Week 8- Moving zones approach in Fluent

Introduction: Computation of fluid flow requires the domain to be steady but in some cases (a pump) it is crucial to simulate the flow under working conditions. For this situation fluent will consider this as an unsteady problem, to resolve this and making the problem steady methods are implemented which are given below:

1) Moving reference frame

Moving reference frame is a way to simulate a moving wall problem. The frame moves in this approach. Frame as a whole moves the mesh topology does not change, ie only the boundary moves(no bc the interface boundary). Used in steady phenomenon.

• Multiple ref frame
• Single ref frame

Data is transferred from the moving frame to the stationary frame and the calculation are done using 3 approaches.

• Area averaging
• Mass averaging
• Mixed out approach.

The averaging is done over the interface.

2) Moving Mesh (Dynamic meshing) (For unsteady problems)

In some cases there is a need to understand the flow after the interaction with the solid or any obstruction to the free flow. In these cases the solid/obstruction is also moving and this causes the fluid to react accordingly as to at times also detaches from the solid. In these cases one would like to observe the fluid and solid (Moving) interaction. This being phenomenon pf high randoness and cruicial importance to the problem statement we use dynamic meshing technique to simulate this flow. For example, in a pump the impeller blade will be moving and the fluid interaction would be important to understand as it is crucial for pump performance. Moving mesh would be able to resolve this and will help understand the flow properties.

For the given geometry :

Setup for moving reference frame:

Boundary condition for airfoil:

The rest of the setup is setting up the viscous model: K-epsilon (Realizable) with enhanced wall functions with a courant number of 10.

The moving reference frame gives he velocity profile:

The pressure contour is as shown:

The moving reference frame has performed as expected and produced result that are appritiable. Hence, we can conclude that the simulation is successful.