scholarly journals Computational study of the application of Al2O3 nanoparticles to forced convection of high-Reynolds swirling jets for engineering cooling processes

2020 ◽  
Vol 15 (1) ◽  
pp. 1-22
Author(s):  
F.-J. Granados-Ortiz ◽  
L. Leon-Prieto ◽  
J. Ortega-Casanova
Keyword(s):  
Forced Convection ◽  
Computational Study ◽  
Al2o3 Nanoparticles ◽  
Swirling Jets ◽  
High Reynolds

The Combustion of a Liquid Fuel Droplet during Forced Convection

1994 ◽  
Vol 12 (1) ◽  
pp. 44-61
Author(s):  
Andrzej Teodorczyk ◽  
Stanislaw Wójcicki
Keyword(s):  
Reynolds Number ◽  
Forced Convection ◽  
Droplet Diameter ◽  
Fuel Droplet ◽  
Combus Tion ◽  
Air Stream ◽  
Freely Suspended ◽  
High Reynolds ◽  
Additional Support ◽  
Physical And Mathematical Models

A new experimental technique was used to investigate single fuel droplet combustion during forced convection: the burning droplet was freely suspended in the controlled air stream, without any additional support. Based on the photo-records of the burning process, the characteristics of the change of square of droplet diameter with time were made and the actual values of burning constants were determined for four hydrocarbon fuels: ben zene, n-heptane, iso-octane and toluene. The experiments were also carried out under micro-gravity and free convection conditions for the same set of fuels. The investigations have allowed the comparison of the burning mechanism of a single droplet for the three different external conditions and have compared quantitatively the burning constants. On the basis of the color pictures of the droplet burning under forced convection conditions and the temperature and gas concentration measurements within the flame, the mechanism of combus tion of fuel droplet was explained. The physical and mathematical models of the process have been proposed which included the aerodynamics of the droplet located in the high Reynolds number air stream, the energy balance of the evaporating droplet and the chemical reaction in the flow. The models have made it possible to determine the quantitative dependence of the burning con stant of different kinds of fuels on Reynolds number, the flow field parameters and the physical and chemical parameters of the liquid and its close surround ings. The calculated values of the parameters describing the burning pro cess have been compared to the experimental data and to the results reported by other investigators. The model has revealed the importance of the feed back mechanism between physical processes involved during droplet combus tion.

scholarly journals On the Transition From Creeping to Inertial Flow in Arrays of Cylinders

2010 ◽  
Author(s):  
K. Yazdchi ◽  
S. Srivastava ◽  
S. Luding
Keyword(s):  
Porous Media ◽  
Darcy’S Law ◽  
Computational Study ◽  
Darcy's Law ◽  
Natural Processes ◽  
Inertial Flow ◽  
Flow Through ◽  
High Reynolds ◽  
An Array Of Cylinders ◽  
Element Method

Many important natural processes involving flow through porous media are characterized by large filtration velocity. Therefore, it is important to know when the transition from viscous to the inertial flow regime actually occurs in order to obtain accurate models for these processes. In this paper, a detailed computational study of laminar and inertial, incompressible, Newtonian fluid flow across an array of cylinders is presented. Due to the non-linear contribution of inertia to the transport of momentum at the pore scale, we observe a typical departure from Darcy’s law at sufficiently high Reynolds number (Re). Our numerical results show that the weak inertia correction to Darcy’s law is not a square or a cubic term in velocity, as it is in the Forchheimer equation. Best fitted functions for the macroscopic properties of porous media in terms of microstructure and porosity are derived and comparisons are made to the Ergun and Forchheimer relations to examine their relevance in the given porosity and Re range. The results from this study can be used for verification and validation of more advanced models for particle fluid interaction and for the coupling of the discrete element method (DEM) with finite element method (FEM).

Dissipation in Implicit Turbulence Models: A Computational Study

2003 ◽  
Author(s):  
L. G. Margolin ◽  
P. K. Smolarkiewicz ◽  
A. A. Wyszogrodzki
Keyword(s):  
Numerical Simulation ◽  
Preliminary Analysis ◽  
High Reynolds Number ◽  
Computational Study ◽  
Turbulence Models ◽  
Finite Volume Methods ◽  
Data Set ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

We describe a series of computational experiments that employ nonoscillatory finite volume methods to simulate the decay of high Reynolds number turbulence. These experiments cover a broad range of physical viscosities and numerical resolutions. We have extracted a data set from these experiments detailing the energy dissipation by physical viscosity and by the numerical algorithm. We offer a preliminary analysis of this data, including new insights into the (computational) transition between direct numerical simulation and large eddy simulation.

scholarly journals Computational Study of Heat Transfer inside Different PCMs Enhanced by Al2O3 Nanoparticles in a Copper Heat Sink at High Heat Loads

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 284 ◽  
Author(s):  
Nadezhda S. Bondareva ◽  
Nikita S. Gibanov ◽  
Mikhail A. Sheremet
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Computational Study ◽  
Conjugate Problem ◽  
High Heat ◽  
Solid Particles ◽  
Heat Sinks ◽  
Al2o3 Nanoparticles ◽  
Electronic Elements ◽  
The Impact

The cooling of electronic elements is one of the most important problems in the development of architecture in electronic technology. One promising developing cooling method is heat sinks based on the phase change materials (PCMs) enhanced by nano-sized solid particles. In this paper, the influence of the PCM’s physical properties and the concentration of nanoparticles on heat and mass transfer inside a closed radiator with fins, in the presence of a source of constant volumetric heat generation, is analyzed. The conjugate problem of nano-enhanced phase change materials (NePCMs) melting is considered, taking into account natural convection in the melt under the impact of the external convective cooling. A two-dimensional problem is formulated in the non-primitive variables, such as stream function and vorticity. A single-phase nano-liquid model is employed to describe the transport within NePCMs.

Dissipation in Implicit Turbulence Models: A Computational Study

2006 ◽  
Vol 73 (3) ◽  
pp. 469-473 ◽  
Author(s):  
L. G. Margolin ◽  
P. K. Smolarkiewicz ◽  
A. A. Wyszogradzki
Keyword(s):  
Numerical Simulation ◽  
Preliminary Analysis ◽  
High Reynolds Number ◽  
Computational Study ◽  
Turbulence Models ◽  
Finite Volume Methods ◽  
Data Set ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

We describe a series of computational experiments that employ nonoscillatory finite volume methods to simulate the decay of high Reynolds number turbulence. These experiments cover a broad range of physical viscosities and numerical resolutions. We have extracted a data set from these experiments detailing the energy dissipation by physical viscosity and by the numerical algorithm. We offer a preliminary analysis of this data, including new insights into the (computational) transition between direct numerical simulation and large eddy simulation.

scholarly journals Computational Study of a Transverse Rotor Aircraft in Hover Using the Unsteady Vortex Lattice Method

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Juan D. Colmenares ◽  
Omar D. López ◽  
Sergio Preidikman
Keyword(s):  
Vortex Lattice ◽  
Computational Study ◽  
Pitching Moment ◽  
Considerable Influence ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Geometric Configurations ◽  
Hover Flight ◽  
High Reynolds ◽  
The Stability

This paper presents the simulation of a two-rotor aircraft in different geometric configurations during hover flight. The analysis was performed using an implementation of the unsteady vortex-lattice method (UVLM). A description of the UVLM is presented as well as the techniques used to enhance the stability of results for rotors in hover flight. The model is validated for an isolated rotor in hover, comparing numerical results to experimental data (high-Reynolds, low-Mach conditions). Results show that an exclusion of the root vortex generates a more stable wake, without affecting results. Results for the two-rotor aircraft show an important influence of the number of blades on the vertical thrust. Furthermore, the geometric configuration has a considerable influence on the pitching moment.

Computational Study of Turbulent Forced Convection Flow in a Square Cavity with Ventilation Ports

2011 ◽  
Vol 59 (12) ◽  
pp. 954-969 ◽  
Author(s):  
E. Sourtiji ◽  
S. F. Hosseinizadeh ◽  
M. Gorji-Bandpy ◽  
J. M. Khodadadi
Keyword(s):  
Forced Convection ◽  
Computational Study ◽  
Convection Flow ◽  
Square Cavity ◽  
Forced Convection Flow

Laminar Forced Convection Mass Transfer to Ordered and Disordered Single Layer Arrays of Micro-Spheres

2012 ◽  
Author(s):  
D. Ambesi ◽  
C. R. Kleijn
Keyword(s):  
Mass Transfer ◽  
Forced Convection ◽  
Sherwood Number ◽  
Single Layer ◽  
Reynolds Numbers ◽  
Frontal Area ◽  
High Reynolds Numbers ◽  
Schmidt Numbers ◽  
High Reynolds ◽  
Laminar Forced Convection

We study laminar forced convection mass transfer to single layer arrays of equidistantly and non-equidistantly spaced micro-spheres. We report average Sherwood numbers as a function of geometry and flow conditions, for open frontal area fractions between 0.04 and 0.95, Schmidt numbers between 0.7 and 10, and Reynolds numbers (based on micro-sphere diameter and the free stream velocity) between 0.1 and 100. For equidistantly spaced arrays of micro-spheres we propose a general analytical expression for the average Sherwood number as a function of the Reynolds number, Schmidt number and the open frontal area fraction, as well as asymptotic scaling rules for small and large Reynolds. For all studied Schmidt numbers, equidistant arrays exhibit decreasing average Sherwood numbers for decreasing open frontal area fractions at low Reynolds numbers. For high Reynolds numbers, the Sherwood number approaches that of a single spheres in cross-flow, independent of the open frontal area fraction. For equal open frontal area fractions, the Sherwood number in non-equidistant arrays is lower than in equidistant arrays for intermediate Reynolds numbers. For very low and high Reynolds numbers, non-uniformity does not influence mass transfer.

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