mobile offshore base research challenges
DESCRIPTION
MOBILE OFFSHORE BASE RESEARCH CHALLENGES. 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. Outline. Summary: ONR MOB S&T Program Research Challenges. - PowerPoint PPT PresentationTRANSCRIPT
MOBILE OFFSHORE BASE RESEARCH CHALLENGES
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
Outline
Summary: ONR MOB S&T Program
Research Challenges
MOB HydromechanicsS&T Summary
Broad, balanced program addressing a range of S&T topics corresponding to MOB design
Driven by: USER!– operational, survival and transit aspects– wide range of MOB platform characteristics– ALL accompanying support information
Deliverables include:– preliminary and final analysis tools– pioneering hydroelastic models and data– wave excitation - structural loads interface– pioneering wave coherence information
MOB HydromechanicsS&T Technology Transfer
MOB Hydromechanics S&T is applicable to all large offshore vessels and structures
Commercial airports (cargo) Remote military training airfields
MOB HydromechanicsS&T Summary
Key S&T Opportunities:
– Analyze hydroelastic data!
– Continue wave coherence studies
– Complete Classification Guide
– develop a technique that will apply viscous damping to VLFS structures with “small” modules
Crest Only;
“This is not a wave.”
“Paired Crest + Trough;
“This is a wave.”
“Disjointed Crest;
“This is unknown!”
““What is a [3D] ‘wave’?”What is a [3D] ‘wave’?”
MOB Hydromechanics 4.1 Automatic Control: Multibody Dynamic
Positioning
UC Berkeley Algorithms and Demonstration
MOB Hydromechanics 2.1.1 Time Domain Limitations, LAMP
Pitch
Exper, freq domain @ fforcing
LAMP @ fforcing + fnat
anat ~ 4 * aforcing
Semis have low pitch radiation damping. LAMP model generated resonance during the ramp, no decay mechanism.
(t)
MOB HydromechanicsOther “VLFS” Structures
Amphibious Lighterage Waterside Security Barriers
MOB HydromechanicsNavy Amphibious Lighterage
Platform dimensions– Module: 100 by 24 by 2 ft, 100 tons (30 by 7 by .6 m)
– Causeway: 1,200 ft (366 m)
– Water depths: 0 to 9 m
MOB HydromechanicsNavy Amphibious Lighterage
Problem: damping!
FrontMiddleBack
+ Sway+ Sway
HYDRAN Sway Damping for RRDF Platforms
0100020003000400050006000700080009000
10000
2 4 6 8 10 12 14
Period (seconds)
Sw
ay
Da
mp
ing
(lb
s-s
ec
/ft)
Front
Middle
Back
CF Sway RAOs vs Wave Heading. Front
Module, Hawser @ 45 degrees, k = 3 kips/ft
0
10
20
30
40
50
2 6 10 14 18
Period (seconds)
Sw
ay R
AO
M, 60
H, 60
MOB HydromechanicsNavy Waterside Barriers
“VLFS?” Note aspect ratio!
Problem: damping again.
