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1

Studies on velocity fields around the cavitation vortices generated by the model of a rotating blade

Suchecki W.

Polish Maritime Research

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2018

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nr 2

66--70

EN

The elimination of hazards caused by cavitation phenomena is an important issue to be considered in the design of process equipment including flow machinery. These hazards are: cavitation erosion, efficiency decrease as well as vibration and noise. One of the most intensive and dangerous forms of cavitation is vortex cavitation that accompanies the operation of hydraulic machines in which components comprised of rotating blades are applied. Velocity fields around cavitation vortices generated by the model of a propeller blade were experimentally studied in a cavitation tunnel. Flow images were recorded using a high-speed camera and processed using particle image velocimetry (PIV) complemented with computer-aided techniques that had been developed for the purpose of this research. These techniques included the removal of image distortions on the basis of a calibration mask, determination of instantaneous velocity distributions and removal of air-bubble traces from flow images. Experimental studies result examples were presented in the form of velocity fields determined in the longitudinal plane as well as in three transverse planes remote from the blade. Instabilities of the cavitating vortex stream and of the local liquid-flow velocity in its surrounding were detected. The effect of the angle of attack of propeller blade on the instability of the vortex stream and the effect of the presence of the cavitating vortex kernel on the local velocities of the surrounding liquid, were determined.

2

Droplet Impact in Icing Conditions – Experimental Study for WE 540

Lizer T., Remer M., Sobieraj G., Psarski M., Pawlak D., Celichowski G.

Archive of Mechanical Engineering

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2017

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Vol. LXIV, nr 2

165--175

EN

The work presents investigation on the water droplet impingement at a substrate with three different surface coating. The experiments are carried out for two temperatures of the surface: 23 degrees centigrade (room temperature) and 10 degrees centigrade. The water droplet contact is recorded via ultra-fast camera and simultaneously via fast thermographic camera. The wetting properties are changing for subzero temperatures of substrates.

3

Separation of isochromatics and isoclinics phasemaps for the photoelastic technique with use phase shifting and a large number of high precision images

Magalhaes C. A., Neto P. S., Magalhaes Jr P. A. A. P. A. A., de Barcellos C. S.

Metrology and Measurement Systems

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2013

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Vol. 20, nr 1

127-138

EN

Digital photoelasticity is an important optical metrology follow-up for stress and strain analysis using full-field digital photographic images. Advances in digital image processing, data acquisition, procedures for pattern recognition and storage capacity enable the use of the computer-aided technique in automation and facilitate improvement of the digital photoelastic technique. The objective of this research is to find new equations for a novel phase-shifting method in digital photoelasticity. Some innovations are proposed. In terms of phaseshifting, only the analyzer is rotated, and the other equations are deduced by applying a new numerical technique instead of the usual algebraic techniques. This approach can be used to calculate a larger sequence of images. Each image represents a pattern and a measurement of the stresses present in the object. A decrease in the mean errors was obtained by increasing the number of observations. A reduction in the difference between the theoretical and experimental values of stresses was obtained by increasing the number of images in the equations for calculating phase. Every photographic image has errors and random noise, but the uncertainties due to these effects can be reduced with a larger number of observations. The proposed method with many images and high accuracy is a good alternative to the photoelastic techniques.

4

An Experimental and Numerical Study of Tip Vortex Cavitation

Szantyr J. A., Flaszyński P., Suchecki W., Alabrudziński S.

Polish Maritime Research

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2011

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nr 4

14-22

EN

The article presents the results of the research project concerning tip vortex cavitation. This form of cavitation is very important in operation of many types of rotary hydraulic machines, including pumps, turbines and marine propellers. Tip vortex cavitation generates noise, vibration and erosion. It should be eliminated or significantly limited during the design of these types of machines. The objective of the project was to develop an accurate and reliable method for numerical prediction of tip vortex cavitation, which could serve this purpose. The project consisted of the laboratory experiments and numerical calculations. Inthe laboratory experiments tip vortex cavitation was generated behind a hydrofoil in the cavitation tunneland the velocity field around the cavitating kernel was measured using the Particle Image Velocimetry method. Measurements were conducted in three cross-sections of the cavitating tip vortex for a number ofangles of attack of the hydrofoil and for several values of the cavitation index. In the course of numerical calculations two commercial CFD codes were used: Fluent and CFX. Several available approaches to numerical modeling of tip vortex cavitation were applied and tested, attempting to reproduce the experimental conditions. The results of calculations were compared with the collected experimental data. The most promising computational approach was identified. Keywords:

5

A method for the accurate numerical prediction of the tip vortices shed from hydrofoils

Flaszyński P., Szantyr J. A., Dymarski P., Kraskowski M.

Polish Maritime Research

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2010

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nr 2

10-17

EN

The possibly accurate numerical prediction of the detailed structure of vortices shed from the tips of hydrofoils is an important element of the design process of marine propellers. The concentrated tip vortices are responsible for the propeller cavitation erosion and acoustic emission. The purpose of the project described in this paper was to develop the numerical method for prediction of the tip vortex structure. In the course of the project the numerical calculations were confronted with the results of experimental measurements. This led to creation of the specific method of construction of the computational grid and to selection of the optimum turbulence model. As a result the reliable method for the accurate numerical prediction of the concentrated tip vortices for different hydrofoil geometry and flow conditions has been developed and validated. This method enables elimination of the unfavourable phenomena related to the tip vortices in the course of the propeller design calculations.

6

An experimental and numerical study of the vortices generated by hydrofoils

Szantyr J. A., Biernacki R., Flaszyński P., Dymarski P., Kraskowski M.

Polish Maritime Research

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2009

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nr 3

11-17

EN

The article presents the results of the research project concerning the process of formation of the tip vortices shed from hydrofoils of different geometry in different flow conditions. Three hydrofoils resembling the contemporary marine propeller blades have been selected for the study. The experimental part of the project consisted of the LDA measurements of the velocity field in three cross-sections of the vortex generated by the hydrofoils in the cavitation tunnel. The numerical part of the project consisted of calculations of the corresponding velocity field by means of three computer codes and several selected turbulence models. The comparative analysis of the experimental and numerical results, leading to the assessment of the accuracy of the numerical methods, is included.

7

Metody badania biodegradacji materiałów polimerowych. Cz. II. Techniki eksperymentalne

Bajer K., Kaczmarek H.

Polimery

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2007

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T. 52, nr 1

13-18

PL

Na podstawie przeglądu bieżącej literatury opisano liczne techniki eksperymentalne stosowane obecnie w laboratoryjnych badaniach biodegradacji polimerów i ich kompozycji a także zespół cech, których zmiana pozwala na ocenę przebiegu i wydajności tego procesu. Szczególną uwagę poświęcono metodzie respirometrycznej polegającej na oznaczaniu ilości ditlenku węgla wydzielającego się podczas biologicznego rozkładu polimerów. Dopiero stosowanie wzajemnie uzupełniających się metod prowadzi do wyjaśnienia skomplikowanych mechanizmów biodegradacyjnych i przewidywania "czasu życia" tworzyw sztucznych.

EN

On the basis of recent literature review the numerous experimental techniques used currently in laboratory investigations of biodegradation of polymers and their compositions were presented. The set of features which changes allow evaluating the course and yield of biodegradation process has been described as well. The special attention has been paid to respirometric method basing on the determination of carbon dioxide evolving during the biological decomposition of polymers. Only the application of the methods complementing each other leads to the explanation of complicated mechanisms of biodegradation and predictions of plastics' working times.

8

Zmiany w kształceniu inżynierów XXI wieku na przykładzie Stanów Zjednoczonych: czego możemy się nauczyć na tym przykładzie?

Misiołek W., Misiołek Z.

Rudy i Metale Nieżelazne

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2005

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R. 50, nr 3

120-125

PL

Polskie uczelnie stoją przed koniecznością zmian w systemie kształcenia inżynierów i prowadzenia badań naukowych. Konieczność zmian jest wymuszana zmianami w zewnętrznym świecie oraz jest podyktowana argumentami natury finansowej. Ciągła optymalizacja metod kształcenia spowodowała wiele zmian w systemie nauczania akademickiego, podnosząc jednocześnie ich poziom i wprowadzając oszczędności w wielu częściach świata. Od polskich uczelni zależy teraz, jaką drogę rozwoju one wybiorą i jacy absolwenci będą opuszczać ich mury w najbliższej przyszłości. W artykule przeanalizowano zmiany w dydaktyce wprowadzone ma wydziałach inżynierskich w Lehigh University w Bethlehem w stanie Pensylwania w Stanach Zjednoczonych Ameryki. Wskazano również potencjalne możliwości rozwoju tak w kształceniu, jak i w badaniach naukowych w zakresie metalurgii i inżynierii materiałowej.

EN

The Polish technical universities face the necessity to change a system for educating engineers and conducting scientific research. This necessity is extorted by the changes taking place in external world and by economic factors. In many parts of the world, permanent optimisation of teaching methods resulted in many changes in academic education system leading to higher level of education and considerable savings. It is now up to the Polish universities to make a choice of a way of further development and to decide on what level will represent the future graduates from these universities. In this paper analysis of the changes implemented in a teaching system at the engineering departments of the Lehigh University in Bethlehem, Pensylvania, USA, is presented. Potential possibilities of development with an account of both teaching and research aspects in the range of metallurgy and materials science have been indicated.

9

Dust formation in low-pressure discharges

Stoffels E., Stoffels W., Kroesen G.

Elektronika : konstrukcje, technologie, zastosowania

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2001

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Vol. 42, nr 3

33-34

EN

Dust formation in various low-pressure systems, like interstellar space, upper parts of atmosphere, and laboratory gas discharges, has been recognised as a fascinating and rich in consequences phenomenon. This article gives a brief survey of one aspect of the vast research area of dusty plasmas. Dust particles attract much attention in surface processing, like etching of semiconductor elements or deposition of various coatings. These technologies are of major concern in industry, and they involve low-pressure plasmas operated in active gases. Much effort has been invested in elucidating dust formation mechanisms in these systems. Here, a silane (SiH4) plasma used for amorphous silicon deposition in solar cell technology is treated as an example. Several experimental techniques for dust detection in vacuum systems are presented and dust formation mechanism in a silane discharge is described.

PL

Formowanie mikroskopijnych pyłów w systemach niskociśnieniowych jest obecnie bardzo popularnym przedmiotem badań w astronomii, fizyce atmosfery, a także w fizyce plazmy. Niskociśnieniowe wyładowania elektryczne znajdują szerokie zastosowania w nowoczesnej technologii obróbki materiałów, np. w trawieniu elementów półprzewodnikowych oraz w napylaniu cienkich warstw. Formowanie pyłów w tych aktywnych chemicznie plazmach ma znaczny wpływ zarówno na jakość modyfikowanej powierzchni jak i na wydajność obróbki plazmowej. W wyniku długotrwałych badań większość mechanizmów formowania pyłów w niskociśnieniowych plazmach została wyjaśniona. W artykule zaprezentowano metody wykrywania pyłów w reaktorach próżniowych oraz mechanizm formowania pyłów w silanie (SiH4). Wyładowania elektryczne w silanie są powszechnie stosowane w napylaniu amorficznych warstw krzemowych przy produkcji fotokomórek.