3,134 research outputs found

    COMGEN-BEM: Boundary element model generation for composite materials micromechanical analysis

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    Composite Model Generation-Boundary Element Method (COMGEN-BEM) is a program developed in PATRAN command language (PCL) which generates boundary element models of continuous fiber composites at the micromechanical (constituent) scale. Based on the entry of a few simple parameters such as fiber volume fraction and fiber diameter, the model geometry and boundary element model are generated. In addition, various mesh densities, material properties, fiber orientation angles, loads, and boundary conditions can be specified. The generated model can then be translated to a format consistent with a boundary element analysis code such as BEST-CMS

    Sustainable Software Ecosystems: Software Engineers, Domain Scientists, and Engineers Collaborating for Science

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    The development of scientific software is often a partnership between domain scientists and scientific software engineers. It is especially important to embrace these collaborations when developing advanced scientific software, where sustainability, reproducibility, and extensibility are important. In the ideal case, as discussed in this manuscript, this brings together teams composed of the world's foremost scientific experts in a given field with seasoned software developers experienced in forming highly collaborative teams working on software to further scientific research.Comment: 4 pages, submission for WSSSPE

    Thermoelectric waste heat recovery in automobile exhaust systems: Topological studies and performance analysis

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    The demand for improved fuel efficiency in automobiles has placed an emphasis on exhaust system waste heat recovery as a 40% of the fuel\u27s chemical energy is lost to the environment in modern spark ignition engines. To advance fuel economy, researchers are currently evaluating technologies to exploit exhaust stream thermal power using thermoelectric generators (TEGs) that operate using the Seebeck effect. Thermoelectric generators have the potential to recover some of this waste energy in the exhaust stream potentially improving fuel economy by as much as 5%. ^ Attempts are made to maximize the electrical power generation by optimizing the thermoelectric generator geometry for a prescribed volume. A plate-fin heat exchanger configuration is assumed and consideration is given to pressure drops associated with the fins placed in the exhaust flow path; and the cross-sectional changes across thermoelectric generator inlet-exit ports. Multiple filled skutterudites based thermoelectric modules are employed in the higher temperature regions and Bismuth Telluride modules are used at lower temperature regions of the device. Power is optimized for rectangular configurations featuring longitudinal and transverse flow through the device and for hexagonal and cylindrical topologies as well. Optimal designs that maximize power output for fixed volume and number of thermoelectric elements are obtained for all configurations. In general, the rectangular configuration with transverse flow has the best overall performance. ^ System modeling of thermoelectric (TE) components is performed to maximize thermoelectric power generation. One-dimensional heat flux and temperature variations across thermoelectric legs have been solved using iterative numerical approach as a tool to optimize both TE module and TEG designs. Design trades are explored assuming the use of skutterudite as thermoelectric material that has potential for application to automotive applications where exhaust gas and heat exchanger temperatures typically vary from 100°C to 600°C. Dependencies of parameters such as leg geometry, fill fractions, electric current, thermal boundary conditions, etc., on leg efficiency, thermal fluxes and electric power generation have been studied in detail. Optimal leg geometries are computed for various automotive exhaust conditions. ^ Axial conduction in the wall liner is further modeled numerically and its impact on temperature distribution in gas stream, wall liner, and temperature difference across thermoelectric junctions are presented. The developed model is simulated to establish TEG output sensitivity to liner materials and thicknesses for both zero and non-zero axial conduction cases. Further, the axial conduction sensitivity to inlet conditions is considered and the effect on TEG output statistics are presented

    Stereotomy, Sustainable Construction and Didactics. Case study: a new Museum for Matera, European Capital of Culture 2019

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    The paper describes the students’ works, which included posters and physical models, were the partial outcomes of the current 3rd year design studio, led by Prof Giuseppe Fallacara and taught with the support of Maurizio Barberio and Micaela Colella, both Ph.D. students at the Polytechnic of Bari. The text illustrate an experimental teaching/learning approach which Giuseppe tested during the design studio. This approach was inspired by the concepts of ‘Experiential Learning’ and ‘Flipped Classroom’, consisting in a series of “cooperative classes”, where tutors and students interacted and discussed in an absolute spirit of intellectual equality. The goal was to simulate the activity of a large architecture practice, involved in the design of a public building, which generally requires the contribution of a large number of architects and designers. The students were given a brief for a new museum and multipurpose centre in Matera, Italy, which was recently nominated European Capital of Culture 2019. They had to deliver a design proposal, a rapid prototyped model and a short video

    Direct Cooled Ceramic Substrate for Thermal Control of Automotive Power Electronics

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    As electric vehicle technology develops, manufacturers would like to move toward hotter coolants for power electronic components to reduce system level costs. Thus, unique designs of inverter designs were sought to enable operation with 105°C coolant. The proposed solution in this research incorporated flow channels into the ceramic layer of the direct-bonded copper substrate typically found in power electronic packages. The focus of this research details the design and analysis of the direct cooled ceramic substrate from the perspective of its thermal performance and innovative packaging concept. The research was directed to pursue alumina as the substrate ceramic because of its low cost. Alumina, which has the lowest thermal conductivity among four materials considered, requires a larger substrate cross-sectional area to result in a viable design. Based on preliminary model parameters, two flow channel designs with larger alumina substrates were shown to meet the design goals. Experiments were conducted to characterize the pressure drop across metal foam inserts which were used to enhance the heat transfer in the flow channels. Other experiments were conducted to validate the thermal performance and model configuration. The results of thermal validation experiment showed that the assumed effective thermal conductivity of the metal foam – fluid matrix was too large. The small contact area between the metal foam inserts and ceramic substrate reduces the effective thermal conductivity. Based on the data reduction method, the model parameters were modified to produce temperature distributions that better reflected the experimental data. Simulations were updated with the modified model parameters. These models showed that the cross-sectional area of the alumina substrate had to increase further in order to adequately manage the heat load. In parallel efforts, the overall inverter package was considered. A linear manifold package resulted in the highest power density. Technical review of the inverter package raised concerns about stray inductance. Incorporating the entire inverter leg on one substrate would alleviate these losses. Future research can use the parameters determined in this work to more confidently predict the performance of direct cooled ceramic substrate designs

    Numerical study of high temperature heat exchanger and decomposer for hydrogen production

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    This dissertation deals with three-dimensional computational modeling of a high temperature heat exchanger and decomposer for hydrogen production based on sulfur-iodine thermochemical water splitting cycle, a candidate cycle in the U.S. Department of Energy Nuclear Hydrogen Initiative. The conceptual design of the shell and plate decomposer is developed by Ceramatec, Inc. The hot helium from a nuclear reactor (T=975°C) is used to heat the SI (sulfuric acid) feed components (H2O, H2SO4 , SO3) to get appropriate conditions for the SI decomposition reaction (T\u3e850°C). The inner wall of the SI decomposition part of the decomposer is coated by a catalyst for chemical decomposition of sulfur trioxide into sulfur dioxide and oxygen. The proposed material of the heat exchanger and decomposer is silicon carbide (SiC); According to the literature review, there is no detailed information in available publications concerning the use of this type of decomposer in the sulfur-iodine thermochemical water splitting cycle. There is an urgent need for developing models to provide this information for industry. In the present study, the detailed three-dimensional analysis on fluid flow, heat transfer and chemical reaction of the decomposer have been completed. The computational model was validated by comparisons with experimental and calculation results from other researchers; Several new designs of the decomposer plates have been proposed and evaluated to improve the uniformity of fluid flow distribution in the decomposer. To enhance the thermal efficiency of the decomposer, several alternative geometries of the internal channels such as ribbed ground channels, hexagonal channels, and diamond-shaped channels are proposed and examined. It was found that it is possible to increase the thermal efficiency of the decomposer from 89.5% (baseline design) up to 95.9% (diamond-shaped channel design); The calculated molar sulfur trioxide decomposition percentage for the baseline design is 64%. The percentage can be increased significantly by reducing reactants mass flow rate and with increasing channel length and operation pressure. The highest decomposition percentage (∌80%) for the alternative designs was obtained in the diamond-shaped channels case; The sulfur dioxide production (throughput) increases as the total mass flow rate of reacting flow increases, regardless of the fact that the decomposition percentage of sulfuric trioxide decreases as total mass flow rate of reacting flow increases

    Möbius Geometry and Cyclidic Nets: A Framework for Complex Shape Generation

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    International audienceFree-form architecture challenges architects, engineers and builders. The geometrical rationalization of complex structures requires sophisticated tools. To this day, two frameworks are commonly used: NURBS modeling and mesh-based approaches. The authors propose an alternative modeling framework called generalized cyclidic nets that automatically yields optimal geometrical properties for the façade and the structure. This framework uses a base circular mesh and Dupin cyclides, which are natural objects of the geometry of circles in space, also known as Möbius geometry. This paper illustrates how new shapes can be generated from generalized cyclidic nets. Finally, it is demonstrated that this framework gives a simple method to generate curved-creases on free-forms. These findings open new perspectives for structural design of complex shells

    Mesh generation for voxel -based objects

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    A new physically-based approach to unstructured mesh generation via Monte-Carlo simulation is proposed. Geometrical objects to be meshed are represented by systems of interacting particles with a given interaction potential. A new way of distributing nodes in complex domains is proposed based on a concept of dynamic equilibrium ensemble, which represents a liquid state of matter. The algorithm is simple, numerically stable and produces uniform node distributions in domains of complex geometries and different dimensions. Well-shaped triangles or tetrahedra can be created by connecting a set of uniformly-spaced nodes. The proposed method has many advantages and potential applications.;The new method is applied to the problem of meshing of voxel-based objects. By customizing system potential energy function to reflect surface features, particles can be distributed into desired locations, such as sharp corners and edges. Feature-preserved surface mesh can then be constructed by connecting the node set.;A heuristic algorithm using an advancing front approach is proposed to generate triangulated surface meshes on voxel-based objects. The resultant surface meshes do not inherit the anisotropy of the underlying hexagonal grid. However, the important surface features, such as edges and corners may not be preserved in the mesh.;To overcome this problem, surface features such as edges, corners need to be detected. A new approach of edge capturing is proposed and demonstrated. The approach is based on a Laplace solver with incomplete Jacobi iterations, and as such is very simple and efficient. This edge capturing approach combined with the mesh generation methods above forms a simple and robust technique of unstructured mesh generation on voxel-based objects.;A graphical user interface (GUI) capable of complex geometric design and remote simulation control was implemented. The GUI was used in simulations of large fuel-cell stacks. It enables one to setup, run and monitor simulations remotely through secure shell (SSH2) connections. A voxel-based 3D geometrical modeling module is built along with the GUI. The flexibility of voxel-based geometry representation enables one to use this technique for both geometric design and visualization of volume data
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