Numerical Simulation Of Flow Patterns Research Articles

Numerical simulation of flow pattern at a divergent pier in a bend with different relative curvature radii using ansys fluent

In this work, the three-dimensional flow around piers in river meanders under rigid bed conditions was modeled. The software ANSYS FLUENT was used to perform the simulation. The study was carried out in a 180° curve accompanied by cylindrical piers with a diameter of 5 cm and a slope angle of 21° under rigid bed conditions. The results of the comparisons showed that this model can help simulate the flow pattern around inclined bridge piers in bended channels with acceptable accuracy. To analyze the flow pattern, the work was followed by studying the effect of the parameters that affect the physics of the problem: the relative radius of curvature of the curve, the location of the piers within the 180° curve, and the arrangement of the piers relative to the flow direction. The results showed that increasing the relative radius of curvature as well as the range of the bend reduced the tangential velocity values; the minimum tangential velocity value occurred at a relative radius of curvature of 5. With the pier group installed in the direction of flow, the maximum secondary flow power occurred at the 60° position at about 18.8%, while with the pier group installed across the flow, the maximum secondary flow power occurred at the 120° position at 14.2%. A comparison of the vorticity at the perpendicular and downstream positions showed that the vorticity values at the 60° and 120° positions were greater than the corresponding values at the 90° position in both cases.

Numerical simulation of flow pattern for non-Newtonian flow in agitated thin film evaporator

Agitated thin film evaporator (ATFE) is a new type of high-efficiency evaporator where a film is forced to form through a rotating scraper and the high-viscosity non-Newtonian flow materials can be evaporated smoothly. The flow distribution and transmission mechanism of the material in the evaporator directly determine the evaporation efficiency and power consumption of the evaporator. Unlike previous study that was based mainly on Newtonian flow, this paper establishes a three-dimensional computational fluid dynamics model of ATFE for non-Newtonian flow with different viscosities, and systematically probes the flow field distribution characteristics and film forming mechanism in the evaporator. The results show that the flow field distribution characteristics of low-viscosity non-Newtonian flow are similar to those of Newtonian flow, the material can form a uniform and continuous liquid film on the wall; as the viscosity increases, the uniformity and continuity of the liquid film gradually deteriorate. Through studying the flow field distribution and transmission form of the materials, and combining the liquid film distribution, velocity distribution, shear strain rate distribution, and viscosity distribution, it is found that the shear field and viscosity distribution formed by the internal structure and operating state of the evaporator are the key to the good film formation. In addition, it is proposed that the bending of the leading edge of the scraper can assist the spreading of high viscous fluid liquid film, and the best bending angle is explored. This research provides theoretical guidance and basis for the design and application of ATFE.

Numerical Simulation of Flow Pattern in Series of Impermeable Groynes in Fixed Bed

This paper presents a numerical simulation of recirculating flow patterns in groyne fields. Moreover, it entails the concept determination of proper spacing of vertical unsubmerged and impermeable groynesin seriesto control the bank erosion. Flow pattern between the groynes varies along their space. The flow in groyne field may significantly affect the flow change, bed change, bank erosion and condition of habitat. In this regard, an assessment of flow along the space of groynes will yield important data needed to diversify the object of groyne installation. So, knowledge about determination of the proper spacing of groynes in groyne field is important. Space of vertical groynes was set from 1.5 to 10 times the length of groynes. The velocity field between groynes was simulated by using Computational Fluid Dynamics (CFD) model Nays 2D. Simulated velocity field was compared with existing experimentaldata for the same parameter, which agreed satisfactorily. Based on simulated results,the optimal spacing of vertical groynes to control the bank erosion was recommended.

Numerical simulations of flow patterns in the human left ventricle model with a novel dynamic mesh morphing approach based on radial basis function

We present a new numerical simulation framework for prediction of flow patterns in the human left ventricle model. In this study, a radial basis function (RBF) mesh morphing method is developed and applied within the finite-volume computational fluid dynamics (CFD) approach. The numerical simulations are designed to closely mimic details of recent tomographic particle image velocimetry (TomoPIV) experiments. The numerically simulated dynamic motions of the left ventricle and tri-leaflet biological mitral valve are emulated through the RBF morphing method. The arbitrary Lagrangian-Eulerian (ALE) based CFD is performed with the RBF-defined deforming wall boundaries. The results obtained show a good agreement with experiments, confirming the reliability and accuracy of the developed simulation framework.

Numerical simulation of flow pattern for non-Newtonian flow in agitated thin film evaporator

刮膜蒸发器是通过旋转刮板强制成膜，可实现高粘度非牛顿流体类物料平稳蒸发的新型高效蒸发器。蒸发器内流体的流动、分布与传输机制直接决定了蒸发器的蒸发效率与功耗。不同于现有研究主要基于牛顿流体开展，本文针对不同粘度的非牛顿流体，建立蒸发器三维计算流体动力学模型，系统研究了蒸发器内的流场分布特性和成膜机理。结果表明：低粘非牛顿流体的流场分布特性和牛顿流体类似，物料可在壁面形成均匀且连续的液膜；随着粘度的增加，液膜的均匀性和连续性逐渐变差。通过对流场分布与传输形式的研究，结合液膜分布、速度分布、剪应变率分布，以及粘度分布进行对比分析发现，蒸发器内部结构与运行状态形成的剪切场与粘度分布是蒸发器良好成膜的关键。此外，提出对刮板前缘进行弯折可辅助高粘流体液膜铺展，并对最佳弯折角度进行探索。本研究为刮膜蒸发器的设计和应用提供了理论指导与依据。

A meshless solution of a of lid-driven cavity containing a heterogeneous porous medium

The main objective of the present paper is to define and evaluate a benchmark test for solving the Navier-Stokes equations in heterogeneous porous medium. The benchmark is of high relevance for proper numerical simulation of flow pattern in the liquid-solid phase-change related phenomena. The test case represents a lid-driven square cavity which consists of a solid, a liquid, and a mushy part. Three different variations of the problem are solved, in which the ratio between the liquid and the mushy part is modified. The Reynolds and the Darcy number of this case are equal to 400 and 2.5×10−10, respectively. The Navier-Stokes equation, with an additional source term to take into account the Darcy effect, is solved with the local meshless diffuse approximate method. The method is structured by using the second-order polynomial basis vector and the Gaussian function to evaluate the weighted least squares approximation. The explicit Euler scheme is used to perform the time discretisation. The non-incremental pressure correction scheme is used to couple the pressure and velocity fields. Results are presented in terms of stream function, velocity magnitude, and mid-plane velocity profiles in the steady state. The accuracy of the numerical method is evaluated by a comparison with the finite volume solution obtained with a commercial solver and an investigation of the node arrangement effect.

Numerical simulation of flow patterns and the effect on heat flux during R32 condensation in microtube

Based on the fluid volume approach, a transient numerical model for the condensation heat transfer and flow features in a microchannel is proposed. The flow condensation of R32 in a circular microtube with 0.1 mm diameter was studied. Four typical flow patterns, annular, injection flow, slug flow and bubbly flow are simulated along a two-dimension calculational domain successively. The numerical mode is verified by the experiments from the literature. The numerical results discern that the increase of mass flux, wall temperature and saturation temperature affect the detachment point of vapor slug further toward the outlet with higher occurrence frequency, which can be attributed to the higher Weber number and Capillary number of tail vapor core respectively. The local heat flux and wall shear stress will decrease along the flow direction overall, and tend to be constant in the single phase liquid area. However, there exit some rebounds and oscillations of the local heat flux and wall shear stress during injection and slug flow. The transient oscillations of wall shear stress can induce fluctuations and even waves in the annular flow upstream, which can be concluded as “surface tension force affecting upstream”, is proposed based on the minimum potential energy theory. This mechanism could be a supplement for the traditional theory of “flow pattern transition at high mass flux being induced by fluctuations which grow up while flowing downstream”.

Numerical Simulations of Flow Patterns and Possible Implications for Deposition around Circular Patches of Vegetation

ABSTRACT Kim, H. S.; Choi, J., and Park, M., 2016. Numerical simulations of flow patterns and possible implications for deposition around circular patches of vegetation. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1367 - 1371. Coconut Creek (Florida), ISSN 0749-0208. This study presents flow patterns and possible deposition around circular patches of vegetation using a two-dimensional numerical model. Because flow can pass through the patch, the formation of the von-Karman vortex street is delayed and its position moves further downstream as solid volume fraction (SVF) increases. The vortex downstream of the patch is formed as SVF≥0.08. When the two patches are very close to each other, a single vortex street is formed. As the distance between two patches is large, the effect of the interaction is weak and the vortex is developed behind indivi...

Numerical modeling of flow pattern in dam spillway’s guide wall. Case study: Balaroud dam, Iran

Flow pattern recognition using the physical modeling and numerical simulation helps designers to propose optimal shape for hydraulics structures. Optimal shape of hydraulic structure causes increasing their performance. In this study, the effect of geometries of guide walls on the flow pattern and rating curve of Balaroud dam spillway’s (Iran) was simulated using numerical and physical simulation. Numerical simulation of flow pattern through the guide walls was carried out using Flow 3D software as computational fluid dynamic (CFD) tool. To this task, three plans for the guide walls were evaluated. The results showed that the plan (3) has best performance for removing cross waves and smoothly passing the flow through the approach channel and over the spillway. Evaluating the turbulence models showed that the RNG-K-epsilon becomes the best performance to show the cross waves.

Numerical simulation of flow patterns in the forebay and suction sump of Tianshan pumping station

Tianshan Pumping Station takes water from the Yellow River. A three-dimensional (3D) mathematical model of turbulence flow patterns in the forebay and suction sump was developed and a 3D turbulent flow simulation technique applied to numerical calculation of the flow pattern characteristics in both the original and rebuilt forebays of the pumping station. The numerical simulation results were analyzed and contrasted. The results showed that, with technical improvement, surface backflow was avoided, and bottom velocity in the forebay was increased while bottom velocity in the suction sump was unchanged. Because of this, there was no sediment deposition in the bottom of the forebay, and flow velocities in the forebay and suction sump were more evenly distributed.

A Numerical Study of Flow Field in a Hydrocyclone for Potash Ore Desliming

Despite the widespread use of hydrocyclone in the process of potash ore desliming, its accurate design is often difficult because the feed composition is complicated and the viscosity is high in the brine system. In this study, a numerical approach based on computational fluid dynamics (CFD) was performed to describe the flow field. The numerical simulation of flow pattern in hydrocyclones for potash ore desliming was presented. Some basic information concerning the velocity and pressure distribution is given, and the results can be used as the fundamental basis for its design.

Oscillatory instability and fluid patterns in low-Prandtl-number Rayleigh-Bénard convection with uniform rotation

We present the results of direct numerical simulations of flow patterns in a low-Prandtl-number (Pr = 0.1) fluid above the onset of oscillatory convection in a Rayleigh-Bénard system rotating uniformly about a vertical axis. Simulations were carried out in a periodic box with thermally conducting and stress-free top and bottom surfaces. We considered a rectangular box (Lx × Ly × 1) and a wide range of Taylor numbers (750 ⩽ Ta ⩽ 5000) for the purpose. The horizontal aspect ratio η = Ly/Lx of the box was varied from 0.5 to 10. The primary instability appeared in the form of two-dimensional standing waves for shorter boxes (0.5 ⩽ η < 1 and 1 < η < 2). The flow patterns observed in boxes with η = 1 and η = 2 were different from those with η < 1 and 1 < η < 2. We observed a competition between two sets of mutually perpendicular rolls at the primary instability in a square cell (η = 1) for Ta < 2700, but observed a set of parallel rolls in the form of standing waves for Ta ⩾ 2700. The three-dimensional convection was temporally quasiperiodic for 750 ⩽ Ta ⩽ 1114, chaotic for 1115 ⩽ Ta < 1125, and quasiperiodic once again for 1125 ⩽ Ta < 2700. The three-dimensional quasiperiodic flow bifurcated into a two-dimensional periodic flow for Ta ⩾ 2700. The convection at the primary instability were three-dimensional and quasiperiodic in time for all values of Ta (⩽3000) in a box with η = 2. Küppers-Lortz type of convection was observed at the primary instability in longer boxes (4 ⩽ η ⩽ 10). The convective structures consisted of the appearance and disappearance of straight rolls, rhombic patterns, and wavy rolls inclined at an angle \documentclass[12pt]{minimal}\begin{document}$\phi = \frac{\pi }{2} - \arctan {(\eta ^{-1})}$\end{document}ϕ=π2−arctan(η−1) with the straight rolls. We also present a low-dimensional model constructed for a square box (η = 1).

Numerical simulation of flow pattern with sill in the front inflow forebay of pumping station

There are recirculation zones and vortexes in the forebay of pumping stations which effect the flow pattern and reduce the efficiency of the pump.The incompressible N-S equations are solved by the finite volume method. The Realizable k-ε turbulence model and the SIMPLE algorithm for pressure-velocity coupling are used. The flow pattern of bottom sills with different positions is calculated. Large recirculation zones and the serious bias flow occur on the both sides in the forebay when there is nothing in the forebay, as well as, flow conditions of sideway pump stations is also bad due to mainstream compression .There is a large recirculation zone and serious bias flow when the bottom sill is too far from the sumps. On the other hand, the flow pattern of sump is badly affected when it is too close to the sumps. The flow pattern is improved when the bottom sill is installed in the right position.There is optimized location where the flow will be pumped uniformly into the sump. The results indicate that the calculation results show a good agreement with the test results. The research results can be applied in the similar forward diffuse forebay of pumping stations.

Lubrication properties of Nitinol 60 alloy used as high-speed rolling bearing and numerical simulation of flow pattern of oil-air lubrication

The friction and wear tests were performed using Nitinol 60 alloy pin sliding over GCr15 steel disk in a pin-on-disk tribometer system under PAO oil lubrication conditions. It was found that Nitinol 60 alloy can be lubricated well and has shown remarkable tribological performance. Average coefficient of friction (COF) of Nitinol 60 is 0.6 under dry friction; however, average COF decreases to 0.1 under PAO oil lubrication. SEM image of the worn surface shows that Nitinol 60 exhibits excellent wear resistance and the wear mechanism is mainly adhesive wear. Flow pattern of oil-air flow in oil pipe was simulated by FLUENT software with VOF model for acquiring working performance of oil-air lubrication. The optimum velocity of oil and air at the inlet was achieved, which provides the great proposal for the design of experiment of oil-air lubrication of Nitinol 60 alloy. The simulation results showed that the optimum annular flow of flow pattern was obtained when air velocity is 10 m/s and oil velocity is 0.05 m/s. The formation mechanism of annular flow was also discussed in the present study.

NUMERICAL SIMULATION OF BACKWATER AT BRIDGE PIERS (TECHNICAL NOTE)

Flow pattern around bridge pier and its effects is one of the interest of hydraulic engineers. Since numerical models are progressing as a tool to analyses flow fields, in this paper numerical simulation of flow pattern around bridge pier is studied and its consequent effects on backwater is investigated. Fluent model (version 6) is used and water surface is simulated using volume of fraction (VOF) method. Comparison of numerical and experimental results show good agreement.

Numerical Simulation of Flow Pattern and Liquid-solid Flow in Sudden Pipe Expansion

In order to analyse the diffusion features of solid particles in sudden pipe expansion, the turbulence flow field inside sudden pipe expansion was simulated with some Reynolds Time-average Models and Large Eddy Simulation (LES). The results showed that simulation with LES could respond the vortex dissipation and the flow instability better than the others. And the solid particle diffusion in sudden pipe expansion was simulated with LES and Discrete Phase Models(DPM). The results showed that the diffusance of particles decreased as the number of P St increased, the bigger particles remained their original flow track more and influenced less by coherent vortex and turbulence discrete vortex of the flow field, and the flow field had stronger capability of carrying particles with small diameter of particles.

Modeling of Agglomerate Dispersion in Single Screw Extruders

Abstract A model for solid agglomerate dispersion in single screw extruders is proposed. The model combines numerical simulations of flow patterns in the metering section of a single screw extruder with a Monte Carlo method of clusters rupture and erosion mediated by a local fragmentation number. Particle size distributions and Shannon entropy are used for mixing characterization. The model is quite general and can be adapted for different polymer-additive systems as well as for different processing equipment.

An arbitrary Lagrangian–Eulerian formulation for the numerical simulation of flow patterns generated by the hydromedusa Aequorea victoria

A new geometrically conservative arbitrary Lagrangian–Eulerian (ALE) formulation is presented for the moving boundary problems in the swirl-free cylindrical coordinates. The governing equations are multiplied with the radial distance and integrated over arbitrary moving Lagrangian–Eulerian quadrilateral elements. Therefore, the continuity and the geometric conservation equations take very simple form similar to those of the Cartesian coordinates. The continuity equation is satisfied exactly within each element and a special attention is given to satisfy the geometric conservation law (GCL) at the discrete level. The equation of motion of a deforming body is solved in addition to the Navier–Stokes equations in a fully-coupled form. The mesh deformation is achieved by solving the linear elasticity equation at each time level while avoiding remeshing in order to enhance numerical robustness. The resulting algebraic linear systems are solved using an ILU(k) preconditioned GMRES method provided by the PETSc library. The present ALE method is validated for the steady and oscillatory flow around a sphere in a cylindrical tube and applied to the investigation of the flow patterns around a free-swimming hydromedusa Aequorea victoria (crystal jellyfish). The calculations for the hydromedusa indicate the shed of the opposite signed vortex rings very close to each other and the formation of large induced velocities along the line of interaction while the ring vortices moving away from the hydromedusa. In addition, the propulsion efficiency of the free-swimming hydromedusa is computed and its value is compared with values from the literature for several other species.

Performance of Kenics static mixer over a wide range of Reynolds number

Abstract The present study deals with the numerical simulation of flow patterns and mixing behaviour in Kenics static mixer over a wide range of Reynolds number. Three different sets of Kenics mixer (aspect ratio = 1.5) comprised of 3, 9 and 25 elements each have been characterized. The Reynolds number was varied in the range of 1 to 25,000 (i.e., from laminar to turbulent flow regime). The numerical approach takes into account the aspects of the fluid flow at higher Reynolds number values including circumferential velocity profiles at different cross-sections within the Kenics mixer, which were neglected in previous studies. It was observed that cross-sectional mixing in the turbulent flow regime takes place up to 30% of each element length at element-to-element transition; beyond that velocity profiles were uniform. The experiments were also carried out to measure the circumferential and axial velocity profiles and pressure drop in three different Kenics Mixers using air as fluid. The pressure drop per unit element (Δ P / η ) was found to be independent of the number of Kenics mixing elements used in the system. The total pressure drop across Kenics mixer obtained by CFD simulations were compared with the experimental pressure drop values and correlations available in the literature. The numerical results were found in good agreement with the experimental as well as the results reported in the literature. A new pressure drop correlation in the Kenics static mixer has been developed.

Numerical Simulation of Flow Patterns in Cyclones of Different Cone Dimensions

AbstractThis paper presents the numerical simulation of the flow patterns within three cyclones of different cone dimensions. The simulation was performed with commercial CFD package FLUENT V5.5. The accuracy of the simulation was tested by comparison with the available experimental data. Simulation results show that the cone dimension significantly influences the flow pattern within cyclones. The comparison of the flow patterns within the cyclones of different cone dimensions explained well the different separation behavior of these cyclones. The results suggest that the CFD simulation is capable of predicting changes in flow patterns resulting from cyclone configuration modification.