Abstract
This study investigates the extended Hybrid Laminar Flow Control (xHLFC) concept, which relocates active boundary layer suction to the airfoil’s adverse pressure gradient region to enhance aerodynamic robustness and simplifies system integration. An xHLFC airfoil was derived via genetic optimization for a swept mid-range configuration, demonstrating good Mach number drag divergence characteristics compared to a conventional Natural Laminar Flow (NLF) counterpart. To experimentally validate the concept under transition-relevant conditions, a wind tunnel model was designed using an N-factor-matched scaling approach to reproduce cruise-flight instability amplification rates (Tollmien-Schlichting and Crossflow) at reduced Reynolds numbers. The novelty lies in the fully integrated suction panel, additively manufactured using Triply Periodic Minimal Surfaces (TPMS) to monolithically realize structural stiffness and tailored internal pressure loss. Wind tunnel tests confirm the successful scaling and flow fidelity of the model. Active suction extends the laminar flow, resulting in a drag reduction of up to 49 %. A preliminary reconstruction of the mean wall-normal suction velocity, based on the Preist model and measured pressure differential, validates the overall functionality of the TPMS panel. However, the observed spanwise non-uniform transition pattern highlights limitations attributed to local porosity inhomogeneity, indicating a need for spatially resolved porosity assessment in future additively manufactured flow control systems.
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