T-Junction, Thermal FSI, ANSYS CFD Simulation

Description

In this project, we present a simulation of a T-junction Pipe under Thermal FSI via ANSYS software. We have modeled a simple T-junction containing a main pipe and a branch, so that two streams with different temperatures would be mixed. The computational domain consists of a fluid zone dedicated to the streams and a solid region as the pipe body surrounding the fluid zone.

What is FSI?

Two fluid streams flow through the T-junction pipe. So, the fluid flow can expose a pressure load on the inner wall of the T-junction pipe. 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?

Two streams with different temperatures flow throughout the T-junction. 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?

Only the effect of the pressure and thermal loads of the flow on the inner wall of the T-junction pipe is analyzed; no need to consider the effect of the solid T-junction structure on the nearby flow. Hence, it is called One-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 and thermal analysis corresponding to the T-junction solid body in the ANSYS Static Structural and ANSYS Steady-State Thermal solvers, respectively, while we performed the fluid analysis corresponding to the streams in the ANSYS Fluent (Fluid Flow) solver.

How to use solvers?

The static Structural solver, 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 T-junction pipe as the fluid-structure interface to couple the calculations.

How to couple solvers?

Note that the data between the fluid and structural solvers is transferred directly. First, by Fluent calculation, the thermal data from the fluid flow is transmitted as input in the form of Temperature Load to the Thermal solver. Then, on one hand, by steady-state Thermal calculations, the thermal data in the form of Temperature Body Load from the thermal solver, and on the other hand, by Fluent calculations, the flow data in the form of Pressure Body Load are transmitted to the static Structural solver.

Conclusion

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

Fluid:

We obtained the distribution of the temperature and pressure of the water flowing within the T-junction, as well as the surface temperature and pressure on the internal wall of the T-junction.

Thermal:

We obtained the contours related to the temperature distributions on the T-junction structure body. The results show that heat transfer occurs between the fluid and the structure.

Structural:

We obtained the contours related to the total deformation and von Mises stress on the T-junction structure body. The results confirm that the T-junction body undergoes considerable deformation under pressure and thermal stresses.