Powering Data - Resistance and Propulsion

Name

This is NOT editable, it is simply included here as an aid to you when entering data.

Resistance Method

Select the appropriate prediction method from the list.

Use Ratios

If you wish to incorporate a set of resistance ratios calculated previously, then the Use Ratios check box should be checked.

Note:
Unlike previous versions of Hydro, a different ratio file may be specified and used for each loading condition.

Ratios FileName

If the Use Ratios box is checked, then you should select a file. By clicking in this field, a File Open dialog is displayed allowing you to select the ratio file. The name is then entered into the cell. Note that the file name may not be directly entered.

The structure of the ratios file is given in .

Because the resistance ratios are calculated for all resistance methods, the calculated ratios may not be particularly reliable for some of the resistance methods and, in fact, may not even be calculated for others. Therefore, when incorporating a set of resistance ratios into a powering prediction, care should be taken to ensure that the resistance method chosen is applicable to the current hullform and that the resistance ratios in the chosen ratio file are sensible numbers (around 0.8 - 1.5). The resistance ratio file can be viewed as a text file. However, the file is in a fixed format, so editing of the ratio file is strongly discouraged.

Propulsion Factors

Select the appropriate prediction method from the list. If the User Input option is chosen, then the following three entries become available (and are assumed constant across the speed range), otherwise they are disabled, since the values are calculated automatically.

w

Wake fraction.

t

Thrust deduction fraction.

etar

Relative rotative efficiency.

Ship/Model Correlation

Select the appropriate prediction method from the list of two. The Ca x 1000 cell is only enabled if the User Input option is chosen. If Holtrop & Mennen is chosen it must be ensured that all relevant hullform parameters are supplied, as specified on the Powering Data - Loading Conditions page.

Ca x 1000

Ship/model correlation value.

Wake Correction

Select the appropriate prediction method from the list of three

• ITTC 1978 method (including FFC) - default option.

• ITTC 1978 method (excluding FFC).

• No wake correction.