Two-dimensional Hydrodynamic Simulation For Complex Water Systems

In nature, water systems are often connected with several parts of different scalesand different types, such as river and lake systems, river and bay systems, channel andreservoir systems. Due to terrain characteristics difference among these parts, as wellas applicability differences of different models, the hydrodynamic simulation of thiskind of water systems often need to be split and then coupled by several differentmodels. The most popular one is1D–2D coupled numerical model. Coupled simulationusually faces problems of low numerical precision and calculation instabilities near thecouple interfaces. Therefore, this research proposes and develops a new2D modelwhich is applicable to hydrodynamics simulation of multi-terrain area.Based on the comparison between1D model and2D model, this work raises anidea of taking terrain changes into2D model’s computational elements. Proceededfrom flow continuum and momentum conservation, meanwhile, through introducingsome concepts (like water level coefficient, equivalent water depth, equivalenthydraulics radius, et al.), we derive improved shallow water governing equationswhich consider the terrain changes in each control volume. This work usesOpenFOAM as development platform to finish the discretization and solution of thegoverning equations; raises a technique of laying inner points into every grid element,which could effectively describe terrain characteristics within elements, then obtain therelationships between water level coefficient, equivalent water depth, equivalenthydraulics and water level. Taking advance of this technique, we develop the new2Dmodel called InnerParts2D.Firstly, InnerParts2D model is used to simulate traditional1D problems. Thispaper use a virtual constant uniform flow example and the Sanya River network casetest it. Compared with several other models’ simulation results, the InnerParts2D caneffectively simulate traditional1D problems. Then, InnerParts2D is applied in theSanya Bay-River System and produces quite good results. This job realizes a goal thatone model simulates a complex water system consisting of several different type ofparts (which usually has to be treated with1D-2D coupled model) integrally. In theSanya Bay-River System case, we also put some effort to analyze introducing variables’changings in several typical elements during the simulation period, for the sake oftelling how the new2D model improve simulating results. This research gives the following conclusion: because of improvements of terrainprecision, InnerParts2D could produce a much better result than the traditional2Dmodel. This makes it possible to simulate complex terrain waters with coarse mesh. Inaddition, InnerParts2D is capable to be applied in river networks’ study naturally,which makes integrally simulation of river-lake-bay complex water systems possible.In a word, InnerParts2D model will become a powerful tool for the future large-scaleand complex waters’simulation.