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The use of Lempel-Ziv complexity to analyze turbulence and flow randomness based on velocity fluctuations

Blonski S., Pregowska A., Michalek T., Szczepanski J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2019

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Vol. 67, nr 5

957--962

EN

One of the mathematical tools to measure the generation rate of new patterns along a sequence of symbols is the Lempel-Ziv complexity (LZ). Under additional assumptions, LZ is an estimator of entropy in the Shannon sense. Since entropy is considered as a measure of randomness, this means that LZ can be treated also as a randomness indicator. In this paper, we used LZ concept to the analysis of different flow regimes in cold flow combustor models. Experimental data for two combustor’s configurations motivated by efficient mixing need were considered. Extensive computer analysis was applied to develop a complexity approach to the analysis of velocity fluctuations recorded with hot-wire anemometry and PIV technique. A natural encoding method to address these velocity fluctuations was proposed. It turned out, that with this encoding the complexity values of the sequences are well correlated with the values obtained by means of RMS method (larger/smaller complexity larger/smaller RMS). However, our calculations pointed out the interesting result that most complex, this means most random, behavior does not overlap with the “most turbulent” point determined by the RMS method, but it is located in the point with maximal average velocity. It seems that complexity method can be particularly useful to analyze turbulent and unsteady flow regimes. Moreover, the complexity can also be used to establish other flow characteristics like its ergodicity or mixing.

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Wheel/rail contact geometry research and development of locomotive Class 744.0 as examples of R&D activities of the Jan Perner Transport Faculty

Zelenka J., Michalek T., Kohout M.

TTS Technika Transportu Szynowego

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2016

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R. 23, nr 1-2

80--83

EN

The Jan Perner Transport Faculty (JPTF) of the University of Pardubice and especially its Department of Transport Means and Diagnostics deals with research and development activities in the branch of railway vehicles. There are two basic reasons for that. At first, it is incumbent upon all academic workers to pursue the science and research according to the Czech law concerning the universities. And the second reason is a relation to the educational process - if the JPTF wants to offer a high quality education in the specialization "Railway Vehicles" (which is offered in Czech as well as English language today) to its students, the research activities of the academic workers (i.e. the teachers) allow them to stick to the newest trends in the branch. In this article, particular examples of cooperation of the JPTF with producers as well as operators of railway rolling stock are presented as a contribution of the faculty to the research and development in the branch of railway vehicles.

PL

W artykule przedstawiono aktywność badawczą Wydziału Transportu Uniwersytetu w Pardubicach (Czechy) w zakresie pojazdów kolejowych. Scharakteryzowano wyposażenie laboratoriów wykorzystywane do badań teoretycznych i eksperymentalnych. Skoncentrowano się na zagadnieniach dostosowania profili kól do specyficznych warunków ruchowych oraz współpracy przy konstrukcji nowej lokomotywy.

3

A new method of the assessment of rail vehicles guiding behaviour in small-radius curves

Zelenka J., Michalek T.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 2

511-519

EN

This paper deals with the assessment of rail vehicles guiding behaviour during passing through small-radius curves. This assessment according to the European standard EN 14363 or the UIC Code 518 is a part of the authorization process in the case of new, reconstructed or modernized railway vehicles. The new version of UIC Code 518:2009 modifies among others the existing definition of the limit value of the quasistatic guiding force. At present, the majority of new vehicles has a problem to keep this limit value of the force acting on the outer wheel of the guiding wheelset in small and very small-radius curves. For purposes of the assessment of the interaction between vehicles and track, this Code defines a new quantity - so-called quasistatic loading force, as well. The assessment of the guiding behaviour of the new four-axled diesel-electric locomotive Class 744.0 CZ LOKO by simulations performed at the Detached Branch of the Jan Perner Transport Faculty in Česká Třebová is demonstrated in this paper.