institute of thermomechanics ascr · is a leading multidisciplinary research institute of the...

INSTITUTE OF THERMOMECHANICS ASCR

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The INSTITUTE of THERMOMECHANICS ASCR, v. v. I.

is a leading multidisciplinary research institute of the Academy of Sciences of the CzechRepublic in the field of applied physics, with several branches across the country. The Institutecooperates intensively with domestic and foreign research institutions and universities oftechnology and natural sciences. One third of our research staff are young scientists under 35years of age, primarily doctoral and postdoctoral students, to whom we provide opportunitiesfor professional development in our research programmes. Although the Institute is focusedprimarily on basic research, it maintains extensive collaboration with large industrial companies as well as dynamic and technology-oriented 5MBs.

The history ofthe Institute reaches back to 1953. The early research was focused on technicalsciences and their applications in mechanical and power engineering industries. These twocore specialisations have been central to our research up to the present day, though over thecourse oftime the Institute's research scope has extended to new and perspective fields suchas biomechanics, environmental engineering, mechatronics or electrical engineering. As aresult, the Institute has acquired a largely interdisciplinary character.

Our researchers are members and chairs of international scientific organizations and theysupervise doctora l students and trai n high-school ta lents under the country-wide educationa lprojects. Our main building is the seat of several scientific societies.

The Institute has been the guarantor of cooperation between the Academy of Sciences of theCzech Republic and the Pardubice region in East Bohemia since 2009.

Do you want to collaborate or partner with us? Are you interested in our research? Would youlike to visit the conferences and seminars organized by our Institute? Are you a student looking for a thesis topic or a research opportu nity? Visit our website or ou r Facebook and YouTu bepages for more information. You can also visit us to discuss how our knowledge and researchcan help your business. And our selected laboratories in Prague, Pilsen and Novy I<nin areopen to the general public during the annual Open Days held every autumn.

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FLUIDS AND THERMAL SCIENCES RESEARCH

~HIGH-SPEED AERODYNAMICSThe experimental research of high-speedflows in steam and gas turbines, compressors, ejectors and steam valves has almost50 years oftradition in the Institute ofThermomechanics. Internal gas flows in modelsof flow machinery are studied in the windtunnels in Novy I<nin near Prague using theMach-Zehnder interferometer and otheroptical and pneumatic methods.

Our key partner in aerodynamic research isDoosan Skoda Power. Our cooperation withthe former SI<ODA Pilsen concern began inthe 1960s and was formalized at the begin-

ning of the 1970s with the signing of acontract for long-term cooperation. In the1980s ou r scientists and thei r colleaguesfrom Skoda were awarded a medal at theInternational Engineering Fair in Brno forthe design of a 240-MW turbine for nuclearpower plants.

Today our laboratories are equipped withseveral wind tunnels suited for differentapplications. The research continues in itsrich tradition and focuses on modern powerengi neeri ng applications.

Colour schlierenimageoftheflowin the bladecascadeof the laststage of alarge steam turbine.

Interferogram of airflow ina control valve, thefringescorrespond to regions ofthe same density.

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~HEAT AND MASS TRANSFEROur research of heat and mass tra nsfer ingases and liquids is focused on the passiveand active control of flows and thermalfields. Using an experimental approach westrive to discover new ways to intensify thetransport of heat and mass during forcedconvection in wakes and impinging and

synthetic jets. The results are useful in fluidics/microfluidics, the cooling of electronic components or gas turbine blades,improving the efficiency of mixing in chemical reactors or in external and internal aerodynamics.

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Smoke visualization ofa syntheticjet.

Coherent vortex lines in theshear layerand theirbreakdown, smokevisualizationof submerged airjet.

Wake flow behind a cooledcircular cylinder(Von Karman vortexstreet).


~NON-EQUILIBRIUM MULTIPHASE SYSTEMSChanges of states of matter (or, more accurately, phase transitions) in nature and inengineering applications occur at a finiterate and under conditions that are more orless distant from the thermodynamic equilibrium (for example from the equilibriumboiling point). The non-equilibrium phasetransitions include the formation (nucleation) of droplets in steam turbines and inthe atmosphere, the nucleation of ice insidethe droplets, the deposition of ice on the

leading edges of airplane wings or theformation of cavitation bubbles in pumpsand liquid turbines. Our research is focusedon the measurement and modelling ofthese non-equilibrium phase transitions, onstudying the properties of metastable liquids (e.g. supercooled liquid or supersaturated vapour) prior to the phase transitionand on the characterisation of multi phasesystems in sprays, aerosols and bubbles.

~THERMOPHYSICAL PROPERTIES OF LIQUIDSDensity, viscosity, surface tension and other to develop mathematical models of thethermophysical properties of liquids serve properties. We measure relations betweenas the input parameters for the design of pressure, volume and temperature for envi-power engineering and chemical devices ronmentally friendly refrigerants and newand for the modelling of geophysical and ionic liquids using the constant-volumebiological processes. We carry out very method and a vibrating tube. Tensiometricprecise measurements of thermophysical methods and the method of capillary eleva-properties of liquids and use the obtained tion help us to determine the surfaceexperimental data and the laws of physics tension of the substances.

A significant part of our research of multiphase systems and the thermophysical propertiesof liquids is motivated by the priorities of the International Association for the Properties ofWater and Steam (IAPWS), whose national committee is headquartered from the Institute ofThermomechanics ASCR.

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~TU RBU LENT FLOWSDespite the recent advances in experimental and computational techniques thefundamentals of turbulent flows continueto puzzle scientists, being arguably the lastunsolved problem of classical physics. Weconcentrate on the experimental andnumerical modelling of turbulent flows andthe tra nsition to tu rbu lence in 3D geome-

tries, measuring the velocity fields andturbulent flow characteristics and studyingfluid-solid interactions. Our results areapplied in the aerodynamic optimisation offlow past bodies (e.g. aircraft or automobiles) or flow machinery (turbines andcom pressors).

Isosurfaces of the verticalcomponent of the time-averagedmean velocity downstream ofa step in a narrow channel.

r Kidnev-stiaoed impactobjectat the channelbottom.

Turbulent flow of airin a rectangular-cross-section

channel. Energy dynamicmodecharacterizing velocity field

fluctuations.

Channel flow; the isosurfacesof the component of thetime-averaged mean velocitynormal to the channelbottomcharacterize the space topologyof theflow field.

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ENVIRONMENTAL AERODYNAMICSThe atmospheric dispersion of emissionsand dangerous substances from local andarea sources or road traffic or during chemical accidents or terrorist attacks affects asociety's health, safety and quality of life.Simulating atmospheric pollution and studying the interaction between urban areasand atmospheric flow helps us to improveour environment and brings benefits to allof us. The results of our studies have been

used to build more accurate city evacuationplans in, for example, Prague and Pardubice.We use the physical and mathematicalmodelling of flow and diffusion in theatmospheric boundary layer, various flowvisua lization techniques and measurements of flow velocities in a specializedwind tunnel in the Aerodynamic laboratoryin Novy I<nin.

Particle ImageVelocimetry (PIV)analysisof turbulentflow within streetcanyon inatmosphericboundary layer.

Simulation ofchlorine dispersion

over Pardubicetrain station,

concentration10 mabove ground level.

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RESEARCH OF SOLIDS AND MECHANICAL SYSTEMS

~DIAGNOSTICS OF MATERIALS AND STRUCTURES

we are able to localize material defects,evaluate the damage caused by the loading,fatigue, corrosion or wear of structural partsand predict their lifetime. The methods canbe used to predict building failures anddetect leakages of gases and liquids frompressurized vessels and tubes. Ultrasonicmethods can be used in medical diagnostics of the properties of human skin andtheir changes due to mechanical loading orUV radiation.

We also conduct measurements of changesduring the thermal aging of materials aftertheir cyclic thermal loading (e.g. the agingof the polymer insulation of electric cables)or nanoindentation measurements ofchanges in hardness and the ratio of elasticand plastic deformations of materials. Wecan also evaluate gradual changes ofmechanical properties and the behaviour ofmaterials under low-cycle and high-cyclefatigue loading with combined tension andcompression or even torsion.

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The reliability and safety of aircraft, nuclearpower plants, chemical plants, civil structures, pipelines, storage tanks and certainmachines require the periodic health monitori ng. Our methods of nondestructivetesting (NOT) and evaluation of defects arebased on the propagation of elastic wavesin solids. We use advanced signal analysis(e.g. time reversal mirrors) and data processing (e.g. artificial neural networks). With theuse of acoustic emission and nonlinearultrasonic spectroscopy and other methods

Acoustic emission sources and zones withcracks detectedby nonlinear ultrasonicspectroscopy with time reversal mirrorsduring thefatigue test of an aircraftwingflange.

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~ELASTIC AND THERMOMECHANIC PROPERTIESOF MATERIALS AND THIN LAYERS

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Studying elastic and thermomechanic properties of solids and thin layers helps us tobetter understand modern functional materials such as ferromagnetic and ferroelectricmaterials, fibre composites, ceramics,shape-memory alloys and thermal spraycoatings. To measure the elastic propertiesof materials we use Resonance UltrasoundSpectroscopy (RUS), which was developedin our laboratories. Using other methods,includi ng laser ultrasou nd methods, the

ultrasonic pulse-echo method, scanningacoustic microscopy and the surface acoustic wave method, we measure and characterize the elastic properties of materia ls, wemeasure the plane elasticity of thi n coatings and surface layers (such as plasmacoatings), the elastic anisotropy of extremely fine-grained materials and the mechanical properties and temperature changes insolids in-situ during their loading and wecharacterize phase transitions in solids.


Eigenmode of 3D vibrationof prismatic body(measurement by RUS;Resonance UltrasoundSpectroscopy).

Propagation of elasticwavein silicon waferovertime.

Sample of the Cu-Al-Ni smartalloyfor RUS measurements.

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~VIBRODIAGNOSTICS AND ROTOR DYNAMICSThe contactless analysis of the vibrations,state and potential damage of complexmechanical systems during operations enables the advanced planning of maintenance shutdowns. The system developed inour Institute measures the motion, vibrations and loading of rotating mechanicalparts (such as turbine and compressorblades). The system is installed in severalpower stations in the Czech Republic,where it has helped to achieve significa ntsavings in maintenance.

The vibrodiagnostics of rotating machinesand vibroacoustics also help to study thevibrations of railway wheels, bearings,shafts, brakes, rolling mills, crushers and

other machines. These techniques have abroad application - e.g. they can help tosuppress the noise generated by railway ortramway traffic, which has an adverse effecton the quality of life and the environment.We are helping one of the largest manufacturers of railway wheels in Europe to develop technology for the optimum damping ofrailway wheels. We also measure the dynamic characteristics of rubber materialsand develop models of vibrations and interactions of non-linear dynamic systems. Andlast but not least, we also study the influence of the new types of bearings, such asmagnetic bearings and bearings with magnetorheological dampers, on the rotor dynamics.

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Vibration eigenmode ofa rubber-damped railway wheel.

Distribution of the magneticflux density in the body ofthe magnetorheological squeeze film damper.


~COMPUTATIONAL MECHANICS OF SOLIDSAND MECHANICAL SYSTEMSIn our institute we develop, implement andtest numerical and analytical methods forcontinuum mechanics. Our main interestlies in linear and non-linear static anddynamic problems, thermomechanicalproblems, stress wave propagation, problems of the contact and impact of deformable bodies and the development of constitutive equations for solids. We also developa FEM-based (Finite Element Method)computational PMD (Package for MachineDesign) system, which has received the

certificate of the State Office for NuclearSafety.

We put a vast effort into studyi ng materia ldefects, crack-growth mechanisms andcrack propagation in crysta lli ne materia lsusing molecular dynamic (MD) simulationsand multi-scale methods. We also collaborate on the calculation of electron structures and total energies of non-periodicsystems using FEM and pseudopotentialmethods.

Example of FEM-based meshfor themechanical analysis of a complexstructure.

Snapshot of a stressstate of twothin-walledtubes at impact.

Molecular dynamicssimulation oftransonicpropagation of crystaldefect in the Beephaseof iron withshock waves.

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ELECTRICAL ENGINEERING AND INTERDISCIPLINARY RESEARCH

~ELECTRIC DRIVES AND POWER ELECTRONICSThe current challenges of power engineering, such as power quality and the stabilityof the power grid with a large ratio ofrenewable energy sources, place new demands on electrical engineering research.In our laboratories we focus on the researchof electric drives, electric rotating machinesand power electronics and on other electromechanical conversions. The results of ourresearch can be applied, for example, in thedesign of electric generators for wind andhydro power plants. We study the circuitstructu re of solid-state power convertersand the mutual interaction of power invert-

ers. machines and the power grid anddevelop advanced control and diagnosticalgorithms for inverters. In collaborationwith (KO Elektrotechnika we are developing AC drives fed from multi-level, highvoltage inverters for demanding industrialapplications. The design of a power inverterfor a new-generation drive for miningequipment, developed as a joint effort of(KO Elektrotechni ka and ou r Institute, wasawarded the GOLDEN AMPER award at theinternational AMPER 2011 trade fair. We area competence centre of the EuropeanCentre for Power Electronics.

Numerical model of a magneticfield in an induction machine.

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~ELECTROPHYSICS AND COUPLED PROBLEMSIN ELECTRICAL ENGINEERINGComplex phenomena in electrical engineering require insight into other fieldssuch as electrophysics or electrical powerengineering. We use experimental techniques to study dynamic phenomena inelectric arcs and thermal plasma jets, whichare used in plasma coating, metal cutting orwaste disposal technologies. We alsodevelop novel numerical methods for

coupled problems in heavy-current andelectrical power engineering. These methods are applied in the electromagneticprocessing of solid and molten metals,electromagnetic stirring and melting, thepumping of molten metals, hot pressing,thermoelasticity and in the development ofelectromagnetic actuators (devices converting electrical to mechanical energy).

3D tomographicalreconstruction of turbulentthermal plasmajet.

Microphotography of moltenhafnium pool at cathode tip of

plasmatron cutter: Differentcolours denote different

temperatures of the moltenhafnium.

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~INTERDISCI PLI NARY RESEARCHA significant part of our research is highlyinterdisciplinary. Our fields of interestinclude biomecha nics, biophysics, mechatronics, robotics or fluid-structure interaction.

Our biomechanical and biophysical research finds applications in medicine ordermatology. We model changes in bonetissue under dynamic loading, the flow ofcerebrospinal fluid or the flow of liquids inelastic tubes (e.g. blood flow through the

heart and the bloodstream). We search forthe optimum lubrication of hip-joint endoprotheses and study the biomechanics ofthe human voice or the biophysics ofcardiac cells.

Our joint centre with the Brno University ofTechnology develops methods of ArtificialIntelligence (AI) in engineering. Thesemethods are tested and applied in mechatronic and robotic systems of our owndesign.

We develop theoretical models of interaction between fluid flows and deformable bodies.We are interested mostly in the vibration characteristics and stability limits of aero-hydroelastic systems, mainly the aeroelasticity of airfoils.

Four-legged walking robotfor walking gaitself-generation verification.

In vivodestroyed ceramic totalhipjoint endoprothesis.

Numerical simulation of flowaroundairfoil flutter.

Dolejskova 1402/5182 00 PragueCzech Republic

Ph.: +420 266 052 021Fax: +420 286 584 695Email: secreit.cas.cz

www.it.cas.cz

institute of thermomechanics ascr · is a leading multidisciplinary research institute of the...

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