Spatio-temporal modeling of the wind field over an urban lake subject to wind sheltering

2022 ◽  
Keyword(s):  
Wind Direction ◽  
Wind Field ◽  
Field Measurements ◽  
Structure Alignment ◽  
Urban Lake ◽  
Quality Model ◽  
Wind Model ◽  
Cfd Modelling ◽  
Prevailing Wind Direction ◽  
Spatio Temporal

Abstract The wind field over an urban lake may exhibit considerable variability due to wind shielding effects from surrounding structures. Field measurements at an urban reservoir in Singapore were augmented by computational fluid dynamics (CFD) model results to develop a wind model over the reservoir surface via a data assimilation approach. The field measurements identified, depending on structure alignment with the prevailing wind direction, wind shielding that impacted wind direction and velocity over the reservoir surface. The wind model integrated the temporal response of the measurements and spatial distribution produced by the CFD modelling. The wind model was used to predict the spatio-temporal pattern of the wind field over the reservoir surface for a full year. The modeling results showed good agreement with measured wind data at three measurement locations on the reservoir surface. The wind model has been incorporated with a hydrodynamics and water quality model to provide the spatio-temporal wind forcing over the reservoir surface.

scholarly journals Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source

2005 ◽  
Vol 5 (11) ◽  
pp. 2927-2934 ◽  
Author(s):  
L. J. Carpenter ◽  
D. J. Wevill ◽  
S. O'Doherty ◽  
G. Spain ◽  
P. G. Simmonds
Keyword(s):  
Boundary Layer ◽  
Wind Direction ◽  
Marine Boundary Layer ◽  
Land Breeze ◽  
Peat Bogs ◽  
Mixing Ratios ◽  
The North ◽  
Prevailing Wind Direction ◽  
Atmospheric Observations ◽  
Summer Minimum

Abstract. In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.

scholarly journals Modulation of urban atmospheric electric field measurements with the wind direction in Lisbon (Portugal)

2015 ◽  
Vol 646 ◽  
pp. 012013 ◽  
Author(s):  
H G Silva ◽  
J C Matthews ◽  
R Conceição ◽  
M D Wright ◽  
S N Pereira ◽  
...  
Keyword(s):  
Electric Field ◽  
Wind Direction ◽  
Field Measurements ◽  
Atmospheric Electric Field ◽  
Electric Field Measurements

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.

POD Analysis of the Impact Dynamics of the Olive Tree Branch: Nature’s Paradigm of a Complex Soft-Stiff Structural System in Biomechanics

2017 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Nonlinear Vibrations ◽  
Field Measurements ◽  
Olive Tree ◽  
Structural System ◽  
Impulsive Forces ◽  
Spatio Temporal ◽  
Pod Analysis ◽  
Complete Detachment ◽  
Tree Branch ◽  
The Impact

Geometry consistent spatio-temporal measurements of the experimental acceleration of olive tree branches were analyzed with advanced POD tools in an effort to gain knowledge on the mechanics-dynamics of this bio-mechanical structure. To pave the way for understanding the dynamics of this system, both the typical olive tree as a whole and its typical branch are approached as interacting soft-stiff continuum mechanical systems. The POD analysis reveals that the impact response is a nonlinear vibration with very fast dissipation. The POD modal amplitudes are nonlinear vibrations of continuous, broadband frequency spectrum. Initially they exhibit regular phases of nonlinear slow dissipation-and-amplification followed by irregular, fast dissipation-and-amplification phases. Sequentially applied impacts at the branch soft area results in a complete detachment of the fruit. The POD analysis reveals that this occurs because the response is highly localized in the soft area where the impact is applied and thus it transfers its momentum to the fruits. The work is supplemented with analysis of field measurements of the acceleration dynamics of orchard olive tree branches excited by harvesting devices generating combing clouds of impulsive forces aimed at detaching the olive fruit by momentum transfer.

Comparison of field measurements to predicted reaeration coefficients, k2, in the application of a water quality model, QUAL2E, to a tropical river

2002 ◽  
Vol 46 (9) ◽  
pp. 47-54 ◽  
Author(s):  
M. Mohamed ◽  
J.D. Stednick ◽  
F.M. Smith
Keyword(s):  
Water Quality ◽  
Standard Error ◽  
Field Measurements ◽  
Water Quality Modeling ◽  
Low Flow ◽  
Quality Model ◽  
Predictive Equations ◽  
Discharge Data ◽  
Study Results ◽  
Reaeration Coefficient

Some of the many tools used for watershed management are mathematical and computer models for wasteload allocations. QUAL2E is one of the most popular water quality models used for such purposes. The question arises as to whether the model is applicable in a different climate such as that in the tropics. In this study, QUAL2E was used to model Sg. Selangor River in Malaysia using the predictive equations for reaeration coefficient (k2) within the model and the measured reaeration coefficients for the river. The study results indicated that use of the reaeration coefficient (k2) measured at Sg. Selangor River did give the lowest standard error (SE) for the simulation of water quality during the 7Q10 low-flow period which is considered as the worst scene scenario in water quality modeling. But during calibration and validation using actual low-flow discharge data, the measured reaeration coefficients did not give the lowest standard error (SE). In conclusion, the results indicated that QUAL2E is applicable in tropical rivers when used with the modeled river parameters (i.e. hydraulic parameters, meteorological conditions etc.). Measured reaeration coefficients produced good results and several predictive equations also produced comparatively good results.

CFD modelling and validation of measured wind field data in a portable wind tunnel

2011 ◽  
Vol 3 (3) ◽  
pp. 315-325 ◽  
Author(s):  
Andres Gartmann ◽  
Wolfgang Fister ◽  
Wolfgang Schwanghart ◽  
Mathias D. Müller
Keyword(s):  
Wind Tunnel ◽  
Wind Field ◽  
Field Data ◽  
Cfd Modelling

scholarly journals Evaluating multi-year, multi-site data on the energy balance closure of eddy-covariance flux measurements at cropland sites in southwestern Germany

2019 ◽  
Vol 16 (2) ◽  
pp. 521-540 ◽  
Author(s):  
Ravshan Eshonkulov ◽  
Arne Poyda ◽  
Joachim Ingwersen ◽  
Hans-Dieter Wizemann ◽  
Tobias K. D. Weber ◽  
...  
Keyword(s):  
Energy Balance ◽  
Eddy Covariance ◽  
Wind Direction ◽  
Climate Models ◽  
Global Climate Models ◽  
Energy Balance Closure ◽  
Prevailing Wind ◽  
Atmospheric Conditions ◽  
Prevailing Wind Direction ◽  
Wide Range

Abstract. The energy balance of eddy-covariance (EC) measurements is typically not closed, resulting in one of the main challenges in evaluating and interpreting EC flux data. Energy balance closure (EBC) is crucial for validating and improving regional and global climate models. To investigate the nature of the gap in EBC for agroecosystems, we analyzed EC measurements from two climatically contrasting regions (Kraichgau – KR – and Swabian Jura – SJ) in southwestern Germany. Data were taken at six fully equipped EC sites from 2010 to 2017. The gap in EBC was quantified by ordinary linear regression, relating the energy balance ratio (EBR), calculated as the quotient of turbulent fluxes and available energy, to the residual energy term. In order to examine potential reasons for differences in EBC, we compared the EBC under varying environmental conditions and investigated a wide range of possible controls. Overall, the variation in EBC was found to be higher during winter than summer. Moreover, we determined that the site had a statistically significant effect on EBC but no significant effect on either crop or region (KR vs SJ). The time-variable footprints of all EC stations were estimated based on data measured in 2015, complimented by micro-topographic analyses along the prevailing wind direction. The smallest mean annual energy balance gap was 17 % in KR and 13 % in SJ. Highest EBRs were mostly found for winds from the prevailing wind direction. The spread of EBRs distinctly narrowed under unstable atmospheric conditions, strong buoyancy, and high friction velocities. Smaller footprint areas led to better EBC due to increasing homogeneity. Flow distortions caused by the back head of the anemometer negatively affected EBC during corresponding wind conditions.

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