Addition of polymers to single-phase turbulent flows leads to a significant drag reduction. Based on the percentage of achieved drag reduction (DR) in the flow, the viscoelastic flows are categorized as low drag reduction (LDR) and high drag reduction (HDR) regimes.
The motive of this study is to perform extensive large-scale direct numerical simulations (DNS) of turbulent bubbly channel flows using a fully parallelized 3D finite-difference/front-tracking method to examine the effects of polymer additives (i.e., viscoelasticity) on dynamics of bubbly flows in the presence of clean and surfactant contaminated bubbles in HDR regime including the maximum drag reduction asymptote (MDR).
In this method, the incompressible Navier-Stokes equations are solved using a very efficient FFT-based pressure projection method that allows for massively parallel simulations of turbulent flows. The Navier-Stokes equations are solved fully coupled with the governing equations of interfacial and bulk surfactant concentrations and the FENE-P viscoelastic model. A non-linear equation of state is used to relate surface tension to interfacial surfactant concentration.
KTH Royal Institute of Technology, Stockholm, Sweden;
Finnish Meteorological Institute, Finland.