Open AccessCharacterization of Turbulent Properties in the EPA Baffled Flask for Dispersion Effectiveness Testing
Author(s) -
Lin Zhao,
Bing Wang,
Piero M. Armenante,
Robyn N. Conmy,
Michel C. Boufadel
Publication year - 2016
Publication title -
journal of environmental engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.438
H-Index - 95
eISSN - 1943-7870
pISSN - 0733-9372
DOI - 10.1061/(asce)ee.1943-7870.0001000
Subject(s) - microscale chemistry , particle image velocimetry , rotation (mathematics) , turbulence , kolmogorov microscales , dissipation , rotational speed , mechanics , laboratory flask , taylor microscale , mixing (physics) , dispersion (optics) , environmental science , materials science , physics , turbulence kinetic energy , chemistry , optics , thermodynamics , classical mechanics , mathematics , geometry , mathematics education , quantum mechanics , k omega turbulence model
The baffled flask test (BFT) has been proposed by United States Environmental Protection Agency to be adopted as the official standard protocol for testing dispersant effectiveness. The mixing energy in the baffled flask is investigated in this paper. Particle image velocimetry (PIV) was used to measure the water velocity in the flask placed at an orbital shaker that was rotated at seven rotation speeds: 100, 125, 150, 160, 170, 200, and 250 rpm. Two dimensional velocity fields in large and small vertical cross sections of the flask for each rotation speed were obtained. The one-dimensional (1D) energy spectra indicates the existence of inertial subrange. The estimated average energy dissipation rates were in the range 7.65×10 -3 to 4 W/kg for rotation speeds of Ω=100-250 rpm, of which it is larger than the one estimated by prior studies using single-point velocity measurement techniques for Ω=100 and 200 rpm. Factors such as instruments used, velocity components measured, and different analysis methods could contribute to the discrepancies in the results. The Kolmogorov scale estimated in this study for all seven rotation speeds approached the size of oil droplets observed at sea, which is 50-400 μm. The average energy dissipation rate, ε and Kolmogorov microscale, η, in the flasks were correlated to the rotation speed, and it was found thatε ¯ = 9.0 × 10 - 5Exp (0.043Ω) with R 2 = 0.97 and η ¯ = 1 , 463 Exp (-0.015Ω) with R 2 = 0.98.