AKHIL KARTHIKA AJITH 7 th EMship cycle: September 2016 February 2018 - - PowerPoint PPT Presentation

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AKHIL KARTHIKA AJITH 7 th EMship cycle: September 2016 February 2018 - - PowerPoint PPT Presentation

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Structural design and Stability of a 6,000 ton Capacity Floating Dock as per DNVGL Rules AKHIL KARTHIKA AJITH 7 th EMship cycle: September 2016 February 2018 Master Thesis Development Of Flap Rudder Systems For Large Container Vessels

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SLIDE 1

Kodathoor Midhun, 7 th EMship cycle: 2016 − 2018 Defence of Master Thesis, Szczecin, January 2018

Structural design and Stability of a 6,000 ton Capacity Floating Dock as per DNVGL Rules

Development Of Flap Rudder Systems For Large Container Vessels

Master Thesis

AKHIL KARTHIKA AJITH

7th EMship cycle: September 2016 − February 2018

Supervisor: Dr. Nikolai Kornev, University of Rostock, Rostock, Germany I nternship tutor: Mr. Steve Leonard, I BMV Maritime I nntionsgesellschaft, Rostock, Germany Reviewer: Mr. Jean-Baptiste Souppez, Southampton Solent university, UK

La spezia, February 2018

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SLIDE 2

Why Flap Rudd dder For Containership p Opera ration?

  • Higher safety and higher side force compared to

conventional rudders

  • Better maneuvering ability
  • Compared to conventional rudder lesser rudder area

required to provide same side force

  • Improved course keeping with reduced rudder angle.
  • Reduced tug assistance for small feeder vessels

2 EMSHIP 2016-18

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SLIDE 3

Obje jectives o

  • f t

the Study

  • Feedback from large containership owners regarding the

low maneuvering problem in shallow water

  • Previous CFD analyses indicates that flow separation

starts from the flap rather than the leading edge

  • Existing linkage mechanism means relatively aggressive

flap operation at small rudder angles

  • Initial project aim to develop new flap actuation ratios

EMSHIP 2016-18 3

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SLIDE 4

Bec Becker Flap Rudder r CFD An Analysis

  • Two dimensional analysis
  • 1. New flap ratios find out by changing the

value of a/b ratios.

  • 2. a/b values from 1.5 to 1.7 incremented by

0.05

  • 3. Flow analysis conducted at slow speed

(8 knot) and cruise speed (23 knot) conditions.

  • 4. Wake values are derived from the model

test result at 14.5 m draft (VA).

4 EMSHIP 2016-18

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SLIDE 5

Details of 2D CFD Pl Plan

  • Flow analysis conducted at +0.7R & -0.7R
  • f the rudder horizontal section
  • Domain size fixed based on chord length
  • f rudder
  • 50000 to 80000 cells used (polyhedral)
  • Base size fixed at 0.9m with 1.05 times

surface growth

  • Prism layer count fixed at 7 with steady

case & full scale rudder

  • 5 to 10 minutes for meshing & analysis

using 383 processor server

EMSHIP 2016-18 5

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SLIDE 6

Results ts o

  • f Two Dimensional Analysis

EMSHIP 2016-18 6

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 5 10 15 20 25 30 Lift Force (N)

x 10000

Rudder Angle (Deg) Lift vs Flap Ratios (uppeside -port-slow speed, +0.7R) Lift Force Lift Force Lift Force Lift Force Lift Force

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SLIDE 7

Flow Separation at 12° for Existing ng Flap R Rud udder

EMSHIP 2016-18 7

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SLIDE 8

Result o

  • f Two Dimensional CFD

D Stud udy

  • Analysis result recommend that Flap Ratios D

(a/b=1.7) has reduced aggressiveness in flap

  • peration
  • Stall angle delayed 6 to 8 degree for each case of

Ratio D

  • Further increase of a/b ratio not possible due to

space limitations caused by trunk/stock dimensions

  • Flow separation appears to start from the

forward part of flap / end point of suction side

  • f rudder

EMSHIP 2016-18 8

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SLIDE 9

Three Dimensional An Analysis

  • Flow analysis done with the ship hull

and virtual propeller.

  • Wake calculated independently, file

as table in STAR-CCM+.

  • Comparison of existing ratios and
  • ptimum ratios
  • Impact of water depth in rudder side

force.

  • Hull force in different water depth.

EMSHIP 2016-18 9

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SLIDE 10

Details of T Three Dimensional CFD Pl Plan

  • Base size fixed 30.3 m
  • 1/3 of the ship hull considered for the analysis
  • Analysis done at full scale
  • Steady-state
  • 5 to 6 million cells used per case
  • k-omega SST turbulence model used
  • 383 processors
  • Run time – about 2 hours per case

EMSHIP 2016-18 10

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SLIDE 11

Details of Three Dimensional CFD Pl Plan

EMSHIP 2016-18 11

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SLIDE 12

Result t of T Three Dimensional Analysis

EMSHIP 2016-18 12

  • 8.00E+00
  • 6.00E+00
  • 4.00E+00
  • 2.00E+00

0.00E+00 2.00E+00 4.00E+00 6.00E+00

  • 40
  • 30
  • 20
  • 10

10 20 30 40 LIFT FORCE (N)

Millions

Rudder Angle (Deg) Rudder Lift vs Rudder Angle Ratio D,shallow depth exisiting ratios ,shallow depth

Starboard Port

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SLIDE 13

Result t of T Three Dimensional Analysis

  • Result from the 3D analysis are diffrent from

the 2D analysis

  • From the flow analysis realized that flow

seperation start from the leading edge

  • Rudder Bulb appear to triger flow seperation

EMSHIP 2016-18 13

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SLIDE 14

Result t Of T Three Dimensional Analysis

EMSHIP 2016-18 14

  • 8.00E+00
  • 6.00E+00
  • 4.00E+00
  • 2.00E+00

0.00E+00 2.00E+00 4.00E+00 6.00E+00

  • 40
  • 30
  • 20
  • 10

10 20 30 40 LIFT FORCE (N)

Millions

Rudder Angle Rudder Lift vs Rudder Angle Ratio D,slow speed exisiting ratios ,slow speed without bulb -slow speed

Starboard Port

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SLIDE 15

Shear S r Stress D Distri ribution A At 18° Rudder An r Angle

Rudder with normal condition Rudder with the absence of bulb

EMSHIP 2016-18 15

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SLIDE 16

Leading Edge Flow S Separation & Rudder r Bulb Inter eraction

  • n
  • Present flow analysis for the twisted flap rudder with bulb shows that

flow separation starts from the leading edge of intersection of bulb and rudder geometry.

  • Bulb is present to reduce fuel consumption – elimination of propeller

hub vortex.

  • Bulb optimized for power-saving.

EMSHIP 2016-18 16

Investigate effect of removing bulb

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SLIDE 17

EMSHIP 2016-18 17

Symmetrical rudder with bulb Symmetrical rudder without bulb Twisted rudder with blended LE Twisted Rudder with horizontal transition plate

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SLIDE 18

Ne New Ge Geom

  • metries

es Vs Existing T g Twisted ed Flap Rudder er

EMSHIP 2016-18 18

  • 1.20E+00
  • 9.00E-01
  • 6.00E-01
  • 3.00E-01

0.00E+00 3.00E-01 6.00E-01 9.00E-01 1.20E+00

  • 40
  • 30
  • 20
  • 10

10 20 30 40 Lift Force (N)

Millions

Rudder Angle (Deg) Rudder vs performance symmetric rudder symmeric rudder without bulb blended Leading Edge twisted rudder with transition plate exisiting rudder

Port Starboard

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SLIDE 19

Shea ear F Force C ce Comparison

  • n -Existing &

& Symmetrical Rudder G r Geometry (Rudde

dder a and F d Flap r p rotate 2 25° towards ds port s side) e)

Existing rudder with new ratio D Symmetric rudder with new ratio D

EMSHIP 2016-18 19

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SLIDE 20

Impac act o

  • f Ship Hu

Hull a at Di Different W Water De Depths (8 k knot

  • ts)

)

  • In this section we compare the ship hull forces and

moments with approximate rudder turning moment

  • Ship hull force & turning moment are calculated with

different turning radii to ship length ratio (R/L) and drift angle β

EMSHIP 2016-18 20

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SLIDE 21

Rudder er S Side F e Force I e In Differ erent W t Water er D Depths

EMSHIP 2016-18 21

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SLIDE 22

Hu Hull M Moment &R &Rud udder M r Moment –Suez C Canal al & & De Deep De Depth

EMSHIP 2016-18 22

  • 200

200 400 600 800 1000 2 4 6 8 10 12 Hull Moment in million (N.m) Drift Angle (Deg) Hull Moment

shallow depth R/L=100 shallow depth R/L=10 shallow depth R/L=5 Deep water R/L=100 Deep water R/L=10 Deep water R/L=5

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SLIDE 23

Hu Hull M Moment &R &Rud udder M r Moment –Suez C Canal al & & De Deep De Depth

EMSHIP 2016-18 23

  • 200

200 400 600 800 1000 2 4 6 8 10 12

Hull Moment in million (N.m) Drift Angle (Deg)

Hull Moment & Rudder Moment comparison

shallow depth R/L=100 shallow depth R/L=10 shallow depth R/L=5 Deep water R/L=100 Deep water R/L=10 Deep water R/L=5 Flap rudder -Max. rudder moment

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SLIDE 24

Ho How t to Overcome the E Existing Problem o

  • f Hi

High Hu Hull F Force & & Turning M Moment

  • Hull forces dominate in shallow water condition

compared to deep water.

EM SHIP 2016-18 24

Solutions Benefits Penalties

Increasing rudder Area Increasing the side force

  • peration difficulties

production cost Improving the rudder section Improving the flow characteristics, Increasing the side force Unlikely to provide sufficient improvement Twin-screw propulsion Increasing the side force in large magnitude gain in side force vs production expense?

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SLIDE 25

Conclusions

  • 2D& 3D analysis results are different
  • Flap ratio D has better performance
  • Rudder bulb appears to start the flow separation at leading edge
  • Numerical analysis of flow around rudder recommend that

symmetrical rudder without bulb have improved flow separation & side forces than existing one

  • Large container ships in shallow water – hull forces dominate.
  • Vessel operated in shallow water require a specific recommendation
  • f maneuvering operation

EMSHIP 2016-18 25

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SLIDE 26

Future W e Works & Recom

  • mmen

endation

  • ns
  • Transient analysis with explicit propeller (rotating mesh)
  • Full 3D restrictions (include banking)
  • Bulb details
  • Model tests

Thank you

EMSHIP 2016-18 26