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.

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.

Velocity and Concentration Field Measurements in Bubble-Driven Turbulent Liquid Flows

2011 ◽  
Author(s):  
Won Taek Jeong ◽  
Seung Jae Yi ◽  
Hyun Dong Kim ◽  
Sang Moon Kim ◽  
Kyung Chun Kim
Keyword(s):  
Gas Flow ◽  
Concentration Field ◽  
Vertical Motion ◽  
Field Measurements ◽  
Turbulent Dispersion ◽  
Mixing Efficiency ◽  
Water Tank ◽  
Time Resolved ◽  
Planar Laser ◽  
Liquid Flows

In this study, simultaneous measurements of velocity and concentration fields using the time-resolved particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) methods have conducted to investigate mixing characteristics in turbulent water flows driven by air bubbles in a cylindrical water tank. The flow rates of compressed air is changed from 1 to 5 L/min at 0.5 MPa and the corresponding range of bubble based Reynolds number is from 8,320 to 22,100. PLIF measurement results demonstrate that the mixing efficiency is enhanced with increase of gas flow rate. The sloshing motion of the free surface is also effective to the scalar mixing process since the vertical motion can be correlated with concentration fluctuation and increase turbulent dispersion process.

Simultaneous velocity and concentration field measurements of passive-scalar mixing in a confined rectangular jet

2007 ◽  
Vol 42 (6) ◽  
pp. 847-862 ◽  
Author(s):  
Hua Feng ◽  
Michael G. Olsen ◽  
James C. Hill ◽  
Rodney O. Fox
Keyword(s):  
Concentration Field ◽  
Field Measurements ◽  
Passive Scalar ◽  
Scalar Mixing ◽  
Rectangular Jet

A fast response miniature probe for wet steam flow field measurements

2016 ◽  
Vol 27 (12) ◽  
pp. 125901
Author(s):  
Ilias Bosdas ◽  
Michel Mansour ◽  
Anestis I Kalfas ◽  
Reza S Abhari
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Fast Response ◽  
Steam Flow ◽  
Wet Steam ◽  
Wet Steam Flow

Large-scale structure and entrainment in the supersonic mixing layer

1995 ◽  
Vol 284 ◽  
pp. 171-216 ◽  
Author(s):  
N. T. Clemens ◽  
M. G. Mungal
Keyword(s):  
Mach Number ◽  
High Speed ◽  
Large Scale ◽  
Mixture Fraction ◽  
Mixing Layer ◽  
Mie Scattering ◽  
Planar Laser ◽  
The Cross ◽  
Convective Mach Number ◽  
Stream Direction

Experiments were conducted in a two-stream planar mixing layer at convective Mach numbers,Mc, of 0.28, 0.42, 0.50, 0.62 and 0.79. Planar laser Mie scattering (PLMS) from a condensed alcohol fog and planar laser-induced fluorescence (PLIF) of nitric oxide were used for flow visualization in the side, plan and end views. The PLIF signals were also used to characterize the turbulent mixture fraction fluctuations.Visualizations using PLMS indicate a transition in the turbulent structure from quasi-two-dimensionality at low convective Mach number, to more random three-dimensionality for$M_c\geqslant 0.62$. A transition is also observed in the core and braid regions of the spanwise rollers as the convective Mach number increases from 0.28 to 0.62. A change in the entrainment mechanism with increasing compressibility is also indicated by signal intensity profiles and perspective views of the PLMS and PLIF images. These show that atMc= 0.28 the instantaneous mixture fraction field typically exhibits a gradient in the streamwise direction, but is more uniform in the cross-stream direction. AtMc= 0.62 and 0.79, however, the mixture fraction field is more streamwise uniform and with a gradient in the cross-stream direction. This change in the composition of the structures is indicative of different entrainment motions at the different compressibility conditions. The statistical results are consistent with the qualitative observations and suggest that compressibility acts to reduce the magnitude of the mixture fraction fluctuations, particularly on the high-speed edge of the layer.

Velocity and concentration field measurements in a turbulent, impinging flammable jet

2005 ◽  
Vol 60 (1) ◽  
pp. 219-230 ◽  
Author(s):  
A.D. Birch ◽  
R.P. Cleaver ◽  
M. Fairweather ◽  
G.K. Hargrave
Keyword(s):  
Concentration Field ◽  
Field Measurements

scholarly journals Robust, spatially scanning, open-path TDLAS hygrometer using retro-reflective foils for fast tomographic 2-D water vapour concentration field measurements

2014 ◽  
Vol 7 (12) ◽  
pp. 12827-12849 ◽  
Author(s):  
A. Seidel ◽  
S. Wagner ◽  
A. Dreizler ◽  
V. Ebert
Keyword(s):  
Water Vapour ◽  
Single Channel ◽  
Greenhouse Gas Emission ◽  
Concentration Field ◽  
Field Measurements ◽  
Tunable Diode Laser ◽  
Environmental Research ◽  
Soil Physics ◽  
Water Vapour Concentration ◽  
Vapour Concentration

Abstract. We have developed a fast, spatially direct scanning tunable diode laser absorption spectrometer (dTDLAS) that combines four polygon-mirror based scanning units with low-cost retro-reflective foils. With this instrument, tomographic measurements of absolute 2-D water vapour concentration profiles are possible without any calibration using a reference gas. A spatial area of 0.8 m × 0.8 m was covered, which allows for application in soil physics, where greenhouse gas emission from certain soil structures shall be monitored. The whole concentration field was measured with up to 2.5 Hz. In this paper, we present the setup and spectroscopic performance of the instrument regarding the influence of the polygon rotation speed and mode on the absorption signal. Homogeneous H2O distributions were measured and compared to a single channel, bi-static reference TDLAS spectrometer for validation of the instrument. Good accuracy and precision with errors of less than 6% of the absolute concentration and length and bandwidth normalized detection limits of up to 1.1 ppmv · m · √Hz−1 were achieved. The spectrometer is a robust and easy to set up instrument for tomographic reconstructions of 2-D-concentration fields that can be considered a good basis for future field measurements in environmental research.

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.

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