A Computational Study of Gaseous Jets Submerged in a Liquid Co-flow

Open Access
Author:
Fronzeo, Melissa A
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 17, 2017
Committee Members:
  • Michael P Kinzel, Thesis Advisor
  • Jules Washington Lindau V, Committee Member
  • Zachary P Berger, Committee Member
  • Philip John Morris, Committee Member
Keywords:
  • Computational fluid dynamics
  • multiphase flow
  • jets
  • submerged jets
  • ventilated cavities
Abstract:
The objective of this thesis is to apply Computational Fluid Dynamics (CFD) to multiphase flows to develop an understanding of the underlying flow mechanisms in artificially ventilated cavities and submerged gas jets. These studies are motivated by the need to better characterize these flows by understanding internal pressure and producing predictive regime mapping. The CFD is utilized to capture effects that are difficult to visualize experimentally. First, a study on the internal pressure of artificially ventilated cavities is displayed. Investigation into both twin and toroidal vortex closure modes indicates that several pressure regions develop within the cavities. These regions are found to correlate to cavity expansion and contraction that are a function of the closure mode. It is found that the constant pressure assumption within the cavity, used within semi-empirical theory and prediction, is only accurate to a certain degree. This thesis also contains several studies focused on multiphase submerged jets. First we examine the flow structure in the interaction of a gaseous jet with the ambient fluid tested at multiple densities. The main physical finding, consistent with previous observations, is that instabilities develop more rapidly at the gas-liquid interface with increased ambient fluid density. The dynamic response of the interface, partially driven by Rayleigh-Taylor and Kelvin-Helmholtz instabilities, drives other trends with increasing fluid density such as shorter Mach penetration and faster return to the ambient pressure. A breakdown of the jet spread and development is presented, along with the ambient fluid density effect on characteristics such as the size and spread of the mixing layer. Lastly, submerged gaseous jets in a liquid co-flow at varying freestream velocities and mass flow rates of the jet, the controlling parameters, are studied. The results show that there are several distinct regimes that form with respect to the controlling parameters. These regimes are classified based on their shared time-averaged and dynamic characteristics, after which a regime map, similar to those used in multiphase pipe flow, is constructed. This regime map is generated with several different methods in order to find the best predictive measure of what regime will form.