DNVGL-RP-F109 Shields Number Calculators

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DNVGL RP F109 Shields Number

Calculate DNVGL RP-F109 Shields number and critical velocity.

Shields number is the ratio of shear force to weight force and is used to estimate the onset of seabed movement for non cohesive soils. The critical velocity corresponds to to the onset of seabed movement.

Reference : DNVGL-RP-F109 : On-Bottom Stability Design Of Submarine Pipelines (Download from the DNVGL website)

Calculate the Shields number and critical wave or current velocity for seabed movement (DNVGL-RP-F109 section 4.4).

The Shields number is the ratio of shear stress to weight for sediment particles. Non cohesive sediment becomes unstable when the Shields number exceeds a critical value (approximately 0.04 for subsea waves and currents). The Shields number can be calculated for waves only, or for current only (combined wave and current is not valid).

Tool Input

roughtype : Seabed Roughness Type
- D50u : User Defined Particle Diameter
facttype : Critical Shields Parameter Type
- ϴcu : User Defined Critical Shields Number
wavetype : Friction Factor Type
Uc : Current Velocity
Uw : Wave Horizontal Velocity
T : Wave Period
ρb : Seawater Density
ρp : Particle Density

Tool Output

ϴ : Shields Parameter
ϴcr : Critical Shields Parameter
τ : Fluid Shear Stress
CVG : Convergence Factor
D50 : Mean Particle Diameter
Ss : Particle Relative Density
Ucr : Critical Fluid Velocity
fw : Friction Factor

DNVGL RP F109 Shields Number

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