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Recirculation Surfaces for flow visualization

IEEE TRANSACTIONS ON visualization AND COMPUTER GRAPHICS 2019年第1期25卷 946-955页

作者： Wilde, Thomas Rossl, Christian Theisel, Holger Univ Magdeburg Visual Comp Grp Magdeburg Germany

We present a formal approach to the visual analysis of recirculation in flows by introducing recirculation surfaces for 3D unsteady flow fields. Recirculation surfaces are the loci where massless particle integration returns to its starting point after some variable, finite integration. We give a rigorous definition of recirculation surfaces as 2 -manifolds embedded in 5D space and study their properties. Based on this we construct an algorithm for their extraction, which searches for intersections of a recirculation surface with lines defined in 3D. This reduces the problem to a repeated search for critical points in 3D vector fields. We provide a uniform sampling of the search space paired with a surface reconstruction and visualize results. This way, we present the first algorithm for a comprehensive feature extraction in the 5D flow map of a 3D flow. The problem of finding isolated closed orbits in steady vector fields occurs as a special case of recirculation surfaces. This includes isolated closed orbits with saddle behavior. We show recirculation surfaces for a number of artificial and real flow data sets.

关键词： flow visualization recirculation unsteady flow

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flowLLM: Large language model driven flow visualization

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Visual Informatics 2025年

作者： Zilin Li Weihan Zhang Jun Tao School of Computer Science and Engineering Sun Yat-sen University 132 Outerring East Road Higher Education Mega Center Guangzhou 510006 Guangdong China

flow visualization is an essential tool for domain experts to understand and analyze flow fields intuitively. In the past decades, various interactive techniques were developed to customize flow visualization for exploration. However, these techniques usually use specifically designed graphical interfaces, requiring considerable learning and usage effort. Recently, flowNL Huang et al., (2023) introduces a natural language interface to reduce the effort, but it still struggles with natural language ambiguities due to the lack of domain knowledge and provides limited ability to understand the context in dialogues. To address these issues, we propose an explorative flow visualization powered by a large language model that interacts with users. Our approach leverages an extensive dataset of flow-related queries to train the model, enhancing its ability to interpret a wide range of natural language expressions and maintain context over multi-turn interactions. Additionally, we introduce an advanced dialogue management system that supports interactive continuous communication between users and the system. Our empirical evaluations demonstrate significant improvements in user engagement and accuracy of flow structure extraction. These enhancements are crucial for expanding the applicability of flow visualization systems in real-world scenarios, where effective and intuitive user interfaces are paramount.

关键词： flow visualization Natural language interface Large language model Interactive exploration

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Dye advection without the blur: ML-based flow visualization

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Visual Informatics 2025年

作者： Sebastian Künzel Daniel Weiskopf VISUS University of Stuttgart Allmandring 19 Stuttgart 70569 Baden-Württemberg Germany

Semi-Lagrangian texture advection (SLTA) enables efficient visualization of 2D and 3D unsteady flow. The major drawback of SLTA-based visualizations is numerical diffusion caused by iterative texture interpolation. We focus on reducing numerical diffusion in techniques that use textures sparsely populated by solid blobs, such as typically in dye advection. A ReLU-based model architecture is the foundation of our ML-based approach. Multiple model configurations are trained to learn a performant interpolation model that reduces numerical diffusion. Our evaluation investigates the models’ ability to generalize concerning the flow and length of the advection process. The model with the best tradeoff between the computational effort to compute, quality of the result, and generality of application is found to be single-layer ReLU-based. This model is further analyzed and explained in-depth and improved using symmetry constraints. Additionally, a metamodel is fitted to predict single-layer ReLU model parameters for advection processes of any length. The metamodel removes the need for any prior training when applying our technique to a new scenario. Additionally, we show that our model is compatible with Back and Forth Error Compensation and Correction to improve the quality of the advection result further. We demonstrate that our model shows excellent diffusion reduction properties in typical examples of 3D steady and unsteady flow visualization. Finally, we utilize the strong diffusion reduction capabilities of our model to compute dye advection with exponential decay, a novel method that we introduce to visualize the extent and evolution of unsteadiness in both 2D and 3D unsteady flow.

关键词： flow visualization 2D and 3D unsteady flow Semi-Lagrangian texture advection Machine learning ReLU

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Experimental analysis of cavitation in a centrifugal pump using acoustic emission, vibration measurements and flow visualization

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EUROPEAN JOURNAL OF MECHANICS B-FLUIDS 2019年 75卷 300-311页

作者： Mousmoulis, Georgios Karlsen-Davies, Nilla Aggidis, George Anagnostopoulos, Ioannis Papantonis, Dimitrios Natl Tech Univ Athens Lab Hydraul Turbomachines Sch Mech Engn Iroon Polytechniou 9 Athens 15780 Greece Univ Lancaster Dept Engn Renewable Energy Grp Lancaster LA1 4YW England

The continuously increasing industrial productivity has resulted in a great breakthrough in the field of maintenance on centrifugal pumps in order to ensure their optimum operation under different operating conditions. One of the important mechanisms that affect the steady and dynamic operation of a pump is cavitation, which appears in the low static pressure zone formed at the impeller entrance region. This paper investigates the inception and development of cavitation in three different impellers of a laboratory centrifugal pump with a Plexiglas casing, using flow visualization, vibration and acoustic emission measurements. The aim of this study is the development of an experimental tool that detects cavitation in different impellers and the further understanding of the effects of blade geometry in cavitation development. The results show that the geometrical characteristics of the impeller affect cavitation development and behavior, while an acoustic emission sensor and an accelerometer can be applied for successfully detecting the onset of this mechanism. (C) 2018 Elsevier Masson SAS. All rights reserved.

关键词： Cavitation in centrifugal pumps Diagnostics and prognostics flow visualization Noise and vibration measurements

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A CNN-based shock detection method in flow visualization

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COMPUTERS & FLUIDS 2019年 184卷 1-9页

作者： Liu, Yang Lu, Yutong Wang, Yueqing Sun, Dong Deng, Liang Wang, Fang Lei, Yan Natl Univ Def Technol Coll Comp Changsha Hunan Peoples R China China Aerodynam Res & Dev Ctr Computat Aerodynam Inst Mianyang Peoples R China Sun Yat Sen Univ Sch Data & Comp Sci Guangzhou Guangdong Peoples R China China Aerodynam Res & Dev Ctr State Key Lab Aerodynam Mianyang Peoples R China Chongqing Univ Sch Big Data & Software Engn Chongqing Peoples R China

As one of the main technologies of flow visualization, shock detection plays a key role in feature identification and has been intensively studied. However, existing methods take too much execution time to meet the requirement of post-processing on large-scale Computational Fluid Dynamics (CFD) flow field data. To address this problem, in this paper, we propose a detection method for shock waves based on Convolutional Neural Networks (CNN) and design a novel loss function to optimize the detection results. In specific, the proposed method samples small patches from flow field data, and trains a detection network which includes multiple convolutional layers. This network is responsible for generating shock values and finding the location of shock waves. Compared with the existing shock detection methods which are not based on deep learning, our method has great advantages in detection time. Compared with the ones based on deep learning, our method gives a better detection result of shock waves. Extensive experimental results demonstrate the good generalization of the proposed method on many datasets. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： flow visualization Shock detection CFD flow field CNN

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flow visualization in a coronary network with microvascular obstruction (MVO) using a multiscale in-vitro benchtop model 23

Flow visualization in a coronary network with microvascular ...

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23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2019

作者： Thirugnanasambandam, Mirunalini Wüthrich, Christian Frey, Sabrina Heeb, Peter Nef, Cornelia Bernard, André Obrist, Dominik ARTORG Center for Biomedical Engineering Research University of Bern Switzerland Institute for Micro- and Nanotechnology University of Applied Sciences Buchs NTB Switzerland

ISBN: (纸本)9781733419000

The main goal of this study is to better understand the effect of MVO [1] on coronary microcirculation using a multiscale in-vitro benchtop model, which accurately represents 1) the coronary microvasculature in healthy (normal) myocardium and 2) in disease states, particularly with MVO. The primary outcome of this study is a better understanding of micro-coronary flow under normal and pathological conditions, through a series of flow visualization experiments. © 2019 CBMS-0001.

关键词： flow visualization

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Experimental Analysis of Natural Convection and flow visualization in an Asymmetrically Heated Open Vertical Channel

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JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS 2019年第5期11卷 051020页

作者： Cherif, Yassine Sassine, Emilio Zalewski, Laurent Souidi, Kaies Lassue, Stephane Univ Artois Lab Civil Engn & Geoenvironm LGCgE F-62400 Bethune France Lebanese Univ Lab Appl Phys LPA Fac Sci Fanar Campus Beirut Lebanon Univ Artois Dept Chim IUT Bethune CS20819 F-62408 Bethune France

An experimental device was designed to perform the thermal and dynamic study of natural convection airflow in an open vertical channel. The two side walls of the vertical channel are made of Plexiglas allowing the visualization of the flow via the particle image velocimetry (PIV) method. For the two other vertical walls, one is heated at a constant temperature, and the other is insulated with a 9-cm thick polystyrene insulation. The dynamic characterization of convection is carried out by nonintrusive measurements (Ply), and thermal phenomena are analyzed using nonintrusive heat flux instrumentation (simultaneous temperature and velocity measurements have been carried out across the channel at different elevations). Moreover, this study deals with the influence of the Rayleigh number on the measured vertical velocity profiles as well as the thermal flux densities recorded along the heated wall. To do this, different values of the modified Rayleigh numbers were considered in the interval with the channel aspect ratio of A = 5 and A = 12.5. The obtained Nusselt number values have been compared successfully with those of the literature. The impacts of the Rayleigh number and the aspect ratio on the velocity profiles and the convective and radiative heat transfer have been examined.

关键词： Heat flux Natural convection Particulate matter Rayleigh number Sensors Temperature flow (Dynamics) flow visualization

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Development of a flow visualization Borescope and a Two-Phase flow Probe for Aeroengine Transmission Gears

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JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME 2019年第9期141卷 091013页

作者： Arisawa, Hidenori Shinoda, Yuji Noguchi, Yoshiyuki Goi, Tatsuhiko Banno, Takahiko Akahori, Hirofumi Kawasaki Heavy Ind Co Ltd 1-1 Kawasaki Cho Akashi Hyogo 6738666 Japan

To reduce power losses due to oil flows in aeroengine gearboxes, the oil flows should be visualized and measured. In this study, we develop a flow visualization borescope that qualitatively visualizes oil flows along with a two-phase flow probe that quantitatively measures the oil/air ratio and flow velocity. The flow visualization borescope comprises a 16-mm-diameter pipe. Within the pipe, an air purge passage for removing oil mist and a borescope are integrated with an illumination laser and optical lenses, enabling clear, high-speed photography. The two-phase probe consists of a 5-mm-diameter pipe with a 1-mm-diameter measurement hole and an internal pressure adjustment pipe. The borescope and flow probe were demonstrated using a shrouded spur gear with a peripheral speed of 100 m/s and oil supply of 20 l/min. flow visualization at 30,000 fps revealed that oil outflow from the shroud opening spreads turbulently over the entire width of the opening. Measurements of the oil/air ratio and flow velocity using the two-phase flow probe revealed a thin oil-rich layer on the shroud wall and showed that the flow speed is lower than the gear peripheral speed. The measurement equipment used herein would be easy to install in a gearbox and is therefore expected to be applied in actual aeroengine gearboxes.

关键词： Calibration flow (Dynamics) Probes Mechanical drives visualization Pressure flow visualization Gears Two-phase flow

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Investigation of flow visualization around linked tall buildings with circular sections

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BUILDING AND ENVIRONMENT 2019年 153卷 60-76页

作者： Kim, Bubryur Tse, K. T. Yoshida, Akihito Chen, Zengshun Pham Van Phuc Park, Hyo Seon Hong Kong Univ Sci & Technol Dept Civil & Environm Engn Kowloon Clear Water Bay Hong Kong Peoples R China Yonsei Univ Ctr Struct Hlth Care Technol Bldg Seoul 120749 South Korea Tokyo Polytech Univ Wind Engn Res Ctr Atsugi Kanagawa Japan Chongqing Univ Sch Civil Engn Chongqing Peoples R China Shimizu Corp Res Inst Tokyo Japan Yonsei Univ Dept Architectural Engn Seoul 120749 South Korea

This study investigated the wind environment around buildings by visualizing the wind flow patterns of linked buildings (LB), in which two buildings with circular sections are attached through linking members. Particle image velocimetry was used to measure the wind flows around LB models with different gap distances between the buildings. Proper orthogonal decomposition (POD) analysis was applied to identify velocity and vorticity patterns. The results showed that when the two buildings have a side-by-side arrangement (alpha = 0 degrees), and the gap distance is small, the POD using velocity indicates a single vortex street and biased flow in the gap, whereas that using vorticity suggests a contracted flow in the gap. When the gap distance is large, two independent vortex streets appear in the first mode of both POD, with the POD using vorticity confirming the presence of re-circulation zones in the wake region. In a tandem arrangement (alpha = 0 degrees), the shear layer street occurring in the upstream building affects the entire LB system, and the POD analysis using vorticity shows that the shear layer cannot surround the downstream building if the gap distance is large. The link, gap distance, and elevation have little impact on the flow patterns when alpha = 0 degrees. However, these factors affect the flow patterns when alpha = 0 degrees. In addition, when the gap distance is equal to two-thirds of the building breadth and alpha = 0 degrees, the two shear layer streets joined behind the space between the two buildings and produced the maximum mean wind speed around the building compared to other cases.

关键词： Linked tall building Tall building Particle image velocimetry Proper orthogonal decomposition Wind environment around tall building flow visualization

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Experimental flow visualization study using particle image velocimetry in a helical coil steam generator with changing lateral pitch geometry

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2019年 133卷 756-768页

作者： Delgado, M. Hassan, Y. A. Anand, N. K. Texas A&M Univ Dept Nucl Engn College Stn TX 77843 USA Texas A&M Univ Dept Mech Engn College Stn TX 77843 USA

A full size section from a helical coil steam generator with five concentric coils with a helix-to-rod diameter ratio of 127 was constructed to study shell side fluid flow. The geometry has a constant transverse pitch ratio (a = 2.96), but changing lateral pitch ratio (b = 0.6-0.9) across the image planes of interest. Particle Image Velocimetry (PIV) with an index of refractive matching fluid technique was used to capture images of the flow behavior at these planes of interest. Experiments focused on visualizing cross-flow at the entrance and center regions of the test section at each plane of interest at Re = 8500. Analysis was conducted to study average vertical and transverse velocity components, vorticity and streamline fields for the shell side flow. Averaged results showed characteristic flow structures common of staggered cross-flow behavior within tube and shell heat exchangers. Select linear heights based on rod geometry show a consistent average velocity pattern across all three planes of interest regardless of lateral pitch ratio. Average velocity components do not suggest a correlation with lateral pitch ratio as previous studies with constant lateral pitch ratio designs have shown. The constantly changing geometry of this particular helical coil steam generator design affects the development and dependence of vortex formation and motion. Published by Elsevier Ltd.

关键词： PIV flow visualization Helical coil steam generator Tube and shell heat exchanger Cross-flow

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