Tidal current energy is one of the most promising renewable energy resources. The prediction of the hydrodynamic loads and power efficiency are the critical issues for verifying the new designs. Besides, Optimization of turbine arrangement is important for a tidal turbine farm. The hydrodynamic behavior of a turbine operating in the wake of an upstream turbine needs to clarify. In this paper we present a CFD approach in which the CFD library of OpenFOAM is utilized for prediction of the performance of a three bladed horizontal axis tidal turbine (HATT) in a test tunnel environment. The Reynolds Average Navier Stokes (RANS) equation with Shear Stress Transport (SST) turbulence model is applied. The steady-state solver is tested for present numerical simulation. The Multi Reference Framework (MRF) method is adopted for dealing with grid relative rotation. Turbulence models effects and the mesh generation are well described. The resultant power and thrust coefficients of these simulations are compared with experimental results at various tip speed ratios (TSRs).