How to divide the global resistance change into the components related to the pushing propeller and the pulling propeller of the double-ended ship
The division of the global resistance change ∆RR+D due to the simultaneous action of the pushing (SR) and pulling (SD) screw propellers into the components ∆RR and ∆RD can be done by taking into account two different procedures and different hypothetical assumptions given in the form of the division coefficients (Aj)R and (Aj)D, the same in each procedure.
In the procedure no 1: ∆RR = ∆RR+D(Aj) and ∆RR = ∆RR+D(Aj)Dj
In the procedure no 2: ∆RR = TR – (R0– FD) (Aj)R and ∆RD = TD – (R0– FD) (Aj)D
Two necessary conditions were formulated to be fulfilled when selection of the coefficients (Aj)R and (Aj)D is done. The results of the analysis are univocal. Among the possible division coefficients only one pair of them fulfills the formulated conditions. This pair is:
(A1)R=TR/TR+D and (A1)D=TD/TR+D
Keywords:self propulsion tests, double-ended ships, resistance change due to propeller action
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