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Effect of boundary layer and its local separation on lift and drag coefficients, especially in the analysis of hydrodynamic behavior of hydrofoils is considered as an interesting subject for fluid mechanics researchers. Boundary layer control methods to increase the lift coefficient and reduce the drag coefficient, are very common. Aerodynamic study of flows at low Reynolds to special applications such as micro unmanned underwater vehicles, underwater robots and explorers are interested. For this reason in this study, the effect of fluid blowing and suction through upper surface of hydrofoils on flow control, lift and drag coefficients for flow under Re =500 and Re=2000 are investigated. Jameson’s finite volume method and power-law preconditioning method for analyzing viscous incompressible flows are presented. To control the boundary layer a jet with a width of 2.5% of chord length is placed on hydrofoil’s upper surface and results for different blowing (suction) parameters are introduced. Results show that, blowing far from leading edge at low blowing angel and perpendicular suction far from leading edge increase the lift coefficient. Also blowing with law velocity ratio and suction with large velocity ratio, has the better impact on increasing lift coefficient.

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In this paper, the immersed boundary-lattice Boltzmann method has been employed to simulate non-Newtonian flow around curve boundaries. The pressure base lattice Boltzmann equations have been used to solve the Eulerian domain to estimate proper pressure gradient in the Poiseuille flow. In addition Immersed boundary method (IBM) utilizes a discrete set of force density is also used to represent the effect of boundary on flow domain. In addition to simulate the real physical dominate problem and study the right effects of non-Newtonian fluid properties, scaling parameters have been introduced to notice the relationship between physical and lattice variables. At First, the capability of present method is examined for simulating the power-law fluid flow around a confined circular cylinder and the results show good agreement with previous study. In the following, the power-law fluid flow around elliptical cylinder in a channel is investigated for three aspect ratios eta=1,1.5,2 and for 5

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Numerical analysis and simulation of cavitating flows due to appearance and its application in the maritime industry, water turbomachinery, hydrofoils, underwater vehicles, etc. have specific importance. For this reason in this research, the effect of blowing on hydrodynamic behavior of cavitating flows over hydrofoils has been investigated. Jameson's finite volume method and power-law preconditioning method with single-phase cavitation model (Barotropic model) have been used to the analyzing of cavitating flow. The stabilization of solution has been achieved with help of the second and fourth-order dissipation term. Explicit four step Runge-Kutta method has been used to achieve the steady state condition. As regards the cavitation often occurs at high Reynolds number, to facilitate the simulation the inviscid flow equations are considered. For apply the blowing from hydrofoil surface, a jet has been placed on hydrofoil’s upper surface. The parameters of jet location, blowing velocity ratio, blowing angle and width of jet are investigated and simulation has been performed for two different cavitation numbers. The numerical results show that the power-law precondition increases the convergence speed significantly. Blowing reduces the cavity length, lift and pressure drag coefficients compared to no blowing case. Also the increase of blowing velocity ratio, blowing angle and width of jet, decrease the cavity length, lift and pressure drag coefficients.

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Aerodynamic study of flows at low Reynolds for special applications such as micro unmanned underwater vehicles, underwater robots and explorers are interested. In this paper, an improved progressive preconditioning method named power-law preconditioning method, for analyzing unsteady laminar flows around hydrofoils is presented. In this method, the 2D Navier-Stokes equations modifies by altering the time derivative terms of the governing equations. The preconditioning matrix is adapted from the velocity flow-field by a power-law relation. The governing equation is integrated with a numerical resolution derived from the cell-centered Jameson’s finite volume algorithm and a dual-time implicit procedure is applied for solution of unsteady flows. The stabilization is achieved via the second- and fourth-order artificial dissipation scheme. Explicit four-step Runge–Kutta time integration is applied to achieve the steady-state condition. The computations are presented for unsteady laminar flows around NACA0012 hydrofoil at various angles of attack and Reynolds number. Results presented in the paper focus on the velocity profiles, lift and drag coefficient and effect of the power-law preconditioning method on convergence speed. The results show satisfactory agreement with numerical works of others and also indicate that using the power-law preconditioner improves the convergence rate and decreases the computational cost, significantly.

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In situations involving large zeta potential, the classical Poisson-Boltzmann theory of electrolytes breaks down and a modified Poisson-Boltzmann equation which takes into account the finite size of the ions must be utilized. In addition, most biofluids cannot be treated as Newtonian, therefore, simultaneous effects of finite size of the ions and non-Newtonian behavior of the fluid in combined electroosmotic and pressure driven flows have been examined in the present study. The Governing equations are solved by a finite-difference-based numerical procedure in a rectangular microchannel. The ion size is introduced into the modified Poisson-Boltzmann equation by the steric factor, which allows considering the ions as point charges or finite sizes. Considering the ionic finite size, generally enhances the velocity of the shear-thickening fluid, while reduces the velocity of shear-thinning fluid. The Cross sectional aspect ratio is also considered and it was found that the adverse pressure gradient greatly affects the velocity profile, when aspect ratio increases, while velocity profile is less sensitive to aspect ratio variations in favorable pressure gradients. Furthermore, friction coefficient of both shear thinning and thickening fluids increases with the increase in zeta potential for point charge model, which for finite size charges decreases. Cross sectional averaged velocity reduces under steric effects for shear thinning fluids at large zeta potentials, while it is slightly influenced by shear thickening fluids.

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Passive micro-mixers have simpler manufacturing in comparison with active micro-mixers and only require energy for flow pumping. In the present study, non-Newtonian fluids and non-Newtonian power-law fluid’s mixing behavior in passive micro-mixers have been studied. Simulation has been performed, using computational fluid dynamics commecrical code of Ansys fluent and two different approaches of two-component mixing have investigated. The first approach studies fluid’s mixing behavior by changing flow behavior index and flow consistency index in 5 different 3D geometries as multiple T-micromixer with aligned and non-aligned inputs in one and two plane, respectively, multiple T-micromixer, double T-micromixer, and T-micromixer, while the second approach studies mixing behavior by changing flow behavior index while flow consistency index is constant in two multiple 3D geometries with non-aligned inputs. In all studies, water was used as Newtonian fluid and carboxymethyl cellulose solution was used as non-Newtonian fluid. The studied range of Reynolds number was 1 to 100. In both approaches, the results for mixing index and pressure drop for power-law index according to criterion are reverse of each other; it means that in the first approach, with increasing power-law index, the mixing index increased and the pressure drop decreased and in second approach, this procedure is reversed. But, procedure of non-dimensional fully developed velocities in two approaches investigated is similar in comparison to geometries with non-aligned inputs.

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In this research, the deformation of a non-Newtonian leaky-dielectric droplet suspended in another non-Newtonian fluid under a uniform electric field is simulated. The aim of this research is the studying the effect of the electric field on the hydrodynamic of non-Newtonian droplets and also the comparison between the behavior of Newtonian and non-Newtonian droplets in the presence of an electric field. The power law model is used to describe non-Newtonian fluid behavior. The level set method is employed to determine the location of the interface. Also, the ghost fluid method is used to apply discontinuities at the interface. By applying an electric field, a non-Newtonian droplet deforms similarly to a Newtonian one. This deformation may occur either in the direction of the electric field or perpendicular to it. By increasing the electric Capillary number (ratio of electric force to surface tension force) the deformation of the non-Newtonian droplet with different power law constants increases. In this research, the behavior of different non-Newtonian droplets with different power constants was compared and it was observed that by an increase in the power law constant the drop deformation increases. According to the results, the deformation of a shear-thinning droplet under an electric field is less than the deformation of a Newtonian droplet and the deformation of a Newtonian droplet is less than the deformation of a shear thickening droplet.

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The effect of gum tragacanth (0, and 0.15%) and Fennel (Foeniculum vulgare) (0, 2.5, and 5%) on the chemical and rheological properties, phase separation, Lactic Acid Bacteria (LAB) viability, and sensory characteristics of an Iranian dairy drink "Doogh" was investigated during 20 days of storage. Results cleared the stability of Dooghs prepared with Gum Tragacanth Dispersions (GTD) was significantly higher than samples without this hydrocolloid (P< 0.05). Doogh samples’ viscosity in the presence of Fennel Extract Powder (FEP) was increased significantly (P< 0.05). Power-law and Herschel-Bulkley rheological models were appropriate models for describing the flow behavior of control and treated Doogh samples, respectively. The results showed that by increasing the amounts of FEP, LAB viability increased while the fungi population decreased significantly (P< 0.05). Therefore, this herbal powder could stimulate LAB growth and control the fungi population in treated samples. Finally, adding GTD to the Doogh sample was proper for improving stability, and enrichment with Fennel was suitable for increasing LAB viability and microbial spoilage control.