Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream

Flow features, due to air injection through multiple vents on the surface of a hydrofoil inclined at an angle with respect to the free-stream in a cavitation tunnel, are presented here. The hydrofoil, with a chord length, <i>c</i>, is oriented at the angle of inclination, <inline-form...

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Autores principales:	Kiseong Kim, David Nagarathinam, Byoung-Kwon Ahn, Cheolsoo Park, Gun-Do Kim, Il-Sung Moon
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	bubbly flows two-phase flows high-speed imaging hydrofoil Technology T Engineering (General). Civil engineering (General) TA1-2040 Biology (General) QH301-705.5 Physics QC1-999 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/8a780d68cced445cbace27a90aaef97f
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id	oai:doaj.org-article:8a780d68cced445cbace27a90aaef97f
record_format	dspace
institution	DOAJ
collection	DOAJ
language	EN
topic	bubbly flows two-phase flows high-speed imaging hydrofoil Technology T Engineering (General). Civil engineering (General) TA1-2040 Biology (General) QH301-705.5 Physics QC1-999 Chemistry QD1-999
spellingShingle	bubbly flows two-phase flows high-speed imaging hydrofoil Technology T Engineering (General). Civil engineering (General) TA1-2040 Biology (General) QH301-705.5 Physics QC1-999 Chemistry QD1-999 Kiseong Kim David Nagarathinam Byoung-Kwon Ahn Cheolsoo Park Gun-Do Kim Il-Sung Moon Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream
description	Flow features, due to air injection through multiple vents on the surface of a hydrofoil inclined at an angle with respect to the free-stream in a cavitation tunnel, are presented here. The hydrofoil, with a chord length, <i>c</i>, is oriented at the angle of inclination, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> = 3.5°. The Froude number, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi></mrow></semantics></math></inline-formula>, based on the free-stream velocity, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>V</mi><mo>∞</mo></msub></semantics></math></inline-formula>, and air injection vent diameter, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>d</mi><mi>h</mi></msub></semantics></math></inline-formula>, is 30.30, 50.51 and 70.71. Air is injected through multiple vents on the hydrofoil at the non-dimensional air injection coefficient, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>q</mi></msub><mo>∼</mo><mn>16</mn><mo>−</mo><mn>8917</mn></mrow></semantics></math></inline-formula>. The air bubble packing per unit area is quantified using spatial density, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>S</mi><mi>D</mi></msub></semantics></math></inline-formula>, at various combinations of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi><mo>,</mo><msub><mi>C</mi><mi>q</mi></msub></mrow></semantics></math></inline-formula> based on a high-speed video from the side view. The time-averaged spatial density, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo><</mo><msub><mi>S</mi><mi>D</mi></msub><mo>></mo></mrow></semantics></math></inline-formula>, is observed to increase in a logarithmic manner with an increase in the air injection rate, <i>Q</i>, at various Froude numbers. There is an increase in the mean spatial density of the bubbles with the increase in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>q</mi></msub></semantics></math></inline-formula> at all <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi></mrow></semantics></math></inline-formula>. A power–law relation is shown to exist between the time-averaged spatial density, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo><</mo><msub><mi>S</mi><mi>D</mi></msub><mo>></mo></mrow></semantics></math></inline-formula>, and the non-dimensional flow variables, Reynolds number, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>R</mi><mi>e</mi></mrow><mrow><mi>a</mi><mi>i</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>q</mi></msub></semantics></math></inline-formula> based on a regression analysis. By tracking individual finite volume bubbles flowing with the free-stream, the bubble dimensions in pixels are quantified using quantities such as the deformation rate, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ϵ</mi></semantics></math></inline-formula>, and standardization, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ϵ</mi><mi>S</mi></msub></semantics></math></inline-formula>, from the side-view videos. It is observed that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ϵ</mi></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ϵ</mi><mi>S</mi></msub></semantics></math></inline-formula> change with time, even as they become advected with the free-stream. Through high-speed imaging from the top view, we characterize the bubbly flow features’ time-averaged thickness, <i>t</i>, at various combinations of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi><mo>,</mo><msub><mi>C</mi><mi>q</mi></msub></mrow></semantics></math></inline-formula> at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> = 3.5°. We obtain a power-law relation between the non-dimensional time-averaged jet thickness, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>t</mi><mo>/</mo><mi>c</mi></mrow></semantics></math></inline-formula>, and the non-dimensional flow parameters such as, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>R</mi><mi>e</mi></mrow><mrow><mi>a</mi><mi>i</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi><mo>,</mo><msub><mi>C</mi><mi>q</mi></msub></mrow></semantics></math></inline-formula> and the non-dimensional streamwise distance, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>x</mi><mo>/</mo><msub><mi>x</mi><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msub></mrow></semantics></math></inline-formula>, based on a regression analysis, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>x</mi><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msub></semantics></math></inline-formula> is a reference distance. The results are relevant to engineering applications where the air–water bubbly flow in a free-stream is important.
format	article
author	Kiseong Kim David Nagarathinam Byoung-Kwon Ahn Cheolsoo Park Gun-Do Kim Il-Sung Moon
author_facet	Kiseong Kim David Nagarathinam Byoung-Kwon Ahn Cheolsoo Park Gun-Do Kim Il-Sung Moon
author_sort	Kiseong Kim
title	Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream
title_short	Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream
title_full	Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream
title_fullStr	Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream
title_full_unstemmed	Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream
title_sort	air-water bubbly flow by multiple vents on a hydrofoil in a steady free-stream
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/8a780d68cced445cbace27a90aaef97f
work_keys_str_mv	AT kiseongkim airwaterbubblyflowbymultipleventsonahydrofoilinasteadyfreestream AT davidnagarathinam airwaterbubblyflowbymultipleventsonahydrofoilinasteadyfreestream AT byoungkwonahn airwaterbubblyflowbymultipleventsonahydrofoilinasteadyfreestream AT cheolsoopark airwaterbubblyflowbymultipleventsonahydrofoilinasteadyfreestream AT gundokim airwaterbubblyflowbymultipleventsonahydrofoilinasteadyfreestream AT ilsungmoon airwaterbubblyflowbymultipleventsonahydrofoilinasteadyfreestream
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spelling	oai:doaj.org-article:8a780d68cced445cbace27a90aaef97f2021-11-11T14:59:58ZAir-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream10.3390/app112198902076-3417https://doaj.org/article/8a780d68cced445cbace27a90aaef97f2021-10-01T00:00:00Zhttps://www.mdpi.com/2076-3417/11/21/9890https://doaj.org/toc/2076-3417Flow features, due to air injection through multiple vents on the surface of a hydrofoil inclined at an angle with respect to the free-stream in a cavitation tunnel, are presented here. The hydrofoil, with a chord length, <i>c</i>, is oriented at the angle of inclination, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> = 3.5°. The Froude number, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi></mrow></semantics></math></inline-formula>, based on the free-stream velocity, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>V</mi><mo>∞</mo></msub></semantics></math></inline-formula>, and air injection vent diameter, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>d</mi><mi>h</mi></msub></semantics></math></inline-formula>, is 30.30, 50.51 and 70.71. Air is injected through multiple vents on the hydrofoil at the non-dimensional air injection coefficient, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>C</mi><mi>q</mi></msub><mo>∼</mo><mn>16</mn><mo>−</mo><mn>8917</mn></mrow></semantics></math></inline-formula>. The air bubble packing per unit area is quantified using spatial density, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>S</mi><mi>D</mi></msub></semantics></math></inline-formula>, at various combinations of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi><mo>,</mo><msub><mi>C</mi><mi>q</mi></msub></mrow></semantics></math></inline-formula> based on a high-speed video from the side view. The time-averaged spatial density, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo><</mo><msub><mi>S</mi><mi>D</mi></msub><mo>></mo></mrow></semantics></math></inline-formula>, is observed to increase in a logarithmic manner with an increase in the air injection rate, <i>Q</i>, at various Froude numbers. There is an increase in the mean spatial density of the bubbles with the increase in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>q</mi></msub></semantics></math></inline-formula> at all <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi></mrow></semantics></math></inline-formula>. A power–law relation is shown to exist between the time-averaged spatial density, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo><</mo><msub><mi>S</mi><mi>D</mi></msub><mo>></mo></mrow></semantics></math></inline-formula>, and the non-dimensional flow variables, Reynolds number, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>R</mi><mi>e</mi></mrow><mrow><mi>a</mi><mi>i</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>q</mi></msub></semantics></math></inline-formula> based on a regression analysis. By tracking individual finite volume bubbles flowing with the free-stream, the bubble dimensions in pixels are quantified using quantities such as the deformation rate, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ϵ</mi></semantics></math></inline-formula>, and standardization, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ϵ</mi><mi>S</mi></msub></semantics></math></inline-formula>, from the side-view videos. It is observed that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ϵ</mi></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ϵ</mi><mi>S</mi></msub></semantics></math></inline-formula> change with time, even as they become advected with the free-stream. Through high-speed imaging from the top view, we characterize the bubbly flow features’ time-averaged thickness, <i>t</i>, at various combinations of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi><mo>,</mo><msub><mi>C</mi><mi>q</mi></msub></mrow></semantics></math></inline-formula> at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> = 3.5°. We obtain a power-law relation between the non-dimensional time-averaged jet thickness, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>t</mi><mo>/</mo><mi>c</mi></mrow></semantics></math></inline-formula>, and the non-dimensional flow parameters such as, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>R</mi><mi>e</mi></mrow><mrow><mi>a</mi><mi>i</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>n</mi><mo>,</mo><msub><mi>C</mi><mi>q</mi></msub></mrow></semantics></math></inline-formula> and the non-dimensional streamwise distance, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>x</mi><mo>/</mo><msub><mi>x</mi><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msub></mrow></semantics></math></inline-formula>, based on a regression analysis, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>x</mi><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msub></semantics></math></inline-formula> is a reference distance. The results are relevant to engineering applications where the air–water bubbly flow in a free-stream is important.Kiseong KimDavid NagarathinamByoung-Kwon AhnCheolsoo ParkGun-Do KimIl-Sung MoonMDPI AGarticlebubbly flowstwo-phase flowshigh-speed imaginghydrofoilTechnologyTEngineering (General). Civil engineering (General)TA1-2040Biology (General)QH301-705.5PhysicsQC1-999ChemistryQD1-999ENApplied Sciences, Vol 11, Iss 9890, p 9890 (2021)

Air-Water Bubbly Flow by Multiple Vents on a Hydrofoil in a Steady Free-Stream

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