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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 the half width, export the X coordinate, Y coordinate, and Axial Velocity by going to File-Export to CFD Post (described at the bottom of Turbulent Jet - Turbulent Setup and Solution). Alternately, go . 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 ASCII type file. With the data, you can either copy it into Excel, or use a Matlab script and this function to read in ASCII files at the specified X locations. 

Using the Matlab script and plotting Y-coordinate approximate locations at which U=U_center/2 - (determined by examining the values read in to Matlab - ) gives the half width variation:. It appears to increase approximately linearly along X.

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.

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