Abstract
Abstract. Ducted wind turbines (DWTs) can be used for energy harvesting in urban areas where non-uniform flows are caused by the presence of buildings or other surface discontinuities. For this reason, the aerodynamic performance of DWTs in yawed-flow conditions must be characterized depending upon their geometric parameters and operating conditions. A numerical study to investigate the characteristics of flow around two DWT configurations using a simplified duct-actuator disc (AD) model is carried out. The analysis shows that the aerodynamic performance of a DWT in yawed flow is dependent on the mutual interactions between the duct and the AD, an interaction that changes with duct geometry. For the two configurations studied, the highly cambered variant of duct configuration returns a gain in performance by approximately 11 % up to a specific yaw angle (α= 17.5∘) when compared to the non-yawed case; thereafter any further increase in yaw angle results in a performance drop. In contrast, performance of less cambered variant duct configuration drops for α>0∘. The gain in the aerodynamic performance is attributed to the additional camber of the duct that acts as a flow-conditioning device and delays duct wall flow separation inside of the duct for a broad range of yaw angles.
Highlights
Global energy demand is expected to more than double by 2050 owing to the growth in population and economy (Gielen et al, 2019)
The 2D unsteady RANS (URANS) approach combined with the numerical duct-actuator disc (AD) model has been adopted for the results presented hereinafter
Of the two duct geometries investigated, the DonQi® D5 duct configuration returns a gain in CP up to and including a yaw angle α = 17.5◦; thereafter any further increase in α results in the CP drop
Summary
Global energy demand is expected to more than double by 2050 owing to the growth in population and economy (Gielen et al, 2019). Igra (1981) experimentally studied the effects of yaw on the performance of DWTs. Eight geometries were investigated using different duct profiles and an actuator disc (AD) model to represent the turbine. Incorporating the real turbine geometries, which would necessarily have to be different for ducted and for bare operation, would confuse turbine and duct effects, preventing a proper analysis of DWTs in yawed flow. The numerical predictions agree reasonably well, both in axial- and yawed-flow conditions, when compared to the measurements on the Tjæreborg 2 MW field turbine This model is employed by Tongchitpakdee et al (2005) to study yaw; the NASA Ames experiments of the National Renewable Energy Laboratory (NREL) Phase VI turbine are modelled for yaw angles from 0 to 45◦ to find reasonable agreement with the experiments.
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