Near Wall Turbulence Characteristics of a Drag Reducing Polymer Fluid Flow in Concentric Annulus Using CFD

Abstract

A CFD simulation was conducted to analyze the near wall turbulence characteristics of a drag reducing (DR) polymer fluid (0.12% V/V) flow through concentric annulus. The continuity and momentum equations were solved by using a commercial CFD package (CFX 14) with the Shear-Stress-Transport (SST) model option. The simulation results were compared to the experimental data obtained by using high resolution Particle Image Velocimetry (PIV) analyses of drag reducing polymer fluid flow in a horizontal concentric annulus. A fully developed turbulent flow of water through a horizontal flow loop (ID = 9.5 cm) with concentric annular geometry (inner to outer pipe radius ratio = 0.4) was used for comparison purpose. The flow rates ranged from 3.92 to 5.95 kg/s. Drag reducing PHPA solutions behaved as a power law fluid with the rheological model (μ = Kγn−1) for the shear rate of 1/s to 600/s. Bulk and near wall velocity profile obtained from simulation showed good agreements with the experimental data. Drag reducing polymer reduce the Reynolds stresses level due to weaker and fewer turbulent eddies formation near the wall. Results of the simulation study also showed that if the flow rates of power law fluid increased from 3.92 to 5.95 kg/s, the drag reduction in the annuli is increased from 10% to 20% compared to water case indicating the strong damping to turbulent kinetic energy in the flow. The CFD analyses using SST model is computationally inexpensive and, therefore, can be conveniently used for investigating the flow characteristics of drag reducing polymer fluids in concentric annulus.