In the article [4], the authors have clarified that the hypercircle method is useful for estimating the added mass of two-dimensional cylinders with a rectangular or triangular section when vibrating in the horizontal direction very slowly. In this paper, the added mass of a rectangular cylinder floating on the surface of water and vibrating in the horizontal or vertical direction with a very high frequency is calculated by the same method also for the purpose of investigating the effect of the restricted waterway on the added mass.
As the result, it is concluded that the clearance between the side wall of the waterway and the nearer side wall of the cylinder has a considerable effect on the horizontal added mass, while the vertical added mass is affected remarkably by the clearance of water under the bottom of the body.