How do the finite-size particles modify the drag in Taylor-Couette turbulent flow

Abstract

We experimentally investigate the drag modification by neutrally buoyant finite-size particles with various aspect ratios in a Taylor-Couette (TC) turbulent flow. The current Reynolds number, $Re$, ranges from $6.5\times 10^3$ to $2.6\times 10^4$, and the particle volume fraction, $\Phi$, is up to $10\%$. Particles with three kinds of aspect ratio, $\lambda$, are used: $\lambda =1/3$ (oblate), $\lambda =1$ (spherical) and $\lambda =3$ (prolate). Unlike the case of bubbly TC flow, we find that the suspended finite-size particles increase the drag of the TC system regardless of their aspect ratios. In addition, the normalized friction coefficient, $c_{f,\Phi }/c_{f,\Phi =0}$, decreases with increasing $Re$, the reason could be that in the current low volume fractions the turbulent stress becomes dominant at higher $Re$. As $Re$ increases, the particles distribute more evenly in the entire system, which results from both the greater turbulence intensity and the more pronounced finite-size effects of the particles at higher $Re$. Moreover, it is found that the variation of the particle aspect ratios leads to different particle collective effects. The suspended spherical particles, which tend to cluster near the walls and form a particle layer, significantly affect the boundary layer and result in maximum drag modification. The minimal drag modification is found in the oblate case, where the particles preferentially cluster in the bulk region, and thus the particle layer is absent. Based on the optical measurement results, it can be concluded that, in the low volume fraction ranges ($\Phi =0.5\%$ and $\Phi =2\%$ here), the larger drag modification is connected to the near-wall particle clustering. The present findings suggest that the particle shape plays a significant role in drag modification.

References in corpus (29)

• The Flow Physics of COVID-19
• High Reynolds number Taylor-Couette turbulence
• Turbulent channel flow of dense suspensions of neutrally-buoyant spheres
• Interface-resolved DNS of vertical particulate channel flow in the turbulent regime
• Bubble puzzles: From fundamentals to applications
• Bubbly and Buoyant Particle-Laden Turbulent Flows
• Shear thickening and migration in granular suspensions
• Multiple states in highly turbulent Taylor-Couette flow
• Bubble drag reduction requires large bubbles
• Laminar, turbulent and inertial shear-thickening regimes in channel flow of neutrally buoyant particle suspensions
• The importance of bubble deformability for strong drag reduction in bubbly turbulent Taylor-Couette flow
• Quantifying turbulence induced segregation of inertial particles
• Shear thickening in non-Brownian suspensions: an excluded volume effect
• The effect of particle density in turbulent channel flow laden with finite size particles in semi-dilute conditions
• Experimental investigation of the turbulence induced by a bubble swarm rising within an incident turbulence
• Universal Scaling Laws for Dense Particle Suspensions in Turbulent Wall-Bounded Flows
• Drag reduction in turbulent channel flow laden with finite-size oblate spheroids
• Shear-thinning and shear-thickening emulsions in shear flows
• Dispersion of air bubbles in isotropic turbulence
• Experimental investigation of turbulent suspensions of spherical particles in a square duct
• Global and local statistics in turbulent emulsions
• Scaling of global momentum transport in Taylor-Couette and pipe flow
• Kinematics and dynamics of freely rising spheroids at high Reynolds numbers
• The clustering morphology of freely rising deformable bubbles
• Catastrophic phase inversion in high-Reynolds number turbulent Taylor--Couette flow
• Strong alignment of prolate ellipsoids in Taylor-Couette flow
• Rotation of anisotropic particles in Rayleigh-Bénard turbulence
• Reduction of turbulent skin-friction drag by passively rotating discs
• Drag reduction in boiling Taylor-Couette turbulence

Cited by in corpus (5)

• The effect of particle anisotropy on the modulation of turbulent flows
• Recent developments of turbulent emulsions in Taylor-Couette flow
• Turbulence drag modulation by dispersed droplets in Taylor-Couette flow: the effects of the dispersed phase viscosity
• Numerical study on turbulence modulation of finite-size particles in plane-Couette flow
• Experimental investigation into Lagrangian statistics of droplets in homogeneous isotropic turbulence