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    Numerical investigation of synthetic jet based flow control for vertical axis wind turbines

    Author
    Menon, Ashwin
    View/Open
    172969_Menon_rpi_0185N_10438.pdf (5.664Mb)
    Other Contributors
    Sahni, Onkar; Gandhi, Farhan; Amitay, Michael;
    Date Issued
    2014-08
    Subject
    Mechanical engineering
    Degree
    MS;
    Terms of Use
    This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.;
    Metadata
    Show full item record
    URI
    https://hdl.handle.net/20.500.13015/1181
    Abstract
    This numerical study focuses on the implementation of active flow control using synthetic jets on vertical-axis wind turbine (VAWT) blades. This study demonstrates that synthetic-jet based flow control improves the efficiency of the turbine and reduces the risk of structural fatigue.; The idea of using synthetic jets is to control the variation in flow-induced loading during each rotation cycle. At first the dominant location of the flow separation is determined for both airfoils. The jets are then placed at this location. Jet parameters of blowing ratio and reduced frequency are specified within a range (i.e., O(0.5-1.5) and O(1-10), respectively) and their effects on jet performance are studied. The jets are activated only in a selected portion of the rotation cycle. This is referred to as the partial cycle control in contrast to the full cycle (the latter is found to be detrimental). For given jet parameters, simulations results are used to determine whether the jets improve axial force, flow separation and blade-vortex interaction. At blowing ratio of 1.5 and reduced frequency of 5, we observe above 12% increase in the average axial force over the rotation cycle for both airfoils.; In VAWTs, the blades experience a significant variation in the angle of attack over each rotation cycle and associated with it are sudden changes in the flow-induced loading on the blades. For example, a sudden variation in blade loading is experienced due to the detachment of the leading edge vortex at high angles of attack. This is in-turn reduces the axial force and hence the overall power output of the turbine. Additionally, such force variations lead to structural fatigue and possibly failure. Current simulations consider a cross-section of a three-blade VAWT model (with straight blades). VAWT models with two different airfoils, NACA 0018 and DU 06-W-200, are considered at tip-speed-ratios of 2 and 3. In these simulations, unsteady, Reynolds-averaged Navier-Stokes equations along with the Spalart-Allmaras turbulence model are employed, where stabilized finite element method is utilized along with an implicit time-integration scheme.;
    Description
    August 2014; School of Engineering
    Department
    Dept. of Mechanical, Aerospace, and Nuclear Engineering;
    Publisher
    Rensselaer Polytechnic Institute, Troy, NY
    Relationships
    Rensselaer Theses and Dissertations Online Collection;
    Access
    Restricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.;
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