جستجوی مقالات مرتبط با کلیدواژه "sph" در نشریات گروه "علوم پایه"

Mixing and homogenization of cement paste are some of the most used phenomena in the construction and building industries. In most cases, a homogeneous mixture of cement paste is required and this is supplied by rotary mixers. In the present study, the rotary cement paste mixers in two-dimensional (2D) conditions are investigated by an Incompressible Smoothed Particle Hydrodynamics (ISPH) method. The method is validated and then used to model the cement paste mixer. The cement paste is considered a Bingham fluid. Two types of mixers are examined; shear mixer and blender. An appropriate mixing index that was previously applied to the discrete element method was successfully implemented for the ISPH method, and the performance of these two types of mixers is analyzed with this mixing index. The results show that the Reynolds number has a key role in the mixing in the shear mixers. In the low Reynolds numbers, an unmixed region is formed, which decreases with increasing Reynolds numbers. In blender mixers, the mixing rate is expected to increase with the multiplicity of vortices formed. But the coordinated motion of the vortices with the blades causes a fluid mass to move. Also, the resistance of the fluid to the moving components of the mixer is calculated and the difference in the performance of the two mixers in terms of energy consumption and mixing speed is compared and discussed.

Sloshing describes liquids motion in the semi-filled tanks, and exerts dynamic loading on its walls. This effect is of great importance in a number of dynamic systems e.g. aerospace vehicles, road tankers, liquefied natural gas carriers, elevated water towers and petroleum cylindrical tanks. Pressures insert impacts which are important for structural strength evaluation and its correct assessment is challenging for designers because of high share of nonlinear effects, complicated changes of free surface, strong impact phenomenon and air trapping effects. Since, numerical capabilities of the Smoothed Particle Hydrodynamics (SPH) method allow proper simulation of the fluid and/or the free surface we used it to investigate the behavior of a water tank exposed to a harmonic excitation. Besides, a Finite Volume (FV) analysis was employed using FLOW3D software, for the further comparison of the results from the SPH method. To assess the results, temporal variations of the impact pressure at the specific height of the tank wall is compared against the results from the experiment and also, the Finite Difference (FD) method. The comparison showed strong correlation of SPH results with the experimental ones. But, FLOW3D is not sufficiently capable of estimating the trend of pressure time history especially near the extremes.

Fluid mixing is a crucial and challenging process for microfluidic systems, which are widely used in biochemical processes. Because of their fast performance, active micromixers that use stirrer blades are considered for biological applications. In the present study, by using a robust and convenient Incompressible Smoothed Particle Hydrodynamics (ISPH) method, miscible mixing within a two-blade micromixer is investigated. The problem discussed herein is represented by an active micromixer comprising two stir-bars that rotate to mix the fluids. Because of its Lagrangian nature, Smoothed Particle Hydrodynamics is an appropriate and convenient method for simulating moving boundary problems and tracking the particles in the mixing process. Previous investigations have been carried out for mixing flow for a low Schmidt number. However, a low Schmidt number is barely applicable for liquid mixing. Hence, in the present study, the Schmidt number is considered to be Sc=1000. The present results show that the two-blade micro-channel mixer considerably improves the mixing rate in comparison with the one-blade micro-channel mixer.