scholarly journals Influence of Embankments With Parapets on the Cross-Wind Turbulence Intensity at the Contact Wire of Railway Overheads

2010 ◽  
Author(s):  
Sergio Avila-Sanchez ◽  
Oscar Lopez-Garcia ◽  
Jose Meseguer
Keyword(s):  
Wind Tunnel ◽  
Environmental Factor ◽  
Turbulence Intensity ◽  
Experimental Analysis ◽  
System Operation ◽  
Contact Wire ◽  
Aerodynamic Loads ◽  
Essential Parameter ◽  
Railway System ◽  
Undamped Oscillations

Winds as an environmental factor can cause significant difficulties for the railway system operation. The railway overhead has been particularly vulnerable to cross-winds related problems, such as development of undamped oscillations due to galloping phenomenon. The installation of windbreaks to decrease the aerodynamic loads on the train can affect the loads on railway overheads triggering cable galloping. One essential parameter to indicate the influence of the parapet wake on the catenary contact wire is the turbulence intensity. In this paper the results of an experimental analysis of the turbulence intensity due to the presence of parapets carried out in a wind tunnel are reported. Embankments equipped with different parapets have been tested and turbulence intensity has been measured at both contact wire locations, windward and leeward. The relative influence of the parapets is measured through a reduced turbulence intensity, defined as the ratio between the turbulence intensity measured with parapet and the turbulence intensity in the case without any parapet on the embankment. In general the reduced turbulence intensity increases as the height of the parapet increases.

scholarly journals Blind test comparison of the performance and wake flow between two in-line wind turbines exposed to different atmospheric inflow conditions

2016 ◽  
Author(s):  
Jan Bartl ◽  
Lars Sætran
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Turbulence Intensity ◽  
Wake Flow ◽  
Detached Eddy Simulation ◽  
Mean Velocity ◽  
Blind Test ◽  
The Mean ◽  
Inlet Conditions ◽  
Inflow Conditions

Abstract. This is a summary of the results of the fourth Blind test workshop which was held in Trondheim in October 2015. Herein, computational predictions on the performance of two in-line model wind turbines as well as the mean and turbulent wake flow are compared to experimental data measured at NTNU's wind tunnel. A detailed description of the model geometry, the wind tunnel boundary conditions and the test case specifications was published before the workshop. Expert groups within Computational Fluid Dynamics (CFD) were invited to submit predictions on wind turbine performance and wake flow without knowing the experimental results at the outset. The focus of this blind test comparison is to examine the model turbines' performance and wake development up until 9 rotor diameters downstream at three different atmospheric inflow conditions. Besides a spatially uniform inflow field of very low turbulence intensity (TI = 0.23 %) as well as high turbulence intensity (TI = 10.0 %), the turbines are exposed to a grid-generated atmospheric shear flow (TI = 10.1 %). Five different research groups contributed with their predictions using a variety of simulation models, ranging from fully resolved Reynolds Averaged Navier Stokes (RANS) models to Large Eddy Simulations (LES). For the three inlet conditions the power and the thrust force of the upstream turbine is predicted fairly well by most models, while the predictions of the downstream turbine's performance show a significantly higher scatter. Comparing the mean velocity profiles in the wake, most models approximate the mean velocity deficit level sufficiently well. However, larger variations between the models for higher downstream positions are observed. The prediction of the turbulence kinetic energy in the wake is observed to be very challenging. Both the LES model and the IDDES (Improved Delayed Detached Eddy Simulation) model, however, are consistently managing to provide fairly accurate predictions of the wake turbulence.

The development of the winged keel for twelve-metre yachts

1986 ◽  
Vol 173 ◽  
pp. 55-71 ◽  
Author(s):  
P. Van Oossanen ◽  
P. N. Joubert
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Experimental Analysis ◽  
Design Parameters ◽  
Low Aspect Ratio ◽  
Lifting Surface ◽  
Wind Tunnel Measurements ◽  
America’S Cup

In this paper the authors present a numerical and experimental analysis of the winged keel originally developed for the International twelve-metre class yacht Australia II that won the America's Cup in 1983. After briefly explaining why this keel was evolved in 1981, some basic considerations are presented relating keel performance to various design parameters. The results of numerical flow analyses and wind-tunnel measurements on a model of a winged keel are then presented and compared. The differences between the performance with and without winglets fitted to the keel are discussed. The fitting of winglets appreciably enhances the performance of a low-aspect-ratio lifting surface such as the keel of a twelve-metre yacht.

Evaluation on Across-Wind Response of Tall Building According to Aerodynamic Shapes

2013 ◽  
Vol 823 ◽  
pp. 131-136
Author(s):  
Jang Youl You ◽  
Ki Pyo You ◽  
Young Moon Kim
Keyword(s):  
Wind Tunnel ◽  
Cross Sections ◽  
Turbulence Intensity ◽  
Suburban Area ◽  
Light Weight ◽  
Wind Tunnel Tests ◽  
Large Cities ◽  
High Rise ◽  
Type Form ◽  
Wind Response

High-rise buildings constructed in large cities are thin and long in their shape and are both unconventional and light-weight. The purpose of this study is to reduce the across-wind response of high-rise buildings (unconventional) under the influence of wind load. As a means to change the external shape of high-rise buildings, we selected the flat Y-type form. It is generally applied in domestic high-rise buildings for examination. Wind tunnel tests take place on 12 high-rise buildings, composed of three different Y-type shapes such as basic square forms with square cross sections and unconventional forms, in a suburban area (α=0.15) with a turbulence intensity of 10%.

scholarly journals Wind Tunnel Experiment for Predicting a Visible Plume Region from a Nuclear Power Plant Cooling Tower

2014 ◽  
Vol 53 (2) ◽  
pp. 234-241 ◽  
Author(s):  
Dong-Peng Guo ◽  
Ren-Tai Yao ◽  
Dan Fan
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Wind Tunnel ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Nuclear Power ◽  
Cooling Tower ◽  
Wind Tunnel Experiment ◽  
Plume Rise ◽  
Plume Region

AbstractThis paper introduces a wind tunnel experiment to study the effect of the cooling tower of a nuclear power plant on the flow and the characteristics of visible plume regions. The relevant characteristics of the flow field near the cooling tower, such as the plume rise and the visible plume region, are compared with the results of previous experimental data from Électricité de France (EDF) and the Briggs formulas. The results show that the wind tunnel experiment can simulate the top backflow of the cooling tower and the rear cavity regions among others. In the near-wake region, including the recirculation cavity, mean velocity decreases and turbulence intensity increases significantly. The maximum turbulence intensity observed is 0.5. In addition, the disturbed flow extent of the cooling tower top reaches 1.5 times the cooling tower height. Analysis of the visible plume region shows that the wind tunnel experiment can simulate the variation of a visible plume region. The results are consistent with the wind tunnel experiment of EDF. Moreover, the plume rise analysis shows that the wind tunnel experiment data are in agreement with the Briggs formulas for 50–200 m. As a whole, the proposed wind tunnel experiment can simulate the flow field variation of the visible plume region and the plume rise around the buildings with reasonable accuracy.

Wind Tunnel Test of Honeycomb in Improving Flow Quality

2013 ◽  
Vol 774-776 ◽  
pp. 275-278
Author(s):  
Chun Guang Li ◽  
Yang Liu ◽  
John.C.K. Cheung
Keyword(s):  
Wind Tunnel ◽  
Cell Size ◽  
Turbulence Intensity ◽  
Wind Tunnel Test ◽  
Open Loop ◽  
Incoming Flow ◽  
Flow Quality ◽  
The Mean ◽  
Square Cells ◽  
Change Tendency

The function of honeycomb with different length and width in improving flow quality were studied in the course of building a new small section open loop wind tunnel. Instantaneous velocities of turbulent flow in the tunnel were measured by cobra probe. The focus of this study was put on the effect of the honeycomb in attenuating the total turbulence intensity including the free-turbulence carried by the incoming flow and the turbulence generated by the square cells themselves. The change tendency of the mean wind velocity and the total turbulence characteristics in the decay area have been studied by varying the length to cell size ratio L/D, and ratio of distance between the square cells and the measuring position to cell size X/D.

Control of separation in the concave portion of contraction to improve the flow quality

2009 ◽  
Vol 113 (1141) ◽  
pp. 177-182 ◽  
Author(s):  
K. Ghorbanian ◽  
M. R. Soltani ◽  
M. D. Manshadi ◽  
M. Mirzaei
Keyword(s):  
Wind Tunnel ◽  
Pressure Distribution ◽  
Turbulence Intensity ◽  
Test Section ◽  
Adverse Pressure Gradient ◽  
Wind Tunnel Experiments ◽  
Free Stream Turbulence ◽  
Static Pressure Distribution ◽  
Subsonic Wind Tunnel ◽  
Flow Quality

AbstractSubsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip strip. The results confirm the significant impact of the tripped boundary layer on the control of adverse pressure gradient. The trip strip atX/L= 0.115 improves pressure distribution in contraction and reduces turbulence intensity in the test section, considerably.

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