For the regression analysis methods (all methods except analytical), the resistance and power are automatically calculated whenever a change is made to the input data. The analytical results can only be obtained after solving the analysis, see Using the slender Body Method on page 22 for more information.
A table with the calculation results will be tabulated in the Results window.
A graph of the results will appear in the Results Graph window.
Clicking on any of the curves in the graph will show the resistance and speed values at that point in the bottom left of the Graph window.
Double clicking on the graph will bring up a table with all the graph data points.
The type of graph displayed can be changed by selecting Graph Type from the Display menu.
As well as graphs of resistance or power, it is possible to plot the individual resistance coefficients.
Alternatively this can be done by selecting the required component from the pull-down list in the Graph toolbar:
Please note that not all methods calculate all the resistance components; many of the methods use the residuary + friction approach and hence the wave and viscous components cannot be derived. The following table summarises which components are calculated by each method.
|
Method |
RT |
RR |
RW |
RF |
RV |
RCor |
RApp |
RAir |
|
Savitsky pre-planing |
yes |
no |
no |
no |
no |
yes |
yes |
yes |
|
Savitsky planing |
yes |
yes |
no |
yes1 |
no |
yes |
yes |
yes |
|
Lahtiharju |
yes |
no |
no |
no |
no |
yes |
yes |
yes |
|
Holtrop |
yes |
yes |
yes2 |
yesITTC’57 |
yes |
yes3 |
yes |
yes |
|
Compton |
yes |
yes |
no |
yes ITTC’57 |
no |
yes |
yes |
yes |
|
Fung |
yes |
yes |
no |
yes ITTC’57 |
no |
yes |
yes |
yes |
|
van Oortmerssen |
yes |
yes |
no |
yes ITTC’57 |
no |
yes |
yes |
yes |
|
Series 60 |
yes |
yes |
no |
yes4 |
no |
yes |
yes |
yes |
|
Delft I, II |
yes |
yes |
no |
yes5 |
no |
no |
yes |
yes |
|
Delft III |
yes |
yes |
no |
yes5 |
no |
no |
yes |
yes |
|
Slender Body |
yes |
yes |
yes |
yes ITTC’57 |
yes6 |
yes |
yes |
yes |
Table notes:
|
1: |
The ATTC’47 (Schoenherr)
friction line is used, but a modified wetted surface area is used: |
|
2: |
The Holtrop wave resistance also contains the “bulb” and “transom” components |
|
3: |
The Holtrop method includes a regression equation for determining the correlation allowance coefficient; this is used rather than the user-specified value. |
|
4: |
Uses alternative friction line: |
|
5: |
Uses ITTC’57 friction line, but Reynolds Number is based on a shorter length: 0.7 LPP |
|
6: |
If the user specified form factor is negative, the slender body method uses the form factor as calculated by the Holtrop method. |
|
ITTC’57 |
Uses the ITTC’57 friction line: |
|
RT |
Total resistance; either expressed as: RT = RR + RF + RCor + RApp + RAir or RT = RW + RV + RCor + RApp + RAir |
|
RR |
Residuary resistance; total hydrodynamic resistance less skin friction resistance. Does not include RCor, RApp or RAir |
|
RW |
Wave resistance; resistance due to energy input into the generation of free surface waves. |
|
RF |
Friction resistance; skin friction of equivalent flat plate area, typically uses the ITTC’57 ship-model correlation line or Schoenherr friction line. |
|
RV |
Viscous resistance; skin friction viscous resistance plus allowance for 3D form effects of the hull. Typically by the use of a form factor (1+k). In this case RV = (1+k) RF |
|
RCor |
Correlation allowance resistance; additional resistance for correlation from model to ship scale |
|
RApp |
Appendage resistance; resistance of appendages such as rudder, etc. |
|
RAir |
Air resistance; wind resistance of above-water hull and superstructure |
