Multi-fidelity Fluid-Structure Interaction Analysis of a Membrane Blade Concept in non-rotating, uniform flow condition
Abstract. In order to study the aerodynamic performance of a semi-flexible membrane blade, Fluid-Structure Interaction simulations have been performed for a non-rotating blade under steady inflow condition. The studied concept blade has a length of about 5 m. It consists of a rigid mast at the leading edge, ribs along the blade, tensioned edge cables at the trailing edge and membranes forming upper and lower surface of the blade. Equilibrium shape of membrane structures in absence of external loading depends on the location of the supports and the pre-stresses in the membranes and the supporting edge cables. Form finding analysis is used to find the equilibrium shape. The exact form of a membrane structure at the service condition depends on the internal forces and also on the external loads which in turn depend on the actual shape. As a result, two-way coupled Fluid-Structure Interaction (FSI) analysis is necessary to study this class of structures. The fluid problem has been modeled using two different approaches which are the vortex panel method and the numerical solution of the Navier–Stokes equations. Nonlinear analysis of the structural problem is performed using the Finite Element Method. The goal of the current study is twofold: First, to make a comparison between the converged FSI results obtained from the two different methods to solve the fluid problem. This investigation is a prerequisite for the development of an efficient and accurate multi-fidelity simulation concept for different design stages of the flexible blade. The second goal is to study the aerodynamic performance of the membrane blade in terms of lift and drag coefficient as well as lift to drag ratio and to compare them with those of the equivalent conventional rigid blade. The blade configuration from the NASA-Ames Phase VI rotor is taken as the baseline rigid blade configuration. The studied membrane blade shows a higher lift curve slope and higher lift to drag ratio compared with the rigid blade.