Three-Dimensional Effects of the Flow Over the BeVERLI Hill

Three-dimensional turbulent boundary layers are commonly generated in engineering flows exposed to surface curvature and spatially varying pressure gradients, yet their detailed structure and dynamics remain insufficiently understood. In this study, a canonical three-dimensional turbulent boundary layer developing over a complex hill geometry is examined using high-resolution Laser Doppler Velocimetry (LDV) measurements and complementary steady Reynolds-averaged Navier-Stokes simulations. Measurements were acquired at four streamwise stations in the Virginia Tech Stability Wind Tunnel at a hill-height-based Reynolds number of 250{,}000. The results reveal that while the near-wall region remains approximately collateral up to 60 wall-normal units, strong three-dimensional effects emerge farther from the wall in regions influenced by pressure gradients and curvature. These effects manifest as pronounced flow skewness, the formation of distinct inner and outer layers, and elevated turbulence anisotropy. Stations exposed to mild pressure gradients exhibit comparatively thinner and more two-dimensional boundary layers, whereas strong adverse pressure gradients promote outer-layer thickening and flow separation. The CFD simulations successfully reproduce the primary qualitative trends in mean flow, although quantitative deviations persist near separation. These findings demonstrate the significant sensitivity of turbulent boundary layer structure to three-dimensional pressure-gradient and surface curvature. The combined experimental and computational dataset provides a valuable reference for evaluating turbulence models in complex non-equilibrium flows and offers insight relevant to aerodynamic design applications involving separation-prone geometries.