Abstract
Typical wind turbine systems are sufficiently large so as to require extensive physical space for their installation and operation. These requirements preclude the use of turbines in crowded, urban environments. On the other hand, smaller turbine systems may find practical application as rooftop units, installed atop tall buildings. Such rooftop units must be much smaller than their ground-based counter parts. In this paper, a new, vertical-axis wind turbine has been analyzed by using a two-step numerical procedure. The design consists of two turbine cups that are positioned with 180o separation. In the first step of the analysis, a complete numerical simulation of the wind-flow patterns across the cup with wind impacting angles spanning 360o was completed. From these calculations, it was possible to determine the functional relationship between rotational forces, relative wind speed, and the relative angle of wind approach. The second stage of numerical procedure was a time-wise integration of the instantaneous angular velocity of the wind turbine. These calculations were carried out until the turbine had achieved quasi-steady motion. The corresponding cycle-averaged angular velocity (terminal angular velocity) was then determined. This second stage was completed for a wide range of wind speeds so that a functional dependence of the turbine rotational velocity on the wind speed could be found. This functional relationship enables a user to predict the operational response of the wind turbine based on a known and steady wind velocity.