This chapter reviews the general concepts of fluid-structure interaction (FSI). It discusses the fluid computations in the Fluent solver and the solid computations in the Structural solver, and focuses on establishing data transfer between fluids and structures. As a suitable and common method, it introduces the system coupling tool for defining data transfer. In addition, it refers to one-way and two-way FSI to clarify their differences from an analytical perspective.

This chapter examines the detailed concepts of the intrinsic fluid-structure interaction (FSI). In order to reduce the computational cost, it is possible to eliminate the use of external solvers and perform simultaneous fluid and solid calculations with the Fluent solver alone. In this case, there is no need for data transfer and system coupling by the exterior solver. So, this is known as intrinsic FSI. This chapter describes the structure model in the Fluent solver. These computations can be performed in both linear elasticity and nonlinear elasticity modes.Then, it discusses the equations and relations related to the fluid and solid computations. These governing relations consist of applied forces (from the fluid), displacements (through the structure boundary), and ultimate deformations. In addition, it refers to one-way and two-way FSI to clarify their differences from an analytical perspective.

Description In this project, we present a simulation of a Fish Cage floating on the seawater via ANSYS software.  Since the fish cage is floating on seawater, an interaction occurs between the water waves and the cage structure. First, the water flow exerts a volume force on the cage's body by hitting it. Subsequently, displacement or deformation appears on the cage body, which can lead to the water flow being affected. Therefore, we intend to perform a numerical simulation of the fish cage 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 marine environment that includes both fluid and solid domains. There is a solid cage structure within the fluid environment, which is water up to a certain level and airflow above it. We meshed the computational domain via ANSYS Meshing software. The mesh is of an unstructured type, and approximately 490,000 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, we considered the fish cage floating on seawater. Therefore, we used a Multiphase model to define the water level above which the air exists. So, for defining a two-phase flow, we used the volume of fluid (VOF) model. Results We analyzed the results in two fluid and solid approaches: In Fluent, we studied the behavior of water flow. For this, we obtained the distributions of the pressure, velocity, and volume fraction of water. The results show that the water flow collides with the fish cage body in a wave mode and, as a result, exerts a hydraulic force on the cage structure.  In Structural Transient, we studied the behavior of the fish cage body under the influence of the applied forces of the water flow. For this, we obtained the distribution of the deformation, von Mises stress, and elastic strain. The results confirm that the water flow affects the cage structure and, as a result, parts of it undergo deformations and displacements. In conclusion, we can claim that we carried out the simulation project of a fish cage correctly and acceptably by using the two-way FSI method.

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.

Description In this project, we present a simulation of a Horizontal-Axis Water Turbine (HAWT) via ANSYS software.  Since the turbine blades are exposed to water flow, an interaction occurs between the water flowing and the turbine blades' structure. So, the water flow exerts a hydraulic force on the blades' body by hitting it. Therefore, we intend to perform a numerical simulation of the water turbine 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 only the effect of fluid on the structure, and there is no need to account for the effect of the structure on the fluid. So, we choose One-way FSI, which is a simple and less-expensive approach.  We modeled the geometry via Design Modeler software. The computational domain is a sample space for water flow, in which a distinct fluid region is defined around the turbine body. The turbine is of the horizontal-axis type and includes three blades.  We meshed the computational domain via ANSYS Meshing software. The mesh is of an unstructured type, and approximately 3,400,000 cells have been generated. Methodology Fluid-structure interaction can be performed in two general methodologies: In the ANSYS Workbench environment, using an external solver Only in the Fluent solver (in the form of an intrinsic FSI). For one-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 Transfer data directly from the fluid solver to the structural solver Since we were analyzing one-way FSI and not considering the effect of structural displacement on the adjacent fluid, we didn't need to use the dynamic mesh model. In addition, we used the Multiple Reference Frame (MRF) to define a rotational flow with a certain angular velocity in the region around the turbine body. Results We analyzed the results in two fluid and solid approaches: In Fluent, we studied the behavior of water flow around the turbine. For this, we obtained the distributions of the pressure and velocity of water near the blades. The results show that the water flow collides with the rotating blades' body and, as a result, exerts a hydraulic force on the turbine structure. In Structural Transient, we studied the behavior of the turbine blades' body under the influence of the applied forces of the water flow. For this, we obtained the distribution of the deformation, von Mises stress, and elastic strain. The results confirm that the water flow affects the turbine blades' structure. In conclusion, we can claim that we carried out the simulation project of a HAWT correctly and acceptably by using the one-way FSI method.

Description In this project, we present a simulation of a Blood Vessel via ANSYS Fluent software.  Since the vessel is exposed to blood flow, an interaction occurs between the blood flowing and the vessel structure. First, the blood flow exerts a force on the vessel's body by hitting it. Subsequently, displacement or deformation appears on the vessel, which can lead to the blood flow being affected. Therefore, we intend to perform a numerical simulation of the blood vessel 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 Spaceclaim software. The computational domain is a sample space of a vascular system with a simple construction. We considered the blood vessel as a horizontal cylinder with a solid layer surrounding the fluid region.  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 Fluent environment. In other words, the Fluent solver performs both fluid and solid calculations simultaneously.  For two-way FSI in Fluent solver, the Structure model is utilized. The structural model can be implemented in two ways: Linear elasticity: The deformation is proportional to the applied force. In this case, the deformations are usually small, and the calculation process is faster. Nonlinear elasticity: The deformation is not necessarily proportional to the applied force. In this case, the deformations are usually large, and the calculation process is more complex and time-consuming. In this project, we considered fluid-structure interaction in the form of a Linear Elasticity state. Since we were analyzing two-way FSI and considering the effect of structural displacement on the adjacent fluid, we used the Dynamic Mesh model. In other words, we establish a connection between the fluid and structural calculations with the Intrinsic FSI option. Then, we enabled the smoothing and remeshing methods to define a deformable mesh.  In addition, for defining blood flow in a pulse-mode, we used a user-defined function (UDF) so that the flow has a variable velocity with respect to time.  Results We analyzed the results in two fluid and solid approaches: In a fluid view, we studied the behavior of blood flow. For this, we obtained the distributions of the pressure and velocity of blood. The results show that the blood flow collides with the vessel body at pulsatile speed and, as a result, exerts a hydraulic force on the vessel structure. In a solid view, we studied the behavior of the vessel body under the influence of the applied forces of the blood flow. For this, we obtained the distribution of the von Mises stress and displacements (in all directions). The results confirm that the blood flow affects the vessel structure and, as a result, it undergoes deformation relative to the initial state. In conclusion, we can claim that we carried out the simulation project of a blood vessel correctly and acceptably by using the two-way FSI method.

Description In this project, we present a simulation of a Horizontal-Axis Water Turbine (HAWT) via ANSYS Fluent software.  Since the turbine blades are exposed to water flow, an interaction occurs between the water flowing and the turbine blades' structure. First, the water flow exerts a hydraulic force on the blades' body by hitting it. Subsequently, displacement or deformation appears on the turbine, which can lead to the water flow being affected. Therefore, we intend to perform a numerical simulation of the water turbine 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 for water flow, in which a distinct fluid region is defined around the turbine body. The turbine is of the horizontal-axis type and includes three blades.  We meshed the computational domain via ANSYS Meshing software. The mesh is of an unstructured type, and approximately 3,400,000 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 Fluent environment. In other words, the Fluent solver performs both fluid and solid calculations simultaneously.  For two-way FSI in Fluent solver, the Structure model is utilized. The structural model can be implemented in two ways: Linear elasticity: The deformation is proportional to the applied force. In this case, the deformations are usually small, and the calculation process is faster. Nonlinear elasticity: The deformation is not necessarily proportional to the applied force. In this case, the deformations are usually large, and the calculation process is more complex and time-consuming. In this project, we considered fluid-structure interaction in the form of a Linear Elasticity state. Since we were analyzing two-way FSI and considering the effect of structural displacement on the adjacent fluid, we used the Dynamic Mesh model. In other words, we establish a connection between the fluid and structural calculations with the Intrinsic FSI option. Then, we enabled the smoothing and remeshing methods to define a deformable mesh.  In addition, we used the Multiple Reference Frame (MRF) to define a rotational flow with a certain angular velocity in the region around the turbine body. Results We analyzed the results in two fluid and solid approaches: In a fluid view, we studied the behavior of water flow around the turbine. For this, we obtained the distributions of the pressure and velocity of water near the blades. The results show that the water flow collides with the rotating blades' body and, as a result, exerts a hydraulic force on the turbine structure.  In a solid view, we studied the behavior of the turbine blades' body under the influence of the applied forces of the water flow. For this, we obtained the distribution of the von Mises stress and displacements (in all directions). The results confirm that the water flow affects the turbine blades' structure. In conclusion, we can claim that we carried out the simulation project of a HAWT correctly and acceptably by using the two-way FSI method.

Description In this project, we present a simulation of an Airfoil exposed to the airflow via ANSYS Fluent software.  Since the airfoil is exposed to airflow, an interaction occurs between the wind blowing and the airfoil structure. It means that airflow exerts a volume force on the airfoil's body by hitting it. 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 only the effect of fluid on the structure, and there is no need to account for the effect of the structure on the fluid. So, we choose One-way FSI, which is a simple and less-expensive approach.  We modeled the geometry via SpaceClaim 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 1,700,000 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 one-way FSI in the ANSYS Fluent environment. In other words, the Fluent solver performs both fluid and solid calculations simultaneously.  For two-way FSI in Fluent solver, the Structure model is utilized. The structural model can be implemented in two ways: Linear elasticity: The deformation is proportional to the applied force. In this case, the deformations are usually small, and the calculation process is faster. Nonlinear elasticity: The deformation is not necessarily proportional to the applied force. In this case, the deformations are usually large, and the calculation process is more complex and time-consuming. In this project, we considered fluid-structure interaction in the form of a Linear Elasticity state. Since we were analyzing one-way FSI and not considering the effect of structural displacement on the adjacent fluid, we didn't need to use the dynamic mesh model. Results We analyzed the results in two fluid and solid approaches: In a fluid view, 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 a solid view, we studied the behavior of the airfoil body under the influence of the applied forces of the air flow. For this, we obtained the distribution of the von Mises stress and displacements (in all directions). 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.