...

Laminar Jet Results

From the converged solution, plot the stream function as you did in the previous section: Image Added

From these contours, you can observe that the air is being entrained near the jet inlet, and that the jet expands slightly along the x-direction. Also knowing that the flow velocity is related to the stream function Ψ by u = ∂Ψ/∂y and v = - ∂Ψ/∂x, one can see that the stream functions will be smaller in the entrainment and jet stream areas, because the flow is more strongly linear there. 

Now. go to 'Plots'-XY Plot and make a plot of how the axial velocity and half-width vary with axial distance x. These can be used to examine the self similarity of the solution. 

To make the plot of the velocity variation along the centerline, adjust the XY plot dialogue box (in particular, adjust the plot direction to be along X): Image Added
This will give you the centerline plot: Image Added

You can see that the axial velocity at the centerline (U_center) decreases sharply after the inlet, and that it will asymptotically approach 0m/s far from the jet. However, the half-width (Y distance at which U=U_center/2) increases along X as the spray expands into the environment. 

To obtain this distance, go to File-Export-Solution Data. Select 'X-coordinate', 'Y-coordinate', and 'Axial Velocity' as values to export. Export them along the centerline, and various X locations (like X=10D) as either an Ascii file to copy into Excel, or as a CFD-Post file. Plotting Y-coordinate approximate locations at which U=U_center/2 gives the half width variation:

Image Added

An additional step is to plot the self-similar profiles U/U_center at various X locations, using the same exported data. The profiles appear to be self similar, although at X values closer to the inlet they will not match exactly due to the additional entrainment effects.

Image AddedAlso skip this step!

Go to Step 4: Turbulent Jet Setup and Solution

...