245mi - architettura navale
TRANSCRIPT
245MI - Architettura NavaleA.A. 2020/21
Introduction
Docente: Prof. Mitja MorgutUniversità degli Studi di TriesteDipartimento di Ingegneria e ArchitetturaVia A. Valerio 10, 34127 TriesteEdificio C5 - Stanza C5_2.44mail: [email protected]
Resistance prediction Classification on marine vessels Calm Water
Why resistance predictions are important
Architettura Navale, A.A. 2020/21
When a new ship is ordered, a contract containing a specification of the ship is signedÏ One of the most strict specifications is the contract speed i.e. the speed reached
at a specific power consumption in a trial run before delivery.Ï The trial run carried out to certify the contract speed is supposed to take place
under ideal conditions.
For a successful ship design, it is fundamental to accurately predict the powernecessary to achieve the desired/expected speed
Ï Due to a strong competition between shipyards the offer must be at least as goodas that of the competitors.A few percent higher power for a given speed can lead in a lost of order.
Ï On the other hand, if the prediction is performed in too optimistic fashion and onthe trial day the ship does not reach the expected speed, the customer mighteven refuse the ship.
The difficulty of this task is augmented by the fact that reliable information regardinghull shape, resistance and propulsion is required early in the design.The hull shape needs to be defined as soon as possible is since it affects not onlyresistance and propulsion, but also stability, structure.. of the vessel.
Resistance prediction Classification on marine vessels Calm Water
Why resistance predictions are important
Architettura Navale, A.A. 2020/21
When a new ship is ordered, a contract containing a specification of the ship is signedÏ One of the most strict specifications is the contract speed i.e. the speed reached
at a specific power consumption in a trial run before delivery.Ï The trial run carried out to certify the contract speed is supposed to take place
under ideal conditions.
For a successful ship design, it is fundamental to accurately predict the powernecessary to achieve the desired/expected speed
Ï Due to a strong competition between shipyards the offer must be at least as goodas that of the competitors.A few percent higher power for a given speed can lead in a lost of order.
Ï On the other hand, if the prediction is performed in too optimistic fashion and onthe trial day the ship does not reach the expected speed, the customer mighteven refuse the ship.
The difficulty of this task is augmented by the fact that reliable information regardinghull shape, resistance and propulsion is required early in the design.The hull shape needs to be defined as soon as possible is since it affects not onlyresistance and propulsion, but also stability, structure.. of the vessel.
Resistance prediction Classification on marine vessels Calm Water
Different ways to predict resistance
Architettura Navale, A.A. 2020/21
Three different methods are used at different stages of the design task
1) Empirical methodsÏ Employed in the initial design stageÏ Simple and rapid, but not always accurateÏ Usefull to identify the main particulars of the hull
2) Numerical methodsÏ Having an idea of the hull main dimensions, they may (are) employed to further
optimize of the shape of the hullÏ Time consuming, may require a significant amount of computational resourcesÏ Currently the CFD (Computational Fluid Dynamics) simulations are routinely
used
3) Model testsÏ Performed in the later stages of the designÏ Well established and arguably the most reliable performance prediction methodÏ Expensive but cheap compared to the cost of the shipÏ The model test data have to be extrapolated to full scale. This can introduce
significant errors if not done properly.
Resistance prediction Classification on marine vessels Calm Water
Classification based on the way the weight is supported
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
Surface piercing foils
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
Fully submerged foils
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
ACV - Air Cushion Vehicles
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
WIG - Wing in Ground (Craft)
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
WIG - Wing in Ground (Craft)
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
WIG - Wing in Ground (Craft)
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
Natural environment
Architettura Navale, A.A. 2020/21
Resistance prediction Classification on marine vessels Calm Water
Calm water
Architettura Navale, A.A. 2020/21