Effect of zero-mean-shear turbulence on rise velocity of in-chain bubbles from marine natural seeps

This paper reports on a laboratory experiment that investigates the impact of ocean turbulence on the rise velocity of bubbles released from natural seeps. To simulate the turbulence conditions of ocean bottoms, we used an oscillating grid-stirred turbulence (OGT) tank to generate nearly homogeneous and isotropic turbulence (HIT) with a range of turbulence dissipation rates. By isolating the effect of zero-mean-shear turbulence on the bubble rise from the effect of cross flows, we found that the presence of turbulence reduced the bubble rise velocity by up to 19% across six different gas flow rates. Our data show a linear relationship between the normalized bubble rise velocity and the log-value of the normalized turbulence dissipation rate, with two different slopes. Our analysis suggests that turbulence increased the horizontal motion of the bubbles, causing them to scatter laterally, thereby reducing their rise velocity. Lastly, we propose a semi-empirical equation that can be used to calculate the rise velocity of in-chain bubbles in turbulent waters. These findings have important implications for our understanding of the role of turbulence in the transport and fate of seep bubbles in ocean waters.