A turbulence-resolving numerical investigation of wave-supported gravity flows
MetadataShow full item record
Keywordwave‐supported gravity flows; turbulence‐resolving numerical simulation; wave direction; intermittently turbulent flow
Wave‐supported gravity flows (WSGFs) have been identified as a key process driving the offshore delivery of fine sediment across continental shelves. However, our understanding on the various factors controlling the maximum sediment load and the resulting gravity current speed remains incomplete. We adopt a new turbulence‐resolving numerical model for fine sediment transport to investigate the formation, evolution, and termination of WSGFs. We consider the simplest scenario in which fine sediments are supported by the wave‐induced fluid turbulence at a low critical shear stress of erosion over a flat sloping bed. Under the energetic wave condition reported on the Northern California Coast with a shelf slope of 0.005, simulation results show that WSGFs are transitionally turbulent and that the sediment concentration cannot exceed 30 kg/m urn:x-wiley:jgrc:media:jgrc23843:jgrc23843-math-0001 (g/L) due to the attenuation of turbulence by the sediment‐induced stable density stratification. Wave direction is found to be important in the resulting gravity current intensity. When waves are in cross‐shelf direction, the downslope current has a maximum velocity of 1.2 cm/s, which increases to 2.1 cm/s when waves propagate in the along‐shelf direction. Further analysis on the wave‐averaged momentum balance confirms that when waves are parallel to the slope (cross‐shelf) direction, the more intense wave‐current interaction results in larger wave‐averaged Reynolds shear stress and thus in a smaller current speed. Findings from this study suggest that the more intense cross‐shelf gravity current observed in the field may be caused by additional processes, which may enhance the sediment‐carrying capacity of flow, such as the ambient current or bedforms.
Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 125(2), (2020): e2019JC015220, doi:10.1029/2019JC015220.
Suggested CitationYue, L., Cheng, Z., & Hsu, T. (2020). A turbulence-resolving numerical investigation of wave-supported gravity flows. Journal of Geophysical Research-Oceans, 125(2), e2019JC015220.
Showing items related by title, author, creator and subject.
Sanford, Thomas B.; Price, James F.; Girton, James B.; Webb, Douglas C. (American Geophysical Union, 2007-07-07)An autonomous, profiling float called EM-APEX was developed to provide a quantitative and comprehensive description of the ocean side of hurricane-ocean interaction. EM-APEX measures temperature, salinity and pressure to ...
Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf Traykovski, Peter A.; Wiberg, Patricia L.; Geyer, W. Rockwell (2006-11-14)A mooring and tripod array was deployed from the fall of 2002 through the spring of 2003 on the Po prodelta to measure sediment transport processes associated with sediment delivered from the Po River. Observations on the ...
Hsu, Tian-Jian; Ozdemir, Celalettin E.; Traykovski, Peter A. (American Geophysical Union, 2009-05-14)Wave-supported gravity-driven mudflow has been identified as a major offshore fine sediment transport mechanism of terrestrial sediment into the coastal ocean. This transport process essentially occurs within the wave ...