Development of Metal 3D-Printed Helium-Filled Soap Bubble Nozzles

Abstract

Particle Image Velocimetry (PIV) is a useful flow visualization technique to obtain instantaneous velocity measurements of a fluid. The use of traditional tracer particles for PIV measurements is limited to small field of view measurements. This is due to the fact that the illumination source energy is nominally low, and these particles have a finite scattering efficiency. One solution to overcome this limitation is to use neutrally buoyant helium-filled soap bubbles (HFSBs) as tracer particles. HFSBs have a higher light scattering intensity than traditional tracer particles, enabling larger field of view measurements for PIV. A HFSB system was designed and fabricated at Auburn University to enable velocity field measurements. Using knowledge of previous HFSB nozzle designs, a HFSB orifice nozzle was designed to be completely fabricated using a metal 3D printer. Additive manufacturing can be used to print multiple HFSB nozzles quickly and cost-effectively with little post-processing required. The HFSB nozzle was characterized by its bubble diameter and production rate as a function of air, helium, and soap flow rates. This characterization was compared to other working HFSB nozzles in literature to ensure the metal 3D printed nozzles produced comparable results. Models representing the bubble diameter based on the flow rates to one of the nozzles were created using a linear regression analysis. Finally, the robustness of metal additive manufacturing as a solution to produce consistent HFSB nozzles was evaluated using computed tomography. The nozzles presented in this thesis are the first metal 3D printed HFSB nozzles to not require modifications after printing that successfully produced helium-filled soap bubble tracer particles.