Better Bubble Process Modeling: Improved Bubble Hydrodynamics Parameterization

Proper modeling of bubble-mediated processes requires both good observations and parameterizations. Although one of the most important bubble parameterizations is the rise velocity, V B , published studies of V B in natural waters (i.e., sea water, marsh water, lake water) are largely unavailable; most studies are for clean distilled water. Also poorly studied is the effect of temperature, T on V B . An examination of V B in seawater showed that for bubbles with radius, r > 700 μm, V B was not significantly different from the value for distilled water. Analysis of V B with depth, showed a decrease in V B as the bubble rose over a distance, suggesting bubble contamination can take a significant time (1 m or more), and this time increases with increasingr. Also, hydrodynamic contamination was fastest in marsh and lake waters, where the water was collected close to sediments. Experiments to measure V B over the range 0 < T < 40°C showed that for non-oscillating bubbles, V B (T) increases with T; while for larger bubbles, V B (T) decreases with T due to oscillations. A three-part parameterization of V B (r,T) with transitions at Re = 1, 540, and the onset of oscillations (itself T dependent) was developed.