波浪中における漁具の運動-I

Abstract

A series of experiments was performed to study the motion of freely floating bodies in still water, and apply the data acquired here to the study on the motion of fishing gear. The displacement from the equilibrium position with the lapse of time was recorded on a 35mm film with the aid of a stroboscope and was evaluated for the vertical oscillation. The configuration of the models used in the experiments were of three types; a circular cylinder, a circular cone and a sphere. The main problem was to describe the motion of a float with non-uniform cross section area. For the solution of this problem, an approximation was done by substituting the amount of change in sub-merged volume due to damped oscillation as a volume of a body with uniform cross section area. Accordingly, to use this approximation menthod, the constant coefficient in the equation of motion was calculated in every period, i. e. the equation was solved by means of the method of variable constant. The theoretical consideration was performed based on the experimental results of damped oscillation to examine the possibility of applying the theory for a circular cylinder to a circular cone and a sphere. Through the experimental results, it was ascertained that the theory for circular cylinder could be applied to a circular cone or a sphere for practical purposes.