Controlling Motion of Levitating Drops in a Vertical Wind Tunnel Using Velocity Wells

Previous vertical wind tunnel experiments use a crosswire insert to create a velocity well, wherein the slowest wind velocity occurs at the center of the crosswire, allowing water drops to levitate at the center of the tunnel. However, such an approach has notable limitations: the wires gradually lose tension and sag, introducing unwanted turbulence, and the insert is difficult to modify for specialized applications. To address these issues, we develop a 3D-printed honeycomb insert, reducing turbulence, enhancing precision in generating a velocity gradient, and allowing for specialized modifications in the velocity well. In this work, we design a honeycomb insert capable of generating a unique velocity gradient to trap a water drop in a ring around the center of the wind tunnel. We assess the effectiveness of the honeycomb structure for future velocity well experiments using Computational Fluid Dynamics (CFD) simulations to generate velocity and vorticity surface plots. Our simulations indicate that with our current design, we can achieve and maintain the desired velocity gradient throughout most of the wind tunnel with minimal vorticity, validating the potential of the honeycomb structure for further applications.