CMS/DredgeModule/Phase2: Difference between revisions
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= Background = | |||
The dredging and placement of multiple sediment grain-sizes are an extension of the single-grain | |||
size transport approach. In the updated Dredge Module, the sediment can be represented by discrete grain size | |||
classes, and each size class is eroded, transported, and deposited independently. The grain size | |||
classes interact solely in the bed layers. The bed is represented by sediment layers of a specific | |||
thickness below the bed surface. The top or surficial upper bed layer is referred to as the mixing | |||
layer (often referred to as the active layer), which exchanges the surficial sediments with | |||
deposition from the water column. The mixing layer thickness may be set to a constant value (e.g., | |||
0.05 meter [m]) or calculated based on the median grain size and bed form size at each cell. The | |||
critical shear stress for erosion for each grain size class in the mixing layer is determined using the | |||
hiding and exposure approach of Wu. | |||
Below the mixing layer, additional bed layers are defined and are used to track the fraction of each | |||
grain size class in the bed, referred to as the bed composition. All of the bed layers exchange | |||
sediment with each other by splitting and merging adjacent layers as their thickness evolves during | |||
a simulation due to erosion and deposition. Guidance on the implementation in SMS is available at [[CMS-Flow_Multiple-sized_Sediment_Transport | CMS-Flow_Multiple-sized_Sediment_Transport]]. | |||
= Dredge Area Setup = | |||
The first dredge area, "CapitolDredge" consists of a dredge source area aligned to represent a navigation channel (north-south alignment). The dredge depth was set to 6 meters, which created a total dredge volume of approximately 153,000 m<sup>3</sup>. The dredge rate was set to 5000 m3/day, which yielded a total time of 30 days to complete dredging. Two placement areas were defined; both near the southern edge of the grid domain, one to each side of the channel. | |||
Revision as of 16:06, 30 January 2024
Under construction.
Background
The dredging and placement of multiple sediment grain-sizes are an extension of the single-grain size transport approach. In the updated Dredge Module, the sediment can be represented by discrete grain size classes, and each size class is eroded, transported, and deposited independently. The grain size classes interact solely in the bed layers. The bed is represented by sediment layers of a specific thickness below the bed surface. The top or surficial upper bed layer is referred to as the mixing layer (often referred to as the active layer), which exchanges the surficial sediments with deposition from the water column. The mixing layer thickness may be set to a constant value (e.g., 0.05 meter [m]) or calculated based on the median grain size and bed form size at each cell. The critical shear stress for erosion for each grain size class in the mixing layer is determined using the hiding and exposure approach of Wu.
Below the mixing layer, additional bed layers are defined and are used to track the fraction of each grain size class in the bed, referred to as the bed composition. All of the bed layers exchange sediment with each other by splitting and merging adjacent layers as their thickness evolves during a simulation due to erosion and deposition. Guidance on the implementation in SMS is available at CMS-Flow_Multiple-sized_Sediment_Transport.
Dredge Area Setup
The first dredge area, "CapitolDredge" consists of a dredge source area aligned to represent a navigation channel (north-south alignment). The dredge depth was set to 6 meters, which created a total dredge volume of approximately 153,000 m3. The dredge rate was set to 5000 m3/day, which yielded a total time of 30 days to complete dredging. Two placement areas were defined; both near the southern edge of the grid domain, one to each side of the channel.