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=7 x 10(4) and Re=10(6) after having injected (i) small bubbles (R=1 mm) up to a volume concentration of alpha=5% and (ii) buoyant particles (rhop/rhol=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 20% at Re=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.
van den Berg
Thomas H
TH
Department of Applied Physics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. t.h.vandenberg@tnw.utwente.nl
Luther
Stefan
S
Lathrop
Daniel P
DP
Lohse
Detlef
D