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Linear and Non-Linear Rheological Properties of Foods
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Ozlem C. Duvarci, Gamze Yazar, Hulya Dogan, Jozef L. Kokini
Several measurements and visualization techniques have been utilized to experimentally validate numerical simulation results and gain a deeper understanding of the processes involved in flow and mixing, such as measurements of velocities, at either specific points or through an entire plane, pressure and residence time. Flow visualization can be achieved using acid-base reactions or the diffusion of a dye in a flow and then using imaging techniques to capture the flow patterns. Velocity measurement has traditionally been carried out at point locations using Laser Doppler Velocimetry (LDA). Velocity measurements through entire planar cross-sections are done using Particle Image or Tracking Velocimetry (PIV) and Planar Laser-Induced Fluorescence (PLIF).
Computer-Aided Flow Visualization
Published in Wen-Jei Yang, Handbook of Flow Visualization, 2018
Computer-aided flow visualization is a rather broad category that refers to the use of digital computer processing in combination with various display devices to enhance our ability to visually understand fluid flow behavior. This description clearly broadens the scope of what is considered “conventional” flow visualization (i.e., two-dimensional images of an optically detectable medium or property translating in an experimental flow field) to include the three-dimensional reconstruction of space- and time-dependent behavior, the visual display of reduced quantitative property data, and the generation of “flow visualization” images from analytically generated data. This chapter reviews a number of general techniques that have been developed to facilitate computer-aided flow visualization. As the reader will note, most techniques discussed are adaptations from the well-developed general fields of image processing and computer-aided design/graphics. Since the techniques employed for computer-aided flow visualization are essentially generic to these other fields, the present section covers only general approaches. For specific details of the computational mechanics and appropriate hardware/ software systems, the reader should consult the literature in the appropriate field [e.g., 1–4]. The reader is also referred to Chaps. 16–19 in this handbook, which address the details of image acquisition and processing in more depth.
Flow Visualization By Direct Injection
Published in Richard J. Goldstein, Fluid Mechanics Measurements, 2017
Thomas J. Mueller, F. N. M. Brown
Throughout the history of aerodynamics and hydrodynamics there has been a great interest in making flow patterns visible. The visualization of complex flows has played a unique role in the improvement of our understanding of fluid dynamic phenomena. Flow visualization has been used to verify existing physical principles and, in the process, has led to the discovery of numerous flow phenomena. In addition to obtaining qualitative global pictures of the flow, the possibility of acquiring quantitative measurements without introducing probes, which invariably disturb the flow, has provided the necessary incentive for the development of a large number of visualization techniques. Although clean air and water are transparent, smoke or other particles in air, and dye or other particles in water, provide the necessary contamination for flow visualization. For very practical reasons, the study of fluid mechanics was concerned with the flow of water and other liquids until relatively recent times. Man’s interest in flight, however, pointed out the necessity of visualizing air flows to understand the mechanics of objects moving through the air. Many substances have been used to visualize the flow of air and water. In air, smoke, helium bubbles, dust particles, and even glowing iron particles, have been used; in water, a variety of dyes, particles, neutrally buoyant spheres, and both air and hydrogen bubbles have been employed.
A study of drag reduction with textile roughness on a cyclist model
Published in The Journal of The Textile Institute, 2022
X. Y. Hsu, Jiun-Jih Miau, T. H. Ku, J. J. Chen, W. C. Yuan, Y. H. Lai, Y. R. Chen, Y. J. Chen, C. H. Tseng, C. H. Chen, S. S. Jan, Y. S. Ciou, Y. Chen, C. W. Chiu
Flow visualization experiments were performed using the dye-streak, oil-film and ink-dot methods. For the dye-streak method, the dye was introduced upstream from the model to reveal the flow motions in the region of interest. The outer diameter of the dye injection tube was 1 mm, that the Reynolds number based on the freestream velocity and the diameter of the tube was about 60. Note that the disturbance generated by the injection tube resulted in a wake behind the tube. Under the flow condition, the disturbance generated is categorized as a laminar wake (Roshko, 1954; Van Dyke, 1982), whose velocity deficit would be diffused by the viscous effect mainly. Thus, the disturbance produced could be regarded as insignificant to flow motion. For the oil-film method, a white water-color paint was applied on the surface of the model. After the model was placed in the flow for a length of time until most of the paint material on the windward side of the model was carried away, the flow separation lines would be revealed clearly. As for the ink-dot flow visualization technique, the same water-color paint was applied on the model surface in dots at the pre-determined grid points. Until the dotted paint dried for a certain length of time in the air, the model was placed in the test section. As a result, a limiting streamline pattern would be emerged from the appearance of the ink-dots due to the viscous effect of flow near the surface.
Transfer function-based 2D/3D interactive spatiotemporal visualizations of mesoscale eddies
Published in International Journal of Digital Earth, 2020
Fenglin Tian, Lingqi Cheng, Ge Chen
Particle-tracing methods are one of the standard techniques for flow visualization. A fundamental problem is the selection of appropriate seed points for particle tracing to visualize all important features of a flow. One solution to this problem is texture-based visualization (Cabral and Leedom 1993), which presents several major issues, such as aliasing artefacts and artificial blurring. This problem may be even more serious in 3D flow representations. In contrast, geometry-based methods (Turk and Banks 1996) produce geometric representations with ensured accuracy. To express flow fields via this method, several obstacles must be overcome, including uniform streamline distributions, computational complexity, occlusion and cluttering. Many approaches have been proposed to solve these problems, although these new achievements have not been applied in marine flow fields, especially the 3D structure of mesoscale eddies.
Development of an oscillation-based technology for the removal of colloidal particles from water: CFD modeling and experiments
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Eran Halfi, Alumah Arad, Asher Brenner, David Katoshevski
The introduction of a colored dye into the agitated tank may facilitate superior flow visualization (Brown et al., 2004). To that end, the use of a tank with a level indicator in the form of a scale attached to the tank wall can provide valuable quantitative information on the observed height of colored dye. In the present study, dye was injected into the agitated tank at measured depths to study the flow patterns and to compare the dye injection results with those of the simulated flow field. Note that in the conventional jar test configuration, particles do not settle, but rather, they remain suspended in the liquid phase as a result of the flow field generated in the jar test configuration. In fact, a similar configuration is used for solid particle fluidization in cylindrical tanks (Marshall & Bakker, 2004; Nagata, 1975). Therefore, separation of the solid particles from the liquid phase requires an additional sedimentation tank.