Application of Transport Tube Method For Flow Visualization

The use of transport tubes is a relatively novel approach to creating visualizations of complex fluid flow phenomena. While this method of analysis has been used to study some limited flow cases, it needed to be applied to additional scenarios. The aim of this project was to test and apply the transport tube method for the purpose of studying a relevant, real-world flow case: underwater bubble plumes. The structure of the plumes was examined using this transport tube method, an analysis model that visualizes the transport of mass, momentum, and kinetic energy as three-dimensional (3D) tube structures. Numerical integration was used to create transport tubes based on mass flux, momentum flux, and kinetic energy flux vector fields. These tubes represent regions in 3D space where there is no flow of the corresponding quantity across the boundary of the tube. The transport tube method was implemented using codes developed in both MATLAB and Python. Before examining the primary case of interest, the method was first applied to multiple sample flow fields of varying conditions in order to gauge its accuracy. These sample cases included plane Couette flow and a basic wind dataset. Additionally, the analysis of both a laminar axisymmetric jet and wake provided a basis from which to consider the similarly structured bubble plume. The results for these preliminary cases indicated that the transport tube method was effective at identifying complex flow features (e.g., eddies) and transport patterns of mass, momentum, and kinetic energy in a variety of flows both 2D and 3D, laminar and turbulent. Once finally applied to the primary case of underwater bubble plumes, the transport tube method was able to demonstrate the mechanism by which momentum and kinetic energy were exchanged between the plume and the surrounding flow. Peeling events from the plumes created a dual plume structure that led to turbulent interactions between rising and falling plumes. The transport tube method was able to capture these peeling events and resulting effects for the three different bubble plume cases that were studied.