Helical Blade Vertical Axis Wind Turbine (Small Scale), ANSYS Fluent Training
In the present problem, we are simulating a small-scale VAWT with helical blades.
This product includes a Mesh file and a comprehensive Training Movie.
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Introduction (Helical Blade Vertical Axis Wind Turbine (Small Scale))
With increasing environmental concerns, research into environmentally friendly renewable energy sources has increased. The focus on these resources is due to the increasing pollution (chemical and thermal pollution), increasing global energy demand, and decreasing fossil energy reserves. Renewable energy includes solar, biomass, geothermal, hydropower, and wind. Wind energy is one of these energies that has presented various choices to researchers. This energy currently has the fastest growth rate among other renewable sources. The devices used to generate wind energy are called wind turbines. A wind turbine is a device that converts the kinetic energy of the wind current into the rotational energy of the rotor shaft. These turbines include two main groups of the horizontal axis and the vertical axis. Vertical axis turbines were the first means of obtaining wind energy.
Types of vertical axis wind turbines include Darius, Savonius, Zephyr, and Sistan windmills.
We are simulating a wind turbine with dimensions of 10 x 20 cm with an average diameter of 7 cm in the present problem. This simulation was performed at wind speeds of 2 m / s and speeds of 60-40-80-100-120 rpm, and torque was reported as output. Small scale wind turbines can be used in places such as subways and tunnels, and spaces where there is a lot of wind production, but the dimensions of the environment are limited. To determine the generator for wind turbines, they should be tested at different speeds. This process is related to different TSRs (Tip Speed Ratio):
Helical Blade VAWT Geometry & Mesh
First, we draw the geometry of the turbine in SOLIDWORKS and prepare the geometry for meshing in Design Modeler software. Then, we import the geometry file in the ANSYS Meshing software.
At first, we use tetrahedral elements and then applying Fluent Mesh to convert it to polyhedral with fewer cells and better quality.
Different types of three-dimensional elements that we use in these mesh are tetrahedra and polyhedral, shown in the figures above.
Turbine modeling is performed in two zones of rotating and fixed.
The rotational computational domain must rotate around the blade axis using the Mesh Motion method to model the helical blade. Due to the greater importance of the turbine in the problem results, it is preferable to mesh the rotational zone around the blades with finer elements. The cylindrical rotational computational domain around the turbine helical blade with a diameter of 1.12 is considered. The meshing is done more accurately in this domain. The rotational domain is separated using interface surfaces that transfer values between the two domains.
The element number is equal to 2457591 tetrahedral or 507457 polyhedral.
VAWT CFD Simulation
This simulation was performed with the Pressure-Based and Transient solver.
A summary of the models and boundary conditions of the problem can be seen in the table below.
|Near wall treatment||Standard wall function|
|Cell zone conditions|
|Fluid-r||Rotation zone axis Z||40-60-80-100-120 rpm|
|velocity magnitude||2 m/s|
|Pressure outlet||0 pa|
|stationary wall motion||Cylinder-s|
|Rotary wall motion||Cylinder-r|
|momentum||first order upwind|
|turbulent kinetic energy||first order upwind|
|specific dissipation rate||first order upwind|
|gradient||Least squares cell base|
|gauge pressure||0 pa|
In this simulation, the wind turbine model was investigated in terms of the flow rate of 2 m / s at different rotational speeds.
This model investigates how much torque power the turbine can transfer to the generator as output. These results show that at 80 rpm, this turbine can transmit the most torque. However, if we do this test with the TSR criterion, this turbine has the highest torque at TSR = 0.46. Therefore, to design this turbine, the angles of attack and profiles must be designed so that the wind turbine can be close to the distance at TSR = 0.46.
In the next step, the performance of this turbine can be examined in different operating points according to TSR, for example, at a constant rotational speed of different flow velocities. In this way, it is possible to identify the working points with the maximum performance for the turbine, which is the maximum torque.
There are a Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.