APPENDIX E 



INTERNATIONAL TOWING TANK CONFERENCE 1957 

 MODEL-SHIP CORRELATION LINE 



Meeting in London in 1948, the ITTC* agreed that in future published work the extrapo- 

 lation of model resistance results to estimate resistance and power for the ship would be 

 carried out by using either the Froude coefficients or the ATTC 1947 line, the latter being 

 based upon the work of Schoenherr. In using this latter line, a ship correlation allowance is 

 usually made of +0.0004 on C p. 



The 1948 Conference also set up a Skin Friction Committee which was instructed, 

 inter alia, "to survey the problem of skin friction in general, and in particular to recommend 

 what further research should be carried out to establish the minimum turbulent friction line 

 for both model and ship use.* 



This committee finally reported to the 8th ITTC in Madrid in 1957, making two alter- 

 native proposals. Both were designed to increase the slope of the ATTC line at the low 

 values of Reynolds number associated with the use of small ship models while giving values 

 close to the ATTC line at high Reynolds numbers. One of these proposals was, in effect, 

 adopted by the Conference, which decided that "the line given by the formula 



C/ = 



0.075 



Oogio«.-2)' 



is adopted as the ITTC 1957 model-ship correlation line, it being clearly understood that this is 

 to be regarded only as an interim solution to this problem for practical engineering purposes." 



Tables of values of C^r derived from this formula have been given at .various times 

 (see for example Reference 72), and the differences between them and those represented by 

 the ATTC 1947 line can be illustrated by the following figures: 



loglO ^n 



Val 



ues of C p X 10^ 



ATTC 1947 

 Line 



ITTC 1957 

 Line 



Difference 



6.0 



4.410 



4.688 



+ 0.278 



7.0 



2.934 



3.000 



+ 0.066 



8.0 



2.072 



2.083 



+ 0.011 



9.0 



1.531 



1.531 



1 



10.0 



1.173 



1.172 



-0.001 J 



♦Then called the "International Conference of Ship Tank Superintendents." 



E-1 



