Hybrid study of Vortex Lines in Transitional Pipe Flow

Concentrated vortex lines spontaneously arise in many flows -- such as turbulence -- acting as organizing features of the flow. In order to study the interactions between vortices and background flows in a controlled environment, we have built an experimental apparatus to generate and track streamwise vortices in pipe flow at Reynolds numbers up to 2000. We image the resulting flows in 3D using a combination of fluorescently dyed vortex cores and randomly distributed tracer particles. Our experimental results are compared to a Navier-Stokes simulation of the same scenario. Our setup allows us the unique opportunity to analyze 3D flow fields in experiments and simulations using identical methods. This research extends the geometric analysis of vortices into more dynamic flow environments.