Cd & Cm for square section legs
Cd & Cm for square section legs
(OP)
Hi guys,
anyone got a reference for Cd & Cm for square section legs for a small jack up rig ?
Thanks.
anyone got a reference for Cd & Cm for square section legs for a small jack up rig ?
Thanks.





RE: Cd & Cm for square section legs
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RE: Cd & Cm for square section legs
For Morrison's Equation (without motion):
You can reference API Recommended Practice 2A (either WSD or LRFD) for a table with such factors. "C.3.2.10 Morison Equation"
where
Cm- inertia coefficent
Cd- drag coefficent
Values appropriate for the case of a steady current with negligible waves or the case of large waves with Umo*Tapp>30
Umo- maximum horizontal particle velocity at storm mean water level (2D , not diffraction)
Tapp- Apparent Wave Period
D- platform leg diameter
smooth Cd=0.65, Cm=1.6
rough Cd=1.05, Cm=1.2
If <30 than you need to modify with wake encounter
What type of project is this? I will answer anyones question with hard facts as long as they are honest and detailed about the purpose for the calculations.
RE: Cd & Cm for square section legs
Ciria Underwater Engineering Group: Report UR8, Dynamics of Marine Structures: Methods of calculating the dynamic response of fixed structures subject to wave and current action..
pg.152 Table 4.2 and Table 4.3
for a perfect square without rounded edges...
to be used with morison's equation (with or without motions)
Cd= 2.0, and Cm =2.5