Drag Reduction Through Boundary Layer Analysis on Flow Over Bi-Textured Thin Plates

In the present work, laminar flow over one-dimensional bi-textured thin plates is numerically studied, focusing on the skin friction coefficient and its role in drag reduction for bio-mimetic, energy-efficient surfaces. Using the Finite Volume Method, the methodology is benchmarked against the Blasius solution and analyzes flow over anisotropic patterned plates, particularly variations in boundary layer thickness and skin friction due to alternating no-slip-perfect-slip patterns, starting with a no-slip pattern at the leading edge. The effect of increasing Reynolds numbers (1 × 105 < Re < 2 × 105) shows stepped boundary layer growth at pattern junctions, with up to 20% drag reduction at a Reynolds number of 1.3 × 105 compared to its classical no-slip boundary condition counterpart. The study also examines how changes in the shear-free area ratio and periodicity affect skin friction distribution, finding reduced drag with increased shear-free areas and increased effective drag-contributing length with more periods. For a shear-free area ratio value of 0.4 with 2 periods and for 4 periods with a shear-free area ratio value of 0.25 drag reduction to Blasius solution where found to be 15% and 12% respectively at Re = 1 × 105. Results, also suggest that the larger the number of periods on a textured plate the closer it behaves to the classical flat plate. This research suggests an alternative method for estimating average skin friction, moving away from traditional equivalent slip formulations to consider near-surface flow dynamics, providing insights crucial for designing drag-reducing fluid dynamic surfaces.