1. MOBILE OFFSHORE BASE HYDROMECHANICS
Dr. Paul Palo
U. S. Naval Facilities Engineering Service Center
Centre for Ships and Ocean Structures
Norwegian University of Science and Technology
29 October 2004
The purpose of this briefing is to provide an overview of the ONR Science and Technology program, which has been underway since February 1997.
The first grant was awarded in March and the initial contract awarded in July In the subsequent 2-12/ years approximately 75 grants and contracts have been awarded towards the goal of assessing MOB feasibility and cost.
The Naval Facilities Engineering Service Center (Port Hueneme CA) coordinates the technical program for ONR.

2. Outline Overview: SeaBasing and MOB Overview: ONR MOB S&T Program
MOB Hydromechanics S&T
Science & Technology (S&T) Evaluation Process
Hydromechanics S&T and Products
Supporting S&T Activities
Summary

3. Overview of SeaBasing and MOB

4. SeaBasing and MOB Sample Mission Requirements
SeaBase Function: provide complete logistics support for ground personnel
Transit to site in reasonable time
Receive supplies from CONUS
Store, prepare, stage supplies
Transport supplies to shore

5. SeaBasing and MOB SeaBase Requirements #1 of 3
Single Module Transit
Scenario
Full cargo &
Deballasted on pontoons
Fastest Transit Time
Maximum Speed versus
Sea State
Incident Wave Direction
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

6. SeaBasing and MOB SeaBase Requirements #2 of 3
On-site operations
Positioned miles off coast
Large Vessel Unloading through Sea State __
Small Vessel Loading through Sea State __
Survive Extreme Events through Sea State __
Accommodate __-number of VTOL aircraft
Stationkeeping (Dynamic Positioning)
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

7. SeaBasing and MOB SeaBase Requirements #3 of 3
On-site operations: optional?
CTOL Aircraft Operations
This greatly complicates the engineering:
Multiple Module Platform
Connect through Sea State __
Provide acceptable dynamics through Sea State __
Optional Disconnect through Sea State __
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

8. SeaBasing and MOB Family of SeaBase Concepts
Navy-favored
“SeaBase” Platform
based on MPF(F)
& V-22 Osprey
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.
“MOB”
Platforms

9. SeaBasing and MOB Range of MOB Platform Configurations
Single Module
Two Modules
Hinged Platform
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.
Bridged Platform
Dyn. Pos. Platform

10. SeaBasing and MOB MOB Module and Platform Sizes Semi- submersible VLCC
300m (DB102)
VLCC
455m (Seawise Giant)
CVN
320m (Nimitz)
This viewgraph puts into perspective the magnitude of the MOB concept relative to the state of practice by superimposing the largest/most mission-capable MOB platform versus other state-of-the-art platforms.
Note: at the inception of this ONR program, MOB concepts were sized to satisfy all mission require-ments, including CTOL operations up to the C-17. This leads to the nominal one-mile long platform [shown above] built as an assembly of smaller modules.
However - you will see in this briefing that we now know that most MNS-derived mission requirements can be satisfied with far smaller and less costly structures.
M O B
Semisubmersible Module
m length
m beam
35m draft
Platform Configuration
m length
1 to 5 modules
Rigid/Hinged/Bridged/DP Connectivity

11. MOB S&T Program

12. ONR MOB S&T Program ONR Program Overview
Program Objectives
Establish Feasibility and Cost of MOB(s)
Funding
$36M
FY96-00

13. ONR MOB S&T Program NFESC Program Overview
Program Objectives
Establish feasibility and cost
Define a consistent design methodology
Reduce technology gaps
Advance industry capability to DoD req’ts
Make DoD a “smart buyer”
53-organization Project Team
26 commercial firms (domestic and int’l)
16 academic institutions
11 government agencies

14. ONR MOB S&T Program S&T Evaluation Process
Identify Mission Requirements
Still undefined as of 2004!
Representative missions defined
Candidate Platform Characteristics
Nonquantified missions  unknown length
Hierarchy of platforms based on length
& connection scheme
Define Engineering Design Requirements
State-of-the-Art Capabilities
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.
Prioritize Science & Technology Tasks

15. ONR MOB S&T Program Unprecedented Design Challenges
Semisubmersible module size
Multiple module platform
Connectivity
Length/configuration
Open ocean dynamics
Motions (Aircraft operations, vessel motions)
Wavefield (Stresses, Cargo transfer, Air gap)
Failure Modes (1st torquing mode)
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

16. ONR MOB S&T Program MOB Uniqueness
MOB exceeded state of practice
- No consensus methodology to design, down-select,
build, and operate a MOB.
MOB as an “Innovative Structure”
- An Innovative Structure -- “is usually the first of its kind; few, if any, design standards directly apply and there is little operational experience to relate to the design review process.” (National Research Council, 1991)
“Technical evaluation of such structures must be based on fundamental engineering principles, requiring specialists in the relevant disciplines.”

17. ONR MOB S&T Program Roadmap = Classification Guide
3. Classification Requirements
2. Requirements & Procedures
1. General
11. Dynamic Positioning
13. Maintenance
14. Environmental
Compliance
6. Materials
4. Environment
5. Loads
7. Structural Resistance
8. Engineering Analysis
9. Structural Design
10. Stability
12 . Fabrication
Requirements
Demands
Capacity
Analysis/Design
Assessment

18. MOB Hydromechanics S&T

19. MOB Hydromechanics Science & Technology Categories
1. Operational Dynamics
2. Survival Dynamics
3. Transit Dynamics
4. Validation Tests and Analysis
5. Exercise Models
6. Met/Ocean Specification
Achieve mission requirements
Assure safety of personnel and materiel
Provide reasonable response time

20. MOB Hydromechanics S&T Balance
Validation Data
$4.3M
$1.9M
Advance
& Exercise Models
Metocean Specification
Achieve mission requirements
Assure safety of personnel and materiel
Provide reasonable response time
MOB Classification Guideline

21. MOB Hydromechanics Science & Technology Issues
1. Operational Dynamics Models
1.1 Platform dynamics
1.2 Connection/Disconnection
1.3 Fatigue structural loads
1.4 Stationkeeping
For Each Issue -
Identify key requirements
Assess State-of-the-art
Highlight advancement and product
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

22. MOB Hydromechanics 1.1 Platform Dynamics
Example Calculations
Motions of one module
Transit
Operations
Motions of connected platform
Column and pontoon shape
optimization
Dynamics of berthed vessels
Key Model Requirements
Inviscid, linear & stationary acceptable
Hydrodynamic coupling; mean drift force
Highly efficient numerical solver
Hydroelasticity [rigid and/or elastic bodies]
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

23. MOB Hydromechanics 1.1 Platform Dynamics
State-of-the-Art Summary (Frequency Domain)
HOBEM (high-order, single, rigid body)
AQWA (rigid, multiple bodies, no coupling)
MORA (rigid, multiple bodies; adjacent coupling only)
HYDRAN (hydroelastic, rigid, hydrodynamic coupling;
computationally intensive)
WAMIT (hydroelastic, hydrodynamic coupling; computationally
intensive)
HIPAN (single, rigid body; higher-order; computationally
efficient)
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

24. MOB Hydromechanics 1.1 Platform Dynamics
MOB Frequency Domain S&T:
1.1.1 Advance WAMIT & HIPAN models
Refer to N. Newman presentation
1.1.2 Develop alternative dynamic model
1.1.3 Develop simplified preliminary design tool
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

25. MOB Hydromechanics 1.1 Platform Dynamics
1.1.1 Advance WAMIT & HIPAN models
Objective: provide fully-coupled hydroelastic final
design model(s)
Performer: MIT, AeroHydro
Product:
2 associated deliverables (Fast-WAMIT & HIPAN)
HIPAN: high-order potentials on patches & panels using b-spline body geometry description
WAMIT: pre-computed FFT solver (up to 3 orders of magnitude computational increase) makes this the only model capable of full MOB study
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

26. MOB Hydromechanics 1.1 Platform Dynamics
1.1.2 Develop alternative dynamic model
Objective: provide numerically efficient preliminary
design model
Performer: OSA Inc. (Chakrabarti)
Product:
diffraction theory model (fully-coupled, rigid-body)
two-stage analysis: (1) potentials for isolated individual modules; (2) superposition
avoids large panel problem entirely; allows for efficient parametric configuration studies
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

27. MOB Hydromechanics 1.1 Platform Dynamics
1.1.3 Develop simplified preliminary design tool
Objective: provide numerically efficient preliminary
design model
Performer: Off Coast Inc. (Ertekin & Riggs)
Product:
based on a simplified (uncoupled, rigid body) version of the HYDRAN diffraction theory model
menu- & library-based interactive preprocessor
Rayleigh damping for [equiv] viscous drag
deliberately simplified to allow for efficient parametric configuration studies
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

28. MOB Hydromechanics 1.2 Connection/Disconnection
Key Model Requirements:
Inviscid, linear & stationary acceptable
Multiple modules with varying mean positions and arbitrary approach path
Impact and/or elastic loads desirable
State-of-the-Art Summary (Time Domain)
LAMP (described next)
CFD viscous models: not sufficiently mature
MOB Time Domain S&T:
1.2.1 Advance LAMP model
1.2.2 Develop simplified connection model (MORA)
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

29. MOB Hydromechanics 1.2 Connection /Disconnection
1.2.1 Advance LAMP model
Objective: advance accuracy of this nonlinear model
Performer: SAIC (Annapolis).
Product:
“fully-nonlinear” time domain model (rigid-body; large waves and responses; multiple bodies with nonstationary mean positions)
computationally-intensive model
advanced free surface condition from incident to instantaneous
Encountered fundamental air gap deficiency (see S&T topic 2.1)
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

30. MOB Hydromechanics 1.2 Connection /Disconnection
1.2.2 Develop simplified connection model
Objective: develop “piecewise stationary” prelimi-
nary analysis model for wave motions
Performer: C. J. Garrison and Assoc
Product:
efficient preliminary analysis tool (via MORA)
three stage solution: (1) determine frequency domain behavior for two bodies at finite number of fixed mean positions along approach path; (2) convert to time domain “retardation functions”; (3) interpolate for continuous dynamics
avoids intensive time domain solution
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

31. MOB Hydromechanics 1.3 Fatigue structural loads
Key Model Requirements
Inviscid, linear & stationary acceptable
Interface pressure distribution from arbitrary hydro panel into arbitrary structural element surface meshes
State-of-the-Art Summary (Time Domain)
None (SAS; restricted to identical meshes)
MOB Time Domain S&T
1.3.1 Universal loads generator

32. MOB Hydromechanics 1.3 Fatigue structural loads
1.3.1 Universal loads generator
Objective: Develop a universal pressure loads generator post-processor
Performers: MIT, Aerohydro Inc, McDermott
Product:
b-spline representation for body geometry and potentials
convert Fast-HIPAN pressures into local pressures for locally nonlinear responses
allows for optimum hydro and structural discretizations (maximum accuracy)
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

33. MOB Hydromechanics 1.3 Fatigue: universal loads generator
Structural
ABAQUS
Hydrodynamic
MIT / HIPAN
AeroHydro/HIP2FEA
Define Geometry
MOB-HyLoads
Wind & Current Loads
Time history wave loads
Analysis Procedures
Mean Drift Forces
Define
Sea State

34. MOB Hydromechanics 1.4 Stationkeeping
Key Model Requirements
Current and wind loads on semisubmersibles, including viscous wakes, wave, and free surface effects
Desirable: multi-body capability for connect simulations and shielding effects
State-of-the-Art Summary (Time Domain)
CFD (not sufficiently mature)
MOB S&T
None. (1) Hydro CFD not pursued because there are no apparent short-term opportunities to advance modeling of free surface and high Reynolds Number flows. (2) Wind CFD for aircraft landing/takeoff environment not pursued as not critical to feasibility objective.

35. MOB Hydromechanics Science & Technology Issues
2. Survival Dynamics
2.1 Extreme Motions
Air gap
Wave impact
Run-up on columns
2.2 Extreme structural loads
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

36. MOB Hydromechanics 2.1 Extreme Motions
Key Model Requirements
Goal = required column height for semi design
Accurate modeling of instantaneous free surface and [nonstationary] wetted surface of body
Single (disconnected) rigid body; uncertain if inviscid models are necssary
State-of-the-Art Summary (Time Domain)
LAMP model (simplified to incident free surface)
MOB S&T
2.1.1 Apply LAMP model (see previous Task & next visual)
2.1.2 Advance AEGIR model

37. MOB Hydromechanics 2.1 Extreme Motions
2.1.2 Advance AEGIR model
Objective: advance development of this nonlinear
time domain model
Performer: MIT
Product:
“fully-nonlinear” time domain model (rigid-body; large waves and responses; inviscid; nonstationary mean positions)
highly flexible formulation; includes run-up
Incomplete development at end of MOB program
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

38. MOB Hydromechanics 2.2 Extreme Structural Loads
Key Model Requirements
Accurate pressures induced on [nonstationary] wetted surface of body
Multiple bodies, elasticity (if connected in extreme events)
Viscosity preferrable
State-of-the-Art Summary (Time Domain)
Morison Equation, based on long wavelengths in typical extreme seas and MOB characteristic dimensions of columns and pontoons. Inviscid models (e.g., LAMP) do not include viscous damping and have been shown to yield misleading results. Uncertainties with: coefficients, shielding, and wave crest kinematics.
MOB S&T
None.

39. MOB Hydromechanics Science & Technology Issues
3. Transit Dynamics Models
3.1 Platform dynamics (stability, accelerations)
3.2 Nonlinear Stability
3.3 Dynamics while in damaged condition
Continuing the Mission Requirements and Performance Measures Product Area:
The tools listed here provide the means for insuring that MOB designs satisfy the mission requirements in the most efficient and cost effective manner.
The tools provide the means for assessing any concept/design on the basis of constructability, functional performance, operational availability and cost.

40. MOB Hydromechanics 3.1 Transit Dynamics Models
Key Model Requirements
Accurate modeling of instantaneous wave pressures and buoyancy on [nonstationary] wetted surface of body as pontoons intermittently submerge and waves overtop
Single, rigid body models acceptable; importance of viscosity unknown
State-of-the-Art Summary (Time Domain)
No industry experience similar to MOB transit. LAMP allows for changing wetted surface, but does not model dynamics of waves above the pontoons.
MOB S&T
3.1 Apply LAMP model (see previous Task 1.2.1)

41. MOB Hydromechanics 3.2 Nonlinear Stability Model
2.1.2 Evaluate Stability during transit
Objective: investigate single, deballasted module
dynamics (with pontoon immersion)
Performer: Univ of New Orleans
Product:
Estimation of orbits, attractors, etc to nonlinear buoyancy and “representative” viscous damping
Not a solved topic!
Continued development of the “Reverse MI/SO” system identification UNO (see Task 4.4)

42. MOB Hydromechanics 3.2 Damage Dynamics Models
Key Model Requirements
Assess stability and motions for large heel and trim static conditions [due to explosive detonations]
Accurate modeling of instantaneous free surface and [nonstationary] wetted surface of body. Internal voids?
Single, rigid body models acceptable; importance of viscosity unknown
State-of-the-Art Summary (Time Domain)
No specific criteria yet developed. LAMP allows for changing wetted surface.
MOB S&T
3.2 Apply LAMP model (see previous Task 1.2.1)

43. MOB Hydromechanics Science & Technology Issues
4. Validation Tests and Analysis
4.1 Hydroelastic Tests
4.2 Limited Hydroelastic Validations
4.3 Transit Dynamics Tests and Analysis
4.4 Air gap Tests

44. MOB Hydromechanics 4.1 Hydroelastic Tests
Key Data Requirements
Accurate structural knowledge of platform response
Accurate knowledge of spatial wavefield
State-of-the-Art Summary (Time Domain)
Limited; typically very small scale and for mats
MOB S&T
4.1 Conduct hydroelastic tests of generic, connected
MOB semisubmersibles

45. MOB Hydromechanics 4.1 Hydroelastic Tests
4.1 Conduct Tests at NSWC-CD
Objective: provide a hierarchy of data for 1, 2, and 5 module elastic MOB platforms with connectors
Performer: Naval Surface Warfare Center, Carderock
Detachment (MASK facility)
Product:
guided by 2-day workshop of government, academia, and industry, and real-time QA
Four 6m fully-elastic modules
Multi-axis spring connectors
Limited. Exhausted funding before data analysis. See next topic.

46. MOB Hydromechanics 4.1 Hydroelastic Tests
6m Elastic Module
Connector

47. MOB Hydromechanics 4.1 Hydroelastic Tests
27.5m Elastic Platform Model

48. MOB Hydromechanics 4.2 Limited Hydroelastic Validations
Objective: conduct preliminary validations using subsets of NSWC-CD data
Test Performer: McDermott Technologies; OSA; University of Hawaii; University of Maine
Products:
limited evaluations for 1 and 2 module configurations
Opportunity??

49. MOB Hydromechanics 4.3 Transit Dynamics Tests and Analysis
Key Data Requirements
Rigid body motions of a semisubmersible at transit draft (minimal freeboard up on the pontoons)
Nonlinear buoyancy (pontoons versus column waterplane) results in complicated dynamics best treated with nonlinear phase plane techniques
State-of-the-Art Summary (Time Domain)
None; unique problem to MOB
MOB S&T
4.4 Conduct transit dynamics tests

50. MOB Hydromechanics 4.4 Transit Dynamics Tests and Analysis
Objective: examine transit dynamics
Test Performer: U. S. Naval Academy (Annapolis)
Data Analysis: University of New Orleans
Products:
4m model length; same as NSWC module
direct use of data for validation of LAMP, etc.
indirect use of data to qualify and quantify equations of motion using “Reverse MI/SO” nonlinear systems identification technique (per NFESC).

51. MOB Hydromechanics 4.4 Transit Dynamics Tests
4m Rigid Module

52. MOB Hydromechanics 4.5 Air Gap Tests
Key Data Requirements
Rigid body motions and wavefield for a semisubmersible at survival draft
State-of-the-Art Summary (Time Domain)
Proprietary (e.g., LAMP)
Industry divided as to the accuracy of state-of-the-art modeling
MOB S&T
4.5 Conduct air gap tests

53. MOB Hydromechanics 4.5 Air Gap Tests
Objective: provide data for subject conditions
Test Performer: U. S. Naval Academy (Annapolis)
Pre-test Simulations: SAIC (Annapolis)
Products:
same model as for transit dynamics tests
3 response channels; 13 wave channels (sensors on model and fixed)
ultimately intended for validation of LAMP and other model predictions.

54. MOB Hydromechanics Science & Technology Issues
5. Exercise Models
5.1 Benchmark Comparison of Existing Diffraction
Models
5.2 Benchmark LAMP Exercise
5.3 Berthed Vessel Simulations
5.4 Industry Experience with Seakeeping Models

55. MOB Hydromechanics 5.1 Benchmark Comparison of Diffraction Models
Objective: benchmark existing models for MOB
applications
Test Performer: Bechtel
Products:
parametric assessment of small amplitude, linear diffraction theory models
HOBEM, AQWA, MORA, WAMIT, HIPAN and HYDRAN exercised for single semisubmersibles and connected platforms
quantitatively established general guidance on how to properly apply diffraction theory models for VLFS semi seakeeping studies

56. MOB Hydromechanics 5.2 Benchmark LAMP Exercise
Objective: investigate numerical use of LAMP
Test Performer: Naval Facilities Engineering Service
Center (Port Hueneme CA)
Products:
investigate discretization of: body, free surface, and matching surface for transit conditions
preliminary guidance on LAMP relative accuracy versus number of panels

57. MOB Hydromechanics 5.3 Berthed Vessel Simulations
Objective: examine dynamics of vessels in the
confused wavefield associated with large
MOB semisubmersibles
Test Performer: McDermott Engineering (Houston)
Products:
preliminary assessment of dynamic motions during cargo handling operations
quantify errors if incident waves only are [incorrectly] used as excitation

58. MOB Hydromechanics 5.4 Industry Experience with Seakeeping Models
Objective: indirect assessment of industry capability
to correctly apply seakeeping models
Test Performers: McDermott Engineering (Houston)
Kvaerner
Bechtel
Aker
Products:
valuable insight regarding transition of new models and extrapolation of old models to MOB
consensus opinion: their original expectations that MOB was a direct extension of state-of-the-art was too simplistic

59. MOB Hydromechanics Science & Technology Issues
6. Metocean Specification at O(km) Scales
6.1 Metocean Specification
6.2 Wave Spatial Coherence: Data Analysis
6.3 Wave Spatial Coherence: Modeling
Critical for accurate motion and stress estimates
Low order modal responses will be excited only if waves are long-crested and narrowbanded.

60. MOB Hydromechanics 6.1 Metocean Specification
Key Requirements
Knowledge of wind/wave/current phenomena at MOB O(2 km) scale; internal waves and solitons included
Necessary for elastic responses and cell/environmental contour design methods in MOB Classification Guide
State-of-the-Art Summary of Wave Fields
None.
MOB S&T
6.1 Develop general engineering-oriented specification
6.2 Numerically investigate wave properties from existing
data sets
6.3 Advance physics-based models into “3+1” dimensions

61. MOB Hydromechanics 6.1 Met/Ocean Specification
Objective: compile engineering-oriented guidance for wind/wave/current excitation of MOB
Performers: Bechtel (numerous subcontractors)
Products:
Extensive MOB Environmental Specification
2 Extensive MOB Climatological Databases
23 sites, 20 6 hrs
Pacific storms, 1 km mesh, 1 hr intervals
Excellent general guidance for marine structures
Missing critical wave coherence information

62. MOB Hydromechanics 6.2 Wave Spatial Coherence: Data Analysis
Objective: provide “quick-look” guidance regarding
open ocean wave crest lengths
Performers: JHU/APL; ERIM; WHOI/UMiami;
UWyoming/NASA
Products:
Guided by ONR Workshop, Aug 1997
numerically investigate wave properties from existing SAR, SRA, wave gauge data sets
Unresolved question: “what is a ‘wave’?”
First-ever measurements of the wavefield in a Hurricane

63. MET/OCEAN DESCRIPTORS
WAVES IN HURRICANE BONNIE
Scanning Radar Altimeter (NASA)
There is very limited information regarding wind, waves, and current at the 1-mile scale of MOB platforms. In fact, no information existed at the beginning of this program regarding waves within hurricanes and/or typhoons.
This Program sponsored development of an Environmental Specification for MOB Platforms using inputs from a half a dozen nationally-recognized experts in meteorological/ocean conditions.
In addition, this program helped support flights by the NASA “Hurricane Hunters” that provided the first ever measurements of the waves within a hurricane (above). The level of gray indicates vertical height; white is a crest while black is a trough. The largest wave (in the “North” panel) has a total wave height of approximately 60 ft.
All panels:
~6x1 km
East Panel
North Panel
Northeast Panel

64. MOB Hydromechanics 6.3 Wave Spatial Coherence: Modeling
Objective: advance numerical modeling of evolving
3D wavefields
Performers: MIT; UHawaii; UTorino
Products:
Guided by ONR Workshop, Aug 1997
MIT and Hawaii models balance physics and computational burden
Torino model addresses fundamental physics of rogue waves