A polydisperse model for bubbly two-phase flow around a surface ship

A two-fluid model suitable for the calculation of the two-phase flow field around a naval surface ship is presented. This model couples the Reynolds-averaged Navier–Stokes (RANS) equations with equations for the evolution of the gas-phase momentum, volume fraction and bubble number density, thereby allowing the multidimensional calculation of the two-phase flow for monodisperse variable size bubbles. The bubble field modifies the liquid solution through changes in the liquid mass and momentum conservation equations. The model is applied to the case of the scavenging of wind-induced sea-background bubbles by an unpropelled US Navy frigate under non-zero Froude number boundary conditions at the free surface. This is an important test case, because it can be simulated experimentally with a model-scale ship in a towing tank. A significant modification of the background bubble field is predicted in the wake of the ship, where bubble depletion occurs along with a reduction in the bubble size due to dissolution. This effect is due to lateral phase distribution phenomena and the generation of an upwelling plume in the near wake that brings smaller bubbles up to the surface. © 1998 John Wiley & Sons, Ltd.

The interaction of background ocean air bubbles with a surface ship

A center-averaged two-fluid model for wall-bounded bubbly flows

Plunging liquid jets are commonly encountered in nature and are widely used in indus-trial applications (e.g., in waterfalls, waste-water treatment, the oxygenation of chemicalliquids, etc.). Despite numerous experimental studies that have been devoted to this inter-esting problem, there have been very few two-phase ﬂow simulations. The main difﬁcultyis the lack of a quantitative subgrid model for the air entrainment process, which plays acritical role in this problem. In this paper, we present in detail a computational multi-phase ﬂuid dynamics (CMFD)-based approach for analyzing this problem. The mainingredients of this approach are a comprehensive subgrid air entrainment model thatpredicts both the rate and location of the air entrainment and a two-ﬂuid transport model,in which bubbles of different sizes are modeled as a continuum ﬂuid. Using this approach,a Reynolds-averaged Navier Stokes (RaNS) two-way coupled two-phase ﬂow simulationof a plunging liquid jet with a diameter of 24mm and a liquid jet velocity around 3.5m/swas performed. We have analyzed the simulated void fraction and bubble count rate pro-ﬁles at three different depths beneath the average free surface and compared them withexperimental data in literature. We observed good agreement with data at all locations.In addition, some interesting phenomena on the different movements of bubbles with dif-ferent sizes were observed and discussed. [DOI: 10.1115/1.4007335]

A Two-Way Coupled Polydispersed Two-Fluid Model for the Simulation of Air Entrainment Beneath a Plunging Liquid Jet

During reentry and hypersonic igh t of space vehicles through atmosphere real gas eects come into play. The analysis of such hypersonic o ws is critical for proper aerothermal design of these vehicles. The present work emphasises numerical simulation of hypersonic o w with chemical non-equilibrium. A Reynolds Averaged Navier-Stokes code has been developed for this purpose employing an improved Roe scheme which is very robust and does not require any entropy x. To the best knowledge of the authors, such a formulation for real gas o w has not been reported earlier. A circular cylinder test case for which experimental data is available has been used to validate the code. Nomenclature _ !s mass rate of production of the species s s molar concentration of species s coecien t of thermal conductivity s thermal conductivity of the species s i

An Improved Roe Scheme for Real Gas Flows

An explicit finite volume TVD (MUSCL) formulation of the Roe's Approximate Riemann Solver is presented for the solution of three-dimensional Euler and Navier-Stokes equations. It is shown to provide accurate solutions of 3D inviscid and viscous high speed flows past blunt body configurations of practical interest.

Computation of three dimensional supersonic and hypersonic blunt body flows using high resolution TVD schemes based on Roe's Approximate Riemann Solver

S. K. Saxena

Papers

Computation of three dimensional supersonic and hypersonic blunt body flows using high resolution TVD schemes based on Roe's Approximate Riemann Solver