Simulation of Morphing Blades for Vertical Axis …

1 Simulation of Morphing Bladesfor Vertical axis wind TurbinesJennifer TanA ThesisIn the Department ofMechanical, Industrial and Aerospace EngineeringPresented in Partial Fulfillment of the Requirementsfor the Degree ofMaster of Applied Science in Mechanical Engineering atConcordia UniversityMonreal, Quebec, CanadaAugust 2017c Jennifer Tan, 2017 CONCORDIA UNIVERSITY School of Graduate Studies This is to certify that the thesis prepared By: Jennifer Tan Entitled: Simulation of Morphing Blades for Vertical axis wind Turbines and submitted in partial fulfillment of the requirements for the degree of Master of Applied Science (Mechanical Engineering) complies with the regulation of the University and meets the accepted standards with respect to originality and quality. Signed by the final Examining Committee: _____ Chair Dr. Mingyuan Chen _____ Examiner Dr. Samuel Li _____ Examiner Dr.

2 Brian Vermeire _____ Supervisor Dr. Marius Paraschivoiu Approved by: _____ Martin D. Pugh, Chair Department of Mechanical and Industrial Engineering _____ 2017 _____ Amir Asif, Dean Faculty of Engineering and Computer Science AbstractSimulation of Morphing Bladesfor Vertical axis wind TurbinesJennifer TanThe Simulation of flow through Vertical axis wind turbine (VAWT) is characterized byunsteady flow where the blade experiences varying angles of attack and Reynolds number asit completes a cycle. Therefore, the lift generated also varies as a function of its rotationalposition relative to the incoming freestream velocity. In order to improve the performance ofthese turbines the blade can take advantage of smart materials developed for control surfaceactuation. The aim of this paper is to investigate the effect of Morphing Blades on theaerodynamic performance of the turbine Blades .

3 The study uses commercial software AnsysFluent pressure-based solver to investigate the flow past the turbine Blades by solving the 2 DUnsteady Reynolds-Averaged Navier-Stokes (URANS) equations. In order to simulate themorphing blade for VAWT, a sliding mesh method is used to simulate the VAWT rotationwhile a user-defined function (UDF) is written for the blade Morphing flexure motion. Thisentails the use of dynamic mesh smoothing to prevent the mesh from having negative cellvolumes. Although the dynamic mesh strategy has been successful in preserving the cellquality, it has been shown that the proposed method of simulating the Morphing blade onVAWT is inadequate due to unphysical solutions. Finally, the effect of Morphing the blade istested on a static airfoil case instead, where it is shown that stall is alleviated by morphingthe blade trailing would like to thank my supervisor Dr.

4 Marius Paraschivoiu for giving me the opportunityto work on this thesis project, and for providing invaluable guidance and feedback. I couldnot have done as much without the support of my supervisor. I would like to extend mygratitude to Matin Komeili and Gabriel Naccache for their suggestions and counsel especiallyduring the initial phases of working on the thesis topic. I would also like to thank my col-leagues Spencer Foley, Dan McLean, Patrick Larin, Farbod Vakilimoghaddam, and AierkenDilimulati for all the insightful discussions and discourses. I would also like to acknowledgeDr. Daniel Inman and Dr. Alexander Pankonien of University of Michigan for providingthe Synergistic Smart Morphing Aileron blade profiles used for the study. I want to thankthe exam committee members Dr. Brian Vermeire and Dr. Samuel Li. Finally, I would liketo dedicate my thesis to my parents Rolando and Sylvia Tan, who have been patient withme all their life and supported me through thick and thin.

5 My thanks also to my brothersAlexander, Randolph, Lawrence, and Reginald for all the love and the computations for the study were made possible through the supercomputer Briar eefrom l Universit e de Montr eal, managed by Calcul Qu ebec and Compute Canada. Theoperation of this supercomputer is funded by the Canada Foundation for Innovation (CFI),the minist`ere de l Economie, de la science et de l innovation du Qu ebec (MESI) and theFonds de recherche du Qu ebec - Nature et technologies (FRQ-NT).ivContents1 Morphing Blade for Vertical axis wind Turbines .. = + Blade Profile (almost symmetric blade) .. = Blade Profile (cambered blade) .. = + Blade Profile (inverted-camber blade) .. Problem Statment and Objective .. Outline of the Study ..52 Theory and Literature Airfoil Static Stall .. Dynamic Stall in VAWT.

6 Wake and Blade-Vortex Interaction .. Effect of Blade Camber and Pitch .. Deforming Mesh Methods .. Spring Analogy .. Elasticity .. Diffusion .. Interpolation .. Basis Functions .. of Deforming Mesh Methods ..143 Models and Governing Equations .. Turbulence Model .. Numerical Setup .. Discretization .. at Cell Faces .. Coupling .. Discretization .. Calculation of Forces .. Grid Generation, Initial and Boundary Conditions .. Simulation of Moving Grids .. Equations for Dynamic Mesh .. Mesh and Non-conformal Cells .. Mesh Methods .. Function ..284 Verification and Grid and Time Step Sensitivity Analysis .. Grid Resolution at Boundary Layer .. Validation with Experiment .. Choice of Temporal Discretization .. Mesh Deformation Quality ..385 Results and Airfoil Static Stall Angle Investigation.

7 VAWT Fixed Profile Results .. Morphing Trailing Edge at Static Stall Angle .. Challenges of Morphing Case for VAWT .. Morphing Blade for VAWT .. Strategies for Morphing Blade on VAWT .. Outside of Fluent ..606 Conclusion62A Fourier Approximation of Fourier approximation for the airfoil surfaces .. 21 Frames of SSMA actuation range ..72B User-Defined Function80viList of Synergistic Smart Morphing Aileron (SSMA) [52] .. The trailing edge of the three blade profiles considered for the study .. Deflection angle and shift inCLcurve [3] .. Range of in one cycle for various plotted against the azimuthal DynamicCL(left) andCD(right) plotted against for 2< <5 [76] .. Computed vortex trajectory downstream [2] .. Domain geometry and boundary conditions .. (a) Rotating zone, (b) sliding mesh, (c) mesh resolution on trailing edge.

8 Boundary conditions for the static airfoil cases .. Sliding mesh and non-conformal interfaces [27] .. Blade surface split into upper, lower, and tip for specifying coordinates .. Algorithm diagram for specifying node movement for blade flexure motion . Grid sensitivity withCPas objective variable .. Temporal sensitivity withCPas objective variable .. Turbulent viscosity ratio near the wall .. Validation of experimental case for = 2 with non-dimensional tangential force Validation of experimental case for = 2 with non-dimensional normal for = + .. Turbulent viscosity ratio (a) 2nd order (b) 1st order temporal for = + (a) Initial mesh, (b) = + , and (c) = after defromation .. Orthogonality of the grids before (left) and after deformation (middle, right) Skewness of the grids before (left) and after deformation (middle, right).

9 Static airfoil = + convergence history, = 10 (left), = 20 (right) . angle of attack for the static airfoils .. Pressure contour [Pa] for the static airfoils .. (a)CL, (b)CDfor the three blade profiles for = .. Pressure contours [Pa] for = 120 (left column) and = 300 (right column) Vorticity contours for = 120 (left column) and = 300 (right column) .. Coefficient of powerCPat = for each fixed blade profiles .. Coefficient of powerCPat = of baseleine profile and envelope .. = + morphed to = for = 18 (left), Morphing phase (right) Comparison ofCL,CDvalues between = morphed and = Static pressure [Pa] while Morphing the blade from = + to = Streamlines on the profile before and after Morphing .. (a)CLvs effectiveaoaeff(b)aoaeffvs from fixed profile results .. for baseline profile, envelope, and Morphing profile.

10 Turbulent viscosity ratio for the Morphing case on VAWT .. Convergence history four cycles after Morphing to = + .. between morphed once and fixed profile of = + .. Vorticity magnitude contours for (a) Morphing case, (b) baseline fixed Declaring C-mesh fluid zone as deforming in Fluent dynamic mesh zones . Diagram of the alternate method I for VAWT Morphing case .. Diagram of the alternate method II for VAWT Morphing case .. Upper Fourier coefficients for the 21 frames of actuation range .. Lower Fourier coefficients for the 21 frames of actuation range ..72viiiList of Summary of the three blade profile characteristics .. Comparison of common mesh deformation methods .. Geometry and inlet conditions .. Summary of grid and time step sensitivity analysis .. AverageCPper cycle for 1st order and 2nd order temporal discretization.