Effect of turbulent integral scale on probability after-effect measurements

Berman, Neil S.; Tan, Hung; Guan, Dawei

doi:10.1088/0022-3735/17/12/027

Cited by 2 publications

(4 citation statements)

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“…Only two data points were available for PAM a t each location as each point required a lengthy repeat of the mixing and refilling procedure in the once-through system. The water data have been previously reported by Berman et al (1984). At y / x = 0.05 the measured 6 is less than one for both fluids and the dead time contribution is similar to that for the measurements at the jet center.…”

Section: (7)supporting

confidence: 75%

“…The probability of finding a particle in the first spot and not in the second spot can be experimentally measured, and this probability can be shown to be only a function of the dispersion. The theoretical development and some experiments using two photodetectors have been previously presented by Tan and Berman (1982) and Berman et al (1984). However, this method requires careful alignment and realignment for each setting of the space between the beams.…”

Section: Scopementioning

confidence: 99%

“…Since v and r, are related, it is convenient to integrate over dv instead of dr,. For a Gaussian velocity distribution the integration for homogeneous, isotropic, stationary turbulent flow with long thin parallelepiped scattering volumes is given by Berman et al (1984). When…”

Section: Aiche Journalmentioning

confidence: 99%

“…When the two beams are lined up in the mean flow direction, turbulent diffusion in the cross-flow direction leads to the probability that a particle will intersect only one of the beams rather than two. Measurements of this probability as a function of distance between the beams has been proposed as a method to determine the Lagrangian turbulence intensity and integral scale (Tan and Berman, 1982;Berman et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

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Lagrangian dispersion in turbulent flow from laser transit anemometry

Berman

1986

AIChE Journal

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The Lagrangian dispersion function in turbulent flow can be determined from measurements of the probability that a particle which is observed in a small volume is not observed in a similar size volume downstream. In this work a single-detector method is proposed to detect the particle arrivals in a multiple series of scattering volumes; the probability can be determined from the digital record over a long time compared to the turbulent integral time scale. The method is tested at locations downstream of a water spray nozzle and a submerged jet of dilute polymer solutions. N. S. BermanDepartment of Chemical and Bio Engineering Arizona State University Tempe, AZ 85287 SCOPEThe transport or dispersion of a passive contaminant by turbulent convection is a stochastic process that can be analyzed in an Eulerian or a Lagrangian frame of reference. Although the Lagrangian or random trajectory model is easiest to formulate, most measurements are Eulerian and are made at fixed points in space. One Lagrangian experiment is the measurement of the time of flight of particles between two points in the flow illuminated by a focused laser beam. When the points are close together so that the flight time is much less than the integral time scale of the flow, dispersion is not a parameter and the two frames of reference are the same. Most applications of a time of flight or laser transit anemometer are based upon the location of the two spots at such close proximity to each other.When the separation of the spots is of the order of the integral scale, not all the particles that are observed in the first spot will be seen in the second spot. The probability of finding a particle in the first spot and not in the second spot can be experimentally measured, and this probability can be shown to be only a function of the dispersion. The theoretical development and some experiments using two photodetectors have been previously presented by Tan and Berman (1982) and Berman et al. (1984). However, this method requires careful alignment and realignment for each setting of the space between the beams.In this paper the theoretical development of a simpler technique using a single photodetector is described and tested experimentally. The method to measure the turbulent mixing parameters in a Lagrangian framework can be valuable in studies of mixing in process equipment and in two-phase flows. CONCLUSIONS AND SIGNIFICANCEThe probability aftereffect is the combination of the ance to mean close to unity. There is a relationship events that some particles which were originally in the between the probability aftereffect and the mean first spot move out and that some particles move in square difference between the number of particles in from the surrounding fluid during the time of flight the first spot in the time interval and the number of parbetween the spots. In turbulent flow the probability disticles in a similar time interval but separated by the tribution of the particle arrivals within a sampling time flight time. AIChE Journalparticles that...

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Section: (7)supporting

confidence: 75%

Section: Scopementioning

confidence: 99%

Section: Aiche Journalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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