Concentration 
Low 
"High 
“—— 
“00 
Pe 
X Axis (m} 
| VMS line at 
| 9meters _ 
MIC 
NO 
Z Axis {m} 
Concentration Profile 
370 
mn 
L 
@ 
6 
L%“ 
© 
\ 
a. 
» 
© Concentration =. 
Y Axis {m} 
f 
371 
372 
373 
374 
Figure 5: Illustration of CFD plume dispersion (grey), considering Ship 1 case and VMS measurement points. Contour plot 
demonstrates the concentration at the plume’s slice cut vertically to VMS dotted line. The graph of concentration indicates the 
profile against height in Z-Axis. 
375 Figure 6 illustrates the rear view of a plane perpendicular to the Y and Z axis and the bottom 
376 view of the subdomain of Figure 5. Figure 6 presents the contour lines of the exhaust gas dilution 
377 ratio (DR) in these two views, corresponding to the Ship 1 case study. The DR at any given point 
378 xcorresponds to the ratio of the pollutant concentration at the funnel, just before the plume exits to 
379 the atmosphere, over the concentration at the specific point. The two views of Figure 6 indicate 
380 the track of the VMS as a dotted line. The grey-coloured plume is also illustrated to declare the 
381 spatial limits of the plume. 
382 The DR at the funnel level in a distance from 0 to 50 m increases from 1:1 at the funnel 
383 exit to 100:1 at a 50 m distance. With increasing distance from the ship’s funnel, the DR reaches 
384 a value of 10°: 1 in approximately 1350 m along the x-direction. The plume expansion in the z-axis 
385 ranges between 60 m, at the funnel to 220 m at a 1350 m distance. The height of the plume rise in 
386 our study is in the same order of magnitude as the results of Li et al. (2022), for similar conditions 
387 in the computational domain. The downward dispersion of the plume is affected by the vorticity 
388 that is created by the vessel’s structure. According to the DR contour lines, the concentration 
389 values in the vicinity of the vessel below the funnel exit height are higher than above, a behaviour 
390 that was also observed by Badeke et al. (2021). The contour lines of the bottom view of Figure 6 
391 depict the DR on a slice cut at 9 m height along the z-axis. Also, the VMS dotted line is depicted 
392 In Figure 6. The concentration of gaseous pollutants is lower at the height of 9 m than at the level