An introduction to DHIs Mooring Analysis model content/presences/emea/uk/2016... · An introduction...
Transcript of An introduction to DHIs Mooring Analysis model content/presences/emea/uk/2016... · An introduction...
An introduction to DHIs Mooring Analysis model
Poul Kronborg
Product Area Owner, Marine MIKE Software Products
DHI
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1. Overview of Mooring analysis model and a preview of the coming
MIKE 21 Mooring Analysis (MA)
2. Model Validation
3. Example 1: Passing Vessel Induced Moored Vessel Motions
4. Example 2: Transshipment Terminal Operability
5. Questions
Agenda
01.
Overview of DHI
Mooring Analysis Software
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Moored Vessel Response Model
• Mooring Analysis model is under
active development
• Timeline of the model so far:
2011 – WAMSIM
2016 – DVRS
2017 – MIKE 21 MA
• MIKE 21 MA is still under
development, but examples of
the User Interface will be shown
Geographical coordinates for mooring system components
Irregular frequency filtering for single and multibody body systems
Greatly improved user interface
More accurate calculation of line and fender forces
Faster convergence to equilibrium position of the system
Improved temporal handling
Main developments in this phase
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Moored Vessel Modelling – MIKE 21 MA
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• MIKE 21 MA solves the equation of motion for the floating
vessel in all 6 degrees of freedom in the time domain
Applications:
Single Buoy Moorings
Passing Vessel Induced Vessel Response
Tandem Moored Vessels
Berth Operability/Downtime Analysis
Nearshore/Offshore Mooring Design
Floating Breakwaters / Wind Turbines
Moored Vessels Adjacent to Reflective Structures
Moored Vessels in Sheltered Areas
Accurate representation of vessel hull geometry and gyrostatic data.
Wave diffraction forces calculated from non-linear, non- uniform incident wave fields or flow fields produced by Mike21 and BW.
Implicitly resolves both bound and free long period waves in shallow water
Non-linear restoring forces due to mooring lines, fenders and posts
Frictional damping in the surge and roll modes due to scraping along a fender
Viscous surge and sway damping
Wind, current forces and 2nd order wave drift forces
Irregular frequency filtering for single body systems
Capabilities of MIKE 21 MA
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Overview of the M21MA Model
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Theoretical background for DVRS • FRC:
• Boundary element method code based on linear potential flow theory
• Solves radiation and diffraction problems in order to compute first order wave induced
frequency response functions of offshore structures (added mass, radiation damping,
exciting forces)
• Solves second order drift force frequency response functions based on momentum
conservation (far-field formula)
• MIKE 21 MA:
• Converts the frequency response functions from FRC to the mooring analysis simulation
time domain
• Calculates the exciting forces using Haskind relation from 2D (H,P,Q) or 0D (eta) wave
inputs
• Calculates second order drift forces from 2D (H,P,Q) or 0D (eta) wave inputs and FVRE
calculated drift force frequency response functions
• Calculates wind and current forces based on drag curves
• Calculates mooring forces based on force vs. deflection curves (line, fender)
• Uses the equation of motion for body dynamics to calculate the movement of the floating
bodies with the fourth order Runge-Kutta method
Placement in MIKE 21 In order to make it easier to find
this new implementation, we have
made a separate group under MIKE
21 called :
Maritime
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MIKE 21 Mooring Analysis (MA)
• Overall standard MIKE menu set-up
• Main items in menu tree:
• Material profiles
• Vessels
• Port Data
• Mooring Set-up
• Environmental Conditions
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MIKE 21 Mooring Analysis (MA): Material profiles
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MIKE 21 Mooring Analysis (MA): Vessels
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MIKE 21 Mooring Analysis (MA): Port Data
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MIKE 21 Mooring Analysis (MA): Mooring Setup
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MIKE 21 Mooring Analysis (MA): Mooring Setup
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MIKE 21 Mooring Analysis (MA): Mooring Setup
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MIKE 21 Mooring Analysis (MA): Mooring Setup
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MIKE 21 Mooring Analysis (MA): Mooring Line data
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MIKE 21 Mooring Analysis (MA): Environmental conditions
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MIKE 21 Mooring Analysis (MA): Output
Results – Cargo ship P2-class
No. of
lines Position
Initial set-up Optimised set-up
incl. shore tension
Max. force [kN] Max. force [kN]
1 stern line 221 153
2 stern line 223 157
3 aft spring line 258 203
4 aft spring line 251 199
5 fore spring line 258 175
6 fore spring line 291 170
7 bow line 173 150
8 bow line 172 150
9 aft breast line (with ST*) - 157
10 aft spring line (with ST*) - 183
11 fore spring line (with ST*) - 183
12 fore breast line (with ST*) - 114
OCIMF Recommendation :
• Wire: 55% MBL
• Synthetic ropes: 50% MBL
• Polyamide: 45% MBL
Here: 0.50*480 kN = 240 kN
Results – Mooring forces of further investigated vessel types
Ship type MBL [kN] Reduced MBL
[kN] Max. force [kN]
Percentage of
line usage
Cargo ship P2-class
(8 Lines) 480 240 291 121%
Cargo ship P2-class
(8 + 4 lines with st) 480 240 203 85%
Pontoon
(ballasted) 990 495 144 29%
Pontoon
(loaded) 990 495 280 57%
Jack-up ship 1
(initial set-up 6 lines) 512 230 263 114%
Jack-up ship 1
(6 lines + 2x spring
lines)
512 230 180 78%
Jack-up ship 2
(initial set-up 12 lines) 850 425 277 65%
Results - Motions of further investigated vessel types
Ship type Surge [m] Sway [m] Heave [m] Roll [°] Pitch [°] Yaw [°]
Cargo ship P2-class
(8 Lines) 4.49 0.06 0.40 1.62 0.19 0.16
Cargo ship P2-class
(8 + 4 lines with st) 2.72 0.05 0.40 0.60 0.19 0.14
Pontoon
(ballasted) 0.19 0.03 0.39 0.11 0.18 0.08
Pontoon
(loaded) 0.94 0.17 0.41 0.34 0.20 0.51
Jack-up ship 1
(initial set-up 6 lines) 2.40 0.12 0.40 0.21 0.21 0.40
Jack-up ship 1
(6 lines + 2x spring lines) 1.58 0.12 0.40 0.13 0.19 0.32
Jack-up ship 2
(initial set-up 12 lines) 0.94 0.17 0.39 0.22 0.20 0.14
02.
Model Validation
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Validation of DVRS – Port of Brisbane
Passing Vessel induced Moored vessel motions
• Passing Tanker – 46,900 m3
• Passing distance – 130m
• Passing speed – 8knots
• Line pre-tension – 10 tonnes
Scale Model
Numerical Model
Drawdown comparison
Measured (black) DVRS (blue)
Comparison of vessel motions
Measured (black) DVRS (blue)
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Square root of
surface elevation
spectra
(HS=4.91m, TP=11.0s at
offshore boundary)
Measured (blue)
WAMSIM (red)
Square root of vessel
motion spectra
Measured (blue)
WAMSIM (red)
• LNG Carrier
• 6 linear – elastic mooring
lines
• 2 linear – elastic fenders
• L – shaped Harbour
Validation of WAMSIM – LNG moored in Sheltered Harbour
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• Two LNG Tankers moored
side by side
• 4 linear – elastic mooring
lines
• 2 linear – elastic fenders
• 4 chains
Validation of WAMSIM – Tandem Moored Vessels
Square root of vessel motion spectra
Vessel 1 Vessel 2
Swell Hs Swell Tp Swell Direction Wind Hs Wind Tp Wind Sea Direction
1.5m 16s 25deg 0.5m 7.5s 0deg
03.
Example 1: Passing Vessel Induced Moored
Vessel Motions
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• Port of Brisbane (PoB) is one of Australia’s fastest growing
container Ports
• Channel optimisation to allow larger vessels to transit
• DHI undertook numerical modelling study to identify the affects
of moored vessel motions induced by passing ships at several
key berths
Port of Brisbane Channel Optimisation
Integrated Impact Assessments
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• navigational studies
• channel sedimentation studies
• dredge spill investigations;
• marine ecology and water quality impact assessments
• collision risk with marine mega fauna
• oil spill risk assessment
• underwater sound pollution
• Numerical modelling is often undertaken to solve one particular task
• Limits potential for coupled impact assessment and often makes it difficult
to compare independent studies
• Integrated numerical modelling platform provides the foundation for
multipurpose investigations
• PoB model capabilities :
Wave & Hydrodynamic Modelling
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• DHI’s spectral forecast model for Australian waters (OzSea) to
model locally generated wind waves and swell
• MIKE 21 HD FM to model tidally driven circulation in Moreton Bay
• Spatial resolution refinements of triangular mesh down to 10 m
were made within the navigation channel
• Inner section of the shipping channel, the model resolution was
increased to a 3 x 3m quadrangular mesh
• Validation of the HD model against recorded water levels was
undertaken at five stations
Passing Vessel Modelling
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• Drawdown is generated by a drop in surface elevation along
the length of the hull of the moving vessel.
• Simulate the drawdown wave induced by passing vessel in
MIKE 21 HD
• Pressure field representing the moving stencil was
interpolated onto the model domain grid
• Pressure field generated from 3D vessel grid files and
interpolated to a 2D stencil
• Spatial resolution of 0.2 m x 0.2 m
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Passing Vessel Annimation
Passing Vessel Modelling
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Vessel LOA (m) Beam
(m) Draft (m)
Displacement
(m3)
MR 10.4 183 33 10.4 48,180
LR 10.4 226 32.5 10.4 60,507
MR 11.2 183 33 11.2 52,200
LR 11.2 226 32.5 11.2 65,622
• 9 passing vessel scenarios were
modelled in total.
• Focus on 2 tankers at 2 load states
• For equivalent draft, LR tankers are
~10-15,000m3 heavier than MR tanker
• Results from MIKE 21 HD directly fed
into moored vessel model
Results – Surge Motions of Moored Vessel
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• The largest vessel motions occur at
the Caltex Berth
• All except the Cement berth, the
MR vessel causes larger overall
moored vessel motions than the LR
for equivalent draft.
• Although the maximum drawdowns
from the passing of the LR tankers
at the berths are higher, the
moored vessel motions are lower at
most berths.
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• The vessel generating the maximum drawdown varies with
distance from the vessel to the edge of the model boundary
• For two vessels with identical draft and almost identical
width, although the maximum extent of the drawdown field
is greater for the longer vessel, the wider draw down wave
dissipates more slowly with distance.
• As a result, the longer vessel will only cause larger draw
down than the short vessel after a certain distance away
from the hull.
Passing distance threshold
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• Although the maximum extent of the
drawdown field is larger for the LR
tanker, the water level induced
pressure gradients at the moored
vessel are lower under the passing LR
scenario.
• Lower in line and transverse gradients
from the passing of the LR tanker
results in lower turning moments of
the vessel
Drawdown variability
04.
Example 2: Transshipment Terminal Operability
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Transshipment Terminal Operability Objective
• Development of an offshore transhipment facility for the transfer of iron ore from shallow draft vessels to ocean going vessels
• Determine operability of a number of tandem moored vessel systems
• Process:
• Run FRC for each of the multibody systems (Nves)
• Create single body MIKE 21 MA setups (mooring system) in MIKE 21 MA for each of the multibody systems and convert these to multibody setups (Nves)
• Determine environmental forcings to be run in order to adequately calculate operability (Nenv)
• Use MIKE 21 MA setups as templates to generate batches of MIKE 21 MA setups for each mooring system and environmental condition. In total Nves * Nenv MIKE 21 MA setups will be generated
• Determine the number of scenarios which exceed operability threshold for each mooring system and calculate operability by: Nfailed / Nenv
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Transshipment Terminal Operability FVRE and DVRE setups
• 8 Multibody systems were run
• Up to 4 bodies were run in this study
• 3 body case shown as example
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• Environmental forcing conditions were provided as hourly values over the years 2000-2015
• Timeseries’ of the environmental conditions were created for each hour. This resulted in 90,000+ distinct environment conditions
• Winds: Constant timeseries of wind speed and direction was generated for each simulation
• Current: Constant timeseries of current speed and direction was generated for each simulation
• Waves:
• Hs, Tp and direction were provided for both swell and wind wave components
• Using the Pierson Moskowitz spectrum and the Hs and Tp provided with MIKE’s random wave generator, timeseries’ of surface elevation of the swell and wind wave for each simulation was generated and processed to MIKE 21 MA inputs
• 90,000+ Wave, Wind and Current Conditions
Transshipment Terminal Operability Environmental Conditions
Transshipment Terminal Operability Results
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• Example Run Times:
• FRC: 3 body case, 7824 submerged panels = 27hrs
• Mike 21 MA: 90,000 simulations = 2 days
• The final result were operability tables detailing the operability for each mooring system.
• This was extended to detail the operability in each year and month between 2000-2015.
• These results helped the client choose which mooring system to develop
Scenario Individual Relative Combined
Scenario A 97% 98% 97%
Scenario B 95% 97% 95%
Scenario C 94% 98% 95%
Summary
• MIKE 21 MA is a highly sophisticated model which, in conjunction with MIKE 21 FM HD & BW can accurately
represent vessel motions as a result of highly complex, non – linear wave fields
• Easy to use GUI with well defined inputs/outputs
• Outputs are all dfs0 and post-processing is easily done with the MIKE 21 toolbox PP tools
• MIKE 21 MA is capable of accurately assessing moored vessel response from the most simple cases (single
vessel in open water) to very complex cases (multiple vessels, reflective quays)
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Thank you Poul Kronborg [email protected]
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