Effect of Chordwise Struts and Misaligned Flow on the Aerodynamic Performance of a Leading-Edge Inflatable Wing

Axelle Viré,Roland Schmehl,Geert Lebesque,Mikko Folkersma

doi:10.3390/en15041450

Abstract

Leading-edge inflatable (LEI) kites use a pressurized tubular frame to structurally support a single skin membrane canopy. The presence of the tubes on the pressure side of the wing leads to characteristic flow phenomena for this type of kite. In this paper, we present steady-state Reynolds-Averaged Navier-Stokes (RANS) simulations for a LEI wing for airborne wind energy applications. Expanding on previous work where only the leading-edge tube was considered, eight additional strut tubes that support the wing canopy are now included. The shape of the wing is considered to be constant. The influence of the strut tubes on the aerodynamic performance of the wing and the local flow field is assessed, considering flow configurations with and without side-slip. The simulations show that the aerodynamic performance of the wing decreases with increasing side-slip component of the inflow. On the other hand, the chordwise struts have little influence on the integral lift and drag of the wing, irrespective of the side-slip component. The overall flow characteristics are in good agreement with previous studies. In particular, it is confirmed that at a low Reynolds number of Re=105, a laminar separation bubble exists on the suction side of this hypothetical rigid wing shape with perfectly smooth surface. The destruction of this bubble at low angles of attack impacts negatively on the aerodynamic performance.

Highlights

Wind energy will be a key enabler for the global energy transition in the years to come [1,2]
The computational study investigated the effect of chordwise strut tubes and inflow with a side-slip component on the flow around a leading-edge inflatable wing for airborne wind energy applications
The results show that the struts have little influence on the overall aerodynamic performance of the wing, independent of the degree of side-slip

Summary

Introduction

Wind energy will be a key enabler for the global energy transition in the years to come [1,2]. To meet the climate goals that many nations have set, wind power will have to grow at an unprecedented rate and will need to be harnessed at new locations. This drives the development of new concepts that are low cost, resource efficient, and fast to deploy and that have a low environmental impact. The wing is operated in pumping cycles, alternating between tether reel-out and reel-in phases. For a leading-edge inflatable (LEI) wing flying figure-of-eight crosswind manoeuvres, typical variations of the angle of attack are 6◦ ≤ α ≤ 16◦ during the reel-out phases and −8◦ ≤ α ≤ 4◦ during the reel-in phases [4,5]. For an accurate prediction of the power output, it is important to know the aerodynamic performance of the wing over the entire operation cycle

Objectives

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Conclusion