Observational study of power-law approximation of wind profiles within an urban boundary layer for various wind conditions

Kikumoto, Hideki; Ooka, Ryozo; Sugawara, Hirofumi; Lim, Jongyeon

doi:10.1016/j.jweia.2017.02.003

Cited by 60 publications

(18 citation statements)

References 33 publications

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“…Their analysis reveals that the absolute difference in wind directions between the full-scale measurement heights of 25 m and 500 m can be as large as 40°i rrespective to wind speeds, in which the yaw angles were measured. Apparently, the wind directional deviations observed from the wind tunnel tests are smaller than those reported by Peña et al [13] and Kikumoto et al [14]. Nevertheless, the deviation can still be considered as significant when considering that its magnitude is larger than that of the Ekman Spiral and the deviation is confined to the lower 500 m of the ABL.…”

Section: Twisted Wind Profiles and Their Existence In Hong Kongmentioning

confidence: 51%

“…In the ABL, the wind profiles often have different flow directions at different heights, as confirmed by mathematical models [22,23] and field observations [13,14,24]. The vertical variation in flow directions is a result of the combined effects of Earth's rotation, friction between the wind and Earth's surface, and the pressure gradient force between high-and low-pressure zones [13].…”

Section: Twisted Wind Profiles and Their Existence In Hong Kongmentioning

confidence: 89%

“…However, deviations in wind direction observed in field measurement campaigns are larger than the average deviation in wind direction of the Ekman Spiral and are confined to the lower altitudes in the ABL (as opposed to all along its height). For example, Wind-Lidar measurements taken by Peña et al [13] reveal 25°-45°deviations in wind direction under the neutral and stable atmospheric conditions while Kikumoto et al [14] report about 70°of the deviations in wind direction for the heights in between 67.5 m and 500 m from SODAR-Lidar measurements.…”

Section: Twisted Wind Profiles and Their Existence In Hong Kongmentioning

confidence: 99%

“…For instance, the shape of the power-law wind model can become distorted because of Urban Heat Island (UHI) effect [11] and the development of an internal boundary layer [12]. Similarly, the assumption of the constant wind direction along the profiles' height is doubtful in the urban wind field [13,14]. Compared to wind speed and turbulence, the variation in wind directions has not received much attention even though several researchers, such as Kikumoto et al [14] have emphasised that the deviation in wind directions should be replicated accurately in both physical and numerical simulations to obtain precise results when studying urban wind fields.…”

Section: Introductionmentioning

confidence: 99%

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A wind tunnel study of effects of twisted wind flows on the pedestrian-level wind field in an urban environment

Weerasuriya

Tse

Zhang

et al. 2018

Building and Environment

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The influence of twisted wind flows on the pedestrian-level wind (PLW) field of an urban area was evaluated by testing a typical urban site (Tsuen Wan, Hong Kong) in a boundary layer wind tunnel. Four twisted wind profiles with different magnitudes and directions of yaw angles were employed to investigate variations in wind speed with the properties of the twisted wind flows at the pedestrian level. An additional conventional wind profile with similar wind speeds and turbulence intensities to the twisted winds but with zero yaw angles was simulated for comparisons. The mean wind speeds at 77 locations including the perimeter, roadsides, and groups of highrise buildings were analysed for the conventional and the four twisted wind flows. The comparisons show a tendency of twisted winds to generate higher wind speeds at the pedestrian level than the conventional wind profile. The wind speeds of the twisted winds have a strong dependence on the magnitude and direction of the yaw angles, particularly at locations where the densities of buildings in the neighbourhood are low and hence local wind circulations are significantly modified by the twisted winds.

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Section: Twisted Wind Profiles and Their Existence In Hong Kongmentioning

confidence: 51%

Section: Twisted Wind Profiles and Their Existence In Hong Kongmentioning

confidence: 89%

Section: Twisted Wind Profiles and Their Existence In Hong Kongmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A wind tunnel study of effects of twisted wind flows on the pedestrian-level wind field in an urban environment

Weerasuriya

Tse

Zhang

et al. 2018

Building and Environment

View full text Add to dashboard Cite

show abstract

“…It was found that when the mean wind speed at 50 m was less than 4 m/s, the wind direction changed frequently due to thermal effects, while the variability of the wind direction was small when the wind speed exceeded 10 m/s [157]. To better estimate approaching wind velocity in wind-driven ventilation assessment, a Doppler LiDAR was placed on a building rooftop in Tokyo to determine the wind profile [158,159]. It was found that the power law index for estimating the potential of natural ventilation was time dependent, having a value of 0.2-0.3 in evenings, nights and mornings, but decreasing to less than 0.1 during daytime because of the diurnal cycle in convection [158].…”

Section: Urban Meteorologymentioning

confidence: 99%

A Review of Progress and Applications of Pulsed Doppler Wind LiDARs

et al. 2019

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Doppler wind LiDAR (Light Detection And Ranging) makes use of the principle of optical Doppler shift between the reference and backscattered radiations to measure radial velocities at distances up to several kilometers above the ground. Such instruments promise some advantages, including its large scan volume, movability and provision of 3-dimensional wind measurements, as well as its relatively higher temporal and spatial resolution comparing with other measurement devices. In recent decades, Doppler LiDARs developed by scientific institutes and commercial companies have been well adopted in several real-life applications. Doppler LiDARs are installed in about a dozen airports to study aircraft-induced vortices and detect wind shears. In the wind energy industry, the Doppler LiDAR technique provides a promising alternative to in-situ techniques in wind energy assessment, turbine wake analysis and turbine control. Doppler LiDARs have also been applied in meteorological studies, such as observing boundary layers and tracking tropical cyclones. These applications demonstrate the capability of Doppler LiDARs for measuring backscatter coefficients and wind profiles. In addition, Doppler LiDAR measurements show considerable potential for validating and improving numerical models. It is expected that future development of the Doppler LiDAR technique and data processing algorithms will provide accurate measurements with high spatial and temporal resolutions under different environmental conditions.

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Modelling wind speed across Zambia: Implications for wind energy

Libanda¹,

Paeth²

2022

Intl Journal of Climatology

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Wind energy is a key option in global dialogues about climate change mitigation. Here, we combined observations from surface wind stations, reanalysis datasets, and state‐of‐the‐art regional climate models from the Coordinated Regional Climate Downscaling Experiment (CORDEX Africa) to study the current and future wind energy potential in Zambia. We found that winds are dominated by southeasterlies and are rarely strong with an average speed of 2.8 m·s−1. When we converted the observed surface wind speed to a turbine hub height of 100 m, we found a ~38% increase in mean wind speed for the period 1981–2000. Further, both simulated and observed wind speed data show statistically significant increments across much of the country. The only areas that divert from this upward trend of wind speeds are the low land terrains of the Eastern Province bordering Malawi. Examining projections of wind power density (WPD), we found that although wind speed is increasing, it is still generally too weak to support large‐scale wind power generation. We found a meagre projected annual average WPD of 46.6 W·m−2. The highest WPDs of ~80 W·m−2 are projected in the northern and central parts of the country while the lowest are to be expected along the Luangwa valley in agreement with wind speed simulations. On average, Zambia is expected to experience minor WPD increments of 0.004 W·m−2 per year from 2031 to 2050. We conclude that small‐scale wind turbines that accommodate cut‐in wind speeds of 3.8 m·s−1 are the most suitable for power generation in Zambia. Further, given the limitations of small wind turbines, they are best suited for rural and suburban areas of the country where obstructions are few, thus making them ideal for complementing the government of the Republic of Zambia's rural electrification efforts.

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Observational study of power-law approximation of wind profiles within an urban boundary layer for various wind conditions

Cited by 60 publications

References 33 publications

A wind tunnel study of effects of twisted wind flows on the pedestrian-level wind field in an urban environment

A wind tunnel study of effects of twisted wind flows on the pedestrian-level wind field in an urban environment

A Review of Progress and Applications of Pulsed Doppler Wind LiDARs

Modelling wind speed across Zambia: Implications for wind energy

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