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Ship's Stabily

Ship stability is a complicated aspect of naval architecture which has existed in some form or another for hundreds of years. Historically, ship stability calculations for ships relied on rule-of-thumb calculations, often tied to a specific system of measurement. Some of these very old equations continue to be used in naval architecture books today, however the advent of the ship model basin allows much more complex analysis.

Master shipbuilders of the past used a system of adaptive and variant design. Ships were often copied from one generation to the next with only minor changes being made, and by doing this, serious problems were not often encountered. Ships today still use the process of adaptation and variation that has been used for hundreds of years, however computational fluid dynamics, ship model testing and a better overall understanding of fluid and ship motions has allowed much more in-depth analysis.

Transverse and longitudinal waterproof bulkheads were introduced in ironclad designs between 1860 and the 1880s, anti-collision bulkheads having been made compulsory in British steam merchant ships prior to 1860[1]. Prior to this, a hull breach in any part of a vessel could flood the entire length of the ship. Transverse bulkheads, while expensive, increase the likelihood of ship survival in the event of damage to the hull, by limiting flooding to breached compartments separated by bulkheads from undamaged ones. Longitudinal bulkheads have a similar purpose, but damaged stability effects must be taken into account to eliminate excessive heeling. Today, most ships have means to equalize the water in sections port and starboard (cross flooding), which helps to limit the stresses experienced by the structure, and also alter the heel and/or trim of the ship.

References

1. ^ Ship Stability. Kemp & Young. ISBN 0853090424

2. ^ a b c d Comstock, John (1967). Principles of Naval Architecture. New York: Society of Naval Architects and Marine Engineers. pp. 827. ISBN 670020738.

3. ^ a b Harland, John (1984). Seamanship in the age of sail. London: Conway Maritime Press. pp. 43. ISBN 0851771793.

4. ^ U.S. Coast Guard Technical computer program support accessed 20 December 2006.

7/23/2010

The Effect of Free Surface of liquids (FSE)


The Effect of Free Surface of liquids (FSE)

เมื่อเราปล่อยให้มีของเหลวที่สามารถเคลื่อนตัวได้อย่างอิสระภายในเรือ (ถังซึ่งบรรจุไม่เต็ม) การเคลื่อนตัวของผิวหน้าของของเหลวนั้นจะเกิดผลกระทบกับการเปลี่ยนแปลงตำแหน่งของจุด CG ของเรือ โดยจะทำให้จุด CG มีการเปลี่ยนแปลงเลื่อนขึ้นทางแนวดิ่งเสมอ (KG เพิ่มขึ้นเสมอ และทำให้ GM ลดลง) สามารถหาค่าดังกล่าวได้จากสูตร

When we left there. Fluid can move freely within the ship. ( tank containing Not a full) the movement of the liquid surface will affect the change. Position of the ship CG will cause the CG to change the vertical scroll up always (KG always up and down the GM) can get that value from the formula

The Effect of Free Surface of liquids (FSE)

The Effect of Free Surface of liquids (FSE)

Figure shows the effect of changing the cg fluid movement back and forth within the tank, which contained no full Affect the CG location and the ship

Reducing the impact of the Free Surface.

1 / add liquid to fill the tank. Or taken out up

2 / containers designed to be liquid water, the vertical wall of tank length. To reduce the impact.

3 / omissions fillingin the liquid in the tank position is very high.

จากรูปแสดงผลกระทบของการเปลี่ยนแปลงตำแหน่ง cg ของของเหลวที่เคลื่อนตัวไปมาภายในถังซึ่งบรรจุไม่เต็ม ส่งผลกระทบต่อตำแหน่ง CG รวมของเรือ

การลดผลกระทบจาก Free Surface คือ

1/ เติมของเหลวให้เต็มถัง หรือถ่ายออกให้หมด

2/ ออกแบบถังบรรจุของเหลวให้มีผนังกั้นน้ำทางแนวยาวของถัง จะลดผลกระทบลง

3/ ละเว้นการเติมของเหลวในถังที่มีตำแหน่งอยู่สูงมากๆ
ที่

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