2015 Programme

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2 December 2015, 10:00

Fractography and Failure Analysis

Prof. Jan Siegl, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague

Lecture outline:
1) Basic methodology of the fractographic analysis
2) Methods of quantitative fractography – reconstructions of fatigue crack growth kinetics (materials characterization and failure analysis of aircraft structures)
3) Analysis of operational failures and brakedowns (case study for turbines)

4 November 2015, 10:00

Scalable algorithms for the solution of contact problems with 10e9 unknowns

Prof. Zdeněk Dostál, Faculty of Electrical Engineering and Computer Science, VŠB - Technical University of Ostrava

An overview of the theoretical results on optimal algorithms for the solution of special problems of quadratic programming and QCQP will be given together with the adaptation of TFETI domain decomposition method for the solution of contact problems. Then will be presented a short summary of theoretical results showing the asymptotically linear complexity of the presented algorithms for frictionless, Tresca, and transient problems. The theoretical results will be illustrated by the solution of large real world contact problems and academic problems discretized by over 10e9 variables.

12 October 2015, 13:30

Aerodynamic Control using Virtual Surface Modification

Prof. Ari Glezer, Woodruff School of Mechanical Engineering, Georgia Institute of Technology
A novel, scalable approach to flight control by distributed fluidic modification of the apparent aerodynamic shape of the lifting surfaces, or virtual aerosurface shaping will be discussed. Robust control of attached and separated flows is engendered by leveraging the generation, accumulation, and advection of vorticity concentrations near the surface to alter its aerodynamic shape and thereby the aerodynamic forces and moments without mechanical control surfaces. Actuation is effected by the interactions of arrays of surface-integrated jets with the local cross flow such that the actuation time scale is typically considerably lower than the relevant characteristic time scale of the flow. The presentation will also describe applications of virtual aerosurface shaping to manoeuvring, drag reduction, and structural stabilization.

7 October 2015, 10:00

Multi-Phase Electric Machines and Drives

Prof. Miroslav Chomát, Institute of Thermomechanics of the CAS, v. v. i.

The recent advances in power electronics have enabled the employment of some unconventional types of electric machines in drives. In this regard, increasing attention has been paid to machines with the number of phases higher than three. The lecture will focus on the advantages, disadvantages and specific properties that need to be taken into account when designing and developing drives with these machines.

3 June 2015, 10:00

Ultrasonic characterization of advanced material

Dr. Michal Landa, Institute of Thermomechanics of the CAS, v. v. i.

Motivation - investigation of relationships between the mechanical properties and microstructures of advance materials; determination of anisotropic elasticity, and detection of phase transformations and thermally activated processes. Why do we need an ultrasound? Necessity of contactless measurements. Advantages of recent all-optical techniques in ultrasonics (laser-ultrasonics).

6 May 2015, 10:00

Application of contact algorithm in creep analysis of high-pressure casing DSPWR

Dr. Dušan Gabriel, Institute of Thermomechanics of the CAS, v. v. i.

First, the laboratories of the Department D4 - Impact and Waves in Solids will be briefly introduced. Next, the contribution will be aimed at the long-term development of a general three dimensional contact algorithm for the solution of complex engineering problems including the effects of material and geometric non-linearities. The key feature of this algorithm is that the contact search is performed at the Gaussian points rather than the nodes. The method was shown to be consistent with the variational formulation of a continuum problem, which enabled easy incorporation of higher-order elements with midside nodes to the analysis. The test problem involved creep analysis of high-pressure casing of the DSPWR steam turbine. Material properties were described by the probabilistic exponential model with damage. The FE prediction of permanent displacements in time 10 thousand and 200 thousand hours and a deformed shape of the dismantled casing was obtained. The analysis was performed in the FE code PMD (Package for Machine Design) developed at Department D4. The results were compared with FE code ANSYS.

1 April 2015, 10:00

Experimental and theoretical research of friction coupling effect on dynamics of bladed discs

Dr. Luděk Pešek, Institute of Thermomechanics of the CAS, v. v. i.

The laboratories of the department Dynamics and Vibration will be briefly introduced at the beginning. Then the contribution will be aimed at the development of experimental and computational methods for explanation of the friction coupling effect in rotary bladed machines. By means of the friction couplings in the blading, the reduction of dynamical straining of blades of rotary wheels can be achieved. Therefore new experimental procedures on the test wheel model including theoretical analytical-numerical methods enabling parametric optimization of dynamic model of bladed wheels will be presented.

4 March 2015, 10:00

The Department of Thermodynamics at a glance and research of the homogeneous nucleation of droplets

Dr. Jan Hrubý, Institute of Thermomechanics of the CAS, v. v. i.


The lecture will consist of two parts. In the first part, the research activities of the Department of Thermodynamics will be overviewed. Most of the research is performed in three laboratories. Density and surface tension for newly appearing fluids such as ionic liquids are precisely determined and correlated in the Laboratory of Thermophysical Properties of Fluids. Transport phenomena in various flow configurations including synthetic jets and microfluidic devices are investigated in the Laboratory of Heat and Mass Transfer. Metastable states of fluids, such as supercooled water or supersaturated steam, and nucleation of new phases are subject of research in the Laboratory of Phase Transition Kinetics.

In the second part of the lecture, the problem of homogeneous nucleation of droplets from supersaturated vapors will be introduced. The research is motivated by applications in steam turbines, natural gas processing, carbon dioxide separation and storage, and atmospheric phenomena. Experimental techniques will be reviewed with an emphasis on expansion-based devices for high nucleation rates. Although the so-called classical nucleation theory (CNT) is available for decades, no breakthrough happened allowing to quantitatively predict correct temperature and pressure dependencies of the nucleation rates. Own research will be introduced, considering the effects of finite thickness of the phase interface and its undulation by capillary waves, coupled to the universal critical scaling relations.


4 February 2015, 10:00

Aerodynamic Research on the Tip Sections of Long Rotor Turbine Blades

Dr. Martin Luxa, Institute of Thermomechanics of the CAS, v. v. i.


The lecture is focused on systematic aerodynamic research on the flow structures and flow parameters of tip section cascades at transonic and supersonic regimes of operation. The analysis of the flow is based on numerous detailed wind tunnel measurements of five tip blade cascades of different design. The blade cascades represent tip sections of the last stage rotor bladings with length of blades 860 mm, 1080 mm, 1220 mm, 1375 mm and 1525 mm.

Aerodynamic experimental research of the tip blade cascades is oriented to providing data on high-speed flow of compressible fluid past tip sections of blades. The analysis of experimental data is aimed to transonic effects namely expansion over sonic conditions, aerodynamic choking, development of supersonic flow, boundary layer development, the flow past trailing edge, exit shock waves, interaction of shock wave with boundary layer, wakes, etc.

Results of experiments are invaluable not only for improvements of new machine results but also for numerical modeling of transonic flow and numerical solution of flow in flow paths of turbomachines




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