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The fluid flow and oil-water separation were simulated using a Reynolds stress transport equation model of turbulence in water flow and a stochastic model of oil droplet motion,Simulation results give the axial and tangential velocity components,the pressure and turbulence intensity distribution and droplet trajectories for a hydrocyclone of F type and a hydrocyclone proposed by the present authors.The flow filed predictions are in qualitative agreement with the LDV measurements.The results show that the proposed hydrocyclone has better performance than the hydrocyclone of F type due to creating stronger centrifugal force and lower axial velocity. 相似文献
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基于分相流模型的气液两相流流量测量 总被引:1,自引:1,他引:0
从伯努利方程出发,基于分相流模型,推导出气液两相流流过文丘里管的流量公式.在分析了两相流通过节流装置的实际流动情况后,作者认为气液两相滑移比是影响流量公式误差的一个重要因素.在理论与实验研究的基础上,作者提出了气液两相流流过文丘里管的滑移比经验关联式.利用作者提出的滑移比经验关联式和分相流模型的流量公式测量两相流流量,体积流量误差的均方根小于5.1%,表明该方法适用流过文丘里管的两相流流量测量,尤其对于两相流动激烈的两相相互作用区域,流量误差满足测量的要求. 相似文献
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The velocity profile is calculated for slow three-dimensional flow through a simple cubic array of spheres. The velocity is represented by stream-function expansions which directly satisfy the equation of continuity and the no-slip conditions. The problem is solved by a variational principle which gives a lower bound on the total flow rate. The computed bound is within 0·2 per cent of the experimental results of Martin et al.[6]. 相似文献
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R. C. Gupta 《Polymer-Plastics Technology and Engineering》2013,52(3):475-492
An integral solution for Herschel-Bulkley fluid flow development in a straight channel is presented. The analysis not only accounts for the loss of energy due to viscous dissipation in the boundary layer, but evaluates wall-shear stress as integrals involving axial velocity distribution, which is obtained by cross-sectional integration of the equation of momentum. Results are compared with other integral solutions for several values of Herschel-Bulkley number and flow behavior index. 相似文献
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在实验研究超疏水微通道流动特性的基础上,建立了超疏水微通道流动模型,并利用FLUENT软件选择了合适控制方程,进行了数值模拟。对滑移壁面与无滑移壁面速度分布进行了对比分析。模拟得到的滑移速度,无量纲压降与实验值吻合性较好,最大相对误差分不超过15%、20%。分析了无量纲压降随着Re减小的原因是由于滑移效应的减弱,滑移长度的模拟值与实验值吻合较好,相对误差不超过20%,根据流场分析得出滑移长度可以反映滑移效应的大小。 相似文献
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We investigate the liquid circulation velocity in the draft‐tube airlift reactor, with mechanical agitation in the internal column as a riser, at the impeller speed of up to 40 s–1. An influence of the gas flow rate and the stirrer speed on the riser and downcomer gas hold‐up difference and on the liquid circulation velocity is also investigated. The character of the liquid circulation velocity changes depends on the relation between the gas flow rate and the impeller speed. A monotonic increase of the liquid circulation velocity with an increase of the gas velocity is observed at the impeller speed of lower than 15 s–1. A distinct decrease of the liquid velocity is found at higher impeller speeds and at low gas velocities. The decrease is larger for higher impeller speeds. We observe the minimum on the curve of the liquid velocity dependence on the gas velocity followed by the monotonic increase of the liquid velocity with an increase of the gas flow velocity. The minimum of the liquid circulation velocity appears if the ratio of the gas flow number to the impeller speed is about 0.0006. The minima are shifted towards the higher gas velocities at higher impeller speeds. An experimental equation for the prediction of the liquid circulation velocity in the stirred airlift reactor is presented. 相似文献
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《分离科学与技术》2012,47(9-10):1007-1020
Abstract Fluid flow in forced flow electrophoresis has not been previously analyzed, even though it presents some interesting aspects. The effectiveness of this method for biological separations is due to a superimposition of an electric field on filtration. A mathematical model is presented, describing fluid flow and mass transfer for dilute solutions at electrical potentials less than the critical one. The calculated solute trajectories in a channel are determined by the ratio of the electrophoretic velocity to the withdrawal velocity through the permeable wall. The stationary layer and the layer in which all the solutes arrive at the permeable membrane at the end of the channel are also calculated. The concentration of the filtrate through the permeable membrane is obtained from the material balance of the solute entering the channel. Increased performance is obtained by means of a double-stage forced flow electrophoresis, where the ratio of final filtered solute concentration to inlet concentration is shown to be the square of the same ratio at the first stage. 相似文献
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Flow Mechanics on Extrusion through a Square-Entry Die 总被引:1,自引:0,他引:1
Jingmin Zheng William B. Carlson James S. Reed 《Journal of the American Ceramic Society》1992,75(11):3011-3016
The relationships between the constants of the Herschel-Bulkley (H-B) equation describing plastic flow and the Benbow equation for extrusion through a square-entry die were studied via computer simultions. These relationships are fundamental for characterizing the rheology of ceramic extrudates using the square-entry rheometer and are difficult to obtain from experiments. Results showed that the apparent shear rate should be used instead of extrudate velocity in the Benbow equation, and the Benbow equation was modified accordingly. The exponent in the H-B equation was exactly the same as the shear thinning exponent for the extrudate body in the modified Benbow equation. The die-entry velocity factor was a function not only of the shear rate factor but also of the shear thinning exponent in the H-B equation. The yield strength of the modified Benbow equation was zero when the yield strength in the H-B equation was zero. 相似文献
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This paper is concerned with an upward co-current flow of a gas-solid two-phase mixture through a packed bed, a system employed in a number of industrial processes. Experimental work was carried out by using glass balls for packed bed, and both glass beads and FCC as suspended particles. The effects of solids loading and gas velocity on the pressure drop as well as the static and dynamic solid hold-ups within packed bed were examined. Experimental results showed different behaviour of the FCC from glass beads. At a given gas velocity, pressure drop increased approximately linearly with solids loading with a slope for FCC much higher than that for glass beads. The static hold-up of glass beads was much lower than corresponding dynamic hold-up at a given gas velocity, and it did not seem to change much with solids loading under the conditions of this work. At a given gas velocity, the static hold-up of FCC, however, was found to be comparable with the corresponding dynamic hold-up. An analysis was conducted on the pressure drop using a modified version of the Ergun equation by taking into account the effects of suspended particles on the viscosity and density, as well as the gravitational force. It was found that the modified Ergun equation agreed well with the experimental results of both this work and those reported in the literature. Effort was also made to develop relationships for the dynamic hold-up and the interaction coefficient between the suspended and the packed particles, the so-called solid-phase friction factor in the literature. The dynamic hold-up was found to increase with an increase in the product of velocity ratio of the solid to gas phases and the square root of the diameter ratio of the suspended to packed particles, whereas the interaction coefficient increased in general with increasing Froude number but with significant scattering. 相似文献
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利用有限体积法(FVM)对双极坐标系下变系数二阶流体在内管做轴向往复运动的偏心环空中非定常流的控制方程进行了离散,其中时间积分方案采用全隐式,再利用交替方向隐式方法(ADIP)对离散方程组进行了数值求解;通过对视为变系数二阶流体的不同质量分数的聚丙烯酰胺(HPAM)水溶液在内管做轴向往复运动的偏心环空中的非定常流动实验,在相同条件下,在利用该方法数值求解上述控制方程后得到速度场的基础上,结合流量公式,将数值计算得到的流量与实测流量进行了比较,并将比较的吻合程度与其它方法得到的吻合程度进行了对比。结果表明:本文所给数值计算方法是正确的;利用本文方法数值计算得到的流量与实测流量的吻合程度比另外两种方法更好,且数值计算步骤较为简便、计算速度较快。 相似文献
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The effects of electrohydrodynamic (EHD) flow and turbulent diffusion on the collection efficiency of particles in a model ESP composed of the plates with a cavity were studied through numerical computation. Electric field and ion space charge density in the ESP were calculated by the Poisson equation of electric potential and the current continuity equation of ion space charge. The EHD flow field was solved by the continuity and momentum equations of gas phase, including the electrical body force induced by the movement of ions under the electric field. RNG k - l model was utilized to analyze turbulent flow. Particle concentration distribution was calculated from the convective diffusion equation of particle phase. As the ion space charge increased, the collection efficiency of charged particles increased because the electric potential increased over the entire domain in the ESP. The collection efficiency decreased as the EHD flow became stronger when the electrical migration velocity of charged particles was high. However, the collection efficiency could increase for the stronger EHD flow when the electrical migration velocity of charged particles was relatively lower. Also, the collection efficiency decreased as the turbulent diffusion of particles increased when the electrical migration velocity of particles was high. However, the collection efficiency could increase with the turbulent diffusion when the electrical migration velocity of particles was relatively lower. 相似文献
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The flow behavior of gas and ultrafine powder in a spouted bed was numerically investigated by using a two‐fluid model coupled with a population balance equation (PBE). The aggregation process is controlled by the PBE, which is solved by the direct quadrature method of moments. The agglomerate diameter is calculated according to the change in particle number. The solid pressure and viscosity were modified for agglomerates on the basis of the kinetic theory of granular flow. Distributions of diameter, solids volume fraction, and velocity are obtained by the new model. The influence of cohesive intensity and gas velocity on the diameter distribution were analyzed. The spout diameter, a vital parameter for the design of spouted beds, was calculated and a calculation formula is proposed. 相似文献
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The flow pattern of a fluidized bed with non-fluidized zones is investigated both experimentally and theoretically. Experiments were carried out in such a way that air was introduced only through part of the distributor. The results show a significant amount of air flowing to the zone where no air is introduced. However, once the gas velocity exceeds the minimum fluidization velocity in the zone where the air is introduced, the cross-flow hardly changes upon further increase of the gas velocity. A continuity equation and Ergun's equation are used to describe the flow pattern and pressure distribution over the bed. Very good agreement between the experimental and calculated results is achieved without any fitting parameter. The results are relevant to the understanding of heat transfer behaviour of a fluidized bed combustor (FBC) that is only partly fluidized to control its load. 相似文献
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The entrance region flow of a Casson fluid in a straight channel has been investigated numerically without making prior assumptions on the form of velocity profile within the boundary layer region, which is determined by a cross-sectional integration of the momentum differential equation for a given distance from the channel entrance. Using the macroscopic mass and momentum balance equations, the thickness of the core, the entrance length, the plug core velocity, and the pressure drop have been obtained at each cross section of the entrance region of the channel for specific values of Casson number. 相似文献
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N. B. Kirichenko 《Theoretical Foundations of Chemical Engineering》2004,38(4):341-348
By numerically integrating the inverse Laplace transform, an approximate solution was obtained to the convective diffusion equation for stationary two-dimensional mass transfer on a selectively permeable surface (membrane) past which there is a flow with linear flow velocity distribution at constant suction velocity. The solution was the concentration distributions in the pressure channel, which depend on two coordinates and the membrane selectivity. The adequacy of the assumptions made for reverse osmosis and pregel ultrafiltration in describing the laminar and turbulent flows in plane channels was demonstrated. 相似文献
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利用粒子图像测速测试平台研究了低速旋转盘腔轴向中截面的液体流动特性,并利用Realizable k-e模型对低速旋转盘腔内液体流场进行三维数值模拟,模拟结果与实验值吻合较好,最大相对误差为16.9%. 利用模型方程研究了导流板数、导流板相对长度、进口雷诺数和旋转雷诺数对盘腔内液体流动的影响. 结果表明,盘腔体积平均相对速度及涡量受进口雷诺数(Re)、导流板数、导流板相对长度影响较大,当进口Re从17000升至53000时,体积平均相对速度及涡量分别增加2.4倍和1.6倍;当导流板数由0提高至4时,体积平均相对速度及涡量增幅分别为62%和30%;当导流板相对长度由0.5提高至0.93时,体积平均相对速度及涡量增幅分别为114%和58%. 盘腔压损主要受进口Re的影响,当进口Re从17000升至53000时,盘腔压损增长8倍,而导流板数及导流板相对长度对压损的影响较小,增幅均小于5%. 为强化旋转盘腔内流体与壁面间传热,减小流体阻力,应优化进口Re、尽量增加导流板数和长度. 相似文献