Integrated Exploration Of Deposition Physical Simulation And Numerical Simulation On Shallow Water Delta

Deposition simulation is an important experimental method and means in sedimentology theory,including physical simulation and numerical simulation.Both have their own advantages and disadvantages.Physical simulation can more intuitively display the natural sedimentation process,but it is costly and highly random;Numerical simulation has low cost and a long time span,but effective numerical simulation requires establishing a complete set of control equations,closure conditions,and calculation methods,and requires physical simulation to provide parameters.Therefore,the increasing integration of deposition physical simulation and numerical simulation is an important trend in the development of physical simulation technology.The combination of the two not only helps to record the sedimentary process in detail,but also enables the precise description and characterization of the spatiotemporal distribution characteristics of deposition bodies.In recent years,shallow water deltas have gradually become the focus of research by various experts and scholars.The main factors affecting the growth and development of shallow water deltas include ancient structures,ancient terrain,ancient climate,and ancient water flow.There is a lack of more comprehensive quantitative analysis of the specific impact of the main controlling factors on it.Therefore,the author selected three influencing factors,namely,sediment ratio,lake level change,and estuarine flow,and adopted a method of combining deposition physical simulation and numerical simulation,analyze the deposition evolution process of shallow water delta and the impact of control factors on it,and conduct quantitative analysis using the length-width ratio,width-thickness ratio,growth rate,area,shoreline roughness,and other indicators of deposition bodies.Through literature research and using the similarity theory of the natural model method,a single slope experimental device was designed to carry out single-factor deposition physical simulation experiments with different sediment ratio,different lake level changes,and different estuarine flows,visually displaying the growth and development process of shallow water deltas.The experimental results showed that high sediment ratios,large lake level drops adequate inflow is conducive to the expansion of the distribution range of shallow water deltas and the development of frontal lobes.The author also designed and conducted numerical simulation experiments based on modern sedimentology theory,from the formation of initial estuarine dams to the formation of distributary channels,abandoned channels,and frontal lobes,to conduct a more detailed quantitative analysis of the growth and development of shallow water deltas.This not only made up for the shortcomings of sedimentation physical simulation experiments,but also made the analysis of results more comprehensive.The experimental results show that:(1)Under the condition of high sediment ratio,it is easy to form deposition bodies with a large number of channels,strong stability,large distribution area,thin thickness,irregular shoreline,and a large number of pods;(2)As the decrease in lake level increases,the morphology of shallow water deltas gradually changes from sheet shaped to leafy and then to bird foot shaped,with poor continuity and an increase in the number of river channels.The convergence of the main body of the delta is stronger,which helps to develop deposition bodies forward and form shallow water deltas with a large distribution range and a large number of branches.The estuary has a large flow rate,resulting in a larger number of river channels formed by shallow water deltas and a larger distribution range of deposition bodies;(3)The convergence of the main body of shallow water deltas is better,and more lobes are generated at the front edge.With the increase of estuary flow,the morphology of shallow water delta gradually changes from checkered to leafy,and the estuarine flow is 1000m3/s is a reference threshold.Comparing the results of physical simulation with numerical simulation,it was found that the similarity was high.The deposition evolution mechanism of shallow water delta in both modes is consistent,with first longitudinal elongation and then transverse broadening.The final morphology of the deposition body is in a leaf like shape,and the influence of different control factors on the morphological parameters of shallow water delta is also consistent in both modes.It indicates that numerical simulation has certain feasibility,and combining it with physical simulation has important theoretical significance and practical value in promoting the exploration and research of oil and gas reservoirs.