Aerodynamic analysis of an airborne wind turbine with three different aerofoil-based buoyant shells using steady RANS simulations

The manuscript investigates aerodynamic performance of an airborne wind turbine with varying shell configurations in an effort to elaborate the influence of shell aerodynamics on the performance of the buoyant airborne wind turbine for operating conditions at an altitude of 400 m above the sea level. A systematic study has been conducted on the three airborne duct shapes based on the NACA-5415, NACA-9415 and NACA-5425 cambered aerofoils by considering NREL Phase IV rotor and constant airborne shell throat diameter of 4.02 m. Three dimensional steady state simulations have been performed by employing k-ω SST turbulence model for a range of wind speeds10-25 m/s at zero angle of attack (the angle between wind direction and turbine rotational axis). The performance of the studied turbines have been analysed in terms of rotor thrust coefficient, duct thrust coefficient, turbine power coefficient, swallowed mass flow rate and pressure distribution along the shell. Results demonstrate that among all the considered shell configurations, the NACA-9415 shell based turbine demonstrated highest power coefficient. Increment in the both, aerofoil camber (5-9% of chord length) and thickness (15-25% of the chord length) resulted in 2.05 and 1.45 times higher turbine power coefficient respectively in comparison to the reference aerofoil (NACA-5415) shell based turbine.