Direct Numerical Simulation of Mass Transfer from Spherical Bubbles: the Effect of Interface Contamination at Low Reynolds Numbers

The gas-liquid mass transfer from bubbles is estimated by Direct Numerical Simulation for fully contaminated bubbles behaving as solid spheres, partially contaminated spherical bubbles and clean spherical bubbles. Partial contamination of bubble interface is accounted by the Stagnant Cap Model to show the effect of the surfactant on hydrodynamic and mass transfer at low Reynolds number. Hydrodynamics results are validated by comparison with other works of the literature. The numerical mass transfer is then analysed in term of local and averaged Sherwood numbers. The comparison of DNS results with classical relations gives the good scaling of Sherwood with Pe1/3 and Pe1/2 respectively for solid sphere and clean bubble in creeping flow. For partially contaminated bubble and after validation of simulated drag coefficient, the effect of the contamination on mass transfer is shown for several Peclet numbers. A correlation for Sherwood number in function of contamination angle is then proposed in creeping flow.