PIV measurement of cross flow in a rod bundle assisted by telecentric optics and matched index of refraction

Xiong, Juntao; Qu, Wenhai; Wu, Zenghui; Xu, Cheng

doi:10.1016/j.anucene.2018.06.024

Cited by 32 publications

(3 citation statements)

References 12 publications

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“…Commonly used model materials are fluorinated ethylene propylene (FEP), polyvinyl acetate (PVAc), polystyrene (PS), and polymethyl methacrylate (PMMA). Among them, FEP has poor transmittance and causes substantial decay of the laser flux [45,46]; PVAc has a low softening point (38 °C) and is unsuitable for medium-and high-temperature tests; PS has poor toughness and is difficult to machine. PMMA, with its good transmittance and easy processing, is the most used model material in flow field visualization experiments.…”

Section: Flow Field Visualization Measurement Technologymentioning

confidence: 99%

Review of Refractive Index-Matching Techniques of Polymethyl Methacrylate in Flow Field Visualization Experiments

Fan

et al. 2023

International Journal of Energy Research

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The development of modern computational fluid dynamics (CFD) technology provides many preliminary references for experimental design. In addition, the CFD calculation results verified by experiments can display enormous microdata in areas that are difficult to measure through experiments, as an extension. This can make measurements more reasonable and effective, shorten measurement times, and save manpower and capital significantly. Therefore, it is vital to verify the accuracy of CFD calculation results, especially in cases of complex structures and multiphase flows. The results of model tests can be utilized in a prototype experiment by properly designing a test section and selecting a working fluid if the Reynolds similarity criterion is met. Optical measurement technology is a noninvasive measurement method, and the impact on the flow field can be almost negligible. It is advised to use transparent materials and prepare a refractive index-matching (RIM) fluid to obtain a good optical path. Polymethyl methacrylate (PMMA) is widely used in flow field visualization experiments because of its good light transmission and mechanical strength. This review is aimed at introducing the current status of different flow field measurement techniques; moreover, it is intended to help the readers to become more familiar with the principles of RIM, the characteristics, applications, and usage suggestions of various RIM fluid schemes of PMMA, providing references for researchers in the design, preparation, and conducting stages of flow field visualization measurement experiments. This review is divided into five sections. In the introduction section, Chapter 1, relevant research developments and related results of flow field measurements are presented, followed by the innovations and benefits of this paper. In Chapter 2, the flow field visualization measurements are presented and a derivation is shown. In Chapter 3, some RIM fluid schemes of PMMA and their applications are given, which are very valuable for peers. In Chapter 4, the measurement and analysis of some physical properties are described. In the RIM process, it is necessary to focus on the RI, density, dynamic viscosity, compatibility, stability, safety, and cost of RIM fluids. These factors greatly impact the accuracy of experimental results, experimental progress, and safety of the experimenters. Based on the analysis and our practical experience, some suggestions are given for preparing and using RIM fluids. In the conclusion section, Chapter 5, the results and practical implications of this paper are summarized.

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Section: Flow Field Visualization Measurement Technologymentioning

confidence: 99%

Review of Refractive Index-Matching Techniques of Polymethyl Methacrylate in Flow Field Visualization Experiments

Fan

et al. 2023

International Journal of Energy Research

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“…It is commonly referred to as the standard fixed focal-length lens. The telecentric lens erases perspective errors [24][25][26]. The hypercentric lens inverts the normal perspective to see almost the entire surface of a three-dimensional object.…”

Section: Introductionmentioning

confidence: 99%

The effects of camera focus and sensor exposure on accuracy using computer vision

Moru¹

2022

Nig. J. Tech.

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As industrial camera become smarter, due to the increase in supporting algorithms, so the quality of data produced offers higher precision and accuracy of industrial inspection operations. This paper aims to focus on the accurate effect of camera focus on a calibration process under the influence of different sensor exposure and degrees of focus. A computer vision methodology is used to determine the effects of different sensor exposures and at different degrees of camera focus. Endocentric and telecentric lenses are used to acquire images, and a comparative analysis was achieved using the least square method. A sample of 2176 images was used to generate the population for analysis. The analysis showed that the human eye cannot visually determine a hundred percent focus of an image. This means that it is difficult to determine when an image is 100% focused from when it is 95% focused. The result from the experiment showed that as the camera focus tends towards 100% the calibration error decreases, with a minimum calibration error of 0.06 pixels, leading to the conclusion that the developed method achieved a calibration error accuracy with the most effective camera sensor exposure and the camera focus.

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“…Dominguez-Ontiveros et al's and Conner et al's experimental data has been included in the CFD benchmark database (Conner et al, 2013b). With the aid of telecentric optic Xiong et al (2018a) measured the 2D cross flow in a 5 × 5 rod bundle with 2D PIV. More recently, Qu et al (2019a,b,c) carried out the high-fidelity PIV measurement in rod bundle with split mixing vanes.…”

Section: Introductionmentioning

confidence: 99%

Validation for CFD Simulation in Rod Bundles With Split-Vane Spacer Grids Based on LDA Measurement

Xiong

2020

Front. Energy Res.

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Laser Doppler anemometry (LDA) measurement of axial flow velocity and pressure drop measurement has been carried out in a 5 × 5 rod bundle installed with two split-mixing-vane grids. The measured results are utilized to validate the CFD simulation. The realizable and non-linear k-ε turbulence model is utilized in the CFD computation, while the two-layer wall treatment is employed with both models. Mesh sensitivity investigation shows that the pressure drop is weakly affected by local mesh refinement in the spacer grid, while its effect on the velocity in the near wake of spacer grid is apparent. The validation shows that prediction on the mean axial velocity is relatively poor in the near wake of the spacer grid where the measured result shows relatively smooth distribution of axial velocity. Refinement of mesh in the spacer grid eliminates some peaks for the non-linear model. Comparing with the effect of mesh refinement, the difference caused by the turbulence models is relatively weak in the near wake region. In the far-wake region it is still difficult to judge which model shows definite superiority to the other. For pressure drop, prediction of non-linear k-ε is closer to the experiment.

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PIV measurement of cross flow in a rod bundle assisted by telecentric optics and matched index of refraction

Cited by 32 publications

References 12 publications

Review of Refractive Index-Matching Techniques of Polymethyl Methacrylate in Flow Field Visualization Experiments

Review of Refractive Index-Matching Techniques of Polymethyl Methacrylate in Flow Field Visualization Experiments

The effects of camera focus and sensor exposure on accuracy using computer vision

Validation for CFD Simulation in Rod Bundles With Split-Vane Spacer Grids Based on LDA Measurement

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