Manifold, Two-way Thermal FSI, ANSYS Fluent CFD Simulation

Description

In this project, we present a simulation of an Exhaust Manifold under Thermal FSI via ANSYS software. We have modeled a simple exhaust manifold consisting of a fluid domain dedicated to the gas flow and a solid region as the manifold body surrounding the fluid zone.

What is FSI?

The gas flow is discharged through the exhaust manifold. So, the gas flow can expose a pressure load on the inner wall of the manifold. In such a condition, analysis of Fluid-Structure Interaction (FSI) becomes important. It means that both fluid and structural calculations are available.

Why Thermal FSI?

Hot gas flows throughout the exhaust manifold. So, it is expected that a thermal load will be imposed on the solid body. As a result, the focus is on the Thermal FSI. It means the solution data of fluid flow, structural, and thermal calculations are coupled.

1-way or 2-way?

First, the effect of the pressure and thermal loads of the gas flow on the inner wall of the exhaust manifold is analyzed. Next, the effect of the solid manifold structure, deformed or displaced, on the nearby gas flow is investigated. Hence, it is called Two-way FSI.

Methodology

For FSI simulations, we recommend two general methods: intrinsic FSI and extrinsic FSI. If the calculation of both the fluid and the structure is performed only in ANSYS Fluent, it is called Intrinsic FSI. Meanwhile, if the calculation process of the fluid and the structure is performed in different and individual solvers and then coupled with each other, it is referred to as Extrinsic FSI.

Extrinsic FSI:

In this project, we have used the external FSI method. We performed the structural analysis corresponding to the manifold solid body in the ANSYS Steady-State Thermal solver, while we performed the fluid analysis corresponding to the gas flow in the ANSYS Fluent (Fluid Flow) solver.

System Coupling:

The steady-state Thermal solver and the Fluent solver are defined separately in the ANSYS Workbench environment. Then, fluid and solid calculations are performed to obtain the solution data. In this case study, we consider the inner wall of the exhaust manifold as the fluid-structure interface to couple the calculations. Therefore, the data transfer between the fluid and structure solvers is defined by the System Coupling tool.

How to define Data Transfer?

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

Conclusion

We have investigated the results with two approaches: thermal fluid analysis (from Fluent) and thermal structural analysis (from steady-state Thermal).

Thermal Fluid:

We obtained the distribution of the temperature and heat flux of the airflow within the manifold exhaust, as well as the temperature and heat flux on the surface of the manifold’s internal wall. The results show that heat transfer occurs between the fluid flow and the structural body, such that the heat flux is lost from the hot stream adjacent to the inner wall of the manifold.

Thermal Structural:

We obtained the contours related to the temperature and heat flux distributions on the manifold structure body. The results show that heat transfer occurs between the fluid flow and the structural body, such that the heat flux is absorbed by the internal surface of the manifold body.