Papers by Keyword: Velocity Distribution

Abstract: Turbulent flow characteristics through a three-dimensional annular diffuser having a rectangular twisted hub RTH are investigated. The numerical analyses are performed to have more understanding of the physical behavior of the fluid flow. The numerical work is conducted using the RTH with three twist ratios (y/w = 0.6, 0.7, and 1) for a Reynolds number 128069. In the present study, the air is used as a working fluid. Computational Fluid Dynamics CFD, based on a finite volume method, is completed by utilizing the standard k-ε turbulence model. Velocity streamlines, velocity contours, and pressure contours plots are described to study the flow characteristics by utilizing different twist ratios (y\w). The analytical results reveal that RTH has a significant effect on the velocity and pressure characteristics. Findings show that the diffuser with the twist ratio (y\w = 0.6) produces more swirling and recirculation than (y\w = 0.7 and 1). Therefore, the RTH with a small twist ratio significantly enhances the distribution of the velocity and pressure because of the strong swirling generated through the flow.

Abstract: A process when different materials are combined to produce a product with multiple layers is called co-extrusion. During this process, polymers are melted in separate machines and then extrudate from different die channels. Once these channels converge, the polymers meet and flow through a single channel. The surface where the two fluids face is called “interface”. It is crucial to maintain the interface's uniformity and stability in order to achieve the desired multi-layered structure. Most of the issues in co-extrusion are related to issues that can be classified into two categories such as polymer encapsulation/interfacial distortion and die swell. To solve these problems, designers focus on improving the interface's stability. This paper examines effects of cross-section modification of the two-channel feedblock on the interface location and velocity and pressure distributions of the flow. The ANSYS software was used to simulate the co-extrusion of polymers, LLDPE and HDPE, in two-channel feedblock with rectangular, circular, and straight slot cross-sections. The results show that sharp corners increase the thickness of dead zones, while rounding them decreases the thickness. Additionally, stadium-shaped (or straight-slot) cross-section channels can move the flow with a higher maximum velocity and thinner boundary layer combining the results of rectangular and circular feedblocks.

Abstract: In this paper, a double-side grinding method with variable position rotation is proposed, which changes the motion mode of the workpiece in the fixed distance rotation grinding from the grinding principle, and realizes the irregular planar motion of the workpiece in the isolation dics at the same time as the rotation. That is, the movement trajectory of the workpiece rotation center relative to the grinding tool is the curve of the change. Different grinding principles fundamentally overcome some defects of traditional planar grinding methods. A prototype model of variable position rotation grinding is established, and the feasibility of the new method is verified by simulation experiments. The simulation data also further proves the time-varying nature of this grinding method in improving the grinding trajectory, the uniformity of relative velocity distribution of grinding and the superiority and diversity of the mechanical wear of the grinding mechanism and the ability to adjust the grinding trajectory.

Abstract: A bar drawing process of an aluminium alloy in semisolid state is presented in the work. The drawing process depends on various parameters such as temperature, die-angle, shear rate etc., accordingly a study is considered. The work involves development of a model to investigate the drawing process of A356 alloy in semisolid range. The rheology of the alloy in semisolid state shows a distinct behaviour and reduces energy requirement during the drawing process. In the context, a model suitably represents the rheology of the alloy is considered to perform a study of the process in details. An analytical and a numerical solutions are combined together to solve the governing equations. Finally, in the work, the distribution of velocity, viscosity variation and drawing power of the semisolid alloy under shear are predicted in the domain. It is found that the energy requirement is reasonably less in case of semisolid bar drawing process compare to a conventional bar drawing process. Finally, the drawing power required to deform a conventional solid A356 alloy is compared with that of the semisolid A356 alloy.

Abstract: In case of metal sheet forming of alloys in semisolid state, modelling of the process is very essential to predict flow behaviour, temperature distribution of the alloy etc. towards improvement of the product quality and to reduce manufacturing costs. Accordingly, the present work develops a model to predict the behaviour during metal sheet forming of an Al-alloy (A356) in semisolid state. The semisolid alloy passes through a rectangular channel having small depth and larger width. The alloy in semisolid state is cooled from the top at a controlled rate. In the model, the respective flow field is represented by the momentum conservation equation. The non-Newtonian behaviour of the semisolid slurry is incorporated considering the Herschel–Bulkley model. The agglomeration and de-agglomeration phenomena of the suspended particles under shear are represented using a time dependent structural parameter. The temperature field is predicted considering the transient energy conservation equation, and hence the fraction of solid is continuously updated. The solution considers an apparent viscosity of the semisolid alloy as a function of structural parameter, shear stress and shear rate. The governing equations are finally solved by finite difference method. The work predicts velocity, temperature and liquid fraction distribution of the semisolid slurry.

Abstract: In order to explore the velocity attenuation law and model of φ6mm tungsten ball fragment, theory analysis combined with tests is employed to study its velocity experimental results. First of all, a fragment velocity measuring system including 12 groups of cutting device is established. Then the attenuation experiments of φ6mm tungsten ball fragment in high speed and low speed velocity are performed by the measuring system. Based on the least-square method, MATLAB software is adopted to analysis the experimental data and obtained the high speed and low speed velocity attenuation models. The results show that φ6mm tungsten ball fragment speed attenuation coefficient is consistent in high speed and low. Thus, the analysis on velocity experimental results verifies that the established model is reasonable.

Abstract: In order to get the situation of transitional flow in tube, we tested the fluid field by PIV experiment and acquired the velocity distribution of the flow field at different Reynolds number (Re=2400 and Re=3000). At the same time the structure and characteristics of the flow field were obtained. The experimental result shows that the change of axial velocity in boundary layer is not obvious at low Reynolds number, the fluctuation of axial velocity appears and normal speed changes a little in mainstream area. With the increase of Reynolds number the axial velocity both in boundary layer and mainstream area change obviously, pulsation of the normal speed increases, the state of fluid flow gradually evolves from laminar to transitional flow.

Abstract: Models with main-branch channel, crossing channel and net type channel are established and nutrient liquid with a velocity of 0.01m/s is adopted in the study to investigate the fluid field in the channel by using FEA software FLUENT. The velocity and pressure distribution have been obtained in the investigation. By comparing the results in the three models, pressure and velocity distribution in the second and the third models are relatively uniform and are appropriate for the bionics principles. Studies in this paper will be of benefits for the development of tissue engineering.

Abstract: Based on computer simulation, a new measurement pipe design with locally shrunk cross section is proposed for electromagnetic flow transducer. The efficiency of the magnetic field excitation circuit is effectively enhanced. The sensitivity of the transducer is increased. The transducer design is adopted in a battery powered electromagnetic flow meter prototype to reduce the power consumption. The prototype was tested. The feasibility of the proposed design was proved.

Abstract: Two factors have been selected to investigate the effects of environmental condition variations on pressure drop of draw resistance standard rods and a series of numerical simulations have been carried out. The results indicate that the pressure drop of draw resistance standard rod significantly increase with the rise of the ambient pressure but slightly decrease with the augment of environmental humidity. To compare with the effect of the pressure, the influence of humidity on the pressure drop is rather weak, which could be neglected during the actual measurement.