Numerical analysis of the flow past a leading edge inflatable kite wing using a correlation-based transition model

Numerical analysis of the flow past a leading edge inflatable kite wing using a correlation-based transition model

Demkowicz, Patryk (TU Delft Aerospace Engineering)

Viré, Axelle (mentor)
Schmehl, Roland (graduation committee)
van Zuijlen, Alexander (graduation committee)
Folkersma, Mikko (graduation committee)

Delft University of Technology

Aerospace Engineering

2019-12-19

Thorough understanding of flexible wing structural and aerodynamic properties is crucial to reduce uncertainties in the design process of energy generating kite systems. A flexible leading edge inflatable (LEI) tethered kite connected to a drum-generator module is currently being developed by the Airborne Wind Energy research group at TU Delft jointly with its commercial spin-off Kitepower. During each energy generation cycle, the kite experiences persistent regions of flow separation, which combined with the bowed shape of the kite and its low aspect ratio cause multiple 3D flow phenomena. Furthermore, a kite is a lightweight and flexible structure and there exists very strong coupling between the aerodynamic loads and its structural dynamics, forming an intricate aeroelastic problem.

Due to computational limitations of today's hardware, it is difficult and expensive to numerically solve the coupled aeroelastic problem in detail. As such, the focus of this thesis is to resolve and characterise one side of the problem, which is the LEI kite aerodynamics. Kitepower LEI V3A kite, modelled as a rigid geometry, has been analysed for various Reynolds numbers and angles of attack using a steady-state Computational Fluid Dynamics solver. A high quality, hybrid mesh has been generated. The gamma-Rethetat transition model has been used to improve the accuracy of the results at low Reynolds numbers and to assess the significance of transition at high Reynolds numbers.

Obtained force coefficients for a range of angles of attack are in general agreement with the values used in existing numerical models and measurements from experiments. The results indicate that flow transition is important to take into account for Reynolds numbers at least up to 3 million in order to accurately predict the stall angle. Large amounts of cross flow have been observed over the span of the kite that may affect the integral drag coefficient. The employed methodology is only applicable to the traction phase of the pumping cycle, as the steady-state and rigid geometry assumptions do not hold during the retraction phase, where the kite experiences severe deformation.

RANS
transition modelling
kite

http://resolver.tudelft.nl/uuid:c53aa605-1b2e-47a7-b991-c1917d7463b4

Student theses

master thesis

© 2019 Patryk Demkowicz