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Item Homogenization-based modeling of ionic transport in weakly piezoelectric porous media(2026) Camprová Turjanicová, Jana; Rohan, EduardThis paper presents a new homogenized model of two-component electrolyte transport through a weakly piezoelectric porous medium. The model relevant to the microscopic scale describes quasi-stationary states of the medium while reflecting essential physical phenomena, such as electrochemical interactions in a dilute Newtonian solvent under assumptions of slow flow. The dimensional analysis of the mathematical model introduces scaling of the viscosity, electric permittivity, piezoelectric coupling, and dielectric tensor. The micromodel is linearized around the reference state represented by the thermodynamic equilibrium and further upscaled through the asymptotic homogenization method. Due to the scaling of parameters, the derived limit model retains the characteristic length associated with the pore size and the electric double-layer thickness. The upscaling procedure gives a fully coupled macroscopic model describing the electrolyte flow in terms of the global pressure and streaming potentials of the two ionic species in the weakly piezoelectric matrix. By virtue of the characteristic responses, quantities of interest are reconstructed at the microscopic scale using the resolved macroscopic fields. The coupling between electrochemical and mechanical phenomena influenced by the skeleton piezoelectricity is illustrated using numerical examples. The model, which was motivated by the cortical bone porous tissue, is widely applicable in designing new biomaterials involving piezoelectric stimulation.
Item Self-induced non-synchronous resonance phenomena and stability in reduced aero-elastic system(2024) Byrtus, Miroslav; Dyk, ŠtěpánThe paper is aimed at the parametric dynamic analysis of the two degrees of freedom (DoF) phenomenological model of aero-elastic interaction between a friction-damped flexible mounted body and a flowing fluid. A coupled system of a linear structure oscillator and the van der Pol based wake oscillator is introduced. Firstly, the complex eigenvalue problem is used for the comprehensive analysis of frequency lock-in, veering and crossing areas from the structural mode stability point of view. Further, an in-depth analysis of the fully nonlinear model based on the numerical continuation method is presented. The analysis focuses on non-synchronous vibration in the resonance areas. Attention is paid to the investigation of transition mechanisms to frequency lock-in and frequency veering in the structural response. In experimental studies, the amplitude and frequency jumps are observed. Here, we show that the origin of these jump phenomena results from the mutual coexistence of two stable solutions, which form a hysteresis region, which can be found in experimentally gained data. Moreover, the influence of structure friction-damping on nonlinear response is evaluated. The proposed phenomenological model is validated concerning two different experimental-based investigations.Item Transient response of non-prismatic heterogeneous viscoelastic rods and identification of their material properties(2024) Šulda, Jakub; Adámek, Vítězslav; Kroft, RomanPulse propagation in homogeneous and heterogeneous viscoelastic thin rods of a constant or variable cross-section is investigated in this work using analytical, numerical and experimental methods. Based on the elementary theory of thin rods, the model for pulse propagation in a layered non-prismatic rod is derived and solved in the Laplace domain. Using the numerical inverse Laplace transform, semi-analytical transient solutions for both homogeneous, layered and functionally graded viscoelastic prismatic or non-prismatic rods are obtained. The parameters of the generalised Zener model (GZM) are then identified by solving the problem of parametric optimisation in Matlab and utilising the transient acceleration responses measured for rods of different types and different material properties (POM-C, PC1000, PP, PVC, PET, PLA and aluminium). A great agreement between the measured signals and the responses calculated for GZM with different numbers of relaxation times was achieved. Next, the dynamic properties of selected prismatic and non-prismatic rods have been studied. The dispersion and attenuation curves for both homogeneous and layered rods are reconstructed from the measured signal using a method adopted from the literature. The obtained results are then discussed in the context of the theoretical curves resulted from the elementary rod theory and from the theory that takes into account the lateral motions of the rod.Item A new polyhedral sonic crystal for broadband sound barriers: Optimization and experimental study(2024) Tajsham, Alireza; Younesian, Davood; Goodini, Javad; Hosseinkhani, AliIn this research, a new polyhedral geometry for a 2D unit-cell with ultrawide frequency bandgaps is proposed. The genetic algorithm is combined with the finite element (FE) model to obtain an optimal geometry of the unit-cell based on the two objective functions: (i) the largest bandgap within 0–1500 Hz and (ii) the largest bandgap summation in the range of 0–6000 Hz. Frequency analysis is conducted for the optimized geometries to illustrate the performance of the sonic crystal for the noise attenuation in bandgap frequencies. In order to validate the numerical results, an experimental test for a 3D model is designed and implemented. It is shown that a strong correlation is observed between the results from the bandgap diagram, frequency analysis, and experimental measurements. The proposed design presents a fractional bandwidth (FB) of 80.69 % and a bandgap coverage factor (BGCF) of 179.01 % in the applied frequency range, which are remarkable results in terms of bandgap indexes compared to the available literature of sonic crystals. The proposed design for unit-cell represents highly promising properties as a candidate for the noise control applications at both low and high-frequency ranges.Item Hybrid steel–composite cross-arm for distribution power lines(Elsevier, 2023) Zemčík, Hana; Kroupa, Tomáš; Vaňková, Tereza; Zemčík, Robert; Pihera, Josef; Prosr, Pavel; Kadlec, Petr; Šroubová, Lenka; Müllerová, Eva; Martínek, Petr; Pavlica, Richard; Komárek, Josef; Friedl, Jan; Polanský, RadekItem A sequential global programming approach for two-scale optimization of homogenized multiphysics problems with application to Biot porous media(Springer, 2023) Vu, Bich Ngoc; Lukeš, Vladimír; Stingl, Michael; Rohan, Eduard
Item Homogenization of the acoustic transmission on periodically perforated plates interacting with potential mean flow(Elsevier, 2024) Rohan, Eduard; Lukeš, VladimírItem New actuation planning method for the analysis and design of active tensegrity structures(Elsevier, 2023) Hrabačka, Martin; Bulín, Radek; Hajžman, MichalItem Homogenization and numerical algorithms for two-scale modeling of porous media with self-contact in micropores(Elsevier, 2023) Rohan, Eduard; Heczko, JanItem Neural-network-based fluid–structure interaction applied to vortex-induced vibration(Elsevier, 2023) Bublík, Ondřej; Heidler, Václav; Pecka, Aleš; Vimmr, JanIn this paper, a fluid–structure interaction (FSI) solver with neural-network-based fluid-flow prediction is proposed. This concept is applied to the problem of vortex-induced vibration of a cylinder. The majority of studies that are concerned with fluid-flow prediction using neural networks solve problems with fixed boundary. In this paper, a convolutional neural network (CNN) is used to predict unsteady incompressible laminar flow with moving boundary. A deformable non-Cartesian grid, which traces the boundary of the fluid domain, is used in this paper. The CNN is trained for oscillating cylinder with various frequencies and amplitudes. The dynamics of the elastically-mounted cylinder is modelled using a linear spring–mass–damper model and solved by an implicit differential scheme. The results show that the CNN-based FSI solver is capable of capturing the so-called lock-in phenomenon for the problem of vortex-induced vibration of a cylinder and the quantitative behaviour is similar to the results of the CFD-based FSI solver. Moreover, the CNN-based FSI solver is two orders of magnitude faster than the CFD-based FSI solver and the speedup is expected to be even greater on larger problems.Item Flow-Field Prediction in Periodic Domains Using a Convolution Neural Network with Hypernetwork Parametrization(World Scientific, 2023) Bublík, Ondřej; Heidler, Václav; Pecka, Aleš; Vimmr, JanItem Subcritical behaviour of short cylindrical journal bearings under periodic excitation(Springer, 2023) Rendl, Jan; Byrtus, Miroslav; Dyk, Štěpán; Smolík, LubošItem 3D projection of the LuGre friction model adapted to varying normal forces(Springer, 2022) Colantonio, Lorenzo; Dehombreux, Pierre; Hajžman, Michal; Verlinden, OlivierItem Comparison of implicit time-discretization schemes for hybridized discontinuous Galerkin methods(University of West Bohemia, 2022) Levý, Tomáš; May, GeorgItem Comparison of implicit time-discretization schemes for hybridized discontinuous Galerkin methods(University of West Bohemia, 2022) Levý, Tomáš; May, GeorgItem Impact point localization in three-dimensional structures using wavelet transform(Academic Press, 2022) Houdek, Václav; Smolík, Luboš; Kubín, ZdeněkItem Curvilinear element of the discontinuous Galerkin method designed to capture the labyrinth seal geometry exactly(University of West Bohemia, 2022) Bublík, Ondřej; Pecka, Aleš; Vimmr, JanItem Infračervená termografie ve facility managementu(Asociace technických diagnostiků, 2018) Pašek, JanFacility management je multidisciplinární obor zahrnující i péči o budovy a jejich provoz; tento obor v současné době prochází v ČR dynamickým rozvojem. V zemích západní Evropy a USA se ale již jedná o velmi rozvinutý obor s historií několika desítek let. Legislativa pro facility management v ČR je tak implementována z oblasti EN a ISO standardů. Přes jisté rozdíly v obou skupinách norem je společným znakem značná pozornost věnovaná zejména hodnocení kvality a výkonu poskytovaných služeb, sledování nákladů, analýzám a prezentování informací. Významným nástrojem, ale i důsledně sledovanou a hodnocenou službou bude infračervená termografie zaváděná rychlostí úměrnou rozvoji facility managementu v podmínkách ČR. Příspěvek informuje o pozici infračervené termografie ve facility managementu a o nárocích, resp. požadavcích, které budou její aplikace klást na techniky termodiagnostiky.Item Technický stav středověkých kamenných chrámů v Angkoru, 2. díl(INFORMAČNÍ CENTRUM ČKAIT, 2021) Pašek, JanArcheologický park Angkor je světově unikátním stavebním a archeologickým pracovištěm středověké Khmérské říše, zahrnuje stovky středověkých kamenných chrámových staveb. Český výzkumný tým CNPA (Czech National Project at Angkor) ve spolupráci s kambodžským Úřadem pro ochranu a správu Angkoru a regionu Siem Reap (APSARA Authority) zkoumá a hodnotí stav těchto památek i možnosti jejich záchrany. Druhý díl článku popisuje především jejich konstrukční chování, analyzuje jejich technický stav a důsledky sanačních intervencí.Item Technický stav středověkých kamenných chrámů v Angkoru, 1. díl(INFORMAČNÍ CENTRUM ČKAIT, 2021) Pašek, JanArcheologický park Angkor v Kambodži je světově unikátním stavebním a archeologickým pracovištěm. Zahrnuje stovky kamenných monumentů z období existence rozvinuté středověké khmérské říše, z nichž se velká většina nachází v různém stadiu rozpadu. Český výzkumný tým CNPA (Czech National Project at Angkor) se ve spolupráci s kambodžským Úřadem pro ochranu a správu Angkoru a regionu Siem Reap (APSARA Authority) zabývá zkoumáním a hodnocením jejich technického stavu i souborem vlivů působících na další porušování těchto světově unikátních středověkých památek a možnostmi jejich záchrany.
