Three-Dimensional Numerical Modeling of Confined and Unconfined Turbidity Currents – Model Development and Validation

Abstract

Turbidity currents are sediment-laden gravity currents that transfer sediments to deep sea and lake floors through erosion and deposition. These deposits form subaqueous fans in deep marine environments and can reduce reservoir storage capacity, complicating management. Deep sea deposits often contain hydrocarbons like oil and gas. Field measurements of turbidity currents are challenging due to the risk of damage to measuring instruments, and laboratory experiments do not accurately simulate these currents. Thus, numerical modeling is crucial for understanding their formation and properties, and for locating oil and gas fields within deep sea turbidites.A 3D two-phase numerical model (water and solids) is used to simulate underflow turbidity currents. This model solves the Reynolds-Averaged Navier-Stokes equations and uses the Eulerian approach, with turbulence closure achieved by the RNG k-ε model. It simulates both continuous unconfined currents and surge-like confined currents. Calibration and validation against experimental data show the model accurately replicates key features of turbidity currents.Model results indicate that fine particles remain suspended longer, providing additional density that drives the current further with increasing downstream velocity. Vertical concentration profile shows two distinct layers: a denser, faster-moving bottom layer parallel to the bed, and a slower, more diluted upper layer affected by entrainment and mixing with ambient fluid. Turbidity currents are supercritical on sloped channels and subcritical on mild sloped unconfined seafloors or reservoir bottoms. In following article, hypothetical simulations using this model will further explore various characteristics and deposits of turbidity currents on a field scale.

Keywords

• turbidity current
• submarine fans
• multiphase flow
• confined
• unconfined