Two-fluid modeling of bubbly flows around surface ships using a phenomenological subgrid air entrainment model

Ma, Jingsen; Oberai, Assad A.; Hyman, Mark; Drew, Donald A.; Lahey, R.T.

doi:10.1016/j.compfluid.2011.08.015

Cited by 31 publications

(18 citation statements)

References 18 publications

(37 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This model however, being a function of the liquid velocity, is frame dependent and predicts an unphysical entrainment of bubbles for traveling waves. Ma et al (2011b) propose a model in which the entrainment rate is proportional to the product of the turbulent kinetic energy and gradient of the normal velocity in the direction of the free surface normal. Thought the gradient seems to be a good indicator of entrainment locations, the model constant is highly problem dependent and must be adjusted on a per-case basis (Carrica et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

A mechanistic model of bubble entrainment in turbulent free surface flows

Castro

Carrica

2016

International Journal of Multiphase Flow

View full text Add to dashboard Cite

A framework for the development of models of bubble entrainment in free surface turbulent flows is presented. The framework uses mechanistic processes to model the stages involved in the entrainment of bubbles due to interaction of turbulence with a free surface. Entrainment is modeled as a chain of events for a bubble that is formed at the free surface, then pulled into the fluid against buoyancy, and interacts with vortices that break it up into smaller bubbles, or with other bubbles by coalescence. The main entrainment mechanism is modeled as a vortex/free surface interaction process that can entrain bubbles if the vortices located a given distance from the surface are strong enough. This approach overcomes limitations of approaches where the entrainment is determined only by turbulence parameters, which in the case of objects interacting with a free surface entrain bubbles on the boundary layers irrespective of the distance to the free surface. Depending on the computational fluid dynamics approach used to solve the flow, these processes may need different levels of modeling; more resolved approaches like large-eddy simulation with a volume of fluid method of the free surface will require less modeling complexity than a less resolved RANS method, since some of the involved processes of entrainment are directly accounted for. In this paper a standard RANS approach is used with the free surface modeled using a single-phase level set method, and models are presented for each of the relevant processes to produce a complete mechanistic model of turbulent bubble entrainment. The model was calibrated and tested for two relevant problems: a 2D+T breaking wave in model scale, and the full scale bubbly flows around the US Navy Research Vessel Athena. For the second case a grid study is carried out to analyze grid convergence performance of the model. Comparisons with experimental data show that the model predicts well location and magnitude of entrainment.

show abstract

Section: Introductionmentioning

confidence: 99%

A mechanistic model of bubble entrainment in turbulent free surface flows

Castro

Carrica

2016

International Journal of Multiphase Flow

View full text Add to dashboard Cite

show abstract

“…The influence of each bubble is spread using a Gaussian distribution conserving the total bubble volumes [17]. Equations (2) and (3) are solved using the Eulerian flow solver 3DYNAFS-VIS © [18]. The numerical scheme uses a finite volume formulation.…”

Section: Eulerian Continuum Model For Carrier Fluid Phasementioning

confidence: 99%

“…Bubbly flow problems have a wide spectrum of applications in marine hydrodynamics [e.g., [1][2][3][4][5][6]. Numerical modeling of this kind of problems, especially while involving cavitation, remains challenging due to its complex physics.…”

Section: Introductionmentioning

confidence: 99%

Modeling Separation and Cavitation Behind a Blunt Body

Hsiao

et al. 2016

Volume 1B, Symposia: Fluid Mechanics (Fundamental Issues and Perspectives; Industrial and Environmental Applications); Multipha

Self Cite

View full text Add to dashboard Cite

Cavitation flow behind a blunt body is modeled using a physics-based numerical model of cavitation initiation and transition to larger cavities. The calculations initiate from the dynamics of nuclei, then tracks the dispersed bubble phase with a two-phase viscous model. This solver includes a level set method to model coalescence of the nuclei into large cavities and to track the dynamics of the resulting free surfaces. A transition scheme enables collection of the bubbles into a large cavity and also enables breakup of a large cavity into a bubble cloud. Using this model, simulations are conducted for different flow velocities and corresponding cavitation regimes. When the velocity is relatively small (i.e., large cavitation number), flow separation behind the body results in the shedding of vortices, which capture nuclei in their cores to form elongated vortical cavities. As the flow velocity increases (or as the ambient pressure decreases) the flow evolves into a separated flow with a large cavity behind the body. A reentrant jet may form and move upstream into the cavity towards the body. This jet periodically shears off portions of the cavity volume, resulting in large amounts of bubble clouds. These results are in good qualitative agreements with experimental observations.

show abstract

“…Kiger and Duncan (2012) also reviewed the mechanisms of air entrainment by a plunging jet, and the application to plunging breakers, pointing out the insufficiencies of the model to obtain a global air-entrainment model for plunging breaking waves. These works brought a lot of knowledge on the bubble generation mechanisms and are used as references in the development of numerical models of air entrainment around surface ships in stationary flows (Carrica et al, 1999;Moraga et al, 2008;Ma et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Experimental study of bubble sweep-down in wave and current circulating tank: Part II—Bubble clouds characterization

et al. 2016

View full text Add to dashboard Cite

a b s t r a c tIn this second part, images acquired from the specific trials developed in order to study the phenomenon of bubble sweep-down are analysed. A post-processing method has been developed to analyse the two air entrainment mechanisms described in the first part, for several test configurations. Bubble clouds are described in terms of depth, area and velocity for both vortex shedding and breaking wave bubble clouds. A parametric study is also performed to calculate the influence of each test parameter on the frequency of bubble generation. It is demonstrated that the occurrence of bubble clouds is proportional to the wave height, with a considerable influence of the phase shift between waves and motions. The overall results provide new elements for the understanding and the study of the phenomenon, with the final objective of obtaining a reliable tool that facilitates the design of research vessels.

show abstract

Two-fluid modeling of bubbly flows around surface ships using a phenomenological subgrid air entrainment model

Cited by 31 publications

References 18 publications

A mechanistic model of bubble entrainment in turbulent free surface flows

A mechanistic model of bubble entrainment in turbulent free surface flows

Modeling Separation and Cavitation Behind a Blunt Body

Experimental study of bubble sweep-down in wave and current circulating tank: Part II—Bubble clouds characterization

Contact Info

Product

Resources

About