Two- and three-dimensional nested simulation by using FEM and FVA to analyze flows in an estuary

This paper presents an mixed-dimensional model which was developed to simulate numerically complex current patterns in a classical horn-type estuary, the Hang-Zhou Bay, situated in the Bast Chinaʹs coast line. The multidimensional mathematical model consists of a three-dimensional finite volume approach submodel being nested with a two-dimensional finite element model. The two-dimensional Finite Element Method (FEM) was employed to solve shallow-water equation in whole estuary (far field) and the three-dimensional Finite Volume Approach (FVA) was utilized to solve nonsimplified Reynolds equation in the near field of the intake structure of the cooling water system of an electric power plant, namely, the Jia-Xing Electric Power Plant. Reasonable agreement was found between modeled currents and observed field data. The results of numerical computations were directly used to analyze the tidal currents, to analyze the effect of a deep pool in front of the intake structure, and to predict the possible variation of bottom topography in association with empirical analyzing and modeling. The established model, exploited the merits possessed by both FEM and FVA, can provide sufficient details of current patterns in natural waters for engineering application, with a reasonable accuracy demanded by a practical problem and at a lower computational cost. The development of this computational method provided a feasible approach for simulating three-dimensional flows in natural waters, which is different from the conventional layered quasi-three-dimensional models.