F. Chegini, A. Foehly, N. Huynh, L. Pavarino, M. Potse, S. Scacchi, M. Weiser
coupled2023.
Abstract
The cardiac extracellular-membrane-intracellular (EMI) model enables the precise geometrical representation and resolution of aggregates of individual myocytes. As a result, it not only yields more accurate simulations of cardiac excitation compared to homogenized models but also presents the challenge of solving much larger problems. In this paper, we introduce recent advancements in three key areas: (i) the creation of artificial, yet realistic grids, (ii) efficient higher-order time stepping achieved by combining low-overhead spatial adaptivity on the algebraic level with progressive spectral deferred correction methods, and (iii) substructuring domain decomposition preconditioners tailored to address the complexities of heterogeneous problem structures. The efficiency gains of these proposed methods are demonstrated through numerical results on cardiac meshes of different sizes.
Abstract The cardiac extracellular-membrane-intracellular (EMI) model enables the precise geometrical representation and resolution of aggregates of individual myocytes. As a result, [...]
G. Generini, I. Rafanellí, A. Andreini, M. Dozzini, A. Milani, M. Bigi
coupled2023.
Abstract
To achieve a higher energy conversion efficiency, the use of supercritical CO2 (sCO2) in closed-loop Brayton and Rankine cycles has become relevant in the last decades due to an increased interest in its properties. sCO2 allows a more efficient heat transfer, chemical stability, non-flammability, and greater system efficiency. The necessity of a sealing system, which creates a barrier between the high-pressure fluid in the turbine and compressor and low-pressure regions, became essential for high-efficiency preservation and plant emissions reduction. In this regard, Dry Gas Seals (DGS) become one of the substantial components for sCO2 turbomachinery design due to lower leakage and higher efficiency than a traditional labyrinth radial seal. The high fluid pressure and density, connected to a small size sealing clearance and a high rotational speed, results in a significant friction heat, which characterizes the domain temperature distribution. The necessity for a thermal analysis of the domain becomes compelling to respect the maximum temperatures allowed in the turbomachine. When drawing up a thermal analysis, the high computational costs of a 3D simulation of the fluid domain (CFD) could be unfavourable due to the different orders of magnitude of secondary flows cavity sizes and DGS seals gaps, and the necessity to run a high number of simulations to define a geometrical sensitivity and optimization of crucial zones. A segregated conjugate heat transfer (CHT) iterative procedure has been implemented, relating a commercial 1D fluid modeller (Altair Flow Simulator) and a commercial finite element solver (Ansys Mechanical). To assess the procedure developed, 3D CFD simulations and CHT analysis of specific critical areas of the domain have been carried out. The segregated approach, implemented within the European project CO2OLHEAT, showed results in line with 3D CFD and CHT analysis, reducing computational time and cost.
Abstract To achieve a higher energy conversion efficiency, the use of supercritical CO2 (sCO2) in closed-loop Brayton and Rankine cycles has become relevant in the last decades due [...]
Biogas production has the potential to provide three benefits for green energy, waste management, and bio-fertilizers. The process involves converting organic waste materials, such as agricultural waste and food scraps, into methane-rich biogas through anaerobic digestion. This biogas can then be used to generate electricity and heat, reducing the reliance on fossil fuels. Additionally, the waste materials are broken down, reducing the amount of waste in landfills, and the process produces nutrient-rich fertilizer for crops. In summary, biogas production can play a significant role in creating a sustainable future. In recent decades, membrane materials have been used and improved to become a proven solution for covering the roof of anaerobic digesters. Coated textiles, with advanced technical properties such as good gas barrier properties, flexibility, and durability, are ideal for this application. The aim of this paper is to provide the reader with a clear understanding of biogas production and the focus on the impact of some plasticizers which can be used for the development of a gas membrane in anaerobic digesters.
Abstract Biogas production has the potential to provide three benefits for green energy, waste management, and bio-fertilizers. The process involves converting organic waste materials, [...]
V. Orlandini, R. Paciorri, A. Assonitis, F. Saltari, F. Mastroddi, A. Bonfiglioli
membranes2023.
Abstract
This paper describes a recently developed numerical technique to simulate high-speed flows on complex 3D inflatable structures using tetrahedral volume grids. In detail, the proposed methodology is based on the front-tracking approach, as it involves the coupling between a shock-fitting technique and a non-linear structural solver: by doing so, we are able to exploit the well-known advantages of shock-fitting regarding the computation and modelling of gas-dynamic discontinuities to deal with fluid-structure interaction problems. More details about the proposed technique and some applications to inflatable structures in hypersonic flows are presented in this paper
Abstract This paper describes a recently developed numerical technique to simulate high-speed flows on complex 3D inflatable structures using tetrahedral volume grids. In detail, the [...]
Colección de pruebas Jesús Sánchez 
Efficient numerical methods for simulating cardiac electrophysiology with cellular resolution 
491New York Institute of Technology
