Fluid-Structure Interaction of an Inflatable Kite Wing

Visualising the wing tip vortex of a ram-air kite suspended in a wind tunnel (TU Delft experiments at the University of Stuttgart, 2008).

Navaneetha Krishnan Rajan PhD Researcher Delft University of Technology Faculty of Aerospace Engineering

Wind Energy Section Kluyverweg 1 2629 HS Delft The Netherlands N.K.Rajan@tudelft.nl

www.lr.tudelft.nl

Fluid-Structure Interaction of an Inflatable Kite Wing

Faculty of Aerospace Engineering, Delft University of Technology Kite power is one of the promising concepts in Airborne

Wind Energy. The complex flight patterns, the unpre-dictable nature of cross-winds, and the highly flexible and inflatable design of the kite wing make the dynamics and control of the wing highly complex. Existing methods make use of approximated structural and fluid-dynamics models to predict this behaviour [1]. Also, most of the approximate solutions can only be used to simulate the wing under ideal conditions. Reliable simulation mod-els that can provide high fidelity results are imperative for further development of kite power systems.

A novel fluid-structure interaction (FSI) simulation tech-nique is being developed at the Kite Power group of TU Delft. The proposed method brings in Finite Element (FE) computing techniques for the precise structural and aerodynamic analysis of the airborne kite. The objective is to develop a non-linear dynamic FE structural solver coupled with a CFD tool that can allow for the complex dynamics of the highly flexible, inflated kite under a vari-ety of flight conditions.

The outputs of the FSI simulator will provide better in-sight into the kite dynamics. The framework can be uti-lized in the optimization of flight paths and in enhanc-ing kite performance. An FSI simulator can analyse the kite’s behaviour under extreme and non-ideal conditions.

It can be used to guarantee the kite’s stability during launching, reeling, steering, low-wind and under other adverse conditions where there are high chances for the kite to collapse. The system can be used to optimize exist-ing control algorithms which makes automation feasible. The project is at its inception and the methods are at the formulation stage. In the initial phase, a minimal tural solver with the capacity to resolve nonlinear struc-tural dynamics on 2D membrane elements will be cou-pled with an existing CFD code. Fluidity is an open-source CFD code that is being developed at the Applied Mod-elling and Computation Group (AMCG), Imperial College, London [2]. In-built routines for modern CFD techniques like mesh-adaptivity and immersed boundary methods, and hybrid parallelisation using OpenMP and MPI makes Fluidity an ideal choice for the problem at hand. The poster will list the objectives and delineate an initial out-line of the project. This research is supported by the Eu-ropean Commission under grant agreement PCIG13-GA-2013-618159.

References:

[1] Bosch A., Schmehl R., Tiso P., Rixen D.: Dynamic Nonlinear Aeroe-lastic Model of a Kite for Power Generation. Journal of Guidance, Control, and Dynamics, Vol. 37, No. 5, pp. 1426–1436 (2014) [2] Fluidity Manual: Applied Modelling & Computation Group. Im-perial College, London (2014)