Combining high-speed planar PIV and motion tracking of a flexible cylinder in cross-flow

Most modeling studies investigating the flow dynamics in vegetation canopies are limited to rigid models as proxies for vegetation elements. However, most canopies embody some degree of structural flexibility, resulting in aeroelastic mechanisms coupling the motion of the vegetation with the surrounding flow. Studies addressing flexible canopies typically quantify either the flow or the plant motion independently, thus missing the instantaneous coupling between turbulent stresses and structural deformations. Few experiments have been devoted to measuring both quantities simultaneously. Okamoto and Nezu (2009) utilized a combined PIV-PTV technique to capture both flow and canopy motion. However, only the motion of the stem tips was captured, as opposed to the deformation of the entire stem. Py et al. (2006) employed digital image correlation (DIC) to quantify the motion of crop canopies using in-field images. However, the wind itself was not measured across the domain. The present work presents an experimental technique that can be utilized to study the flow–structure interaction in flexible canopies, and that could be extended to other flexible and/or moving objects. High-speed PIV data of the flow surrounding an idealized canopy element, consisting of a flexible cylinder, together with the corresponding displacement field throughout the cylinder were simultaneously obtained combining fluorescent imaging and refractive index matching (RIM).

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DPIV Around a Flexible Circular Cylinder Undergoing Cross-Flow Forced Oscillations

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2012-78535 ◽

2012 ◽

Author(s):

Francisco J. Huera-Huarte ◽

Zafar A. Bangash

Keyword(s):

Circular Cylinder ◽

High Speed ◽

Continuous Wave ◽

Laser Sheet ◽

Cross Flow ◽

Forced Oscillations ◽

Flow Visualisation ◽

Flexible Cylinder ◽

Image Velocimetry ◽

Structural Mode

This research is motivated by early experiments [1, 2], in which the main time consistent flow structures in the wake of a flexible oscillating circular cylinder were studied. We have now investigated the wake of a circular cylinder undergoing forced vibrations, by using Planar Digital Particle Image Velocimetry (DPIV) and long exposure photographs for flow visualisation. The focus is given to the node to anti-node transition when the cylinder oscillates in its second structural mode. A flexible cylinder is supported by a structure consisting of a frame that includes a motor that drives a shaft, that actuates a pusher connected to the cylinder at two points, through a crank slider mechanism. We are able to produce forced oscillations of the cylinder, either in its first mode when the pushers are in phase, or in its second mode if the pushers are configured out-of-phase. We have used a high speed camera together with a continuous wave laser, to image seeding particles being illuminated by the laser sheet, at two different heights along the length of the cylinder: the node and the anti-node. We have also produced long exposure images of the particles leading to flow visualisation.

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A Polymer-Gel Eye-Phantom for 3D Fluorescent Imaging of Millimetre Radiation Beams

10.20944/preprints201807.0597.v1 ◽

2018 ◽

Author(s):

Leonard Luthjens ◽

Tiantian Yao ◽

John Warman

Keyword(s):

Uv Light ◽

Thin Sheet ◽

Vitreous Body ◽

Fluorescent Imaging ◽

Polymer Gel ◽

Tertiary Butyl ◽

Tomographic Images ◽

Index Matching ◽

Refractive Index Matching ◽

Radiation Beams

Abstract: We have filled a 24 mm diameter glass sphere with a transparent polymer-gel that is radio-fluorogenic, i.e. it becomes (permanently) fluorescent when irradiated, with an intensity proportional to the local dose deposited. The gel consists of >99.9% tertiary-butyl acrylate (TBA) pre-polymerized to ~15% conversion, and ~100 ppm maleimido-pyrene (MPy). Its dimensions and physical properties are close to those of the vitreous body of the human eye. We have irradiated the gel with a 3 mm diameter, 200 kVp X-ray beam with a dose rate of ~1 Gy/min. A 3D (video) view of the beam within the gel has been constructed from tomographic images obtained by scanning the sample through a thin sheet of UV light. To minimize optical artifacts, the cell was immersed in a square tank containing a refractive-index-matching medium. The 20%-80% penumbra of the beam was determined to be ~0.4 mm. The research was a preparatory investigation of the possibility of using the method to monitor the millimetre diameter proton pencil beams used in ocular radiotherapy.

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A Polymer-Gel Eye-Phantom for 3D Fluorescent Imaging of Millimetre Radiation Beams

Polymers ◽

10.3390/polym10111195 ◽

2018 ◽

Vol 10 (11) ◽

pp. 1195 ◽

Cited By ~ 3

Author(s):

Leonard Luthjens ◽

Tiantian Yao ◽

John Warman

Keyword(s):

Uv Light ◽

Thin Sheet ◽

Three Dimensional ◽

Vitreous Body ◽

Fluorescent Imaging ◽

Polymer Gel ◽

Tertiary Butyl ◽

Tomographic Images ◽

Index Matching ◽

Refractive Index Matching

We have filled a 24 mm diameter glass sphere with a transparent polymer-gel that is radio-fluorogenic, i.e., it becomes (permanently) fluorescent when irradiated, with an intensity proportional to the local dose deposited. The gel consists of >99.9% tertiary-butyl acrylate (TBA), pre-polymerized to ~15% conversion, and ~100 ppm maleimido-pyrene (MPy). Its dimensions and physical properties are close to those of the vitreous body of the human eye. We have irradiated the gel with a 3 mm diameter, 200 kVp X-ray beam with a dose rate of ~1 Gy/min. A three-dimensional (3D) (video) view of the beam within the gel has been constructed from tomographic images obtained by scanning the sample through a thin sheet of UV light. To minimize optical artefacts, the cell was immersed in a square tank containing a refractive-index-matching medium. The 20–80% penumbra of the beam was determined to be ~0.4 mm. This research was a preparatory investigation of the possibility of using this method to monitor the millimetre diameter proton pencil beams used in ocular radiotherapy.

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Selection of model liquid with refractive index matching for visualization of internal flow in a scaled atomizer model

EPJ Web of Conferences ◽

10.1051/epjconf/201921302070 ◽

2019 ◽

Vol 213 ◽

pp. 02070

Author(s):

Marcel Sapík ◽

Milan Malý ◽

Jan Jedelský ◽

Graham Wigley ◽

Ondřej Cejpek

Keyword(s):

Refractive Index ◽

High Speed ◽

Laser Doppler Anemometry ◽

Internal Flow ◽

Model Material ◽

Chemical Effect ◽

High Speed Imaging ◽

Model Liquid ◽

Index Matching ◽

Refractive Index Matching

A scaled transparent modular model of pressure-swirl (PS) atomizer was prepared from cast PMMA (Poly(methyl methacrylate), Perspex™, Plexiglas™) with the aim to achieve a better understanding of internal flow and subsequent spray formation. Because of use of high-speed imaging and Laser Doppler Anemometry (LDA) the working liquid had to be selected with respect of a refractive index matching (RIM) with the atomizer material. The liquid should be colourless and chemically non-aggressive to the model material with suitable viscosity to achieve the Reynolds number of the internal flow of the original atomizer. Froude number should be high enough to neglect the influence of gravity on the flow. An extensive search for transparent liquids and materials of enlarged models was made with a focus on RIM in performed experiments. Several liquids were chosen, and their chemical effect on PMMA was tested. Despite the successful tests that proved the liquid suit the case, the model material was damaged and the tests proved to be insufficient. For this reason, the tests were modified to better involve the stress of the bolted model. It turned out that a force effect (bolt in the thread, pre-stressed bolt connection) on the material has a significant influence on the acceleration of the chemical effect. The internal flow was examined using a high-speed camera with several liquids.

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Analyzing Deterioration in Optical Performance of Fiber Connections with Refractive Index Matching Material Using Incorrectly Cleaved Fiber Ends

IEICE Transactions on Communications ◽

10.1587/transcom.e96.b.2206 ◽

2013 ◽

Vol E96.B (9) ◽

pp. 2206-2212

Author(s):

Mitsuru KIHARA ◽

Yuichi YAJIMA ◽

Hiroshi WATANABE

Keyword(s):

Refractive Index ◽

Optical Performance ◽

Index Matching ◽

Refractive Index Matching

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Experimental Measurement of In-Plane Rolling Nonpneumatic Tire Vibrations Using High-Speed Imaging

Tire Science and Technology ◽

10.2346/tire.18.470101 ◽

2019 ◽

Vol 47 (3) ◽

pp. 196-210

Author(s):

Meghashyam Panyam ◽

Beshah Ayalew ◽

Timothy Rhyne ◽

Steve Cron ◽

John Adcox

Keyword(s):

High Speed ◽

Image Correlation ◽

Dynamic Mode Decomposition ◽

Dynamic Mode ◽

High Speed Imaging ◽

Correlation Algorithm ◽

Mode Decomposition ◽

Series Of Experiments ◽

Plane Deformations ◽

Dominant Frequencies

ABSTRACT This article presents a novel experimental technique for measuring in-plane deformations and vibration modes of a rotating nonpneumatic tire subjected to obstacle impacts. The tire was mounted on a modified quarter-car test rig, which was built around one of the drums of a 500-horse power chassis dynamometer at Clemson University's International Center for Automotive Research. A series of experiments were conducted using a high-speed camera to capture the event of the rotating tire coming into contact with a cleat attached to the surface of the drum. The resulting video was processed using a two-dimensional digital image correlation algorithm to obtain in-plane radial and tangential deformation fields of the tire. The dynamic mode decomposition algorithm was implemented on the deformation fields to extract the dominant frequencies that were excited in the tire upon contact with the cleat. It was observed that the deformations and the modal frequencies estimated using this method were within a reasonable range of expected values. In general, the results indicate that the method used in this study can be a useful tool in measuring in-plane deformations of rolling tires without the need for additional sensors and wiring.

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Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽

10.3390/s21051602 ◽

2021 ◽

Vol 21 (5) ◽

pp. 1602

Author(s):

Ángel Molina-Viedma ◽

Elías López-Alba ◽

Luis Felipe-Sesé ◽

Francisco Díaz

Keyword(s):

Modal Analysis ◽

Energy Absorption ◽

High Speed ◽

Operational Modal Analysis ◽

Modal Identification ◽

Image Correlation ◽

Composite Panel ◽

Impact Excitation ◽

Full Field ◽

The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

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Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions

Energies ◽

10.3390/en14040797 ◽

2021 ◽

Vol 14 (4) ◽

pp. 797

Author(s):

Stefan Hoerner ◽

Iring Kösters ◽

Laure Vignal ◽

Olivier Cleynen ◽

Shokoofeh Abbaszadeh ◽

...

Keyword(s):

Flow Field ◽

High Speed ◽

Cross Flow ◽

Speed Ratio ◽

Fluid Structure Interactions ◽

Dimensional Parameter ◽

Fluid Structure ◽

Passive Flow Control ◽

Tidal Turbines ◽

Tidal Turbine

Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.

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Hybrid Mamdani Fuzzy Rules and Convolutional Neural Networks for Analysis and Identification of Animal Images

Computation ◽

10.3390/computation9030035 ◽

2021 ◽

Vol 9 (3) ◽

pp. 35

Author(s):

Hind R. Mohammed ◽

Zahir M. Hussain

Keyword(s):

Neural Networks ◽

Convolutional Neural Networks ◽

High Speed ◽

Moving Objects ◽

Real Life ◽

Fuzzy Rules ◽

High Rate ◽

Moving Images ◽

Animal Images

Accurate, fast, and automatic detection and classification of animal images is challenging, but it is much needed for many real-life applications. This paper presents a hybrid model of Mamdani Type-2 fuzzy rules and convolutional neural networks (CNNs) applied to identify and distinguish various animals using different datasets consisting of about 27,307 images. The proposed system utilizes fuzzy rules to detect the image and then apply the CNN model for the object’s predicate category. The CNN model was trained and tested based on more than 21,846 pictures of animals. The experiments’ results of the proposed method offered high speed and efficiency, which could be a prominent aspect in designing image-processing systems based on Type 2 fuzzy rules characterization for identifying fixed and moving images. The proposed fuzzy method obtained an accuracy rate for identifying and recognizing moving objects of 98% and a mean square error of 0.1183464 less than other studies. It also achieved a very high rate of correctly predicting malicious objects equal to recall = 0.98121 and a precision rate of 1. The test’s accuracy was evaluated using the F1 Score, which obtained a high percentage of 0.99052.

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