(81c) Characterization of Mixing in the EPA Baffled Flask for Dispersion Effectiveness Testing

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 field in large and small vertical cross sections of the flask for each rotation speed were obtained. The 1D energy spectra indicates a nearly isotropic flow in the BF and 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 N = 100-250 rpm, of which it is slightly larger than the one estimated by prior studies using single-point velocity measurement techniques for N = 100 and 200 rpm. 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,  and Kolmogorov microscale in the flasks were correlated to the rotation speed.