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 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.

Influence of elevated water levels on wind field characteristics at a bridge site

2019 ◽  
Vol 22 (7) ◽  
pp. 1783-1795 ◽  
Author(s):  
Hongmiao Jing ◽  
Haili Liao ◽  
Cunming Ma ◽  
Kejian Chen
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Water Level ◽  
Wind Field ◽  
Wind Profile ◽  
Water Levels ◽  
Bridge Engineering ◽  
Bridge Site ◽  
Bridge Girder ◽  
Elevated Water

The influence of elevated water levels on wind field characteristics at bridge sites owing to hydroelectric power stations plays an important role in bridge engineering, particularly in mountainous valley regions. To investigate this issue, a comparative experimental study, which uses a topographic model with two water level states for determining the influence on wind field characteristics at the proposed bridge site located in a mountainous valley area, was conducted in the XNJD-3 wind tunnel at Southwest Jiaotong University, Chengdu, PR China. The altitude difference between the two water level states was approximately 200 m, whereas uniform and D-type boundary layer air inflow conditions were adopted during the wind tunnel test, respectively. The wind speed at the bridge girder and profile of the 1/4, mid, and 3/4 spans were recorded during the experiment. The test results indicated that after the water level was raised, the mean wind speed (or speed-up factor) along the bridge girder decreased by approximately 10%, and the values of the wind profile also decreased. However, the wind profile curve shapes remained approximately unchanged, and the wind attack angle was significantly transformed by approximately 5° in certain locations of the bridge girder. Moreover, the variation in the water level had a negligible influence on the turbulence intensities, turbulence integral length scales, probability distribution of fluctuating wind components, and turbulent wind spectra along the bridge girder. Therefore, as the water level in the canyon rises, the wind field characteristics at the bridge site tend to be conducive to bridge safety. Therefore, long-span bridges located in mountainous valley areas should be designed appropriately according to the expected minimum water level of the river.

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>

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.

scholarly journals The quantification of NO<sub><i>x</i></sub> and SO<sub>2</sub> point source emission flux errors of mobile DOAS on the basis of the Gaussian dispersion model: A simulation study

2020 ◽  
Author(s):  
Yeyuan Huang ◽  
Ang Li ◽  
Thomas Wagner ◽  
Yang Wang ◽  
Zhaokun Hu ◽  
...  
Keyword(s):  
Point Source ◽  
Wind Field ◽  
Point Sources ◽  
Emission Source ◽  
Emission Flux ◽  
Error Source ◽  
Error Budget ◽  
So2 Flux ◽  
Main Error ◽  
Ratio Correction

Abstract. Mobile differential optical absorption spectroscopy (mobile DOAS) has become an important tool for the quantification of emission sources, including point sources (e.g., individual power plants) and area emitters (e.g., entire cities). In this study, we focused on the error budget of mobile DOAS measurements from point sources, and we also offered recommendations for the optimum settings of such measurements. First we established a Gaussian plume model from which the NOx and SO2 distribution from the point source was determined. In a second step the simulated distributions are converted into vertical column densities of NOx and SO2 according to the mobile DOAS measurement technique. With assumed parameters, we then drove the forward model in order to simulate the emissions, after which we performed the analysis. Following this analysis, we conclude that: (1) Larger sampling resolution clearly results in larger flux error. The proper resolution we suggest is between 5 m and 50 m. Even larger resolutions may also be viable, but > 100 m is not recommended. (2) Error effects vary with measurement distance from the source. We found that undetectable flux (measured VCDs are under the detection limit) is the main error source when measuring far from the source, for both NOx and SO2. When measuring close to the source, low sampling frequency results in large flux error. (3) The wind field primarily affects 2 aspects of the flux measurement error. When measuring far from the source, dispersion results in more undetectable flux, which is the main error source. When measuring close to the source, wind field uncertainty becomes the main error source of SO2 flux, but not of NOx. We suggested that the proper wind speed for mobile DOAS measurements is between 1 m/s and 4 m/s. (4) The study of NOx atmospheric chemistry reactions indicated that a [NOx]/[NO2] ratio correction has to be applied when measuring very close to the emission source. But even when such a correction is applied, the remaining errors can be significant. To minimize the [NOx]/[NO2] ratio correction error, we recommended 0.05 NO2 maximum reaction rate as the accepted NOx steady-state thus to determine the proper starting measurement distance. (5) The error of the spectral retrieval is not a main emission flux error source and its error budget varies with the measuring distance. (6) Increasing the number of measurements can lower the flux error that results from wind field uncertainty and retrieval error. This directly indicates that SO2 flux error could be lowered if the measurements are repeated when not too far from the emission source. With regard to NOx, more measurement times can only work effectively when not very close or too far from the source. (7) Also the effects of the temporal and spatial sampling are investigated. When the sampling resolution is prescribed, the integration depends on the driving speed and the corresponding flux error is mainly determined by the undetectable flux. When the car speed is prescribed, the integration time is determined by the sampling resolution for measuring near the source, while undetectable flux predominates when far away. (8) As a general recommendation, our study suggests that emission rates < 30 g/s for NOx and < 50 g/s for SO2 are not recommended for mobile DOAS measurements. The source height affects the undetectable flux, but has little influences on the total error. Based on the model simulations our study indicates that mobile DOAS measurements are very well suited tool to quantify point source emissions. The results of our sensitivity studies are important to make optimum use of such measurements.

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 Variations in Friction Velocity with Wind Speed and Height for Moderate-to-Strong Onshore Winds Based on Measurements from a Coastal Tower

2020 ◽  
Vol 59 (4) ◽  
pp. 637-650 ◽  
Author(s):  
Pingzhi Fang ◽  
Wendong Jiang ◽  
Jie Tang ◽  
Xiaotu Lei ◽  
Jianguo Tan
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Wind Speed ◽  
Wind Direction ◽  
Friction Velocity ◽  
Wind Profile ◽  
Wind Data ◽  
Profile Data ◽  
Onshore Wind ◽  
Critical Wind Speed

AbstractVariations in friction velocity with wind speed and height are studied under moderate (≥9 m s−1)-to-strong onshore wind conditions caused by three landfalling typhoons. Wind data are from a coastal 100-m tower equipped with 20-Hz ultrasonic anemometers at three heights. Results show that wind direction affects variations in friction velocity with wind speed. A leveling off or decrease in friction velocity occurs at a critical wind speed of ~20 m s−1 under strong onshore wind conditions. Friction velocity does not always decrease with height in the surface layer under typhoon conditions. Thus, height-based corrections on friction velocities using the model from Anctil and Donelan may not be reliable. Surface-layer heights predicted by the model that are based on Ekman dynamics are verified by comparing with those determined by a proposed method that is based on the idea of mean boundary layer using wind-profile data from one of the landfalling typhoons. Friction velocity at the top of the surface layer is then estimated. Results show that friction velocity decreases by about 20% from its surface value and agrees well with previous results of Tennekes.

scholarly journals Field Measurements of Hanging Flight Aerodynamics in the Kestrel Falco Tinnunculus

1991 ◽  
Vol 155 (1) ◽  
pp. 519-530
Author(s):  
JOHN VIDELER ◽  
ALEX GROENEWOLD
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Wind Profile ◽  
Field Measurements ◽  
Vertical Wind ◽  
Horizontal Direction ◽  
Falco Tinnunculus ◽  
Windward Slope ◽  
Sea Dike

Hunting kestrels were observed to hang, almost without wing-flapping, in fixed positions over a sea dike. The height and position with respect to the dike profile, the wind direction and velocity and the percentage of hunting time without wing beating were recorded in 429 cases. The vertical wind angle, θ, the wind speed and its horizontal direction were measured at 13 heights up to 8.8m above the windward slope, the top and the leeward slope of the dike under various wind conditions in 225 cases. These wind profile measurements were used to estimate 6 and wind speed near the hanging birds. Kestrels hanging more than 90% of the hunting time preferred a position 6.5±1.5m (S.D.) over the windward slope with sea winds blowing at 8.7±1.5ms−1 (S.D.) perpendicular (±30°) to the longitudinal dike axis. For these birds angle θ was approximately 6–7°. These angles are larger than expected from aerodynamic models and windtunnel measurements. The minimum gliding angle for a kestrel under steady conditions is estimated to be 5°. Hanging kestrels save two-thirds of the energy used during normal windhovering but have to spend 1.6 times more time to catch the same number of voles.

scholarly journals The Effect of the Surface Wind Field Representation in the Operational Storm Surge Model of the National Hurricane Center

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 193 ◽  
Author(s):  
Talea Mayo ◽  
Ning Lin
Keyword(s):  
Wind Speed ◽  
Storm Surge ◽  
Wind Field ◽  
Wind Profile ◽  
Storm Surges ◽  
Maximum Wind Speed ◽  
Field Representation ◽  
Maximum Wind ◽  
National Hurricane Center ◽  
Surface Background

The Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model is the operational storm surge model of the National Hurricane Center (NHC). Previous studies have found that the SLOSH model estimates storm surges with an accuracy of ±20%. In this study, through hindcasts of historical storms, we assess the accuracy of the SLOSH model for four coastal regions in the Northeastern United States. We investigate the potential to improve this accuracy through modification of the wind field representation. We modify the surface background wind field, the parametric wind profile, and the maximum wind speed based on empirical, physical, and observational data. We find that on average the SLOSH model underestimates maximum storm surge heights by 22%. The modifications to the surface background wind field and the parametric wind profile have minor impacts; however, the effect of the modification to maximum wind speed is significant—it increases the variance in the SLOSH model estimates of maximum storm surges, but improves its accuracy overall. We recommend that observed values of maximum wind speed be used in SLOSH model simulations when possible.

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