A New Appraisal of Strip Theory- 

 made with regard to some apparent inconsistencies in the Korvin-Kroukovsky 

 analysis, there is reason to believe that certain modifications and corrections 

 can be made which will generally improve the procedure and render it more 

 useful. 



It is important to note that the prime objective of the authors' research ef- 

 fort is to ascertain the importance of seaworthiness considerations in prelimi- 

 nary design. Since, however, strip theory of all suggested theoretical approaches 

 had been brought closest to practical application, the decision was made that it 

 was the most appropriate building block upon which to erect further structure. 

 This report constitutes the authors' thoughts as to the accuracy of the strip 

 theory as currently understood and suggestions for improvements. 



HISTORICAL NOTES 



The earliest and least refined version of strip theory was presented in Ref. 

 [8], where the authors essentially amplified the studies of Kriloff, Weinblum, St. 

 Denis and other pioneers in the field of ship oscillations. The major advance- 

 ment in Ref. [8] was the inclusion of some of the cross-coupling coefficients in 

 the equations of motion. The first complete presentation of the procedure fol- 

 lowed in 1955 [9] and was subsequently corrected and improved two years later 

 [10]. In this effort, various discussers of Ref. [10] and in particular Kaplan [11] 

 and Abkowitz [12] were instrumental in pointing out certain mistakes of the 1955 

 exposition, while Fay's analysis [13] motivated a more accurate definition of the 

 velocity dependent terms in the equations of motion. Finally, Jacobs [14] at the 

 suggestion of several discussers of Ref. [9] presented a more precise expres- 

 sion for the exciting force (and moment) and hence extended the procedure to the 

 analytical calculation of ship bending moments, as a result of which a unified 

 computational approach was outlined in [5]. The most recent discussion on the 

 coefficients of the equations of motion and excitation terms appears in Ref. [15], 

 whereas for a complete summary of the whole problem as it was understood by 

 Korvin-Kroukovsky the interested reader is referred to Ref. [4]. 



Since the appearance of Ref. [6], the inclusion of hull-shape nonlinearities 

 was achieved by Parissis [16]. This latter work represents a further refinement 

 of strip theory and provides, with the aid of Kerwin's polynomial hull represen- 

 tation [17], some interesting answers with regard to the validity of linearity and 

 effect of hull-shape non-linearities on ship responses. Although this quasi- 

 nonlinear work is valuable in its own right, it is of no direct use in statistical 

 analysis which is solidly tied to linear systems. 



STRIP THEORY VERSUS EXPERIMENT 



The first objective of the investigation reported in Ref. [6] was to attempt 

 to assess the accuracy of the strip theory in the form it existed at the time of 

 writing, Ref. [5]. This was accomplished by correlating theoretical computa- 

 tions to experimental data published by the Netherlands Ship Model Basin in 

 Refs. [18] and [19]. The results reported in the latter publications were chosen 

 as the main source for the comparison attempt because they contained the most 



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