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Vortical structures and instability analysis for athena wetted transom flow with full-scale validation / Shanti Bhushan in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 18 p. Titre : Vortical structures and instability analysis for athena wetted transom flow with full-scale validation Type de document : texte imprimé Auteurs : Shanti Bhushan, Auteur ; Tao Xing, Auteur ; Frederick Stern, Auteur Année de publication : 2012 Article en page(s) : 18 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Transform  flow  Full-scale  validation  Vortex  instability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Vortical structures and associated instabilities of appended Athena wetted transom flow in full-scale conditions are studied using DES to explain the source of dominant transom flow frequency, including verification and validation using full-scale experimental data. The results are also compared with model-scale bare and appended hull predictions and experiments. The grid used for the validation is sufficiently fine as it resolves 70% and 91% of the experimental inertial subrange and turbulent kinetic energy values, respectively. The model-scale bare and appended hull resistance predictions compare within 2.5%D and 5.4%D of the experimental data D, respectively. The full-scale appended hull resistance predictions compare within 4.2%D of the extrapolated data using the ITTC line. The averaged comparison error of the full-scale transom wave elevation mean, RMS and dominant frequency predictions and the experimental data is 8.1%D, and the predictions are validated at an averaged 11.2%D interval. The transom wave elevation unsteadiness is attributed to the Karman-like transom vortex shedding as both show the same dominant frequency. The Karman-like instability shows St = 0.148 for the bare hull and St = 0.103 ± 4.4% for model- and full-scale appended hull. The appended hull simulations also predict: horseshoe vortices at the juncture of rudder-hull with St = 0.146 ± 3.9% and strut-hull with St = 0.053 ± 2%; shear layer instability at the strut-hull intersection with St = 0.0067 ± 3%; and unsteady sinkage and trim induced by transom vortex shedding with St = 2.19. The instabilities do not show significant variation on scale, propeller or motions. The bare hull simulation also predicts flapping-like instability in the wake with St = 0.144. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Vortical structures and instability analysis for athena wetted transom flow with full-scale validation [texte imprimé] / Shanti Bhushan, Auteur ; Tao Xing, Auteur ; Frederick Stern, Auteur . - 2012 . - 18 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 18 p. Mots-clés : Transform  flow  Full-scale  validation  Vortex  instability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Vortical structures and associated instabilities of appended Athena wetted transom flow in full-scale conditions are studied using DES to explain the source of dominant transom flow frequency, including verification and validation using full-scale experimental data. The results are also compared with model-scale bare and appended hull predictions and experiments. The grid used for the validation is sufficiently fine as it resolves 70% and 91% of the experimental inertial subrange and turbulent kinetic energy values, respectively. The model-scale bare and appended hull resistance predictions compare within 2.5%D and 5.4%D of the experimental data D, respectively. The full-scale appended hull resistance predictions compare within 4.2%D of the extrapolated data using the ITTC line. The averaged comparison error of the full-scale transom wave elevation mean, RMS and dominant frequency predictions and the experimental data is 8.1%D, and the predictions are validated at an averaged 11.2%D interval. The transom wave elevation unsteadiness is attributed to the Karman-like transom vortex shedding as both show the same dominant frequency. The Karman-like instability shows St = 0.148 for the bare hull and St = 0.103 ± 4.4% for model- and full-scale appended hull. The appended hull simulations also predict: horseshoe vortices at the juncture of rudder-hull with St = 0.146 ± 3.9% and strut-hull with St = 0.053 ± 2%; shear layer instability at the strut-hull intersection with St = 0.0067 ± 3%; and unsteady sinkage and trim induced by transom vortex shedding with St = 2.19. The instabilities do not show significant variation on scale, propeller or motions. The bare hull simulation also predicts flapping-like instability in the wake with St = 0.144. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]