This standard provides guidelines for calculating the forces exerted by ocean currents on marine and offshore structures. It covers different types of currents, velocity profiles, and presents formulas for calculating drag and lift forces, including the effects of marine growth.
Offers guidelines for estimating forces induced by currents on marine structures such as piles, platforms, and breakwaters.
Quick Reference Values
Density of sea water (ρ)1025 kg/m³
Drag Coefficient (Cd) for smooth cylinder, subcritical flow (Re < 5x10^5)1.2
Drag Coefficient (Cd) for smooth cylinder, supercritical flow (Re > 5x10^5)0.3
Drag Coefficient (Cd) for flat plate normal to flow1.9
Typical marine growth thickness for design50 mm to 150 mm
Key Formulas
Fd = 0.5 * ρ * Cd * A * V² — Drag Force
Fl = 0.5 * ρ * Cl * A * V² — Lift Force
Re = (ρ * V * D) / μ — Reynolds Number
Practical Notes
The selection of drag (Cd) and lift (Cl) coefficients is critical and highly dependent on the Reynolds number (Re), surface roughness, and proximity to other members.
Current forces must be evaluated in conjunction with wave forces, often using principles from Morison's equation, as simple superposition can be unconservative.
Always account for the variation of current velocity with water depth (current profile) as specified in Clause 5, rather than using a single average value.