Trans RINA, Vol 156, Part B2, Intl J Small Craft Tech, Jul-Dec 2014


An example of the results obtained is summarized in Figure 14: each sampling port is identified by an ID number and a short description which indicates the placement on the ship model. In the column on the right the measured CO2 concentration values are reported.


The concentration values obtained are very close to the detection limit of the instrument, (0.01% by volume). Such low concentrations suggest that no problem with the dilution of the exhaust or their stagnation in critical parts of the yacht should be expected.


4.4 FLOW VISUALIZATIONS


Yacht aerodynamics and comfort assessment can be further investigated in the wind tunnel by means of flow visualization techniques.


Smoke visualization for instance of the


allows collecting


qualitative information about the wind velocity field in correspondence


passengers. An example of this activity is showed in Figure 15.


6. REFERENCES 1. LEWIS E. V., ‘Air and wind resistance’ Par


5.2, pp. 29-34, Principles of naval Architecture, Second Revision, SNAME, Jersey City NJ, 1988


2. HUGHES G, ‘Model Experiments on the Wind Resistance of Ships’, Trans. INA, Vol. 72, 1930


3. HUGHES G, ‘The Air Resistance of Ships’ Hulls with Various Types and Distributions of Superstructure’, Trans. IESS, 1932


4. BAKER G.S., ‘Ship Efficiency and Economy’, 1942


5. SAUNDERS H.E., Hydrodynamics in Ship Design, Three Volumes, New York, SNAME, 1957


6. 7.


ISHERWOOD, R.M., ‘Wind resistance of Merchant Ships’, Trans RINA Vol 115, UK, 1973


FUJIWARA T., UENO M., NIMURA T., ‘An estimation method of wind forces and moments acting on ships’, Proceedings of the Mini- Symposium on Prediction of Ship Manoeuvring Performance, pp.83-92, 18 Oct. 2001


Figure 15: smoke visualisations 5.


CONCLUDING REMARKS


In this paper the experimental methodologies developed at Politecnico di Milano Wind Tunnel in order to assess mega-yacht aerodynamics in terms of aerodynamic loads, comfort analysis, pollutants dilution and re-ingestion analysis


using wind tunnel tests are described. With


reference to a 270’ LOA mega-yacht designed and built by Azimut-Benetti- boatyard, previously reported as an


© 2014: The Royal Institution of Naval Architects


8. FUJIWARA T., UENO M., IKEDA Y., ‘Cruising Performance of a large passenger ship in heavy sea’, Proceedings of the Sixteenth International Offshore and Polar Engineering Conference, pp. 304-311, The International Society of Offshore and Polar Engineers, 2006


9. HADDARA, M.R., GUEDES SOARES, C., ‘Wind Loads on Marine Structures’ Marine Structures 12:199-209, 1999


10. KOOP, A., ROSSIN, B., VAZ, G., ‘Predicting Wind Loads on Typical Offshore Vessels Using CFD, Proceedings of ASME 31th International


open areas occupied by example, many data useful for the design and


construction of the yacht, have been obtained by the wind tunnel tests.


Aerodynamic loads measurements allowed a better understanding of


the added resistance given by the


superstructures, and are a basis for the DPS performance simulation. The results of this simulation are in the form of a capability polar plot, which shows, for each wind angle, the maximum wind force that the system can withstand keeping position and heading.


Speed-up measures have been useful to identify the most critical areas, and to decide, together with the designer, the position and layout of the windscreen or glass doors.


Thanks to the exhausts dilution test, the position of the exhaust


outlets has been chosen from two options,


avoiding potential problems which could not be easily solved at a later stage, and the layout of the HVAC grids could be confirmed, as the pollutant concentrations were negligible in all conditions.


B-79


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