Sign-up for free online course on ANSYS simulations!Unable to render {include} The included page could not be found.
Unable to render {include} The included page could not be found.
Laminar Jet Results
From the converged solution, plot the stream function as you did in the previous section:
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 as below (in particular, adjust the plot direction to be along X):
This will give you the centerline plot:
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.
To obtain the half width, export the X coordinate, Y coordinate, and Axial Velocity. 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 an 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 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.
