1 TMR4225 Marine Operations, 2007.01.25 Lecture content: –Linear submarine/AUV motion equations...
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Transcript of 1 TMR4225 Marine Operations, 2007.01.25 Lecture content: –Linear submarine/AUV motion equations...
1
TMR4225 Marine Operations, 2007.01.25
• Lecture content:– Linear submarine/AUV motion equations
– AUV hydrodynamics – Hugin operational experience
2
Linear motion equations
• Linear equations can only be used when– The vehicle is dynamically stable for motions in horisontal and
vertical planes
– The motion is described as small perturbations around a stable motion, either horisontally or vertically
– Small deflections of control planes (rudders)
– For axisymmetric bodies the 6DOF equations can be split in two sets of 2 DOF equations
3
Dynamic stability
• Characteristic equation for linear coupled heave - pitch motion:– ( A*D**3 + B*D**2 + C*D + E) θ = 0
• Dynamic stability criteria is:– A > 0, B > 0 , BC – AE > 0 and E>0
• Found by using Routh’s method
4
Dynamic stability (cont)
• For horisontal motion the equation (2.15) can be used if roll motion is neglected
• The result is a set of two linear differential equations with constant coefficients
• Transform these equations to a second order equation for yaw speed
• Check if the roots of the characteristic equation have negative real parts
• If so, the vehicle is dynamically stable for horisontal motion
5
Methods for estimating forces/moments
• Theoretical models– Potential flow, 2D/3D models– Lifting line/lifting surface– Viscous flow, Navier-Stokes equations
• Experiments– Towing tests (resistance, control forces, propulsion)– Oblique towing (lift of body alone, body and rudders)– Submerged Planar Motion Mechanism– Cavitation tunnel tests (resistance, propulsion, lift)– Free swimming
6
Methods for estimating forces/moments
• Empirical models– Regression analysis based on previous experimental results using
AUV geometry as variables
7
Submarine and AUV motion equations
• 6 degrees of freedom equations
• Time domain formulation
• Simplified sets of linear equations can be used for stability investigations
8
EUCLID Submarine project
•MARINTEK takes part in a four years multinational R&D programme on testing and simulation of submarines, Euclid
NATO project “Submarine Motions in Confined Waters”. •Study topic:
•Non-linear hydrodynamic effects due to steep waves in
shallow water and interaction with nearby boundaries.
9
Testing the EUCLID submarine in waves
• Model fixed to 6 DOF force transducer
• Constant speed
• Regular waves
• Submarine close to the surface
10
Numerical study of bow plane vortex
Streamlines released at bow plane for 10 deg bow plane angle (Illustration: CFDnorway)
Streamlines released at bow plane for -10 deg bow plane angle (Illustration CFDnorway)
12
AUV overview
• AUV definition:– A total autonomous vehicle which carries its own power and does
not receive control signals from an operator during a mission
• UUV definition:– A untethered power autonomous underwater vehicle which
receives control signals from an operator
– HUGIN is an example of an UUV with an hydroacoustic link
13
AUV/UUV operational goals
• Military missions– Reconnaissance
– Mine hunting
– Mine destruction
• Offshore oil and gas related missions– Sea bed inspection
– Pipe line inspection
• Sea space and sea bed exploration and mapping– Mineral deposits on sea floor
– Observation and sampling
14
Offshore oil and gas UUV scenario
• Ormen Lange sea bed mapping for best pipeline track
• Norsk Hydro selected to use the Hugin vehicle
• Hugin is a Norwegian designed and manufactured vehicle
• Waterdepth up to 800 meters
• Rough sea floor, peaks are 30 – 40 meter high
• Height control system developed for Hugin to ensure quality of acoustic data
15
Phases of an AUV/UUV mission
• Pre launch• Launching• Penetration of wave surface (splash zone)• Transit to work space• Entering work space, homing in on work task• Completing work task• Leaving work space• Transit to surface/Moving to next work space• Penetration of surface• Hook-up, lifting, securing on deck
17
AUV – Theoretical models
• Potential theory– Deeply submerged, strip theory
– VERES can be used to calculate
• Heave and sway added mass
• Pitch and yaw added moment of inertia
– VERES can not be used to calculate
• Surge added mass
• Roll added moment of inertia
18
AUV- Theoretical models
• Viscous models
• Solving the Navier Stokes equations– Small Reynolds numbers (< 1000) : DNS
– Medium Reynolds numbers (< 10**5) : LES – Large Eddy Simulation
– High Reynolds numbers (> 10**5) : RANS – Reynolds Average
Navier Stokes
19
AUV – Theoretical models
• 3D potential theory for zero speed - WAMIT– All added mass coefficients
– All added moment of inertia coefficients
– Linear damping coefficient due to wave generation
• Important for motion close to the free surface
• More WAMIT information– http://www.wamit.com
20
NTNU/Marine Technology available tools:
• 2 commercial codes– Fluent
– CFX
• In-house research tools of LES and RANS type
• More info: Contact Prof. Bjørnar Pettersen
21
AUV – Experimental techniques
• Submerged resistance and propulsion tests– Towing tank
– Cavitation tunnel
• Submerged Planar Motion Mechanism tests– Towing tank
• Oblique towing test– Towing tank
• Lift and drag test, body and control planes– Cavitation tunnel
22
AUV – Experimental techniques
• Free sailing tests– Towing tank
– Ocean basin
– Lakes
– Coastal waters
• Free oscillation tests/ascending test– Water pool/ Diver training pool
23
HUGIN history
• AUV demo (1992-3)– Diameter: 0.766 m Length: 3.62/4.29 m
– Displacement: 1.00 m**3
• HUGIN I & II (1995-6)– Diameter: 0.80 m Length: 4.8 m
– Displacement: 1.25 m**3
• HUGIN 3000C&C and 3000CG (1999-2003)– Diameter: 1.00 m Length: 5.3 m
– Displacement: 2.43 m**3
24
NTNU/MARINTEK HUGIN involvement
• AUV demo (1992-3)– Model test in cavitation tunnel, open and closed model, 2 tail
sections (w/wo control planes)• Resistance, U = {3,10} m/s
• Linear damping coefficients for sway, yaw, heave and pitch, yaw/trim angles {-10, 10} degrees
– 3D potential flow calculation • Added mass added moment of intertia
– Changes in damping and control forces due to modification of rudders
– Student project thesis
25
NTNU/MARINTEK HUGIN involvement
• HUGIN 3000– Resistance tests, w/wo sensors
• Model scale 1:4
• Max model speed 11.5 m/s
• Equivalent full scale speed?
– Findings• Smooth model had a slightly reduced drag coefficient for increasing
Reynolds number
• Model with sensors had a slightly increased drag coefficient for increasing Reynolds numbers
• Sensor model had some 30% increased resistance
26
HUGIN information
• New vessels have been ordered late 2004 and 2005– One delivery will be qualified for working to 4500 m waterdepth
• New instrumentation is being developed for use as a tool for measuring biomass in the water column
• Minecounter version HUGIN 1000 has been tested by Royal Norwegian Navy
• More Hugin information: see Kongsberg homepage for link
27
HUGIN field experience
• Offshore qualification seatrials (1997)
• Åsgard Gas Transport Pipeline route survey (1997)
• Pipeline pre-engineering survey (subsea condensate pipeline between shorebased process plants at Sture and Mongstad) (1998)
• Environmental monitoring – coral reef survey (1998)
• Fishery research – reducing noise level from survey tools (1999)
28
HUGIN field experience• Mine countermeasures research (1998-9)• Ormen Lange pipeline route survey (2000)• Gulf of Mexico, deepwater pipeline route survey (2001 ->)• Raven, West Nile Delta, Egypt, area of 1000 km**2 was
surveyed late 2005 by Fugro Survey– Sites for subsea facilities– Route selection for flowlines, pipelines & umbilicals– Detect and delineate all geo-hazards that may have an impact on
facilities installetion or well drilling– Survey area water depth: 16 – 1089 m (AUV used for H > 75 m)– Line spacing of 150 m and orthogonal tie-lines at 1000 m intervals– Line kilometers surveyed by AUV: 6750 km – Distance to seabed (Flying height): 30-35 m– Operational speed: 3.6 knots
30
Actual HUGIN problems
• Inspection and intervention tasks– Adding thrusters to increase low speed manoeuvrability for
sinspection and intervention tasks• Types, positions, control algorithms
– Stabilizing the vehicle orientation by use of spinning wheels (gyros)
• Reduce the need for thrusters and power consumption for these types of tasks
– Docking on a subsea installation• Guideposts
• Active docking devices on subsea structure (robotic arm as on space shuttle for capture of satelittes)
31
Actual HUGIN problems
• Roll stabilization of HUGIN 1000– Low metacentric height– 4 independent rudders – PI type regulator with low gain, decoupled from other regulators
(heave – pitch – depth, sway – yaw, surge)– Task: Keep roll angle small ( -> 0) by active control of the four
independent rudders• Reduce the need for thrusters and power consumption for these types of
tasks
– Docking on a subsea installation• Guideposts
• Active docking devices on subsea structure (robotic arm as on space shuttle for capture of satelittes)
32
Future system design requirements
• Launching/ pick-up operations up to Hs = 5 m when ship is advancing at 3-4 knots in head seas
• Increasing water depth capability
• Increased power capability– Operational speed 3- 4.5 knots
– Mission length 3- 4 days