Chia Po Lin EWTEC Lisbon 1995. PhD Thesis Edinburgh University

Chia Po Lin EWTEC Lisbon 1995. PhD Thesis Edinburgh University



Thanks to

Wikipedia

Surface tension force = 4 x Side x 73 milliNewton / metre at 15C

Buoyancy force = Side3 x 1000 kilogram /metre3 x g

0 2 4 6 8 100

2

4

6

8

Buoyancy and surface tension forces on cubes floating nearly awash

Cube side mm

For

ce m

illi

new

tons

Buoyancy = surface tension at 5.5 mm side cube

1% error for a 55 mm cube. One part in 340 for a 100 mm cube

0 20 40 60 80 1000.95

0.96

0.97

0.98

0.99

1Gravity force / Gravity plus surface tension for cubes as a function of side.

Cube side mm

Err

or

Combined

Capillary

Gravity

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.20

0.2

0.4

0.6

0.8

Phase velocity of gravity and capillary waves versus wavelength

Wave length metre

Vel

ocity

met

res/

seco

nd

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

1

2

3

4

5

6

7

8

9

10Percentage velocity error as a function of wavelength

Wave length metres

Err

or p

erce

nt

1% error at 121 mm. 1 in 1700 at 500 mm

Drag coefficients as a functions of Reynolds number. Hermann Schlichting

300

300,000

Nearly 1000 :1 OK. Then a drop by a factor of 4 at ReN = 500,000

Full scale cylinder diameter 10 metres

Full scale wave trough to crest 4 metres

Full scale wave period 9 seconds

What scale gives Reynolds number of 500,000?





10 :1





10 :1But drag forces are ~ 1/30 less than inertial forces and 90°out of phase so who cares?

KeuleganCNoVelocity Period

Diameter


Diameter

KeuleganCNo

HeightPeriod

Period

Diameter


Diameter

KeuleganCNo

HeightPeriod

Period

Diameter

NASA

1/100 1/10 1/1

Model / device cost £5 - £1k £10K- £200k £3m-£20m

Model weight 1kg 1 tonne 1000 tonne

Launch time minutes 1-5 days ~>year

Repeatability 1:1000 Tank 1:1000Open sea 0

0

Test duration 128 sec 10 min months

Control √ √ XFault repair time hours days Months-

>1 year

Drag coefficient error 400%

Not understanding ‘off-the-shelf’ components and materials.

Because investors give launch date priority over reliability.

F ig u r e 5 . P la n a n d e l e v a t io n s k e t c h e s o f t h e t e s t p la t f o r m .

Trying to survive loads above those at the economic limit.

What the sea isdoing to your part

every ~10 seconds

What fractionof your parts

will fail

0 1 2 3 4 5 6 7 80

0.2

0.4

0.6

0.8

1Probabilty distribution of stress and endurance

Multiple of root mean square stress

sdev1 0.4

MS1 5

3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 40

0.0002

0.0004

0.0006

0.0008

Probabilty distribution of stress and endurance


MTBF2 = 67.2 days

Need mean stress 6.3 times std. deviation to get MTBF = 150 years

0 1 2 3 4 5 6 7 80

0.2

0.4

0.6

0.8

1Probabilty distribution of stress and endurance


sdev2 0.2

MS2 2.4

MTBF2 830.3 yr

Using the wrong installation equipment.

. . . . standing up in a hammock

http://www.scanmudring.no/?page=301&menu=4&id=6

SUGGESTED CRAWLER SPECIFICATION

Frame dimensions 12.19m x 2.43m x 2.59m

Weight 30 tonne

Power 100kW

Smooth seabed, side-on, no slide current 5 m/sec

Side-on no roll 1 m clearance 11 m/sec

Vertical lift all 8 legs 300 kN

Horizontal thrust 400 kN

Walking speed 280 mm/sec = 0.55 knot

360 degree azimuth rotation 11 min

Step size with digital hydraulics 1 mm

Mud pressure with maximum size feet 12 kPa

Maximum obstacle clearance 2.1 m

Slope climbing on rock 45 degrees

Payload tools and materials 20 tonne

Conventional work vessel

Pull only. Very slow direction change.



Needs intelligent heavy lift capability at both ends.




Hard fragile skin punctured in tens of millimeters.





Fixed wave response not matched to client.






Independent operation.







Potentially fatal heel induced by work forces.








Winches, cranes and own electrical generation .









Too heavy to be lifted by container crane.









Too heavy to be lifted by container crane.

Conventional GPS with precision of tens of metres.

Ideal Installation vessel

Push, pull, twist and shear 280 kN in any direction in seconds.



Fast connection and disconnection.




Soft skin deflecting > 2 metres.





Wave response adjusted to match client object.






Co-operation between multiple units from a single point.







No heel induced by work forces.








Source of electrical, hydraulic and pneumatic power.









Sea container handling points.









Sea container handling points.

Local differential, carrier-phase navigation.

http://www.voithturbo.com/vt_en_pua_marine_vspropeller.htm

Has lovely animation of rotor blade angles.

http://www.voithturbo.com/vt_en_pua_marine_vspropeller.htm

What we did wrong the first time

Had a leadership which wanted us to fail.

Now every developer wants every other developer to fail.

Will this majority succeed?

What went wrong the first time ?


Having a leadership that secretly wanted the project to fail.



Choosing a single very big target 2 GW.




Relying on second rate consultants.




Relying on second rate consultants.

Not thinking enough about phase.

What we are doing wrong now

Moving in the wrong direction.

Going to full scale with inadequate small scale measurements.

Not understanding ‘off-the-shelf’ components and materials

because investors give launch date priority over reliability.

Trying to survive loads above those at the economic limit.

Using the wrong installation equipment.

Having sharp corners.

Not reporting failures to one another.

Not thinking enough about phase.

Moving in the wrong direction.

Going to full scale with inadequate small-scale measurements.

Documents

Chia Po Lin EWTEC Lisbon 1995. PhD Thesis Edinburgh University