# Pre-Analysis & Start-Up — Lesson 2

## Pre-Analysis

In the Pre-Analysis step, we'll review the following:

• Mathematical model: the governing equations + boundary conditions and the assumptions contained within the mathematical model.
• Numerical solution procedure in the Ansys solver: the solution strategy used by Ansys compared to the hand calculation approach.
• Hand-calculations of expected results: an analytical solution of the mathematical model to predict the expected stress field from Ansys Fluent. We'll pay close attention to additional assumptions that have to be made in order to obtain an analytical solution.

### Mathematical Model

Similar to the previous method, but considering a rotating frame of reference for the hub.

In part 1 we only analyzed one position of the hub relative to the incoming wind, which might be an over-simplification. We also didn't account for the vortices generated by the blades passing upwind on the blades downstream.

All of these will be accounted in this Sliding Mesh method. In this case, Fluent will actually move all components of the geometry and solve a transient problem.

### Numerical Solution Procedure in Ansys Fluent

Similar to part 1, but now Fluent will iterate in each time step until it either converges, or reaches the maximum iterations per time step defined by the user.

### Expected Results

We expect a similar distribution of Velocity, Vorticity and Turbulent KE. We also expect the Moment coefficient to be oscillatory.

Text summary of the above video
• Open the file from part 1 of the tutorial.
• Duplicate the project
• Name it "Sliding Mesh."
• Click and drag the "Solution" cell from MFR into the Solution cell of the new Sliding Mesh project.

## Geometry

The geometry was incorporated into the project when we dragged the Solution cell from the MFR project into the Sliding Mesh project.

## Mesh

Again, this has already been set. We don't need to import the mesh again.