The Change of Aerodynamic Parameters over Beijing Urban Area during 1991-2018

2020 ◽  
Author(s):  
Xiaoman Liu
Keyword(s):  
Wind Speed ◽  
Urban Area ◽  
Wind Direction ◽  
Wind Field ◽  
Atmospheric Stability ◽  
Meteorological Condition ◽  
Field Structure ◽  
Average Height ◽  
Growth Trend ◽  
Aerodynamic Parameters

<p>       Higher and denser building groups are the most concentrated reflection of urbanization on the underlying surface reconstruction. With the continuous city expanding, urban wind field structure was changed, also the aerodynamic parameters dependent on. Based on observational data (slow-response) collected at 15 levels on Beijing 325m meteorological tower from 1991-2018, time and vertical trends of atmospheric stability, wind direction, wind speed, aerodynamic parameters were analyzed. Through Sen's slope, Mann-Kendall trend test and mutation analysis, we believe that urbanization has made a significant influence on local meteorological condition, and all the above variables mutated around the year of 1999. Before 1999, the proportion of neutral and unstable conditions declined with a trend of -0.63% and -2.0% per year respectively, and increased with a trend of +0.08% and +0.06% per year after 1999. As for wind direction, the dominant wind direction below 47m turned from southwest/northwest before 1999 to southeast after 1999, while above 47m remain unchanged as southeast, reflecting that the action range of urban impact is clearly distinguished from that of atmospheric background field. In terms of wind speed, the annual mean value trended to decrease at -0.0019m/s per year, and vertical wind speed trended to increased with height (per meter) at m/s per year, which reflected the continuous enhancement of attenuation effect of complex underlying on the near-ground wind speed. Furthermore, we found that although there was indeed a weaken tendency for wind speed in Beijing urban areas, but near neutral wind speed maintained a growth trend under 140m during 1999-2018. It was possible the deal with urban wake effect, wind field structure mutation or turbulence effect. Aerodynamic parameters  and d have undergone significant changes during the peak stage of urbanization, and tended to develop steadily with a 7-years fluctuations trend after that. In the past 28 years, d has increased from 1.34m in 1991 to 26.19m in 2018, while  has decreased from 2.75m to 1.02m. This is due to the fact that the increase of buildings average height is the result of roughness superposition. If the 7-year fluctuations trend continues, d of Beijing urban area will soon enter the next uplift period, during which the wind speed may increase slightly under nearly neutral conditions, and the cleaning effect on the pollution may be gradually enhanced.</p><p> </p>

scholarly journals Influence of Wind Speed, Wind Direction and Turbulence Model for Bridge Hanger: A Case Study

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1633
Author(s):  
Yang Ding ◽  
Shuang-Xi Zhou ◽  
Yong-Qi Wei ◽  
Tong-Lin Yang ◽  
Jing-Liang Dong
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Wind Field ◽  
Solid Mechanics ◽  
Von Mises Stress ◽  
Long Span Bridges ◽  
High Rise ◽  
Long Span ◽  
Cfd Models ◽  
Von Mises

Wind field (e.g., wind speed and wind direction) has the characteristics of randomness, nonlinearity, and uncertainty, which can be critical and even destructive on a long-span bridge’s hangers, such as vortex shedding, galloping, and flutter. Nowadays, the finite element method is widely used for model calculation, such as in long-span bridges and high-rise buildings. In this study, the investigated bridge hanger model was established by COMSOL Multiphysics software, which can calculate fluid dynamics (CFD), solid mechanics, and fluid–solid coupling. Regarding the wind field of bridge hangers, the influence of CFD models, wind speed, and wind direction are investigated. Specifically, the bridge hanger structure has symmetrical characteristics, which can greatly reduce the calculation efficiency. Furthermore, the von Mises stress of bridge hangers is calculated based on fluid–solid coupling.

Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field

2020 ◽  
Author(s):  
Xinghong Cheng
Keyword(s):  
Spatial Distribution ◽  
Wind Speed ◽  
Wind Field ◽  
Meteorological Condition ◽  
Emission Rates ◽  
Wind Fields ◽  
Vertical Column ◽  
Wind Speeds ◽  
South Central ◽  
The Mean

<p>We carried out 14 days of Car MAX-DOAS experiments on the 6th Ring Rd of Beijing in January, September and October, 2014. The tropospheric vertical column densities (VCD) of NO<sub>2</sub> are retrieved and used to estimate the emissions of NO<sub>x</sub>. The offline LAPS-WRF-CMAQ model system is used to simulate wind fields by assimilation of observational data and calculate the NO<sub>2</sub> to NO<sub>x</sub> concentration ratios. The NO<sub>X</sub> emissions in Beijing for different seasons derived from Car MAX-DOAS measurements are compared with the multi-resolution emission inventory in China for 2012 (MEIC 2012), and impacts of wind field on estimated emissions and its uncertainties are also investigated. Results show that the NO<sub>2</sub> VCD is higher in January than other two months and it is typically larger at the southern parts of the 6th Ring Road than the northern parts of it. Wind field has obvious impacts on the spatial distribution of NO<sub>2</sub> VCD, and the mean NO<sub>2</sub> VCD with south wind at most sampling points along the 6th Ring Rd is higher than north wind. The journey-to-journey variation pattern of estimated NO<sub>X</sub> emissions rates (E<sub>NOX</sub>) is consistent with that of the NO<sub>2</sub> VCD, and E<sub>NOX </sub>is mainly determined by the NO2 VCD. In addition, the journey-to-journey E<sub>NOX</sub> in the same month is different and it is affected by wind speed, the ratio of NO<sub>2</sub> and NOx concentration and the decay rate of NO<sub>X</sub> from the emission sources to measured positions under different meteorological condition. The E<sub>NOX</sub> ranges between 6.46×10<sup>25</sup> and 50.05×10<sup>25</sup> molec s<sup>-1</sup>. The averaged E<sub>NOX</sub> during every journey in January, September and October are respectively 35.87×10<sup>25</sup>, 20.34×10<sup>25</sup>, 8.96×10<sup>25</sup> molec s<sup>-1</sup>. The estimated E<sub>NOX</sub> after removing the simulated error of wind speed and observed deviation of NO<sub>2</sub> VCD are found to be mostly closer to the MEIC 2012, but sometimes E<sub>NOX </sub>is lower or higher and it indicates that the MEIC 2012 might be overestimate or underestimate the true emissions. The estimated E<sub>NOX</sub> on January 27 and September 19 are obviously higher than other journeys in the same month because the mean NO<sub>2</sub> VCD and Leighton ratio during these two periods are larger, and corresponding wind speeds are smaller. Additionally, because south wind may affect the spatial distribution of mean NO<sub>2</sub> VCD in Beijing which is downwind of south-central regions of Hebei province with high source emission rates, the uncertainty of the estimated E<sub>NOX</sub> with south wind will be increased.</p>

Wind tunnel tests on the characteristics of wind fields over a simplified gorge

2016 ◽  
Vol 20 (10) ◽  
pp. 1599-1611 ◽  
Author(s):  
Peng Hu ◽  
Yongle Li ◽  
Yan Han ◽  
CS Cai ◽  
Guoji Xu
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Direction ◽  
Wind Field ◽  
Small Range ◽  
Wind Fields ◽  
Wind Speeds ◽  
Mean Wind Speed ◽  
Wind Characteristics ◽  
The Mean

Characteristics of wind fields over the gorge or valley terrains are becoming more and more important to the structural wind engineering. However, the studies on this topic are very limited. To obtain the fundamental characteristics information about the wind fields over a typical gorge terrain, a V-shaped simplified gorge, which was abstracted from some real deep-cutting gorges where long-span bridges usually straddle, was introduced in the present wind tunnel studies. Then, the wind characteristics including the mean wind speed, turbulence intensity, integral length scale, and the wind power spectrum over the simplified gorge were studied in a simulated atmospheric boundary layer. Furthermore, the effects of the oncoming wind field type and oncoming wind direction on these wind characteristics were also investigated. The results show that compared with the oncoming wind, the wind speeds at the gorge center become larger, but the turbulence intensities and the longitudinal integral length scales become smaller. Generally, the wind fields over the gorge terrain can be approximately divided into two layers, that is, the gorge inner layer and the gorge outer layer. The different oncoming wind field types have remarkable effects on the mean wind speed ratios near the ground. When the angle between the oncoming wind and the axis of the gorge is in a certain small range, such as smaller than 10°, the wind fields are very close to those associated with the wind direction of 0°. However, when the angle is in a larger range, such as larger than 20°, the wind fields in the gorge will significantly change. The research conclusions can provide some references for civil engineering practices regarding the characteristics of wind fields over the real gorge terrains.

A practical framework using odor survey data to prioritize nuisance odors

2009 ◽  
Vol 59 (3) ◽  
pp. 595-602 ◽  
Author(s):  
G. A. Burlingame
Keyword(s):  
Wastewater Treatment ◽  
Wind Speed ◽  
Survey Data ◽  
Wind Direction ◽  
Wastewater Treatment Plant ◽  
Data Use ◽  
Atmospheric Stability ◽  
Treatment Plant

There are three main questions that need to be answered to address nuisance odors at the fenceline of a wastewater treatment plant: What odors are occurring at the fenceline of the plant? What processes within the plant give rise to these odors? What priority should we assign to mitigation of the nuisance odors? The prioritization is based on three factors that make odors a nuisance: strength or intensity of the odor when it is detected; quality or description of the odor; persistence or occurrence of the odor at the fenceline. Since fenceline odors vary according to: wind direction; wind speed; atmospheric stability and obstructions (buildings, trees, roadways), this study conducted odor surveys at the fenceline of a wastewater plant between April and November for 20 surveys. The data were used to develop a practical framework in three steps: summarize fenceline (residential vs non-residential) odor survey data; use odor type category and average odor strength to determine the annoyance factor; use annoyance factor and fenceline occurrence to determine the priority rating for nuisance odors to be mitigated.

scholarly journals A Method of Accelerating the Convergence of Computational Fluid Dynamics for Micro-Siting Wind Mapping

Computation ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 22 ◽  
Author(s):  
Kim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Wind Direction ◽  
Initial Conditions ◽  
Atmospheric Stability ◽  
Computation Time ◽  
Initial Condition ◽  
Simulation Domain ◽  
Computational Fluid Dynamics Cfd

To assess wind resources, a number of simulations should be performed by wind direction, wind speed, and atmospheric stability bins to conduct micro-siting using computational fluid dynamics (CFD). This study proposes a method of accelerating CFD convergence by generating initial conditions that are closer to the converged solution. In addition, the study proposes the ‘mirrored initial condition’ (IC) using the symmetry of wind direction and geography, the ‘composed IC’ using the vector composition principle, and the ‘shifted IC’ which assumes that the wind speed vectors are similar in conditions characterized by minute differences in wind direction as the well-posed initial conditions. They provided a significantly closer approximation to the converged flow field than did the conventional initial condition, which simply assumed a homogenous atmospheric boundary layer over the entire simulation domain. The results of this study show that the computation time taken for micro-siting can be shortened by around 35% when conducting CFD with 16 wind direction sectors by mixing the conventional and the proposed ICs properly.

scholarly journals Study on Wind Field Characteristics in a Coastal Plain Based on a New Three-Dimensional Joint Distribution Model

2021 ◽  
Vol 11 (19) ◽  
pp. 9114
Author(s):  
Xiaoyue Gao ◽  
Tianbao Xiao ◽  
Jiawu Li ◽  
Jianming Hao ◽  
Zhenxing Ma
Keyword(s):  
Wind Speed ◽  
Weibull Distribution ◽  
Coastal Plain ◽  
Wind Direction ◽  
Wind Field ◽  
Joint Distribution ◽  
Three Dimensional ◽  
Copula Function ◽  
Distribution Model ◽  
Joint Probability Distribution

This paper studied the joint probability distribution of wind speed, wind direction, and wind height. The measured wind field data of a coastal plain in Zhongshan city, Guangdong Province, China, were taken as the research object. A three-dimensional joint distribution modeling method, based on the copula function and the AL (angular–linear) model, is proposed. Firstly, the wind speed is modeled by the common distribution model, and the Weibull distribution is selected. Secondly, the mvM (mixed von Mises distribution) was used to fit the wind direction probability density, and the joint distribution of wind speed and wind direction was established based on the AL model. Finally, a three-dimensional joint distribution model of wind speed, wind direction, and height was established by considering the effect of height through the copula function. The results showed that Weibull distribution can better describe the wind speed distribution in this region. The north–south wind prevailed in this region, and the probability of the main wind direction decreased with the increase in height. The joint distribution of wind speed and direction, based on the AL model, fitted well with the measured data, and the final three-dimensional distribution model had a good fitting effect.

scholarly journals Wave Energy Disbalance as Generator of Extreme Wave Occurrence in Semi-Enclosed Coastal Waters (Example of Rijeka Bay—Croatia)

2019 ◽  
Vol 7 (11) ◽  
pp. 420
Author(s):  
Lončar ◽  
Leder ◽  
Leder ◽  
Carević
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Wind Direction ◽  
Wind Field ◽  
Wave Generation ◽  
Direct Application ◽  
Generation Model ◽  
Developed Surface ◽  
Sea Area ◽  
Adriatic Basin

The conditions for the occurrence of high waves in front of the Rijeka port in the Rijeka Bay were analyzed. The analysis was carried out on the basis of measured data on the wave rider station located in front of the main breakwater of the port of Rijeka and the results of numerical wave generation modelings for the wider sea area on the spatial scale of the Adriatic basin. The results of the conducted analysis show that the sudden transition in wind direction from the third to the second quadrant (and vice versa), with the simultaneous rapid increase in wind speed, creates the conditions for generating the largest waves in front of the port of Rijeka. The main reason for achieving the highest wave height in these conditions is the unbalanced wind power input with non-developed surface dissipation (white-capping) and quadruplet wave interaction. Situations with a slower increase in wind speed and approximately constant wind direction resulted in the occurrence of smaller wave heights. The direct application of anemometric data for the forcing wind field in the Adriatic basin within the wave generation model results in a more accurate simulation of wave height and wave period development than application of the wind field from the prediction atmospheric model Aladin-Hr. This is due to the fact that the site is located in a semi-enclosed sea area of restricted fetch, and the spatial/temporal resolution of atmospheric data (2 km and 3 h) is not sufficient to resolve the rapid transition in the wind field. In the case of direct application of anemometric data, the white-capping parameterization should be of a non-stationary character.

scholarly journals NOx Emission Flux Measurements with Multiple Mobile-DOAS Instruments in Beijing

2020 ◽  
Vol 12 (16) ◽  
pp. 2527
Author(s):  
Yeyuan Huang ◽  
Ang Li ◽  
Pinhua Xie ◽  
Zhaokun Hu ◽  
Jin Xu ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Wind Field ◽  
Wind Profile ◽  
Nox Emission ◽  
Nox Emissions ◽  
Emission Flux ◽  
Error Source ◽  
Flux Measurements ◽  
Mega Cities

NOX (NOX = NO + NO2) emissions measurements in Beijing are of great significance because they can aid in understanding how NOX pollution develops in mega-cities throughout China. However, NOX emissions in mega-cities are difficult to measure due to changes in wind patterns and moving sources on roads during measurement. To obtain good spatial coverage on different ring roads in Beijing over a short amount of time, two mobile differential optical absorption spectroscopy (DOAS) instruments were used to measure NOX emission flux from April 18th to 26th, 2018. In addition, a wind profile radar provided simultaneous wind field measurements for altitudes between 50 m and 1 km for each ring road measurement. We first determined NOX emission flux of different ring roads using wind field averages from measured wind data. The results showed that the NOX emission flux of Beijing’s fifth ring road, which represented the urban part, varied from (19.29 ± 5.26) × 1024 molec./s to (36.46 ± 12.86) × 1024 molec./s. On April 20th, NOX emission flux for the third ring was slightly higher than the fourth ring because the two ring roads were measured at different time periods. We then analyzed the NOX emission flux error budget and error sensitivity. The main error source was the wind field uncertainty. For some measurements, the main emission flux error source was either wind speed uncertainty or wind direction uncertainty, but not both. As Beijing’s NOX emissions came from road vehicle exhaust, we found that emission flux error had a more diverse sensitivity to wind direction uncertainty, which improved our knowledge on this topic. The NOX emission flux error sensitivity study indicated that more accurate measurements of the wind field are crucial for effective NOX emission flux measurements in Chinese mega-cities. Obtaining actual time and high resolved wind measurements is an advantage for mega-cities’ NOX emission flux measurements. The emission flux errors caused by wind direction and wind speed uncertainties were clearly distinguished. Other sensitivity studies indicated that NOX/NO2 ratio uncertainty dominated flux errors when the NOX/NO2 ratio uncertainty was >0.4. Using two mobile-DOAS and wind profile radars to measure NOx emission flux improved the quality of the emission flux measuring results. This approach could be applied to many other mega-cities in China and in others countries.

scholarly journals Automated wind turbine wake characterization in complex terrain

2019 ◽  
Vol 12 (6) ◽  
pp. 3463-3484 ◽  
Author(s):  
Rebecca J. Barthelmie ◽  
Sara C. Pryor
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Atmospheric Stability ◽  
Average Height ◽  
Data Set ◽  
Wind Speeds ◽  
Stable Conditions ◽  
Low Wind Speeds ◽  
Turbine Wake ◽  
Wind Turbine Wake

Abstract. An automated wind turbine wake characterization algorithm has been developed and applied to a data set of over 19 000 scans measured by a ground-based scanning Doppler lidar at Perdigão, Portugal, over the period January to June 2017. Potential wake cases are identified by wind speed, direction and availability of a retrieved free-stream wind speed. The algorithm correctly identifies the wake centre position in 62 % of possible wake cases, with 46 % having a clear and well-defined wake centre surrounded by a coherent area of lower wind speeds while 16 % have split centres or multiple lobes where the lower wind speed volumes are no longer in coherent areas but present as two or more distinct areas or lobes. Only 5 % of cases are not detected; the remaining 33 % could not be categorized either by the algorithm or subjectively, mainly due to the complexity of the background flow. Average wake centre heights categorized by inflow wind speeds are shown to be initially lofted (to two rotor diameters, D, downstream) except when the inflow wind speeds exceed 12 ms−1. Even under low wind speeds, by 3.5 D downstream of the wind turbine, the mean wake centre position is below the initial wind turbine hub height and descends broadly following the terrain slope. However, this behaviour is strongly linked to the hour of the day and atmospheric stability. Overnight and in stable conditions, the average height of the wake centre is 10 m higher than in unstable conditions at 2 D downstream from the wind turbine and 17 m higher at 4.5 D downstream.

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