Helical Blade Vertical Axis Wind Turbine (Small Scale), 5 Different RPMs — ANSYS Fluent CFD Simulation

Description

This project simulates the airflow over a small-scale vertical axis wind turbine (VAWT) with helical blades using ANSYS Fluent. Wind energy has the fastest growth rate among renewable sources, and a wind turbine is a device that converts the kinetic energy of the wind into the rotational energy of the rotor shaft. Small-scale turbines like this one are well suited to environments such as subways and tunnels, where there is plenty of wind but limited space, and they must be tested across a range of rotational speeds — corresponding to different tip speed ratios (TSRs) — to select the right generator. This study evaluates the turbine at five different RPMs and reports the resulting torque.

Methodology

The model is designed in three dimensions in SOLIDWORKS and imported into Design Modeler, consisting of a helical-blade VAWT placed inside a rectangular domain. Meshing is first performed in ANSYS Meshing to generate a tetrahedral mesh, which is then converted in Fluent Meshing to a polyhedral mesh with fewer cells and better quality — 2,457,591 tetrahedral cells becoming 507,457 polyhedral cells. The transient solver is enabled. The turbine measures 10 × 20 cm with an average diameter of 7 cm, and the simulation is run at a wind velocity of 2 m/s across rotating speeds of 40, 60, 80, 100, and 120 rpm. To model the helical blade, a cylindrical rotational domain around the blade (sized at 1.12 diameters) is defined and rotated about the blade axis using the Mesh Motion method, meshed more finely to reflect its greater importance to the results. This rotational domain is separated from the stationary domain by interface surfaces that transfer values between the two, and the standard k-epsilon model solves the turbulent flow equations.

Analysis

At the end of the solution, 2D and 3D contours of pressure, velocity, and streamlines are obtained. The pressure contour shows a clear stagnation point on the frontal area of the helical blade, and a wake region forms behind the turbine due to flow separation. The torque delivered to the generator is calculated for each speed: the turbine transmits the most torque at 80 rpm, which corresponds to its peak torque at TSR = 0.46. This indicates that, to design the turbine well, the blade angles of attack and profiles should be tuned so that operation stays close to TSR = 0.46. As a next step, the turbine's performance can be examined at different operating points — for example, at a constant rotational speed with varying flow velocities — to identify the working points of maximum torque. By the end of this project, you'll be able to set up a transient Mesh Motion simulation of a helical-blade VAWT, run a comparative study across multiple RPMs, convert a tetrahedral mesh to polyhedral in Fluent Meshing, and interpret the pressure, velocity, and torque results to find the turbine's optimal tip speed ratio.