DNS of mass transfer in turbulent bubbly flow in a vertical pipe

Abstract

The present research focuses on the DNS of mass transfer in gravity-driven turbulent bubbly flow in a vertical pipe, at a high Reynolds number (Re approximates to 1000). The objective is to compute the mass transfer coefficient included in the Sherwood number (Sh), as a function of the Reynolds (Re) number, Damkoler (Da) number for first-order chemical reaction, Schmidt (Sc) number, bubble fraction (BF), and confinement ratio (CR). Indeed, Sh = Sh(Re, Sc, BF, Da, CR), where Re=Re(Eo, Mo, BF, CR), Mo is the Morton number, Eo is the Eotvos number, and physical properties ratios are set to 100. A novel unstructured multiple-marker conservative level-set method for mass transfer in bubbly flows is employed to perform present simulations, in order to circunvent the numerical coalescence of bubbles. Navier-Stokes equations, conservative level-set (CLS) and chemical species transport equations are solved by the finite-volume method on collocated unstructured meshes. Thermodynamic equilibrium relates the concentration of chemical species at the interface by the so-called Henry's law. The pressure-velocity coupling is performed by the fractional-step projection method, whereas surface tension is computed by the continuous surface force model extended to the multiple markers CLS method. Verifications and validations of the numerical methods have been reported in our previous works. Based on our last efforts performed to research mass transfer in gravity-driven bubble swarms on unconfined domains, this research is a further step to include the wall's effect through the confinement ratio (CR). Thus, this work unravels the impact of CR on Sh, at Re = O(1000), whereas the remaining parameters are kept constant.