3b. Versuch RL i, Haufigkeitsverteilung der Schlingerperioden. 



Fig. 26 



Abb. ()a. Versuch II 41, Haufigkeitsverteilung der Wellenperioden, relative 

 Hiiufigkeit auf mm-Teilung. 



Fig. 27 



by Willi Langmaack-^ can be cited. In the pres- 

 ent connection the reference is of particular in- 

 terest in demonstrating the value of the "normal 

 distribution" method. As Dr. Jasper points out 

 in the early part of his paper, the Rayleigh distri- 

 bution is convenient in that it depends on a single 

 parameter E. While for many problems the re- 

 sultant common form of distribution is of value, 

 for others it may be of interest to bring out the dif- 

 ferences of existing conditions. In this particular 

 case the "normal distribution" brings out the 

 mean value of a quantity, and the spread of dis- 



^ "Haufigkeitsverteilung der Schwingungsperioden und ampli- 

 tuden eines Schifies in Seegang," by Willi Langmaack, Werft- 

 Reederei-Hafen, Heft 13, 1941, pp. 204-211. 



tribution about the mean value. This is illustrated 

 by Fig. 3(6) of the reference mentioned^^ (Fig. 26 

 of this discussion). The plot represents the fre- 

 quency distribution of roUing periods plotted 

 against the period. Two values of the maximum 

 frequency of occurrence can here be seen at the 

 periods of 10.7 and 26 sec, with the normal distri- 

 bution about each of these. This plot evidently 

 represents two superposed oscillations, the first at 

 the frequency of wave encounter and the second at 

 the natural frequency of ship's rolUng. A i exam- 

 pi^ of distribution of wave periods is shown on 

 Fig. 6(o), 25 (Fig. 27 of this discussion), where the 

 total motion is seen to be the result of three super- 

 posed wave trains. 



47 



