可浸長の簡易計算法

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Principal part of flooding calculation is divided into three parts. (1) To find the floodable volume so as to make the ship after flooding float at the trimmed water line which crosses the margin line only at one point. and the longitudinal position of its centre of volume. (2) With the given distribution of sectional area below that trimmed water line, to find the floodable length and the position of its middle point. (3) To find the end points of the floodable length curve. In this paper, the following methods are adopted to carry out these calculations. As an extension of the displacement calculation, at several parallel water lines between the load water line and deep water line. the volume above L.W.L. (ν), the distance of its centre of volume from midship (λ), the distance of the centre of flotation from midship, and the corresponding longitudinal metacentric radius (R) are calculated, and the profile between the L.W.L. and margin line with the locus of centre of flotation of even keel water line (I)(scale of depth being taken as ten times that of length), sectional area curve below margin line (II), and the plan area curve of margin line (III) are prepared. (1) Neg1ecting Leclert's correction. from the centre of flotation of an intermediate even keel water line between m.l. and L.W.L., two tangent lines (or lines through the end points of m.l.) are drawn towards fore part and aft part, and their inclinations α are measured. By virtue of the relation [numerical formula] tan α+λ (V_0 : vol. below L.W.L.) the longitudinal distance d of the centre of floodable volume ν from midship is calculated. (In this formula, d and α are assumed to be positive when referred to the fore part, λ being taken as positive for the centre of volume of layer ν allocated after midship.) The draft d_e of corresponding even keel water line is also noted. With the base of d, curves of ν (floodable volume curve) and of d_e (even keel draft curve) are drawn. (2) As for a certain value of d, the corresponding ν and d_e are read and with (I), through the centre of flotation corresponding to d_e, a tangent line to margin line is drawn. Now, d being : ssumed to be the first approximation to the position of the middle point of the floodable length, the sectional area A_m below margin line by (II), the height h_m between margin line and the tangent by (I), and the breadth b_m of the margin line plan area by (III) are taken at the position d, then the sectional area α_0 below the trimmed water line at d will be given by α_o=A_m-b_mh_m, and the first approximate value of the floodable 1ength 21 will be ν/α_o. By the same way, the sectional areas α_e and α_m at d±l can be obtained. Assuming the distribution of sectional area below the trimmed water line as a parabola of second order nearly within this range, the exact values of the floodable length L_F and the distance of its middle point from α_0 section E_f can be given by 2lL and 2le, in which L and e are taken from the diagram of Fig.4 with the given values of μ_e=α_e/α_0 and μ_m=α_m/α_0. (3) Through the centre of flotation of the even keel water line at about H/3 above L.W.L. (H being the distance between L.W.L. and margin line), two trimmed water lines are drawn, passing through the two end points of the margin line. At ξ≒(ship's length)/15,2ξ, 3ξ and 4ξ from both ends, the sectional areas below those trimmed water lines are calculated in the same way, as mentioned above, and by applying Simpson's first and second rules, the volumes, the longitudinal distances of their centres of volume from the ends, and the lengths corresponding to those volumes (i.e. 2ξ, 3ξ and 4ξ) up to 2ξ, 3ξ and 4ξ from ends are calculated. The values of volumes and their lengths are erected at the position of the centres of volume, and the curves (curve of end flooded volume and curve of end flooded length) are drawn. The intersection of the end flooded volume curve and the floodable volume cu
社団法人日本船舶海洋工学会の論文
1939-09-15

可浸長の簡易計算法

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