scholarly journals ANALYSIS OF THE NUMERICAL MODELLING OF TURBULENCE IN THE CONICAL REVERSE-FLOW CYCLONE

2010 ◽  
Vol 2 (5) ◽  
pp. 17-22
Author(s):  
Inga Jakštonienė ◽  
Petras Vaitiekūnas
Keyword(s):  
Fluid Flow ◽  
Numerical Modelling ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Cylindrical Part ◽  
Solid Particles ◽  
Good Prediction ◽  
Transfer Equations ◽  
Volume Method ◽  
Tangential Inlet

The paper describes the numerical modelling of the swirling fluid flow in the Stairmand cyclone (conical reverse-flow – CRF) with tangential inlet (equipment for separating solid particles from the gaseous fluid flow). A review of experimental and theoretical papers is conducted introducing three-dimen­sional differential equations for transfer processes. The numerical modelling of the Stairmand cyclone the height of which is 0.75 m, diameter – 0.17 m, the height of a cylindrical part – 0.290 m, a conical part – 0,39 m and an inlet area is 0,085×0,032 m is presented. When governing three-dimensional fluid flow, transfer equations Navje-Stokes and Reynolds are solved using the finite volume method in a body-fitted co-ordinate system using standard k– e and RNG k– e model of turbulence. Modelling is realised for inlet velocity 4.64, 9.0 and 14.8 m/s (flow rate was 0.0112, 0.0245 and 0.0388 m3/s). The results obtained from the numerical tests have demonstrated that the RNG k– e model of turbulence yields a reasonably good prediction for highly swirling flows in cyclones: the presented numerical results (tangential and radial velocity profiles) are compared with numerical and experimental data obtained by other authors. The mean relative error of ± 7,5% is found.

scholarly journals ANALYSIS OF NUMERICAL MODELLING OF TURBULENCE IN A CONICAL REVERSE‐FLOW CYCLONE

2010 ◽  
Vol 18 (4) ◽  
pp. 321-328 ◽  
Author(s):  
Petras Vaitiekūnas ◽  
Inga Jakštonienė
Keyword(s):  
Numerical Modelling ◽  
Swirling Flow ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Equation System ◽  
Reynolds Stress Model ◽  
Cylindrical Part ◽  
Solid Particles ◽  
System Modelling

This paper aims to analyse the problem of numerical modelling of the airflow in a conical reverse‐flow (CRF) cyclone with tangential inlet (equipment for separation of solid particles from gaseous fluid flow). A review of experimental and theoretical papers that describe cyclones with very complex swirling flow is performed. Three‐dimensional transport differential equations for incompressible turbulent flow inside a cyclone are solved numerically using finite volume‐based turbulence models, namely, the Standard k–ϵ model, the RNG k–ϵ model and the Reynolds stress model (RSM). The paper describes the numerical modelling of the airflow in the CRF cyclone, the height of which is 0.75 m, diameter ‐ 0.17 m, height of cylindrical part ‐ 0.255 m, height of conical part ‐ 0.425 m, inlet area is 0.085×0.032 m2. Mathematical model of airflow in a cyclone consisted of Navier‐Stokes (Reynolds) three‐dimensional differential equation system. Modelling results, obtained from the numerical tests when inlet velocity is 4.64, 9.0 and 14.8 m/s and flow rate is, respectively, 0.0112, 0.0245 and 0.0408 (0.0388) m3/s, have demonstrated a reasonable agreement with other authors’ experimental and theoretical results. The average relative error was ± 7.5%. Santrauka Nagrinejama duju aerodinamikos kūginiame grižtamojo srauto (KGS) ciklone (irenginys kietosioms dalelems atskirti iš oro srauto) su tangentiniu srauto itekejimu skaitinio modeliavimo problema. Trimates nespūdžiojo turbulentinio srauto ciklono viduje pernašos diferencialines lygtys skaitiškai sprestos baigtiniu tūriu metodu taikant standartini k–ϵ, RNG k–ϵ ir Reinoldso itempiu (RIM) turbulencijos modelius. Atliktas skaitinis oro srauto judejimo KGS ciklone modeliavimas. Ciklono aukštis – 0,75 m, skersmuo ‐ 0,17 m, cilindrines dalies aukšti ‐ 0,255 m, kūgines ‐ 0,425 m, itekejimo angos plotas 0,085×0,032 m2. Oro srauto judejimo ciklone matematinis modelis – Navje ir Stokso (Reinoldso) trimačiu diferencialiniu lygčiu sistema. Modeliavimo rezultatai, kai itekejimo greitis 4,64, 9,0 bei 14,8 m/s ir debitas – 0,0112, 0,0245 ir 0,0408 (0,0388) m3/s, neblogai sutapo su kitu autoriu eksperimentiniais rezultatais. Vidutine santykine paklaida ‐ ± 8 proc. Резюме Анализируется проблема аэродинамики газового потока в коническом возвратного потока (КВП) циклоне (оборудование для отделения твердых частиц от газового потока) с тангенциальной подачей газа. Произведен обзор экспериментальных и теоретических работ в циклонах такого типа, в которых образуется сложное вихревое течение потока. Для моделирования использованы трехмерные дифференциальные уравнения переноса, численно решаемые методом конечных объемов с использованием следующих моделей: стaндартной k–e, RNG k–e и рейнольдсовой модели турбулентности напряжений. Произведено численное моделирование движения потока воздуха в циклоне КВП, высота которого 0,75 м, диаметр – 0,17 м, высота цилиндрической части – 0,255 м, конической части – 0,425 м, площадь входного отверстия – 0,085×0,032 м 2 . Математическую модель движения потока воздуха в циклоне составила система трехмерных дифференциальных уравнений Навье-Стокса и Рейнольдса. Анализ результатов, произведенный при скоростях втекания в циклон 4,64, 9,0 и 14,8 м/с (дебит – 0,0112, 0,0245 и 0,0408 м 3 /c) и для модели рейнольдсовых напряжений, показал приемлемую согласованность с результатами других исследователей – со средней относительной погрешностью ± 7,5 проц.

STUDY OF GAS–SOLID FLOW IN A MULTICHANNEL CYCLONE / ORO IR KIETŲJŲ DALELIŲ SRAUTO DAUGIAKANALIAME CIKLONE TYRIMAS

2012 ◽  
Vol 20 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Pranas Baltrėnas ◽  
Petras Vaitiekūnas ◽  
Inga Jakštonienė
Keyword(s):  
Quartz Sand ◽  
Swirling Flow ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Cylindrical Part ◽  
Solid Particles ◽  
Numerical Tests ◽  
Tangential Inlet ◽  
Theoretical Results

This paper aims to analyse the problem of the gas–solid particle (SP) flow in the multichannel cyclone (three rings) with tangential inlet (KDG – equipment for separation of solid particles from gaseous fluid flow). It provides a review of experimental and theoretical papers that describe cyclones with a very complex swirling flow. The paper describes the experimental study and numerical modelling of the flow in the multichannel cyclone, the height of which is 0.72 m and the diameter – 0.50 m; with the height of the cylindrical part amounting to 0.29 m, the height of the conical part – 0.43 m, and the inlet area – 0.29×0.034 m2. The multi-functional measuring instrument Testo 400, intended for measuring the flow velocity in the inlet and outlet of the multichannel cyclone was used in experimental studies of the cyclone. Three-dimensional transport differential equations (Reynolds) for incompressible turbulent flow inside a cyclone are solved numerically using finite volume-based numerical method and turbulence models, namely the Standard k-ϵ model, the RNG k-ϵ model. According to results obtained during the experiments with quartz sand and quartz sand dust pollutants, the highest SP treatment efficiency as regards these pollutants, reaching 85.8-90.4%, was obtained. Modelling results obtained from the numerical tests with the inlet velocity of 6.27–10.78 m/s and, the flow rate of 0.111–0.190 m3/s have demonstrated a reasonable agreement with experimental and theoretical results. The average relative error was ± 4.3%. Santrauka Nagrinėjama dujų ir kietųjų dalelių aerodinamika daugiakanaliame (trijų žiedų) išcentriniame ciklone-filtre (keturkanalis dulkių gaudytuvas – KDG). Srauto įtekėjimas tangentinis. Apžvelgti eksperimentiniai ir teoriniai procesų tokiuose ciklonuose, kuriuose susidaro ypač sudėtingas sūkurinis srautas, tyrimo darbai. Atliktas eksperimentinis tyrimas ir skaitinis oro srauto judėjimo KDG ciklone modeliavimas (ciklonas 0,72 m aukščio ir 0,50 m skersmens, cilindrinės dalies aukštis −0,29 m, kūginės (dulkių rinktuvo) −0,43 m, įtekėjimo angos plotas −0,29×0,034 m2). Ciklono eksperimentiniams tyrimams naudota Testo 400 daugiafunkcis matuoklis, skirtas oro srauto greičiui matuoti daugiakanalio ciklono įtekėjimo ir ištekėjimo angose. Pateiktosios pernašos trimatės diferencialinės lygtys (Reinoldso) atvejo, kai turbulentinis srautas ciklono viduje nespūdusis, skaitiškai spręstos baigtinių tūrių metodu, taikant standartinį k-ϵ, ir RNG k-ϵ turbulencijos modelius. Remiantis tyrimų rezultatais, didžiausiasis ciklono su kvarcinio smėlio ir kvarcinio smėlio dulkių teršalais valymo efektyvumas siekė 85,8–90,4%. Modeliavimo rezultatai, kai įtekėjimo greitis 6,27–10,78 m/s ir debitas −0,111–0,190 m3/s, atitinkamai neblogai sutapo su eksperimentų duomenimis. Vidutinė santykinė paklaida siekė ±4,3 proc.

Thermohydrodynamic Behavior of a Slider Pocket Bearing

2005 ◽  
Vol 128 (2) ◽  
pp. 312-318 ◽  
Author(s):  
Mihai B. Dobrica ◽  
Michel Fillon
Keyword(s):  
Pressure Distribution ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Convective Boundary ◽  
Inertia Effects ◽  
Good Convergence ◽  
Bearing Design ◽  
The One ◽  
Volume Method ◽  
Generalized Reynolds Equation

Pocket-pads or steps are often used in journal bearing design, allowing improvement of the latter’s dynamic behavior. Similar “discontinuous” geometries are used in designing thrust bearing pads. A literature review shows that, to date, only isoviscous and adiabatic studies of such geometries have been performed. The present paper addresses this gap, proposing a complete thermohydrodynamic (THD) steady model, adapted to three-dimensional (3D) discontinuous geometries. The model is applied to the well-known geometry of a slider pocket bearing, operating with an incompressible viscous lubricant. A model based on the generalized Reynolds equation, with concentrated inertia effects, is used to determine the 2D pressure distribution. On this basis, a 3D field of velocities is constructed which, in turn, allows the resolution of the 3D energy equation. Using a variable-size grid improves the accuracy in the discontinuity region, allowing an evaluation of the magnitude of error induced by Reynolds assumptions. The equations are solved using the finite volume method. This ensures good convergence even when a significant reverse flow is present. Heat evacuation through the pad is taken into account by solving the Laplace equation with convective boundary conditions that are realistic. The runner’s temperature, assumed constant, is determined by imposing a zero value for the global heat flux balance. The constructed model gives the pressure distribution and velocity fields in the fluid, as well as the temperature distribution across the fluid and solid pad. Results show important transversal temperature gradients in the fluid, especially in the areas of minimal film thickness. This further justifies the use of a complete THD model such as the one employed.

scholarly journals The Effect Of Reynolds Number At Fluid Flow In Porous Media

REAKTOR ◽  
2017 ◽  
Vol 6 (2) ◽  
pp. 48
Author(s):  
L. Buchori ◽  
M. D. Supardan ◽  
Y. Bindar ◽  
D. Sasongko ◽  
IGBN Makertihartha
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Reynold Number ◽  
Packed Bed ◽  
Solid Particles ◽  
Flow In Porous Media ◽  
Viscous Term ◽  
Volume Method

In packed bed catalytic reactor, the fluid flow phenomena are very complicated because of the fluid and solid particles interaction to dissipate the energy. The governing equations need to be developed to the forms of specific models. Flows modeling of fluid flow in porous media with thw absence of the convection and viscous terms have been considerably developed such as Darcy, Brinkman, Forchheimer, Ergun, Liu, et.al and Liu and Masliyah models. These equations usually are called shear factor model. Shear factor is determined by the flow regime, porous media characteristics and fluid properties. It is true that these models are limited to condition whether the models can be applied. Analytical solution for the model types above is available only for simple one-dimentionalcases. For two or three-dimentional problem, numerical solution is the only solution. The present work is aimed to developed a two-dimentional numerical modeling flow in porous media by including the convective and viscous term. The momentum lost due  to flow and porous material interaction is modeled using the available Brinkman-Forchheimer and Liu and Masliyah equations. Numerical method to be used is finite volume method. This method is suitable for the characteristic of fluid flow in porous media which is averaged by a volume base. The effect of the solid and fluid interaction  in porous media is the basic principle of the flow model in porous media. The momentum and continuity  equations are solved for two-dimentional cylindrical coordinate. The result were validated with the experimental data . the result show a good agreement in their trend between Brinkman-Forchheimer equqtion with the Stephenson and Stewart (1986) and Liu and Masliyah equation with Kufner and Hoffman (1990) experimental data.Keywords : finite volume method, porous media, Reynold number, shear factor

Numerical modelling of three-dimensional fluid flow in a spiral compensator

2005 ◽  
Vol 37 (4) ◽  
pp. 267-292
Author(s):  
Wolfgang Schacht ◽  
Evgenii V Vorozhtsov ◽  
Anatoly F Voevodin
Keyword(s):  
Fluid Flow ◽  
Numerical Modelling ◽  
Three Dimensional

Fluid Flow and Heat Transfer in an Annulus With Ribs on the Rotating Inner Cylinder Surface

2020 ◽  
Vol 12 (4) ◽  
Author(s):  
S. Gokul ◽  
M. Deepu
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Thermal Performance ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Reynolds Numbers ◽  
Cylinder Surface ◽  
Turbulent Fluid Flow ◽  
Cylindrical Annulus ◽  
Volume Method

Abstract Numerical studies on heat transfer in Taylor-Couette-Poiseuille flow in a cylindrical annulus with ribs mounted on the rotating inner cylinder are presented. The present study focuses on two different types of ribs, namely, longitudinal ribs and helical ribs. Three-dimensional, steady, incompressible, turbulent fluid flow is solved using a semi-implicit method for pressure linked equations (SIMPLE) algorithm based finite volume method. The numerical solution method is validated using two sets of benchmark experimental data. Extensive numerical computations are carried out at various Reynolds numbers (2100 < Re < 2400) and modified Taylor numbers (30,000 < Tam < 90,000) for annulus with and without ribs. Ribs enhance the transport of heat and momentum by inducing more vorticity and turbulence in the flow. The overall performance is presented in terms of thermal performance factor (TPF), which takes in to account the heat transfer as well as pressure drop in the ribbed annulus. Helical ribs are found to offer superior thermal performance than its longitudinal counterpart.

scholarly journals CFD Simulation of Aeration and Mixing Processes in a Full-Scale Oxidation Ditch

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1633 ◽  
Author(s):  
Thomas Höhne ◽  
Tural Mamedov
Keyword(s):  
Fluid Flow ◽  
Cfd Simulation ◽  
Pure Water ◽  
Three Dimensional ◽  
Continuous Phase ◽  
Full Scale ◽  
Solid Particles ◽  
Mixing Processes ◽  
Treatment Processes ◽  
Sst Turbulence Model

This study aims to build a computational fluid dynamics (CFD) model that can be used to predict fluid flow pattern and to analyse the mixing process in a full-scale OD. CFD is a widely used numerical tool for analysing, modelling and simulating fluid flow patterns in wastewater treatment processes. In this study, a three-dimensional (3D) computational geometry was used, and the Eulerian-Eulerian multiphase flow model was built. Pure water was considered as the continuous phase, whereas air was modelled as the dispersed phase. The Shear Stress Transport (SST) turbulence model was specified which predicts turbulence eddies in free stream and wall-bounded region with high accuracy. The momentum source term approach and the transient rotor-stator approach were implemented for the modelling of the submersible agitators. The hydrodynamic analysis was successfully performed for four different scenarios. In order to prevent the incorrect positioning of the submerged agitators, thrust analysis was also done. The results show that the minimum required water velocity was reached to maintain the solid particles suspended in the liquid media and adequate mixing was determined.

scholarly journals Hybrid lattice Boltzmann and finite volume method for fluid flow and heat transfer simulations

2015 ◽  
Author(s):  
◽  
Zheng Li
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Methods ◽  
Hybrid Method ◽  
Three Dimensional ◽  
Multiscale Methods ◽  
Tracking Method ◽  
Flow And Heat Transfer ◽  
Interface Location ◽  
Volume Method

The fluid flow and heat transfer problems encountered in industry applications span into different scales and there are different numerical methods for different scales problems. Multiscale methods are needed to solve problems involving multiple scales. In this dissertation, multiscale methods are developed by combining various single scale numerical methods, including lattice Boltzmann method (LBM), finite volume method (FVM) and Monte Carlo method. Two strategies exist in combing these numerical methods. For the first one, the whole domain is divided into multiple subdomains and different domains use various numerical methods. Message passing among subdomains decides the accuracy of this type of multiscale numerical method. For the second one, various parameters are solved with different numerical methods. These two types of multiscale methods are both discussed in this dissertation. In Chapters 3 and 4, the whole domain is divided into two subdomains and they are solved with LBM and FVM respectively. This LBM-FVM hybrid method is verified with lid driven flows and natural convections. In Chapter 5, a LBM-FVM hybrid method is proposed to take both advantages of LBM and FVM: velocity field and temperature file are solved with LBM and FVM respectively. MCM has advantages in solving radiative heat transfer, and LBM-MCM hybrid method is proposed in Chapter 6. Numerical investigation for melting problems are carried on in this dissertation. The key point in solving the melting problem is how to obtain the interface location. To overcome the disadvantages in the now existing numerical methods, an interfacial tracking method is advanced to calculate the interface location. In Chapter 7, low Prandtl fluid natural convections are solved with LBM to discuss the oscillation results. Based on these results, low Prandtl number melting problems are solved using LBM with interfacial tracking method in Chapter 8. High Prandtl number melting problems in a discrete heated enclosure are solved using FVM with interfacial tracking method in Chapter 9. To take both advantages of LBM and FVM, melting problems are solved with LBM-FVM hybrid method in chapter 10, while interfacial tracking method is advanced by porous media assumptions in fluid flow field simulation process. Problems in Chapters 3-10 are all in two-dimensional and three-dimensional problems are more general than them in the realistic applications. Double LBM-MRT model for three-dimensional fluid flow and heat transfer is proposed and three types of natural convections in a cubic cavity are discussed in Chapter 11. For the first two types of cubic natural convections, the present results agreed very well with the benchmark solutions or experimental results in the literature. The results from the third type exhibited more general three-dimensional characters. Three-dimensional melting problems are solved with the proposed double LBM-MRT model with interfacial tracking method in Chapter 12. Numerical results in three conduction melting problems agree with the analytical results well. Taking Chapter 11 results in consideration, the double LBM-MRT model with interfacial tracking method is valid to solve three-dimensional conduction or convection controlled melting problems. Two convection melting problems in a cubic cavity are also solved. With a lower Rayleigh number, the convection effects are weaker; side wall effects are smaller; melting process carries on slower.

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