Archimedes Screw Turbine (AST)

Archimedes Screw Turbine (AST), CFD Simulation, ANSYS Fluent Tutorial

Description

This project simulates an Archimedes Screw Turbine (AST) — also known as an Archimedes screw generator or screw turbine — consisting of 3 blades, using ANSYS Fluent. This hydraulic machine applies the principle of the Archimedean screw to convert the potential energy of upstream flow into kinetic energy.

The turbine is modeled as installed within a river, with water flowing through it via a fixed-level inlet positioned in an upper box of the domain. The turbine is set at a 30-degree angle relative to the ground, with water entering from the upper level. The outlet is defined with zero gauge pressure, while all remaining surfaces are treated as stationary walls.

The 3D geometry was designed in Design Modeler, featuring two rectangular boxes at the turbine's inlet and outlet ends that guide the flow into and out of the turbine. The turbine's interior and exterior radii measure 0.5 m and 1 m, respectively. The domain was meshed in ANSYS Meshing, generating over 2 million elements.

Methodology

The turbine's rotational motion is modeled using an unsteady Mesh Motion approach, with the rotating zone containing the screw turbine rotating independently within the domain.

The VOF model defines the water and air phases, with the domain's upper level maintaining a fixed water level via the Open Channel Flow boundary condition. Turbulence is resolved using the standard two-equation k-epsilon model.

Conclusion

Results include 2D and 3D contours and vector fields for water pressure and velocity. Water flow enters through the upper box, passes over the turbine blades, and exits through the outlet face.

Turbine output power was calculated by multiplying the moment obtained from ANSYS Fluent by the turbine's angular velocity (1.05 rad/s, corresponding to 10 rpm), yielding a maximum output of approximately 5 kW at this operating speed. The moment parameter's variation over the course of the solution is captured to illustrate this calculation.

Static pressure contours across the domain further show a clear pressure decrease as the flow passes through the channel, consistent with the expected energy extraction occurring as water moves through the turbine.