Performing high-fidelity numerical simulations of turbulent flow in multi-turbine wind farms remains a challenging issue mainly because of the large computational resources required to accurately simulate the large disparity of spatial scales. To address this challenge we develop herein a new Adaptive Mesh Refinement (AMR) flow solver to enhance the resolution and improve the efficiency of the Virtual Wind Simulator (VWiS) code,1 which is capable of simulating multi-turbine wind farms in complex terrain. We extend the Curvilinear Immersed Boundary (CURVIB) approach incorporated in the VWiS code to unstructured Cartesian grids with strong coupling between multiple levels of refinement. The challenging issues of flux mismatching or pressure discontinuity across fine/coarse interfaces are overcome by the resulting fully unstructured approach. The efficiency and accuracy of the solver is demonstrated by solving the Navier-Stokes equations in driven cavity flows. Large-eddy simulation (LES) of turbulent flows past a stand alone wind turbine, which is modelled by using the Actuator Line Model (ALM), reveal that computed results obtained in locally refined domains are in good agreement with the experimental measurements. These simulations also show the ability of our method to simulate the rich dynamics on the wake of the turbine.