347
348
349
350
351
352
of the funnel’s exit cross-section (data collected by measuring using the pictures of ships from
Fleetmon). The reference temperature assumed for density estimation is 600 K, a value that
constitutes an assumption based on in-house exhaust measurement data on a variety of vessels.
Exhaust gas outlet speed is one of the most important parameters in gas dispersion because 11
affects plume rise (Dobrucali & Ergin, 2019; Li et al., 2022). Temperature is also a sub-parameter
that can define funnel exit speed, due to its input to the gas density estimation (ABS, 2019).
Mrotal =P'V'A
(13)
353
254
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
3 Results
3.1 Dispersion results from modelling
The plume dispersion in the computational domain is the base result of the approach. Figure
5 depicts an example of the modelled plume dispersion of Ship 1 (in grey colour) which originates
from the funnel and is transported by the wind in the x direction. The plume crosses the black
dotted line which indicates the relative location of the VMS, at 9 m above sea level. This height
corresponds to the average elevation of the real MS over the tide-influenced sea level. The VMS
position dots outside of the plume have zero concentration. The grided subdomain indicates the
plume’s spatial distribution in the three-dimensional coordinate system. In addition, the contour
plot presents the pollutant concentration in the plume (CO: in this case, but it is the same for SO2).
The contour plot is oriented vertically to the XY plane and along the VMS dotted line. The
pollutant concentration maximum is located at approximately 40 m above the water surface. The
yellow line demonstrates the concentration vertical profile at the maximum concentration of the
plume. The coordinates of the yellow line points in the xyz-coordinate system are 520 m, 0m, z
m (variable). The pollutant concentration profile exhibits an increasing trend from 0 to 40 m, and
a decreasing one above the 40-meter height level.
16
