High Fidelity Aeroelastic Analysis of a Membrane Wing

Julia Steiner MSc Student Delft University of Technology Faculty of Aerospace Engineering

Wind Energy Research Group

Kluyerweg 1 2629 HS Delft

Netherlands

julia.steiner@alumni.ethz.ch kitepower.tudelft.nl

High Fidelity Aeroelastic Analysis of a Membrane Wing

Faculty of Aerospace Engineering, Delft University of Technology

Through aeroelastic modeling of membrane wings such as Leading Edge Inflatable (LEI) tube kites used in Air-borne Wind applications, one can gain a better under-standing of processes relevant for flight stability and per-formance optimization. The aim of this project is to estab-lish a baseline for a partitioned aeroelastic solver suitable for membrane wings at high Reynolds numbers by cou-pling high fidelity structure and fluid models.

An in-house implementation of a dynamic, nonlinear Fi-nite Element structural solver employing shell elements is used to model the canopy of the membrane wing [1]. As a first step, an unsteady lumped vortex particle method is used for the fluid model. Eventually the transient Navier-Stokes Finite Element solver Fluidity [2] is used to model the highly nonlinear flow around the membrane wing at high angles of attack present in crosswind flight of the kite.

Validation data setup [4]

The quantitative validation of the solver is initially done on the classical Fluid-Structure Benchmark case as pro-posed by Turek et al. [3]. Subsequently, a qualitative ver-ification on the test case of Greenhalgh [4] as pictured on the left is carried out as well. While limitations in the ex-periment description make quantitative verification for this test case difficult, qualitative verification for steady inflow conditions at different angles of attack and hys-teresis effects around an angle of attack close to zero are still possible.

While the benchmark cases of this project deliver proof of concept of the applied methodology, they are of little practical relevance. Nevertheless, in future projects the solver can be extended to include three-dimensional ef-fects, a more realistic wing design and unsteady bound-ary conditions.

References:

[1] Bosch, A. et al: Dynamic Nonlinear Aeroelastic Model of a Kite for Power Generation. Journal of guidance, control and dynamic 37(5), 1426-1436 (2014)

[2] Krishnan, N. et al: An Immersed Boundary Method using Finite Element Methods. Computer Methods in Applied Mechanics and En-gineering (2017). Draft version.

[3] Turek, S. et al: Numerical Benchmarking of Fluid-Structure In-teraction: A comparison of different discretization and solution ap-proaches.

[4] Greenhalgh, S. et al: Aerodynamic Properties of a Two-Dimensional Inextensible Flexible Airfoil. AIAA Journal 22(7), 865-870, (1984)