The effectiveness of targeted polymer injection for turbulent drag redution

The effect of polymer drag reduction by targeted injection is studied in comparison to that of a uniform concentration (or polymer ocean) in a turbulent channel flow. Direct Numerical Simulations are performed using a pseudo-spectral method to solve the coupled equations of a viscoelastic fluid using the FENE-P model. Light and heavy particles are used to carry the polymer in some cases, and polymer is artificially injected into specific flow regions in the other cases. To study drag reduction, the global mass flux through the channel is computed over time and compared to a turbulent channel with no polymer. The overall effectiveness of targeted polymer injection is presented based on mass flux and its effect on turbulent structures. Various factors are discussed including relevant time scales and a correlation between polymer concentration and drag-producing structures.