Hi Denis,
to add another answer to your question, the OCL vessels used to berth at STL White bay in Sydney and as the terminal is below houses the residents used to complain about the exhaust gases blowing into their houses and the exhausts where raised and a diffuser added to help disperse the exhaust. This is happening again now with the cruise vessels using White bay and people complaining about the exhaust gases as there is no shore power available for the cruisers to use
regards Ron

SORRY.
the FLINDERS BAY photo and comments were on Shipsnostalgia

Thanks Denis.
In answer to your Question,It is something which has discussed in length before,If you go to my FLINDERS BAY photos from way back it is explained there by some Blokes who sailed on them,but in a nutshell they originally had an ordinary funnel which was added to later and the deflector at the top was called a turbulator and its purpose was to stop the exhaust smoke from hanging around the wheelhouse,to disperse it better if you like,if you find early photos of this class you will see the difference,no upward stem

Excellent photos of this containerships classic, Wayne!

Could anyone tell why she has such hight exhaust pipe or whatever that is? There's also like a some deflector at the top of it...