National Repository of Grey Literature 12 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Simple model for investigation of aerodynamic coupling in linear blade cascades
Chládek, Štěpán ; Pešek, Luděk ; Procházka, Pavel P.
Simple viscous-elastic model has been proposed for investigation of aerodynamic coupling in linear blade cascades. One blade is connected with both adjacent blades using idealized springs and dampers which represent viscous fluid. All blades may oscillate with one degree of freedom represented by vertical translation. Energy method using travelling waves model was utilized for aerodynamic damping coefficient derivation. The proposed model does not compute the damping values quantitatively, nevertheless it provides the damping shape analysis. Interesting results are presented within zero and low subsonic flow velocities, where the experiment included velocity flow field measurement.
A simple algorithm for probes positioning in BTT systems
Tchawou Tchuisseu, Eder Batista ; Procházka, Pavel ; Maturkanič, Dušan
The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the minimization of the coherence and the condition number of the sensingmatrix for defining the best probe positioning in the case of synchronous and asynchronous vibrations.
The International Colloquium dynamics of machines and mechanical systems with interactions Dymamesi 2020
Zolotarev, Igor ; Pešek, Luděk ; Kozieň, M.
The aim of the Colloquium is to facilitate the exchange of up to date information and knowledge among specialists in structural and multibody dynamics, in coupled interacting systems as aero-elasticity, hydro-elasticity, bio-mechanics, systems with feedbacks and mechatronics. The papers are divided into the three sections and focused on the Dynamics of Machines, Interactions and Power Engineering.\n\n
Dynamic and heat transfer analysis of a container with measuring instruments for space probes
Zolotarev, Igor ; Bula, Vítězslav ; Šnábl, Pavel ; Gabriel, Dušan ; Dobiáš, Jiří ; Masák, Jan ; Snížek, Jan ; Souček, Jan
Rocket boosters and spacecraft are subject to intense acoustic environments during launch, which induce high levels of vibration in structural elements and equipment. In addition, elastic structural interactions with propulsion systems and flight control systems can produce low-frequency, high-deflection flight instabilities. Natural vibration of the container with measuring equipment were studied by numerical and experimental methods in the laboratory of Institute termomechanics CAS. Heat transfer analysis inside the container was made by FEM with respect to the conditions during start of the rocket and work in space.\n
Modelling and simulation of self-balanced vertical rigid rotors
Zapoměl, Jaroslav ; Kozánek, Jan ; Košina, Jan ; Cibulka, Jan
Unbalance of rotors of rotating machines is mostly caused by the manufacturing and assembling inaccuracies. In some cases it can be induced by the rotor operation or can be variable during the rotor running. In these cases the classical approach based on attaching the balancing weights to the rotor surface is not efficient. The technological solution is offered by application of a self-balancing device. This paper deals with its design, modelling, and investigation of its functionality in dependence of the rotor operation parameters.
Design of experiment for temperature dependence of rubber samples under torsional harmonic load
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Košina, Jan ; Cibulka, Jan
This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a scheme of temperature measurement under torsional dynamic stress. The reason for these measurements is to determine the temperature dependence and sensitivity of the parameters of the thermal outputs.
Human vocal tract models with yielding walls – preliminary experimental results
Radolf, Vojtěch ; Horáček, Jaromír ; Košina, Jan
Yielding walls of acoustic cavities cause an additional low frequency acoustical – mechanical resonance of the system. This resonance changes also the higher acoustic resonance frequencies. Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of human vocal tract. The unique experimental set-up has been assembled to study in detail acoustic-structural interaction of the vocal tract cavities with a dynamical system originated in vibration of the soft tissue. The experimental results are in qualitative agreement with the results of mathematical modelling.
A hybrid boundary element based aeroelastic model for flexible wing.
Prasad, Chandra Shekhar ; Pešek, Luděk
The paper describes development of medium delity aeroelastic numerical model for fast aeroelastic analysis of the flexible aeronautical structures e.g. wings, rotor blades etc. The numerical model is developed particularly for the incompressible low subsonic flow regime application. For the flow field modeling boundary element based hybrid panel method flow solver with viscous-inviscid coupling strategy have been successfully developed and implemented here.The unsteady flow field is modeled using hybrid/modi ed panel method where, integral boundary layer theory (vis-cous part), surface panel method (potential flow inviscid part) and vortex particle method (separated shear layer modeling) are coupled together. The proposed model can simulate both attached and separated flow fields. The estimated aerodynamic lift coefficients and the pressure coefficient are compared with experimental results for static and dynamic stall flow conditions. Furthermore, the results from new aeroelastic model will be compared with classical CFD-CSD based aeroelastic models for efficiency and accuracy check. The proposed methodology for the aeroelastic analysis of long exible aeronautical structure will provide researchers and engineers a fast, cost effective and efficient tool for aeroelastic analysis for different design at preliminary design stage where large numbers of design iteration are required within short time frame.
Contribution to HPC FEM calculations of bladed disk dynamics with dry-friction contacts
Pešek, Luděk ; Šnábl, Pavel ; Bula, Vítězslav
The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tie-bosses based on 3D finite element method with surface to surface dry-friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behaviour and damping estimation of our bladed wheel design yielded a reasonable agreement. Due to dry-friction contacts and non-linear solution of 3D FE model it, however, leads to HPC computations and long computation times. The contribution deals with description of computational strategy for damping evaluation and achieved results, too.
There are linear dynamical systems with Multiple Eigenvectors?
Kozánek, Jan ; Zapoměl, Jaroslav
The steady-state response of non-damped linear and discrete dynamical systems on harmonic excitation can be expressed as the linear combination of independent eigenvectors. For special damped dynamical systems, there are some case, where the same eigenvector corresponds to the different eigenvalues.

National Repository of Grey Literature : 12 records found   1 - 10next  jump to record:
Interested in being notified about new results for this query?
Subscribe to the RSS feed.