The project will perform studies on wind and water turbines by using ANSYS Fluent. Prototypes of the vertical-axis turbines with 7.5 kW and 12 kW rated power of water and wind turbine respectively designed by research group at Uppsala University has been deployed in the river Dalälven and Marsta. The vertical-axis turbines can work with stream flow from any direction without the need of a yawing mechanism which reduces the risk of failures and simplifies the installation. With the advancement of the vertical-axis turbine concept, we need reliable simulation tools to analyses the physical quantities. Important parameters are the velocity field to see effect the turbine wake and tower and to determine the incoming streams on the hydrofoils and airfoils, and also the blade forces, which determines the loads on the structure and the power generated by the turbine. Accurate modelling of the turbine in is therefore crucial to understand which aerodynamic phenomena can be correlated to the experimental trends. CFD calculations can provide further details of unsteady nature of the interactions within the turbine. This will not have been possible without access to high-performance computing (HPC) resources like NAISS. We hope the results can lead to improved turbine performance and reliability.