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HYDRODYNAMICS OF PLANING HULL BY CFD
UNIVERSITY OF NAPLES FEDERICO II POLYTECHNIC AND BASIC SCIENCES SCHOOL DEPARTMENT OF INDUSTRIAL ENGINEERING
THESIS MASTER’S DEGREE IN NAVAL ENGINEERING
SUPERVISOR CANDIDATE
PROF. ERMINA BEGOVIC, PH.D. MARCELLO IACONO
CORRELATOR
SIMONE MANCINI, PH.D. STUDENT
Academic year 2014/2015
FROUDE NUMBER
planing vessels
The Alpha-Z stepped planing hull designed by Michael Peters
TOTAL RESISTANCE
Methods for bare hull resistance: •Experimental method (e.g.: Froude method) •Empirical method (e.g.: Savitsky [1964], Savitsky [2010], Morabito [2010])
•Systematic series (e.g.: Series 62, Series 65, Series 62 Dutch, BK series, MBK series, Kowalyshyn D. and Metcalf B. Series (2006), Taunton D. J. et al. Series (2011), Begovic E. and Bertorello C. Series (2012), De Luca F. and Pensa C. Series (2014) •Statistical methods (e.g.: Radojcic’s method [1985], Holtrop) •CFD (Computational Fluid Dynamics)
PRESSURE AND SPRAY ROOT AREAS
Flat plate surface Deadrise surface
EQUILIBRIUM CONDITION FLAT PLATE
SOTTORF
EQUILIBRIUM CONDITION MONOHEDRALL HULL
SAVITSKY SHORT FORM
SAVITSKY SHORT FORM PROCEDURE
PRESSURE DISTRIBUTION
MORABITO METHOD On the spray and bottom pressures of planing surfaces, Ph.D. Thesis
Stevens Institute of Technology, 2010
Symmetry line
Effect of the transom stern
Other sections
Begovic E. and Bertorello C., 2012 Resistance assessment of warped hull forms
EXPERIMENTAL REFERENCE WORK
COMPUTATIONAL FLUID DYNAMICS
NUMERICAL SETUP
STAR-CCM+ CD-adapco Turbulence model k-epsilon Time step 0.005-0.002 Iterations 3
At four different velocities:
3.4 m/s Frb=1.667 FrV=1.921 4.6 m/s Frb=2.256 FrV=2.599 5.75 m/s Frb=2.819 FrV=3.248 6.32 m/s Frb=3.098 FrV=3.569
SCoPE Operating System For multidisciplinary
scientific Processing
RESISTANCE COMPARISON MONOHEDRAL HULL
35
40
45
50
55
60
3,4 4,6 5,75 6,32
Res
ista
nce
[N
]
v [m/s]
Exp
Coarse grid
Medium grid
Fine grid
Savitsky short form
2.6% 5.3%
WARPED HULL
40
45
50
55
60
3,4 4,6 5,75 6,32
Res
ista
nce
[N
]
v [m/s]
Exp Coarse Grid Medium grid Fine grid Savitsky short form
1.9%
1.8%
5.8% 8.1%
4.8%
TRIM COMPARISON MONOHEDRAL HULL
WARPED HULL
3,2
3,4
3,6
3,8
4,0
4,2
4,4
4,6
4,8
5,0
3,4 4,6 5,75 6,32
Trim
[d
eg]
v [m/s]
Exp Coarse grid Medium grid Fine grid Savitsky short form
2,0
2,5
3,0
3,5
4,0
4,5
5,0
3,4 4,6 5,75 6,32
Trim
[d
eg]
v [m/s]
Exp Coarse grid Medium grid Fine grid Savitsky short form
18.6%
10.3% 14.9%
5.2%
14.8%
6.4% 14.4%
4.5%
SINKAGE COMPARISON MONOHEDRAL HULL
WARPED HULL
-10
-5
0
5
10
15
20
25
30
35
40
3,4 4,6 5,75 6,32
Sin
kage
[m
m]
v [m/s]
Exp
Coarse grid
Medium grid
Fine grid
0
5
10
15
20
25
30
35
40
45
3,4 4,6 5,75 6,32
Sin
kage
[m
m]
v [m/s]
Exp
Coarse grid
Medium grid
Fine grid
WETTED SURFACE COMPARISON MONOHEDRAL HULL
WARPED HULL
0,50
0,55
0,60
0,65
0,70
0,75
0,80
0,85
3,4 4,6 5,75 6,32
Wet
ted
Su
rfac
e [m
2 ]
v [m/s]
Exp Coarse grid Medium grid Fine grid Savitsky short form
0,50
0,55
0,60
0,65
0,70
0,75
0,80
3,4 4,6 5,75 6,32
Wet
ted
Su
rfac
e [m
2 ]
v [m/s]
Exp Coarse grid Medium grid Fine grid Savitsky short form
14.3%
6.1% 1.6%
8.1%
11.7%
4.2% 7.0%
Coarse grid at v=6.32 m/s
Medium grid at v=6.32 m/s
Fine grid at v=6.32 m/s
Coarse grid at v=6.32 m/s
Medium grid at v=6.32 m/s
Fine grid at v=6.32 m/s
MONOHEDRAL HULL WARPED HULL
MONOHEDRAL HULL WARPED HULL
Experimental and numerical wetted surfaces, v=5.75 m/s Experimental and numerical wetted surfaces, v=5.75 m/s
MONOHEDRAL HULL WARPED HULL
Longitudinal pressure distribution at v=5.75 m/s Longitudinal pressure distribution at v=5.75 m/s
MONOHEDRAL HULL TRANSVERSAL PRESSURE LINES AT V=6.32 M/S
WARPED HULL TRANSVERSAL PRESSURE LINES AT V=6.32 M/S
-500
0
500
1000
1500
2000
0,00 0,05 0,10 0,15 0,20 0,25 Hyd
rod
ynam
ic P
ress
ure
(P
a)
Half beam (m)
x=-0,256 (0,25 L)
x=0,141 (0,4 L)
x=0,494 (0,55 L)
x=0,891
0
500
1000
1500
2000
2500
0,00 0,05 0,10 0,15 0,20 0,25
Hyd
rod
ynam
ic P
ress
ure
(P
a)
Half beam (m)
x=-0,344 (0,25 L) x=0,053 (0,4 L) x=0,406 (0,55 L)
TRANSVERSAL DISTRIBUTION AT 0,25 L
-50
0
50
100
150
200
0,00 0,05 0,10 0,15 0,20 0,25
Hyd
rod
ynam
ic P
ress
ure
(P
a)
Half beam (m)
v=3.4 m/s
MONO x=-0,344 (0,25 L)
W2 x=-0,256 (0,25 L)
-50
0
50
100
150
200
250
300
0,00 0,05 0,10 0,15 0,20 0,25 Hyd
rod
ynam
ic P
ress
ure
(P
a)
Half beam (m)
v=4.6 m/s MONO x=-0,344 (0,25 L)
W2 x=-0,256 (0,25 L)
-100
0
100
200
300
400
500
0,00 0,05 0,10 0,15 0,20 0,25 Hyd
rod
ynam
ic P
ress
ure
(P
a)
Half beam (m)
v=5.75 m/s
MONO x=-0,344 (0,25 L) W2 x=-0,256 (0,25 L)
0
100
200
300
400
500
600
0,00 0,05 0,10 0,15 0,20 0,25
Hyd
rod
ynam
ic P
ress
ure
(P
a)
Half beam (m)
v=6.32 m/s MONO x=-0,344 (0,25 L)
W2 x=-0,256 (0,25 L)
MONOHEDRAL HULL LONGITUDINAL PRESSURE DISTRIBUTION AT V=6.32 M/S
WARPED HULL LONGITUDINAL PRESSURE DISTRIBUTION AT V=6.32 M/S
-1000
-500
0
500
1000
1500
2000
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Pre
ssu
re (P
a)
Length (m)
at keel
Empirical Evaluation
Numerical Evaluation by CFD - Fine grid
-2000
-1000
0
1000
2000
3000
4000
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 Pre
ssu
re (P
a)
Length (m)
at keel Empirical Evaluation
Numerical Evaluation by CFD - Fine grid
CONCLUSIONS
1. Accuracy of numerical results
2. Savitsky method gives the best results for resistance and wetted surface (difference from
experimental in the order of 2%), while CFD calculations are more accurate than Savitsky method
for trim angle
3. Stagnation and spray root lines, Pressure profiles, Longitudinal pressure distributions evaluated
from CFD calculations are very close to results of Morabito method, Peaks and transversal
pressure distributions
4. Even though experimentation remains the tool most commonly used by designers to obtain
accurate values of the hydrodynamic forces acting on the boat, empirical methods are very
inexpensive and fast to use. Advantages of numerical simulations: the flow streamlines, the wave
profiles or the pressure distribution
ACKNOWLEDGEMENTS
Thanks to availability of 32 processors at HPC Centre SCoPE of University of Naples “Federico II” and thanks to SCoPE academic staff for the given support.
