Simulating bubble dynamics in a buoyant system

Abstract

Multiphase flows are critical components of many physical systems; however, numerical models of multiphase flows with large parameter gradients can be challenging. Here, two different numerical methods, volume of fluid (VOF) and smoothed particle hydrodynamics (SPH), are used to model the buoyant rise of isolated gas bubbles through quiescent fluids for a range of Bond and Reynolds numbers. The VOF is an Eulerian grid-based method, whereas the SPH is Lagrangian and mesh free. Each method has unique strengths and weaknesses, and a comparison of the two approaches as applied to multiphase phenomena has not previously been performed. The VOF and SPH simulations are compared, verified, and validated. Results using two-dimensional VOF and SPH simulations are similar to each other and are able to reproduce numerical benchmarks and experimental results for sufficiently large Morton and Reynolds numbers. It is also shown that at low Reynolds numbers, the two methods, SPH and VOF, diverge in the transient regime of the bubble rise. Regimes that require simulations capable of representing three-dimensional drag are identified as well as regimes in which results from VOF and SPH diverge. KEYWORDS bubble dynamics, buoyant systems, multiphase flows, rising bubble dynamics, smoothed particle hydrodynamics (SPH), volume of fluid (VOF) Re = vL ,

Vapor Bubble Deformation and Collapse near Free Surface

“…Nguyen et al [21] used a geometrical VOF algorithm based on the piecewiselinear interface calculation (PLIC) to numerically investigate the dynamic behavior of bubble collapses, water jets, and pressure loads during the collapse of the bubble near walls and a free surface; the results showed a good agreement between the simulation and experiment of the bubble dynamics during the collapse process. Erin et al [22] used the SPH and VOF methods to simulate the rising of bubbles, and compared with previous experimental results, they concluded that both the VOF and SPH methods may be used to capture physically realistic transient and steady-state multi-phase systems; the SPH method could better capture the centroid of the bubble, while the VOF method better captured the rising velocity of the bubble.…”

“…SPH is a meshless method. It is uniquely capable of representing the dynamic evolution of complicated geometries without additional algorithmic complication, such as those found in multi-phase flows [22]. When simulating fluid dynamics problems, the SPH method discrete the flow field into moving fluid micro clusters, which can be regarded as a combination of a series of molecules with the same properties [23].…”

Vacuum Filling Simulation with Combined Lagranian and VOF Method

“…The algebraic VOF method solves the volume fraction rate transport equation directly, without involving any geometric object. Existing researches show that the VOF method can depict complex interface structure and changes, and can be applied to the solution of two-phase flow [12] . Gim et al [13] presented an improved VOF model that based on smoothing functions, which effectively reduced the issue of spurious velocities.…”