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In the present work, we investigate the dynamics of a bubble, rising inside a vertical sinusoidal wavy channel. We carry out a detailed numerical investigation using a dual grid level set method coupled with a finite volume based discretization of the Navier–Stokes equation. A detailed parametric investigation is carried out to identify the fate of the bubble as a function of Reynolds number, Bond number, and the amplitude of the channel wall and represented as a regime map. At a lower Reynolds number (high viscous force), we find negligible wobbling (path instability) in the dynamics of the bubble rise accompanied only with a change in shape of the bubble. However, at a higher Reynolds number, we observe an increase in the wobbling of the bubble due to the lowered viscous effects. Conversely, at a lower Bond number, we predict a stable rise of the bubble due to higher surface tension force. However, with a gradual increase in the Bond number, we predict a periodic oscillation which further tends to instigate the instability in the dynamics. With a further increase in the Bond number, a significant reduction in instability is found unlike a higher Reynolds number with only change in the shape of the bubble. At lower values of Reynolds numbers, Bond numbers, and channel wall amplitudes, the instability is discernible; however, with an increase in the channel wall amplitude, the bubble retains integrity due to higher surface tension force. At a higher Bond number and channel wall amplitude, a multiple breakup in the form of secondary bubbles is observed. We propose a correlation which manifests the average bubble rise velocity and the fluctuating velocity (due to channel waviness) as a function of Reynolds number, Bond number, and channel wall amplitude. Finally, we conclude that the bubble dynamics pertinent to the offset channels with varying amplitudes does not remain the same as that of the symmetric channel. [ABSTRACT FROM AUTHOR]

A coupled level-set and immersed-boundary-method (CLSIBM) is proposed for simulation of liquid and gas phase flow during filling of a complex geometry based mold using a modified cut-cell technique. The CLSIBM uses Cartesian computational domain, with two level-set functions: for liquid-metal and gas interface and ϕf,s for liquid-metal/gas and solid (mold box) interface. The cut-cell based immersed boundary method enable us to handle any internal two-phase flow in complex geometry using a Cartesian grid. Numerical results are presented for filling in four different tanks/molds, demonstrating the robustness of the proposed method during mold filling in complex geometry mold box. [ABSTRACT FROM AUTHOR]

Brief Background To study causes of failure of root canal treated teeth. Observations Root canal treatment can fail due to errors and/or mishaps at various stages in treatment, beginning with case selection, during treatment, post-treatment. The most frustrating on part of a clinician are those ocurring during treatment that predispose the root canal system to inadequate disinfection. The role of smear layer and biofilms during post-treatment disease is also acknowledged. Whatever be the cause, it is ultimately the apical percolation of fluids that leads to loss of seal. Summary and Conclusions All in all, it is worth noting that it is the knowledge, expertise and skill of the operator that is the one ultimate solutionto the problem of failed root canals. A systematic approach should be instituted in referral practice. Retreatment cases, syndromic patients, cases with abnormal/additional root and canal morphology should be lawfully referred to specialists so that highest level of care is given to best serve the patients who entrust us with their care. [ABSTRACT FROM AUTHOR]