PE Pipe Technical Catalogue (PDF) - Pipelife Norge AS

Pipelife Norge ASPE CATALOGUE-SUBMARINE APPLICATIONS, PIPELIFE NORGE AS, December 2002.C LR eFig. A.4.5.3 Lift coefficient, C LThe lifting force will be reduced as the distance (f) between pipe and seabed increases.If f = 0.5 ⋅D the lifting force will be approximately 10% of the lifting force for a pipeline laying directlyon the seabed. This is a vital detail in design of concrete weights.Example 4A current is attacking a pipeline at an angle 45ºfrom the centreline as shown beside.V= 1 m/sThe pipe's diameter is 500 mm.Density of water is 1000 kg/m 3 .Assume that C L = 0.20 and C D = 1.0.Calculate the drag force and the lift force.Solution :The velocity component perpendicular to the pipelinecan be written :α = 45 oD= 500mmv N = v ⋅ sin αA.4-13)Inserting this expression into A.4-10) and A.4-11) we get :F D =1 2 2C D ⋅ ⋅ ρ ⋅ v ⋅ sin α ⋅ D2A.4-14)F L =1 2 2C L ⋅ ⋅ ρ ⋅ v ⋅ sin α ⋅ D2A.4-15)Putting in values from example 4 gives :F D =12 21.0 ⋅ ⋅1000⋅1⋅ sin 45 ⋅ 0.5 N/m = 125 N2F L =12 20.2 ⋅ ⋅1000⋅1⋅ sin 45 ⋅ 0.5 N/m = 25 N2Side 57 av 84