Triangular Porous Texturing Elements for Skin Friction Reduction

This study investigates the effect of Triangular Porous Texturing (TPT) elements on a turbulent boundary layer. Three flat plate models featuring a smooth baseline, an array of solid triangular prisms, and an array of TPT elements, were tested in an open-circuit wind tunnel (U_∞ = 13 m/s, I = 0.5%). A 400-grit sandpaper strip forced boundary layer transition at the leading edge, x = 0 m, and the roughening arrays spanned x = 0.0346m – 0.1154m (Re_x ≈ 3×10⁴-1×10⁵). Compared to the smooth flat plate, the solid triangular prisms and TPT elements reduced skin friction by 19.3% and 15.3%, respectively. Flow field measurements, captured with planar Particle Image Velocimetry (PIV), reveal that solid triangular prisms suppress near-wall turbulent bursts, whereas the TPT bleed-jets boost momentum transport in the lower log layer of the turbulent boundary layer. Solid triangular prisms are optimal for cruise conditions, offering drag reduction benefits. TPT elements balance skin friction reduction with the added benefit of delayed flow separation, making it well suited for applications requiring maneuverability under adverse pressure gradients.