The wind power contribution for the global energy matrix and its technological and commercial maturity becomes an important fact for the sustainable energy development. The CFD studies gain importance with the computational progress to improve the efficiency of wind turbines on the aerodynamic criteria. The RANS models show the best relation between accuracy and required computational effort. The present article investigates the application of Arbitrary Mesh Interface (AMI) in transient regime and k-omega SST turbulence model in its standard setting to obtain the Power Coefficient of a small HAWT by using OpenFOAM (pimpleDyMFoam). The numerical results were comparable with the field test results and the numerical results obtained with frozen rotor approach, in stationary regime (simpleFoam) and the same turbulence model. The findings showed good agreement between simulations and experiments. The moving mesh approach with layers addition over the blade's surface, for the adjustment of y+ values, was determinant for the results and reproduced well the three-dimensional dynamic effects of flow for this application. The frozen rotor approach resembled the condition of a stopped rotor and its weaknesses are presented and discussed. The numerical results lied between the highest and the mean experimental values and consistently within the confidence interval. (C) 2019 Elsevier Ltd. All rights reserved.