Reynolds number dependence of drag reduction by rodlike polymers

Maximum drag reduction simulation using rodlike polymers.

Simulations of maximum drag reduction (MDR) in channel flow using constitutive equations for suspensions of noninteracting rods predict a few-fold larger turbulent kinetic energy than in experiments using rodlike polymers. These differences are attributed to the neglect of interactions between polymers in the simulations. Despite these inconsistencies the simulations correctly reproduce the ess...

Drag reduction by polymers in wall bounded turbulence.

We elucidate the mechanism of drag reduction by polymers in turbulent wall-bounded flows: while momentum is produced at a fixed rate by the forcing, polymer stretching results in the suppression of momentum flux to the wall. On the basis of the equations of fluid mechanics we develop the phenomenology of the "maximum drag reduction asymptote" which is the maximum drag reduction attained by poly...

Superposition of drag reduction due to riblets on drag reduction due to polymers

Turbulent Drag Reduction by Spanwise Wall Oscillations

The objective of this paper is to examine the effectiveness of wall oscillation as a control scheme of drag reduction. Two flow configurations are considered: constant flow rate and constant mean pressure gradient. The Navier-Stokes equations are solved using Fourier-Chebyshev spectral methods and the oscillation in sinusoidal form is enforced on the walls through boundary conditions for the sp...

The Lift and Drag on a Flat Plate at Low Reynolds Number via Variational Methods* By

The problem of determining the low Reynolds number lift and drag on a flat plate in Oseen flow is treated by the application of a variational principle due to Levine and Schwinger. This approach circumvents the difficulty which has limited previous results to drastically low values of the Reynolds number. In particular, an asymptotic form for the drag coefficient is derived, and found to be sui...