Control for Turbulent Drag Reduction by Wall-normal Blowing and Suction
Date:
Abstract: Turbulent drag is one of the most prominent flow challenges currently inhibiting advances in aircraft performance. Surface texture, porosity, and compliance have shown limited success in passively controlling turbulent drag, but these approaches are largely limited to single/static configurations or theoretical demonstrations. Recent advances in mechanical metamaterials and phononic crystals have shown that novel dynamic properties can be engineered into the surface and subsurface of materials, suggesting an enticing possibility for structures that can generate passive, local, adaptive, and dynamic alterations to complex flows. Here, we probe the idea of fluid-metamaterial interaction, by computationally understanding the interaction of phononic materials with near-wall flow coherences in turbulent wall-bounded flows, where the phononic material and the flow dynamics are characterized by similar spatio-temporal scales, with the goal of turbulent drag reduction. First, we analyze near-wall flow coherences in the turbulent flow to identify dominant time and length scales, then design mass-spring models of phononic materials that respond at those same scales. As an initial approximation of the phononic material response to turbulent wall pressure, we explore the effects of prescribed wall-normal velocity oscillations at the channel wall, in the form of a blowing-suction boundary conditions. Simulations show that harmonic streamwise oscillations cause drag reduction in certain frequency-wavelength-amplitude regimes. Mass-spring models of defect-based phononic materials are then designed to match these frequency-wavelength-amplitude responses. We then simulate the interaction between multiple phononic materials in the subsurface of the channel (i.e., a phononic subsurface or “Psub”), with iteratively increasing complexity. Results show regions of drag reduction, by calculating the turbulent shear stress at the wall as a function of phononic material parameters.
Citation: V. Ramakrishnan, “Computational study of fluid-metamaterial interaction between phononic materials and a turbulent channel flow”, APS DFD 2025: 78th Annual Meeting of the Division of Fluid Dynamics, Houston, TX, November 23 - 25, 2025.