May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen 1 Dansis Seminar on Erosion and Cavitation Bjerringbro (DK) May 22, 2019 Christian Johannsen Hamburg Ship Model Basin (HSVA) Bildbereich Experimental Investigation of Cavitation and Erosion at HSVA – The Hamburg Ship Model Basin
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May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
1
Dansis Seminar on
Erosion and Cavitation
Bjerringbro (DK)
May 22, 2019
Christian Johannsen
Hamburg Ship Model
Basin (HSVA)
Bildbereich
Experimental Investigation of Cavitation and
Erosion at HSVA – The Hamburg Ship Model Basin
2
Who is HSVA?
Cavitation in Shipbuilding and its Aftereffects
Model Testing Technique and its Transferability to Reality
HSVA‘s New Erosion Testing Method
Summary
Outline
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
3
Who is HSVA?
Research based services for the maritime industry:
Model tests in open water
and in ice
Computational fluid
dynamics
Design and analysis
Full scale investigations
4
Private, self supporting company
Owned by German Shipping Industry
21 shareholders
100 employees
12 million € turnover per year
83% commercial orders
Internationally acting
43% National
57% International
17% Research
83% Industry
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Who is HSVA?
5
Predictions for...
• Power requirement of ships
• Propeller cavitation behavior, noise and vibration excitation, ersoion
• Manoeuvring behavior of ships
• Seakeeping behavior of ships
• Ice-breaking performance of ships
Design, analysis and optimisation of
• Hull lines
• Propeller geometries
• Ship appendages (ruders, fins, etc.)
Tailor-made studies to all questions around ship hydrodynamics
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
What is HSVA doing?
6
What tools do we use?
1.
2.
300 m long towing tank
Computer Cluster 80 m long ice tank
Cavitation tunnel for complete ship
models
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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The towing tank
300 m x 18 m x 6 m
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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The cavitation tunnel HYKAT
Test section dimensions 11 m x 2.8 m x 1.6 m
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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The ice tank
78 m x 10 m x 2.5/5.0 m
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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The computer cluster
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
90 nodes, 1500 cores
11
Who is HSVA?
Cavitation in Shipbuilding and its Aftereffects
Model Testing Technique and its Transferability to Reality
HSVA‘s New Erosion Testing Method
Summary
Outline
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
12
Cavitation in shipbuilding and its aftereffects
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
At school they taught us:
Water vaporizes at 100°C – but is that true?
13
If pressure is low enough, even cold water vaporizes
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 20 40 60 80 100
Water Temperature [° C]
Va
po
ur
Pre
ssu
re [b
ar]
Atmospheric Pressure at Sea Level
Possible Pressure at
Propeller Suction Side
Atmospheric Pressure at Mount Everest
Cavitation in shipbuilding and its aftereffects
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
14
n D
–
VA
+
+
+
–
–
–
On the propeller blade May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
24. Oktober 2011 Kavitationskolloquium Ruhr-Universität, C. Johannsen
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n D
VA Vt
+
+
+
–
–
–
–
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
On the propeller blade
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n D
VA Vt
+
– –
–
– +
+
Sheet cavitation
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
On the propeller blade
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–
VA Vt
+
+
+ –
–
–
n D
At the blade tip
Tip vortex cavitation
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
18
Erosion May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
19 May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
Cavitation causes pressure variations propagating to the hull
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Full Scale Radiated Noise
60
70
80
90
100
110
120
130
140
150
160
100 1000 10000
Frequency [Hz]
So
un
d P
res
su
re L
ev
el [d
B r
e 1
µP
a,1
Hz,R
MS
,1m
]
Limit Curve
Noncavitating Condition
Cavitating Condition Full Scale Radiated Noise
Cavitating
Non Cavitating
Noise May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation in shipbuilding and its aftereffects
Cavitation collapses make noise
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Cavitation needs to be minimized to...
to avoid damages
to avoid vibrations
to avoid noise inboard and outboard
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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Who is HSVA?
Cavitation in Shipbuilding and its Aftereffects
Model Testing Technique and its Transferability to Reality
HSVA‘s New Erosion Testing Method
Summary
Outline
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
23
Why not using numerics?
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Model Testing Technique and its Transferability to Reality
The environment of cavitation is...
three-dimensional
highly turbulent
instationary
influenced by viscosity effects
compressible (vapor phase)
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H
L
HModel
LModel
For wave generation of a ship:
222
2
2
FnLg
v
Lg
TL
g
TL
g
a
gm
am
ForcesGravity
ForcesMass
Froude Number
ModelShip FnFn !
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Model testing scaling laws
Which of these rectagles scale to each other – and why?
The relevant parameters – here length and height – have the same ration
to each other: Model
Model
HL
HL
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Lg
vWave generation of a
ship Froude No.
Frictional resistance Reynolds No.
Propeller loading Thrust Coef.
Cavitation extent Cavitation No.
ForcesGravity
ForcesMass
ForcesFriction
ForcesMass
Lv
42 Dn
T
2
.
)(2
Dn
PP Vaporstat
PressureStagnation
Press. Vapor toMargin
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Model testing scaling laws
PressureStagnation
Prop.atIncr.Pressure
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Lg
vWave generation of a
ship Froude No.
Frictional resistance Reynolds No.
Propeller loading Thrust Coef.
Cavitation extent Cavitation No.
ForcesGravity
ForcesMass
ForcesFriction
ForcesMass
Lv
42 Dn
T
2
.
)(2
Dn
PP Vaporstat
PressureStagnation
Press. Vapor toMargin
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Model testing scaling laws ...for cavitation testing
PressureStagnation
Prop.atIncr.Pressure
by adjustment of tunnel water speed
by reduction of tunnel pressure
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Hydrodynamics- and Cavitation Tunnel (HYKAT)
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7 m/s
Pabs. 0.4 bar
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Model testing
procedure
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Hydrodynamics- and Cavitation Tunnel (HYKAT)
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May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Model testing
procedure
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Model testing with strobe light
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
Cavitation behavior of a container ship propeller at strobe light
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Model testing - the drawback of strobe light
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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Model testing - the drawback of strobe light
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
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Model testing - the drawback of strobe light
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen
You can‘t see the cavitation dynamics!
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Model testing – full scale similarity of cavitation behavior
Model test in HYKAT Real ship
May 22, 2019 Dansis Seminar, Bjerringbro (DK), C. Johannsen