Ingen lysbildetittelHugin status
Odyssey IV
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)
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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
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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
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Oblique towing (lift of body alone, body and rudders)
Submerged Planar Motion Mechanism
Free swimming
Empirical models
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Heave and sway added mass
Pitch and yaw added moment of inertia
VERES can not be used to calculate
Surge added mass
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All added mass coefficients
Linear damping coefficient due to wave generation
Important for motion close to the free surface
More WAMIT information
Medium Reynolds numbers (< 10**5) : LES – Large Eddy Simulation
High Reynolds numbers (> 10**5) : RANS – Reynolds Average
Navier Stokes
More info: Contact Prof. Bjørnar Pettersen
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Towing tank
Cavitation tunnel
Towing tank
Cavitation tunnel
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Displacement: 1.00 m**3
HUGIN I & II (1995-6)
Displacement: 1.25 m**3
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
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
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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)
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Gulf of Mexico, deepwater pipeline route survey (2001 ->)
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Costs: 30 – 45 mill NOK (2002)
Number produced 3 (2002)
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
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Low metacentric height
4 independent rudders
PI type regulator with low gain, decoupled from other regulators (heave – pitch – depth, sway – yaw, surge)
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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
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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
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No existing infrastructure
Using subsea vehicles for drilling and prosuction
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(Orheim, Houston, 2005)
Example: 3 days track for iceberg (marking per 3 hours)
(Orheim, Houston, March 2005)