scholarly journals Linking urban aerosol fluxes in street canyons to larger scale emissions

2010 ◽  
Vol 10 (5) ◽  
pp. 2475-2490 ◽  
Author(s):  
B. K. Tay ◽  
G. B. McFiggans ◽  
D. P. Jones ◽  
M. W. Gallagher ◽  
C. Martin ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Field Experiments ◽  
Ultrafine Particle ◽  
Urban Aerosol ◽  
Cfd Model ◽  
Street Canyons ◽  
First Order ◽  
Flux Measurements ◽  
Circulatory Flow ◽  
Computational Fluid Dynamics Cfd

Abstract. In this study we investigate ultrafine particle (UFP) fluxes using a first order eddy viscosity turbulence closure Computational Fluid Dynamics (CFD) model and determine the different factors that influence emissions of UFP into the urban boundary layer. Both vertical turbulent fluxes as well as the fluxes due to mean circulatory flow are shown to contribute to the overall ventilation characteristics of street canyons. We then derive a simple parameterised numerical prediction model for canyon top UFP venting which is then compared with tower based micrometeorological flux measurements obtained during the REPARTEE & CityFlux field experiments.

scholarly journals Linking aerosol fluxes in street canyons to urban city-scale emissions

2009 ◽  
Vol 9 (5) ◽  
pp. 18065-18112
Author(s):  
B. K. Tay ◽  
G. B. McFiggans ◽  
D. P. Jones ◽  
M. W. Gallagher ◽  
C. Martin ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Field Experiments ◽  
Ultrafine Particle ◽  
Cfd Model ◽  
Mean Flow ◽  
Street Canyons ◽  
First Order ◽  
Urban City ◽  
Flux Measurements ◽  
Computational Fluid Dynamics Cfd

Abstract. In this study we investigate ultrafine particle (UFP) fluxes using a first order eddy viscosity turbulence closure Computational Fluid Dynamics (CFD) model and determine the different factors that influence emissions of UFP into the urban boundary layer. Both vertical turbulent fluxes as well as the fluxes due to mean flow are shown to contribute to the overall ventilation characteristics of street canyons. We then derive a simple parameterised numerical prediction model for canyon top UFP venting which is then compared with tower based micrometeorological flux measurements obtained during the REPARTEE and CityFlux field experiments.

scholarly journals Quantifying the Airflow Distortion over Merchant Ships. Part I: Validation of a CFD Model

2006 ◽  
Vol 23 (3) ◽  
pp. 341-350 ◽  
Author(s):  
Bengamin I. Moat ◽  
Margaret J. Yelland ◽  
Robin W. Pascal ◽  
Anthony F. Molland
Keyword(s):  
Wind Speed ◽  
Charles Darwin ◽  
Reverse Direction ◽  
Cfd Model ◽  
Mean Flow ◽  
Flow Distortion ◽  
Flux Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean

Abstract The effects of flow distortion created by the ship’s hull and superstructure bias wind speed measurements made from anemometers located on ships. Flow distortion must be taken into account if accurate air–sea flux measurements are to be achieved. Little work has been undertaken to examine the wind speed bias due to flow distortion in wind speed reports from voluntary observing ships (VOS). In this first part of a two-part paper the accuracy of the computational fluid dynamics (CFD) code VECTIS in simulating the airflow over VOS is investigated. Simulations of the airflow over a representation of the bridge of a VOS are compared to in situ wind speed measurements made from six anemometers located above the bridge of the RRS Charles Darwin. The ship’s structure was ideal for reproducing the flow over VOS when the wind is blowing onto either beam. The comparisons showed VECTIS was accurate to within 4% in predicting the wind speed over ships, except in extreme cases such as wake regions or the region close to the bridge top where the flow may be stagnant or reverse direction. The study showed that there was little change in the numerically predicted flow pattern above the bridge with change in Reynolds number between 2 × 105 and 1 × 107. The findings showed that the CFD code VECTIS can reliably be used to determine the mean flow above typical VOS.

scholarly journals Hydrodynamic impact and power production of tidal turbines in a storm surge barrier

2020 ◽  
Vol 3 (3) ◽  
pp. 127-136
Author(s):  
Thomas O'Mahoney ◽  
Anton De Fockert ◽  
Arnout C. Bijlsma ◽  
Pieter De Haas
Keyword(s):  
Storm Surge ◽  
Energy Production ◽  
Field Experiments ◽  
Turbine Blades ◽  
Cfd Model ◽  
Hydrodynamic Impact ◽  
Tidal Turbines ◽  
Gate Opening ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

To estimate the impact on energy production and environment of tidal turbines placed in the Eastern Scheldt Storm Surge Barrier a Computational Fluid Dynamics (CFD) study has been carried out on the additional head differences induced by the turbines. The CFD model focusses on a single gate opening of the Storm Surge Barrier and includes half of the adjoining gates on either side. In this 40 m wide Gate a 1.2 MW array existing of five Tocardo T2 tidal turbines has been installed as part of a demonstration project in 2015. Transient computations of the barrier with and without the turbine array were carried out for a range of quasi stationary tidal phases. The turbines are resolved in detail as rotating equipment: real-time rotation of the turbine blades (involving the displacement of the mesh nodes in an unsteady setting) is implemented, and torque and thrust for the prescribed speed of rotation is provided as output. The results for velocity, power and thrust are compared with field experiments to validate the model. Based on these computations an estimate of the effect of turbines on the discharge capacity of the storm surge barrier is given. This information will be used to parameterize the tidal turbines in the far-field hydrodynamic model of Eastern Scheldt estuary for the ultimate assessment of the effect of tidal turbines on energy production and on the environment.

CFD Simulations of Flows in Step-up Street Canyons

2020 ◽  
Author(s):  
Soo-Jin Park ◽  
Jae-Jin Kim ◽  
Eric Pardyjak ◽  
Ji-Yoon Hong
Keyword(s):  
Wind Tunnel ◽  
Flow Characteristics ◽  
Width Ratio ◽  
Cfd Model ◽  
Wind Tunnel Experiments ◽  
Cfd Simulations ◽  
Street Canyons ◽  
Recirculation Zones ◽  
Computational Fluid Dynamics Cfd ◽  
Two Stages

<p>We analyzed the flow characteristics in strep-up street canyons using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations (H<sub>u</sub>/H<sub>d</sub> = 0.33, 0.6 and L/S = 1, 2, 3, and 4; H<sub>u</sub>, H<sub>d</sub>, L, and S respectively indicate the upwind, downwind building heights, the building length and street-canyon width) as those in the wind-tunnel experiments. The CFD model reproduced the in-canyon vortex, recirculation zones above the downwind buildings, and stagnation point position reasonably well. Furthermore, we analyze the flow characteristics in the step-up street canyons based on the numerical results. The in-canyon flows simulated in the shallow (H<sub>u</sub>/H<sub>d</sub> = 0.33) and deep (H<sub>u</sub>/H<sub>d</sub> = 0.6) street canyons underwent two stages (development and mature stages) as the building-length ratio increased. In the development stages, one clockwise-rotating vortex was formed in the step-up street canyons and its center was slightly tilted toward the wall of the upwind building. However, in the mature stages, two clockwise-rotating vortices were formed in the upper and lower layers. A clockwise vortex and a counterclockwise vortex were stabilized as the building width ratio increased.</p>

Effects of Over Fire Air on the Combustion and NOx Emission Characteristics of a 600 MW Opposed Swirling Fired Boiler

2012 ◽  
Vol 512-515 ◽  
pp. 2135-2142 ◽  
Author(s):  
Yu Peng Wu ◽  
Zhi Yong Wen ◽  
Yue Liang Shen ◽  
Qing Yan Fang ◽  
Cheng Zhang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Empirical Method ◽  
Nox Emission ◽  
Emission Characteristics ◽  
Cfd Model ◽  
Nitrogen Release ◽  
Computational Fluid Dynamics Cfd ◽  
Low Nox Emission

A computational fluid dynamics (CFD) model of a 600 MW opposed swirling coal-fired utility boiler has been established. The chemical percolation devolatilization (CPD) model, instead of an empirical method, has been adapted to predict the nitrogen release during the devolatilization. The current CFD model has been validated by comparing the simulated results with the experimental data obtained from the boiler for case study. The validated CFD model is then applied to study the effects of ratio of over fire air (OFA) on the combustion and nitrogen oxides (NOx) emission characteristics. It is found that, with increasing the ratio of OFA, the carbon content in fly ash increases linearly, and the NOx emission reduces largely. The OFA ratio of 30% is optimal for both high burnout of pulverized coal and low NOx emission. The present study provides helpful information for understanding and optimizing the combustion of the studied boiler

Validation of a Computationally Efficient Computational Fluid Dynamics (CFD) Model for Industrial Bubble Column Bioreactors

2014 ◽  
Vol 53 (37) ◽  
pp. 14526-14543 ◽  
Author(s):  
Dale D. McClure ◽  
Hannah Norris ◽  
John M. Kavanagh ◽  
David F. Fletcher ◽  
Geoffrey W. Barton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Bubble Column ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Computational Fluid Dynamics Cfd

Artificially Ventilated Cavities: Evaluating the Constant-Pressure Approximation

2017 ◽  
Author(s):  
Melissa A. Fronzeo ◽  
Michael Kinzel ◽  
Jules Lindau
Keyword(s):  
Constant Pressure ◽  
Flow Behavior ◽  
Internal Cavity ◽  
Common Assumption ◽  
Ventilated Cavity ◽  
Physical Insight ◽  
Circulatory Flow ◽  
Computational Fluid Dynamics Cfd ◽  
The Common ◽  
Semi Empirical

Computational Fluid Dynamics (CFD) is employed to study the fundamental aspects of the internal pressure within artificially ventilated, gaseous cavities in both twin- and toroidal-vortex closure modes. The results show that several pressure regions develop within the cavities, indicating that the common assumption that the cavity has a constant pressure breaks down when evaluated in high detail. The internal cavity pressure is evaluated using a probability density function (PDF). The resulting PDF plots show a clusters with multiple peaks. A mixture-of-Gaussians (MOG) method is employed to better understand the distributions of these peaks. These peaks are then mapped to the simulation results, where it is observed that these peaks correlate to distinct cavity regions (which vary depending on cavity type). Moreover, these varying pressure regions appear to align with cavity-radius growth and reduction and appear to be the driving force of the internal, circulatory flow. Lastly, the importance of these pressure regions are investigated with respect to predictions from semi-empirical theory of the cavity shape, showing a moderate impact depending on where the cavity is probed. Overall, these results provide physical insight into ventilated cavity flow behavior that is often ignored.

An Integrated Ship Re-Design/Modification Strategy

2019 ◽  
Vol 161 (A1) ◽  
Keyword(s):  
Computer Aided Design ◽  
Modular Design ◽  
Ship Hull ◽  
Cfd Model ◽  
Hull Form ◽  
Design Modification ◽  
Technical Parameters ◽  
Computational Fluid Dynamics Cfd ◽  
Bulbous Bow ◽  
Aided Design

Herein, we present an integrated ship re-design/modification strategy that integrates the ‘Computer-Aided Design (CAD)’ and ‘Computational Fluid Dynamics (CFD)’ to modify the ship hull form for better performance in resistance. We assume a modular design and the ship hull form modification focuses on the forward module (e.g. bulbous bow) and aft module (e.g. stern bulb) only. The ship hull form CAD model is implemented with NAPA*TM and CFD model is implemented with Shipflow**TM. The basic ship hull form parameters are not changed and the modifications in some of the technical parameters because of re-designed bulbous bow and stern bulb are kept at very minimum. The bulbous bow is re-designed by extending an earlier method (Sharma and Sha (2005b)) and stern bulb parameters for re-design are computed from the experience gained from literature survey. The re-designed hull form is modeled in CAD and is integrated and analyzed with Shipflow**TM. The CAD and CFD integrated model is validated and verified with the ITTC approved recommendations and guidelines. The proposed numerical methodology is implemented on the ship hull form modification of a benchmark ship, i.e. KRISO container ship (KCS). The presented results show that the modified ship hull form of KCS - with only bow and stern modifications - using the present strategy, results into resistance and propulsive improvement.

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