Textos de Apoio (pdf)

ITTC – Recommended
Procedures
Performance, Propulsion
1978 ITTC Performance Prediction
Method
7.5 – 02
03 – 01.4
Page 5 of 31
Effective Date
1999
Revision
00
C
DM
and
C
DS
⎡
( ) ( )
⎥ ⎥ ⎤
⎞
⎜
⎛ t
⎟⎢
0.04 5
= 2 1 + 2 −
1
2
⎝ c ⎠⎢
6
3
⎣ Rnco
Rnco
⎦
⎛ t ⎞⎛
⎞
2 1 2 ⎜
c
⎜ + ⎟ 1.89 + 1.62.log ⎟
⎝ c ⎠
⎝
k ⎠
= p
−2.5
In the formulae listed above c is the chord
length, t is the maximum thickness, P/D is the
pitch ratio and R nco is the local Reynolds number
at x=0.75. The blade roughness k p is put
k p =30.10 -6 m. R nco must not be lower than 2.10 5
at the open-water test.
2.4.3 Full Scale Wake and Operating Condition
of Propeller
The full scale wake is calculated from the
model wake, w TM , and the thrust deduction, t:
w
TS
=
( ) ( ) ( 1 + k ) C FS
t + 0.04 + wTM
− t − 0.04
( 1 + k) C FM
+ ∆C
where 0.04 is to take account of rudder effect.
The load of the full scale propeller is obtained
from
K
J
=
S
.
C
T
TS
2 2D
2
1
TS
( 1 − t)( − w ) 2
2
With this K T
/ J as input value the full
scale advance coefficient J TS and the torque
coefficient K QTS are read off from the full scale
propeller characteristics and the following
quantities are calculated
- the rate of revolutions:
F
n
S
( − w )
TS
VS
= 1 (r/s)
J D
TS
- the delivered power:
K
5 3 QTS −3
PDS
= 2πρ D nS
10 (kW)
η
- the thrust of the propeller:
K
T 2 4 2
TS
= . J . .
2 TS
ρ D nS
(N)
J
- the torque of the propeller:
KQTS
5 2
QS
= ρD
nS
: (Nm)
η
R
- the effective power:
3 −3
PE = CTS1/
2ρ . VS
. S.10
(kW)
- the total efficiency:
PDS
η
D
=
P
- the hull efficiency:
1 − t
η
H
= 1 − w
E
TS
2.4.4 Model-Ship Correlation Factors
Trial prediction of rate of revolutions and delivered
power with C P - C N corrections
if CHOICE=0 the final trial predictions will be
calculated from
n T = C N .n S
R
(r/s)
for the rate of revolutions and
P DT = C P .P DS (kW)