CFD modeling of entrance and exit geometries of a wind speed accelerator.

Abstract

Current wind power technology is not economically feasible throughout most of the United States due to low average wind speeds. A design for a small-scale wind concentrator device suitable for use in areas of low wind velocity was tested using computational fluid dynamics (CFD). Using a novel approach, the device seeks to accelerate incoming air above minimum velocities required for economical power generation. The novel approach employs a funnel shaped inlet with relief vents along the circumference, so as to alleviate backpressure. Both inlet and outlet sections utilize funnel shapes with both parabolic and hyperbolic regions. All geometry and mesh models were created using ICEM 12.1. Simulations were performed using Fluent 12.1.2.Turbulence was modeled using the standard k-epsilon model. All mesh models contained roughly 500,000 unstructured computational cells. CFD simulations predict a 2.53X acceleration of incoming air through the throat of the device (based upon a 2 m/s ambient wind speed). Similar performance was seen across the range of 1-12 m/s. Analysis focused on testing various designs to reduce losses due to turbulent energy and backpressure, with a focus on maximizing the throat velocity where a turbine can be located. Tested variables include funnel shape, lengths of both inlet and outlet funnels, and curvature of the inlet rim. In addition to design of the device, the effect on airflow through the relief vents by a surrounding casing was also analyzed.

CFD modeling of center cones, vortex breakers and pressure relief slits in a wind speed accelerator.

“…While designing the concentrator, this procedure for model creation and data collection proved effective in all cases. Some parts of the inlet and exit geometry were tested jointly as part of a separate project, and some results of both are presented here to completely describe the evolution of the overall design (Russ, 2011). The first item addressed was finding an optimized intake geometry.…”

“…These models were run with the new equation set (Russ, 2011) and it was concluded that the third or fourth curve was the best designs for the inlet. These curves showed an acceleration of 15%, from the ambient flow of 2 m/s to 2.3 m/s in the device throat, with a turbulent model…”