3-D Visualization of a Zero-Pressure Gradient Turbulent Boundary Layer

Abstract

The application of a novel technique for 3-D visualization of a zero-pressure gradient turbulent boundary layer is discussed. Measurements of a 1.65δ x 1.65δ x 1.65δ volume were taken at a flow speed of 96 ft/s, Reθ ~ 5900, and δ = 1.21 in, in a 2 ft x 2 ft open circuit wind tunnel. Many different mechanisms for flow seeding were explored in order to find the most sufficient technique. Experiments were run to ensure that the boundary layer was not being adversely affected by the flow seeding technique and that a zero-pressure gradient was being maintained. 2-D PIV experiments were also run to give a quantitative comparison to the qualitative data from the 3-D measurement technique. Resulting 3-D measurements illustrated the existence of large-scale structures in the boundary layer, giving a unique look at a flow speed and volume combination previously uncharted in 3-D boundary layer measurements. The quality of the 3-D measurements proved that the flow seeding technique used in these experiments was satisfactory and laid the foundation for future measurements in a variety of flow conditions.