Preprints
https://doi.org/10.5194/wes-2023-7
https://doi.org/10.5194/wes-2023-7
06 Apr 2023
 | 06 Apr 2023
Status: this preprint is currently under review for the journal WES.

Wake Characteristics of a Balloon Wind Turbine and Aerodynamic Analysis of its Balloon Using the LES-AD Model

Aref Ehteshami and Mostafa Varmazyar

Abstract. Wake characteristics and aerodynamics of a balloon wind turbine were numerically investigated for different wind scenarios. Large eddy simulation, along with the actuator disk model, was employed to predict the wake behavior of the turbine. To improve the accuracy of simulation results, a structured grid was generated and refined by using an algorithm to resolve about 80 % of the local turbulent kinetic energy in the wake. Results contribute to designing an optimized layout of wind farms and stability analysis of such systems. The capabilities of the hybrid ADM-LES model when using the mesh generation algorithm were evaluated against the experimental data on a smaller wind turbine. The assessment revealed a good agreement between numerical and experimental results. While a weakened rotor wake was observed at a distance of 22.5 diameters downstream of the balloon turbine, the balloon wake disappeared at about 0.6 of that distance in all wind scenarios. Vortices generated by the rotor and balloon started to being merged at a tilt angle of 10°, which intensifies the turbulence intensity at 10 diameters downstream of the turbine for wind speeds of 7 m s-1 and 10 m s-1. By increasing the tilt angle, the lift force on the wings experiences a sharper increase with respect to that of the whole balloon, which signifies a controlling system requirement for balancing such extra lift force.

Aref Ehteshami and Mostafa Varmazyar

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2023-7', Anonymous Referee #1, 16 May 2023
  • RC2: 'Comment on wes-2023-7', Joshua Brinkerhoff, 20 May 2023
  • RC3: 'Comment on wes-2023-7', Anonymous Referee #3, 20 May 2023

Aref Ehteshami and Mostafa Varmazyar

Aref Ehteshami and Mostafa Varmazyar

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Short summary
In this paper, we numerically studied the wake characteristics and aerodynamics of a balloon wind turbine, an airborne system operating at altitudes of about 400–1000. The system can benefit from a stronger and steady wind flow at these altitudes. Results contribute to the wake structure and the magnitude of aerodynamic loads on the balloon in varying wind conditions at high altitudes. Findings are valuable in designing future optimized wind farms and control systems for balloon wind turbines.