Drag Reduction in Bubbly Taylor-Couette Turbulence


In Taylor-Couette flow the total energy dissipation rate and therefore the drag can be determined by measuring the torque on the system. We do so for Reynolds numbers between Re textequals 7$times$10 4 and Re textequals 10 6 after having injected (i) small bubbles (R textequals 1 mm) up to a volume concentration of $α$textequals5textpercent and (ii) buoyant particles ($ǎrrho$p/$řrho$l textequals 0.14) of comparable volume concentration. In case (i) we observe a crossover from little drag reduction at smaller Re to strong drag reduction up to 20textpercent at Re textequals 10 6. In case (ii) we observe at most little drag reduction throughout. Several theoretical models for bubbly drag reduction are discussed in view of our findings.

Physical Review Letters 94: 044501-1–044501-4