FSI and Vibration Analysis of an Airfoil

Description

In this project, we present a simulation of an Airfoil exposed to the airflow via ANSYS software.

Since the airfoil is exposed to airflow, an interaction occurs between the wind blowing and the airfoil structure. First, the airflow exerts a volume force on the airfoil's body by hitting it. Subsequently, displacement or deformation appears on the airfoil, which can lead to the airflow being affected. Therefore, we intend to perform a numerical simulation of the airfoil as a Fluid-Structure Interaction (called FSI).

The interaction between fluid and structure can be implemented as:

• One-way FSI

• Two-way FSI

In this project, we aim to analyze both the effect of fluid on the structure and the effect of the structure on the fluid. So, we choose Two-way FSI, which is a more accurate and realistic but more complex approach.

We modeled the geometry via Design Modeler software. The computational domain is a sample space of the surrounding air that includes both fluid and solid domains. There is a solid airfoil structure within the fluid environment, which is considered fixed from the center.

We meshed the computational domain via ANSYS Meshing software. The mesh is of an unstructured type, and approximately 56,000 cells have been generated.

Methodology

Fluid-structure interaction can be performed in two general methodologies:

• In the ANSYS Workbench environment, using an external solver (specifically, system coupling)

• Only in the Fluent solver (in the form of an intrinsic FSI).

In this project, we implemented a two-way FSI in the ANSYS workbench environment.

For two-way FSI with an external solver, three main steps are required:

• Simulation of the fluid domain from the model using the Fluent solver

• Simulation of the solid domain from the model using the Transient Structural solver

• Definition of the Data Transfer between the fluid and structural solvers using the System Coupling tool

For utilizing the system coupling, we define two data transfers:

• In the form of Forces to the interface wall (from the fluid solver to the structural solver)

• In the form of Displacements of the interface wall (from the structural solver to the fluid solver)

Since we were analyzing two-way FSI and considering the effect of the structure's displacement on the adjacent fluid, we used the Dynamic Mesh model. In other words, we establish a connection between the fluid and structure calculations with the System Coupling option. Then, for defining a deforming mesh, we enabled the smoothing and remeshing methods.

In addition, because of the aerodynamic nature of the airfoil and the very high airflow velocity, we considered a density-based solver.

Results

We analyzed the results in two fluid and solid approaches:

In Fluent, we studied the behavior of airflow. For this, we obtained the distributions of the pressure and velocity of air. The results show that the airflow collides with the airfoil body at high speed and, as a result, exerts a hydraulic force on the airfoil structure.

In Structural Transient, we studied the behavior of the airfoil body under the influence of the applied forces of the airflow. For this, we obtained the distribution of the deformation, von Mises stress, and elastic strain. The results confirm that the airflow affects the airfoil structure and, as a result, it undergoes displacements relative to the fixed center.

In conclusion, we can claim that we carried out the simulation project of an airfoil correctly and acceptably by using the two-way FSI method.