6 Degrees-of Freedom Towed Buoy Dynamic Assessment Kristian Geleff - - PowerPoint PPT Presentation

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6 degrees of freedom towed buoy dynamic
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6 Degrees-of Freedom Towed Buoy Dynamic Assessment Kristian Geleff - - PowerPoint PPT Presentation

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6 Degrees-of Freedom Towed Buoy Dynamic Assessment Kristian Geleff UDT, Glasgow, 2018 Marine Land Aviation Nuclear www.babcockinternational.com UDT 2018 Introduction 6 Degrees-of Freedom Towed Buoy Dynamic Assessment Introduction

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SLIDE 1

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Marine Land Aviation Nuclear

6 Degrees-of Freedom Towed Buoy Dynamic Assessment

Kristian Geleff – UDT, Glasgow, 2018

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www.babcockinternational.com

UDT 2018

Marine Land Aviation Nuclear

Introduction

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6 Degrees-of Freedom Towed Buoy Dynamic Assessment

  • Introduction of the system
  • Purpose of developing this capability
  • Challenges
  • Simulation
  • Key Performance Indicators
  • Conclusion
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SLIDE 3

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UDT 2018

Marine Land Aviation Nuclear

Introduction

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Comms at Speed and Depth Environment (waves, wind etc) Long Towing Cable

Speed, depth, manoeuvres Operating window Water properties Towing Platform Wave Affected Zone

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SLIDE 4

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UDT 2018

Marine Land Aviation Nuclear

Purpose

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Provide confidence across a number of areas:

  • Assess simulation performance against test data
  • Validation activities
  • Assess performance impact of design changes
  • Developmental tool - improve design & performance
  • Assess performance across wide range of operating scenarios
  • Time and availability of platforms make this very challenging to achieve with testing
  • Define operating envelope – interpolate between measured points of data
  • De-risking tool – increase likelihood of full scale trials being successful
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SLIDE 5

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UDT 2018

Marine Land Aviation Nuclear

Challenges

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Scale

  • Underway towed systems are very large

‒ Towed body to towing platform spans hundreds of meters

  • No test facilities large enough to accommodate full scale testing
  • Requires towing platform

‒ Often actual platform due to lack of suitable research platforms

  • High risk going from the drawing board to full scale tests

Hydrodynamic scaling

  • Different for turbulent transition (Reynolds Number Re) and wave making resistance (Froude Number Fr)
  • Not possible to scale for both simultaneously
  • Scale based on Fr and add leading edge trips to artificially trigger turbulent transition at lower Reynolds Numbers.

Tank Testing

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Marine Land Aviation Nuclear

Challenges

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Operating Environment

  • Wind and waves by nature are chaotic and turbulent
  • Repeatable experiments cannot be achieved
  • Sea states are characterised in statistical terms i.e. significant wave height, period..
  • Statistical methods of analysing performance becomes necessary

500 1000 1500 2000 2500 Time (s) Elevation (m) Wave Elevation

  • 4
  • 3
  • 2
  • 1

1 2 3 4 Probability Density Standard Deviation

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SLIDE 7

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UDT 2018

Marine Land Aviation Nuclear

Challenges

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The highly coupled nature of a towed buoy system makes testing of sub-systems and components of limited value.

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SLIDE 8

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UDT 2018

Marine Land Aviation Nuclear

Challenges

  • Simulation in the wave affected zone:
  • Full 6 degree of freedom buoy dynamics

required for complex shape

  • Hydrodynamic coefficients required for all

impingement angles

  • Hydrodynamic scaling challenges

1 2 3 4 5 6 7 8

  • 1.5
  • 1
  • 0.5

0.5 1 1.5 Fluid direction (xz plane) Fluid Velocity (m/s) Time (s)

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SLIDE 9

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UDT 2018

Marine Land Aviation Nuclear

Simulation

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UDT 2018

Marine Land Aviation Nuclear

Key Performance Indicators

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Monitor KPIs: Availability

  • Antenna depth
  • Antenna orientation

Results:

  • Availability (%)
  • Min, max, mean, standard deviation

500 1000 1500 2000 2500 Time (s) Depth (m) Towed Buoy Depth Towed Buoy Depth Mean Upper Depth Bound Lower Depth Bound Minimum Depth Maximum Depth

Operating Window

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SLIDE 11

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UDT 2018

Marine Land Aviation Nuclear

Key Performance Indicators

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Assessment of KPI across

  • perating scenarios
  • Identify operating scenarios

where performance improvements required

  • Quantify performance of

design changes

  • Performance prediction for

end user

Note: Random data used to demonstrate visualisation

Depth (m) z z z z z z z z z z z z z z z y y y y y y y y y y y y y y y y y y x x x Sea State b Sea State b Sea State b Speed (kts) Heading Heading Heading

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SLIDE 12

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UDT 2018

Marine Land Aviation Nuclear

Conclusion

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Challenges facing development of submarine towed buoy systems have been discussed

  • Full scale testing is expensive and logistically difficult
  • Scaling effects and highly coupled natured limits value of small scale/sub element testing
  • Operating environment is chaotic and not easily replicated in a controlled test
  • Statistical validation

Simulation is an enormously valuable tool

  • Design and development
  • Cost and risk reduction
  • Predicting operating envelope
  • Reducing development timescales
  • Maximising chance of success for full scale testing
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SLIDE 13

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UDT 2018

Marine Land Aviation Nuclear

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