Description

In this project, we present the CFD simulation of the thermal behavior of an Exhaust Manifold under Fluid-Structure Interaction (FSI) in ANSYS software.

We consider a simple exhaust manifold through which a hot gas flow is discharged. On the other hand, the outer walls of the manifold body are exposed to convection heat transfer with the surrounding. As a result, heat transfer occurs between the manifold body and the gas stream.

In such a condition, we can implement thermal simulations of the fluid and the structure simultaneously. So, we model a computational domain consisting of the fluid zone for the airflow and the solid zone for the manifold body. For this, it is known as thermal fluid-structure interaction (FSI).

Since we intend to evaluate both the effect of the heat flow from the fluid on the manifold body and the effect of the temperature of the solid boundary on the adjacent flowing fluid, we utilize a Thermal Two-Way FSI.

Methodology

In the first step, we model the computational domain in Design Modeler software. We design a three-branch internal domain for fluid flow that is enclosed within a manifold body as a solid body.

We use the solid body for simulation in ANSYS Steady-State Thermal, and the fluid zone inside it for simulation in ANSYS Fluent software.

In the second step, we describe the simulation in Fluent software. Before that, we mesh the fluid domain in ANSYS Meshing software, so that about 231,000 elements are generated.

For thermal FSI simulation in Fluent, we define the System Coupling as the thermal condition. In other words, the internal wall of the manifold (adjacent to the fluid flow) conducts heat transfer into the solid body through a system coupling.

In the third step, we describe the simulation in Mechanical (Steady-State Thermal) software.

We define the Convection thermal condition for the external walls of the manifold body. Besides, we define the internal wall of the manifold as a System Coupling Region. As a result, the temperature distribution of the manifold structure can be affected by the hot stream.

In the final step, we describe the procedure in the System Coupling tool. By this, the Fluent and mechanical calculations are linked.

In the coupling system, we define two Data Transfers. One is the data transfer in the form of Heat Flow from fluid to structural, and the other is the data transfer in the form of Temperature, from structural to fluid.

It means that first the hot fluid flow transfers heat to the structure body, and then the temperature distribution on the structure affects the temperature of the fluid adjacent to it.

Conclusion

After the calculation process, we present both the Thermal Fluid analysis and the Thermal Structural analysis.

So, in Steady-State Thermal, we obtain the contours of Temperature and Heat Flux on the manifold structure body. On the other hand, in Fluent, we obtain the temperature and heat flux distribution of the airflow within the manifold, as well as the temperature and heat flux on the surface of the manifold's internal wall.

Note that we provide the contours of temperature and heat flux on the manifold structure in a way that shows the procedure for reaching from the initial to the stable distribution.

The results show that heat transfer occurs properly between the fluid flow and the structural body. It means that the heat flux is lost from the hot stream adjacent to the inner wall of the manifold and absorbed by the internal surface of the manifold body.