Conference Papers (KME)
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Item Towards an agreement between the numerical simulations and the experimental data obtained in a transonic linear turbine blade cascade for flutter testing(MATEC Web of Conferences, 2025) Tsymbalyuk, Volodymyr; Eret, Petr; Sláma, Václav; Hron, David; Peterka, Tomáš; Macálka, Aleš; Ira, JiříThe paper reports on the progress in the agreement between the results of numerical simulations and the experimental data obtained in a transonic linear turbine blade cascade for flutter testing. The outcomes show that previously omitted details in CFD geometry have a detrimental impact on the results, and their implementation reduces the difference between the two approaches tested. In detail, small gaps between the wind tunnel wall and the blades are introduced in the numerical model according to the experimental setup. Experimentally evaluated and computed aerostatic and aerodynamic forces and moments are compared. The findings show reasonable agreement and suggest promising advances in numerical data validation.
Item Transitions to chaos of kinematically excited bistable magnetic pendulum(Institute of Thermomechanics of the CAS, v.v.i Prague, 2024) Byrtus, Miroslav; Smolík, LubošThe paper investigates the dynamic behaviour of a bistable system which is represented by a magnetic pendulum fixed to a moving plate. Bistable systems are often employed in energy harvesting or vibration attenuation issues because of their broad-band high-amplitude response. Here, the transitions to chaotic response are investigated both numerically and experimentally.Item Effective piezoelecric behaviour due to flexoelectric microstructure - homogenization based modelling(University of West Bohemia, 2024) Rohan, EduardThe flexoelectricity is a property of all dielectric materials, occurring in both centrosymmetric and asymmetric crystals when strain gradient is generated. Conversely, also a "hyperstress" is generated due to gradient of electric field, contributing to the material stiffness. Both these direct and reverse effects appear at small scales, rather then at the ``macrolevel''. The aim of the present study is to explore behaviour of weakly flexoelectric periodically heterogeneous materials. For this, the asymptotic homogenization method is employed. We consider piezoelectric or dielectric materials with a weak flexoelectric property, constituting the skeleton of general periodic porous structures which enable to generate the strain gradients. Using the asymptotic homogenization, it is shown that effective behaviour of such materials is piezoelectric, whereby the homogenized piezoelectric coefficients are computed using the characteristic responses of the flexoelectric microstructure. Analytic result is derived for a 1D periodic rods designing a porous structure.Item Exploration of workspace of active tensegrity structures using actuation planning process(The Korean Society of Mechanical Engineers, 2024) Hrabačka, Martin; Bulín, Radek; Hajžman, Michal; Rendl, Jan; Polach, PavelThis paper focuses on creating a methodology for workspace exploration of tensegrity manipulators consisting of stiff struts in compression and compliant cables in tension. The actuation of the structure is done via changing rest lengths of cables. The work includes an introduction to tensegrity structures, an explanation of the methodology for workspace exploration, and an illustration of the procedure on the example structure.Item Trajectory planning and control of manipulators based on tensegrity structures with manipulability and modal properties optimization(University of West Bohemia, 2024) Halamka, Vojtěch; Hrabačka, Martin; Zavřel, Jan; Beneš, Petr; Hajžman, Michal; Šika, ZbyněkThis paper presents a control methodology for robots based on tensegrity structures with redundant actuators. This methodology is divided into two tasks: trajectory planning and shape control. The basis of the trajectory planning is the workspace exploration using the Dynamic Relaxation method, followed by the interpolation and key manipulator properties optimization of the rod angles and the cable forces with respect to the desired end-effector trajectory. The Computed Torque Control method extended with Singular Value Decomposition is used for the shape control. The methodology is demonstrated on a virtual prototype of planar manipulator. The values of the tracking errors of the end-effector trajectory confirm its functionality.Item Numerical simulations of pantograph and catenary interaction considering imperfect joints(The Korean Society of Mechanical Engineers, 2024) Hajžman, Michal; Bulín, Radek; Hrabačka, Martin; Smolík, Luboš; Byrtus, MiroslavCatenary systems, utilized in the railway industry for transmitting electrical energy to a vehicle, consist of support poles and wires. Resolving dynamic issues related to the interaction between a pantograph and catenary systems poses another challenge. Key aspects involve a moving load on the contact wire due to the pantograph and nonlinearities arising because droppers can transmit force only under tension.The introduction of imperfect joints in the pantograph of an electric rail vehicle introduces a significant challenge in accurately modelling its behaviour. Imperfect joints can result in non-ideal connections, leading to deviations from the expected motion and performance. To address this issue, a comprehensive approach utilizing a multibody dynamics methodology was employed.Item Software development for a multibody pantograph model and FEM catenary system(University of West Bohemia, 2024) Hrabačka, Martin; Hajžman, Michal; Bulín, Radek; Smolík, LubošThis work deals with the implementation of software simulating the dynamics of a moving pantograph interacting with the catenary system. Catenary systems, utilized in the railway industry for transmitting electrical energy to a vehicle, consist of support poles and wires, and they are modeled by FEM. On the other hand, a multibody approach is used to model pantographs, which consist of several rods and other bodies interconnected by joints. Together, solving the dynamics of this complex mechanical system represents a very interesting task, including several nonlinear features such as friction and clearances in pantograph joints or one-sided forces generated in catenary wires. Through advanced computational techniques, it is possible to predict how imperfections in joints influence the overall performance of the pantograph during its interaction with the catenary system. This simulation approach allows engineers to gain insights into potential issues, optimize the design, and enhance the reliability and efficiency of the electric rail vehicle.Item Friction identification and active elimination on multi-DoF mechanism(University of West Bohemia, 2024) Šika, Zbyněk; Kraus, K.; Hajžman, Michal; Bulín, RadekThe paper deals with the newly improved symmetrical version of the active absorber demonstrator that was built and identified. Using voice-coil actuators in legs, various force inputs have been fed into the absorber demonstrator, such as chirps, steps or white noise signals. The dynamic behaviour of the new demonstrator is significantly better than theoriginal one. Passive resistances are significantly reduced and the incidence of hard-to-predict stick-slip effects is much lower.Item Reduced-order modelling of blood flow in the human arterial tree(Západočeská univerzita v Plzni, 2025) Augustiňák, TomášHaemodynamics is recognised to affect the pathogenesis of the most life-threatening cardiovascular diseases, such as heart attack or brain stroke. Thus, in the new millennium, the need to better understand the complexity and uniqueness associated with pulsatile blood flow in compliant arteries has given rise to mathematical models of different spatial dimensions, making it possible to obtain accurate patient-specific results at low computational cost. The work presents a well-known model of the arterial system consisting of 55 largest arteries in the human body. The model, which is solved by the MacCormack finite volume method, comprises of individual compliant arterial segments formulated as one-dimensional models.Item Complex simulation procedure to predict flutter of steam turbine rotor blades(University of West Bohemia, Univerzitní 8, 301 00 Plze¬, Czech Republic, IC 49777513, 2023) Sláma, V.; Hron, David; Macálka, A.The need for robust numerical tools to predict the flutter of rotor blades is a crucial aspect of the aeromechanical design of new modern last-stage blades for steam turbines. Therefore, a reliable flutter calculation procedure has been developed and validated in Doosan Skoda Power. As a result, a unique and powerful tool FLTR was developed. It also automates the generation of transient input files and the evaluation described in this paper.Item On the friction modelling in joints of multibody systems(Institute of Thermomechanics v. v. i., 2025) Hajžman, Michal; Bulín, Radek; Hrabačka, Martin; Rendl, JanThe paper focuses on approaches to friction modelling and its integration into numerical simulations of multibody systems. The study considers rigid bodies connected by kinematic constraints. A summary of the various formulations of equations of motion, including kinematic constraints, is provided. Friction is incorporated into the equations of motion through forces and torques, with normal contact forces in joints used to evaluate friction forces. The paper addresses both static and dynamic friction models. The practical implementation of these models, based on Lagrange multipliers, is discussed, and an illustrative example of basic dynamic analyses is discussed.
Item Modelovánı́ chemických procesů v kardiovaskulárnı́ biomechanice(Západočeská univerzita v Plzni, 2025) Pekár, Šimon; Jonášová, Alena; Vimmr, JanHlavnı́ přı́činou akutnı́ch a často život ohrožujı́cı́ch stavů u kardiovaskulárnı́ch chorob (např. infarkt myokardu a mozková mrtvice) bývá vznik krevnı́ch sraženin uvnitř cévy. Pro lepšı́ pochopenı́ faktorů spjatých s touto patologiı́, která probı́há jak na biologické, tak biochemické úrovni a je navı́c vystavena účinkům protékajı́cı́ krve, je vhodné využı́t nástrojů matematického modelovánı́ – konkrétně makroskopický popis založený na konvekčně-difúzně-reakčnı́ch (CDR) rovnicı́ch popisujı́cı́ch časoprostorový vývoj koncentrace látek v proudı́cı́m médiu. V rámci této práce byl jednak uchopen jeden ze základnı́ch modelů chemické interakce, na němž lze dobře ilustrovat úskalı́ spojená s řešenı́m tohoto typu rovnic, a jednak výchozı́ model sráženı́ krve, který tvořı́ základ tzv. koagulačnı́ kaskády.Item Zjednodušené dynamické modely v optimalizaci vypružení(VTS pri Žilinskej univerzite v Žiline, 2023) Byrtus, Miroslav; Červenka, ZdeněkPříspěvek se zabývá praktickým použitím 2-hmotových tlumených dynamických modelů v optimalizaci návrhu vypružení kolejového vozidla. Příspěvek srovnává dvě klasické optimalizační metody popsané v odborné literatuře: A) metoda minimalizace rozptylu zrychlení a B) metoda minimalizace frekvenčního přenosu. Příspěvek dále uvádí simulaci jízdy 2-hmotového tlumeného modelu na reálných nerovnostech s vyhodnocením ukazatele pohodlí Nmv dle EN 12299. Na závěr příspěvek uvádí srovnání více typů kolejových vozidel na zjednodušených dynamických modelech.Item Acoustic streaming in porous media – homogenization based two-scale modelling(IOP Publishing Ltd, 2024) Rohan, Eduard; Moravcová, FannyA homogenized model of the acoustic streaming (AS) in rigid porous periodic structure is presented. Using the classical perturbation approach, the first and the second order subproblems arising from the N-S equations governing the fluid dynamics in the pores are obtained and further homogenized. The driving force of the permanent flow is obtained due to the time average of the nonlinear advection terms expressed using the first order acoustic harmonic fluctuations. Homogenization of the 1st order problem yields the dynamic Darcy flow mode governing the wave response. This is employed to constitute the streaming source term involved in the 2nd order homogenized problem for time-averaged pressure field. The AS can be observed at both the macroscopic and the microscopic levels. While the acoustics-driven microflows are observed for any microstructure, the macroscopic AS depends on the porous microstructure geometry and boundary conditions. We propose a solution method based on the spectral analysis of the characteristic microscopic dynamic Stokes flow. The AS phenomenon in the homogenized medium is illustrated using 2D examples of periodic porous microstructures.Item Derivatives of quaternion spline interpolation function for multibody dynamics(IDMEC - Instituto de engenharia Mecanica, 2023) Houdek, Václav; Verlinden, Olivier; Hajžman, MichalInterpolation plays an important role in nowadays world. By interpolating data, we save time and money in general. The main areas where interpolation is applied are robotics, automotive, medicine and biology. One of the possible basis splines for interpolation are B-splines, which are also used in Computer Aided Geometric Design (CAGD) due to their smoothness and locality properties. In the extended abstract, we consider problems of kinematics, which are, in many cases, characterized by a set of non-linear algebraic equations that have to be assembled and solved at each time step. The computational procedure could be time-consuming; therefore it is reasonable to develop suitable methods to overcome such difficulties. Moreover, the parametrization of finite rotations is an essential issue in multi-body kinematics and dynamics and therefore the concept of quaternions is employed to describe body rotations in this work. In other words, the main idea is to solve the kinematics prior to the dynamics, pre-compute the rotation parameters of a car wheel support, and then use the interpolation of rotations in the framework of more complex computational tasks. The pre-computation of the rotation parameters leads to a look-up table.Item A preliminary in silico study of flow-mediated thrombosis in medical devices(Springer, 2024) Jonášová, Alena; Plánička, Stanislav; Vimmr, JanFailure of blood-contacting medical devices, such as vascular grafts and stents, is often attributed to thrombosis-related complications. To provide an alternative insight into the often very complex interaction between the forming clot and blood flow, the study introduces a continuum-based computational model based on a two-way coupled modelling approach. The basis of the model is formed by three interconnected submodels, each representing an essential part of the highly dynamic thrombosis process (blood clotting, fibrin polymerisation, and platelet plug formation). For the description of blood flow exposed to a coagulation trigger, a multiscale approach is used to ensure physiologically relevant flow conditions even during an imminent vessel blockage.Item Periodic solution of non-symmetrical rotor vibration(University of West Bohemia, 2024) Dupal, JanThe presentation deals with an approach to periodic solution of rotor vibration represented by time dependent mathematical model. The non-symmetrical rotor is modelled in rotating coordinate system and for this reason the coefficient matrices are constant. On the contrary the stiffness matrix of the bearings is time periodically dependent. For the solution was used collocation of the describing matrix integral equation whose result is vector displacement expressed in the individual collocation points. The periodic progress of displacements is checked by time by Runge-Kutta continuation.Item Periodic solution of non-symmetrical rotor vibration(University of West Bohemia, 2024) Dupal, JanThe presentation deals with an approach to periodic solution of rotor vibration represented by time dependent mathematical model. The non-symmetrical rotor is modelled in rotating coordinate system and for this reason the coefficient matrices are constant. On the contrary the stiffness matrix of the bearings is time periodically dependent. For the solution was used collocation of the describing matrix integral equation whose result is vector displacement expressed in the individual collocation points. The periodic progress of displacements is checked by time by Runge-Kutta continuation.Item Salmon tissue compression test and its modelling using particle dynamics(University of West Bohemia, 2024) Hansen, Hendrik; Kochová, Petra; Heczko, Jan; Hajžman, MichalThe simulation of damage and fracture in soft tissue presents significant challenges. Mesh-based methods are limited by the continuous changes in material topology and geometry, while meshless approaches, such as the bonded particle method, pose difficulties in accurately representing continuous material models. This study investigates how a bonded particle model can be used for soft tissue deformation based on uniaxial compression tests with salmon tissue. With the experimental results, we calibrate an isotropic hyperelastic incompressible material model and integrate it into a custom bonded particle simulation. The study concludes with aparametric study of the behaviour and accuracy of the particle model in simulating the deformation of salmon tissue.Item Salmon tissue compression test and its modelling using particle dynamics(University of West Bohemia, 2024) Hansen, Hendrik; Kochová, Petra; Heczko, Jan; Hajžman, MichalThe simulation of damage and fracture in soft tissue presents significant challenges. Mesh-based methods are limited by the continuous changes in material topology and geometry, while meshless approaches, such as the bonded particle method, pose difficulties in accurately representing continuous material models. This study investigates how a bonded particle model can be used for soft tissue deformation based on uniaxial compression tests with salmon tissue. With the experimental results, we calibrate an isotropic hyperelastic incompressible material model and integrate it into a custom bonded particle simulation. The study concludes with aparametric study of the behaviour and accuracy of the particle model in simulating the deformation of salmon tissue.
