A Numerical Investigation Of Slope Influence On The Flow And Deposition Of Turbidity Currents

The flow and sedimentary characteristics of turbidity current are of great significance for the exploration and development of seabed oil and gas.Previous studies have shown that slope has an important impact on turbidity current in two-dimensional slope break channels,but there is no study on the impact of slope on turbidity current in three-dimensional channels.In this study,Navier Stokes equation based on Reynolds average and k-ε modified by buoyancy term are selected.The three-dimensional numerical simulation of the flow,deposition or erosion of turbidity current in trapezoidal straight and curved channels with slope break with slope gradient of 0.5°,2°,5° and 8° and slope gradient of 11.31° is carried out in the turbulence model.The major findings are as follows:1)the flow velocity of turbidity current increases with the increase of flow gradient in both straight and curved channels,However,the growth rate of its velocity is gradually slowed down by the entrainment of turbidity current on the surrounding fluid;2)There is a high similarity between the vertical section velocity trend in the three-dimensional turbidity current channel and the two-dimensional vertical section velocity trend with different slopes.The maximum section velocity is close to the bottom of the channel.With the increase of slope,the maximum velocity of longitudinal section increases correspondingly,and the closer the position of the maximum velocity is to the bottom of the river;3)With the increase of slope,the entrainment effect of turbidity current on the surrounding environment fluid is strengthened,and the density at the floodplain on both sides increases,especially at the straight slope break,the top of the curve and after the slope break;4)After multiple flows of turbidity current,the deposition at the floodplain and channel bottom before the slope break of straight channel decreases with the increase of slope,and even erosion occurs at high slope.The deposition at the slope break and floodplain after slope break increases with the increase of slope;5)The deposition of low slope curved channel at the floodplain presents concave outer bank and convex inner bank.With the increase of slope,the floodplain presents outer bank deposition and inner bank erosion.When the slope is larger,both inner and outer banks will be eroded.The deposition at the bottom of the channel presents outer bank deposition and inner bank erosion.When the slope increases,the outer bank deposition decreases or even erodes;6)When the slope is high,the outer Bank of the top of the upstream curve flows into the downstream straight channel after stripping,which makes the downstream flow and deposition more complex;7)With the increase of slope,the sediments with larger particle size are mainly deposited at the bottom of the channel,especially at the bottom of the outer Bank of the curve,which can be the focus of oil and gas exploration.These characteristics have certain practical application value for the application of seabed turbidity current flow and sediment deposition in practical hydraulic engineering,the prevention of marine disasters,and the detection of oil and gas storage in seabed sediment sedimentary strata.