Evolution of a turbulent boundary layer over an axisymmetric body of revolution

Axisymmetric bodies of revolution (ABOR) are representative of many streamlined or aerodynamic platforms. The turbulent boundary layer (TBL) over such geometries is important as it contributes significantly to drag, structural vibrations and flow noise.  In this work, measurements of a TBL over an ABOR were made to study the effects of pressure gradient and curvature. Experiments were conducted in a wind tunnel with a friction Reynolds number range of  Re_τ = 1000 – 2600 over the geometry. A seeding rake with 100 nozzles dispersed helium-filled soap bubbles as tracers, which were illuminated by high-powered LED arrays for tracking by three high-speed cameras with acquisition frequencies up to 20 kHz. Three-dimensional Lagrangian Particle Tracking (LPT) was obtained using the shake-the-box algorithm, and ensemble bin-averaging of particle tracks provided turbulence statistics on a regular grid. 

 

The LPT results were validated against hot-wire and DNS, demonstrating the techniques high accuracy and robustness in capturing mean profiles. While the turbulence levels in the outer layer were well captured, some discrepancies were observed near the wall, indicating limitations in capturing small scales. As such, a detailed examination of the spectral content and resolvable flow scales at various wall heights is provided. The evolution of the mean profiles and 3D turbulence statistics along the body are presented together with the progression of large-scale structures.