Papers by Keyword: Computational Simulation

Abstract: Microfluidic systems are transforming chemical and biological research by enabling precise control and analysis of fluids on a microscale. This study presents the design and computational simulation of a microfluidic system for the in vitro maintenance of pancreatic islets, critical endocrine structures of the pancreas involved in glucose regulation. Three chamber geometries-ellipsoidal, hexagonal, and rectangular-were proposed, each combined with three irrigation patterns: periphery-to-center, pole-to-pole, and a hybrid model. A total of 18 design configurations were analyzed. The irrigation channels, with a diameter of 30 µm and a bifurcation angle of 43°, were designed to mimic physiological conditions, facilitating efficient nutrient exchange. Computational fluid dynamics (CFD) simulations using ANSYS Fluent demonstrated that most designs achieved a flow rate of 14.56 nL/s, closely matching theoretical values and meeting the physiological requirements of islets. Among the proposed models, the hexagonal chamber with peripheral irrigation (single-cell configuration) and the ellipsoidal chamber with periphery-to-center irrigation (dual-cell configuration) showed optimal performance, with stable laminar flow and minimal pressure drop. These results highlight the potential of this microfluidic system as an innovative tool for diabetes research, enabling the study of islet biology, drug testing, and disease modeling under controlled conditions. Future work will focus on experimental validation and optimization of the proposed designs.

Abstract: Implementation of high temperature solar reservoirs is associated with problems related to the physical properties of materials, especially with temperature resistance of the material at temperature changes, with high heat capacity, with high thermal conductivity and with material fire resistance. In the case of silicate materials, more specific materials with favourable physical properties are available, which can be used for the construction of high temperature containers. The basic prerequisite for designing such container is the knowledge of the physical properties of the heat storage core and the thermal insulation ability of container cladding layers.The paper deals with the problem of identification of material properties of silicates in the wide temperature range up to 800 °C, using the standard measurement methodology, improved by additional temperature recording at a defined distance from the thermal source during the dynamic thermal development of the linear thermal source, well-known as the hot wire method.

Abstract: The essence of real-time hybrid simulation (RTHS) is its ability to combine the benefits ofphysical testing with those of computational simulations. Therefore, an understanding of the real-timecomputational issues and challenges is important, especially for RTHS of large systems, in advancingthe state of the art. To this end, RTHS of a 40-story (plus 4 basement stories) tall building havingnonlinear energy dissipation devices for mitigation of multiple natural hazards, including earthquakeand wind events, were conducted at the NHERI Lehigh Experimental Facility. An efficient implementationprocedure of the recently proposed explicit modified KR-a (MKR-a) method was developedfor performing the RTHS. This paper discusses this implementation procedure and the real-time computationalissues and challenges with regard to this implementation procedure. Some results from theRTHS involving earthquake loading are presented to highlight the need for and application of RTHSin performance based design of tall buildings under earthquake hazard.

Abstract: The investigation of the hygrothermal behavior of advanced silica materials, which are today in ever increasing demand during the reconstruction of building envelopes, is an important point of research. For determining the moisture balance in building structures, the Glaser method is most frequently used to day which, however, considers during calculations water diffusion only in stationary state at simplified marginal conditions; it does not take into account the moisture transport in the capillary system of the material structure, nor the sorption properties of the material. The goal of the research is therefore to gain deeper knowledge of the way heat and moisture transport through the pore structure of these silica materials. The paper describes verification of efficacy of thermal insulation and rehabilitation silicate plastering. Based on experiences from previously research and their results were chosen 2 developed plasters for computational simulation of their behavior in the case of detail of window jamb. One type of developed plastering was placed from the site of interior and the second type of plastering was applied from the site of exterior.

Abstract: It is considered that fracture toughness of TRIP steel can be evaluated by means of the small punch (SP) test. However, a mechanism of improving fracture toughness in the SP test for TRIP steel under the impact condition might not be clarified through merely experimental works because the effect of strain-induced martensitic transformation (SIMT) coupled with temperature in TRIP steel becomes quite complicated at high deformation rate. Therefore, a computational simulation on the SP test for an evaluation of the mechanism is indispensable. Since the specimen in the SP test will be fractured at a certain level of deformation, it is necessary to express the fracture by incorporating damage model into constitutive equation of the material in simulation of the SP test. In the present study, a finite element analysis is performed for the SP test with a specimen made of type-304 austenitic stainless steel by an inclusion of damage parameter and its evolution equation. After showing the validity of the computation, the effects of deformation rate, temperature, and SIMT on the force-deflection curve and deformation behavior are examined. Then, the mechanism of rate-sensitive fracture toughness in TRIP steel is challenged to be clarified.

Abstract: In search of new technologies for the iron ore sintering process, the re-circulation of waste gases in the process can provide some advantages in relation to the conventional process. For such study, a sintering multi-phase model was used for the assessment of the re-circulation of waste gases in the process. Five cases of re-circulation of waste gases in the sintering process were analyzed, always aiming at a stable operation in the process. The results of the simulation indicate an enlargement of the combustion front with the re-circulation of the waste gases and the possibility of existing a reduction of the solid fuel consumption. As a result, there was an increase of the calcium-silicate fraction, providing a sinter reducibility improvement, apart from the reduction of the emission of CO₂ and PCDD/Fs in the sinter machine.

Abstract: High-temperature behaviour of refractory composites needs proper experimental and theoretical analysis, coming from classical thermodynamics. The dependence of usual thermal characteristics, as the thermal conductivity and thermal capacity, on temperature, cannot be neglected in any computational simulation, thus the experimental identification of their effective values is required. Whereas valid technical standards related to the hot-wire measurement technique enables us only certain approximate evaluation of thermal diffusivity, the very similar experimental configuration, supplied by the more advanced physical, mathematical and computational analysis, offers a possibility of reliable simultaneous identification of more characteristics. The crucial application is to the selection of appropriate silicate materials for the design of high-temperature storage of solar energy where both high thermal conductivity and thermal capacity are required. The first results refer to certain magnesite-based products as the good choice.

Abstract: The possibility to use the computational modeling as replacement of the natural dynamic testing of mechanical equipment is considered. A useful program tool is selected, initial data are prepared and the set of computational experiments to determine the dynamic and strength characteristics of the engine are performed. To verify the results of computational simulation of mentioned characteristics the data of the engine mechanical testing were used, and satisfactory correspondence was achieved. This investigation showed the dynamic and strength characteristics of the considered engine are complied with the basic regulatory requirements.

Abstract: The material defects in automobile industry caused by correction can be found in different components, such as welded and fastened areas in cars and vehicles. The corrosion appears when components with different conducting properties assembled together in electrolyte substances. Different conducted materials show different potentials which will lead corrosion. The corrosion in components can cause many product problems, such as bad quality, less safety, lower energy efficiency, and higher cost. This paper analyzes the rusty mechanism and anti-corrode in regular coating and nanocoating materials via computer-aided simulation and prototype testing. Both computational simulation and sample testing displayed almost equal results that validate the credibility of analytic method proposed in this paper. Keywords: Nanocoating technology, computational simulation, corrosion control, anti-corrosion, computer-aided modeling

Abstract: New finite element homogenization model with nonaffine constitutive equation of rubber is developed to study the deformation behavior of silica-filled rubber under monotonic and cyclic deformation. The obtained results clarified the effect of the volume fraction of the silica coupling agent and the networklike structure connecting the silica particles on essential physical enhancement mechanisms of deformation resistance and hysteresis loss for silica-filled rubber. The finding suggests that the material characteristics of silica-filled rubber are much more controllable than those of carbon-black-filled rubber.