Finite-sized rigid spheres in turbulent Taylor-Couette flow

Abstract

We report on the modification of drag by neutrally buoyant spherical particles in highly turbulent Taylor-Couette flow. These particles can be used to disentangle the effects of size, deformability, and volume fraction on the drag, when contrasted with the drag for bubbly flows. We find that rigid spheres hardly change the drag of the system beyond the trivial viscosity effects caused by replacing the working fluid with particles. The size of the particle has a marginal effect on the drag, with smaller diameter particles showing only slightly lower drag. Increasing the particle volume fraction shows a net drag increase as the effective viscosity of the fluid is also increased. The increase in drag for increasing particle volume fraction is corroborated by performing laser Doppler anemometry where we find that the turbulent velocity fluctuations also increase with increasing volume fraction. In contrast with rigid spheres, for bubbles the effective drag reduction also increases with increasing Reynolds number. Bubbles are also much more effective in reducing the overall drag.

15 pages, 17 figures

References in corpus (9)

• Multiple states in highly turbulent Taylor-Couette flow
• Bubble drag reduction requires large bubbles
• Quantifying turbulence induced segregation of inertial particles
• Universal Scaling Laws for Dense Particle Suspensions in Turbulent Wall-Bounded Flows
• Microbubbles and microparticles are not faithful tracers of turbulent acceleration
• Dispersion of air bubbles in isotropic turbulence
• Applying Laser Doppler Anemometry inside a Taylor-Couette geometry - Using a ray-tracer to correct for curvature effects
• The clustering morphology of freely rising deformable bubbles
• Lagrangian velocity and acceleration correlations of large inertial particles in a closed turbulent flow