Quasi-steady fluid structure interaction model of the surf kite

M Prabu Sai Manoj 4th Year Undergraduate Department of Aerospace Engineering Indian Institute of Technology Madras

Chennai 600036 India

manoj.adurs@gmail.com http://www.ae.iitm.ac.in

Quasi-Steady Fluid Structure Interaction Model of the Surf Kite

1_{Department of Engineering Design, Indian Institute of Technology Madras} 2_{Department of Aerospace Engineering, Indian Institute of Technology Madras}

Airborne wind energy is a new and promising class of wind energy systems. The core concept of the traditional wind mills was born ages ago and is still a rigid design compared to this new class of wind energy extraction de-vices. In the present study, we have used a kite based air-borne wind energy system in which kites are employed to extract energy from the air and supply this mechan-ical energy into ground generator for further use. Our main focus in this study is to develop a reduced computa-tional model to investigate the parametric space in order to maximize the extracted force values.

In this study, Fluid-Structure Interaction (FSI) model of the Kite North Rhino [1] is developed. Airfoil cross sec-tions of the kite with various geometrical factor like cam-ber and thickness as well as for different angle of attacks are solved for aerodynamic coefficients using commer-cial solver ANSYS-FLUENT. With this results, a fit function is estimated in terms of above variables. A 3D potential flow based solver along with above 2D results is used to calculate the aerodynamic loads [2]. This is implemented in an open source Matlab toolbox called Tornado [3]. Tornado uses an extended version of the potential flow 3D vortex lattice method and has been written by Prof. Tomas Melin from KTH, Sweden. The structural model-ing is done usmodel-ing the commercial solver ABAQUS (Solver-FEA) with a finite element analysis ((Solver-FEA). The CAD model

of the kite is developed in SolidWorks and imported to ABAQUS. For FEA, three dimensional two node beam ele-ments are used to model inflatable leading edges, struts, tips and trailing edges and three node triangular shell el-ements are used to model canopy structure of the kite. A mesh convergence study of the model has also been performed. A coupled FSI solver is developed integrating these two in a loosely coupled scheme [1]. The aerody-namic loads are updated on the structural nodes in the coupled solver at each time which we call as a quasi-FSI model. For a given wind speed, angle of attack, camber and thickness values, the aerodynamic loads that are cal-culated from the aerodynamic model are transferred to fi-nite element model and the information of the deformed geometry is obtained from the FEA. This information is fed into MATLAB algorithm for the set of loads to run the next iteration. This process is repeated till convergence. This quasi FSI model is used to investigate the system’s parametric space in order to optimize the total force ex-tracted.

References:

[1] Bosch H. A.:Finite element analysis of a kite for power genera-tion. MSc Thesis, TU Delft, The Netherlands (2012)

[2] Breukels, J.: An Engineering Methodology for Kite Design. PhD Thesis, TU Delft, The Netherlands (2011)

[3] Tomas, M.: Tornado vortex lattice method (2008). http://www.redhammer.se/tornado