1. TMR4225 Marine Operations, 2006.02.09 Lecture content:
AUV hydrodynamics and
Hugin operational experience
What are you expecting to learn from todays lecture?

2. Dynamic stability 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 constant motion, either horisontally or vertically
Small deflections of control planes (rudders)

3. 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

4. Dynamic stability (cont)
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

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 motion equations
6 degrees of freedom equations
Time domain formulation
Simplified sets of linear equations

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.

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10. AUV overview AUV definition: UUV 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

11. 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

12. 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

13. 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

14. Hugin UUV

15. 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

16. 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

17. 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

18. 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

19. 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

20. AUV – Experimental techniques
Submerged resistance and propulsion tests
Towing tank
Cavitation tunnel
Submerged Planar Motion Mechanism tests
Oblique towing test
Lift and drag test, body and control planes

21. AUV – Experimental techniques
Free sailing tests
Towing tank
Ocean basin
Lakes
Coastal waters
Free oscillation tests/ascending test
Water pool/ Diver training pool

22. HUGIN history AUV demo (1992-3) HUGIN I & II (1995-6)
Diameter: m Length: 3.62/4.29 m
Displacement: m**3
HUGIN I & II (1995-6)
Diameter: m Length: 4.8 m
Displacement: m**3
HUGIN 3000C&C and 3000CG ( )
Diameter: m Length: 5.3 m
Displacement: m**3

23. 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

24. NTNU/MARINTEK HUGIN involvement
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

25. 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)

26. HUGIN field experience
Mine countermeasures research (1998-9)
Ormen Lange pipeline route survey (2000)
Gulf of Mexico, deepwater pipeline route survey (2001 ->)

27. 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)

28. 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)

29. 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 knots
Mission length 3- 4 days

30. 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

31. Hugin deployment video
Video can be downloaded from Kongsberg homepage

32. TMR4225 Marine Operations,
Sum up the 3 most important learning outcomes of todays lecture
Have your expectations been fulfilled?
If not, why not?