No. 2 • Aug • 2014 · No. 2 • Aug • 2014 5 above about 79 degrees north. In these...

No. 2 • Aug • 2014

Norwegian Marine Technology Research Institute

ISSN 0801-1818

CON

TEN

TS

MA

RIT

IME

Reliable prediction of bollard- and tow-pull characteristics of AHTS

Manoeuvrability and minimum required power under adverse condi-tions

Internet at sea: Does it work?

The autonomous ship – where does it go?

Hybrid Power Laboratory at MARINTEK

1 4

6

3

8

Reliable prediction of bollard- and tow-pull characteristics of AHTS>> Senior Research Scientist Egil Jullumstrø>> Research Scientist Ørjan Selvik

Photo: Ulstein

MARINTEK is parti cipati ng in a development pro-gramme initi ated by Ulstein Design & Soluti ons AS, which focuses on the bollard- and tow-pull character-isti cs of anchor-handling tug supply vessels (AHTS), specifi cally, a large tug design. The programme is evaluati ng the following topics:• Propeller/duct performance• Interacti on hull-propulsion system• Eff ect of speed• Propulsion unit performance in waves

A large matrix of propeller/duct combinati ons has been stud-ied, followed up by open-water tests, propulsion tests (free speed), bollard-pull and tow-pull tests.

Interacti on between the hull and the propulsion system are very important for high-powered ships as described here. The thrust deducti on factor depends on hull and skeg clear-ance to the duct/propeller, brackets, tunnel thrusters and other appendages, and fi nally on the total wake and the pressure distributi on on the duct.

Cont. on page 2

REVIEW

2

Calm-water tests at forward speed documented that the pull is gradually reduced as forward speed increases. This eff ect is not surprising, and two factors are involved here. The fi rst is that resistance rises with increasing speed. Secondly, thrust and torque decrease with increasing speed; i.e. propeller loading is reduced.

Performance in waves was investi gated for diff erent speeds, irregular wave conditi ons and in head and following seas. Air sucti on to ducts and propellers can reduce pull in calm water to a certain extent, while in waves, losses due to air sucti on are more pronounced. Losses are also generated by the fact that propellers and ducts are moving in the actual wave fi eld.

Air sucti on is clearly dependent upon wave length, wave encounter frequency, heading and vessel speed. As the fi gure shows, the average thrust is signifi cantly reduced when severe sucti on occurs.

These development studies have provided new insight into tug propulsion performance. More knowledge is sti ll needed regarding the correlati on between model predicti ons and full-scale performance, and this will be the subject of further investi gati ons.

Example: Measurements in head seas, bollard pull.

Reliable prediction ....Cont. from page 1

Example: One set of propellers, rudders and ducts.

MARINTEK’s vessel simulator VeSim is under conti nuous development e.g. within the framework of the ongoing research project SimVal (Sea Trials and Model Tests for Validati on of Shiphandling Simulati on Models, funded by the Research Council of Norway) and the Rolls-Royce University Technology Centre (UTC) Performance in a Seaway. Further important work on manoeuvrability in adverse conditi ons is being carried out at MARINTEK as part of the ongoing research project SHOPERA (funded by the European Union within the Seventh Framework Program under agreement SCP2-GA-2012-314534), where the goal is to develop propos-als for improved regulati ons that will ensure both safe and environmentally friendly ship operati on.

Manoeuvrability and ....Cont. from page 3

No. 2 • Aug • 2014

3

Manoeuvrability and minimum required power under adverse conditions>> Research Scientist Florian Sprenger >> Research Scientist Ørjan Selvik >> Research Manager Dariusz Fathi >> Research Scientist Edvard Ringen

Example of the capabiliti es of VeSim: Power loss due to a venti lati on event observed during model tests (top) and simulati ons (bott om) in irregular waves (Hs=5.3m, Tp=9.7s).

MARINTEK’s vessel simulator VeSim off ers unique opportuniti es to assess manoeuvrability and minimum required power to advance in head seas as early as at the design stage, in order to ensure that the vessel sati sfi es current IMO regulati ons.

Since January 2013, all new-builds and vessels that have undergone a major conversion have to fulfi l the require-ments of MARPOL Annex VI, which defi nes reference lines in terms of an Energy Effi ciency Design Index (EEDI). This index is an indicator of the vessel emissions, given in grams-CO2/tonne-mile, and its implementati on in the IMO regulati ons is intended to be a step towards ‘green shipping’.

One way to meet the EEDI is to reduce installed power, which reduces the powering margin and may lead to signifi cant safety issues for certain types of ship, since their manoeuv-ring capabiliti es in adverse conditi ons may no longer be suffi -cient. In order to ensure safe operati on in adverse conditi ons, the interim resoluti on MEPC.232(65) was released by the IMO in 2013, but so far it covers only tankers and bulkers.

It is obvious that more detailed investi gati ons in t his fi eld are required to ensure that shipping is both green and safe.

Full-scale trials to systemati cally assess vessel performance in adverse conditi ons are hardly possible, while model testi ng is ti me-consuming and expensive. The development of reliable sophisti cated numerical tools such as MARINTEK’s vessel simulator soft ware VeSim is therefore extremely important. VeSim is an effi cient ti me-domain simulator based on Fossen’s unifi ed model for seakeeping and manoeuvering. It takes into account environmental forces from wind, waves and currents as well as forces from the propulsion system, including loss eff ects, e.g. due to propeller venti lati on. Since both hydrody-namic coeffi cients and manoeuvring properti es are precalcu-lated by the plugins VERES (VEssel RESponses) and HullVisc to MARINTEK’s soft ware workbench ShipX, the actual ti me-domain simulati ons can be performed very effi ciently.

While the calm water IMO criteria regarding the turning and course keeping ability are so far not defi ned in adverse condi-ti ons, there is a clear defi niti on of the minimum advance speed in head wind and waves in the interim IMO resoluti on MEPC.232(65). This speed is the greater of the minimum navigati onal speed of 4.0 kn and the minimum course keep-ing speed, which is a functi on of the rudder area and the ves-sel’s windage area. VeSim can be effi ciently applied to assess this criterion for any vessel.

Cont. on page 2

REVIEW

4

For several years, MARINTEK has been involved in a number of projects that investi gate the quality of service provided by various types of broadband com-municati on at sea. The MARENOR project1 is currently contributi ng the most concrete results to these studies.

Satellite communicati on and positi oning systems use diff er-ent frequencies, as shown in the table below.

Band GHz ServicesL 1-2 GNSS, Inmarsat C/Fleet, Iridium

C 4-8 Some VSAT systems, e.g. Sea Tel Inc.

Ku 12-18 Most VSAT systems

Ka 26.5-40 Newer VSAT systems, Inmarsat Global Xpress

In general, higher frequencies off er more bandwidth, but are more suscepti ble to atmospheric att enuati on, which may lead to loss of connecti on or transmission delays. This is normally expected to apply mainly to Ka and Ku band transmissions. Our studies have focused on Iridium and VSAT over Ku, as these are oft en used to provide communicati on services in the North-Atlanti c. Iridium is typically used as backup as it has a relati vely limited bandwidth (134 kilobits per second), but has world-wide coverage – including the Arcti c. VSAT can normally supply much higher bandwidth, but this is dependent on the subscripti on type used and the user’s willingness to pay.

MARENOR Measurement campaign

The MARENOR project has installed a measurement system on several ships that operate in diff erent parts of the world, but with emphasis on the Arcti c. The system measures round-trip ti mes (RTT) for short and long data messages over a typi-

cal Internet link and as the user experiences it. For short messages (around 100 bytes), a measure-ment is done each 5 minutes. The investi ga-ti on shows that the data links are relati vely stable and well suited for most applicati ons. However, certain limits to service quality need to be taken into account for some applicati ons.

VSAT data has been col-lected in the area indicated on the Google Earth (above), between 78 and 69 degrees north and between 11 and 20 degrees west. Iridium data has been collected from a stati on located on ground, close to Longyearbyen (78°13ʹN 15°33ʹE).

This area has good coverage of both Iridium and VSAT and our currently available data provide litt le evidence that lati tude has a strong infl uence on RTT in this area for either system.

Some measurement results

Measurements have been done on an Iridium data link (Iridium Pilot) and a commercial VSAT service over Ku band. In this arti cle we report on data that was collected between 21st April and 31st May 2014. This period was selected in order to maximise data for VSAT, as the ship containing the measurement system moves in and out of the coverage region for the satellite quite oft en. The results are summa-rised in the table below. The diff erence in the total number of messages is due to the complete loss of VSAT connecti on when the ship moves

Internet at sea: Does it work?>> Research Director Ørnulf Rødseth

1 See htt p://www.sintef.no/Projectweb/MARENOR/

No. 2 • Aug • 2014

5

above about 79 degrees north. In these measurements, data from positi ons north of 78 degrees have been removed for the VSAT connecti on, as these are infl uenced by the satellite coming and going out of the ship’s line of vision. Below 78 degrees there is no discernible correlati on between lati tude and VSAT performance in these measurements. The Iridium test stati on is stati onary, but other measurements show no signifi cant correlati on between lati tude and performance.

The expected RTT (E) represents a best fi t mean value to the distributi on of 90% of the messages. This is the round-trip ti me that the user would expect in most communicati ons. As can be seen, the expected RTT for Iridium is twice as long as for VSAT. The distributi on of messages with much longer RTT than E is also diff erent between VSAT and Iridium: Iridium has a much higher percentage of messages with very long RTT.

Connecti on losses in the data link in our experiment occur when a message is delayed more than 300 to 500 seconds. Connecti on losses also occur with VSAT, but these are always associated with the ship moving north beyond 78-79 degrees. They are therefore probably due to losing sight of the geostati onary satellite. As the table shows, Iridium has connecti on losses that are more random in nature and which occur relati vely frequently. Some of these breaks are also of substanti al length.

Some consequences for Internet users at sea

The analyses of the measurements reported on here are not complete as we do not have space to include all details, and

also because the project has not yet been completed. Some of the results may therefore be changed in future publica-ti ons. There are also other important fi ndings that we cannot discuss in detail at this stage. However, the data do represent the general impression of our experiences with satellite com-municati on in the high north:

• Iridium is functi onal in all areas, but there are a relati vely high degree of very long RTTs and breaks in connecti on that must be taken into considerati on when operati ons are being planned.

• VSAT off er lower RTTs than Iridium, but there is obviously a trade-off between geographic availability and speed.

• There are signifi cant variati ons in RTT that must to be taken into considerati on when operati ons are being planned. Fast closed-loop control may not always be pos-sible via a satellite link.

• These variati ons have litt le impact on large fi le transfers, except that in relati vely rare cases (once or twice a day for Iridium) transfers will be interrupted if the connecti on is lost.

• There are also some asymmetric properti es of Iridium that causes longer RTT in certain cases, e.g. when starti ng up transmissions aft er an idle period and when starti ng the transmission from an Internet node rather than from an Iridium terminal.

This is only a small selecti on of the results of the analysis and there are also other operati onal characteristi cs of both sys-tems that may cause problems in special operati onal setti ngs that we have not reported on here. However, one conclusion is that although satellite communicati on is becoming more reliable and more widely available, its characteristi cs need to be well understood to use data links eff ecti vely and safely in practi cal applicati ons.

The MARENOR Project

The MARENOR project is studying the performance of satellite-based mariti me navigati on and radio communica-ti on systems in the High North. The durati on of the project is February 2012 unti l February 2015.

Photo: Shutt erstock

Measurement Iridium VSATTotal number of messages measured 11297 3532

Expected RTT (seconds) – E (see note) 1.4 0.7

Percentage message with RTT > 2E 11.3% 14.0%





Connecti on breaks < 400E (see note) 62 0

Connecti on breaks > 400E 56 0

REVIEW

6

MARINTEK is technical coordinator in the European research and development project MUNIN1, which will perform a feasibility study on an unmanned merchant ship, using a Handymax dry bulker as case. This arti cle provides an overview of the background and some results of the project. In parti cular, we want to look at the potenti al applicati ons of the technology involved and make some guesses at what could develop in the future.

“Autonomous” does not necessarily mean the same as “unmanned”. A ship may have some form of “intelligence” to be able to operate without full crew att enti on for some ti me, without actually being unmanned.

The strategic basis for autonomous shipsShipping, shipbuilding and related areas make up an impor-tant sector of the European economy. It is also a strategically important societal functi on as about 80% of Europe’s imports and exports are transported by sea. To cover the industrial interests, the European Mariti me Industries Forum (MIF) has taken the initi ati ve to develop the “Waterborne Technology Platf orm”2, which includes a strategic research agenda. The autonomous ship had a prominent place in the original strat-egy, although in later versions it has been changed to “partly autonomous” ships. We will return to this later in this arti cle.In general, Europe is meeti ng strong competi ti on in areas where labour costs are an issue. This has already led to a high degree of automati on and a dramati c reducti on in the size of ship crews. However, there may sti ll be effi ciency and safety gains to be had by further automati on, although the com-pletely unmanned ship may not be the best soluti on. More automati on could help to strengthen the European deep-sea shipping industry and even increase Europe’s share of this strategically important business.

Making European shipping more att racti ve to mariners and thereby maintaining local experti se is also important for land-based industry. Access to expert knowledge on operati ons and vessel maintenance is vital to competi ti ve shipbuilding, equipment and marine operati ons industries.

The legal basisLegislati on and internati onal rules will obviously be a problem for unmanned ships, as will insurance and general

confi dence. However, where legislati on is concerned, there are already two cases that are relati vely easy to handle:

• Unmanned operati on only in internati onal waters, which is the case in the MUNIN project. In principle, this would only require the approval of the fl ag state. This soluti on would require crew to be on board during passage in nati onal waters.

• Unmanned operati on only in nati onal waters, e.g. short-sea shipping or supply services in the off shore industry. In this case the coastal, port and fl ag state would be one and the same and approval of operati on would be up to this state alone.

To allow operati on in internati onal traffi c more generally, where ports in diff erent countries are called on, internati onal legislati on would need to be harmonised.

The commercial trust will have to be gained by proper docu-mentati on of safety and reliability.

Piracy and hijackingThis could be a problem for completely unmanned ships, as there is no crew onboard to prevent hijackers or pirates from boarding. However, the ship will also be less att racti ve to pirates, as ransoming the crew is normally their main objec-ti ve. One can also take technical measures to hinder unau-thorized people from operati ng the ship. Electronic control of propulsion machinery is relati vely simple to implement. Tracking the ship by AIS satellite or other means also makes recovery possible.

The autonomous ship – where does it go?>> Research Director Ørnulf Rødseth

1 htt p://www.unmanned-ship.org/ 2 htt p://www.waterborne-tp.org/

No. 2 • Aug • 2014

7

There are also security issues related to communicati on and positi oning systems. Satellite systems rely on very weak sig-nals that are easy to fake or jam. Full remote control of a ship on autopilot by spoofi ng GPS signals has already been dem-onstrated. While it is diffi cult to safeguard against jamming, spoofi ng can be avoided by using additi onal ship sensors to validate data input. Communicati on will need to use strong encrypti on to avoid intercepti on or faking.

Cost reduction as a driving factor?

When the MUNIN project was conceived, cost reducti on through less crew was one argument for investi gati ng the subject. Crewing costs are parti cularly signifi cant on slow or ultra-slow steaming on long voyages. More detailed studies have shown that direct reducti ons in crewing costs will prob-ably not be a factor in considering the use of autonomous ships. Additi onal equipment, higher fuel quality and the cost of operati ng a shore control centre will off set many of the savings.

Many tasks such as cargo hold cleaning, machinery mainte-nance and ship and paint repair need to be done on ships during voyage as part of regular operati on and upkeep. These tasks cannot easily be automated and may make it diffi cult to realise the concept of the completely unmanned ship, at least for longer voyages.

On the other hand, slow and ultra-slow steaming place a signifi cant burden on the crew, since they are confi ned to the ship for up to four weeks at a ti me, with limited Internet and family access while doing three-shift watches throughout the voyage. Such considerati ons will certainly make it diffi cult to att ract people to the job.

Automated watch-keeping and steering at night and shore control centres will allow working shift s to be reduced to a single dayti me watch. At night, the crew would only be called when the control centre is unable to handle a situa-ti on remotely. Shore control will also require higher capacity Internet, which would also be available to the crew when not in use for vessel operati on. The crew would also work together during the single shift , giving them more free ti me together, which would greatly improve working conditi ons.

Cost savings in this scenario would come from lower fuel consumpti on and to a lesser degree from crewing reducti ons.

Improved technical systems

Autonomous ships will require much improved technical systems, mainly for watch-keeping and steering, but also to improve the monitoring and maintenance of technical systems. This will reduce costs related to off -hire and damage to ship and cargo. Exactly how the fi gures add up will be investi gated in the coming year, when the main cost-benefi t analysis for MUNIN will be performed.

Other types of autonomous ships

In the longer term, completely unmanned ships will probably appear on certain long voyages, mainly with dry cargoes. This would require more purpose-built systems onboard with much more emphasis on operati on without conti nuous care and maintenance. Our esti mate is that around 3500 ships could be in this category, which is 7% of the internati onal fl eet. These ships would have an ordinary crew onboard for entering and leaving port.

Another possibility would be supply services to off shore installati ons, where the ships operate in nati onal waters, thus reducing legal problems. High capacity and reliable wireless communicati on will be available near the shore base and around the installati ons to allow direct remote control of ves-sels during the most criti cal parts of the voyage. The number of ships in this category is also limited. Around 1000 ships worldwide would be candidates for this soluti on.

Impact on the maritime profession

The number of crew aff ected by autonomous shipping will be limited. On the other hand, the new job positi ons and the new work environment created by autonomous ships will att ract more people to the mariti me profession. For Europe at least, this may well create an environment capable of recruiti ng more mariti me professionals who can also assume management and supervision positi ons on shore. This will help to stop the movement of the deep-sea shipping industry to the Far East, where it is currently easier to obtain experi-enced personnel.

Relation to e-Navigation

The IMO e-Navigati on acti vity has fi nalised its strategic imple-mentati on plan. Autonomy in shipping is closely related to many of the objecti ves in the plan, parti cularly those related to bett er integrati on of acti viti es between ship and shore. Applicati ons at the interface between e-Navigati on and autonomy primarily concern more advanced traffi c manage-ment systems. Several projects in this area are also under way and we can expect to see an interesti ng cross-ferti lisa-ti on between these initi ati ves.

© Thomas Porathe

Otto Nielsens veg 10, P.O.Box 4125 Valentinlyst NO-7450 Trondheim, Norway

Phone: +47 464 15 000 Fax: +47 7359 5776E-mail: [email protected] www.marintek.no

Norwegian Marine Technology Research Institute

Ørnulf RødsethResearch director

Phone: +930 94 401E-mail: [email protected]

AuthorsEgil JullumstrøSenior research scientist

Phone: +47 991 54 905E-mail: [email protected]

Ørjan SelvikResearch scientist


Florian SprengerResearch scientist


Dariusz FathiResearch manager


Edvard RingenResearch scientist


A hybrid test facility, made feasible by cooperati on between ABB, MARINTEK and NTNU, is now operati ve in MARINTEK’s Energy Laboratory.

Hybrid Power Laboratory at MARINTEK>> Senior Research Engineer Erik Hennie

Figure 1. Hybrid facility

Figure 2. Some of the facility’s main components: diesel generator sets, load units, recti fi ers and drive line-up

The facility comprises:• diesel engines connected to variable-speed generators• recti fi ers • multi drive DC lineup (with inverters and transformers)• electro motors, connected to a eddy current brakes• capacitor bank• batt ery bank• control and management system.

A schemati c overview is shown in Figure 1, while Figure 2 illustrates some of the main components of the facility.

The set-up is capable of simulati ng real-life operati ng profi les, e.g. typical OSV profi les. Advanced power management

Erik HennieSenior research engineer


systems and control algorithms will be developed and tested, and by uti lising all available opti ons and operati onal fl ex-ibility, the potenti al for fuel savings and reducing emissions will be shown. The test facility will also be a useful tool for educati onal and PhD projects.

No. 2 • Aug • 2014 · No. 2 • Aug • 2014 5 above about 79 degrees north. In these...

Documents

Transcript of No. 2 • Aug • 2014 · No. 2 • Aug • 2014 5 above about 79 degrees north. In these...