Direct Numerical Simulation of Drag-Reducing Turbulent Boundary Layer of Viscoelastic Fluid

1st Report, Mean Velocity Profiles and Turbulence Statistics

Abstract

Direct numerical simulation of a zero-pressure gradient drag-reducing turbulent boundary layer of viscoelastic solutions was performed using constitutive equation models such as the Oldroyd-B and Giesekus models. First, the streamwise variations in boundary layer parameters such as the shape factor and friction coefficient were clarified. Next, mean velocity profiles and turbulence statistics at the different streamwise locations were discussed using both inner and outer scaling. The maximum drag reduction ratio for the Oldroyd-B model, which has the higher elongational viscosity, is larger than that for the Giesekus model. The distinct difference in turbulence statistics near the wall between the Oldroyd-B model and Newtonian fluid is observed, as reported in the drag-reducing turbulent channel flow, while the difference between the Giesekus model and Newtonian fluid is slight in this study. On the other hand, in the outer region, distributions of mean velocity and turbulence statistics for both the Oldroyd-B and Giesekus models are similar to those for Newtonian fluid.