title: Dynamics of single rising bubbles in neutrally buoyant liquid-solid suspensions.
abstract: We experimentally investigate the effect of particles on the dynamics of a gas bubble rising in a liquid-solid suspension while the particles are equally sized and neutrally buoyant. Using the Stokes number as a universal scale, we show that when a bubble rises through a suspension characterized by a low Stokes number (in our case, small particles), it will hardly collide with the particles and will experience the suspension as a pseudoclear liquid. On the other hand, when the Stokes number is high (large particles), the high particle inertia leads to direct collisions with the bubble. In that case, Newton's collision rule applies, and direct exchange of momentum and energy between the bubble and the particles occurs. We present a simple theory that describes the underlying mechanism determining the terminal bubble velocity.
authors.affiliation: Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
authors.forename: Nasim
authors.initials: N
authors.lastname: Hooshyar
authors.affiliation: Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
authors.forename: J Ruud
authors.initials: JR
authors.lastname: van Ommen
authors.affiliation: Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hamersma
authors.affiliation: Chemical Engineering Department, Princeton University, Princeton, New Jersey 08543, USA.
authors.forename: Sankaran
authors.initials: S
authors.lastname: Sundaresan
authors.affiliation: Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Mudde