Archimedes Screw Turbine (AST), CFD Simulation with Ansys Fluent
In this project, an Archimedes Screw Turbine (AST) has been simulated and the results of this simulation have been investigated.
This product includes Geometry & Mesh file and a comprehensive Training Movie.
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Archimedes Screw Turbine Introduction
Archimedes Screw Generator, also known as Archimedes Screw Turbine (AST), or screw turbine, is a hydraulic machine that uses the principle of the Archimedean screw to convert the potential energy of flow on an upstream level into kinetic energy.
The Archimedean screw turbine is set on rivers with a relatively low head (from 0.1 m to 10 m) and low flows (0.01 m³/s up to around ten m³/s on one turbine). Due to the construction and slow motion of the turbine blades, the turbine is considered friendly to aquatic wildlife.
Water flows freely, and its weight acts on the curved blades of the turbine worm. Emerging rotational movement via a flexible coupling bolt transmitted to the gearbox continues into the generator. The asynchronous generators will ensure the transformation of the rotational kinetic energy into electrical energy, thereby fulfilling the purpose of the process equipment.
Screw Turbine Project Description
In this project, an Archimedes Screw Turbine consisting of 3 blades is simulated in two models. The first model is unsteady Frame Motion, and the second one is an unsteady Mesh Motion. Considering the conception of both methods, the turbine in the frame-motion method is in a stationary state, and the fluid around it is rotating, while in the Mesh Motion method, the rotating zone that contains the Screw Turbine rotates independently.
It’s assumed that the turbine is set on a river and water fluid flows through it. There is a vertical and horizontal plane named Inlet, and the Outlet Boundary Condition is a vertical plane at the upper level. The turbine has a 30-degree angle with the ground while water enters the domain with a uniform velocity of 0.5 m/s in each plane, gauge pressure in the outlet is zero, and all other faces are stationary walls. The angular velocity of the turbine is 40 rpm, and the two-equation k-Omega model simulates the turbulence in the flow.
Geometry & Mesh
The geometry of the solution is a 3D turbine that makes a 30-degree angle with the ground. There are two rectangular boxes at the turbine’s beginning and end, which guide the flow into the turbine and finally the water exit from it. The turbine’s interior and exterior radius is 0.5 m and 1 m, respectively.
Ansys meshing software is used to generate meshes of the solution. The elements are all in tetrahedral shape (Unstructured), and the number of them in the frame motion method is 793257, and in mesh motion method, more than 2 million elements are created:
Screw Turbine CFD Simulation:
We consider several assumptions to simulate the present model:
- We perform a pressure-based solver.
- Simulation has only examined fluid behavior; in other words, heat transfer simulation has not been performed.
- The present model is unsteady.
- The effect of gravity is neglected.
The following table represents a summary of the defining steps of the problem and its solution:
|Near wall treatment||Standard wall treatment|
|Fluid||Definition method||Fluent Database|
|Cell zone conditions|
|Mesh motion & Frame Motion||Rotational speed (40 rpm)|
|Axis direction||(-cos30 sin30 0)|
|Velocity magnitude||1 m/s|
|Turbulent viscosity ratio||10|
|Spatial discretization||Gradient||Least square cell-based|
|Run calculation||Time step size||0.05 s|
|Number of time steps||200|
|Max iterations per time step||20|
At the end of the solution process, two and three-dimensional contours and vectors related to water pressure and velocity are obtained. At first, water flow enters the inlet box, passes over the turbine blades, and finally moves to the outlet face. Also, static pressure contour is obtained in the whole domain, and as it can be seen, it decreases while passing through the channel.
You can obtain Geometry & Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.