Modification of near-wall turbulence in turbulent boundary layers due to a perforated structure

This study investigates the potential of a perforated structure for the control of near-wall turbulence in turbulent boundary layers. The perforated structure consists of a perforated plate, underneath of which is a backing chamber. The near-wall turbulent structures were analyzed using hot-wire measurements. Different inner-scaled chamber volumes from V+ = 2.4 x 10(6) to 11.5 x 10(6) were considered to manipulate turbulent boundary layers at two Reynolds numbers of Re-theta = 1165 and 2294. The findings reveal significant effects of the perforated structure on near-wall turbulent structures. Statistical analysis utilizing a variable-interval time-averaging technique illustrated a reduction of up to about 9% in sweep and ejection intensity, a decrease in about 25% in ejection frequency, and a decrease in approximately 33.5% in sweep frequency within the near-wall region, y(+) <= 30, indicating that the perforated structure weakened burst events in this region. In addition, the perforated structure lifted the turbulence energy further from the wall. Consequently, there was a reduction of up to approximately 9% in turbulence intensities near the wall, contributing to locally diminished shear stresses and skin friction drag. When the inner-scaled chamber volume increased, the reduction in near-wall turbulence became more pronounced. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).