Turbulent Flow Over Wavy Surfaces : Unravelling Differences Between Water and Rayleigh Waves

We recently published “Turbulent Flow Over Wavy Surfaces : Unravelling Differences Between Water and Rayleigh Waves” in AIAA SCITECH 2025 Forum.

Compared to the canonical problem of the turbulent boundary layer over a flat surface, the flow interaction with a wavy surface presents additional complexities, such as modified patterns of flow separation and reattachment, which enhance turbulence intensity and mixing. By inducing optimal interactions between the flow and the wavy surface, it is possible to enhance the efficiency and performance of aerospace systems and improve mixing in various engineering and environmental applications. Notable examples of wavy surfaces include Rayleigh waves, such as those found in dolphin skin and water waves. Research on dolphin skin suggests that elastic waves can be leveraged to reduce drag using either passive or active flow control techniques, and wind-wave interaction is a key process in shaping environmental flow. Numerous experimental and simulation studies have been conducted on wind-water interfaces, where the tangential motion of surface particles follows the direction of wave propagation. However, the same level of understanding is not available for Rayleigh waves, in which the tangential motion of surface particles follows retrograde motion, contrary to gravity waves. This study explores such a problem using a direct numerical simulation (DNS) of turbulent Couette flows over wavy Rayleigh surfaces with a wave age of 7.55 and material properties. We analyze the turbulence flow characteristics in proximity to compliant surfaces to identify unique near-surface flow patterns near surface elastic waves compared to those observed in water waves. These insights can potentially inform the future design of surface actuators and contribute to the development of non-local techniques for flow control.