal-axis wind

turbine (HAWT) operating under icing conditions. The model calculation procedure was divided into two

stages. The first stage consists of computing the two-phase flow that is composed of air and water phases.

The two-phase flow was solved using the EulerianEulerian approach with the help of Fluent, a commercial

CFD code. At the end of the calculations, it is possible to obtain the local volume fraction and local water

incidence velocity, which can be used to estimate the local collision coefficient. In the second stage, the

thickness of the newly accreted ice layer was calculated and the geometry so obtained was processed with

an in-house smoothing algorithm. From the model simulation, it is possible to obtain the 3-D ice shape, as

well as the ice load on the HAWT blade, which can then be used to analyze the performance of the HAWT

under icing conditions, or to help develop a feasible de-icing solution. The important model input parameters

include: air speed, median volume diameter (MVD) of water droplets, liquid water content (LWC) and air

temperature. The turbine under consideration is a NREL VI turbine that rotates along its axis at a constant
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angular speed. In the flow domain, a rotating reference frame was defined to account for the angular

movement of the wind turbine. The results reveal, among other things, ice geometry information that can

otherwise hardly be obtained by on-site observations.

22. A simulation model for wind turbine blade fatigue loads

November 1999

M. Noda | R.G.J. Flay

AbstractThe paper describes a horizontal axis wind turbine time domain simulation and fatigue estimation

program written using the DelphiTM language. The program models the flapwise motion of a single rotor

blade to determine the blade-root fatigue damage of a medium size wind turbine. The effects of turbulence

intensity, mean wind speed, wind shear, vertical wind component, dynamic stall, stall hysteresis, and blade

stiffness were examined. When all these effects were simulated it is found that a reduction in life of about 2

occurs between a low wind speed low turbulence intensity site, compared to a high wind speed highturbulence intensity site.

23. Experimental study of wind-induced ventilation in urban building of cube arrays with various

layouts

April 2012

Sheikh Ahmad Zaki | Aya Hagishima | Jun Tanimoto

AbstractUrban airflow and dispersion processes have become matters of great concern from the viewpoints

of urban heat island phenomena, thermal comfort of pedestrians, hazard control for toxic gases, wind-

induced ventilation of urban buildings, and so on. In this study, the authors measured the spatial

distribution of the pressure drag acting on the walls of rectangular block arrays in a wind tunnel. The arrays

were arranged with staggered, square, and diamond layouts under different conditions of roughness and

packing density. The total drag and wind profiles of the arrays were preliminarily measured. On the basis of

experimental results, the contribution of pressure drag to the total surface drag on staggered cube arrays

was estimated at greater than 95%. In addition, the bulk pressure coefficients Cp for the arrays defined by

mean velocity at a height of H, 2H and 20H were derived (H refers to the height of a block), and the clear

relation between Cp and the block packing densities were shown for rough estimation of wind-induced

ventilation in urban buildings. In addition, the authors present a simple mathematical expression to explain

the relationship.

24. Field measurements of aerodynamic pressures in tunnels induced by high speed trains

January 2012

Yung-Yen Ko | Cheng-Hsing Chen | Ing-Tsang Hoe | Shin-Tsyr Wang
http://dx.doi.org/10.1016/S0167-6105(99)00099-9http://dx.doi.org/10.1016/S0167-6105(99)00099-9http://dx.doi.org/10.1016/j.jweia.2012.02.008http://dx.doi.org/10.1016/j.jweia.2012.02.008http://dx.doi.org/10.1016/j.jweia.2012.02.008http://dx.doi.org/10.1016/j.jweia.2011.10.008http://dx.doi.org/10.1016/j.jweia.2011.10.008http://dx.doi.org/10.1016/j.jweia.2011.10.008http://dx.doi.org/10.1016/j.jweia.2012.02.008http://dx.doi.org/10.1016/j.jweia.2012.02.008http://dx.doi.org/10.1016/S0167-6105(99)00099-9


11/11

AbstractThe passage of high speed trains causes aerodynamic effects in tunnels, and considerable pressure

transients are generated because of the restricted airspace within the tunnel. This leads to passenger

discomfort, noise surrounding the tunnel, resistance to train movement, and possible damage to the train

body and tunnel facilities. For the real assessment of the aerodynamic pressures in the tunnel induced by

the passing trains of the high speed rail in Taiwan, a series of field measurements were performed near the

portal and the shaft or the adit of the tunnel during normal operation. The measurements were conducted

for several train speeds, including the maximum operation speed of the high speed rail in Taiwan, which is

300km/h. Pressure sensors were deployed along the tunnel to investigate the propagation of pressure

waves. The results show that the train nose entry/exit generated a compression wave propagating

throughout the tunnel, resulting in a sharp increase in pressure. Conversely, the train tail entry/exit

generated an expansion wave causing a pressure drop. The successive reflections of these pressure waves

between both ends of the tunnel were observed. The pass-by of a train inside the tunnel also induced an

immediate local pressure drop due to aerodynamic drag. Based on the measurement results, the spatialvariation of the train-induced pressure peaks inside the tunnel is discussed. Furthermore, the relationship

between the pressure peaks and the train speed is established, and the influence of the cross-sectional area

of the tunnel is also presented.

25. Development of a shrouded wind turbine with a flanged diffuser

May 2008

Yuji Ohya | Takashi Karasudani | Akira Sakurai | Ken-ichi Abe | Masahiro Inoue

AbstractWe have developed a wind turbine system that consists of a diffuser shroud with a broad-ring flange

at the exit periphery and a wind turbine inside it. The flanged-diffuser shroud plays a role of a device for

collecting and accelerating the approaching wind. Emphasis is placed on positioning the flange at the exit of

a diffuser shroud. Namely, the flange generates a low-pressure region in the exit neighborhood of the

diffuser by vortex formation and draws more mass flow to the wind turbine inside the diffuser shroud. To

obtain a higher power output of the shrouded wind turbine, we have examined the optimal form of the

flanged diffuser, such as the diffuser open angle, flange height, hub ratio, centerbody length, inlet shroud

shape and so on. As a result, a shrouded wind turbine equipped with a flanged diffuser has been developed,

and demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 4

5 compared to a standard (bare) wind turbine. In a field experiment using a prototype wind turbine with aflanged diffuser shroud, the output performance was as expected and equalled that of the wind tunnel

experiment.
http://dx.doi.org/10.1016/j.jweia.2008.01.006http://dx.doi.org/10.1016/j.jweia.2008.01.006http://dx.doi.org/10.1016/j.jweia.2008.01.006

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