Opposition control with arrayed actuators in the near-wall region of a spatially developing turbulent boundary layer

Opposition control is known as an efficient mean to reduce drag in numerical simulations. However, even if the actuation principle follows simple spatio-temporal scales of turbulent motion, practical implementation of this concept results in very heavy technological constraints. Before going further in technological developments, it seems reasonable to assess numerically the efficiency of possible control devices by improving significantly the realism of simulations. In this study, the performance of an array of wall deforming actuators is investigated. The realistic wall deformations are allowed for by means of an Arbitrary Lagrangian-Eulerian (ALE) technique. The Direct Numerical Simulation (DNS) has been performed at friction Reynolds number of 368 on a spatially developing boundary layer configuration. The result analysis including averaging conditioned to actuator location and position shows that even if the actuator functioning in opposition control is validated, the drag reduction is not significant. The gains associated with an ideal opposition control are completely annihilated when a realistic actuator description is included in the simulation.