scholarly journals Flow and Turbulence in an Urban Canyon

2011 ◽  
Vol 50 (1) ◽  
pp. 203-223 ◽  
Author(s):  
D. Zajic ◽  
H. J. S. Fernando ◽  
R. Calhoun ◽  
M. Princevac ◽  
M. J. Brown ◽  
...  
Keyword(s):  
Built Environment ◽  
Wind Direction ◽  
Street Canyon ◽  
Thermal Characteristics ◽  
Flow Patterns ◽  
Oklahoma City ◽  
Urban Canyon ◽  
Stability Conditions ◽  
Mean Flow ◽  
Stable Conditions

Abstract A better understanding of the interaction between the built environment and the atmosphere is required to more effectively manage urban airsheds. This paper reports an analysis of data from an atmospheric measurement campaign in Oklahoma City, Oklahoma, during the summer of 2003 that shows wind flow patterns, turbulence, and thermal effects in the downtown area. Experimental measurements within a street canyon yielded airflow patterns, stability conditions, and turbulence properties as a function of the incoming wind direction and time of the day. Air and surface temperatures at two different sites, one within the downtown urban canyon and the other in a nearby park, were measured. A study of the stability conditions within the urban canyon during the campaign indicates that dynamically stable conditions did not occur within the canyon. This provides evidence that the built environment can strongly influence the thermal characteristics in cities. Mean flow patterns close to the street level are analyzed for two different ranges of incoming wind directions and are compared with those obtained from a previous field experiment featuring idealized building configurations. This paper presents an approach allowing the estimation of wind direction in an urban canyon, given inflow conditions, that shows good agreement with wind patterns in the Oklahoma City street canyon. Turbulence statistics were calculated and normalized using different velocity scales to investigate the efficacy of the latter in specifying turbulence levels in urban canopies. The dependence of turbulence quantities on incoming wind direction and time of the day was investigated.

scholarly journals Properties of the Wind Field within the Oklahoma City Park Avenue Street Canyon. Part I: Mean Flow and Turbulence Statistics

2007 ◽  
Vol 46 (12) ◽  
pp. 2038-2054 ◽  
Author(s):  
M. A. Nelson ◽  
E. R. Pardyjak ◽  
J. C. Klewicki ◽  
S. U. Pol ◽  
M. J. Brown
Keyword(s):  
Wind Direction ◽  
Street Canyon ◽  
Sonic Anemometer ◽  
Surface Wind ◽  
Oklahoma City ◽  
Prevailing Wind ◽  
Advective Transport ◽  
Mean Flow ◽  
Prevailing Wind Direction ◽  
The Mean

Abstract Velocity data were obtained from sonic anemometer measurements within an east–west-running street canyon located in the urban core of Oklahoma City, Oklahoma, during the Joint Urban 2003 field campaign. These data were used to explore the directional dependence of the mean flow and turbulence within a real-world street canyon. The along-canyon vortex that is a key characteristic of idealized street canyon studies was not evident in the mean wind data, although the sensor placement was not optimized for the detection of such structures. Instead, surface wind measurements imply that regions of horizontal convergence and divergence exist within the canopy, which are likely caused by taller buildings diverting the winds aloft down into the canopy. The details of these processes appear to be dependent on relatively small perturbations in the prevailing wind direction. Turbulence intensities within the canyon interior appeared to have more dependence on prevailing wind direction than they did in the intersections. Turbulence in the intersections tended to be higher than was observed in the canyon interior. This behavior implies that there are some fundamental differences between the flow structure found in North American–style cities where building heights are typically heterogeneous and that found in European-style cities, which generally have more homogeneous building heights. It is hypothesized that the greater three-dimensionality caused by the heterogeneous building heights increases the ventilation of the urban canopy through mean advective transport as well as enhanced turbulence.

scholarly journals Dispersion Coefficients For Puff at Different Stability Conditions

2021 ◽  
pp. 1-8
Keyword(s):  
Wind Direction ◽  
Dispersion Curves ◽  
Stability Conditions ◽  
Dispersion Coefficients ◽  
Stable Conditions

Slade gave 3 sets of dispersion coefficients for puff i.e, for Unstable, Neutral & Very Stable conditions for 100m and 4000m spread along wind direction. These dispersion coefficients were adopted for stabilities B,D&F respectively. The dispersion coefficients for the remaining 3 stabilities i.e, A,C&E were arrived at by comparing the puff dispersion with the corresponding plumes Pasquil-Gifford had given curves for the different plume spread during A to F stabilities in the same way dispersion curves for puff are plotted for stabilities A to F.

scholarly journals Flow patterns of shallow Palic Lake induced by the dominant winds

2012 ◽  
Vol 10 (1) ◽  
pp. 55-67
Author(s):  
Ljubomir Budinski ◽  
Djula Fabian
Keyword(s):  
Numerical Model ◽  
Flow Pattern ◽  
Coriolis Force ◽  
Wind Direction ◽  
Driving Forces ◽  
Open Water ◽  
Flow Patterns ◽  
Two Dimensional ◽  
Lake Model ◽  
Double Gyre

Studies of lake currents have highlighted that in case of stagnant waters winds are the dominant driving forces. This study is dealing with the influence of dominant winds on the flow pattern of Palic Lake. Action of steady winds of different directions has been tested on the lake by means of a two dimensional numerical model, while in addition to winds all other permanent factors like actual bathymetry, inflow and outflow as well the Coriolis force have been accounted for. The experiments have revealed that winds of different directions created corresponding characteristic flow patterns (in base plot), which were similar in cases of winds having opposite directions. However, in such cases the direction of flow was opposite. Moreover, the Palic Lake model produced the well known double-gyre flow pattern: in the coastal strip the direction of the current corresponded to the wind direction, while it was opposite in the domain of open water.

scholarly journals Numerical Simulation of Coherent Structures in the Turbulent Boundary Layer under Different Stability Conditions

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1068
Author(s):  
Shujin Laima ◽  
Hehe Ren ◽  
Hui Li ◽  
Jinping Ou
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Correlation Coefficient ◽  
Wind Velocity ◽  
Coherent Structures ◽  
Stability Conditions ◽  
Velocity Spectrum ◽  
Turbulent Eddy ◽  
Stable Conditions ◽  
The Stability

Coherent structures in the turbulent boundary layer were investigated under different stability conditions. Qualitative analyses of the flow field, spatial correlation coefficient field and pre-multiplied wind velocity spectrum showed that the dominant turbulent eddy structure changed from small-scale motions to large- and very-large-scale motions and then to thermal plumes as the stability changed from strong stable to neutral and then to strong unstable. A quantitative analysis of the size characteristics of the three-dimensional turbulent eddy structure based on the spatial correlation coefficient field showed that under near-neutral stability, the streamwise, wall-normal and spanwise extents remained constant at approximately 0.3 δ , 0.1 δ and 0.2 δ ( δ , boundary layer height), respectively, while for other conditions, the extent in each direction varied in a log-linear manner with stability; only the spanwise extent under stable conditions was also independent of stability. The peak wavenumber of the pre-multiplied wind velocity spectrum moves towards small values from stable conditions to neutral condition and then to unstable conditions; thus, for the wind velocity spectrum, another form is needed that takes account the effects of the stability condition.

Characteristics of the mean flow patterns and structure of turbulence in spiral gas streams

AIChE Journal ◽  
1960 ◽  
Vol 6 (4) ◽  
pp. 648-655 ◽  
Author(s):  
W. R. Schowalter ◽  
H. F. Johnstone
Keyword(s):  
Flow Patterns ◽  
Mean Flow ◽  
Gas Streams ◽  
The Mean

scholarly journals Water Jacket Systems for Temperature Control of Petri Dish Cell Culture Chambers

2019 ◽  
Vol 9 (4) ◽  
pp. 621 ◽  
Author(s):  
Samira Uharek ◽  
Sara Baratchi ◽  
Jiu Zhu ◽  
Majed Alshehri ◽  
Arnan Mitchell ◽  
...  
Keyword(s):  
Cell Culture ◽  
Temperature Gradient ◽  
Transition Period ◽  
Thermal Characteristics ◽  
Petri Dish ◽  
Sample Volume ◽  
Radial Temperature ◽  
Transient Conditions ◽  
Water Jacket ◽  
Stable Conditions

Water jacket systems are routinely used to control the temperature of Petri dish cell culture chambers. Despite their widespread use, the thermal characteristics of such systems have not been fully investigated. In this study, we conducted a comprehensive set of theoretical, numerical and experimental analyses to investigate the thermal characteristics of Petri dish chambers under stable and transient conditions. In particular, we investigated the temperature gradient along the radial axis of the Petri dish under stable conditions, and the transition period under transient conditions. Our studies indicate a radial temperature gradient of 3.3 °C along with a transition period of 27.5 min when increasing the sample temperature from 37 to 45 °C for a standard 35 mm diameter Petri dish. We characterized the temperature gradient and transition period under various operational, geometric, and environmental conditions. Under stable conditions, reducing the diameter of the Petri dish and incorporating a heater underneath the Petri dish can effectively reduce the temperature gradient across the sample. In comparison, under transient conditions, reducing the diameter of the Petri dish, reducing sample volume, and using glass Petri dish chambers can reduce the transition period.

Bistable Flow Patterns in a Free Surface Water Channel

1989 ◽  
Vol 111 (4) ◽  
pp. 408-413
Author(s):  
E. W. Adams ◽  
A. I. Stamou
Keyword(s):  
Free Surface ◽  
Surface Water ◽  
Stable State ◽  
Flow Patterns ◽  
Shear Layers ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Free Shear Layers ◽  
Side Flow ◽  
Bistable Flow

A series of experiments is reported on a free surface water tunnel with a slot inlet centered at mid-depth in which the flow exhibited equally probable bistable flow patterns. The two flow fields are strongly asymmetric even when the geometry is symmetric and consists of a long stall on one side of the inlet and a short stall on the opposite side. Flow visualization and laser-Doppler velocimetry were performed to examine the flow structure of both stable states in detail. Results showed that the mean flow and turbulence structure of the two bistable states are largely mirror images of each other within the separation zone. The effect of the wall on the flow is minor, only very close to the wall/free surface did the difference in wall constraints cause the two flow patterns to diverge. After reattachment both flows relax to free-surface channel flow. It is shown that the bistable flow pattern results from the interaction of the free shear layers and that only strong disturbances in the free shear layers can cause the flow in one stable state to switch to the other stable state. Bistable flow exists for geometries with asymmetry up to 10 percent for the expansion ratio studied.

Variability of Wind Direction in Relation to Wind Speed*

1956 ◽  
Vol 37 (9) ◽  
pp. 462-464 ◽  
Author(s):  
W. J. Saucier ◽  
K. C. Brundidge
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Flow Patterns ◽  
Atmospheric Flow

A simple principle of mechanics, as applied to wind variation, is used to clarify several important features of atmospheric flow patterns.

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