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In this paper, an asymmetric breakup of non-Newtonian droplet (with power law behavior) in a new geometry (network junction) has been investigated. The geometry can break an initial droplet into six unequal size droplets. The research method is numerical simulation with Volume of Fluid (VOF) algorithm. The numerical results are compared with the results of a benchmark problem and a very good agreement is seen. The results showed that in areas close to the wall, mixing of materials of inside droplet is performed better, which is important in industrial applications of droplet based flows, especially in pharmaceutical and chemical industries. The results showed that the maximum vorticity magnitude in the K1 branch (the lowest output branch in the system) is 26, 44 and 28 % more than the maximum vorticity magnitude of the branches of K2, K3 and K4 (K4 is the highest output branch is in system). Also, maximum effective viscosity in the K1 branch is 27, 29 and 24 % less than the maximum effective viscosity in the K2, K3 and K4 branches, respectively. Therefore, K1 branch has the best performance in mixing of the material of inside droplet among the output branches. It was also revealed that the pressure of inside of droplet (both before and after breakup) is constant along the channel width [ABSTRACT FROM AUTHOR]

In the present paper, a new penalization method is proposed for implementation of the rigid surfaces on the Navier-Stokes equations in the vorticity-stream function formulation. In this method, a rigid body is considered as a region in the fluid flow, where the time is stopped. Therefore, by stopping the fluid particles, this region plays the role of a rigid body. In this regard, a new transformation is introduced and applied to the governing equations and a set of modified equations are obtained. Then, in the modified equations, the time dilation of the solid region is approached to infinity, while the time dilation of the fluid region remains unit. In the article, the physical and mathematical properties of modified equations are investigated and satisfaction of the no-slip and no-penetration conditions are justified. Then, a suitable numerical algorithm is presented for solving the modified equations. In the proposed algorithm, the modified vorticity equation is time integrated via the Crank–Nicolson method, and the spatial discretization is performed with the second-order finite differencing on a uniform Cartesian grid. The method is applied to the fluid flow around a square obstacle placed in a channel, the sudden flow perpendicular to a thin flat plate, and the flow around a circular cylinder. The results show that the no-slip and no-penetration conditions are satisfied accurately, while the flow fields are also solenoidal high level of accuracy. [ABSTRACT FROM AUTHOR]

Experimental investigation of two-phase air-water flow was conducted at consecutive inclinations of a large bend (with three equal slopes in respect to each other) and including the horizontal sections of the inlet and outlet of the bend. The results show that the elongated bubble regime flows without any effect of duct inclination change and consistent for all three zones of horizontal sections of before and after the bend and the bend itself. It was also noticed, as the duct inclination decreases along the route, vortex misty flow transmits to misty annular flow at higher gas flow rates. The annular flow regime was noticed only at the first slop of the bend. Slug flow was observed at the horizontal sections upstream and downstream of the bend. The slug flow at the upstream generated by the interfacial instabilities but at the downstream formed by Taylor bubbles. Slug flow area in the flow diagram increases as liquid flow rate increase at both horizontal sections. In addition, the void fraction change rate with phases mass flow rate was considered at the duct inlet. [ABSTRACT FROM AUTHOR]