Webinar Trim Optimisation Specialized Vessels Nov 2015

7/23/2019 Webinar Trim Optimisation Specialized Vessels Nov 2015

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DNV GL 2015

SAFER, SMARTER, GREENERDNV GL 2015

Webinar 17 & 18 November 2015

MARITIME ADVISORY

Trim optimisation and its impact on specialized

vessels (OSVs & RoRos)

1 Webinar 17 & 18 November 2015

Trim optimisation and its impact on specialized vessels (OSVs & RoRos)

Heikki Hansen Fluid Engineering Department


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Trim optimisation and its impact on specialized vessels Webinar

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H e i k k i H a n s e n

Team Leader Fluid EngineeringProduct Manager ECO Assistant

Ph.D. (Mechanical Engineering) B.Eng. Yacht & Powercraft Design Joined GLs subsidiary FutureShip in

2009 after finishing his Ph.D. at TheUniversity of Auckland and working in

the yachting and automotive industry inthe fields of fluid dynamics andperformance modelling

Presenter


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Agenda

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A Why does trim optimisation lead to fuel savings?

Trim optimisation examples for specialized vessels

1. Car Carrier PCTC 5000

2. RoRo Vessel 7,500 DWT

3. Offshore Supply Vessel 5,500 DWT

4. Seismic Research Vessel 4,500 DWT

Conclusions

B

C




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Why does trim lead to fuel savings?


Background:

Many existing vesselsare hydrodynamically

optimised to produce low

resistance at their design

condition (design speed

and draft at even keel)

As soon as a vessel sails

outside of this condition

the flow field around the

vessel is less favourable

When changing trim the

interaction of vessel and

water (flow field)

changes and the

resistance may reduce

Rule of thumb: Trim potential increases the more distinct the underwater lines of a vessel

and the more it sails outside of its design conditions!



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Changing trim affects water flow and fuel consumption


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Car carrier example: speed 15kn, draft 7.5m



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Seismic OSV 91 000 USD annual savings per vessel

Data: 1 year AIS data (Transit mode)

Trim optimisation by DNV GL has been proven for all segments

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Case study selection

Source: DNV GL; client data; fuel price of 650 USD per mt

110 000 DWT Tanker 50 000 USD annual savings per vessel

Data: 2 years voyage reports; 8 ships

53 000 DWT Bulker 84 000 USD annual savings per vessel

Data: sea trial measurement

30 000 DWT MPV 170 000 USD annual savings per vessel

Data: performance measurement

8 750 TEU CV 420 000 USD annual savings per vessel

Data: 17 months including 53 voyages




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What is "Optimum trim"

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always aft down

always 1ft to stern (Greek style)

always 1ft to bow (German style)

always 2ft to stern (India style)

always level trim

1ft aft trim for better manoeuvrability level draft at discharge port for maximum cargo / least draft

by experience of better performance

drains in cargo holds

Captains shower drain




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Lack of knowledge on optimum trim typically leads to unnecessaryhigh fuel consumption

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53 voyages1 departure on optimum trim

Without trim optimization:

Clear gap between sailed andoptimum trim

Consequently savings

potential

Need for advice

Actual trim compared to optimum trim by ECO Assistant

14 sister vessels in same service

Where is theoptimum trim

Source: DNV GL; voyage records from client

-1,5

0,0

1,0

0,5

-0,5

-1,0

-2,0

-2,5

Trim [m]

Departure number

ECO Assistantoptimum trim

sailed trim

5350403020101




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Graph:Required power as a

function of trim and

draft

Red curve:Trim curve (required

power as a function of

trim) from one draft

Green dot:Optimum trim on this

trim curve

Blue surface:Trim surface (made

up of trim curves for

different drafts) for

one speed

Yellow curve:Optimum trim for

different drafts

Light blue surface:Trim surface for a

different speed

Yellow curve:Optimum trim for

second speed is

different to optimum

trim for first speed

For any given draft and speed, the optimum trim and relatedsavings change


Next >>Trim optimisation and its impact on specialized vessels (OSVs & RoRos)


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Finding the optimum trim goes beyond typical experience

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How to trim the vessel? In principal 3 trim options.

To stern? Even keel? To bow?

The challenge with trim:

Complex factors: speed,draft, water depth differentfor each vessel

Experience limited tofamiliar trim conditions, butthe optimum might bebeyond

Frequently changingand

off-design conditions likeslow steaming hardly fitinto rules of thumb

The solution:

Detailed analysisof allrelevant operationconditions

Make results available tocrew and management -easily

Source: DNV GL




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Can we do better?

Challenge: there is no unique optimum trim, but best trim is a function of hull

shape, propulsion system, speed, displacement and water depth

Solution: conduct CFD based trim optimisation for a range of operating conditions

and make results available to crew and ship operator through easy-to-use

software tool


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Parameter Range Data points

Speed 12 22 kn 8

Mean draft 9 14.5 m 7

Trim -3 4 m 7

392



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CFD based trim optimisation

Pre-computed computational fluid

dynamics (CFD) results for your specificvessel

Simulating a large number of conditions

with different speeds, displacements,

water depths1and trim angles

Extensive computational power needed

Results shown in a simple viewer with few

parameters only to be used onboard

before a voyage or at sea

No interfacing with ships sensors

required


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Trim Optimiser Fuel Calculator Reporting Interfacing


1. Optional service offering


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Agenda

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Conclusions

B

C




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No potentials at design condition



by stern Trim [m] by bow

Power savings potential [%]

Fuel savings potential [t/day]


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Slow steaming (16 kn) at design draft 1 t/day fuel savings




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Large bulbous bow, wide transom = significant savings potential




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Unfavorable bow wave observed in simulation and in real life


Trim = -0.0 m (level trim), slow steaming (16kn)



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Unfavorable bow wave


Trim = -0.0 m, slow steaming (16kn)



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Bow wave pattern improved 3.5% reduction in power


Trim = -0.9 m, slow steaming (16kn)



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Bow wave pattern further improved 5.5% reduction in power


Trim = -1.8 m, , slow steaming (16kn)



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Bow down trim improves bow wave and reduces power



Level trim -0.9m bow down -1.8m bow down

Unfavorable bow wave 3.5% power reduction 5.5% power reduction


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Ultra slow steaming (12.5 kn) at low drafts 2 t/day fuel savings




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Stern down trim improves bow wave pattern and reduces powerby up to 13%


Level trim



stern down trim

Improved bow wave pattern


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Summary

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Trim optimisation for Car Carrier

Car Carriers usually have a large potential for trim optimisation. This potential is

increasing with ships size, long sailing legs and operation away from design

condition (like slow steaming, part load or ballast voyages).

Large bulbous bows and wide transoms can have an unfavourable impact on

wave pattern and frictional resistance even for small changes in draft and whenslow steaming.

Moderate trim changes often result in significant fuel savings.




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Agenda

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Conclusions

B

C




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RoRo Vessel also shows little saving potential in design condition



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Speed 19kn

Little savings potential

Reducing ballast water

is beneficial


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RoRo Vessel also shows significant savings potential in off-designconditions



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Speed 15kn

Savings potential when

trimming bow down

1.0m bow down trim

saves 7%

Extra ballast water can

be taken on to achieve

forward trim With

550t extra ballast

(0.2m increase indraft) savings are still

5%


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Agenda

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Conclusions

B

C




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Trim of -0.66m by bow saves 4.5%



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Large savings potential at

design condition 11.6%

Savings still significant for

-0.66m trim by bow 4.5%


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Moderate trim

by bow t=-0.66m

power savings 4.5%

Moderate transomimmersion

Reduced transom immersion drives power savings in thisoperating condition



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Level trim t=0m

Optimum trim

by bow t=-2m

power savings 11.6%

Little transom immersionLarge transom immersion


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Level trim is most unfavorable: Bow down AND stern down trimreduce fuel consumption



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Optimum requires very large

bow down trim

Savings also for moderate trim

of +1.3m by stern 3.9%


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Moderate trim

by stern t=+1.3m

power savings 3.9%

Improved bow wave butincreased transom

immersion

Bow down and stern down trim improves bow wave; bow downtrim also reduces transom immersion



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Level trim t=0m

Optimum trim

by bow t=-2m

power savings 11.2%

Improved bow wave andreduced transom immersion



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Agenda

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Conclusions

B

C




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Trim optimisation saves Seismic Research Vessel 140t per year

For the trim range between 0.50m foreand aft savings between 7% and 12%can be achieved

Analysis of AIS data shows

Vessel in transit mode 15% of sailingtime

Vessel consumes 2,000 tons per yearin transit mode (80% of total FOC)

Annual saving based on 7%assumption is 140 tons fuel or 91,000USD1per ship

Very short payback time


0

200

400

600

800

Speed161050

FOC [t]

Transit modeSeismic

mode

1 Fuel price of 650 USD/mt (MDO)Source: Polarcus, DNV GL and AIS evaluation

Operational profile based on AIS data



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Many vessels operate away from their original

design condition

Trim optimisation has become important fuel

saving lever across the main vessel types

Many specialized vessels exhibit hull features

feature with make them trim sensitive

Even moderate trim changes can lead to

significant fuel savings

Organisational implementation and monitoring

are key factors to lift trim savings potentials

Conclusions



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SAFER, SMARTER, GREENER

www.dnvgl.com

For further information about trim optimisation please contact us:

[email protected]

Heikki Hansen

[email protected]


Thank you for your kind attention!

Documents

Webinar Trim Optimisation Specialized Vessels Nov 2015