stability of air-cushion supported body
does any one know how to calculate the center of buoyancy of a air-cushion supported body??? Hi liy02I am not quite family with air-cushion design, but your question appears a hydraulic static problem.
Buoyancy ( F ) is always equalizing the Gravity (G) , when the ship is stabile.
Archimedes find out the buoyancy is always related with volume submersed in fluid.
so you have the formula like G = F= pVg
Method one: To calculate the center of Gravity. (Center of gravity is the center of buoyancy)
- Build up the geometry. So you know total volume V of ship.
- Get the density of each part. So you have the p.Gravity is G = V x p
- Many softwares are able to calculate 3D geometry gravity position automatic, if you assume the density is even.
See thread: http://www.simwe.com/forum/thread-577585-1-1.html
Method Two: To calculate the center of Buoyancy.
- Buoyancy from volume submersed into water (F1). If you can measure the depth on air-cushion
- Buoyancy from volume submersed into air. ( F2) They are the rest of volume. Of course, This force is small.
- F1 + F2, Both forces apply on the ship body. The essential algorithmic is to combine the force on position and find out center. Hi liy02
I am not exacly right. Center of gravity is NOT the center of buoyancy.
The center of buoyancy is always moving, once the ship is not stable.
The centre is the ship submersed volume integrate the water weight.
To design a stable ship, The gravity centre need always below the buoyancy centre. thanks 斑竹 very much
in my case the COB is always higher than the COG
it is not stable all the time and as it tilts, the stability decreases
anyway, thanks for your help
i am sorry i can't tpye in chinese because i am in the office and the computer does not have chinese input COB, COG到底那个在上？我假设你说反了：
要是你的气室高比吃水小，就把气室当水箱，做稳性自由液面修正。
如你干LNG,PNG，你会发大财。
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