The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
Young Kwan Sohn - One of the best experts on this subject based on the ideXlab platform.
-
transition from debris flow to hyperconcentrated flow in a submarine channel the cretaceous cerro toro formation southern chile
2002Co-Authors: Young Kwan Sohn, M Y Choe, H R JoAbstract:It is important to understand the exact process whereby very large amounts of sediment are transported. This paper reports peculiar conglomerate beds reflecting the transition of submarine debris flows into hyperconcentrated flows, something that has been well documented only in subaerial debris-flow events until now. Voluminous debris flows generated along a Cretaceous submarine channel, southern Chile, transformed immediately into multiphase flows. Their deposits overlie fluted or grooved surfaces and comprise a lower division of clastsupported and imbricated pebble‐cobble conglomerate with basal inverse grading and an upper division of clast- to matrixsupported, disorganized conglomerate with abundant intraformational clasts. The conglomerate beds suggest temporal succession of turbidity current, gravelly hyperconcentrated flow, and mud-rich debris flow phases. The multiphase flows resulted from progressive dilution of gravelly but cohesive debris flows that could Hydroplane, in contrast to the flow transitions in subaerial environments, which involve mostly non-cohesive debris flows. This finding has significant implications for the definition, classification, and hazard assessment of submarine mass-movement processes and characterization of submarine reservoir rocks.
-
depositional processes of submarine debris flows in the miocene fan deltas pohang basin se korea with special reference to flow transformation
2000Co-Authors: Young Kwan SohnAbstract:ABSTRACT Subaqueous debris flows undergo various flow transformations, involving dilution and stripping of surface materials, penetration of ambient water into the flow interior, and detachment and disintegration of hydroplaning flow fronts. The surface transformation is a self-limiting process because the products of the process, such as an overriding suspended-sediment cloud or an armor of gravel at the flow front, inhibit effective working of the process. The degree of flow transformation therefore depends largely on whether a debris flow Hydroplanes or not. For a subaqueous debris flow to Hydroplane, its densiometric Froude number should be larger than 0.4, and the time scale of pore-pressure decay should be larger than the duration of a debris flow. In addition, a debris flow should be devoid of an extremely permeable girth of openwork gravel around the flow head because high pressures cannot be sustained underneath the gravelly material. Detailed sedimentological measurements and estimation of flow properties for three debris-flow beds in the Miocene fan deltas in SE Korea suggests that only a pebbly debris flow with a muddy (impermeable) matrix Hydroplaned. On the other hand, bouldery debris flows are interpreted to have not Hydroplaned irrespective of the nature of matrix. Nonhydroplaning debris flows were subject mainly to surface transformation and were outrun by surface-transformed suspended-sediment flows and debris-fall blocks after the flows entered a base-of-slope setting. Deposits of nonhydroplaning debris flows therefore overlie deposits of turbidity currents and debris falls. In the case of a hydroplaning debris flow, large chunks of debris could be detached from the flow front repetitively to form a series of small-volume flows that proceeded in front of the host debris flow. The preceding flows were promptly diluted to produce voluminous suspended-sediment clouds and were outrun by the faster-moving host debris flow. A deposit from a hydroplaning debris flow is therefore associated with thick and extensive turbiditic deposits that may either underlie or overlie the host debris-flow deposit. The turbiditic deposits associated with a hydroplaning debris flow are distinguished from those of a nonhydroplaning debris flow in that the former contain abundant gravel clasts and chunks of poorly sorted and clast-rich debris that cannot be suspended by the surface transformation process but were more likely derived from the detached fronts of a hydroplaning debris flow. These differences in sediment volume and grain size of turbiditic deposits and the stacking pattern of related debrites and turbidites provide a clue to the behavior of subaqueous debris flows.
H R Jo - One of the best experts on this subject based on the ideXlab platform.
-
transition from debris flow to hyperconcentrated flow in a submarine channel the cretaceous cerro toro formation southern chile
2002Co-Authors: Young Kwan Sohn, M Y Choe, H R JoAbstract:It is important to understand the exact process whereby very large amounts of sediment are transported. This paper reports peculiar conglomerate beds reflecting the transition of submarine debris flows into hyperconcentrated flows, something that has been well documented only in subaerial debris-flow events until now. Voluminous debris flows generated along a Cretaceous submarine channel, southern Chile, transformed immediately into multiphase flows. Their deposits overlie fluted or grooved surfaces and comprise a lower division of clastsupported and imbricated pebble‐cobble conglomerate with basal inverse grading and an upper division of clast- to matrixsupported, disorganized conglomerate with abundant intraformational clasts. The conglomerate beds suggest temporal succession of turbidity current, gravelly hyperconcentrated flow, and mud-rich debris flow phases. The multiphase flows resulted from progressive dilution of gravelly but cohesive debris flows that could Hydroplane, in contrast to the flow transitions in subaerial environments, which involve mostly non-cohesive debris flows. This finding has significant implications for the definition, classification, and hazard assessment of submarine mass-movement processes and characterization of submarine reservoir rocks.
Antonio M. Pascoal - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of Normal Force and Moment Coefficients for an AUV at Nonlinear Angle
2015Co-Authors: Of Attack, E.a. De Barros, João Lucas Dozzi Dantas, Sideslip Range, Antonio M. PascoalAbstract:Abstract—This paper presents a comparative study of compu-tational fluid dynamics (CFD) and analytical and semiempirical (ASE) methods applied to the prediction of the normal force and moment coefficients of an autonomous underwater vehicle (AUV). Both methods are applied to the bare hull of the vehicle and to the body–Hydroplane combination. The results are validated through experiments in a towing tank. It is shown that the CFD approach allows for a good prediction of the coefficients over the range of angles of attack considered. In contrast with the traditional ASE formulations used in naval and aircraft fields, an improved methodology is introduced that takes advantage of the qualitative information obtained from CFD flow visualizations. Index Terms—Autonomous underwater vehicle (AUV), com-putational fluid dynamics (CFD), hydrodynamic derivatives, maneuvering. I
-
Investigation of Normal Force and Moment Coefficients for an AUV at Nonlinear Angle of Attack and Sideslip Range
2008Co-Authors: E.a. De Barros, João Lucas Dozzi Dantas, Antonio M. PascoalAbstract:This paper presents a comparative study of computational fluid dynamics (CFD) and analytical and semiempirical (ASE) methods applied to the prediction of the normal force and moment coefficients of an autonomous underwater vehicle (AUV). Both methods are applied to the bare hull of the vehicle and to the body-Hydroplane combination. The results are validated through experiments in a towing tank. It is shown that the CFD approach allows for a good prediction of the coefficients over the range of angles of attack considered. In contrast with the traditional ASE formulations used in naval and aircraft fields, an improved methodology is introduced that takes advantage of the qualitative information obtained from CFD flow visualizations.
E.a. De Barros - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of Normal Force and Moment Coefficients for an AUV at Nonlinear Angle
2015Co-Authors: Of Attack, E.a. De Barros, João Lucas Dozzi Dantas, Sideslip Range, Antonio M. PascoalAbstract:Abstract—This paper presents a comparative study of compu-tational fluid dynamics (CFD) and analytical and semiempirical (ASE) methods applied to the prediction of the normal force and moment coefficients of an autonomous underwater vehicle (AUV). Both methods are applied to the bare hull of the vehicle and to the body–Hydroplane combination. The results are validated through experiments in a towing tank. It is shown that the CFD approach allows for a good prediction of the coefficients over the range of angles of attack considered. In contrast with the traditional ASE formulations used in naval and aircraft fields, an improved methodology is introduced that takes advantage of the qualitative information obtained from CFD flow visualizations. Index Terms—Autonomous underwater vehicle (AUV), com-putational fluid dynamics (CFD), hydrodynamic derivatives, maneuvering. I
-
Investigation of Normal Force and Moment Coefficients for an AUV at Nonlinear Angle of Attack and Sideslip Range
2008Co-Authors: E.a. De Barros, João Lucas Dozzi Dantas, Antonio M. PascoalAbstract:This paper presents a comparative study of computational fluid dynamics (CFD) and analytical and semiempirical (ASE) methods applied to the prediction of the normal force and moment coefficients of an autonomous underwater vehicle (AUV). Both methods are applied to the bare hull of the vehicle and to the body-Hydroplane combination. The results are validated through experiments in a towing tank. It is shown that the CFD approach allows for a good prediction of the coefficients over the range of angles of attack considered. In contrast with the traditional ASE formulations used in naval and aircraft fields, an improved methodology is introduced that takes advantage of the qualitative information obtained from CFD flow visualizations.
-
Investigation of Normal Force and Moment Coefficients for an AUV at Nonlinear Angle of Attack and Sideslip Range
2008Co-Authors: E.a. De Barros, Dantas, Joao L. D., Pascoal, Antonio M.Abstract:This paper presents a comparative study of computational fluid dynamics (CFD) and analytical and semiempirical (ASE) methods applied to the prediction of the normal force and moment coefficients of an autonomous underwater vehicle (AUV). Both methods are applied to the. bare hull of the vehicle and to the body-Hydroplane combination. The results are validated through experiments in a towing tank. It is shown that the CFD approach allows for a good prediction of the coefficients over the range of angles of attack considered. In contrast with the traditional ASE formulations used in naval and aircraft fields, an improved methodology is introduced that takes advantage of the qualitative information obtained from CFD flow visualizations.FAPESP foundation, Sao Paulo, BrazilFCT-ISR/IST Pluriannual ProgramMaya ProjectIndo-Portuguese Cooperation Progra
Gonzalez Reverte, Francisco Javier - One of the best experts on this subject based on the ideXlab platform.
-
Diseño y estudio de un sistema de aerofreno de un "Hydroplane"
2007Co-Authors: Gonzalez Reverte, Francisco JavierAbstract:El presente Trabajo de Fin de Carrera tiene como objetivo el estudio aerodinámico de un Hydroplane, una barca motorizada exclusiva para carreras. Los Hydroplanes son las barcas más rápidas que existen y se llaman Hydroplanes porque la embarcación planea sobre el agua de lo rápido que va. Además se estudia por qué motivo a veces estas embarcaciones sufren unos accidentes en que vuelcan. Estos accidentes se producen cuando el Hydroplane va a su máxima velocidad y se encuentra con alguna perturbación en su camino, que lo hace levantar más de lo normal en condiciones de carrera, y acaba volcando. Este fenómeno se puede comparar con lo que pasa con un perfil de ala de un avión en que como más ángulo de ataque tiene, más fuerza de sustentación genera. La fuerza de sustentación es la fuerza aerodinámica que hace que un avión vuele. Una vez analizado el Hydroplane, se diseñan unos aerofrenos, como los que se usan en los aviones, para intentar reducir la fuerza de sustentación que hace que el Hydroplane vuelque. Los aerofrenos de los aviones son unas superficies que rompen la forma aerodinámica del ala y de este modo reducen la fuerza de sustentación generada. La aplicación de los aerofrenos en estas embarcaciones es la idea original de este Trabajo de Fin de Carrera, porque hasta ahora no existe ningún sistema parecido. Para realizar el estudio aerodinámico del Hydroplane se utiliza un programa de dinámica de fluidos computacional, que simula las condiciones obtenidas en un túnel de viento. Este programa simula el paso del flujo de aire alrededor del modelo de Hydroplane y permite conocer las fuerzas que el aire ejerce sobre la embarcación. Las simulaciones se tienen que hacer con diferentes configuraciones del Hydroplane: la configuración básica, con alerón y con los aerofrenos, para ver como afectan las diferentes modificaciones aerodinámicas. También se hace el estudio con varios ángulos de ataque, para ver como crecen las fuerzas aerodinámicas. Este trabajo comprueba como los aerofrenos reducen considerablemente la fuerza de sustentación del Hydroplane y como pueden ser de gran utilidad para evitar futuros accidentes. Al final del trabajo se proponen posibles soluciones para saber en qué momento se deben aplicar los aerofrenos para que éstos tengan efecto
