scholarly journals An Analytical Framework for the Investigation of Tropical Cyclone Wind Characteristics over Different Measurement Conditions

2019 ◽  
Vol 9 (24) ◽  
pp. 5385 ◽  
Author(s):  
Lixiao Li ◽  
Yizhuo Zhou ◽  
Haifeng Wang ◽  
Haijun Zhou ◽  
Xuhui He ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Field Measurements ◽  
Analytical Framework ◽  
Reference Station ◽  
Complex Flow ◽  
Integral Scale ◽  
Gust Factor ◽  
Wind Characteristics ◽  
Averaging Time ◽  
Complex Flow Structure

Wind characteristics (e.g., mean wind speed, gust factor, turbulence intensity and integral scale, etc.) are quite scattered in different measurement conditions, especially during typhoon and/or hurricane processes, which results in the structural engineer ambiguously determining the wind parameters in wind-resistant design of buildings and structures in cyclone-prone regions. In tropical cyclones (including typhoons and hurricanes), the inconsistent wind characteristics may be in part ascribed to the complex flow structure with the coexistence of both mechanical and convective turbulence in the boundary layer of tropical cyclones. Another significant contribution to the scattered wind characteristics is due to various measurement conditions (e.g., terrain exposure and height) and data processing schemes (e.g., averaging time). The removal of the inconsistency in the field-measurement system may offer a more rational comparison of measured wind data from various observation platforms, and hence facilitates a better identification scheme of the wind characteristics to guide the urban planning design and wind-resistant design of buildings and structures. In this study, an analytical framework was firstly proposed to eliminate the potential observation-related effects in wind characteristics and then the wind characteristics of seven field measured tropical cyclones (four typhoons and three hurricanes) were comparatively investigated. Specifically, field measurements of wind characteristics were converted to a standard reference station with a roughness length of 0.03 m, observation duration of 10 min for mean wind and averaging time of 3 s for gusty wind at a 10 m height. The differences of the measured wind characteristics between the typhoons and hurricanes were highlighted. The standardized turbulent wind characteristics under the analytical framework for typhoons and hurricanes were compared with the corresponding recommendations in standard of American Society of Civil Engineers (ASCE 7-10) and Architectural Institute of Japan Recommendations for Loads on Buildings (AIJ-RLB-2004).

scholarly journals Turbulent wind characteristics in typhoon Hagupit based on field measurements

2018 ◽  
Vol 14 (10) ◽  
pp. 155014771880593 ◽  
Author(s):  
Lixiao Li ◽  
Yiqing Xiao ◽  
Haijun Zhou ◽  
Feng Xing ◽  
Lili Song
Keyword(s):  
Drag Coefficient ◽  
Large Scale ◽  
Field Measurements ◽  
Sea Surface ◽  
Back Side ◽  
Integral Scale ◽  
Gust Factor ◽  
Peak Factor ◽  
Wind Speeds ◽  
Wind Characteristics

Wind loads are the dominant loads for large-scale buildings and structures in tropical cyclone-prone regions; however, wind characteristics in tropical cyclones are still far from being understood. In this study, wind characteristics concerned in engineering applications, for example, wind attack angle, friction velocity, drag coefficient, turbulence intensity, integral scale, gust factor, and peak factor, were carefully investigated based on field measurements in typhoon Hagupit and were compared with measurements in typhoon Maemi and three hurricanes in literatures. The results show that drag coefficient increases with mean wind speeds at low levels and then decreases gradually at wind speed greater than 22.45 m/s in typhoon Hagupit over sea surface; turbulence intensities in front-side eyewall region are greater than those in back-side eyewall regions both in typhoons and hurricanes; the ratio between longitudinal integral scale and lateral integral scale, [Formula: see text], is scattered, but the ratio between longitudinal integral scale and vertical integral scale, [Formula: see text], is closer both in typhoons and hurricanes; the gust factor in typhoon Hagupit is 1.25 over open sea surface and 1.42 over open flat terrain; the peak factor is about 2.4.

A comparison study on gust factor considering non-stationary effects under typhoon and monsoon conditions

2018 ◽  
Vol 21 (12) ◽  
pp. 1853-1864 ◽  
Author(s):  
Shouqiang Wang ◽  
Lin Zhao ◽  
Shuyang Cao ◽  
Yufeng Zhang ◽  
Feng Yin ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Field Measurements ◽  
Stationary Model ◽  
Gust Factor ◽  
Wind Speeds ◽  
Turbulence Flow ◽  
Mean Wind Speed ◽  
Averaging Time ◽  
Monsoon Winds ◽  
The Relationship

This article studies the feasibility and effectiveness of a non-stationary model using field measurements. Gust factors are compared for both typhoon and monsoon winds whose maximum 10-min mean wind speeds were all greater than 20 m/s using non-stationary models. Wind speeds were recorded by three-dimensional anemometers by the Structural Health Monitoring System of Xihoumen Bridge. The study focuses on the dependences of gust factor on gust averaging time, sample duration, and mean wind speed for both typhoon and monsoon climates. The gust factor curve and the relationship between gust factor and turbulence intensity are also studied. The results suggest that a non-stationary model is more suitable for actual turbulence flow, particularly under typhoon conditions. The article also compares resulting gust factor curves with those obtained in former studies and shows that accurate gust factor curves can be obtained by field measurements for monsoon wind. It is thus recommended that gust factor research should differentiate between typhoon and monsoon winds.

Whole Process Wind Characteristics Field Measurements of a Strong Wind

2011 ◽  
Vol 243-249 ◽  
pp. 5094-5100 ◽  
Author(s):  
Ke Yang ◽  
Wen Hai Shi ◽  
Zheng Nong Li
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Field Measurements ◽  
Integral Length Scale ◽  
Length Scale ◽  
Strong Wind ◽  
Gust Factor ◽  
Mean Wind Speed ◽  
Wind Characteristics ◽  
The Mean

This paper presents field measurement results of boundary layer wind characteristics over typical open country during the passages of typhoon Fung-wong passed by Wenzhou in July 2008. The field data such as wind speed and wind direction were measured from two propeller anemometers placed at the height of about 30m. The measured wind data are analyzed to obtain the information on mean wind speed and direction, turbulence intensity, gust factor, turbulence integral length scale and spectra of wind speed fluctuations. The results clearly demonstrate that the turbulence intensity and gust factor of typhoon Fung-wong are larger than normal, and there is a tendency for the turbulence intensities to decrease with the increase of the mean wind speed, however, there is another tendency for the turbulence integral length scale to increase with the increase of the mean wind speed. The power spectral densities of fluctuating wind speed in longitudinal and lateral directions obtained from the measured wind speed data roughly fit with Von Karman spectra. The results presented in this paper are expected to be of use to researchers and engineers involved in design of low-rise buildings.

scholarly journals Full-Scale Measurements of Wind Characteristics on a High-Rise Building during Typhoon Sarika

2021 ◽  
Vol 12 (1) ◽  
pp. 324
Author(s):  
Jiaxing Hu ◽  
Zhengnong Li ◽  
Zhefei Zhao
Keyword(s):  
Wind Speed ◽  
Wind Field ◽  
Full Scale ◽  
Integral Scale ◽  
Gust Factor ◽  
Time Frequency ◽  
High Rise ◽  
High Rise Building ◽  
Wind Characteristics ◽  
Stationarity Test

A full-scale measurement of wind characteristics atop a high-rise building (with a height of 115 m) was conducted during the passage of Typhoon Sarika on 18 October 2016. Wind field characteristics, wind speed, and wind direction atop the building were recorded synchronously, and turbulence intensity, turbulence integral scale, gust factor, and power spectrum were investigated. Meanwhile, the time and frequency domain characteristics of the wind field were analyzed. The stationarity test results of Typhoon Sarika at different time steps are researched in a runs test. And the time-frequency analysis of non-stationary samples of fluctuating wind speed are conducted by wavelet transform, the measured data are valuable for the wind-resistant design of high-rise buildings in typhoon-prone regions.

scholarly journals Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

2021 ◽  
Author(s):  
Fabian Burmann ◽  
Jerome Noir ◽  
Stefan Beetschen ◽  
Andrew Jackson
Keyword(s):  
Acoustic Waves ◽  
Flow Measurement ◽  
Low Cost ◽  
Time Of Flight ◽  
Zonal Flow ◽  
Gravitational Acceleration ◽  
Complex Flow ◽  
Ultrasonic Time ◽  
Theoretical Predictions ◽  
Complex Flow Structure

AbstractMany common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

scholarly journals A Field Measurement Based Wind Characteristics Analysis of a Typhoon in Near-Ground Boundary Layer

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 873
Author(s):  
Dandan Xia ◽  
Liming Dai ◽  
Li Lin ◽  
Huaifeng Wang ◽  
Haitao Hu
Keyword(s):  
Turbulence Intensity ◽  
Field Measurement ◽  
Three Dimensional ◽  
Wind Data ◽  
Statistical Characteristics ◽  
Gust Factor ◽  
Characteristics Analysis ◽  
Wind Characteristics ◽  
The Mean ◽  
The Relationship

The field measurement was conducted to observe the wind field data of West Pacific typhoon “Maria” in this research. With the application of ultrasonic anemometers installed in different heights (10 m, 80 m, 100 m) of the tower, the three dimensional wind speed data of typhoon “Maria” was acquired. In addition, vane-type anemometers were installed to validate the accuracy of the wind data from ultrasonic anemometers. Wind characteristics such as the mean wind profile, turbulence intensity, integral length scale, and wind spectrum are studied in detail using the collected wind data. The relationship between the gust factor and turbulence intensity was also studied and compared with the existing literature to demonstrate the characteristics of Maria. The statistical characteristics of the turbulence intensity and gust factor are presented. The corresponding conclusion remarks are expected to provide a useful reference for designing wind-resistant buildings and structures.

scholarly journals Experimental Study on Wake Evolution of a 1.5 MW Wind Turbine in a Complex Terrain Wind Farm Based on LiDAR Measurements

2020 ◽  
Vol 12 (6) ◽  
pp. 2467 ◽  
Author(s):  
Fei Zhao ◽  
Yihan Gao ◽  
Tengyuan Wang ◽  
Jinsha Yuan ◽  
Xiaoxia Gao
Keyword(s):  
Wind Speed ◽  
Wind Shear ◽  
Wind Farm ◽  
Wind Farms ◽  
Field Measurements ◽  
Development Trend ◽  
Asymmetric Distribution ◽  
Lidar Measurements ◽  
Wind Characteristics ◽  
The Development Trend

To study the wake development characteristics of wind farms in complex terrains, two different types of Light Detection and Ranging (LiDAR) were used to conduct the field measurements in a mountain wind farm in Hebei Province, China. Under two different incoming wake conditions, the influence of wind shear, terrain and incoming wind characteristics on the development trend of wake was analyzed. The results showed that the existence of wind shear effect causes asymmetric distribution of wind speed in the wake region. The relief of the terrain behind the turbine indicated a subsidence of the wake centerline, which had a linear relationship with the topography altitudes. The wake recovery rates were calculated, which comprehensively validated the conclusion that the wake recovery rate is determined by both the incoming wind turbulence intensity in the wake and the magnitude of the wind speed.

Fluid Flow Structure in Arterial Bypass Anastomosis

2005 ◽  
Vol 127 (4) ◽  
pp. 611-618 ◽  
Author(s):  
C. M. Su ◽  
D. Lee ◽  
R. Tran-Son-Tay ◽  
W. Shyy
Keyword(s):  
Fluid Flow ◽  
Flow Structure ◽  
Bypass Graft ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Arterial Bypass ◽  
Flow Recirculation ◽  
Area Reduction ◽  
Complex Flow Structure

The fluid flow through a stenosed artery and its bypass graft in an anastomosis can substantially influence the outcome of bypass surgery. To help improve our understanding of this and related issues, the steady Navier-Stokes flows are computed in an idealized arterial bypass system with partially occluded host artery. Both the residual flow issued from the stenosis—which is potentially important at an earlier stage after grafting—and the complex flow structure induced by the bypass graft are investigated. Seven geometric models, including symmetric and asymmetric stenoses in the host artery, and two major aspects of the bypass system, namely, the effects of area reduction and stenosis asymmetry, are considered. By analyzing the flow characteristics in these configurations, it is found that (1) substantial area reduction leads to flow recirculation in both upstream and downstream of the stenosis and in the host artery near the toe, while diminishes the recirculation zone in the bypass graft near the bifurcation junction, (2) the asymmetry and position of the stenosis can affect the location and size of these recirculation zones, and (3) the curvature of the bypass graft can modify the fluid flow structure in the entire bypass system.

Natural Convection in a Horizontal Cavity Partially Occupied by a Porous Media Saturated by a Coolant Liquid

2006 ◽  
Author(s):  
Fakhreddine S. Oueslati ◽  
Rachid Bennacer ◽  
Habib Sammouda ◽  
Ali Belghith
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Natural Convection ◽  
Flow Structure ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Heat Fluxes ◽  
Complex Flow ◽  
Coupled Equations ◽  
Complex Flow Structure

The natural convection is studied in a cavity witch the lower half is filled with a porous media that is saturated with a first fluid (liquid), and the upper is filled with a second fluid (gas). The horizontal borders are heated and cooled by uniform heat fluxes and vertical ones are adiabatic. The formulation of the problem is based on the Darcy-Brinkman model. The density variation is taken into account by the Boussinesq approximation. The system of the coupled equations is resolved by the classic finite volume method. The numerical results show that the variation of the conductivity of the porous media influences strongly the flow structure and the heat transfer as well as in upper that in the lower zones. The effect of conductivity is conditioned by the porosity which plays a very significant roll on the heat transfer. The structures of this flow show that this kind of problem with specific boundary conditions generates a complex flow structure of several contra-rotating two to two cells, in the upper half of the cavity.

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