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This paper explores the impact of viscosity ratio and surface wettability on immiscible viscous fingering instability within a rectangular channel. Numerical investigations are conducted across a range of viscosity ratios (VR) from 0.0009 to 0.5 and wall wettability ($\theta$) from 15° to 150°. The volume of fluid (VOF) model is employed to track the development of finger-shaped instability at the fluid interface. Our results indicate that higher viscosity ratios lead to increased displacement efficiency. Additionally, we find the formation of necking at low VR, which diminishes at higher VR values. The finger-shaped pattern splits into two parts at a wettability of 15°; beyond this threshold, no such splitting occurs. Furthermore, a transition from hydrophilic to superhydrophobic wettability abolishes necking, resulting in enhanced displacement efficiency. Notably, as wettability shifts from hydrophilic to super hydrophobic, instability shifts toward the left side. These findings hold relevance for applications in drug delivery, clinical processes and oil recovery.

This paper reports the splitting morphology of low-viscous fingers in the microchannels that are associated with flat T-shaped, curved T-shaped, and Y-shaped junctions. The numerical simulations are based on the finite volume approach and the volume of the fluid model. In this study, microchannels are filled with silicon oil. Perfluorodecalin is used to displace silicon oil from the microchannels. Due to viscosity differences, the low-viscous finger (LVF)-shaped instability evolves at the interface of fluids. A single LVF propagates in the parent channel, and at the junction, it splits into two identical LVFs. It is noted that the splitting morphology of LVF depends upon the shape of the junction and its wettability. Therefore, there are three different junctions, i.e. flat T-shaped, curved T-shaped, and Y-shaped, with three different wettability conditions $(\theta )$, i.e. hydrophilic ($60^{\circ }$), hydrophobic ($120^{\circ }$), and superhydrophobic ($150^{\circ }$) are used for numerical investigation. It is found that a LVF splits symmetrically at all three different junctions but tips of LVFs are found to be convex in superhydrophobic conditions. The LVFs-shaped are curved in the limbs of curved T-shaped microchannel and straight in the limbs of flat T-shaped and Y-shaped microchannels. The findings of this paper may be used in lung biomechanics, respiratory diseases, biochemical testing, and many more.

A three-dimensional numerical simulation of time-averaged wave-induced currents was performed, its results were compared with the results of a depth-integrated Boussinesq equation model And the differences were discussed in terms of wave height, instantaneous and mean free surface elevations, mean and time-averaged velocity fields, and turbulence parameters. For the three-dimensional simulation, an internal wave generation and a wave-absorbing sponge layer scheme, which can eliminate the influence of waves reflected from the wave source and wall boundaries toward the domain, were applied to the RANS equation model in a CFD code named FLUENT and the VOF model was utilized for the water surface In this study, two experiments involving wave-induced flows were simulated. First, to examine the wave-induced flows computed by the present model, we performed an existing two-dimensional experiment in which time-averaged mean motions induced by wave breaking were measured on a constant slope. Second, the breaking monochromatic wave case of Vincent and Briggs' experiments [Vincent and Briggs, 1989] was simulated in three dimensions using the present model. The experimental case presented a three-dimensional phenomenon in which a wave-induced jet-like current was generated and influenced the wave transformation over an elliptical submerged shoal. The computations agreed with the measurements and showed vertical distributions of the wave-induced currents over the shoal.

In the 2011 Tohoku Earthquake, many structures were destroyed by the tsunami whose magnitudes were much larger than the design level. Tsunami defense structures in coastal areas will need reinforcement in the future, and for that reason it is important to evaluate tsunami behavior and resulting tsunami force. This study analyzes tsunami transformation around a Haramachi thermal power station which suffered serious damage by the tsunami due to the 2011 Tohoku Earthquake and which has complex topography and building layout. A three-dimensional (3D) tsunami simulation is carried out for a surrounding region of the Haramachi thermal power station using boundary conditions of the water surface elevation and flow velocity obtained from a two-dimensional (2D) tsunami simulation by a nonlinear shallow water model. Using these boundary conditions, the computer fluid dynamic model FLUENT is employed to simulate the tsunami behavior around the Haramachi thermal power station. The validity of the predictions is examined by comparison with actual traces of tsunami inundation depths (I.D.).