Bent Pipe, Thermal FSI, ANSYS Fluent CFD Simulation

Description

In this project, we present the CFD simulation of a Bent Pipe under Thermal FSI in ANSYS Fluent software.

We studied a simple pipe containing two bends in the fluid flow path. Water flows through the pipe as a fluid at a certain velocity and temperature.

On the one hand, hydraulic fluid flow can generate a pressure load on the inner wall of the pipe, and on the other hand, hot fluid flow may produce a thermal load on the pipe wall.

Therefore, we intend to analyze the fluid-structure interaction, which is known as FSI. As we also aim to take into account the thermal effect, it is called the thermal FSI.

Note that since we want to first analyze the effect of the fluid’s motion and thermal loads on the pipe wall and, consequently, the effect of pipe deformation on the neighboring fluid flowing, we use a two-way FSI approach.

Methodology

First, we modeled the computational domain in Design Modeler software. We designed a simple pipe with two elbows. It consists of two regions: the inner fluid zone corresponds to the fluid flow, and the outer solid zone is dedicated to the pipe body. Next, we meshed all domains in ANSYS Meshing software, so that about 227,000 elements were generated.

Finally, we performed the numerical simulation of the flow pipe in ANSYS Fluent. We performed the present project in two steps: first, we focused only on the hydraulic flow as the FSI; second, we also applied the thermal flow to achieve the thermal FSI analysis.

Typically, an external solver is used as a system coupling to define data transfer between the fluid and structural solvers. However, in this project, we utilized the Fluent solver to model the fluid and solid interaction (without the need for an extrinsic solver).

This approach is known as intrinsic FSI. For this purpose, we used the Structure model to analyze FSI. Then, we used the linear elasticity method for structural analysis, meaning that the structure’s deformation is proportional to the amount of force exerted by the fluid.

Since solid body deformation affects fluid flow, we used the Dynamic Mesh model. This causes the mesh to deform over time in the fluid domain.

Conclusion

After the calculation process, we represent the analysis from the perspective of the interaction between fluids and solids. Note that we aim to provide a comparative analysis between the FSI due to the lonely fluid pressure load and the FSI affected by the addition of thermal load.

Therefore, we obtained the contour of distribution of the total displacement and von Mises stress, both for the inner wall of the pipe, which is exposed to the fluid flow, and for the outer wall of the pipe, which is freely movable.

The results show that the maximum displacement is achieved in the bends or elbows. This indicates that these regions undergo the highest deformation due to the fluid flowing.

Also, in bends and elbows, the stress is significant. However, since the two ends of the pipe are considered as fixed supports, the maximum stress is shown.