Performance and wake interaction between two aligned vertical turbines are investigated by solving the three-dimensional Navier-Stokes equations with the κ−ω SST IDDES turbulence model. Specifically, the impact of longitudinal spacing between the upstream and downstream turbines is examined. The numerical results show that as the longitudinal distance increases, the performance of the downstream turbine shows a quadratic growth. This is phenomenon is strongly correlated to the wake recovery of the upstream turbine. Based on the velocity and turbulence distribution, the wake of the upstream turbine could be divided into three distinct zones. However, the zone characterized by low axial velocity and turbulence level is not observed in the wake of the downstream turbine. This difference primarily arises from the high turbulence present in the incoming wake from the upstream turbine, combined with the turbulence generated by the downstream turbine. Interestingly, regardless of the longitudinal distances between the turbines, the downstream turbine displays similar wake patterns for different streamwise distances between turbines. This consistency is attributed to the influence of the upstream turbine's wake on the stability of the downstream turbine's wake. The downstream turbine is suggested to be positioned in the zone where the upstream turbine's wake has fully developed.