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Multiscale entropy applications for complexity analysis of two-phase flow

Rafałko Gabriela, Mosdorf Romuald, Grzybowski Hubert, Dzienis Paweł, Górski Grzegorz

Archives of Thermodynamics

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2024

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Vol. 45, no 2

83--90

EN

Two-phase flow in channels of small dimensions is often a non-stationary process, the nature of such flow is oscillatory. Due to small channel dimensions, high heat flux, parallel channels interactions, pressure and temperature oscillations, the character of the phenomena occurring during boiling is complex. The changes of the measured signals are observed in different time scales. In order to examine in detail two-phase flow parameters changes, many acquisition devices are often installed. This solution becomes challenging concerning mini and microchannel heat-exchangers due to space limitation and modifications of an experimental setup. This paper presents a novel application of multiscale entropies for spatial and temporal analysis of two-phase flow based on only one registered parameter. This analysis is performed based on pixel brightness changes in photo frames registered by a high speed camera during two-phase flow. The spatial changes of pixel brightness are observed on single frames and temporal changes are examined using a set of frames (in time). The Composite Multiscale Sample Entropy is applied to identify two-phase flow patterns and to analyze the complexity of phase distribution. Using Multivariate Multiscale Sample Entropy the most rapid changes of phase distribution in a multichannel heat exchanger are determined.

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Periodic trends in two-phase flow through a vertical minichannel: wavelet and multiscale entropy analyses based on digital camera data

Górski Grzegorz, Mosdorf Romuald, Rysak Andrzej, Litak Grzegorz

Acta Mechanica et Automatica

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2019

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Vol. 13, no. 1

51--56

EN

By changing the air and water flow relative rates in the two-phase (air-water) flow through a minichannel, we observe aggregation and partitioning of air bubbles and slugs of different sizes. An air bubble arrangement, which show non-periodic and periodic patterns. The spatiotemporal behaviour was recorded by a digital camera. Multiscale entropy analysis is a method of measuring the time series complexity. The main aim of the paper was testing the possibility of implementation of multiscale entropy for two-phase flow patterns classification. For better understanding, the dynamics of the two-phase flow patterns inside the minichannel histograms and wavelet methods were also used. In particular, we found a clear distinction between bubbles and slugs formations in terms of multiscale entropy. On the other hand, the intermediate region was effected by appearance of both forms in non-periodic and periodic sequences. The preliminary results were confirmed by using histograms and wavelets.

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Pozyskiwanie danych do modelowania przepływu wód podziemnych na obszarze leja depresji BOT KWB Bełchatów S.A.

Szczepiński Jacek, Górski Grzegorz, Stachowicz Zbigniew, Szczepanik Paweł

Geologos

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2006

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Vol. 10

263--270

EN

The paper presents problems related to data availability for the ground water flow modeling in the region of the Bełchatów lignite mine. The U.S. Geological Survey’s program MODFLOW was used to reconstruct past and to present the existing conditions in the aquifers within the Bełchatów lignite mine influence. Ground water and surface water monitoring system which enables to assess changes of hydrodynamical and hydrological conditions in the region as well as methods which make possible to obtain additional hydrogeological parameters were discussed. The means in which data are collected and processed were presented.