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Figure 16.8: Convergence History of Total Mass in Domain

Figure 16.9: Convergence History of Evaporated Particle Mass

8. Save the case and data files (spray2.cas.gz and spray2.dat.gz).

File → Write → Case & Data...

16.4.10. Postprocessing

1.Display the trajectories of the droplets in the spray injection (Figure 16.10: Particle Tracks for the Spray Injection (p. 588)).

This will allow you to review the location of the droplets.

Results → Graphics → Particle Tracks → Edit...

a.Enable Draw Mesh in the Options group box.

The Mesh Display dialog box will open.

i.Retain the current display settings.

ii.Close the Mesh Display dialog box.

b.Retain the default selection of point from the Track Style drop-down list.

c.Select Particle Variables... and Particle Diameter from the Color by drop-down lists.

This will display the location of the droplets colored by their diameters.

d.Select injection-0 from the Release from Injections selection list.

e.Click Display. As an optional exercise, you can increase the particle size by clicking the Attributes... button in the Particle Tracks dialog box and adjusting the Marker Size value in the Track Style Attributes dialog box.

f.Close the Particle Tracks dialog box.

g.Restore the 30–degree section to obtain the view as shown in Figure 16.10: Particle Tracks for the Spray Injection (p. 588).

View → Display → Views...

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i.Click the Define... button to open the Graphics Periodicity dialog box.

ii.Click Reset and close the Graphics Periodicity dialog box.

iii.Close the Views dialog box.

h. Use the mouse to obtain the view shown in Figure 16.10: Particle Tracks for the Spray Injection (p. 588).

Figure 16.10: Particle Tracks for the Spray Injection

The air-blast atomizer model assumes that a cylindrical liquid sheet exits the atomizer, which then disintegrates into ligaments and droplets. Appropriately, the model determines that the droplets should be input into the domain in a ring. The radius of this disk is determined from the inner and outer radii of the injector.

Note

The maximum diameter of the droplets is about 4.9x10–5 m or 0.49 mm, which is simililar to the film height. The inner diameter and outer diameter of the injector are 3.5 mm and 4.5 mm, respectively. Hence the film height is 0.5 mm. The range in the droplet sizes is due to the fact that the air-blast atomizer automatically uses a distribution of droplet sizes.

Also note that the droplets are placed a slight distance away from the injector. Once the droplets are injected into the domain, their behavior will be determined by secondary models. For instance, they may collide/coalesce with other droplets depending on the secondary models employed. However, once a droplet has been introduced into the domain, the air-blast atomizer model no longer affects the droplet.

2.Display the mean particle temperature field (Figure 16.11: Contours of DPM Temperature (p. 590)).

Results → Graphics → Contours → Edit...

a.Ensure that Filled is enabled in the Options group box

b.Disable Draw Mesh.

c.Select Discrete Phase Variables... and DPM Temperature from the Contours of drop-down lists.

d.Disable Auto Range.

The Clip to Range option will automatically be enabled.

e.Click Compute to update the Min and Max fields.

f.Enter 260 for Min.

g.Select angle=15 from the Surfaces selection list.

h.Click Display and close the Contours dialog box.

i.Use the mouse to obtain the view shown in Figure 16.11: Contours of DPM Temperature (p. 590).

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Figure 16.11: Contours of DPM Temperature

3.Display the mean Sauter diameter (Figure 16.12: Contours of DPM Sauter Diameter (p. 590)).

Results → Graphics → Contours → Edit...

a.Enable Autorange in the Options group box.

b.Select Discrete Phase Variables... and DPM D32 from the Contours of drop-down lists.

c.Select angle=15 from the Surfaces selection list.

d.Click Display and close the Contours dialog box.

Figure 16.12: Contours of DPM Sauter Diameter

4.Display vectors of DPM mean velocity colored by DPM velocity magnitude (Figure 16.13: Vectors of DPM Mean Velocity Colored by DPM Velocity Magnitude (p. 592)).

Results → Graphics → Vectors → Edit...

a.Select dpm-mean-velocity from the Vectors of drop-down lists.

b.Select Discrete Phase Variables... and DPM Velocity Magnitude from the Color by drop-down lists.

c.Enter 7 for Scale.

d.Select angle=15 from the Surfaces selection list.

e.Click Display and close the Contours dialog box.

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Figure 16.13: Vectors of DPM Mean Velocity Colored by DPM Velocity Magnitude

5.Create an isosurface of the methanol mass fraction.

Results → Surface → Create → Iso-Surface...

a.Enter methanol-mf=0.002 for the New Surface Name.

b.Select Species... and Mass fraction of ch3oh from the Surface of Constant drop-down lists.

c.Click Compute to update the minimum and maximum values.

d.Enter 0.002 for Iso-Values.

e.Click Create and then close the Iso-Surface dialog box.

6.Display the isosurface you just created (methanol-mf=0.002).

Results → Graphics → Mesh → Edit...

a.Deselect atomizer-wall and select methanol-mf=0.002 in the Surfaces selection list.

b.Click the Colors... button to open the Mesh Colors dialog box.

i.Select surface in the Types list and green in the Colors list.

Scroll down the Types list to locate surface. The isosurface will now be displayed in green, which contrasts better with the rest of the mesh.

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ii. Close the Mesh Colors dialog box.

c.Click Display in the Mesh Display dialog box.

The graphics display will be updated to show the isosurface.

7.Modify the view to include the entire atomizer.

View → Display → Views...

a.Click Define... to open the Graphics Periodicity dialog box.

i.Select fluid from the Cell Zones list.

ii.Ensure that Rotational is selected from the Periodic Type list and the Number of Repeats is set to 12.

iii.Click Set and close the Graphics Periodicity dialog box.

b.Click Apply and close the Views dialog box.

c.Click Display and close the Mesh Display dialog box.

d.Use the mouse to obtain the view shown in Figure 16.14: Full Atomizer Display with Surface of Constant Methanol Mass Fraction (p. 595).

Figure 16.14: Full Atomizer Display with Surface of Constant Methanol Mass Fraction

e.This view can be improved to resemble Figure 16.15: Atomizer Display with Surface of Constant Methanol Mass Fraction Enhanced (p. 596) by changing some of the following variables:

•Disable Edges in the Mesh Display dialog box

•Select only atomizer-wall and methanol-mf=0.002 in the Surfaces list of the Mesh Display dialog box

•Change the Number of Repeats to 6 in the Graphics Periodicity dialog box

•Enable Lighting and change it to Flat in the View tab (Display group)

•Enable Headlight check in the View tab (Display group)