Turbulent Boundary Layer Flow Over a Bump

Abstract

Turbulent boundary layers (TBLs) are critical to the performance and efficiency of many engineering systems, especially in aerospace and turbomachinery applications. While two-dimensional (2D) TBLs under zero-pressure-gradient (ZPG) conditions are well understood, real-world boundary layers often experience complex three-dimensional (3D) effects due to surface curvature and pressure gradients. These conditions introduce flow skewing, anisotropy, and deviations from classical equilibrium behavior, making them difficult to model and predict accurately.

This thesis examines the behavior of 3D turbulent boundary layers over the BeVERLI Hill, a three-dimensional surface geometry tested in an asymmetric configuration to explore how pressure gradients and flow skewing alter the development of turbulence. Experimental measurements were acquired at multiple locations across the surface to capture both near-wall and outer-layer flow behavior under varying degrees of pressure gradient and surface curvature.

The findings reveal that, while near-wall turbulence retains some two-dimensional features, the outer layer exhibits substantial changes depending on the local pressure gradient and degree of flow skewing. Favorable pressure gradients tend to suppress turbulence and induce relaminarization-like effects, while adverse gradients promote stronger turbulence and signs of separation. In regions with significant three-dimensionality, the boundary layer separates into distinct inner and outer zones, with misalignment in shear direction and sustained cross-component momentum transfer.

Overall, the study provides new understanding of how complex surface geometry and pressure fields shape 3D turbulent boundary layers, contributing high-fidelity experimental data to aid in turbulence model development and validation.