Experimental bedforms by saline density currents
Autor(a) principal: | |
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Data de Publicação: | 2019 |
Outros Autores: | , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Brazilian Journal of Geology |
Texto Completo: | http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892019000200303 |
Resumo: | Abstract Bedforms are sedimentary features that can be generated on the seafloor by the interaction between density currents and mobile beds. Developing knowledge about the hydraulic and sedimentary processes involved during these events is in the interest of research groups and oil companies. Because of the magnitude of the density currents in its natural environment and the challenge in collecting data, studies in laboratory are of great value. We present results of 29 experiments focusing in the bedform development generated by saline currents, testing two different sediment types and three grain sizes: melamine (245 µm-plastic) and sands (206 and 485 µm). We analyzed the current velocity and fractional density profiles as well as pictures taken during and after each run. Results have showed classical velocity and concentration profiles, for 8 subcritical and 21 supercritical currents, with densimetric Froude numbers (Frd) between 0.5 and 2.2. Some correlations were identified, such as the decrease of the velocity peak height and increase in the mean velocity (with consequent reduction of the current thickness), due to an increase of the concentration and/or flume slope. The occurrence of bedforms was more likely for high discharge and concentration rates of current density, which directly influence the Frd. Bedforms were classified according to the shear stresses values applied by the current to the bed, resulting in the generation of lower plane bed, ripples and dunes. Dunes and ripples were observed in supercritical flow conditions, which is a hydraulic scenario of bedforms generation not predicted by fluvial models. Thus, this study demonstrated the existence of differences in generation and, consequently, the classification approach for density current bedforms, compared to those generated by river flows. To this fact is attributed the hydrodynamic (velocity and concentration profiles) and sediment transport differences between fluvial flows and density currents. Further studies may be carried out in order to constructing new concepts of bedforms generation by density currents. |
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Brazilian Journal of Geology |
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Experimental bedforms by saline density currentsPhysical modellingdensity currentsmobile bedbedformsAbstract Bedforms are sedimentary features that can be generated on the seafloor by the interaction between density currents and mobile beds. Developing knowledge about the hydraulic and sedimentary processes involved during these events is in the interest of research groups and oil companies. Because of the magnitude of the density currents in its natural environment and the challenge in collecting data, studies in laboratory are of great value. We present results of 29 experiments focusing in the bedform development generated by saline currents, testing two different sediment types and three grain sizes: melamine (245 µm-plastic) and sands (206 and 485 µm). We analyzed the current velocity and fractional density profiles as well as pictures taken during and after each run. Results have showed classical velocity and concentration profiles, for 8 subcritical and 21 supercritical currents, with densimetric Froude numbers (Frd) between 0.5 and 2.2. Some correlations were identified, such as the decrease of the velocity peak height and increase in the mean velocity (with consequent reduction of the current thickness), due to an increase of the concentration and/or flume slope. The occurrence of bedforms was more likely for high discharge and concentration rates of current density, which directly influence the Frd. Bedforms were classified according to the shear stresses values applied by the current to the bed, resulting in the generation of lower plane bed, ripples and dunes. Dunes and ripples were observed in supercritical flow conditions, which is a hydraulic scenario of bedforms generation not predicted by fluvial models. Thus, this study demonstrated the existence of differences in generation and, consequently, the classification approach for density current bedforms, compared to those generated by river flows. To this fact is attributed the hydrodynamic (velocity and concentration profiles) and sediment transport differences between fluvial flows and density currents. Further studies may be carried out in order to constructing new concepts of bedforms generation by density currents.Sociedade Brasileira de Geologia2019-01-01info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersiontext/htmlhttp://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892019000200303Brazilian Journal of Geology v.49 n.2 2019reponame:Brazilian Journal of Geologyinstname:Sociedade Brasileira de Geologia (SBGEO)instacron:SBGEO10.1590/2317-4889201920180118info:eu-repo/semantics/openAccessKoller,DéboraManica,RafaelBorges,Ana de OliveiraFedele,Juaneng2019-05-17T00:00:00Zoai:scielo:S2317-48892019000200303Revistahttp://bjg.siteoficial.ws/index.htmhttps://old.scielo.br/oai/scielo-oai.phpsbgsede@sbgeo.org.br||claudio.riccomini@gmail.com2317-46922317-4692opendoar:2019-05-17T00:00Brazilian Journal of Geology - Sociedade Brasileira de Geologia (SBGEO)false |
dc.title.none.fl_str_mv |
Experimental bedforms by saline density currents |
title |
Experimental bedforms by saline density currents |
spellingShingle |
Experimental bedforms by saline density currents Koller,Débora Physical modelling density currents mobile bed bedforms |
title_short |
Experimental bedforms by saline density currents |
title_full |
Experimental bedforms by saline density currents |
title_fullStr |
Experimental bedforms by saline density currents |
title_full_unstemmed |
Experimental bedforms by saline density currents |
title_sort |
Experimental bedforms by saline density currents |
author |
Koller,Débora |
author_facet |
Koller,Débora Manica,Rafael Borges,Ana de Oliveira Fedele,Juan |
author_role |
author |
author2 |
Manica,Rafael Borges,Ana de Oliveira Fedele,Juan |
author2_role |
author author author |
dc.contributor.author.fl_str_mv |
Koller,Débora Manica,Rafael Borges,Ana de Oliveira Fedele,Juan |
dc.subject.por.fl_str_mv |
Physical modelling density currents mobile bed bedforms |
topic |
Physical modelling density currents mobile bed bedforms |
description |
Abstract Bedforms are sedimentary features that can be generated on the seafloor by the interaction between density currents and mobile beds. Developing knowledge about the hydraulic and sedimentary processes involved during these events is in the interest of research groups and oil companies. Because of the magnitude of the density currents in its natural environment and the challenge in collecting data, studies in laboratory are of great value. We present results of 29 experiments focusing in the bedform development generated by saline currents, testing two different sediment types and three grain sizes: melamine (245 µm-plastic) and sands (206 and 485 µm). We analyzed the current velocity and fractional density profiles as well as pictures taken during and after each run. Results have showed classical velocity and concentration profiles, for 8 subcritical and 21 supercritical currents, with densimetric Froude numbers (Frd) between 0.5 and 2.2. Some correlations were identified, such as the decrease of the velocity peak height and increase in the mean velocity (with consequent reduction of the current thickness), due to an increase of the concentration and/or flume slope. The occurrence of bedforms was more likely for high discharge and concentration rates of current density, which directly influence the Frd. Bedforms were classified according to the shear stresses values applied by the current to the bed, resulting in the generation of lower plane bed, ripples and dunes. Dunes and ripples were observed in supercritical flow conditions, which is a hydraulic scenario of bedforms generation not predicted by fluvial models. Thus, this study demonstrated the existence of differences in generation and, consequently, the classification approach for density current bedforms, compared to those generated by river flows. To this fact is attributed the hydrodynamic (velocity and concentration profiles) and sediment transport differences between fluvial flows and density currents. Further studies may be carried out in order to constructing new concepts of bedforms generation by density currents. |
publishDate |
2019 |
dc.date.none.fl_str_mv |
2019-01-01 |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892019000200303 |
url |
http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892019000200303 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
10.1590/2317-4889201920180118 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
text/html |
dc.publisher.none.fl_str_mv |
Sociedade Brasileira de Geologia |
publisher.none.fl_str_mv |
Sociedade Brasileira de Geologia |
dc.source.none.fl_str_mv |
Brazilian Journal of Geology v.49 n.2 2019 reponame:Brazilian Journal of Geology instname:Sociedade Brasileira de Geologia (SBGEO) instacron:SBGEO |
instname_str |
Sociedade Brasileira de Geologia (SBGEO) |
instacron_str |
SBGEO |
institution |
SBGEO |
reponame_str |
Brazilian Journal of Geology |
collection |
Brazilian Journal of Geology |
repository.name.fl_str_mv |
Brazilian Journal of Geology - Sociedade Brasileira de Geologia (SBGEO) |
repository.mail.fl_str_mv |
sbgsede@sbgeo.org.br||claudio.riccomini@gmail.com |
_version_ |
1752122399013208064 |