A "poor man's" approach for high-resolution three-dimensional topology optimization of natural convection problems

This paper treats topology optimization of natural convection problems. A simplified model is suggested to describe the flow of an incompressible fluid in steady state conditions, similar to Darcy's law for fluid flow in porous media. The equations for the fluid flow are coupled to the thermal convection-diffusion equation through the Boussinesq approximation. The coupled non-linear system of equations is discretized with stabilized finite elements and solved in a parallel framework that allows for the optimization of high resolution three-dimensional problems. A density-based topology optimization approach is used, where a two-material interpolation scheme is applied to both the permeability and conductivity of the distributed material. Due to the simplified model, the proposed methodology allows for a significant reduction of the computational effort required in the optimization. At the same time, it is significantly more accurate than even simpler models that rely on convection boundary conditions based on Newton's law of cooling. The methodology discussed herein is applied to the optimization-based design of three-dimensional heat sinks. The final designs are formally compared with results of previous work obtained from solving the full set of Navier-Stokes equations. The results are compared in terms of performance of the optimized designs and computational cost. The computational time is shown to be decreased to around 5-20% in terms of core-hours, allowing for the possibility of generating an optimized design during the workday on a small computational cluster and overnight on a high-end desktop

Aeronautical engineering: A continuing bibliography with indexes (supplement 323)

This bibliography lists 518 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 321)

This bibliography lists 496 reports, articles, and other documents introduced into the NASA scientific and technical information system in Sep. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

A FILTER-FORCING TURBULENCE MODEL FOR LARGE EDDY SIMULATION INCORPORATING THE COMPRESSIBLE POOR MAN\u27S NAVIER--STOKES EQUATIONS

A new approach to large-eddy simulation (LES) based on the use of explicit spatial filtering combined with backscatter forcing is presented. The forcing uses a discrete dynamical system (DDS) called the compressible ``poor man\u27s\u27\u27 Navier--Stokes (CPMNS) equations. This DDS is derived from the governing equations and is shown to exhibit good spectral and dynamical properties for use in a turbulence model. An overview and critique of existing turbulence theory and turbulence models is given. A comprehensive theoretical case is presented arguing that traditional LES equations contain unresolved scales in terms generally thought to be resolved, and that this can only be solved with explicit filtering. The CPMNS equations are then incorporated into a simple forcing in the OVERFLOW compressible flow code, and tests are done on homogeneous, isotropic, decaying turbulence, a Mach 3 compression ramp, and a Mach 0.8 open cavity. The numerical results validate the general filter-forcing approach, although they also reveal inadequacies in OVERFLOW and that the current approach is likely too simple to be universally applicable. Two new proposals for constructing better forcing models are presented at the end of the work

Energy: A continuing bibliography with indexes, issue 39

This bibliography lists 1377 reports, articles and other documents introduced into the NASA scientific and technical information system from July 1, 1983 through September 30, 1983

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

The potential of building-integrated photovoltaic systems in Zimbabwe and their application to thermal environmental control

A strategy has been devised to assist the photovoltaic technology to evolve to the point where it should be a major player in the provision of sustainable energy supplies to loads that are in grid-connected locations in Zimbabwe. The strategy has been devised through an investigation carried out on grid-connected commercial-building loads. The objective of the research undertaken in this programme is to formulate a novel strategy of utilising the photovoltaic technology such that viable financial mechanisms which will provide the funding for the photovoltaic technology in the target area are stimulated. Many financial mechanisms have been given global impetus but it has been generally acknowledged that the success of all renewable energy technologies is dependent on introducing them in such a manner that local finances are capable of funding them. This can only be achieved by persuading existing financial structures to accept these technologies by penetrating the market which these structures are used to dealing with. The financial structures can then be steered, from within, towards the target market. The strategy also builds on the successes achieved by international donor-funded projects in identifying the market potential of utilising photovoltaics as in the GEF PV projects, and the technical viability of the local industry to support the technology as in the GTZ PV projects. It establishes a new method of increasing the capacity of the photovoltaic systems in the region under consideration to a level where it would set a trend that can accelerate the decrease in the cost of the photovoltaic technology in the local area. This adds a fifth dimension to the four major directions being taken to reduce costs of photovoltaic systems, which are reducing the amount of solar materials used; reducing the amount of energy and labour used in processing; using alternative manufacturing equipment; and investigating novel solar materials. The strategy proposed is based on the concept that optimising the perfomance of the energy generating system, optimising the efficiency of the system whose energy load is met by the power system and continually identifying market-efficient applications of the technology on which the power system is based is part and parcel of achieving a sustainable base for the long term utilisation of the technology. It shows the best way of removing the negative view that is widely held that excluding applying the state-of-the-art of a technology in the major markets of photovoltaics, the developing countries, is the only viable way of achieving development. It also lays the basis for the efficient introduction of smart energy-efficient appliances and novel solar devices such as transparent solar cells and AC modules as well as concentrator technology in future, when these concepts have progressed out of the laboratory. In this project commercial buildings in a chosen benchmark city were used as the energy demanding load. Photovoltaic arrays integrated in to the building facades were taken as the energy-generating systems. The energy requirements of the air-conditioning plant in the buildings were taken as the parameter for which various control paradigms were investigated in order to achieve the optimum method of utilising energy generated by photovoltaic systems installed on the buildings. The resources used in this investigation included hourly weather data obtained from the benchmark city and building data from the city scape. Generic and transient building energy simulation computer software tools, TRNSYS and DOE2 respectively, were used to estimate the energy utilisation of the buildings and to test the various control paradigms formulated. A solar resource estimation software program was developed in-house to estimate the available solar energy incident on the various surfaces of the buildings, and a control system simulation program, MATLAB Simulink, was used to test the performance of the proposed mounting system for the photovoltaic modules. The project focused on utilising the building integrated suntracking photovoltaic arrays as shading systems. It used a recursive parameter estimation method to predict the reference for controlling the position of the photovoltaic arrays and enable them to fulfil the dual purpose of generating electricity for the building and reducing the air-conditioning load by reducing the solar gains into the buildings through providing the shade for the windows. It also investigated the effect of utilising energy conservation measures such as designing buildings for natural ventilation and thermal massing. Finally an estimation of the reduction of the cost of air-conditioning system on one of the buildings due to shading was made so that the effect of this reduction on the cost of funding the installation of building-integrated PV can be investigated. It was generally concluded from this work that: i) utilising building integrated photovoltaic systems in the target market could lead to a significant contribution to its energy supply; ii) there were convincing reasons why using building integrated photovoltaic systems was a reasonable way to proceed in promoting the technology in the target area because the building market was the only market in the country which had the capital to adopt the systems in a commercial mode, and thus stimulate the interest of the local financial structures; iii) there is need to optimise the load in these buildings before photovoltaics can be effectively incorporated as the major source of energy iv) the acceptability of photovoltaics as the major source of energy differed among building types, but it was generally accepted that the more energy efficient buildings were the ones where photovoltaics could be the main if not the only source of energy; v) an integrated approach to future energy policies was the only way for a sustainable energy supply in the target market; vi) the strategy is applicable on a regional scale because of the geo-economical location of the benchmark city. This project investigated the technical viability of the building-integrated of photovoltaic systems in Zimbabwe. Further research on the topic requires demonstration systems of the proposed plants, and an in-depth economic analysis can be made from these

Publications of Goddard Space Flight Center, 1964. Volume I - Space sciences

This publication is a collection of articles, papers, talks, and reports generated by the scientific and engineering staff of Goddard Space Flight Center in the year 1964. Many of these articles were originally published in scientific or engineering Journals or as official NASA technical publications, while other are documents of a more informal nature. All are reprinted here as nearly verbatim as typography and format will permit. These articles are grouped into broad subject categories, but no detailed subdivision has been made. Within each category, the articles are arranged alphabetically by author. An overall author index is given in the back of the volume. The years 1963, 1964, and 1965 are being published as whole-year issues, and the resulting size dictates the use of two volumes; the first volume is titled Space Sciences, and the second Space Technology. It is anticipated, however, that future issues will be quarterly single volumes