The aerodynamic interaction of vertical axis wind turbines in several array configurations was studied by conducting a series of wind tunnel measurements. Four configurations of two- and three-turbine arrays were tested and their results were compared with that of the isolated reference case. Two pairs of counter-rotating and co-rotating vertical axis wind turbines were tested where the free-stream wind was perpendicular to the two side-by-side turbines. The counter-rotating configuration resulted in a slight improvement in the aerodynamic performance of each turbine compared to the isolated case, while the co-rotating installation caused a slight performance reduction of turbines at some free-stream velocities. Several measurements were also performed for three-turbine arrays with different spacing where a vertical axis wind turbine was operating downstream of a counter-rotating pair, perpendicular to the free-stream wind. An enhancement in the aerodynamic performance of the downstream turbine was observed in almost all arrays and at most tested wind speeds. For the array spacing studied, the optimum range of the streamwise distance of the downstream turbine from the counter-rotating pair and the spacing between the pair was determined to be about three and one rotor diameters, respectively. (C) 2016 Elsevier Ltd. All rights reserved.