Master of Science Thesis Particle System Modelling and Dynamic Simulation of a Tethered Rigid Wing Kite for Power Generation Mustafa Can Karadayı September 21, 2016 Faculty of Aerospace Engineering Delft University of Technology · Particle System Modelling and Dynamic Simulation of a Tethered Rigid Wing Kite for Power Generation Master of Science Thesis For obtaining the degree of Master of Science in Aerospace Engineering at Delft University of Technology Mustafa Can Karadayı September 21, 2016 Thesis Registration Number: 088#16#MT#FPP An electronic version of this thesis is available at http://repository.tudelft.nl Faculty of Aerospace Engineering Delft University of Technology · Copyright c Mustafa Can Karadayı All rights reserved. Delft University Of Technology Department Of Flight Performance and Propulsion The undersigned hereby certify that they have read and recommend to the Faculty of Aerospace Engineering for acceptance a thesis entitled \Particle System Modelling and Dynamic Simulation of a Tethered Rigid Wing Kite for Power Gener- ation" by Mustafa Can Karadayı in partial fulfillment of the requirements for the degree of Master of Science. Dated: September 21, 2016 Chairperson of Committee: Dr.-Ing. Roland Schmehl Reader: Dr. Axelle C. Vir´e Reader: Dr.ir. Mark Voskuijl Daily Supervisor: Uwe Fechner, MSc Abstract Kite Power research group at TU Delft developed the KiteSim framework for dynamic simulation of crosswind kite power systems. Currently, KiteSim has the capability to simulate leading edge inflatable kites. The use of rigid wing kites in crosswind kite power systems is becoming widespread. Accordingly, KiteSim framework is planned to be augmented to simulate the rigid wing kite power systems as well. Therefore, objective of this thesis is set to enhance the KiteSim framework in order to include the capability of the dynamic simulation of a rigid wing pumping crosswind kite power system by developing a particle system model to represent the tethered rigid wing. The particle system model of rigid wing consists of 6 point masses and 13 spring-damper elements. Positions and masses of the discrete particles are calculated in order to represent the rigid wing properties accurately. The spring-damper elements are interconnecting the particles. Lifting line theory and Kirke's post stall correlation methods are used to create the full angle of attack aerodynamic model for wings and tails. Available atmospheric, tether and winch models of the KiteSim framework are also used for rigid wing dynamic simulations. Equation of the motion of the particle system model is formulated as an implicit problem, which is simulated by implicit Runge-Kutta method of fifth-order. Validation simulations are conducted with the particle system model of NASA SGS 1-36 flight test sailplane. Validation cases show satisfactory results with the flight test data. For the remaining simulations, AP2 PowerPlane of Ampyx Power is modelled as particle system and manually flown in KiteSim. Mass properties of the model is found to be highly accurate throughout the simulations. Power generation capabilities of the model is checked by flying figure-of-eight trajectories. Reel-out phases are investigated, a peak mechanical power of 45 kW and a mean power of 10 kW are obtained. Further comparison of the reel-out dynamic simulations with the quasi-steady theoretical calculations is done. Moreover, gliding and stalling manoeuvres are simulated for a plausibility check study. The developed particle system model for rigid wings shows satisfactory results and a potential for further development. v vi Abstract Acknowledgements My enthusiasm for airborne wind energy was born when I started taking kite power lectures back in 2013 from Dr.-Ing. Roland Schmehl. I want to thank him for introducing me to this fascinating topic and leading me to choose this thesis project. I would like to thank my daily supervisor Uwe Fechner, MSc. who has been always ready to help me with my countless questions. I want to thank Ampyx Power for sharing the data of their previous prototype with me. I am also thankful to Ted Spinders for the help and feedback on piloting the simulation. I am grateful to all past and present members of Kite Power team and Room 6:08 who have been great mates not only in office but also outside. Thank you Tassos, Lukas, Jo, Felix, Chris, Pietro, Lorenzo, Julius, Mike, Apurva, Rachel, Andres, Bas, Viktor, Pranav. I want to thank my friends from FPP; Ashwin, Phillip, Martin, Akshay, Malcom and Roderick for being such a great company. In particular, I feel so happy to meet my companion Dino; our endless talks from science to politics shall never end. Thanks to all Happy Hour People, for sharing the life in Delft since the first day. Special thanks to the great panpas of G¨ulizAbla who became my family in Delft: Sercan, for pre-/peri-/post-fitness adventures; Emre, for interesting topics on the mops; Yasemin, for great midnight dessert sessions; Argun, for good coffee and hazelnut taste; Onursal, for interesting philosophical conversations and even more interesting laptop wars; Alper, for random tricky dj skills; Cansın, for tasty sushi workshops; Burak, for famous one- hand-capable-water-skiing tricks; Ekin, for overnights and broodjes memories; Tilbe, for hilarious countryside trips; and Cansel, for good cheer and 'But, I!' moments. Last but not the least, I am sending my greatest thanks to my parents for their trust and support during my whole life. Delft, The Netherlands Mustafa Can Karadayı September 21, 2016 vii viii Acknowledgements Contents Abstract v Acknowledgements vii List of Figures xv List of Tables xvii Nomenclature xix 1 Introduction1 2 Crosswind Kite Power Fundamentals3 2.1 Physics of Crosswind Kite Power Systems..................3 2.1.1 Power formula.............................3 2.1.2 Power harvesting factor........................4 2.2 Classification of Crosswind Kite Power Systems...............4 2.2.1 Power extraction mode classification.................4 2.2.2 Flexible wing vs. rigid wing classification..............5 2.2.3 Other classifications..........................6 2.3 Working Principles of Crosswind Kite Power Systems............6 3 Literature Review9 3.1 Modelling and Simulation...........................9 3.2 Crosswind Kite Modelling........................... 10 3.3 TU Delft Dynamic Kite Power System Simulator.............. 12 3.3.1 Atmospheric model........................... 12 3.3.2 Tether model.............................. 13 3.3.3 Kite models............................... 13 ix x Contents 3.3.4 Winch model.............................. 14 3.3.5 Implementation............................. 14 3.4 Particle System Modelling........................... 15 3.5 Component Buildup Method......................... 16 3.6 Aerodynamic Models for Dynamic Simulation................ 18 4 Research Objective 21 5 Methodology of the Simulation Modelling 23 5.1 Rigid Wing Particle System Model Structure................ 23 5.1.1 Discretization of the particles..................... 24 5.1.2 Formation of the spring-damper elements.............. 29 5.2 Rigid Wing Aerodynamic Model....................... 29 5.2.1 XFLR5 software............................ 31 5.2.2 Post-stall correlation method..................... 32 5.2.3 Aerodynamic data approximation script............... 34 5.3 Rigid Wing Controller Implementation.................... 34 5.4 Atmospheric Model............................... 35 5.5 Tether Particle System Model......................... 36 5.6 Rigid Wing Particle System Model...................... 39 5.6.1 Calculation of the gravitational forces................ 40 5.6.2 Calculation of the spring-damper forces............... 40 5.6.3 Calculation of the aerodynamic forces................ 41 5.7 Equation of Motion of the Particle System Model.............. 46 5.8 Formulation of the Implicit Problem..................... 46 5.9 Simulation Implementation.......................... 47 5.9.1 Numeric solver............................. 47 5.9.2 Initial and simulation parameters................... 48 6 Model Validation 49 6.1 Validation Aircraft............................... 50 6.2 Validation Methodology............................ 50 6.2.1 Simulation of non-tethered flight in KiteSim............. 50 6.2.2 Fuselage drag estimation........................ 50 6.3 Validation Results and Discussions...................... 51 Contents xi 7 Simulation Results and Discussions 57 7.1 Mass Properties Results............................ 57 7.1.1 Case 1: Tethered, non-maneuvering kite at very high atmospheric wind speed............................... 57 7.1.2 Case 2: Tethered, maneuvering kite at high atmospheric wind speed 60 7.2 Reel-Out Phase Results............................ 63 7.2.1 Case 3: Tethered, reel-out, figure-of-eight trajectory flight at strong wind................................... 63 7.2.2 Case 4: Tethered, reel-out, figure-of-eight trajectory flight at mod- erate wind................................ 67 7.2.3 Comparison of reel-out cases results and theoretical analysis.... 70 7.3 Plausibility Checking Results......................... 71 7.3.1 Case 5: Non-tethered, gliding flight.................. 71 7.3.2 Case 6: Non-tethered, stalling maneuver............... 73 7.4 Discussions................................... 75 7.4.1 Discussion on the developed particle system model......... 75 7.4.2 Discussion on the controlling and piloting.............. 76 7.4.3 Discussion on the mass properties.................. 76 7.4.4 Discussion on the power generation.................