Characteristics of shear layer and primary vortex induced by solitary waves propagating over rectangular structures with different aspect ratios / Tsung-Chun Ho in Journal of engineering mechanics, Vol. 138 N° 9 (Septembre 2012)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 138 N° 9 (Septembre 2012) . - pp.1084–1100. Titre : Characteristics of shear layer and primary vortex induced by solitary waves propagating over rectangular structures with different aspect ratios Type de document : texte imprimé Auteurs : Tsung-Chun Ho, Auteur ; Chang Lin, Auteur ; Kao-Shu Hwang, Auteur Année de publication : 2012 Article en page(s) : pp.1084–1100. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Solitary wave Vortex shedding Shear layer Submerged structure Particle image velocimetry Flow visualization Aspect ratio Résumé : The flow characteristics induced by a solitary wave propagating over a submerged and bottom-mounted structure were studied experimentally using time-resolved particle image velocimetry (PIV) and particle trajectory photography for flow visualization. The setup for time-resolved PIV consisted of a high-speed camera and an argon-ion laser. Image processing techniques were utilized to improve both the temporal and spatial resolutions of the PIV system. The main parameters were wave steepness (H/h=0.16–0.38) and aspect ratios of the rectangular structures (L/D=0.14–11.1). The vortex shedding process near the trailing edge was divided into the following phases: the formation of the separated shear layer, generation of the vortices, vortex motion, and breakdown of the vortices. The motions of the primary vortex may differ depending on experimental parameters. By analyzing these motions, flow patterns were categorized into Types A, B, and C, and the conditions for these types were investigated. In the formation of the shear layer, the similarity profile was determined by selecting the proper length and velocity scales. The relationship between characteristic scales and nondimensional experimental parameters were also investigated. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000420 [article] Characteristics of shear layer and primary vortex induced by solitary waves propagating over rectangular structures with different aspect ratios [texte imprimé] / Tsung-Chun Ho, Auteur ; Chang Lin, Auteur ; Kao-Shu Hwang, Auteur . - 2012 . - pp.1084–1100. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 9 (Septembre 2012) . - pp.1084–1100. Mots-clés : Solitary wave Vortex shedding Shear layer Submerged structure Particle image velocimetry Flow visualization Aspect ratio Résumé : The flow characteristics induced by a solitary wave propagating over a submerged and bottom-mounted structure were studied experimentally using time-resolved particle image velocimetry (PIV) and particle trajectory photography for flow visualization. The setup for time-resolved PIV consisted of a high-speed camera and an argon-ion laser. Image processing techniques were utilized to improve both the temporal and spatial resolutions of the PIV system. The main parameters were wave steepness (H/h=0.16–0.38) and aspect ratios of the rectangular structures (L/D=0.14–11.1). The vortex shedding process near the trailing edge was divided into the following phases: the formation of the separated shear layer, generation of the vortices, vortex motion, and breakdown of the vortices. The motions of the primary vortex may differ depending on experimental parameters. By analyzing these motions, flow patterns were categorized into Types A, B, and C, and the conditions for these types were investigated. In the formation of the shear layer, the similarity profile was determined by selecting the proper length and velocity scales. The relationship between characteristic scales and nondimensional experimental parameters were also investigated. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000420

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Characteristics of steady horseshoe vortex system near junction of square cylinder and base plate / Chang Lin in Journal of engineering mechanics, Vol. 134 N°2 (Fevrier 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 N°2 (Fevrier 2008) . - pp. 184–197. Titre : Characteristics of steady horseshoe vortex system near junction of square cylinder and base plate Type de document : texte imprimé Auteurs : Chang Lin, Auteur ; Tsung-Chun Ho, Auteur ; Subhasish Dey, Auteur Année de publication : 2008 Article en page(s) : pp. 184–197. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Vortices Boundary layers Cylinders Plates Reynolds number Résumé : This paper presents an experimental investigation on the characteristics of a horseshoe vortex system near the juncture of a square cylinder and a horizontal base plate, using particle image velocimetry and flow visualization technique. Experiments were conducted for Reynolds numbers (based on the free stream velocity and the width of square cylinder) ranging from 2.0×102 to 6.0×103 . The flow patterns are first classified into four major regimes: Steady horseshoe vortex system, periodic oscillation vortex system with small displacement, periodic breakaway vortex system, and irregular vortex system. The classifications can be demonstrated as a figure of Reynolds number versus the ratio of the height of square cylinder to undisturbed boundary layer thickness. The study then mainly focused on the characteristics of steady horseshoe vortex system (corresponding to Reynolds numbers ranging from 2.0×102 to 2.5×103 ). The nondimensional characteristics, including the horizontal and vertical distances from the primary vortex core to frontal face of the vertical square cylinder and bottom boundary of the base plate, respectively, the height of stagnation point at frontal face of the square cylinder, and the down-flow discharge as well as circulation of the primary vortex, all increase with increase of the ratio of the height of square cylinder to undisturbed boundary layer thickness. However, they all decrease with the increase of the aspect ratio (i.e., the height-to-width ratio) of the square cylinder. The study provides essential properties of a steady horseshoe vortex system and gives an insight for related engineering applications. It can be served as a basis for more complicated horseshoe vortex systems occurring at high Reynolds numbers. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A2%2818 [...] [article] Characteristics of steady horseshoe vortex system near junction of square cylinder and base plate [texte imprimé] / Chang Lin, Auteur ; Tsung-Chun Ho, Auteur ; Subhasish Dey, Auteur . - 2008 . - pp. 184–197. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°2 (Fevrier 2008) . - pp. 184–197. Mots-clés : Vortices Boundary layers Cylinders Plates Reynolds number Résumé : This paper presents an experimental investigation on the characteristics of a horseshoe vortex system near the juncture of a square cylinder and a horizontal base plate, using particle image velocimetry and flow visualization technique. Experiments were conducted for Reynolds numbers (based on the free stream velocity and the width of square cylinder) ranging from 2.0×102 to 6.0×103 . The flow patterns are first classified into four major regimes: Steady horseshoe vortex system, periodic oscillation vortex system with small displacement, periodic breakaway vortex system, and irregular vortex system. The classifications can be demonstrated as a figure of Reynolds number versus the ratio of the height of square cylinder to undisturbed boundary layer thickness. The study then mainly focused on the characteristics of steady horseshoe vortex system (corresponding to Reynolds numbers ranging from 2.0×102 to 2.5×103 ). The nondimensional characteristics, including the horizontal and vertical distances from the primary vortex core to frontal face of the vertical square cylinder and bottom boundary of the base plate, respectively, the height of stagnation point at frontal face of the square cylinder, and the down-flow discharge as well as circulation of the primary vortex, all increase with increase of the ratio of the height of square cylinder to undisturbed boundary layer thickness. However, they all decrease with the increase of the aspect ratio (i.e., the height-to-width ratio) of the square cylinder. The study provides essential properties of a steady horseshoe vortex system and gives an insight for related engineering applications. It can be served as a basis for more complicated horseshoe vortex systems occurring at high Reynolds numbers. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A2%2818 [...]

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Laboratory Observation of Solitary Wave Propagating Over Submerged Rectangular Dike / Chang Lin in Journal of engineering mechanics, Vol. 132 N°5 (Mai 2006)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 132 N°5 (Mai 2006) . - 545-554 p. Titre : Laboratory Observation of Solitary Wave Propagating Over Submerged Rectangular Dike Titre original : Observation de Laboratoire de Vague Solitaire Propageant la Digue Rectangulaire Submergée par Excédent Type de document : texte imprimé Auteurs : Chang Lin, Auteur ; Chang, Sung-Chieh, Auteur ; Tsung-Chun Ho ; Chang, Kuang-An ; Teng, Michelle H., Éditeur scientifique Année de publication : 2006 Article en page(s) : 545-554 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Laboratory Fluid-structure interaction Solitary waves Flow visualization tests Wave propagation Dikes de Fluide-structure Vagues solitaires Visualisation d'écoulement essais visualisation Propagation vague Digues Index. décimale : 621.34 Résumé : A solitary wave interacting with a bottom mounted rectangular dike was studied experimentally using the quantitative particle image velocimetry (PIV) technique and two qualitative flow visualization techniques, including the laser induced fluorescence technique and the particle tracing technique. Vortices were generated due to flow separation at the comers of the dike, and shed downstream and upward by the induced current. The vortex shedding processes were identified using the two qualitative visualization techniques while detailed velocity field was measured quantitatively using PIV. Detailed vortical structures in the vicinity of the dike were investigated and compared with observations in other studies. A greater than expected number of vortices were generated at both sides of the dike and observed through detailed flow visualization. A similarity profile similar to a turbulent jet was found for the flow on the lee side of the dike. ne vague solitaire agissant l'un sur l'autre avec une digue rectangulaire montée par fond a été étudiée expérimentalement en utilisant la technique velocimetry d'image quantitative de particules (PIV) et deux techniques qualitatives de visualisation d'écoulement, y compris la technique de fluorescence induite par laser et la technique traçante de particules. Les vortexes étaient dus produit à la séparation d'écoulement aux arrivants de la digue, et ont jeté en aval et vers le haut par le courant induit. Les processus de perte de vortex ont été identifiés en utilisant les deux techniques qualitatives de visualisation tandis que le champ détaillé de vitesse était mesuré quantitativement en utilisant PIV. Des structures vortical détaillées à proximité de la digue ont été étudiées et comparées aux observations dans d'autres études. Un nombre prévu plus grand que de vortexes ont été produits sur les deux côtés de la digue et observés par la visualisation détaillée d'écoulement. Un profil de similitude semblable à un turbulent voyagent en jet a été trouvé pour l'écoulement du côté de lie de la digue. En ligne : kchang@tamu.edu [article] Laboratory Observation of Solitary Wave Propagating Over Submerged Rectangular Dike = Observation de Laboratoire de Vague Solitaire Propageant la Digue Rectangulaire Submergée par Excédent [texte imprimé] / Chang Lin, Auteur ; Chang, Sung-Chieh, Auteur ; Tsung-Chun Ho ; Chang, Kuang-An ; Teng, Michelle H., Éditeur scientifique . - 2006 . - 545-554 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 132 N°5 (Mai 2006) . - 545-554 p. Mots-clés : Laboratory Fluid-structure interaction Solitary waves Flow visualization tests Wave propagation Dikes de Fluide-structure Vagues solitaires Visualisation d'écoulement essais visualisation Propagation vague Digues Index. décimale : 621.34 Résumé : A solitary wave interacting with a bottom mounted rectangular dike was studied experimentally using the quantitative particle image velocimetry (PIV) technique and two qualitative flow visualization techniques, including the laser induced fluorescence technique and the particle tracing technique. Vortices were generated due to flow separation at the comers of the dike, and shed downstream and upward by the induced current. The vortex shedding processes were identified using the two qualitative visualization techniques while detailed velocity field was measured quantitatively using PIV. Detailed vortical structures in the vicinity of the dike were investigated and compared with observations in other studies. A greater than expected number of vortices were generated at both sides of the dike and observed through detailed flow visualization. A similarity profile similar to a turbulent jet was found for the flow on the lee side of the dike. ne vague solitaire agissant l'un sur l'autre avec une digue rectangulaire montée par fond a été étudiée expérimentalement en utilisant la technique velocimetry d'image quantitative de particules (PIV) et deux techniques qualitatives de visualisation d'écoulement, y compris la technique de fluorescence induite par laser et la technique traçante de particules. Les vortexes étaient dus produit à la séparation d'écoulement aux arrivants de la digue, et ont jeté en aval et vers le haut par le courant induit. Les processus de perte de vortex ont été identifiés en utilisant les deux techniques qualitatives de visualisation tandis que le champ détaillé de vitesse était mesuré quantitativement en utilisant PIV. Des structures vortical détaillées à proximité de la digue ont été étudiées et comparées aux observations dans d'autres études. Un nombre prévu plus grand que de vortexes ont été produits sur les deux côtés de la digue et observés par la visualisation détaillée d'écoulement. Un profil de similitude semblable à un turbulent voyagent en jet a été trouvé pour l'écoulement du côté de lie de la digue. En ligne : kchang@tamu.edu

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