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525 
526 Figure 11: (a): Different angles of VMS line, (b): alteration of CO, concentration time-series shape for different angles compared 
527 to the baseline. 
528 An additional analysis was conducted, in the current study, to demonstrate the importance 
529 of the vessel’s bulk consideration in modelling, which is responsible for the plume rise and the 
530 downwash phenomena. To investigate this, a supplementary simulation of Ship 1 setup was 
531 conducted, wherein all the ship's geometry was removed from the computational domain, keeping 
332 only the exhaust surface to model the plume dispersion. The results of the simulations for Ship 1, 
333 presented in Figure 12, indicate a significant -90% underestimation in concentration levels in the 
334 scenario where only the exhaust was considered (grey line), compared to the scenario where the 
535 ship's bulk was included (orange line). The underevaluation in the only exhaust scenario is 
536 reflected in the MOP which equals 14 ppm while the MOP of the scenario that accounts the 
537 vessel’s bulk equals 107 ppm. The time-series duration was the only similarity between the orange 
538 and grey lines. The comparison of the measurements with the only exhaust scenario in Figure 12, 
339 reveals the undervaluation in concentrations and peaksum since MEP equals 73 ppm. Badeke et 
540 al. (2021) also observed a similar phenomenon in their study of downward dispersion, using the 
5341 micro-scale MITRAS model. They investigated two scenarios, one with the vessel’s bulk present 
542 and one with the vessel's bulk absent. The results showed that the scenario where the vessel's bulk 
343 was considered, had 25% more downward dispersion compared to the scenario where the vessel’s 
7,