On the link between experimentally‐measured turbulence quantities and polymer‐induced drag reduction in pipe flows

Abstract

In this study, we investigate the hydrodynamics of polymer-induced drag reduction in horizontal turbulent pipe flows. We provide spatiotemporally resolved information of velocity and its gradients obtained with particle image velocimetry (PIV) measurements in solutions of water with dissolved polyethylene oxide (PEO) of three different molecular weights, at various dilute concentrations and with flow Reynolds numbers from 35, 000 to 210, 000. We find that the local magnitudes of important turbulent flow variables correlate with the measured levels of drag reduction irrespective of the flow Reynolds number, polymer weight and concentration. Contour maps illustrate the spatial characteristics of this correlation. A relationship between the drag reduction and the turbulent flow variables is found. The effects of the polymer molecular weight, its concentration and the Reynolds number on the flow are further examined through joint probability distributions of the fluctuations of the streamwise and spanwise velocity components.

A combined experimental and computational study of the flow characteristics in a Type B aortic dissection: Effect of primary and secondary tear size

“…The slight mismatch in the refractive indices was corrected by an image anti-distortion correction post-processing algorithm. Such refractive-index matching approach is commonly used in laser-based flow dynamics imaging measurements in various flow applications (Charogiannis et al, 2015;Voulgaropoulos et al, 2019).…”

“…A sheet-optic arrangement generated light sheets with a thickness of 0.1 mm. More details on the laser system can be found in Voulgaropoulos et al (2019).…”

Improving the efficiency of water fire extinguishing systems operation by using guanidine polymers

“…In addition, the author tries to focus on a new vision of classical theories in the field of research. The authors of paper [6] showed that polymers cause a decrease in resistance in horizontal turbulent flows in pipes. They established a connection between a decrease in resistance and variables of a turbulent flow [6].…”

“…The authors of paper [6] showed that polymers cause a decrease in resistance in horizontal turbulent flows in pipes. They established a connection between a decrease in resistance and variables of a turbulent flow [6]. They showed that local values of some variables of a turbulent flow correlate with measured levels of a resistance decrease, regardless of the Reynolds number.…”

POD analysis of oscillating grid turbulence in water and shear thinning polymer solution

“…Polymers are widely studied as flow additives because they are at the origin of the non‐Newtonian properties of the fluid in many applications, and also because the wide range of existing polymers allows to use them to build model fluids reproducing the behaviors of other non‐Newtonian media 6 7‐10 and leads to the well‐known drag reduction phenomenon, among others 11,12 13,14 : the viscosity of the solution decreases with increasing shear rate.…”