TMR4225 Marine Operations, 2005.05.02 Dynamic stability of underwater vehicles Hugin status Russian proposal for oil and gas production in Arctic Odyssey IV

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)

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

Dynamic stability (cont.) Characteristic equation for linear coupled heave - pitch motion: ( A*D**3 + B*D**2 + C*D + E) r’ = 0 Dynamic stability criteria is: A > 0, B > 0 , BC – AE > 0 and E>0 Found by using Routh’s method

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

Methods for estimating forces/moments Empirical models Regression analysis based on previous experimental results using AUV geometry as variables

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

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

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

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

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

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

HUGIN history AUV demo (1992-3) HUGIN I & II (1995-6) 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

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

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

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)

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

HUGIN 3000 Characteristics Operational depth: 3000 m Mission lenght: 58 hours Nominal speed: 4 knots Position accuracy: 2-3 m for water depths > 2000 m Costs: 30 – 45 mill NOK (2002) Number produced 3 (2002)

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)

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

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

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

Principal Investigator AUV-LAB MIT Odyssey IV Principal Investigator C. Chryssostomidis F. Hover Design Team R. Damus S. Desset J. Morash V. Polidoro

Russian proposal for Arctic oil and gas production No existing infrastructure Harsh environment (ice and low temperatures) Using subsea vehicles for drilling and prosuction

Standard Field Construction Scheme

Underwater Drilling System Submarine Drilling Vessel Bottom Template

Consumable Replenishment System Submarine Support Vessel Drilling Vessel Transport Container Triton class ROV Transport Container Cargo deck

Mulig Stockman utbygging SDV TRUV SSV ROV BT TLP Container TMS 2…3 km

% probability of sea ice (April) in Barents Sea (Orheim, Houston, 2005) Shtokman

Example: 3 days track for iceberg (marking per 3 hours) (Orheim, Houston, March 2005)