Rising speed and dissolution rate of a carbon dioxide bubble in slightly contaminated water

The rising speed and dissolution rate of a carbon dioxide bubble in slightl y contaminated water were investigated experimentally and numerically We de veloped an experimental system that uses a charged-coupled device (CCD) cam era coupled with a microscope to track the rising bubble. By precisely meas uring the bubble size and rising speed, we were able to accurately estimate the drag coefficient and the Sherwood number for the dissolution rate of g as bubbles at Reynolds numbers below 100 in the transient regime, where the bubble changes from behaving as a fluid sphere to behaving as a solid part icle. We also numerically estimated the drag coefficient and Sherwood numbe r of the 'stagnant cap model' by directly solving the coupled Navier-Stokes and convection-diffusion equations. We compared our experimental results w ith our numerical results and proposed equations for estimating the drag co efficient and Sherwood number of the bubble affected by contamination and c larified that the gas-liquid interface of the carbon dioxide bubble in wate r is immobile. We also show that the experimental and numerical results are in good agreement and the stagnant cap model can explain the mechanism of the transient process where the bubble behaviour changes from that of a flu id sphere to that of a solid particle.