Damping of human vocal folds vibration
Radolf, Vojtěch; Horáček, Jaromír; Bula, Vítězslav; Geneid, A.; Laukkanen, A. M.
2022 - English
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal fold damping is important for testing and further development of mathematical modelling of phonation. The measurements of the damping ratio, based on high-speed videolaryngoscopic registrations, were realized on a male subject phonating on the vowel [o:]. The results show during the phonation offset a remarkable decrease of vibration frequency of the vocal folds and an increased damping ratio limiting to the value D≈ 0.2. The results for vocal folds’ damping are in agreement with previous measurements performed on humans using different methods.
Keywords:
damping ratio measurement; phonation offset; high-speed videolaryngoscopy
Fulltext is available at external website.
Damping of human vocal folds vibration
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal fold damping is important for testing and further ...
Design of the magnetically sensitive hydrodynamic bearing for the experimental rotor rig
Ferfecki, P.; Zapoměl, Jaroslav; Molčan, M.
2022 - English
In a hydrodynamic bearing, the relative motion between the rotating shaft and stationary housing is separated by a thin film of a lubricant. The magnetically sensitive lubricants with the promise of a semiactive control are able to improve the vibration response of the rotor system supported by the hydrodynamic bearings. A design of the magnetically sensitive hydrodynamic bearing is briefly introduced in this paper. The presented experimental rotor rig is proposed to analyse the large range of load conditions and rotational speeds of the bearing. The designed hydrodynamic bearing is intended to test the ferrofluids, magnetorheological oils, and nano-micro composite magnetic fluids. The apparent viscosity of the magnetically sensitive lubricant is altered by the magnetic field generated by the electric coil and thus the position of the bearing journal is shifted. The experimental measurement results show that the rheological behaviour of the lubrication layer with a magnetorheological fluid is significantly influenced by a magnetic field. The raising magnitude of the current in the electric coil leads to an increase in the bearing's load performance.
Keywords:
magnetically sentivive fluid; hydrodynamic lubrication; sommerfeld number; experimental measurement; load bearing capacity
Fulltext is available at external website.
Design of the magnetically sensitive hydrodynamic bearing for the experimental rotor rig
In a hydrodynamic bearing, the relative motion between the rotating shaft and stationary housing is separated by a thin film of a lubricant. The magnetically sensitive lubricants with the promise of a ...
Analytické postupy řešení kmitání lopatek pro použití u metody Blade Tip Timing - teoretický popis metody
Maturkanič, Dušan; Procházka, Pavel; Mekhalfia, Mohammed Lamine
2022 - Czech
Práce je zaměřena na analytický přístup k řešení problematiky kmitání lopatek turbíny a kompresoru metodou Blade Tip Timing. Ve zprávě je navržena nová metoda, pro niž byly stanoveny podmínky řešení. Ověření metody bylo provedeno prostřednictvím simulace, kdy byla vyhodnocena spolehlivost, u které byla zadávána správná vstupní data a výpočet probíhal po dostatečně dlouhou dobu, zatímco na základě záměrně zkreslených vstupních dat byla ověřována její přesnost. Součástí zprávy je také vazba výsledků výpočtu frekvence kolísajících otáček, získaných deterministickou metodou, která byla popsána v předchozích pracích, a s nimiž lze dosáhnout přesnějšího výpočtu frekvence a amplitudy kmitání lopatek v reálných podmínkách.\n\n The report focuses on an analytical approach to solving the problem of turbine and compressor blade vibration using the Blade Tip Timing method. The report contains a description of the new method with defined solution requirements. Verification of the method was performed by simulation, where the correct input data was used in the analysis of the reliability of the method when the calculation was repeated at a sufficiently large number of revolutions, while in the accuracy analysis, intentionally distorted input data was used. The report also includes connection to the results of frequency and amplitude calculation for fluctuating speeds obtained by the deterministic method, which was described in previous works aimed at achieving a precise calculation of the frequency and amplitude of blade vibration in real conditions.
Keywords:
vibration; blade; analytical method; frequency; amplitude; turbine; compressor; sensor
Available at various institutes of the ASCR
Analytické postupy řešení kmitání lopatek pro použití u metody Blade Tip Timing - teoretický popis metody
Práce je zaměřena na analytický přístup k řešení problematiky kmitání lopatek turbíny a kompresoru metodou Blade Tip Timing. Ve zprávě je navržena nová metoda, pro niž byly stanoveny podmínky řešení. ...
Effect of oscillating blade on tonal noise of blade cascade with five NACA 0010 profiles
Šnábl, Pavel; Pešek, Luděk; Radolf, Vojtěch; Antoš, Pavel; Procházka, Pavel P.; Prasad, Chandra Shekhar
2022 - English
The airfoil tonal noise is a well known phenomenon which appears on single airfoils in moderate Reynolds numbers at low angles of attack. It can appear on small aircrafts, fans, wind turbines etc. In thispaper, it was observed on a blade cascade consisting of five NACA 0010 profiles placed in a closed rectangular channel with hard walls when for given conditions, i.e. flow velocity and angle of attack, the cascade tunes to one single frequency. During the middle blade oscillation, the single tone splits up to several tones with lower intensity modulated by the excitation frequency. Thus, the oscillation of one blade suppresses the tonal noise generation in the cascade.
Keywords:
aeroacoustics; blade cascade; trailing edge noise; tonal noise; NACA 0010
Fulltext is available at external website.
Effect of oscillating blade on tonal noise of blade cascade with five NACA 0010 profiles
The airfoil tonal noise is a well known phenomenon which appears on single airfoils in moderate Reynolds numbers at low angles of attack. It can appear on small aircrafts, fans, wind turbines etc. In ...
Final Report of the Centre of Excellence for Nonlinear Dynamic Behaviour of Advanced Materials in Engineering
Parma, Slavomír; Gabriel, Dušan
2022 - English
This final report presents the CeNDYNMAT Center of Excellence, which was established at the Institute of Thermomechanics of the Czech Academy of Sciences in 2016 and ended in 2022. The report summarizes the most important scientific results of the center. It also gives an overview of the main outcomes and developments of the project, including budgeting, purchasing instrumentation, international cooperation and organization of conferences and summer courses.
Keywords:
nonlinear dynamic behavior; advanced materials; metal plasticity
Available at various institutes of the ASCR
Final Report of the Centre of Excellence for Nonlinear Dynamic Behaviour of Advanced Materials in Engineering
This final report presents the CeNDYNMAT Center of Excellence, which was established at the Institute of Thermomechanics of the Czech Academy of Sciences in 2016 and ended in 2022. The report ...
Vývoj a implementace 3D metod geometrické extrakce pro topologickou optimalizaci
Šotola, M.; Rybanský, D.; Maršálek, P.; Halama, R.; Kopačka, Ján; Ježek, Ondřej; Gabriel, Dušan; Tejc, J.; Pašek, M.; Kovář, L.
2022 - Czech
Výzkumná zpráva TN01000024/08-V012 je výstupem dílčího úkolu projektu TN1000024/08 Automatizace a optimalizace výrobních procesů, jehož jedním z cílů je vyvinout metody následného zpracování výsledků topologické optimalizace (TO) ve spolupráci s firmou MECAS ESI s. r. o. Tři různé přístupy vyhlazování byly analyzovány: Taubinova metoda, objemová reprezentace s využitím radiálních bázových funkcí a vyhlazení přesít’ováním využívající knihovnu Netgen. This research report TN01000024/08-V012 is an output of the subtask of the project TN1000024/08 Automation and production system optimization, one of the objectives of which is to develop methods of post-processing of topological optimization (TO) results in cooperation with MECAS ESI Ltd. Three different smoothing approaches are discussed: the Taubin method, volume representation using radial basis functions and smoothing by remeshing using the Netgen library.
Keywords:
topology optimization; post-processing; smoothing methods; Taubin method
Available at various institutes of the ASCR
Vývoj a implementace 3D metod geometrické extrakce pro topologickou optimalizaci
Výzkumná zpráva TN01000024/08-V012 je výstupem dílčího úkolu projektu TN1000024/08 Automatizace a optimalizace výrobních procesů, jehož jedním z cílů je vyvinout metody následného zpracování výsledků ...
Problematics of aerodynamic damping calculation from measured data of 5-blade cascade
Šnábl, Pavel; Pešek, Luděk; Prasad, Chandra Shekhar; Chindada, Sony
2022 - English
Aerodynamic damping as a function of inter-blade phase angle (IBPA), so called S-curve, is crucial for assessment of aeroelastic stability of blade cascades, e.g. turbines, compressors, etc.\nFor constructing the S-curve, the motion-induced controlled flutter is introduced to the bladesof the cascade. As decribed in [1], two testing methods exist: aerodynamic influence coefficient\n(AIC) approach and travelling wave mode (TWM) approach. In TWM approach, all blades in a row oscillate with the same frequency and amplitude with various IBPAs. The response is\nmeasured only on the reference blade. With this approach, several measurements with different IPBAs are needed to construct the S-curve. On the other hand, AIC uses single oscillating\nblade and principle of linear superimposition of aerodynamic influence responses measured on all blades in a cascade. The result of one single measurement can be used for estimation of\naerodynamic damping for any IBPA. In the past year a new 5-blade cascade with rotating symmetrical NACA 0010 profiles was designed and built. The blades of the cascade were placed further apart and thus we are now able to reach stall flutter. Also, the suspension of the blades and sensors were significantly improved. Now, our goal is to evaluate S-curves using AIC approach for different flow conditions and oscillation frequencies.
Keywords:
aerodynamic damping; S-curve; blade cascade
Available at various institutes of the ASCR
Problematics of aerodynamic damping calculation from measured data of 5-blade cascade
Aerodynamic damping as a function of inter-blade phase angle (IBPA), so called S-curve, is crucial for assessment of aeroelastic stability of blade cascades, e.g. turbines, compressors, etc.\nFor ...
Měření fotokatalytické účinnosti nátěru fn nano®2 na idealizovaném modelu městské zástavby
Nosek, Štěpán
2022 - Czech
Metodou fyzikálního modelování byl v aerodynamickém tunelu ÚT AV ČR v Novém Kníně úspěšně uskutečněn experiment simulující odbourávání zdraví nebezpečného polutantu (NOX) fotokatalýzou na povrchu ošetřeném aktivním nátěrem FN NANO®2 uvnitř modelu městského uličního kaňonu. Za kontrolovaných podmínek (stejný směr a střední rychlost nabíhajícího větru, neutrální stratifikace atmosféry) byly simulovány dva případy znečištění uličního kaňonu: i) liniovým zdrojem uvnitř kaňonu simulujícím znečištění koncentracemi NO z automobilové dopravy, a ii) nabíhající mezní vrstvou, jenž byla znečištěna koncentracemi NOX (tedy směsi NO a NO2) z automobilu. Oba simulované případy prokázaly stejné průměrné účinnosti (15 %) a stejný trend účinnosti nátěru pro odbourávání NOX (účinnost klesá s výškou) uvnitř uličního kaňonu (zahrnující absolutní chybu účinnosti 1,3 %). Stejné výsledky výše uvedených rozdílných metod poukazují na nezávislost možného použití jedné z těchto metod pro analýzu odbourávání výsledných koncentrací NOX nátěrem FN NANO®2 uvnitř uličního kaňonu. Při vyšetřování lokální účinnosti a účinnosti odbourávání čistého NO nebo NO2 byla prokázána závislost účinnosti odbourávání na pozici zdroje znečištění (uvnitř/vně kaňonu) a složení vstupního plynu (buď pouze NO, nebo směs NO a NO2). Stanovit účinnost odbourávání jednotlivých polutantů (NO a NO2) tak šlo pouze v případě znečištění uličního kaňonu nabíhající mezní vrstvou (ii). Byly prokázány velmi vysoké účinnosti nátěru při odbourávání NO (průměrná účinnost 19 %) a účinnosti při odbourávání NO2 dosahují průměrně 7 %.\n An experiment was conducted to test the effectiveness of the FN NANO®2 coating in removing a harmful pollutant (NOX) by photocatalysis on a surface in a model of an urban street canyon. The experiment was conducted in a wind tunnel under controlled conditions, simulating two cases of street canyon pollution: from a line source within the canyon and a polluted incoming boundary layer. The results showed that the coating has an average efficiency of 15% when removed from NOX, with the efficiency decreasing with height within the street canyon. The removal efficiency depends on the type of pollution. In the case of the polluted incoming boundary layer, the coating showed very high efficiency in removing NO (average efficiency of 19%) and NO2 (average efficiency of 7%). These results show that both methods can be used to analyse the removal of NOX concentrations by the FN NANO®2 coating in a street canyon.
Keywords:
photocatalysis; NOx; TiO2; street canyon; air purification; urban air pollution
Available at various institutes of the ASCR
Měření fotokatalytické účinnosti nátěru fn nano®2 na idealizovaném modelu městské zástavby
Metodou fyzikálního modelování byl v aerodynamickém tunelu ÚT AV ČR v Novém Kníně úspěšně uskutečněn experiment simulující odbourávání zdraví nebezpečného polutantu (NOX) fotokatalýzou na povrchu ...
Determination of current floor during mobile robot elevator ride
Krejsa, Jiří; Věchet, Stanislav; Chen, K. S.
2022 - English
In order for the mobile robot to use the elevator, it must be capable to call the elevator in, detect the control panel, select desired floor and to determine what floor is the elevator located. The paper deals with determination of correct floor the mobile robot is currently at using the processing of onboard accelerometer data. Up to 5 relative floor difference the method exhibits over 95% accuracy.
Keywords:
mobile robot; elevator floor determination; signal processing
Fulltext is available at external website.
Determination of current floor during mobile robot elevator ride
In order for the mobile robot to use the elevator, it must be capable to call the elevator in, detect the control panel, select desired floor and to determine what floor is the elevator located. The ...
Control system architecture for novel experimental microalgae photobioreactor Simbios
Věchet, Stanislav; Krejsa, Jiří; Chen, K. S.
2022 - English
Photo-bioreactors for growing biomass based on various microalgae cultures gains interests nowadays due to have possible positive impact to society because of the potential to serve as an atmospheric carbon dioxide removal (CDR) device, produce food or fuel. We present an overall architecture of a control system designed with focus to keep the photo-bioreactor alive for long term continuous operation without any human supervision needed. To test overall control system stability we design a custom build spiral photo-bioreactor (PBR) with novel hyperbolic shaped illuminated part. The shape of the illuminated part was design with the goal to increase the ratio of spiral part to volume due to the fact that the light is crucial for microalgae to grow. The control system was created from scratch while adopting reliable IoT sensors combined with highly reliable custom build embedded control system including a cloud data processing and storage. As a result we have scalable and reliable solution which is suitable for photo-bioreactors of various shapes and sizes to operate in fully autonomous mode without any human supervision needed.
Keywords:
photobioreactor; IoT sensors; control system,
Fulltext is available at external website.
Control system architecture for novel experimental microalgae photobioreactor Simbios
Photo-bioreactors for growing biomass based on various microalgae cultures gains interests nowadays due to have possible positive impact to society because of the potential to serve as an atmospheric ...
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