This paper presents a numerical study involving flows past vertical axis wind turbines (VAWT). Our motivation is to develop a fast numerical tool with a low computational demand while still retaining an accuracy which can be deemed acceptable in the initial stages of the design process of VAWT farms. The governing equations of our simulations are the unsteady Reynoldsaveraged Navier Stokes (URANS) equations, which are mathematically closed using a conventional two-equation closure framework. However, to save on the computational expense, we combine the URANS equations with the so-called the actuator line method (ALM) to represent the effects of rotating turbine blades on the flow field. By using this method, the need to include the exact blade geometry is avoided. Consequently, the computational grid does not require numerous cells to capture the boundary layer effects. We present results of two different kinds of configurations: (i) flow past a single VAWT, and (ii) flow past a pair of counter-rotating VAWTs placed near to each other (twin-rotor configuration). Our main findings are that (i) the coefficients of power developed by a turbine is larger in a twin-rotor configuration than a single isolated rotor, and (ii) as the distance between the centers of the two rotors in the twin configuration decreases, the influence of relative direction of rotation of the two rotors seems to reduce. This work is expected to aid in arriving at optimized turbine configurations for large wind farm applications.