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Turbidity Current Dynamics: 1. Model Formulation and Identification of Flow Equilibrium Conditions Resulting From Flow Stripping and Overspill
Author(s) -
Traer M. M.,
Fildani A.,
Fringer O.,
McHargue T.,
Hilley G. E.
Publication year - 2018
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2017jf004200
Subject(s) - settling , turbidity current , mechanics , turbidity , turbulence , flow (mathematics) , suspension (topology) , sedimentation , sediment , geology , environmental science , thermodynamics , physics , geomorphology , mathematics , sedimentary depositional environment , oceanography , structural basin , homotopy , pure mathematics
This study expands the widely used one‐dimensional, four‐equation model for turbidity currents to account for mass, momentum, and energy sinks associated with flow stripping and overspill processes acting upon the turbidity current suspension cloud. The suspension cloud is defined as any portion of the flow extending above the channel levees. The expanded model allows steady turbidity currents to evolve to a uniform, or equilibrium, state where mass, momentum, and energy gained through sediment and clear‐water entrainment processes are balanced by the mass, momentum, and energy lost to flow stripping and overspill. We perform a sensitivity analysis of the expanded model to assess how changes in channel (e.g., slope, channel height, width, bed friction, and radius of curvature) and flow (e.g., sediment grain size, suspension cloud concentration, and turbulence) properties affect the equilibrium flow conditions. By varying the model inputs from half to double their base case values, we find that the equilibrium values can change by up to a factor of 2. We find that the equilibrium conditions, including the flow Richardson number, were generally most sensitive to changes in slope, channel height, grain size, and suspension cloud concentration. Additionally, we identify model parameter space where Richardson subcritical equilibrium flow is possible. The fact that turbidity currents can attain equilibrium, and particularly subcritical equilibrium, might help elucidate the long turbidity current runout distances on low slopes inferred from extensive submarine channel levee systems.