Wind turbine efficiency typically focuses on the shape, orientation, or stiffness of the turbine blades. In this thesis, the focus is instead on using static fixed airfoils in proximity to the wind turbine to control the airflow coming out of the turbine. These control devices have three beneficial effects. (1) They gather air from “higher up” where the air is moving faster on average (and therefore has more kinetic energy in it). (2) They throw the used (and slowed down air) downwards. This means that any turbines in the wind farm behind the lead turbines do not get “stale” air. (3) These control devices provide a large stabilizing lifting force for floating off-shore turbines. In this study, Reynolds-Averaged Navier-Stokes (RANS) simulations of an aligned array of two wind turbines along with various designs of these control devices is studied. The recovery in the velocity at the inlet plane of downstream turbine due to the controlled flow facilitated by these devices is measured with respect to the average streamwise wind velocity at the inlet plane of upstream turbine. A customized numerical solver was written in C++ using Opensource Field Operation And Manipulation (OpenFOAM) to model the turbines as actuator discs with axial induction and to generate an inlet velocity field similar to a turbulent atmospheric boundary layer (ABL). All the design configurations use a streamlined (airfoil shaped) structure, at an angle of attack carefully selected to prevent flow separation depending upon its location around the turbine. For strong wake displacement, the devices are placed in proximity to the upstream wind turbine so as to facilitate a substantial downwash of the faster wind from upper layers of the ABL and at the same time deflect the wake out of the way of the downstream turbine. Also, the pressure coefficient across the upstream turbine augmented with these devices can sometimes become more negative than a bare turbine, which in turn increases the mass flow rate of air passing through it, thereby also increasing the leading turbine’s efficiency slightly.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:masters_theses_2-1592 |
| Date | 27 October 2017 |
| Creators | Bader, Shujaut |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses |
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