A mechanical design for a detection unit for a deep-sea neutrino telescope

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A mechanical design for a detection unit for a deep-sea neutrino telescope

VLVnT11 - Edward Berbee - Nikhef

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First concept DOMBAR

Fits in ISO container

13/10/2011 2VLVnT11 - Edward Berbee - Nikhef

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First design

6 mMechanical Cable Connection

Rope & Cable Storage

Rope Storage

Bar Frame

Optical Module

Mechanical Interface

2 DOM + 1 BAR = 1 DOMBAR20 DOMBARS = DOMTOWER

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Floating problem due to flatness

Because of the “flat” top-view the floor tends to float in horizontal direction.


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“turning flaps”“hosted hood”“tuning drum”

Other design ideas; abandoned


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Data VEOC

Mechanical cable (Dyneema rope)

VEOC management

2 double reels for unwinding the ropes


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Some design considerations;

-2 ropes wound around braked cable reels (and so under tension) to perform the unfurling controlled.

-Buoyancy on each floor, above the center of gravity to insure horizontal unfurling of the floors.

-Keep the unfurling speed low for better control (but not to low for drifting away due to current).

-Keep the DU-package compact for easy handling and transportation.

-The rope- and cable unfurling as well as all other items should not happen uncontrolled (without tension) at any moment.


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Slightly rotated bar structures for narrow stacking - complicated cable and rope management!


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Unfurling method-In all methods; tension in ropes

absolutely necessary. Unwinding synchronized

necessary?

All in once, then from the bottom off the package.

-Very high unfurling speed at the beginning.

One by one, from the bottom up,

-Unfurling speed more continuous.

Buoyancy on each storey.

No;-Less need for mechanical construction to separate

one by one.

Yes;- Mechanical construction to

separate one by one absolutely necessary.

Buoyancy on each floor.

Yes;-Less need for mechanical construction to separate

one by one.

No;- Mechanical construction to

separate one by one absolutely necessary.

DOMBAR unfurling constrains; choice made


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Possible designPackage; L x W x H 5800 x 2380 x 2050 mm

Fits a “pallet wide” or “flat rack” container

Floors clamped on vertical tubes, pulled off during unfurling, all under discussion.

“flat rack” container


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Storey with yellow vertical optical cables (VEOC) and two double cable reels at the end (internally braked)

Storey buoyancy, syntactic foam; approx. 450 N - 0,1M3 13/10/2011 11VLVnT11 - Edward Berbee - Nikhef

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Verifying stable dynamic behavior


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-20 bar structures.

-Top buoy.

-3 distance frames.

-Baseframe with clamping tubes.

-2 concrete “Stelcon” plates.

-2 separator racks.


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Possible unfurling

-Buoy is released.

-Buoy pulls of first storey.

-Buoy and first storey will pulloff the second storey etc.

-Released storey will make an approximately 45 degree turn while floating up.

-Tensioned ropes, pull tension approximately 100 N each rope for better control during unfurling.

-Each storey clamped with spring tensioned clamp on 5 vertical tubes, friction on these tubes approx. 500 N.


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Some details

One of the two rollers from the bottom storey to connect to the base frame.

Hinged support plates for stabilizing the end of bar structures.

The three lower storeys are without optical modules.


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Distance frames, the lower one with running wheelsFor rotating of the DU.

Concrete deadweight, (or steel) captured in aluminum profile.

Lower active Bar

Scaled picture

Lower part of the DU

Not scaled picture

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Unfurling of a DU scale model from the seabed up

1:50 model area

Real scale area


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Drag coefficients of importance for the DU

For spheres the drag coefficient Cd= 0.5, For the Dom we take (some extra for the interface); In both horizontal and vertical direction Cd = 0.7

Drag of the cables and ropes; Cd = 1.2

Drag coefficient for the aluminum tubes, circular rod, In both horizontal and vertical direction Cd = 1.2

Storey buoyancy; estimated for flow from the top; Cd = 0.9 estimated for flow from the side; Cd = 0.5

Top-buoy; estimated for flow from the top; Cd = 0.8 Estimated for flow from the side; Cd = 0.4


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0

100

200

300

400

500

600

700

800

900

1000

0 100 200

Hei

ght (

m)

Drift (m)

Hydro dynamic behavior

Characteristics used:

Rope OD (4x) 4 mmVEOC OD (2x) 6.35 mmTop buoyancy 1000 NBar buoyancy 450 NTotal buoyancy 10000 NAnchor 3670 kg (concrete, weight in air)Anchor 2450 kg (steel weight in air)Total transport weight 7420 / 6200 kgTotal weight in sea 1120 kgCalculated drift 165 m @ v = 0.30 m/s

h = 30 cm/s


Used formula;Where: rho = the density of seawater = 1028 kg/m3

v = the speed in m/s Cd = the drag coefficient (dimensionless) A = surface area in m2

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Influences on the amount of drag

Rope OD (4x) 5 mm (instead of 4 mm)Drift 179 m @ v = 0.30 m/s

VEOC OD (2x) 10 mm (instead of 6.35 mm)Drift 190 m @ v = 0.30 m/s

Some examples compared to the situation of the previous slide (drift 165 m);

Top buoyancy 7000 N (instead of 1000N)Bar buoyancy 150 N (instead of 500N)Total buoyancy 10000 N (still)Drift 130 m @ v = 0.30 m/s


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Hydro dynamic behavior

In vertical direction (during unfurling)(450 N local buoyancy)Calculated speed of 1000 N top-buoy at start; 1.46 m/sCalculated speed first storey with top-buoy; 1.13 m/sCalculated speed first two floors with top-buoy; 1.03 m/s Calculated speed at the last floor; 0.85 m/s


In vertical direction with a top buoy of 7000 N instead of 1000 N;(150 N local buoyancy)Calculated (vertical) speed top-buoy at start; 2.48 m/sCalculated speed first storey with top-buoy; 2.04 m/sCalculated speed first two floors with top-buoy; 1.79 m/s Calculated speed at the last floor; 0.89 m/s

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Verifying vertical drag calculation on scale-model

Calculated; 0,060m/s at 0,001 N buoyancy measured speed 0,065 m/s

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Summary;

Calculation for the deviation of the top relative to the bottom at 0.30 m/s current; (possible to improve by a bigger top-buoy) 165 mCalculated speed of 1000 N top-buoy at start; 1.46 m/sCalculated speed first storey with top-buoy; 1.13 m/sCalculated speed at the last floor; 0.85 m/s


A mechanical design for a detection unit for a deep-sea neutrino telescope

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