Equilibrium and Non-Equilibrium Entraining Bubbly Flow Regimes around a Ship
Abstract
Approved for Public ReleaseA five-year fundamental research effort to elucidate and characterize the equilibrium and non- equilibrium bubbly-flow regimes around a surface ship. Bubbly flows around a ship are common phenomena associated with myriad near-surface turbulent flows, their interactions with the hull and waves, as well as multiple two-phase flow mechanisms such as entrainment, fragmentation, degassing and coalescence. Examples of ship bubbly flows include violent flows immediately be- hind the stern, breaking divergent waves, and bubble sweep down at the bow. Of fundamental scientific interest and important practical application are the spatial and temporal variations of the total bubble volume and the bubble size spectrum. While advances in turbulence closure models, notably large eddy simulation (LES) or unsteady Reynolds-averaged Navier-Stokes simulation (uRANS), have allowed ship-scale simulation of turbulent flow fields, advanced bubble-population closure/source/sink models are needed to predict bubble populations around ships. Essential to the development of these closure models is fundamental understanding of bubbly-flow regimes, delineated by the equilibrium/non-equilibrium of the total bubble volume and the equilibrium/non- equilibrium of its size spectrum. To obtain this understanding and develop effective closure models, we identify a number of key research tasks on the critical path. First, the population balance equation (PBE) will be applied to different entraining flows around ships to obtain qualitative understanding of the spatial extent of bubbly-flow regimes in different entraining flows and identify transitions among these regimes. We will then perform direct numerical simulation (DNS) of carefully targeted canonical flows to characterize the bubble population within each regime. Along with the DNS solver, an important numerical tool is our Eulerian label advection (ELA) technique which allows us to separately quantify the different physical mechanisms that evolve the bubble population. Third, we will work in collaboration with bubbly-flow LES development to study the bubbly-flow regimes on larger scales, where LES of a large-scale flow is interfaced with DNS of small regionsof interest. This will be particularly useful for studying transitions between regimes in multi-regime bubbly flows. Throughout these tasks, we will obtain corroboration with large-scale laboratory or field measurements, and LES and uRANS predictions. The fourth key task of this research effort is to collaborate with LES and uRANS development to implement and evaluate bubble-population closure models developed based on this new fundamental understanding. We intended to develop regime dependent physics-based closure modelsfor large scale computational ship hydrodynamics, with the goal of allowing accurate prediction of bubble population volumes and size spectra in the flow around a ship.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 15, 2023
- Source ID
- N000142412076
Entities
People
- Dick K P Yue
Organizations
- Massachusetts Institute of Technology
- Office of Naval Research
- United States Navy