Horizontal Axis Wind Turbine (HAWT) Aerodynamic, ANSYS Fluent Training
$22.00
This project is going to simulate an airflow field close to a standard horizontal axis wind turbine using ANSYS Fluent software.
This product includes Geometry & Mesh file and a comprehensive Training Movie.
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Description
Introduction
Standard Horizontal Axis Wind Turbine (HAWT) is becoming ever more critical in wind power generation. Fortunately, it is known that HAWTs have higher efficiency compare to VAWTs. Thus, they have been employed in open fields and can produce energy from the wind.
As wind tunnel experiments are expensive in terms of both costs and time, another way to study the aerodynamic behavior of the wind turbine is to use CFD. As it is known, CFD resolves the fluid dynamic equations, and it is certainly more realistic. In this regard, CFD has been employed to evaluate this type of turbine evaluation in this study.
HAWT Project Description
This project is going to simulate an airflow field close to a standard horizontal axis wind turbine by ANSYS Fluent software. The geometry included a rotary zone for the turbine walls and a stationary zone for the rest of the domain. The inlet is considered to wind with 1 m/s, and the turbine zone is rotating with 16 RPM. The purpose of this study is to investigate the behavior of airflow and pressure distribution and study drag force.
Mathematical Modeling
To study a horizontal axis wind turbine, one must solve the flow equations in the differential form. Assuming an isothermal, incompressible condition for the air around the blades, two forces known as the Coriolis and centripetal accelerations are the primary source terms exerting on the flow elements. These forces are appearing as the rotating zone starts to move in the current simulation. Briefly, the governing mass and momentum equations are written as follows:
HAWT Geometry and Mesh
As a numerical study, the initial step towards the modeling is the production of the CAD geometry, which is depicted below. The blue face is considered as the inlet of the domain, while the red face on the other side is considered the outlet. The current computational domain is the representation of the wind turbine that we have evaluated the turbine. For the current problem, a mesh count of 2,463,521 elements was created to represent the geometry. Regarding the quality of the mesh, the maximum skewness of 0.91 with an average of 0.26 is a good mesh for the current problem. In addition, for an interested reader, the quality distribution of mesh is shown as follows. Also, 5 prism layers were added adjacent to both wind tunnel walls and the turbine body to accurately calculate the boundary layer. Finally, the mesh is generated through ANSYS-Meshing and is as below.
As a final note, due to having a turbomachinery simulation, a cylindrical zone has been separated from the whole computational geometry (gray zone) and later represented as the rotary geometry.
HAWT CFD Simulation
By importing the mesh into the ANSYS-FLUENT solver, we start the calculation procedure. As discussed before, an incompressible, isothermal condition has found to be a valid assumption for the current simulation. However, we ignore the gravity for two main reasons. First, the gravity source would produce equivalent force for the fluid cells if we consider an isothermal condition. Thus, it won’t affect the characteristic of the fluid flow.
Moreover, the flow field is fully turbulent. Thus, we select the k-w-SST turbulent model for the evaluation of eddies. The noted model has been more accurate than any other eddy-viscosity variation due to a hybrid formulation that takes care of both wall effects and the core flow strain rate. Details of the solution setup are as follows:
Solver settings: | |
Type: | Pressure-based |
Velocity formulation: | Absolute |
Time setting: | Steady-state |
Gravity: | Off |
Energy: | Off |
Model: | k-w-SST |
Zone: | Static fluid zone: Rectangular Box: default
Rotary fluid zone: Cylindrical: Frame Motion Axis: X-direction Axis point: (0,0,0) Rotational Speed: 16 RPM |
Boundary conditions: | Turbine Walls: No-slip
Inlet: velocity inlet: 1 m/s Outlet: pressure outlet FarWalls: Symmetry |
Operating Condition: | Reference Pressure Point: 101325 Pa |
Solver Properties: | |
Solution methods: | SIMPLE |
Pressure interpolation scheme: | Second-Order |
Momentum: | Second-Order |
Turbulence: | First-Order |
Relaxation: | Default
Number of Iterations = 1000 |
Initialization: | Standard > from inlet |
Material used: | |
Fluid: | Air – constant properties
Density: 1.225 kg/(m^{3}) Viscosity: 1.7894×10^{-5} (Pa.s) |
Monitor: | Drag Value of Blade wall in X-direction |
Results and Discussions
After the solution convergence, we observe the results through post-processing. Meanwhile, as an assurance for a valid convergence, we monitor the drag value during the solution iterations. In this study, the solution converged one when the drag force reached a constant rate, and the residuals were below 10^{-6} values. As an initial check, we evaluate the max value of yplus (Y+) to decide the consistency of the boundary layer mesh. Fortunately for this case, the maximum Y-plus value was less than 231, lower than 300.
Afterward, we show the results regarding the pressure and the velocity field below the figures. The leading edge of the turbine wall corresponded to the lowest pressure, which is entirely logical since the velocity has the highest value on the tip of the turbine blade.
Results and Discussions
For the velocity field, we present both contour and streamlines to give much insight into the problem. Briefly, the velocity field adjacent to the wall of the turbine has the highest gradient. This could be, again, observed through the velocity vectors. Additionally, the streamlines vectors illustrate the quality of the flow streams resolved in the wake section, which is the core challenge of aerodynamic simulation.
Finally, we calculate the drag force equal to 243.63 (N), which is accurate for a 3-meter turbine with the noted specifications.
You can obtain Geometry & Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.
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