Full Scale Measurements- Sea Trials

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Full Scale MeasurementsSea trials

Experimental Methods in Marine Hydrodynamics

Lecture in week 45 Contents:

Types of tests

How to perform and correct speed trials

Wave monitoring

Measurement

Observations

Motion measurement

Hull monitoring

Propeller cavitation observations

Performance monitoring

Covers Chapter 11 in the Lecture Notes


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Dedicated sea trials are conducted under the

following circumstances:

Delivery of newbuildings (Contractual Trials)

Speed-power (compliance with contracted performance)

Bollard Pull test (tugs and offshore vesselscompliance with

contracted performance) Maneuvering (compliance with IMO criteria)

Sea keeping (only high speed craft)

If a special problem has arisen, for instance:

Propeller noise and/or erosion

Steering problems

Excessive fuel consumption

For research purposes (quite rare due to high costs)


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Delivery Sea trials (Contractual trials)

Ship building contracts contain specific requirements for

speed-power performance

Failure to meet requirements means fees to be paid and ultimately

that the ship owner has the right to refuse to accept the ship

For tugs and offshore vessels, there will be requirements

for bollard pull as well

There might be requirements also for maneuvering trials :

Emergency stop test Turning circles

Zig-zag tests

High speed craftrequirements also for seakeeping tests

IMO: 2000 HSC Code (IMO 185E)


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Applicable standards

ISO 19019:2005 Sea-going vessels and marine technology --

Instructions for planning, carrying out and reporting sea

trials

ISO 15016:2015(E) Guidelines for the assessment of speedand power performance by analysis of speed trial data

Replaced previous version in 2015. Significant differences!

ITTC Recommended procedure 7.5-04-01-01.1 Preparation

and Conduct of Speed/Power Trials IMO: 2000 HSC Code (IMO 185E)Requirements for

testing of high speed craft


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IMO HSC testing requirements

Stopping

Normal stop from max speed to zero

Emergency stop

Crash stop

Cruise performance in two sea states

Normal conditions

Worst intended conditions

Measurements of accelerations, speed, relative wave heading

Failure tests

Check that the ship, crew and passengers are not at risk if forinstance the steering fails


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Organization of Delivery Trials

The Shipbuilder is responsible

Trial Leader From the shipbuilder

Responsible for the execution of all phases of the trial

Ship masters

There is one ship master hired by the shipbuilder who is in chargeof handling the ship

There is usually one or more ship masters hired by the shipownerwho is going to take over the ship

Measurements are performed by shipbuilder or by thirdparty (like Marintek or Maskindynamikk)


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Execution of speed trials

Always run back and forth at same engine setting

Run back and forth at the same track

Perform runs at different speeds (at least three)

If possible, orient the track with and against the winddirection

Steady Approach

> 5 min and 1 mile

Steady Approach

> 5 min and 1 mile

Wind, current


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Measured mile


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Trial Conditionsmax acceptable

Sea state

Preferably sea state 3

Ultimately sea state 5 (or up to sea state 6 for ships with L>100 m)

Wind Beufort 6 (20 knots) (for ships with L>100 m)

Beufort 5 (for ships with L 100 m)

Water depth h

h>6.0*Am2

and h>V

2

Smaller depths require corrections for shallow water

Current

Current of more than a few knots is unacceptable


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Trial ConditionsContractual

Sea state

No waves

In practice: Beufort 1 (Wave height 0.1 m)

Wind No wind

In practice: Beufort 2 (Wind speed 6 knots)

Water depth h

Deep,

In practice: h>6.0*(Am) and h>V2

Current

No current

No practical limit for when corrections are made. Use of double runs

means that corrections are always included


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Correction of trial results

When trial conditions are not fulfilled corrections must bemade

Typical corrections:

Draughtinterpolation in model test results on two draughts Windcalculation of wind resistance using empirical drag coef. or

results from wind tunnel tests

Shallow waterempirical formulas

Wavescalculation of added wave resistance and speed loss

Standards for how corrections shall be performed: ISO 15016 Guidelines for the assessment of speed and power

ITTC Procedure for the Analysis of Speed/Power Trial Data

STAWAVE by Marin

Comes with a free software package for performing the analysis


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IMO Energy Efficiency Design Index -

EEDI Increases the need for standardized trial and correction

procedures

The speed at 75% MCR in calm water must be accurately

determined

Now longer just a matter for yard and ship owner

Shall be approved by classification society


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Recent developments

The ISO 15016 is about to be discarded

Too complicated to use

Too much freedom to manipulate results

Outdated correction methods

IMO has tasked ITTC to develop a new standard

ITTC works with Marin, and the new guideline is based on

the STAWAVE methods


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Speed measurement

Speed over ground and Speed through water

Timing a measured mile

the old-fashioned way, only applicable to dedicated speed trials

Gives speed over ground

GPS

The obvious choice, always used

Gives speed over ground

Speed log

Device to measure speed through water

Always installed on ships

Doppler log is most common on large ships

Measures speed at about 10 m below bottom, close to bow

The accuracy is questionable!


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Measurement of shaft power

Strain gauges glued directly to the shaft

Calibration factor must be calculated, so shaft dimensions and

material properties must be known exactly

Tachometer to measure shaft speed

Commercial power meters

Made for permanent installation The best, but most expensive alternative

Poor, but cheap alternatives are

fuel rack measurements (measurement of fuel consumption,

combined with supplier data for fuel quality) measurement of cylinder pressure (used on large, slow speed

engines)

For diesel-electric drive-trains, the frequency converter (drive)

will usually be able to output information about power supplied to

the electric motor


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Shaft measurements

Torque measurement Thrust measurem.


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Optical torque sensor


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Optical thrust and torque measurement

Required accuracy for thrust measurement is

25 naonometers!Challenging, but possible, according to

supplier VAF Instruments


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Bollard Pull

Tests

Good location Poor location


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Bollard pull test


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Bollard pull test

2x460 kW


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Maneuvering trials

Trial types and execution same as in model scale

Measurements:

(D)GPS position measurement

Gyro compass course

Rate of turn (if possible)

Rudder angle

Propeller revs


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Types of Ship Maneuvers

IMO standard maneuvers:

Zig-zag tests

10/ 10 to both sides

20/ 20 to both sides

Turning circle test

35 rudder angle

Full astern stopping test

Additional maneuvers:

Spiral test Reverse spiral test

Pull-out maneuver

normally added at the end of a turning test


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Zig-zag test

i


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Test 2011: 20-20 zig zag


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Turning circle


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Testing of position-keeping ability and

thruster performance at zero speed

Important for vessels that have requirements to Dynamic

Positioning performance

No standard tests or commonly recognised procedures

There is a need for development of standardized tests and analysis

procedures for this purpose

A way to characterise thruster performance at zero speed:

Run the thrusters in different combinations (one by one, and in

specific combination) for a short time Measure the acceleration of the ship in the horisontal plane

Compute the impulse required to create the acceleration

Compare the effective impulse with the impulse provided by the

thruster(s) to arrive at a kind of efficiency


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Measurementsenvironmental conditions

Water depth

Echo sounder (ship instrument) or nautical charts

Water quality

Temperature: Cooling water intake temperature can be used

Density: From nautical charts or density measurements

Wind Velocity and direction from anemometer

A separate, calibrated instrument is preferable

Watch out for influence of superstructure on the measurement

Current

Nautical charts and tables

the difference in speed between double runs

a 360 turning test at low speed

The difference between log speed and GPS speed

often, one doesnt trust the speed log sufficiently for this purpose


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Wave measurements

Visual observation and estimation

Estimates by yard representative, ship-owner representative, and

possibly a neutral third party are compared and averaged

Mobile wave buoy Accurate (but only at a single point)

Recovery of the buoy is difficult (risk of loosing it)

Fixed weather station

Good solution if one is nearby

Wave radar (Wavex)

Bow-mounted altimeter

Wave information without measurement: Hindcast data


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Wave buoys

Fugro Oceanor Wavescan

Directional wave spectrum

Wind

Current

Water temperature and salinity

Must be moored; large, heavy, costly Smaller, spherical buoys

Drifting or moored

Simple buoys measure wave height only by use

of an accelerometer

Advanced buoys can measure the directional

wave spectrum through use of the Doppler shift

of the GPS signals

Usually measures positionfor a drifting buoy

this can be used as an estimate of current

Can be brought along for a full scale test
http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=aMG0sltdNOuyxM&tbnid=UVcwN3lXp4O-tM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.channelcoast.org%2Fsouthwest%2Fsurvey_techniques%2Fwaves%2F%3Flink%3Dwave_measurement_at_nearshore_buoys.html&ei=KCJxUsuhOquZ0QX80YHABg&bvm=bv.55617003,d.ZGU&psig=AFQjCNFDWEg9vhfKhWgK0WWzZhpCGFy5Rw&ust=1383232384105471http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=aMG0sltdNOuyxM&tbnid=UVcwN3lXp4O-tM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.channelcoast.org%2Fsouthwest%2Fsurvey_techniques%2Fwaves%2F%3Flink%3Dwave_measurement_at_nearshore_buoys.html&ei=KCJxUsuhOquZ0QX80YHABg&bvm=bv.55617003,d.ZGU&psig=AFQjCNFDWEg9vhfKhWgK0WWzZhpCGFy5Rw&ust=1383232384105471


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Wavex by Miros AS


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Bow-mounted altimeter

Measures relative wave motion

Ship motions must also be measured

in order to calculate absolute wave

height

SM - 055

SM - 094


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Using the ship as wave buoy

Measurement of ship motions and accelerations

Knowledge of ship motion transfer functions can be used

to find the wave spectrum from the measured ship motion

power spectrum

Current research topic

Can hardly work for short waves, since then the ship

doesnt move


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Beufort wind scale with related sea conditions

Sea Description term Wind sp. [knots] Wave height [m]Beufort state Wind Wave min max Probable Max

0 0 Calm Calm 0 1 0 0

1 0 Light air Ripples 1 3 0.1 0.1

2 1 Light breeze Small wavelets 3 6 0.2 0.3

3 2 Gentle breeze Large wavelets 6 10 0.6 1

4 3 Moderate breeze Small waves 10 16 1 1.55 4 Fresh breeze Moderate waves 16 21 2 2.5

6 5 Strong breeze Large waves 21 27 3 4

7 6 Near gale Large waves 27 33 4 5.5

8 7 Gale Moderately high waves 33 40 6 7.5

9 8 Strong gale High waves 40 47 7 10

10 9 Storm Very high waves 47 55 9 12.5

11 9 Violent storm Exceptionally high waves 55 63 11.5 16

12 9 Hurricane Exceptionally high waves 63 71 14 16

13 9 Hurricane Exceptionally high waves 71 80 >14 >16

14 9 Hurricane Exceptionally high waves 80 89 >14 >16

15 9Hurricane Exceptionally high waves 89 99 >14 >16


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Illustrations of Beufort wind (and wave) scale

From: http://en.wikipedia.org/wiki/Beaufort_scale


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Hindcast data

Information about wave and wind condition in the past

Data collected by meteorological institutes

From wave buoys, weather stations, satellites, observations

Many different sources

Might be hard to find the right source for your test

National Oceanic and Athospheric Administration www.noaa.gov

is the main source

Many different applications are using their open data

From hindcast data you can get information about sea stateand wind in your area

You can of course not get wave elevation time series!

Generally only available for open ocean areas
http://www.noaa.gov/http://www.noaa.gov/


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Measurement of motions

Accelerations: Conventional accelerometers

Angles: Gyros, compass, accelerometers

Rate gyro to measure rate of change of angles

Inertial Measurement Units (IMU)

Consists of a number of accelerometers built into one compact unit

Gives out accelerations, velocities and motions at any point

Konsberg Seatex MRU is a good example of a commercial IMU

Kongsberg Seapath

Combination of DGPS and IMUfor accurate position

measurement


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Kongsberg Seatex MRU 5+


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Kongsberg Seapath 330


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Measurement of forces:

Hull Monitoring

Strain gauges most

common sensor

Short and long gauges

Cabling exposed todamage, gauges work

loose

Sensors based on fiber-

optics - polarimetric and

bragg-grating suggested as

alternative

Hull Monitoring System:

Strain gauge in protective casing:

R ll R H lth d M it i


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Rolls-Royce Health and Monitoring

System - HEMOS


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Example: Monitoring of loads

on an azimuthing thruster of a

seismic vessel

Measurement of ship motions andposition with Seapath

Measurements on the portazimuthing thruster

Automatic triggering of data storage

Data acquisition system remotelymonitored from land


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Performance monitoring

Typical merchant ship application:

To monitor the development of speed and fuel consumption

over time, in order to detect need for maintenance

Challenges:

Monitoring and correcting for environmental conditions

Waves, wind, water temperature

Accurate measurement of shaft power and speed through water

Measuring and correcting for loading condition Data processing

Setting-up and running automatic data transmission


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Propeller Cavitation

Observations

Seen from below Seen from the side


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Cavitation observation techniques

1. generation borescope

2. generation borescope

Source: marin.nl


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Documents

Full Scale Measurements- Sea Trials