|
Open-water test: [Data file]
[Performance Curve: eps | tif ]
|
In order to perform the self-propulsion computation, following three computations are required:
The self-propulsion computation is to be carried out at the ship point following the experimental procedure, i.e., the rate of propeller revolution is adjusted in such a way that the propeller thrust is balanced with the extrapolated full-scale resistance of the ship as follows:
where is the total resistance of the ship in the self-propelled condition. is the skin friction correction and is defined as
| ||
is the form factor and
| ||
(ITTC '57 frictional coefficient of the model scale, ) | ||
(ITTC '57 frictional coefficient of the full scale, ) | ||
is the roughness allowance and set to be
| ||
Figure Number | Items | Remarks |
---|---|---|
Integral variables: <towed> Form factor ( 1 + k ) at Fn = 0 Coefficients of total resistance (CT(Tow)), split into pressure (CP(Tow)) and friction (CF(Tow)) components at Fn = 0.26, Nominal wake coefficient ( 1 - w n ) <self-propelled> Coefficients of total resistance (CT(SP)), split into pressure (CP(SP)) and friction (CF(SP)) components, Propeller thrust coefficient ( KT ), Propeller torque coefficient ( KQ ), Thrust deduction coefficient ( 1 - t ), Effective wake coefficient determined from thrust identity method ( 1 - wT ), Propeller open water efficiency ( ηo ), Relative rotative efficiency ( ηR ), Advance ratio of propeller determined from thrust identity method ( J ), Propeller rate of revolution ( n [rps] ), Propulsive efficiency ( η ) |
Experimental results table |
|
Fig. 2-1 | Axial velocity contours and cross flow vectors downstream of propeller
plane (x/Lpp=0.4911) |
download |
Fig. 2-2 | Velocity downstream of propeller plane (x/Lpp=0.4911) at z/Lpp=-0.03 | To be compared with the experimental results download |
Fig. 2-3 | Uncertainty analysis of the above item | UD = 5 % ( Proceedings of CFD Workship 2000 ) |
Fig. 2-4 | Hull surface pressure contours ( port side view ) | download |
(ITTC 1957 frictional coefficient line ) |
Roughness allowance | |
Diameter of propeller | |
Diameter of a propeller hub, | |
Advance ratio | |
By using the propeller thrust at the self propulsion test, the thrust identity method gives the corresponding advance ratio from the open water characteristics. | |
Thrust coefficient, | |
Torque coefficient, | |
Torque coefficient in open water ( uniform flow ) | |
By using the propeller thrust at the self propulsion test, the thrust identity method gives the corresponding open water torque from the open water characteristics. | |
Propeller rate of revolution [rps] | |
Propeller torque | |
Total resistance in towed condition | |
Total resistance in self-propelled condition | |
Skin friction correction | |
Propeller thrust | |
Thrust deduction factor, | |
Ship speed | |
Propeller advance speed, determined by the thrust identity method, | |
nominal wake | |
where the origin is the center of propeller (see Figure) | |
Taylor wake fraction, | |
Propulsive efficiency, | |
Propeller open water efficiency, | |
Relative rotative efficiency, |