scholarly journals A study on the diffusion of matter from a continuous point source in the uniform mean shear flows (1st report, Characteristics of the mean concentration field)

1985 ◽  
Vol 51 (468) ◽  
pp. 2554-2562
Author(s):  
Ikuo NAKAMURA ◽  
Yasuhiko SAKAI ◽  
Masafumi MIYATA ◽  
Hiroyuki TSUNODA
Keyword(s):  
Point Source ◽  
Shear Flows ◽  
Concentration Field ◽  
Continuous Point ◽  
The Mean ◽  
Mean Concentration

scholarly journals Diffusion of Matter from a Continuous Point Source in Uniform Mean Shear Flows : 1st Report, Characteristics of the Mean Concentration Field

1986 ◽  
Vol 29 (250) ◽  
pp. 1141-1148 ◽  
Author(s):  
lkuo NAKAMURA ◽  
Yasuhiko SAKAI ◽  
Masafumi MIYATA ◽  
Hiroyuki TSUNODA
Keyword(s):  
Point Source ◽  
Shear Flows ◽  
Concentration Field ◽  
Continuous Point ◽  
The Mean ◽  
Mean Concentration

Diffusion of matter by a non-buoyant plume in grid-generated turbulence

1987 ◽  
Vol 178 ◽  
pp. 379-403 ◽  
Author(s):  
Ikuo Nakamura ◽  
Yasuhiko Sakai ◽  
Masafumi Miyata
Keyword(s):  
Relative Intensity ◽  
Concentration Field ◽  
Reynolds Numbers ◽  
Experimental Results ◽  
Buoyant Plume ◽  
Gaussian Shape ◽  
Radial Profiles ◽  
Continuous Point ◽  
The Mean ◽  
Mean Concentration

The turbulent diffusion process is investigated for a continuous point source of a non-buoyant plume in grid-generated water turbulence. Two kinds of biplanar grids with a mesh length of 10 mm and 20 mm were used. The mesh Reynolds numbers were 1480 and 2970, respectively. The mean and fluctuating concentration fields of aqueous dye solution were measured by the light absorption method. Experimental results for both grids were compared.For both grids, the mean concentration radial profiles proved to have a similar Gaussian shape, and the mean concentration on the plume axis obeys the hyperbolic decay law well. These mean concentration profiles and their decay show an excellent agreement with the results deduced from the similarity analysis for the mean concentration field.Radial profiles of the fluctuation r.m.s. value and relative intensity (i.e. the ratio of the r.m.s. value to the mean concentration) were found also to be nearly similar, and the centreline r.m.s. value decays downstream as a hyperbola. The relative intensity on the centreline tends to increase slightly downstream. All experimental results obtained were much less scattered and more reliable than those reported earlier.The similarity for the concentration fluctuation intensity has been analysed using a thin-layer approximation. Also, an approximate analysis of the fluctuating concentration field is given by replacing the fluctuating concentration signal by a randomly spaced sequence of rectangular waves with various heights and widths.

Experimental Investigation of the Mean Concentration Fields in a Counterflowing Jet

2010 ◽  
Author(s):  
Luis A. Torres ◽  
Brian A. Fleck ◽  
David J. Wilson ◽  
David Nobes ◽  
Mohammad Mahmoudi
Keyword(s):  
Concentration Field ◽  
Flow Zone ◽  
Length Scales ◽  
Empirical Expressions ◽  
Free Jet ◽  
Similar Region ◽  
Planar Laser ◽  
The Mean ◽  
Counterflowing Jet ◽  
Mean Concentration

The geometrically similar region of the centerline concentration decay of a counter-flowing jet was investigated using planar laser induced fluorescence. The jet is investigated for jet to counterflowing velocity ratios (Ur) in the range 4<Ur<19. New length scales for this flow were studied and used to generate empirical expressions to predict the concentration decay in the established flow zone. These length scales were defined using the 5% contour of the mean concentration field of the counterflowing jet. Additional experiments for two jet to counterflow velocity ratios were used to validate these empirical expressions. The new empirical expressions correlate well with the concentration decay in the centerline of the counterflowing jet within the free jet-like region. It was found that for some cases, the centerline concentration decay of the counterflowing jet was better predicted considering decay proportional to x−6/5, even though it can also be predicted by assuming decay with x−1.

Three-Dimensional Simulation for Diffusion of Matter in Compound Round Jet by Particle Method

2003 ◽  
Author(s):  
Tomomi Uchiyama ◽  
Akihito Ichikawa
Keyword(s):  
Three Dimensional ◽  
Concentration Field ◽  
Particle Method ◽  
Vortex Method ◽  
Vortical Flow ◽  
Round Jet ◽  
The Mean ◽  
Dimensional Simulation ◽  
Mean Concentration ◽  
Good Agreement

The diffusion of matter in compound round jet is simulated by three-dimensional particle method. The flow field is calculated with a vortex method, whereas the concentration field is simulated through a particle method analogous to the vortex method. It is shown that the concentration distribution yielded by the three-dimensional vortical flow is in good agreement with the experimental one obtained by the flow visualization. The mean concentration is confirmed to be in the self-preservation state.

The nozzle-fluid concentration field of the round, turbulent, free jet

1967 ◽  
Vol 30 (2) ◽  
pp. 285-303 ◽  
Author(s):  
H. A. Becker ◽  
H. C. Hottel ◽  
G. C. Williams
Keyword(s):  
Spectral Distribution ◽  
Concentration Field ◽  
Temperature Fields ◽  
Light Scatter ◽  
Free Jet ◽  
Fluid Concentration ◽  
Point Correlation ◽  
The Mean ◽  
Intermittency Factor ◽  
Mean Concentration

The light-scatter technique has been used to study the nozzle-fluid concentration field in an isothermal, turbulent, axisymmetric air/air free jet with the nozzle air marked by an oil smoke. The data on the mean concentration field appear to be the most accurate yet obtained, due to the peculiar advantages of the technique. The turbulent concentration fluctuations have been characterized as to intensity, spectral distribution, and two-point correlation. The intermittency factor has been measured and the properties of the turbulent fluid computed. Comparison with the results of other investigators who used heat to mark the nozzle fluid indicates a close similarity between the concentration and temperature fields.

Averaging for Wind Speed in a Given Direction in the Concentration Equation for Pollutants

1977 ◽  
Vol 16 (10) ◽  
pp. 1097-1100 ◽  
Author(s):  
J. Neumann
Keyword(s):  
Standard Deviation ◽  
Wind Speed ◽  
Point Source ◽  
Gamma Distribution ◽  
Wind Direction ◽  
Average Concentration ◽  
Continuous Point ◽  
The Mean ◽  
The One ◽  
Concentration Equation

Abstract In the equation for the concentration of pollutants from a steady continuous point source, in a stationaryturbulent flow, the factor 1/u enters (u is the mean wind for a given stationary situation). If we are interestedin the concentration along a given wind direction and u denotes the wind speed in that direction and if weseek the average concentration for a class of flow situations (e.g., for the class of statically stable flows),each member of the class representing an individual stationary situation, then the averaging to be appliedis to 1/u and not to u. On the assumption (verified by some examples) that the distribution of u isa "humped" gamma distribution (standard deviation σ less than the average u of u for the class as a whole),we show that the average of 1/u equals 1/(u[1-(σ/u)2]}. Thus the average of 1/u is greater than 1/uand the resulting concentration estimate is larger than the one that would be obtained by the incorrect useof 1/u.

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