## 1 Introduction
Therefore, to evaluate both the capability of 3D models and their calculation efficiency, this paper attempts a simplified 3D model-MIKE 3 FM for simulating dam-break flows. The MIKE 3 model has been applied to investigations of several hydrodynamic simulations in natural water basins. It has been used by [PERSON] et al. [36], [PERSON] and [PERSON] [37] and [PERSON] and [PERSON] [38] for hydrodynamic simulations in field studies. Even with the considerable work of these authors, there have been very few studies on the modelling of dam-breaks using the MIKE 3 FM. In addition, research comparing the performance of 3D shallow water and fully 3D RANS models for solving the problem of dam-break flood propagation has yet to be reported. To fill this gap, the primary objective of the current study is aimed at evaluating simplified 3D SWE, detailed RANS models and analytical solutions for simulating sudden dam-break flows to analyze their accuracy and their applicability to the dam-break problem. There is a need to validate the numerical models before attempting to perform a hydrodynamic simulation to solve real-life dam-break problems. It is an accepted practice to check numerical models using a set of experimental benchmarks. Limited measured data have been acquired in recent years, due to the difficulties of obtaining field data. This paper draws from the validation proposed by two test cases by [PERSON] and [PERSON] [30] and [PERSON] et al. [39]. In the first experiment, which was conducted by [PERSON] and [PERSON] [30], there was a dam-break flood wave during the initial stage over different tailwater levels, and it provided measurements of the free surface profiles. [PERSON] and [PERSON] [30] compared only the free surface profile calculated by the numerical solutions from the 2D SWE and 3D RANS involving Flow-3D software during the initial stage. During the second experiment, which was designed by [PERSON] et al. [39], measurements from this experiment were used to validate the numerical models aimed at simulating the flood propagation and providing measured data, including free surface profiles during the late stage, time evolutions of the water levels, and velocity variations. A study by [PERSON] et al. [39] primarily focused on the experimental investigation, and it only mentions the water level with [PERSON]'s solution during the initial stage, because in a 1D analytical solution without boundary conditions (with an infinite channel length both upstream and downstream), it makes no sense to compare the experimental results with the Ritter (dry bed) or Stoker (wet bed) solutions when the reflections from the walls affected the depth profiles, and when further comparisons with numerical simulations for the experiments in Reference [39] are poor. In aiming directly at these problems, this paper will present a full comparative study on free surface profiles, water depth variations and velocity variations during the entire dam-break process. Here, numerical simulations of the dam break wave are developed using two 3D models for an instantaneous dam break in a finite reservoir with a rectangular channel that is initially dry and wet. This paper is organized as follows: The governing equations for the two models are first introduced before the numerical scheme is described. The typical simplified test cases were simulated using 3D numerical models and a 1D analytical solution. The model results and the ways in which they compare with the laboratory experiments are discussed, and simulated results of the variations in hydraulic elements over time at different water depth ratios are presented before the conclusions are drawn.