The Structure of Turbulence in a Moving Bed as a Function of Flow and Medium Properties

2014 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Control Volume ◽  
Mechanical Energy ◽  
Simple Algorithm ◽  
Darcy Number ◽  
Control Volume Method ◽  
Governing Equations ◽  
Bed Porosity ◽  
Volume Method

This article presents simulations for turbulent flows in a moving permeable bed making use of a macroscopic turbulence model. Intra-pore turbulence is considered by means of a two-equation closure. Governing equations for mean and turbulent flows are volume-averaged. The resulting set of transport equations is discretized using the control-volume method and the obtained algebraic equation set is relaxed via the SIMPLE algorithm. Results indicate that for larger values of Reynolds number, a greater amount of available mechanical energy is converted into turbulence. Simulations further indicate that for lower values of Darcy number and bed porosity, higher levels of turbulence kinetic energy are calculated.

scholarly journals A Framework and Numerical Solution of the Drying Process in Porous Media by Using a Continuous Model

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Hong Thai Vu ◽  
Evangelos Tsotsas
Keyword(s):  
Porous Media ◽  
Control Volume ◽  
Continuous Model ◽  
Control Volume Method ◽  
Drying Process ◽  
Transport Parameters ◽  
Governing Equations ◽  
Numerical Tools ◽  
Volume Method ◽  
The Continuum

The modelling and numerical simulation of the drying process in porous media are discussed in this work with the objective of presenting the drying problem as the system of governing equations, which is ready to be solved by many of the now widely available control-volume-based numerical tools. By reviewing the connection between the transport equations at the pore level and their up-scaled ones at the continuum level and then by transforming these equations into a format that can be solved by the control volume method, we would like to present an easy-to-use framework for studying the drying process in porous media. In order to take into account the microstructure of porous media in the format of pore-size distribution, the concept of bundle of capillaries is used to derive the needed transport parameters. Some numerical examples are presented to demonstrate the use of the presented formulas.

Numerical Simulation of Laminar Confined Impinging Jet in a Composite Channel

2008 ◽  
Author(s):  
Marcelo J. S. de Lemos
Keyword(s):  
Porous Layer ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Local Distribution ◽  
Governing Equations ◽  
Stagnation Region ◽  
Volume Method ◽  
Material Porosity ◽  
Macroscopic Equations

This work shows numerical results for a jet impinging onto a flat plane covered with a layer of a porous material. Porosity of the porous layer is varied in order to analyze its effect on the local distribution of Nu. Macroscopic equations for mass and momentum ae obtained based on the volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Results indicate that inclusion of a porous layer decreases the peak in Nu avoiding excessive heating or cooling near the stagnation region.

Numerical Analysis of Depollution of Smoke Produced by Household Wastes Incineration

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
K. N’Wuitcha ◽  
M. Banna ◽  
S. W. Igo ◽  
B. Zeghmati ◽  
K. Palm ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Radiative Transfer Equation ◽  
Simple Algorithm ◽  
Velocity Fields ◽  
Algebraic Equations ◽  
Governing Equations ◽  
Thomas Algorithm ◽  
Cylindrical Furnace ◽  
Volume Method ◽  
Double Diffusive

This study reports the results on a numerical investigation of the depollution of smokes produced by the incineration of household wastes in a cylindrical furnace. Transfers are described by double-diffusive mixed convection equations, associated to radiative transfer equation, and a global kinetics model. The governing equations are discretized using finite volume method and the resulting algebraic equations are solved by THOMAS algorithm. The linkage between the pressure and velocity fields is assumed by SIMPLE algorithm. Results are presented as streamlines, isotherms, isoconcentrations for different Reynolds number (300 ≤ Re ≤ 1800). Effects of Reynolds number, relative height opening, aspect ratio, excess air ratio, and radiative transfers on gas pollutants (CO, CH4, C2H4…) destruction are investigated in detail.

Influence of Coil Inclined around Y Axis on Thermomagnetic Convection of Air in a Porous Cubic Enclosure under Zerogravity

2011 ◽  
Vol 354-355 ◽  
pp. 24-28 ◽  
Author(s):  
Chang Wei Jiang ◽  
Xian Feng Zhu ◽  
Er Shi ◽  
Zhen Zhou
Keyword(s):  
Heat Transfer ◽  
Magnetic Force ◽  
Vertical Wall ◽  
Simple Algorithm ◽  
Darcy Number ◽  
The Other ◽  
Governing Equations ◽  
Left Hand ◽  
Thermomagnetic Convection ◽  
Volume Method

Thermomagnetic convection of air in a porous cubic enclosure with a electric coil inclined around the Y axis is numerically investigated under zerogravity environment. The porous cubic enclosure is heated isothermally from left-hand side vertical wall and cooled isothermally from opposing wall while the other four walls are thermally insulated. The governing equations in primitive variables are discretized by the finite-volume method and solved by the SIMPLE algorithm. The results show that the overall heat transfer is enhanced gradually with the increase of magnetic force number and Darcy number. The resulted convection is symmetrical in terms of the angle at yeuler =0 when the range of inclination angle is from -90 to 90.

Influence of Coil Inclined around X Axis on Thermomagnetic Convection of Air in a Porous Cubic Enclosure under Zerogravity

2011 ◽  
Vol 354-355 ◽  
pp. 174-178 ◽  
Author(s):  
Chang Wei Jiang ◽  
Ming Zhang ◽  
Xian Feng Zhu
Keyword(s):  
Inclination Angle ◽  
Magnetic Force ◽  
Vertical Wall ◽  
Simple Algorithm ◽  
Darcy Number ◽  
The Other ◽  
Governing Equations ◽  
Left Hand ◽  
Thermomagnetic Convection ◽  
Volume Method

Thermomagnetic convection of air in a porous cubic enclosure with an electric coil inclined around the X axis is numerically investigated under zerogravity environment. The porous cubic enclosure is heated isothermally from left-hand side vertical wall and cooled isothermally from opposing wall while the other four walls are thermally insulated. The governing equations in primitive variables are discretized by the finite-volume method and solved by the SIMPLE algorithm. The results show that the overall heat transfer is enhanced gradually with the increase of magnetic force number and Darcy number. The resulted convection is symmetrical in terms of the inclination angle at xeuler =45 when the range of inclination angle is from 0 to 90 .

Effect of Thermal Conductivity Ratio on Laminar Double-Diffusive Free Convection in a Porous Cavity

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Paulo H. S. Carvalho ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Free Convection ◽  
Thermal Equilibrium ◽  
Control Volume ◽  
Simple Algorithm ◽  
Thermal Conductivity Ratio ◽  
Control Volume Method ◽  
Algebraic Equations ◽  
Square Cavity ◽  
Volume Method ◽  
Double Diffusive

This work presents a study on double-diffusive free convection in a porous square cavity using the thermal equilibrium model. Transport equations are discretized using the control-volume method, and the system of algebraic equations is relaxed via the SIMPLE algorithm. The effect of ks/kf on average Nusselt and Sherwood values was investigated. Results show that increasing ks/kf affects Nuw and Shw boosting mass transfer at the expense of reducing overall heat transport across the enclosure.

Laminar Heat Transfer on a Wall Covered With a Layer of Porous Material Simulated With a Two-Energy Equation Model

2010 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Felipe T. Do´rea
Keyword(s):  
Porous Material ◽  
Control Volume ◽  
Numerical Technique ◽  
Simple Algorithm ◽  
Porous Matrix ◽  
Equation Model ◽  
Energy Model ◽  
Governing Equations ◽  
Volume Method ◽  
Macroscopic Equations

This paper presents simulations for a jet impinging against a flat plane covered with a layer of a porous material. Macroscopic equations for mass, momentum and energy, for the fluid and for the porous matrix, are obtained based on the volume-average concept. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. The effect of porosity and energy model on the local distribution of Nu was analyzed. Results indicate that for low porosity materials, a substantially different Nu number is calculated depending on the energy model applied.

Influence of Micro Trapezoidal-Groove on Behavior of Sliding Tribopairs

2010 ◽  
Vol 37-38 ◽  
pp. 544-549 ◽  
Author(s):  
Pei Yun Zhang ◽  
Yan Hu Zhang ◽  
Xiao Li Wang ◽  
Xi Jun Hua ◽  
Yong Hong Fu
Keyword(s):  
Hydrodynamic Lubrication ◽  
Control Volume ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Tribological Performance ◽  
Control Volume Method ◽  
Supporting Capacity ◽  
Continuity Equations ◽  
Isosceles Trapezoid ◽  
Volume Method

The effect of various micro isosceles-trapezoid grooves on improvement of tribological performance is discussed. It is accomplished through the CFD-approach where the momentum and continuity equations are solved separately, one of low Reynolds turbulence models-Abid index and SIMPLE algorithm in theory of Control Volume Method are adopted. For different width and depth of micro isosceles-trapezoid grooves, the load supporting capacity of oil-film are compared. The results show that the widths has more influence than the depths on hydrodynamic lubrication, and relative parameters change monotonously with the depth of micro-groove. The effect of texturing arc-grooves on improvement of tribological properties is conspicuous if w1= 40μm, w2= 10μm and hp= 10μm for micro isosceles-trapezoid grooves.

Effect of position and height of a shield on convective heat transfer performances of plate fin heat sink

2015 ◽  
Vol 25 (5) ◽  
pp. 1047-1063 ◽  
Author(s):  
Rachid Bouchenafa ◽  
Rachid Saim ◽  
Said Abboudi ◽  
Hakan F. Öztop
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Sink ◽  
Dynamic Performance ◽  
Simple Algorithm ◽  
Governing Equations ◽  
Enhancement Of Heat Transfer ◽  
Content Type ◽  
The One ◽  
Volume Method

Purpose – The purpose of this paper is to examine the thermal and dynamic performance of the plate-fin heat sink fitted with a shield in the bypass. Design/methodology/approach – The governing equations were solved using the finite volume method based on the SIMPLE algorithm. The k-ω Shear Stress Transport was used to model turbulence. The thermal and dynamic results were presented in term of average Nusselt number and friction factor, respectively. The effect of the height (Hs=6, 10 and 13) and the position (X=0, 1/3, 1/2, 2/3 and 3/4) of the shield was studied for a Reynolds number ranging from 2×103 to 12×103 and compared with a heat sink without shield. To evaluate the performance of different heat sink geometries, the efficiency was presented and discussed. Findings – By adding a shield in the bypass, a greater amount of air is injected between the heat sink fins, which improves the heat transfer (advantage) of the one part, and increases the friction on the other hand (disadvantage). The efficiency of the heat sink varies inversely proportional with the Reynolds number. Originality/value – The originality of this work is the method for enhancement of heat transfer.

scholarly journals A New Formulation of Maxwell’s Equations

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 868
Author(s):  
Simona Fialová ◽  
František Pochylý
Keyword(s):  
Numerical Methods ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Control Volume ◽  
Control Volume Method ◽  
Integral Forms ◽  
New Formulation ◽  
Electrical Induction ◽  
Volume Method ◽  
Integral Identities

In this paper, new forms of Maxwell’s equations in vector and scalar variants are presented. The new forms are based on the use of Gauss’s theorem for magnetic induction and electrical induction. The equations are formulated in both differential and integral forms. In particular, the new forms of the equations relate to the non-stationary expressions and their integral identities. The indicated methodology enables a thorough analysis of non-stationary boundary conditions on the behavior of electromagnetic fields in multiple continuous regions. It can be used both for qualitative analysis and in numerical methods (control volume method) and optimization. The last Section introduces an application to equations of magnetic fluid in both differential and integral forms.

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