The goal of this thesis is to analyze the flow field and power generation from a vertical axis wind turbine (VAWT) by extending the Actuator Cylinder Model to include the viscous effects. Turbulent flow effects in the Actuator Cylinder Model are modeled by solving the Reynolds-Averaged Navier-Stokes (RANS) equations with the Spalart-Allmaras (SA) turbulence model in ANSYS FLUENT. A study is performed to establish mesh independence of the solutions. Numerical solutions on a fine mesh are compared to existing theoretical results based on inviscid theory for a series of flow conditions and turbine sizes. Similar trends in the present turbulent flow results are found as in the inviscid results for downstream velocity and pressure profiles. The Betz limit is found not to be applicable to vertical axis wind turbines. To consider wake interactions, the Actuator Cylinder Model is extended to two and three turbine cases. Power densities are computed to determine the optimal vertical and downstream distances between turbines. For the application to small scale airborne turbines, an increased freestream velocity is employed with two and three turbine models to simulate the effects on performance and power generation at higher altitudes with greater wind velocity. Differences between the present numerical results and inviscid theory are discussed
