Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 2, Influence of Abrupt Contraction)

Abstract

This paper computationally visualizes two phase flow patterns through a horizontally placed hydro philic or hydrophobic rectangular channel with an abrupt contraction. The rectangular duct used in this study has a thickness narrower than the Laplace constant so that the surface tension governs the fluid system rather than the inertia force. In particular, the computed bubble behavior at the abrupt contraction seemed to be a similar nature against the preliminary experimental result. Keywords I IntroductionTwophase flow in a channel is an intriguing issue to control flow systems in complicated piping geometries of nuclear energy plant and steelmaking plant, etc. To design such twophase flow systems, we need to investigate the influence of abrupt change of a duct area, i.e., abrupt expansion and contraction. The influence of the abrupt expansion has been investigated in the coupled study [1], and so the investigation on the abrupt contraction is required. In particular, a narrow thickness of the rectan gular duct affects the nature of the twophase flow, i.e., if the duct height (not a hydraulic diameter) would be smaller than the Laplace constantL G g σ r r − , the surface tension governs the fluid system rather than the inertia force. Here, r L and r G are the densities of liquid and gas, σ the surface tension and g the acceleration due to gravity. Similar to the associated study [1], the present setting of the duct thickness is 2 mm which is smaller than the calculated Laplace constant of about 2.7 mm in the present situation.As the preliminary step, this paper computationally visualizes twophase flow patterns through an abrupt contraction of a hydrophobic or hydrophilic rectangular duct with the narrow thickness. II Computational procedureThe FLUENT numerical code ver. 6.2.16, a commercially available CFD software package, was employed for all numerical predictions on Intel Core 2 Quad 2.66 GHz pro cessor with 3.25 GB RAM. GAMBIT 2.2.30 was employed for the establishment of the threedimensional computational grid. The detailed description about the actual setting of the FLUENT code is given in the associated study [1].The computational grids were made up of struc tured elements and a total of 100,320 cells were employed for a given flow domain in the millimeterscale rectan gular channel with the thickness of 2 mm (see Fig. 1). The

A Numerical study of Two-Phase flow through a Rectangular Duct with a Convergence Ribs

“…α ρ α ρ (8) The turbulent viscosity and kinetic energy of the mixture can be found by using Eqs. (9) and (10), respectively. ρ ϵ…”

“…Eskin and Deniz [8] The Eulerian approach was usedwith RMS turbulent model for twophase flow through sudden enlargement. It was observed that the deviation between the numerical values of void fraction and the pressure difference with the experimental values was increased with the increase of the void fraction.Ueda et al [9] used The volume of fluid VOF model, which includes the effect of wall adhesion and surface tension on flow, it was successfully predicted for the bubble flow pattern for low gas discharge and annular flow pattern for high gas discharge.Kumer [10] Performed numerically simulation for water oil two-phase stratified flow in the horizontal and inclined pipes by using volume of fraction (VOF) approach and RNG k-ε turbulence model. The angle of inclination had been ranged from ±50, 00, ±100 from the horizontal.…”