WIND DESCRIPTION FOR ROOF LOCATION OF WIND TURBINES: A design guideline for the required height of a wind turbine on a horizontal roof of a mid- to high-rise building

摘要

This paper gives design guidelines, based on free streamline theory and Computational Fluid Dynamic calculations, for the siting of wind turbines on horizontal roofs of mid- to high-rise buildings. It discusses the calculated height of the "separating streamline" on a horizontal roof of a two-dimensional building. The CFD calculations are carried out with Fluent 5.5 and are based on the RNG k-e turbulence model. The separating streamline is the dividing streamline between the low velocity in the turbulent separation bubble on the roof and the (high) velocity above the bubble. For high roughness around the building less flow has to be pushed aside by the building compared to low roughness, which gives a more parallel like undisturbed flow. Therefore the separating streamline for parallel flow will be higher above the roof compared to the separating streamline in boundary layer flow. Free streamline theory gives the separating streamline for parallel flow, which thus is the highest free streamline possible compared to the CFD calculations of the free streamline in boundary layer flow. Therefore, free streamline gives a save height for the lowest blade tip of a wind turbine on a horizontal roof in order to avoid the turbulent separation bubble.