TMR4225 Marine Operations, 2007.01.25

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

16. Hugin UUV

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

29. Fugro survey pictures http://www.fugrosurvey.co.uk/

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

33. Hugin deployment video • Video can be downloaded from Kongsberg homepage