Polymer drag reduction in surfactant-contaminated turbulent bubbly channel flows

Bubbly turbulent drag reduction is a boundary layer effect.

In turbulent Taylor-Couette flow, the injection of bubbles reduces the overall drag. On the other hand, rough walls enhance the overall drag. In this work, we inject bubbles into turbulent Taylor-Couette flow with rough walls (with a Reynolds number up to 4 x 10(5), finding an enhancement of the dimensionless drag as compared to the case without bubbles. The dimensional drag is unchanged. As in...

Polymer flexibility and turbulent drag reduction.

Polymer-induced drag reduction is the phenomenon by which the friction factor of a turbulent flow is reduced by the addition of small amounts of high-molecular-weight linear polymers, which conformation in solution at rest can vary between randomly coiled and rodlike. It is well known that drag reduction is positively correlated to viscous stresses, which are generated by extended polymers. Rod...

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 c...

Turbulent drag reduction with polymer additive in rough pipes

Drag Reduction in Turbulent Flow of Polymer Solutions

Progress in understanding turbulent drag reduction by polymer additives has recently been made on several fronts. The near-wall dynamics of Newtonian turbulence is becoming better understood. Detailed computations of complex flows of model polymer solutions are now possible. Insights into the effects of viscoelasticity have been gained from a number of important model flows, and the understandi...