Direct Simulation of Transport in Open-Cell Metal Foam

2006 ◽  
Vol 128 (8) ◽  
pp. 793-799 ◽  
Author(s):  
Shankar Krishnan ◽  
Jayathi Y. Murthy ◽  
Suresh V. Garimella
Keyword(s):  
Metal Foam ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Unit Cell ◽  
Computational Time ◽  
Small Scale ◽  
Direct Simulation ◽  
Open Cell ◽  
Periodic Unit Cell

Flows in porous media may be modeled using two major classes of approaches: (a) a macroscopic approach, where volume-averaged semiempirical equations are used to describe flow characteristics, and (b) a microscopic approach, where small-scale flow details are simulated by considering the specific geometry of the porous medium. In the first approach, small-scale details are ignored and the information so lost is represented in the governing equations using an engineering model. In the second, the intricate geometry of the porous structures is accounted for and the transport through these structures computed. The latter approach is computationally expensive if the entire physical domain were to be simulated. Computational time can be reduced by exploiting periodicity when it exists. In the present work we carry out a direct simulation of the transport in an open-cell metal foam using a periodic unit cell. The foam geometry is created by assuming the pore to be spherical. The spheres are located at the vertices and at the center of the unit cell. The periodic foam geometry is obtained by subtracting the unit cell cube from the spheres. Fluid and heat flow are computed in the periodic unit cell. Our objective in the present study is to obtain the effective thermal conductivity, pressure drop, and local heat transfer coefficient from a consistent direct simulation of the open-cell foam structure. The computed values compare well with the existing experimental measurements and semiempirical models for porosities greater than 94%. The results and the merits of the present approach are discussed.

scholarly journals Direct Simulation of Transport in Open-Cell Metal Foams

2005 ◽  
Author(s):  
Shankar Krishnan ◽  
Jayathi Y. Murthy ◽  
Suresh V. Garimella
Keyword(s):  
Metal Foam ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Unit Cell ◽  
Small Scale ◽  
Direct Simulation ◽  
Open Cell ◽  
Semi Empirical ◽  
Periodic Unit Cell

Flows in porous media may be modeled using either a macroscopic approach, where volume-averaged semi-empirical equations are used to describe flow characteristics, or a microscopic approach, where small-scale flow details are simulated by considering the specific geometry of the porous medium. A direct simulation of the transport in an open-cell metal foam is carried out in the present study using a periodic unit cell. The foam geometry is created by assuming the pore to be spherical. The spheres are located at the vertices and at the center of the unit cell. The periodic foam geometry is obtained by subtracting the unit cell cube from the spheres. Fluid and heat flow are computed in the periodic unit cell. The objective of the present study is to obtain the effective thermal conductivity, pressure drop and local heat transfer coefficient from a consistent direct simulation of the open-cell foam structure. The computed values compare well with the existing experimental measurements and semi-empirical models. The results and the merits of the present approach are discussed.

scholarly journals Simulation of Thermal Transport in Open-Cell Metal Foams: Effect of Periodic Unit Cell Structure

2006 ◽  
Author(s):  
Shankar Krishnan ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Thermal Transport ◽  
Pore Space ◽  
Cell Structure ◽  
Flow Characteristics ◽  
Metal Foams ◽  
Unit Cube ◽  
Unit Cell ◽  
Face Centered Cubic ◽  
Open Cell ◽  
Periodic Unit Cell

Direct simulation of thermal transport in open-cell metal foams is conducted using different periodic unit cell geometries. The periodic unit cell structures are constructed by assuming the pore space to be spherical and subtracting the pore space from a unit cube of the metal. Different types of packing arrangement for spheres are considered - Body Centered Cubic, Face Centered Cubic, and the A15 lattice (similar to a Weaire-Phelan unit cell) - which give rise to different foam structures. Effective thermal conductivity, pressure drop and Nusselt number are computed by imposing periodic boundary conditions for aluminum foams saturated with air or water. The computed values compare well with existing experimental measurements and semi-empirical models for porosities greater than 80%. The effect of different foam packing arrangements on the computed thermal and fluid flow characteristics is discussed. The capabilities and limitations of the present approach are identified.

scholarly journals Simulation of Thermal Transport in Open-Cell Metal Foams: Effect of Periodic Unit-Cell Structure

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Shankar Krishnan ◽  
Suresh V. Garimella ◽  
Jayathi Y. Murthy
Keyword(s):  
Thermal Transport ◽  
Pore Space ◽  
Cell Structure ◽  
Flow Characteristics ◽  
Metal Foams ◽  
Unit Cube ◽  
Unit Cell ◽  
Face Centered Cubic ◽  
Open Cell ◽  
Periodic Unit Cell

Direct simulation of thermal transport in open-cell metal foams is conducted using different periodic unit-cell geometries. The periodic unit-cell structures are constructed by assuming the pore space to be spherical and subtracting the pore space from a unit cube of the metal. Different types of packing arrangement for spheres are considered—body centered cubic, face centered cubic, and the A15 lattice (similar to a Weaire-Phelan unit cell)—which give rise to different foam structures. Effective thermal conductivity, pressure drop, and Nusselt number are computed by imposing periodic boundary conditions for aluminum foams saturated with air or water. The computed values compare well with existing experimental measurements and semiempirical models for porosities greater than 80%. The effect of different foam packing arrangements on the computed thermal and fluid flow characteristics is discussed. The capabilities and limitations of the present approach are identified.

Development of High Order LES Solver for Heat Transfer Applications Based on the Open Source OpenFOAM Framework

2015 ◽  
Author(s):  
Luca Mangani ◽  
David Roos Launchbury ◽  
Ernesto Casartelli ◽  
Giulio Romanelli
Keyword(s):  
Heat Transfer ◽  
Open Source ◽  
Gas Turbines ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
High Order ◽  
Computational Time

The computation of heat transfer phenomena in gas turbines plays a key role in the continuous quest to increase performance and life of both component and machine. In order to assess different cooling approaches computational fluid dynamics (CFD) is a fundamental tool. Until now the task has often been carried out with RANS simulations, mainly due to the relatively short computational time. The clear drawback of this approach is in terms of accuracy, especially in those situations where averaged turbulence-structures are not able to capture the flow physics, thus under or overestimating the local heat transfer. The present work shows the development of a new explicit high-order incompressible solver for time-dependent flows based on the open source C++ Toolbox OpenFOAM framework. As such, the solver is enabled to compute the spatially filtered Navier-Stokes equations applied in large eddy simulations for incompressible flows. An overview of the development methods is provided, presenting numerical and algorithmic details. The solver is verified using the method of manufactured solutions, and a series of numerical experiments is performed to show third-order accuracy in time and low temporal error levels. Typical cooling devices in turbomachinery applications are then investigated, such as the flow over a turbulator geometry involving heated walls and a film cooling application. The performance of various sub-grid-scale models are tested, such as static Smagorinsky, dynamic Lagrangian, dynamic one-equation turbulence models, dynamic Smagorinsky, WALE and sigma-model. Good results were obtained in all cases with variations among the individual models.

scholarly journals Local Heat Transfer and Flow Characteristics in Two-Pass Channels with an Inclined Divider Wall.

2002 ◽  
Vol 68 (669) ◽  
pp. 1523-1530
Author(s):  
Masafumi HIROTA ◽  
Hiroshi NAKAYAMA ◽  
Lei CAI ◽  
Hideomi FUJITA ◽  
Tatsuhito KATOH ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat

Numerical Prediction of Flow and Heat Transfer Past a Circular Tube With Annular Fins

2003 ◽  
Author(s):  
D. Chakraborty ◽  
G. Biswas ◽  
P. K. Panigrahi
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Stagnation Line ◽  
Flow And Heat Transfer ◽  
Annular Fin ◽  
Annular Fins

A numerical investigation was carried out to study the flow and heat transfer behavior of a vertical circular tube, which is situated between two annular fins in cross-flow. The flow structure of the limiting streamlines on the surface of the circular tube and the annular fins was analysed. A finite volume method was employed to solve the Navier-Stokes and energy equations. The numerical results pertaining to heat transfer and flow characteristics were compared with the available experimental results. The following salient features were observed in this configuration. A horseshoe vortex system was formed at the junction of the stagnation line of the circular tube and the annular fin. The separation took place at the rear of the tube. The influence of the horseshoe vortices on local heat transfer was substantial. The ratio of the axial gap between two annular fins (L) to the radial protrusion length of the annular fin (LR) was identified as an important parameter. The flow and heat transfer results were presented for different L/LR ratios for a Reynolds number of 1000.

Numerical Investigation of Heat Transfer Enhancement on a Small Scale Vortex Generator

2009 ◽  
Author(s):  
Jiansheng Wang ◽  
Zhiqin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Small Scale ◽  
Transfer Enhancement

The heat transfer characteristic and flow structure of fluid in the rectangular channel with different height vortex generators in small scale are investigated with numerical simulation. Meantime, the properties of heat transfer and flow of fluid in the rectangular channel are compared with the channel which located small scale vortex generator. The variation law of local heat transfer and flow structure in channel is obtained. The mechanism of heat transfer enhancement of small scale vortex generators is discussed in detail. It is found that the influence of vortex generator on heat transfer is not in proportion to the size of vortex generator. What is more, turbulent flow structure near the wall, which influences the temperature distribution near the wall, induces the variety of local heat transfer. The fluid movement towards to the wall causes the heat transfer enhanced. On the contrary, the fluid movement away from the wall decreases the local heat transfer.

Pore Scale Investigation of Heat Conduction of High Porosity Open-Cell Metal Foam/Paraffin Composite

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Conduction ◽  
Pore Size ◽  
Metal Foam ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Scale Model ◽  
Small Scale ◽  
High Porosity ◽  
Pore Scale ◽  
Open Cell

In this paper, a numerical model employing an approximately realistic three-dimensional (3D) foam structure represented by Weaire–Phelan foam cell is developed to study the steady-state heat conduction of high porosity open-cell metal foam/paraffin composite at the pore-scale level. The conduction problem is considered in a cubic representative computation unit of the composite material with a constant temperature difference between one opposite sides of the cubic unit (the other outer surfaces of the cubic unit are thermally insulated). The effective thermal conductivities (ETCs) of metal foam/paraffin composites are calculated with the developed pore-scale model considering small-scale details of heat conduction, which avoids using adjustable free parameters that are usually adopted in the previous analytical models. Then, the reason why the foam pore size has no evident effect on ETC as reported in the previous macroscopic experimental studies is explored at pore scale. Finally, the effect of air cavities existing within solid paraffin in foam pore region on conduction capacity of metal foam/paraffin composite is investigated. It is found that our ETC data agree well with the reported experimental results, and thus by direct numerical simulation (DNS), the ETC data of different metal foam/paraffin composites are provided for engineering applications. The essential reason why pore size has no evident effect on ETC is due to the negligible interstitial heat transfer between metal foam and paraffin under the present thermal boundary conditions usually used to determine the ETC. It also shows that overlarge volume fraction of air cavity significantly weakens the conduction capacity of paraffin, which however can be overcome by the adoption of high conductive metal foam due to enhancement of conduction.

scholarly journals PIV measurement of complex flow characteristics in open-cell metal foam replica

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Minsin Kim ◽  
Youngwoo Kim ◽  
Sajjad Hosseini ◽  
Kyung Chun Kim
Keyword(s):  
Reynolds Number ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Complex Flow ◽  
Time Resolved ◽  
Open Cell ◽  
Flow Disturbances ◽  
Piv Measurement ◽  
Inlet Conditions

Time-resolved 2-D particle image velocimetry was used to study on turbulent flow characteristics inside an open-cell metal foam under the laminar and turbulent inlet conditions. A study on the effect of Reynolds number was conducted with different three channel Reynolds numbers, 1000, 5000 and 10000. Uniform upstream flow is divided by the pore network of metal foam and it is found that there are flow disturbances induced by metal foam structure even at a laminar inlet condition. It is confirmed that there is a similarity of the preferred flow path flows take regardless of Reynolds number.

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