In the past few decades, the growing capability of Computational Fluid Dynamics (CFD) has pushed the research in the field of ship hydrodynamics from simple to complex, covering the prediction of ship resistance, seakeeping, self-propulsion and maneuvering. However, the predictions of free maneuvering problems are especially difficult, mostly due to limitations of traditional meshing methodologies when handling with moving objects. In this paper, a series of numerical computations are carried out to study the free maneuvering characteristics of fully appended ONR Tumblehome ship model with twin rotating propellers and rudders. All the numerical simulations are carried out by our in-house solver naoe-FOAM-SJTU, which is developed on the open source platform OpenFOAM and mainly composed of a dynamic overset grid module and a full 6DoF motion module with a hierarchy of bodies. The objective of this paper is to validate our CFD solver naoe-FOAM-SJTU in predicting free maneuvering problems. In the present work, CFD-based method coupling with dynamic overset grid approach is applied to investigate the free maneuvering tests, ie full 6DoF self-propulsion and turning circle tests. For the self-propulsion simulation, open water performance of the propeller and towed condition of bare hull will be computed beforehand. The simulation of the towed condition can give an approximate flow field of the selfpropulsion and the flow field can be mapped as the initial state of the self-propulsion to reduce the large amount of calculation and avoid divergence at the beginning. Open water performance will give the hydrodynamic characteristics of the rotating propeller. Grid convergence study is applied in this condition to validate the numerical results and the computed results will also be compared with the experimental data. The full 6DoF self-propulsion is carried out by introducing a PI controller to update the rate of revolutions (RPS) of the propeller to achieve the target speed and a P controller for rudder to keep the ship going straight forward. The present numerical result for the RPS is underestimated by 1.7% compared with the experimental data, which indicates that the present approach is applicable for the full 6DoF self-propulsion simulation. As for the turning circle simulation, the fully appended ship hull is first going straight with the propeller RPS obtained by the previous self-propulsion calculation and then the ship rudder is gradually turned to the desired angle to start turning circle. Good agreement is achieved for the ship model trajectory. Furthermore, the detailed flow visualizations are also presented at several critical times during the transient phase for turning circle simulation with the aim to explain how the flow characteristics affect the hydrodynamic performance.