Examining Plots

Given that the y+ contours indicate that the wall data are reasonably accurate, we can estimate the length of the recirculation zone from the wall shear stress plot:

Select the WSS Plot tab at the top of the Display window.

Recirculation zones occur upstream and downstream of the obstacle. These are visible on the graph as regions where the wall shear stress is negative. To determine the length of the downstream recirculation zone:

Select the Plots > WSS Plot > Y Types > Y Type 1 > Y = 0 node.

In the Properties window, select the Sort Plot Data property.

Select the Line Style node within the Y = 0 node.

In the Properties window, change the Style property to Solid.

Select the Symbol Style node.

Change the Shape property to None.

Select the Plots > WSS Plot > Axes > X Axis > Labels node.

Change the Maximum and Minimum properties to 0.9 and 0.3, respectively.

Change the Label Spacing property to 0.05.

Select the Labels node within the Y Axis node.

Change the Maximum property to 0.005.

Change the Label Spacing property to 0.005 also.

The above plot shows that the downstream recirculation zone extends from approximately X = 0.37 m to X = 0.73 m and hence is roughly 0.36 m in length. This is the same as the value predicted by the tetrahedral mesh analysis but about 20% shorter than that predicted by the hexahedral mesh analysis.

The final section of this tutorial, Comparing Mesh Types, will consider which mesh has produced the most accurate solution.