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A computer-aided visualization method for flow analysis

FLOW MEASUREMENT AND INSTRUMENTATION 2014年 38卷 1-8页

作者： Bizjan, Benjamin Orbanic, Alen Sirok, Brane Kovac, Bostjan Bajcar, Tom Kavkler, Iztok Abelium Doo Ljubljana 1000 Slovenia Inst Math Phys & Mech Ljubljana 1000 Slovenia Univ Ljubljana Fac Math & Phys Ljubljana 1000 Slovenia Univ Ljubljana Fac Mech Engn Ljubljana 1000 Slovenia

This paper presents a non-contact method for velocity field calculation from a series of images containing illuminated planar layer of fluid with a pollutant mixed in. Velocity field is calculated using a model similar to optical flow based on the advection-diffusion equation. The model which was also implemented into our software, ADMflow, is evaluated on different sets of synthetic images. Calculated velocity fields are in a good agreement with the true velocity fields, mostly deviating by less than 10% in magnitude and 1 degrees in flow direction. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Advection-diffusion equation computer-aided visualization Dense flow field Image velocimetry Optical flow

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Unsupervised cluster analyses of character networks in fiction: Community structure and centrality

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KNOWLEDGE-BASED SYSTEMS 2019年 163卷 800-810页

作者： Chen, R. H. -G. Chen, C. -C. Chen, C. -M. Natl Taiwan Normal Univ Dept Phys Taipei Taiwan Univ British Columbia Dept Comp Sci Vancouver BC Canada Minnan Normal Univ Minnan Cultural Res Inst Zhangzhou Peoples R China Longyan Univ Res Inst Cent Soviet Dist Longyan Peoples R China

We present an integrated approach to cluster and visualize character networks in fiction with the aid of computational and statistical methods. An unsupervised clustering algorithm, minimum span clustering (MSC), was applied to cluster fictional characters at various characteristic resolutions based on their activities in the novel. As a demonstration, we study the character network in Dream of the Red Chamber, the greatest novel in Chinese literature. The character network of the novel is found to exhibit properties of scale-free and small-world networks. Based on unsupervised cluster analyses, we construct and visualize the community structure of the network, and find a three-tiered structure of core, secondary, and peripheral characters. By treating the network as a weighted graph, we further analyze the centralities of characters to determine their importance in the network, and find that betweenness centrality, as a measure of characters' control over the flow of the narrative, is differentiated from other centrality measures for Dream of the Red Chamber. We believe that these analytic methods provide beneficial tools for applications such as autonomous novel writing. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Unsupervised clustering computer-aided visualization Social network Community structure detection Centrality measures

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Non-contact method for analysis of cavitating flows

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ULTRASONICS 2017年 81卷 178-186页

作者： Bilus, Ignacijo Bizjan, Benjamin Lesnik, Luka Sirok, Brane Pecnik, Bostjan Dular, Matevz Univ Maribor Fac Mech Engn Smetanova Ulica 17 SLO-2000 Maribor Slovenia Univ Ljubljana Fac Mech Engn Askerceva 6 Ljubljana 1000 Slovenia Gorenje Dd Partizanska 12 Velenje 3503 Slovenia

This paper presents a novel non-contact method for simultaneous analysis of pressure and velocity conditions in cavitating flows. The method (implemented in our software ADMflow) is based on high-speed camera flow visualization and was evaluated in an experiment with ultrasonically induced acoustic cavitation of different intensities. Attached cavitation with clearly visible cavitation structures occurred on the tip of an ultrasonic probe immersed in distilled water. Using the high-speed imaging data, pressure fluctuations were calculated by a computer-aided algorithm based on the Brennen's theory of cavitation cloud kinematics and a modified version of the Rayleigh-Plesset equation. Reference measurements of pressure pulsations were conducted by a hydrophone installed at the bottom of the liquid container. The analysis of cavitation structure dynamics was complemented by calculation of velocity fields from the imaging data, the algorithm for which is based on the advection-diffusion equation. Calculated pressure fluctuations were analyzed in the spatial, temporal and spectral domain. Presented results indicate a strong correlation between the fields of velocity and pressure fluctuations during the growth and collapse of cavitation structures. A comparison of time series and power spectra demonstrates that our cavitation analysis method is in a reasonably good agreement with results of the reference measurement methods and can therefore be used for non-contact analysis of pressure and velocity conditions in cavitating flows. (C) 2017 Published by Elsevier B.V.

关键词： Acoustic cavitation Sonotrode Pressure measurement Hydrophone computer-aided visualization Image velocimetry

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Flow Image Velocimetry Method Based on Advection-Diffusion Equation

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STROJNISKI VESTNIK-JOURNAL OF MECHANICAL ENGINEERING 2014年第7-8期60卷 483-494页

作者： Bizjan, Benjamin Orbanic, Alen Sirok, Brane Bajcar, Tom Novak, Lovrenc Kovac, Bostjan Univ Ljubljana Fac Mech Engn Ljubljana 61000 Slovenia Abelium doo Res & Dev Ljubljana Slovenia Univ Ljubljana Fac Math & Phys Ljubljana 61000 Slovenia

This paper presents a non-contact method for velocity field calculation from a series of fluid flow images with illuminated planar layer of the flow and a mixed-in pollutant for flow visualization. The velocity field is calculated using a model similar to optical flow that is based on the. advection-diffusion equation. The model is evaluated using a set of synthetic airfoil flow visualization images generated by a combination of computational fluid dynamics and inverse advection-diffusion equation approaches. The calculated velocity fields are in a good agreement with the true velocity fields.

关键词： computer-aided visualization image velocimetry dense flow field calculation optical flow advection-diffusion equation computational fluid dynamics

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Mineral wool melt fiberization on a spinner wheel

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CHEMICAL ENGINEERING RESEARCH & DESIGN 2014年第1期92卷 80-90页

作者： Sirok, Brane Bizjan, Benjamin Orbanic, Alen Bajcar, Tom Univ Ljubljana Fac Mech Engn Ljubljana 1000 Slovenia Abelium Doo Ljubljana 1119 Slovenia

In this paper, the formation of mineral wool fibres has been studied on a real industrial production process. Parametric dependence of the melt film structural dynamics on the spinner wheel rotational frequency was investigated. The results presented indicate the presence of the melt instability that is formed as a complex quasi-periodic oscillation of the structures on the melt film surface. In addition to the melt oscillations which coincide with the rotating frequency of the spinner wheel and its higher harmonics, aperiodic melt structures also appear These structures result from the Taylor instability, which is inherent to liquid movement and is one of the basic mechanisms of the formation of melt ligaments that solidify into mineral wool fibres. Based on the results, a phenomenological model for structural instability as a function of the wheel rotational frequency was formed, indicating a characteristic influence of melt film dynamics on the fibre formation and indirectly, on the quality of the end Product. (C) 2013 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers.

关键词： Mineral wool Fluid mechanics Fibres computer-aided visualization Experimental modelling

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Quantification of Flow Kinematics Using computer-aided visualization

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STROJNISKI VESTNIK-JOURNAL OF MECHANICAL ENGINEERING 2009年第4期55卷 215-223页

作者： Bajcar, Tom Sirok, Brane Eberlinc, Matjaz Univ Ljubljana Fac Mech Engn Ljubljana 1000 Slovenia

The paper presents a study of the ability of the visualization methods to measure velocity field in the fluid flow from the concentration field of a passive tracer that is introduced to the fluid. The method is based on the advection diffusion equation. A sequence of successive flow images was processed to obtain the required unknown terms. Concentration of the passive tracer vas acquired through greyscale intensity on images at chosen measurement points. Standard numerical procedures were applied to obtain spatial- and time derivatives of the passive tracer concentration. The method was tested in all experiment with an air jet flowing out of a pipe, where the velocity field in a jet was measured with a hotwire anemometer. Comparison of the results of both methods shows good agreement, albeit with certain deviations that are a consequence of simplified approach of the visualization method. The results prove the suitability of the visualization method for quantitative measurements of flow kinematics. Further studies and improvements of the method could provide a simple and relatively cheap yet reliable tool not only for preliminary assessment of the flow velocity field, but also for velocity, measurements in complex flow structures. (c) 2009 Journal of Mechanical Engineering. All rights reserved.

关键词： computer-aided visualization flow kinematics velocity measurment

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A computer-aided visualization Tool for Stochastic Theory Education in Water Resources Engineering

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computer APPLICATIONS IN ENGINEERING EDUCATION 2009年第4期17卷 398-411页

作者： Schwenk, Jonathan Hossain, Faisal Huddleston, David Tennessee Technol Univ Dept Civil & Environm Engn Cookeville TN 38505 USA

In this paper, we propose and demonstrate the proof-of-concept for a computer-aided visualization tool for stochastic theory education in water resources engineering. Using Java Native Interfacing, the tool can wrap a space-time stochastic model written in any computer language and also not require any specific language compiler during tool usage. This feature also allows the tool to be implemented very easily on any configuration of currently used classroom PCs. We also gauged the merit of a computer-aided visualization tool in the classroom by conducting a survey of the civil engineering (CE) curricula of US universities, Questionnaires were distributed to the instructors via an online survey. Eighty-four percent of the universities surveyed were found to offer a general semblance of stochastic theory education in their curriculum for CE. A similar percentage of the total 241 courses that we initially surveyed were found to be available at the graduate level, while 4.5% and 11.5% were either dual-listed or undergraduate-level courses, respectively. Forty universities were found to have complete (integrated) courses dedicated to stochastic theory education (or a near-relative related discipline). 11.2% (27) of these courses were relevant to water resources engineering, while only 9.5% (23 courses) were related to surface water hydrology. Only 62.5% of instructors were active users of some kind of computer-aided visualization tools for classroom instruction. All instructors believed that a rapid visualization system to represent the effect of input (i.e., an aspect of stochastic theory) on output (i.e., application or representation of variability) would enhance the technology as a learning tool Surveyed instructors were unanimous in their willingness to integrate such an instruction tool for teaching theory using real-world examples of water resources engineering. However, 42% felt that such a tool would need to be user-friendly and graphically very attractive in o

关键词： water resources engineering stochastic theory survey curriculum computer-aided visualization

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Sedimentation efficiency of two continuously operating circular settling tanks with different inlet- and outlet arrangements

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CHEMICAL ENGINEERING JOURNAL 2011年 178卷 217-224页

作者： Bajcar, Tom Steinman, Franci Sirok, Brane Preseren, Tanja Univ Ljubljana Fac Mech Engn Ljubljana 1000 Slovenia Univ Ljubljana Fac Civil & Geodet Engn Ljubljana 1000 Slovenia

The paper presents an experimental study of suspension flow patterns and velocity field inside two types of circular settling tanks with continuous operation. The two tanks differ in inlet- and outlet configurations. Research was focused on the influence of flow field on the sedimentation efficiency of both settling tanks. Experiment was carried out on a settling tank sections made of plexi-glass that represented radial slices of prototype circular settling tanks. Kinematic flow properties inside settling tank sections were determined by computer-aided visualization in order to analyse the whole instantaneous flow field at once. Sedimentation efficiency was assessed by measurements of inlet- and effluent suspension concentrations. Pronounced density current evolved in both tanks, which under certain conditions enhanced sedimentation. Flow field showed qualitative changes during operation and proved to be significantly dependent on average suspension density in the inner chamber of the settling tank. Some important properties of the flow field could also be reconstructed from the spatial distribution of the remaining sludge. Centrally fed settling tank with peripheral effluent generally performed better in terms of sedimentation efficiency mainly clue to insufficient height of the effluent baffle in the peripherally fed settling tank. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Circular settling tank Sedimentation computer-aided visualization Flow field Density current

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Influence of flow field on sedimentation efficiency in a circular settling tank with peripheral inflow and central effluent

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CHEMICAL ENGINEERING AND PROCESSING-PROCESS INTENSIFICATION 2010年第5期49卷 514-522页

作者： Bajcar, Tom Gosar, Leon Sirok, Brane Steinman, Franci Rak, Gasper Univ Ljubljana Fac Mech Engn Ljubljana 1000 Slovenia Inst Water Republ Slovenia Ljubljana 1000 Slovenia Univ Ljubljana Fac Civil & Geodet Engn Ljubljana 1000 Slovenia

The paper presents an experimental study of suspension flow patterns and velocity field inside a circular settling tank with continuous operation. Research was focused on the impact of a specific flow pattern on the sedimentation efficiency of the prototype settling tank. The latter differed from a common circular settling tank in that it was peripherally fed and had the central draw-off. Experiment was carried out on a settling tank section made of plexiglass and represented a radial slice of a prototype settling tank. The flow field and local suspension concentration was determined by computer-aided visualization. Sedimentation efficiency was assessed relatively by comparison of the amount of settled particles (sludge height measurements) between different types of flow in a certain time period of the settling tank operation. Results showed that there were two types of flow in the settling tank that were initiated by a horizontal or vertical inflow from the distribution ring. The type of inflow (horizontal or vertical) was a function of the suspension height in the settling tank. Significant differences in sedimentation efficiency were observed between both types of flow, particularly at lower inlet suspension concentrations. Horizontal inflow proved to be less efficient in terms of settling. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Settling tank Sedimentation computer-aided visualization Flow field

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Numerical and experimental investigation of axial fan with trailing edge self-induced blowing

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FORSCHUNG IM INGENIEURWESEN-ENGINEERING RESEARCH 2009年第3期73卷 129-138页

作者： Eberlinc, Matjaz Sirok, Brane Hocevar, Marko Dular, Matevz Univ Ljubljana Fac Mech Engn Ljubljana 1000 Slovenia

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. In the present paper, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. They enable the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the trailing edge slots at the tip of the blade. The study of the influence of internal flow on the flow field of axial fan and the modifications of aerodynamic characteristics of the axial fan have been made. The numerical and experimental results show a comparison of integral and local characteristics of the axial fan with the internal flow, compared to characteristics of a geometrically equivalent fan without internal flow. The experimental results of local characteristics were performed with a five-hole probe and computer-aided visualization. A reduction of adverse flow conditions near the trailing edge at the tip of the blade was achieved, as well as boundary layer reduction on the blade suction side and the reduction of flow separation. The introduction of self-induced blowing led to the preservation of the direction of external flow, defined by blade geometry, and enabled maximal local energy conversion. The integral characteristic reached higher degree of efficiency.

关键词： Axial fan Hollow blade Self-induced blowing Numerical simulation Five-hole probe computer-aided visualization

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