Author(s): J. Imran; A. Kassem; S. M. Khan

Linked Author(s): imran, Ahmed Kassem

Keywords: Numerical modeling; density currents; turbidity currents; submarine channels; flow spilling; secondary circulation

Abstract: The lateral development of density-driven flow in a subaqueous channel is studied using a three-dimensional numerical model. The model is applied to four different cases of confined and unconfined flow in straight channels. The density current is generated by injecting a heavier fluid as a plug flow at the upstream boundary of the channel. The inflow transforms into a density current within a short distance. The current increases in thickness by entraining the ambient lighter fluid as it travels in the downstream direction. In the unconfined cases, the flow begins to spill in the lateral direction as soon as its thickness exceeds the bank height. The spilling results in a distinct lateral flow in the overbank area and limits the growth of the current in the vertical direction. The vertical structure of the overbank flow in the lateral direction is found to be similar to the primary flow structure of a density current. The magnitude of the lateral flow is found to depend strongly on the lateral slope of the floodplain. In the confined case, high sidewalls keep the flow inside the channel and the current continues to grow in the vertical direction. Two weak circulation cells are observed near the sidewalls in all cases. These circulation cells may act to redistribute fluid density across a channel cross-section. Although the model is applied here to a conservative density current, the analysis is valid in general for turbidity current driven by fine sediment.

DOI: https://doi.org/10.1080/00221686.2004.9628312

Year: 2004