Wall-layer structure and drag reduction

摘要: When drag-reducing additives are confined entirely to the linear sublayer of a turbulent channel flow water, both spanwise spacing and bursting rate wall-layer structure same as those for water there is no evidence drag reduction. Drag reduction measured downstream location where injected into begin mix in significant quantities with buffer region (10 y + The superscript denotes dimensionless quantity scaled kinematic viscosity ν wall shear velocity v * = (τ w /ρ) ½ . flow. At streamwise locations does occur fluid not yet uniformly mixed flow, streak increases average decreases. decrease larger than corresponding increase spacing. like homogeneous, mixed, solution. Thus, have direct effect on processes appears passive role interaction inner outer portions layer.