544 bulk was absent. Therefore, the findings demonstrate that it is crucial to include the vessel’s bulk 
545 in modelling. 
50 
= 
50 - 
= 40 - 
30 - 
20 - 
CO, Time-series of Ship 1 
-Measurement 
Simulation 
‚Simulation (only exh.)} 
10 
«r 
' 
n 
+ 
700556288000 
Time (s) 
546 
547 Figure 12: Illustration of the time-series for Ship 1: Scenario where only the exhaust was considered in the computational 
548 domain by removing the rest of the vessel’s bulk (grey), compared to the original simulation results (orange) and measured data 
549 (yellow). 
550 3.3 Assessment of the modelling results 
551 The comparison between the modelling and the measured results is performed by 
552 comparing the MOP and the MEP values for the pollutants examined (Table 6). Table 6, also 
353 presents the relative error between MOP and MEP for the comparison of CO2 and SO2. The CO2 
3554 MOP values for Ship 1,2, 3 and 4 are higher than the corresponding MEP ones, but this is opposite 
3555 (or Ship 5. This comparison shows that a clear signal of CO2 can be detected above the background 
556 (which is at 412 ppm) for all five vessels. Moreover, the CFD model results are at the same level 
357 as the measurements, despite the assumptions related to engine operation and exact funnel-out 
558 concentrations. Finally, CFD modelling rather presents an overestimation of concentrations with 
3559 the exception of Ship 5. Peaksum SOz2 values for Ships 1-4 exhibit the same trend with CO>», 
560 resulting in comparable data with the measurements, since the order of magnitude is the same. The 
561 Ship 5 case is not included in the analysis of SO: since the FSC is below the detection limit of the 
5362 measurement. The evaluation shows that CFD modelling is proper for the detection of 
363 xconcentrations at very low heights above the water level since the VMS is located at a 9 m height 
564 above the water level. Thus, the methodology can be used in applications connected to the 
365 prediction of gaseous pollutants very close to the water surface (e.g., for the exchange of gaseous 
566  pollutants at the air-water interface). 
Table 6: MEP and MOP values for all case studies considering CO2 and SO-,. Also, the relative error between MOP and MEP is 
presented. 
Ship Number 
CO: MEP | CO:.MOP 
(ppm) | (ppm) 
CO. rel. 
error (%) 
| SO2MEP | SO.MOP | SO. rel. 
(ppb) (ppb) error (%) 
JR