T. Ikami, Koji Fujita, H. Nagai, Yutaro Matsuda, Y. Egami
Pressure-Sensitive-Paint (PSP) can measure a surface pressure field. Recently, fast-PSPs have been developed and applied to a visualization of the unsteady aerodynamic phenomenon. In general, the amount of unsteady aerodynamic visualization data is enormous. The Dynamic Mode Decomposition (DMD) technique can efficiently extract spatial and dynamic characteristics from enormous data. However, some data acquisition conditions for correctly discussing the flow field using DMD are still unclear. In particular, it is important to know the appropriate sampling frequency for specific aerodynamic phenomena. In this study, Karman vortexes in the wake of a square cylinder are visualized by the fast-PSP. Moreover, by using the unsteady PSP data, the time resolution of the input data is changed, and the influence on the DMD analysis for the Karman vortices is investigated. We find that the time resolution does not affect the flow structure of the DMD mode. On the other hand, the dynamic characteristics of the flow structure approach the true value when the time resolution is increased.
{"title":"Investigation of Data Acquisition Conditions for Dynamic Mode Decomposition in Unsteady PSP Measurement","authors":"T. Ikami, Koji Fujita, H. Nagai, Yutaro Matsuda, Y. Egami","doi":"10.3154/tvsj.41.11","DOIUrl":"https://doi.org/10.3154/tvsj.41.11","url":null,"abstract":"Pressure-Sensitive-Paint (PSP) can measure a surface pressure field. Recently, fast-PSPs have been developed and applied to a visualization of the unsteady aerodynamic phenomenon. In general, the amount of unsteady aerodynamic visualization data is enormous. The Dynamic Mode Decomposition (DMD) technique can efficiently extract spatial and dynamic characteristics from enormous data. However, some data acquisition conditions for correctly discussing the flow field using DMD are still unclear. In particular, it is important to know the appropriate sampling frequency for specific aerodynamic phenomena. In this study, Karman vortexes in the wake of a square cylinder are visualized by the fast-PSP. Moreover, by using the unsteady PSP data, the time resolution of the input data is changed, and the influence on the DMD analysis for the Karman vortices is investigated. We find that the time resolution does not affect the flow structure of the DMD mode. On the other hand, the dynamic characteristics of the flow structure approach the true value when the time resolution is increased.","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116869377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Water jet accompanied with explosive droplets splashing under the various conditions was observed by flow visualization method as a basic study on the droplets control to develop the novel atomization system. Water jet that spouted from nozzle attached to bottom of air pressurized water reservoir naturally draws air from free surface of water in the reservoir and becomes a gas-liquid mixture jet when the free surface of water in the reservoir makes low into some height from the bottom with time elapsed. The gas-liquid mixture jet has made periodic radial splash of water droplets. In this study, the nozzle length and ejection pressure were changed and the droplets splashing phenomenon was analyzed by using high speed visualization and pressure measurement. As a result, it was found that the frequency of aligned droplets was changed due to difference in the nozzle length.
{"title":"Effect of Nozzle Length on Jet Occurring Explosive Droplets Splashing","authors":"Tsutomu Ishido, H. Hasegawa","doi":"10.3154/tvsj.40.17","DOIUrl":"https://doi.org/10.3154/tvsj.40.17","url":null,"abstract":"ABSTRACT Water jet accompanied with explosive droplets splashing under the various conditions was observed by flow visualization method as a basic study on the droplets control to develop the novel atomization system. Water jet that spouted from nozzle attached to bottom of air pressurized water reservoir naturally draws air from free surface of water in the reservoir and becomes a gas-liquid mixture jet when the free surface of water in the reservoir makes low into some height from the bottom with time elapsed. The gas-liquid mixture jet has made periodic radial splash of water droplets. In this study, the nozzle length and ejection pressure were changed and the droplets splashing phenomenon was analyzed by using high speed visualization and pressure measurement. As a result, it was found that the frequency of aligned droplets was changed due to difference in the nozzle length.","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134087014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A sound is generated when a bubble detaches from a nozzle installed in the water. The sound emission is known as a monopole sound source. This frequency is expressed by Minnaert's equation, and many studies have been conducted on bubble deformation, detachment, and coalescence. However, many physical processes still involve the unsettled phenomena regarding the mechanical behavior of the sound source. In this study, we report that the breathing mode was directly analyzed by an optical measurement, following the simulation of the breathing mode by CFD in the previous report. The present super-resolution measurement gives a sufficient result to discuss the oscillatory motion of bubble surface where the displacement of the bubble is so small that the normal observation cannot capture. In the present research, the numerical simulation of the measurement method was conducted, and measurement of the vibration disc were performed as the preliminary experiments. Thus, the optimum measurement parameters were extracted, and they were applied to the displacement measurement of the breathing mode of the bubble. The results show a good agreement with the CFD ones.
{"title":"Validation of a super-resolution measurement using frequency filtering technique and optical displacement analysis of bubble surface in breathing mode oscillation","authors":"T. Oku, H. Hirahara, D. Kang","doi":"10.3154/TVSJ.41.1","DOIUrl":"https://doi.org/10.3154/TVSJ.41.1","url":null,"abstract":"A sound is generated when a bubble detaches from a nozzle installed in the water. The sound emission is known as a monopole sound source. This frequency is expressed by Minnaert's equation, and many studies have been conducted on bubble deformation, detachment, and coalescence. However, many physical processes still involve the unsettled phenomena regarding the mechanical behavior of the sound source. In this study, we report that the breathing mode was directly analyzed by an optical measurement, following the simulation of the breathing mode by CFD in the previous report. The present super-resolution measurement gives a sufficient result to discuss the oscillatory motion of bubble surface where the displacement of the bubble is so small that the normal observation cannot capture. In the present research, the numerical simulation of the measurement method was conducted, and measurement of the vibration disc were performed as the preliminary experiments. Thus, the optimum measurement parameters were extracted, and they were applied to the displacement measurement of the breathing mode of the bubble. The results show a good agreement with the CFD ones.","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134328731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Characteristics of flow structure due to circularization of straight open channel corner","authors":"Katsutoshi Watanabe, Yuya Mito, H. Une, K. Asai","doi":"10.3154/tvsj.42.1","DOIUrl":"https://doi.org/10.3154/tvsj.42.1","url":null,"abstract":"","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124664528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"PIV計測とニューラルネットワークを活用した粉体噴流プロセスのモデル化検討","authors":"Yuki Furutani","doi":"10.3154/tvsj.43.15","DOIUrl":"https://doi.org/10.3154/tvsj.43.15","url":null,"abstract":"","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116968214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Simultaneous measurement of particle position and displacement in depth by depth-from-defocus using time-series color images Miki DEGUCHI, Shigeru MURATA and Yohsuke TANAKA ABSTRACT This paper presents a method for simultaneous measurement of particle position and displacement in depth by depth-from-defocus using time series color images. This method enables us to obtain the particle information for 3D-PIV by using a single color camera. To improve the depth measurement accuracy, three differently blurred images are simultaneously captured as RGB color images and the depth information is estimated from the three images with a neural network considering in-plane position. In performance tests, we numerically and experimentally evaluate the measurement accuracy of particle position and displacement in depth. The results of depth position by neural network show that the RMS error decreases to 65% of that by a calibration line. The results of depth displacement from three color images show that the RMS error decreases to 24% of that from only one color image, corresponding to 9.5% for maximum displacement 2 mm.
{"title":"Simultaneous measurement of particle position and displacement in depth by depth-from-defocus using time-series color images","authors":"M. Deguchi, S. Murata, Yohsuke Tanaka","doi":"10.3154/TVSJ.39.19","DOIUrl":"https://doi.org/10.3154/TVSJ.39.19","url":null,"abstract":"Simultaneous measurement of particle position and displacement in depth by depth-from-defocus using time-series color images Miki DEGUCHI, Shigeru MURATA and Yohsuke TANAKA ABSTRACT This paper presents a method for simultaneous measurement of particle position and displacement in depth by depth-from-defocus using time series color images. This method enables us to obtain the particle information for 3D-PIV by using a single color camera. To improve the depth measurement accuracy, three differently blurred images are simultaneously captured as RGB color images and the depth information is estimated from the three images with a neural network considering in-plane position. In performance tests, we numerically and experimentally evaluate the measurement accuracy of particle position and displacement in depth. The results of depth position by neural network show that the RMS error decreases to 65% of that by a calibration line. The results of depth displacement from three color images show that the RMS error decreases to 24% of that from only one color image, corresponding to 9.5% for maximum displacement 2 mm.","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131239357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Performance Improvement of Digital Holographic Particle Measurement by Suppression of Speckle-like Noise and Particle Image Elongation in Depth Direction Masatsugu MURAYAMA, Shigeru MURATA and Yohsuke TANAKA ABSTRACT In this paper, we show that the performance of digital holographic particle measurement is improved by suppressing speckle-like noise and particle image elongation in the depth direction. We use a deconvolution method to reduce the speckle-like noise in the background by reconstructing the image while excluding background light and shortening the particle image elongation in the depth direction. First, we compare the number of detected particles and detection accuracy between the proposed and conventional methods in numerical experiment to evaluate the performance of the present method. Then we verify the feasibility of the present method in real flow measurement by confirming that the movement of the particles in 3D space is successfully captured in observation experiments.
{"title":"Performance Improvement of Digital Holographic Particle Measurement by Suppression of Speckle-like Noise and Particle Image Elongation in Depth Direction","authors":"Masatsugu Murayama, S. Murata, Yohsuke Tanaka","doi":"10.3154/tvsj.40.9","DOIUrl":"https://doi.org/10.3154/tvsj.40.9","url":null,"abstract":"Performance Improvement of Digital Holographic Particle Measurement by Suppression of Speckle-like Noise and Particle Image Elongation in Depth Direction Masatsugu MURAYAMA, Shigeru MURATA and Yohsuke TANAKA ABSTRACT In this paper, we show that the performance of digital holographic particle measurement is improved by suppressing speckle-like noise and particle image elongation in the depth direction. We use a deconvolution method to reduce the speckle-like noise in the background by reconstructing the image while excluding background light and shortening the particle image elongation in the depth direction. First, we compare the number of detected particles and detection accuracy between the proposed and conventional methods in numerical experiment to evaluate the performance of the present method. Then we verify the feasibility of the present method in real flow measurement by confirming that the movement of the particles in 3D space is successfully captured in observation experiments.","PeriodicalId":246197,"journal":{"name":"Transactions of the Visualization Society of Japan","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132649198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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