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Dissertation

Parallel object-oriented algorithms for simulation of multiphysics : application to thermal systems

05 Feb 2016-
TL;DR: This PhD thesis presents the development of parallel methodologies, and its implementation as an object-oriented software platform, for the simulation of multiphysics systems, and poses a new paradigm in the production of physics simulation programs.
Abstract: The present and the future expectation in parallel computing pose a new generational change in simulation and computing. Modern High Performance Computing (HPC) facilities have high computational power in terms of operations per second -today peta-FLOPS (10e15 FLOPS) and growing toward the exascale (10e18 FLOPS) which is expected in few years-. This opens the way for using simulation tools in a wide range of new engineering and scientific applications. For example, CFD&HT codes will be effectively used in the design phase of industrial devices, obtaining valuable information with reasonable time expenses. However, the use of the emerging computer architectures is subjected to enhancements and innovation in software design patterns. So far, powerful codes for individually studying heat and mass transfer phenomena at multiple levels of modeling are available. However, there is no way to combine them for resolving complex coupled problems. In the current context, this PhD thesis presents the development of parallel methodologies, and its implementation as an object-oriented software platform, for the simulation of multiphysics systems. By means of this new software platform, called NEST, the distinct codes can now be integrated into single simulation tools for specific applications of social and industrial interest. This is done in an intuitive and simple way so that the researchers do not have to bother either on the coexistence of several codes at the same time neither on how they interact to each other. The coupling of the involved components is controlled from a low level code layer, which is transparent to the users. This contributes with appealing benefits on software projects management first and on the flexibility and features of the simulations, later. In sum, the presented approaches pose a new paradigm in the production of physics simulation programs. Although the thesis pursues general purpose applications, special emphasis is placed on the simulation of thermal systems, in particular on buildings energy assessment and on hermetic reciprocating compressors.
Citations
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01 Jan 2016
TL;DR: The numerical heat transfer and fluid flow is universally compatible with any devices to read and is available in the authors' digital library an online access to it is set as public so you can get it instantly.
Abstract: Thank you for reading numerical heat transfer and fluid flow. Maybe you have knowledge that, people have search numerous times for their favorite books like this numerical heat transfer and fluid flow, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some malicious virus inside their computer. numerical heat transfer and fluid flow is available in our digital library an online access to it is set as public so you can get it instantly. Our books collection spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the numerical heat transfer and fluid flow is universally compatible with any devices to read.

1,531 citations

Journal ArticleDOI
TL;DR: In this article, a generalized three-dimensional computational model based on unstructured meshes is presented, capable to simulate all potential geometries, demonstrating quantitatively the strong impact of the solid volume fraction, fin length and fin thickness on the performance.

25 citations


Cites methods from "Parallel object-oriented algorithms..."

  • ...The interaction of the two domains was carried out using the NEST platform, an in-house C++ object-oriented tool for the conjugate simulation of models of arbitrary complexity [45]....

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01 Jan 2016
TL;DR: In this paper, a partitioned semi-implicit coupling scheme is implemented, which only strongly couples the added mass-effect (pressure term) of the fluid to the structure hence, assuring numerical stability and avoiding excessive computational cost.
Abstract: This paper presents a complete numerical procedure to study the fluid-structure interaction problem of incompressible flow through reed valves, typically employed in hermetic reciprocating compressors. A partitioned semi-implicit coupling scheme is implemented, which only strongly couples the added-mass-effect (pressure term) of the fluid to the structure hence, assuring numerical stability and avoiding excessive computational cost. The fluid is solved by a three-dimensional CFD solver using large eddy simulation closures to model the turbulent flow, while the reed valve is described with the classical plate theory and the normal mode summation method. To showcase the potentiality of the proposed methodology, a sensitivity analysis regarding valve thickness is carried out for a given velocity in the feeding channel. Considerable differences, mainly in valve lift and pressure drop, are appreciated between the considered configurations.

12 citations


Cites background or methods from "Parallel object-oriented algorithms..."

  • ...Figure 2: Suction mass flow profile extracted from Lopez (2016)....

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  • ...It is a time dependent mass flow that belongs to the suction process of a one-dimensional simulation of a hermetic reciprocating compressor, Figure 2 (Lopez, 2016)....

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01 Jan 1995
TL;DR: In this article, heat and mass transfer in the recirculation region of a pipe under steady and pulsatile conditions were studied under uniform and parabolic entrance velocity profiles and the results demonstrate the complexity of separation flows and identify characteristic regions of high and low heat/mass transfer.
Abstract: Abstract Heat and mass transfer phenomena were studied in the sudden expansion region of a pipe under steady and pulsatile conditions. The Prandtl number was varied from 100 to 12 000 and the flow was characterized for both uniform and parabolic entrance velocity profiles. A uniform velocity profile was used for pulsatile flow. It was found that heat transfer in the recirculation region was maximal near the area where wall shear was minimal. Blunting of the inlet profile caused the point of maximum heat transfer to move upstream. There was a nonlinear effect of Prandtl number on heat transfer which plateaued for Pr > 10 3 . The wall shear rate in the separation zone varied markedly with pulsatile flows, but the wall heat transfer remained relatively constant. The time-averaged pulsatile heat transfer at the wall was approximately the same as with steady flow with the mean Reynolds number. However, the isotherms within the pulsatile flow were markedly different from steady flow. The results demonstrate the complexity of separation flows and identify characteristic regions of high and low heat/mass transfer for high Prandtl/Schmidt pulsatile flow.

4 citations

Dissertation
12 Jan 2017
TL;DR: For a building with only 9 rooms the new solver is a thousand times faster than the current method, and an implicit method based on the Trust Region algorithm is proposed.
Abstract: Building energy simulation is playing a key role in building design in order to reduce the energy consumption and, consequently, the CO2 emissions. An object-oriented tool called NEST is used to simulate all the phenomena that appear in a building. In the case of energy and momentum conservation and species transport, the current solver behaves well, but in the case of mass conservation it takes a lot of time to reach a solution. For this reason, in this work, instead of solving the continuity equations explicitly, an implicit method based on the Trust Region algorithm is proposed. Previously, a study of the properties of the model used by NEST-Building software has been done in order to simplify the requirements of the solver. For a building with only 9 rooms the new solver is a thousand times faster than the current method.

3 citations


Cites background or methods from "Parallel object-oriented algorithms..."

  • ...As López said in his thesis [10], "this partitioned approach provides an efficient and practical way to simulate buildings....

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  • ...NEST is an object-oriented tool that "consists on a set of individual numerical sub-models that solve the conservation laws of mass [· · · ] along the buildings spaces and components" [10]....

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  • ...Turning to the Rooms sub-model, as the Openings objects are placed at the boundaries of the control volume, the equation of continuity is [3, 10] ∂mP ∂t = ∑ k∈Inlet ṁk − ∑ k∈Outlet ṁk, ∀P ∈ Rooms ....

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  • ...There are sub-models for walls, for example, used in the energy balance that "solve the thermal interaction between the rooms and between the rooms and the exterior" [10]....

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  • ...To achieve a reasonable balance between them, some software use a modular object-oriented simulation tool [3, 4, 10, 19]....

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References
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01 Jan 1981
TL;DR: In this article, a comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation, and the use of the Monte Carlo technique in solving radiant exchange problems and problems of radiative transfer through absorbing-emitting media.
Abstract: A comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation. Among the topics considered are property prediction by electromagnetic theory, the observed properties of solid materials, radiation in the presence of other modes of energy transfer, the equations of transfer for an absorbing-emitting gas, and radiative transfer in scattering and absorbing media. Also considered are radiation exchange between black isothermal surfaces, radiation exchange in enclosures composed of diffuse gray surfaces and in enclosures having some specularly reflecting surfaces, and radiation exchange between nondiffuse nongray surfaces. The use of the Monte Carlo technique in solving radiant-exchange problems and problems of radiative transfer through absorbing-emitting media is explained.

5,879 citations

Book
01 Jan 1971
TL;DR: In this paper, a comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation, and the use of the Monte Carlo technique in solving radiant exchange problems and problems of radiative transfer through absorbing-emitting media.
Abstract: A comprehensive discussion of heat transfer by thermal radiation is presented, including the radiative behavior of materials, radiation between surfaces, and gas radiation. Among the topics considered are property prediction by electromagnetic theory, the observed properties of solid materials, radiation in the presence of other modes of energy transfer, the equations of transfer for an absorbing-emitting gas, and radiative transfer in scattering and absorbing media. Also considered are radiation exchange between black isothermal surfaces, radiation exchange in enclosures composed of diffuse gray surfaces and in enclosures having some specularly reflecting surfaces, and radiation exchange between nondiffuse nongray surfaces. The use of the Monte Carlo technique in solving radiant-exchange problems and problems of radiative transfer through absorbing-emitting media is explained.

5,420 citations

Journal ArticleDOI
01 Jun 1974-Nature
TL;DR: Chlorofluoromethanes are being added to the environment in steadily increasing amounts as discussed by the authors and these compounds are chemically inert and may remain in the atmosphere for 40 to 150 years, and concentrations can be expected to reach 10 to 30 times present levels.
Abstract: Chlorofluoromethanes are being added to the environment in steadily increasing amounts. These compounds are chemically inert and may remain in the atmosphere for 40–150 years, and concentrations can be expected to reach 10 to 30 times present levels. Photodissociation of the Chlorofluoromethanes in the stratosphere produces significant amounts of chlorine atoms, and leads to the destruction of atmospheric ozone.

3,888 citations

Journal ArticleDOI
01 May 1985-Nature
TL;DR: In this article, it was shown that the very low temperatures which prevail from midwinter until several weeks after the spring equinox make the Antarctic stratosphere uniquely sensitive to growth of inorganic chlorine, ClX, primarily by the effect of this growth on the NO2/NO ratio.
Abstract: Recent attempts1,2 to consolidate assessments of the effect of human activities on stratospheric ozone (O3) using one-dimensional models for 30° N have suggested that perturbations of total O3 will remain small for at least the next decade. Results from such models are often accepted by default as global estimates3. The inadequacy of this approach is here made evident by observations that the spring values of total O3 in Antarctica have now fallen considerably. The circulation in the lower stratosphere is apparently unchanged, and possible chemical causes must be considered. We suggest that the very low temperatures which prevail from midwinter until several weeks after the spring equinox make the Antarctic stratosphere uniquely sensitive to growth of inorganic chlorine, ClX, primarily by the effect of this growth on the NO2/NO ratio. This, with the height distribution of UV irradiation peculiar to the polar stratosphere, could account for the O3 losses observed.

3,131 citations

Book
01 Nov 1997
TL;DR: In this article, the basic concepts of thermodynamics and heat transfer heat conduction are discussed, and numerical methods in heat transfer forced convection natural convection boiling and condensation radiation heat-transfer heat exchangers mass transfer.
Abstract: Part 1 Fundamentals: basic concepts of thermodynamics and heat transfer heat conduction steady heat conduction transient heat conduction numerical methods in heat transfer forced convection natural convection boiling and condensation radiation heat transfer heat exchangers mass transfer. Part 2 Applications: heating and cooling of buildings refrigeration and freezing of foods cooling of electronic equipment property tables and charts (SI units and English units) about the software.

2,095 citations