3-D Flow Visualization of a Turbulent Boundary Layer

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 inches 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 suitable technique. Experiments were run to ensure that the boundary layer was not being adversely affected by the flow seeding technique and that a zeropressure gradient was being maintained. 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.