Aero-servo simulations of an airborne wind energy system using geometry-resolved computational fluid dynamics

Abstract

Airborne wind energy (AWE) is an innovative and promising technology for harnessing wind energy, often achieved through the use of tethered aircraft flying in crosswind patterns. A comprehensive understanding of the unsteady interactions between the wind and the aircraft is required for developing efficient, reliable, and safe AWE systems. High-fidelity simulation tools are essential for accurately predicting these interactions. To provide meaningful insights into crosswind flight maneuvers, they should incorporate the coupled nature of aerodynamics, dynamics, and control systems. Moreover, local aerodynamic phenomena, such as flow separation, play a significant role in the overall performance of the system and must be represented accurately. Capturing these phenomena requires resolving the complete geometry of the aircraft. Therefore, this work presents a geometry-resolved computational fluid dynamics framework of an AWE system, encompassing all lifting surfaces and integrating movable control surfaces, referred to as the virtual wind environment (VWE). Unlike existing models that only consider linear combinations of individual aerodynamic effects, the VWE addresses the challenge of combining the relevant aerodynamic interactions specific to crosswind flight motion. This VWE is coupled to the dynamics and control framework of an AWE system, enabling geometry-resolved aero-servo simulations. We demonstrate the novel simulation framework by tracking a pre-optimized one-loop power cycle in the VWE coupled to model predictive control, achieving 96 % of the reference power.