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Tham khảo tài liệu 'ship stability for masters and mates 5 episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Calculating the effect of free surface of liquids FSE 199 The following worked example shows the effect of subdivisions in slack tanks in relation to free surface effects FSE Question A ship has a displacement of 3000 tonnes. On the vessel is a rectangular double-bottom tank 15 m long and 8 m wide. This tank is partially filled with ballast water having a density of 1.025 t m3. If the GMy without free surface effects is 0.18 m calculate the virtual loss in GMy and the final GMy when the double bottom tank has a no divisional bulkheads fitted b one transverse bulkhead fitted at mid-length c one longitudinal bulkhead fitted on T of the tank d two longitudinal bulkheads fitted giving three equal divisions. Answer h 15m bi 8m Fig. 20.4 a FSE virtual loss in GMy or rise in G - 1 w 1 X b3 X psw . _ _ . . TT TTf see Fig- 20.4 a 12 X w v s n . . . 15 X 83 X 1.025 . . virtual loss in GMy ------------ ------- --------- 3000 X 12 0.02187m t GMy finally 0.1800 - 0.2187 -0.0387m T i.e. unstable ship 200 Ship Stability for Masters and Mates l2 72 m 2 7Ỉ m 8m BHD Fig. 20.4 b FSE virtual loss in GMy or rise in G 2 @ l2 X b3 12 X w x Psw see Fig. 20.4 b . . 2 X 7.5 X 83 X 1.025 . . virtual loss -------------------- 12 X 3000 0.2187m t This is same answer as for part a . Consequently it can be concluded that fitting transverse divisional bulkheads in tanks does not reduce the free surface effects. Ship is still unstable _2 @ lyb - w Psw FSE vertical loss in GMy or rise in G . . virtual loss in GMy 2x 15 X 43 X 1.025 12 X 3000 see Fig. 20.4 c 0.0547 m I i.e. 2 of answer to part a Hence final GMy 0.1800 0.0547 m 0.1253 m Ship is stable. Calculating the effect of free surface of liquids FSE 201 GMt is now ve but below the minimum GMt of 0.15 m that is allowable by D.Tp. regulations. FSE virtual loss in GMt or rise in G 3 @ 11 X b3._ . . TX Psw see Fig. 20.4 d 12 X W . Virtual loss in GMt 3 X 15 X 8 X 1.025 _ 3 _ 12 X W 0.0243 m i.e. 1 of answer to part a Hence final .
