Page History

...

Let's get FLUENT to solve our nonlinear BVP. It'll introduce discretization and linearization errors in the process, as discussed in the Pre-Analysis step. We'll check the level of numerical errors later in the Verification & validation Validation step. There are lots of knobs in the Solution menu that you can twiddle to improve your numerical solution to the BVP. We'll not mess with most of these since the default settings yield an adequate numerical solution for our problem. We could get a slight improvement in accuracy by fiddling various knobs which we'll refrain from doing here.

Solution > Methods

The FLUENT solver converts our BVP to a set of algebraic equations through a process called discretization. We'll use second-order discretization for which the error is of the order of the square of the mesh spacing. This is more accurate (albeit less stable) than first-order discretization where the error is of the order of the mesh spacing.  Choose Second-Order Upwind for all equations as equations as shown below. Set Pressure-Velocity Coupling to SIMPLE if it is not by default.

To set the convergence criterion identified in the flowchart above , select:

...

Solution > Run Calculation 
Enter 500 for Number of Iterations and click Calculate. Note that 500 is the maximum number of iterations we want the solver to carry out. You will see a window message saying Calculating the solution... Wait for FLUENT to finish the calculation. Our solution converges in about 350 - 400  iterations. So the solver will stop the iterations before it reaches the maximum number of iterations specified (500). You should see a residual plot on screen as the computation is being performed. It should look something like this:below. At this point, we have a reasonable solution to the set of algebraic equations generated from the BVP using discretization. 

Save project and exit FLUENT:

...