Papers by Keyword: Axial Velocity

Abstract: In this paper, the flow of a shear thinning nanofluid in a mechanically stirred tank has been numerically analyzed. This tank is cylindrical with a flat bottom. It is filled with Al₂O₃ nanoparticles suspended in the base fluid and equipped with an anchor-type stirrer whose shape is tilted upwards at an angle α. The purpose of this research is to study the impact of the tilt angle (0≤α≤π/6) and the effect of the alumina nanoparticles concentration (0≤φ≤0.1) on the hydrodynamic behavior and energy consumption. In the new anchor design (α>0), the fluid volume that is swept during the rotation of the anchor is the same as that in the case of a standard anchor (α=0). The laminar flow of the nanofluid is governed by the continuity and momentum equations taking into account the physical properties of the nanofluid introduced through correlations cited in the literature. The results obtained have shown that the tilt angle significantly contributes to the reduction of the power number, and leads to a decrease in the intensity of the tangential flow at the level of the extreme transverse planes of the tank. However, this reduction in intensity is compensated by increasing the axial flow. The use of nanoparticles in this work aims to show the role of the new design of anchor in creating a vortex at the bottom of the tank and to avoid of particles sedimentation.

Abstract: Dynamic of particles in annular fluid flow is a very relevant subject for many industrial applications, especially for the oil and gas industry. Successful drilling is, to a large extent, dependent upon the ability of the drilling fluid to clean the hole by conveying the cuttings to the surface. The aim of this work was to evaluate experimentally and through numerical simulations, the helical path and the axial mean velocity developed by glass beads with diameter of 2.7 mm flowing with a non-Newtonian fluid through a partially obstructed annulus. Experimental data are reported for flow of 1 m³/h of an aqueous solution with 0.5% Xanthan gum through concentric annulus with partial obstruction of 6 mm and a 183 rpm rotation of the inner cylinder. Techniques of computational fluid dynamics (CFD) were applied to obtain detailed information about the flow field, allowing to estimate the radial position of launching of particles in the range of 35.5 mm to 39.1 mm. Comparisons between numerical calculations and the flow data indicated, in general, a very good agreement.

Abstract: This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, S_N of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U₀ is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, R_e to evaluate the differences of S_N. The significance of center recirculation zone investigation affected by differences R_e also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U₀. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all S_N after x/D = 0.3 plane towards the outlet of a burner.

Abstract: In order to study the lower critical point in transitional area of pipe, we used the method of direct numerical simulation to simulate fluid flow and contrasted it with experiment. The result showed that the flow state is close to laminar. Along the pipe axis, the change of pressure is not obviously. The changing rate of axial velocity U near wall region was significantly greater than in the mainstream area, it proved the important role of viscous force.

Abstract: Previous wind tunnel study has found that the lift slope of a common research model with flying-wing configuration in a transonic freestream can experience a sudden drop as the angle of attack is increased. A numerical investigation of aerodynamic characteristics of the flying-wing configuration in transonic speed flow is presented with the intend to examine the changes of the flow characteristics in detail. As can been seen from the analysis, at sufficiently high angles of attack the dominant feature of flows over the leeside of the configuration is a pair of counter-rotating vortices. Solving the steady Reynolds-Averaged Navier-Stokes equations , the flow structures were exhibited in different angles and the analysis of total pressure, static pressure and axial velocity through wing vortex cores were presented in order to analyze the flow characteristics for the develop of the vortex. The investigation shows that the numerical method is accurate enough to capture the features of the flow especially the formation and breakdown of the leading-edge vortices. The rapid expansion of the vortex core and adverse pressure gradient the flow encounters in the chordwise direction affect the aerodynamic performance severely.

Abstract: Nozzle spacing is an important factor influencing the effect of high-pressure water jet cleaning. When the nozzle incidence angle, the deflection angle and the target distance are determined, the size of the nozzle spacing determines the overlap of the water jet, the overlap is too large or too small will reduce the cleaning effect. In this paper ,using CFD software to simulate the flow field inside and outside of the high-pressure water jet nozzle, analysis the jet axial velocity, pressure distribution, and discussed this changes in the case of different spacing between the nozzles when the nozzle structure are same, and choose an reasonable spacing to ensure the cleaning effect.

Abstract: This paper presents computational fluid dynamics (CFD) studies to characterize air velocity distribution for various bed configurations in a swirling fluidized bed (SFB). Unlike conventional fluidized beds, a SFB provides radial mixing which is desirable is fluidization. Three velocities components were observed, the tangential velocity, radial velocity and axial velocity. These velocities were created as a result of using annular blade type distributor which mimics the turbine blades. In actual industrial applications, the axial velocity will create fluidization while the tangential velocity provides swirling effect. The presence of radial velocity can be explained as a consequence of centrifugal force generated by the swirling gas. Understanding these velocity distributions will enable optimization of the annular blade distributor design towards a high efficient fluidized bed system.

Abstract: At present, the research ways of stratified air-conditioning technology mainly have two types, experimental study and numerical simulation. In this paper, a transparent Plexiglas model was designed, of which the size was supposed to be 1/50 of the real scale. PIV technology was innovatively applied into the experiment to measure the air distribution of an industrial plant. Different air supply velocities and different kinds of air supply outlets were taken into account to discuss the influence of them. Results revealed that as the jet velocity increased gradually, the airflow’s stratification effect became more evident. When the aspect ratio changed from 1:2 to 1:8, the diffusion degree in vertical direction increased obviously. In comparison with the rectangular air supply outlet, the circular one had lower decay, longer jet distance and better contractibility. The experimental findings are useful for optimizing the design of air distribution in high ceiling industrial plant.

Abstract: The purpose of this study is to examine the validity of groove in enhancing performance of splicing fiber in air splicer. A groove is usually used to improve the condition of internal flow, reduce the internal pressure and so on. In this paper, a two-parameter numerical mathematic model was developed and calculated in two configurations (chamber with groove and chamber without groove). The strength of the fibers was measured which were got from the air splicer with two different configuration. The result of simulation and experimental shows that: with the increase of inlet pressure, the rotational velocity and axial velocity of air flow also increase for the without groove case. As a counterpart, the axial velocity can be significantly reduced while rotational velocity keeps constantly for the groove case.

Abstract: Circulating Fluidization Bed (CFB) for Flue Gas Desulfurization (FGD) is widely used. But its desulfurization efficiency is lower than Wet FGD. Its investment is not much lower than Wet FGD. Flow field of CFB for FGD is hard to be uniform. Swirl Composite Fluidization Mode (SCFM) was brought forward compared to Venturi Fluidization Mode (VFM). Experiment and simulation under cold condition was proceeded. From the test, flow field along axis and in cross-sections for SCFM are uniform. Turbulent velocity fluctuation is violent. And particles concentration is high. SCFM has better flow effect than VFM. Uniformity increases with higher superficial velocity and more tangential swirl devices. Recommended tangential swirl devices number is between 3-6. SCFM technology has good foreground.