This thesis investigates the wake dynamics of an H-type vertical axis wind turbine using particle image velocimetry (PIV). Two-component PIV is used to study vorticity shedding and horizontal wake expansion at the turbine mid-span plane. Stereoscopic PIV is performed on 7 cross-stream vertical planes to analyze tip vortex dynamics and the evolution of 3D wake structures. The experimental results show asymmetrical vorticity decay in the horizontal plane, with faster decay on the leeward side. Tip vortices are stronger than shed vortices. Near the turbine axis, tip vortices move inboard behind the rotor before moving outboard towards the windward side further downstream. Vertical