As tidal and hydrokinetic energy systems develop, new tools are needed to assess quantitatively the effects of turbines on the environment and to estimate their performance. When installed in an array, turbine wakes interact, increasing the complexity of the flow and changing their performance. Experimental and numerical approaches have been employed to analyze flows with multiple turbines, but it is not yet clear which level of detail is necessary to represent the flow hydrodynamics and the details of the devices. In numerical approaches, questions remain on the selection of turbulence models and turbine representations, since more realistic but computationally expensive methodologies not necessarily produce an improvement on the understanding of these flows. In this investigation we perform simulations of turbine arrays to study the hydrodynamics of wakes and their interactions, comparing with experiments and previous simulations. We propose a methodology that couples detached-eddy simulations (DES) with Blade Element Momentum (BEM), showing that by capturing the dynamically-rich coherent structures of the flow, we improve the description of mean quantities and turbine performance. The results show that for downstream turbines, there is an accelerated wake development, increasing the temporal variability of the bed shear stress, and the power and thrust coefficients.