Abstract
The present work investigates the role of different treatments of the lower boundary condition on the numerical prediction of bubbly flows. Two different wall function formulations are tested against experimental data obtained for bubbly boundary layers: (i) a new analytical solution derived through asymptotic techniques and (ii) the previous formulation of Troshko and Hassan (IJHMT, 44, 871-875, 2001a). A modified k-e model is used to close the averaged Navier-Stokes equations together with the hypothesis that turbulence can be modelled by a linear superposition of bubble and shear induced eddy viscosities. The work shows, in particular, how four corrections must the implemented in the standard single-phase k-e model to account for the effects of bubbles. The numerical implementation of the near wall functions is made through a finite elements code.
Highlights
The significant advances experienced over the last forty years on turbulence modeling have meant that the prospect of achieving a three-dimensional representation of multiphase flows has evolved into procedures of practical application
To account for void fraction effects on flow solution, more realistic wall functions were proposed by Marié et al (1997) and Troshko and Hassan (2001b)
The present work revisits some of the previous analysis on bubbly boundary layers at low void fractions, proposing in its own term new local solutions for U, κ and ε
Summary
The significant advances experienced over the last forty years on turbulence modeling have meant that the prospect of achieving a three-dimensional representation of multiphase flows has evolved into procedures of practical application. The effect of the bubbles in the liquid phase in the immediate vicinity of the wall is to provoke an increase in the mean velocity gradient and in the turbulence intensity. To account for void fraction effects on flow solution, more realistic wall functions were proposed by Marié et al (1997) and Troshko and Hassan (2001b).
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