Geometric optimisation of miniature vortex generators on a flat plate boundary layer

This study presents a geometric optimisation of rectangular miniature vortex generators (MVGs) on a zero-pressure gradient flat plate, with the primary objective of delaying laminar-turbulent transition. An efficient numerical framework, coupling flow simulation with local linear stability analysis, was utilized within a multi-objective Bayesian optimisation algorithm to systematically vary MVG height, angle, and spanwise spacing. The optimisation identified a new set of Pareto-optimal configurations that significantly outperform previously studied designs, confirming that earlier setups were non-optimal. The most effective configurations feature taller and more sparsely spaced MVGs, which successfully delayed transition beyond the entire computational domain. Analysis of the flow field reveals that this superior performance is attributed to the generation of a more robust vortex system; the optimised geometry allows for the formation of three distinct vortex pairs, whose positive interaction and merging sustains the stabilising streaks for a much greater downstream distance. These findings demonstrate that optimised MVGs can achieve a far greater transition delay, suggesting the potential for substantial skin friction drag reduction in optimal scenarios.