Vertical Axis Wind Turbine (VAWT), Paper Numerical Validation by ANSYS Fluent Training
- The problem numerically simulates Vertical Axis Wind Turbine (VAWT) using ANSYS Fluent software.
- This project is validated with a reference article.
- We design the 3-D model by the Design Modeler software.
- We mesh the model with ANSYS Meshing software, and the element number equals 1650940.
- We perform this simulation as unsteady (Transient).
- We use the Mesh Motion method to define rotational motion.
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The present problem simulates the airflow passing over a Vertical Axis Wind Turbine (VAWT) by ANSYS Fluent software. We perform this CFD project and investigate it by CFD analysis.
The simulation is based on a reference paper, “Wind tunnel and numerical study of a small vertical axis wind turbine.” Its results are compared and validated with the results in the article.
The present model is designed in two dimensions using Design Modeler software. The generated model consists of a rectangular domain in which the rotating domain is placed.
The meshing of the model has been done using ANSYS Meshing software. The mesh type used for this geometry is structured, and the element number is 1650940.
Also, the transient solver has been enabled due to the mesh motion option enabled.
In this project, the Darrius wind turbine, a type of vertical axis wind turbine (VAWT), is simulated. The turbine consists of several curved airfoil blades mounted on a rotating shaft or framework.
In this type of turbine, the main rotor is positioned vertically and can be installed near the ground. The airflow enters the computational domain with a velocity of 5.07m/s, and the RNG k-epsilon model is exploited to solve the turbulent flow equations, as the paper stated.
Also, it should be noted that the Mesh Motion option was enabled to simulate the rotating motion of turbine blades. The turbine blades rotate at 42.25rad/s.
At the end of this simulation, we compared the present work results and validated them with the results obtained by the paper. For this purpose, we use the diagram in figure 14, which shows the Torque coefficient changes over time for each rotor blade.
The present work is done considering a three-blade turbine model, and the TSR value is considered equal to 2.5; The open-air velocity is equal to 5.07 m/s, the length of the blades or the radius of the turbine is equal to 0.3 m, and also the value of the rotational speed of the blades is equal to 42.25 rad/s.
In pressure contours, due to constant variation of the blades’ position and their angle of attack, the blades’ pressure continually changes. These constant pressure changes bring up one of the significant challenges of VAWTs, which would be the dynamic stall.
Also, due to pressure changes, the blades of a VAWT are fatigue-prone due to the wide variation in applied forces during each rotation.
We can overcome these challenges by using modern composite materials and improvements in design, including aerodynamic wingtips that cause the spreader wing connections to have a static load since the vertically oriented blades can twist and bend during each turn, causing them to break apart.
Another prominent factor regarding the rotation of VAWTs is the generation of tip vortexes on the blades’ top tip. The tip vortex’s strength is different based on each blade’s phase angle. The power of the tip vortex is a sign of lift force on each blade.
The stronger the tip vortex core, the stronger the lift force applied to the blade. This change in strength is due to the turbine rotor blade’s changing lift as it rotates through different phase angles.
We should note that there is likely to be a small delay between the maximum lift and the maximum strength of the tip vortex occurring. This will be due to the flow’s time to respond to the changing lift around the rotor blade.