Mean Concentration Field of a Jet in a Uniform Counter-Flow

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Luis A. Torres ◽  
Mohammad Mahmoudi ◽  
Brian A. Fleck ◽  
David J. Wilson ◽  
David Nobes
Keyword(s):  
Linear Growth ◽  
Concentration Field ◽  
Flow Region ◽  
Counter Flow ◽  
Scaling Factors ◽  
Scalar Concentration ◽  
Planar Laser ◽  
Radial Spreading ◽  
The Mean ◽  
Mean Concentration

An experimental investigation of the scaling factors of mean scalar concentration field of jets issuing into a uniform counter-flow stream is presented. The centerline decay and radial spreading of the mean concentration field were measured by using planar laser induced fluorescence. Jet to counter-flow velocity ratios ranging between 4 to19 were investigated for two different jet diameters. The 5% contour of the mean concentration field of the jet was used to define new scaling factors that generate universal forms for the centerline concentration decay. The jet growth rate in the radial direction was found to be divided into two regions where a linear growth was observed and a region characterized by a power law. Empirical expressions are introduced which predict concentration decay in the established flow region in both the axial and radial directions.

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.

Concentration Field Measurements Within Isolated Turbulent Puffs

2006 ◽  
Vol 129 (2) ◽  
pp. 194-199 ◽  
Author(s):  
E. Ghaem-Maghami ◽  
H. Johari
Keyword(s):  
Concentration Field ◽  
Spherical Geometry ◽  
Field Measurements ◽  
Axial Direction ◽  
Passive Scalar ◽  
Fast Response ◽  
Mie Scattering ◽  
Injection Volume ◽  
Scalar Concentration ◽  
Planar Laser

The structure of passive scalar concentration field within isolated turbulent puffs was measured using the planar laser Mie scattering technique. Puffs were generated by injecting seeded air through a 5-mm-diameter nozzle into a chamber with a weak air co-flow. The injection time and volume was varied by the use of a fast-response solenoid valve. Puffs were examined in the range of 25–55 diameters downstream of the nozzle. The Reynolds number based on the average velocity and nozzle diameter was 5000. The results indicate that as the injection volume increases, puffs evolve from a spherical geometry to that with a tail. The half-width of radial concentration profiles through the puff center decrease as the injection volume increases. On the other hand, the puff length in the axial direction increases with the injection volume. The volume of ambient fluid entrained by the puff, and normalized by the injected volume, decreases with increasing injection volume.

Passive scalar dispersion in a turbulent boundary layer from a line source at the wall and downstream of an obstacle

2000 ◽  
Vol 424 ◽  
pp. 127-167 ◽  
Author(s):  
J.-Y. VINÇONT ◽  
S. SIMOËNS ◽  
M. AYRAULT ◽  
J. M. WALLACE
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Similarity Solution ◽  
Line Source ◽  
Concentration Field ◽  
Mean Square ◽  
Two Dimensional ◽  
Scalar Concentration ◽  
The Mean ◽  
Made In

Simultaneous measurements of the velocity and scalar concentration fields have been made in the plume emitting from a two-dimensional line source at the wall. The source is one obstacle height, h, downstream of a two-dimensional square obstacle located on the wall of a turbulent boundary layer. These measurements were made in two fluid media: water and air. In both media particle image velocimetry (PIV) was used for the velocity field measurements. For the scalar concentration measurements laser-induced uorescence (LIF) was used for the water flow and Mie scattering diffusion (MSD) for the air flow. Profiles of the mean and root-mean-square streamwise and wall-normal velocity components, Reynolds shear stress and mean and root-mean-square scalar concentration were determined at x = 4h and 6h downstream of the obstacle in the recirculation region and above it in the mixing region. At these streamwise stations the scalar fluxes, uc and vc, were also determined from the simultaneous velocity and scalar concentration field data. Both of these fluxes change sign from negative to positive with increasing distance from the wall in the recirculating region at 4h.A conditional analysis of the data was carried out by sorting them into the eight categories (octants) given by the sign combinations of the three variables: ±u, ±v and ±c. The octants with combinations of these three variables that correspond to types of scalar concentration flux motions that can be approximated by mean gradient scalar transport models are the octants that make the dominant contributions to uc and vc. However, in the recirculating zone, counter-gradient transport type motions also make significant contributions. Based on this conditional analysis, second-order mean gradient models of the scalar and the momentum uxes were constructed; they compare well to the measured values at 4h and 6h, particularly for the streamwise scalar flux, uc.Additional measurements of the velocity and concentration fields were made further downstream of the reattachment location in the wake region of the air flow. The mean velocity deficit profile determined from these measurements at x = 20h compares quite well to a similarity solution profile obtained by Counihan, Hunt & Jackson (1974). Their analysis was extended in the present investigation to the concentration field. The similarity solution obtained for the mean concentration compares well to profiles measured at x = 12h, 15h, and 20h, up to about three obstacle heights above the wall.

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.

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
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