The Airborne Wind Turbine (AWT) revolutionizes wind energy generation by taking advantage of high-altitude winds. AWT turbines are connected to the ground or a platform, unlike ground-based turbines. This higher elevation allows stronger, more constant winds, improving energy capture. Lightweight, aerodynamic turbines generate power by rotating their blades in the wind. The AWT’s mobility and ability to reach heights exceeding conventional turbines make it potential for renewable energy capacity.

In the present project, Airborne Wind Turbine is simulated via ANSYS Fluent solver using a Multi-reference Frame (MRF) module. This study gets credit from the reference paper entitled “Aerodynamic analysis of an airborne wind turbine with three different aerofoil-based buoyant shells using steady RANS simulations”.

• Reference [1]: Saleem, Arslan, and Man-Hoe Kim. “Aerodynamic analysis of an airborne wind turbine with three different aerofoil-based buoyant shells using steady RANS simulations.” Energy Conversion and Management177 (2018): 233-248.

Figure 1: Schematic of the wind turbine rotor profile [1]

Simulation Process

The geometry consists of three initial zones. One zone is dedicated to the blade and surrounding that rotates and the other represents the environment. Plus, there is another zone designed to be used later in the meshing step and guide the focus of elements behind the airborne. This step can effectively help us optimize the number of cells and prevent an unrestrained increase in the number of cells. Still, we need 13739868 tetrahedron elements. Check the figures below to see how meticulously they are generated.

Unlike vertical axis wind turbines, horizontal axis wind turbines or blades implemented parallel to the airflow has constant angle of attack during the movement. So there would be no need to perform an unsteady simulation. Utilizing Multi-reference frame (MRF) module facilitates us to apply rotating motion to the rotor with minimum computational costs. It is rotating with 190 rpm.

Figure 2: Discretization of computational domain

Post-processing

The CFD study of the Airborne Wind Turbine (AWT) working at 190 rpm shows interesting aerodynamic features through the distributions of velocity and pressure. The velocity lines show a top flow speed of 56.4 m/s, and there is a clear wake formation behind the turbine that goes several rotor diameters away. Using the Multi-Reference Frame (MRF) method to model the rotational effects is a good way to see how the shape of the blades causes pressure differences that are necessary for torque production. The velocity field shows the predicted acceleration around the blade tips and a velocity deficit in the wake region. This shows that the momentum is being extracted from the free stream flow efficiently.

Figure 3: Velocity pattern and streamlines around airborne wind turbine

With pressure changes across the turbine structure operating from -591 Pa to 90.9 Pa, the pressure contours show important details about the aerodynamic loading. At the leading edge of the blades, high-pressure areas form, and on the suction side, low-pressure areas form. This creates the lift that is needed to make electricity. The pattern of pressure differences suggests the best blade design for operation at high altitudes. The gliding shell configuration seems to keep the structure strong while improving aerodynamic performance. The computer results, which were checked against the reference study by Saleem and Kim (2018), show that this new idea for using high-altitude wind resources could work.

Figure 4: Pressure field around airborne wind turbine