Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 12165:1987 is the Indian Standard (BIS) for guidelines for estimation of current forces on marine structures. 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.
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Coastal and Marine Engineering
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
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.
API RP 2A-WSD, 22nd EditionAmerican Petroleum Institute (API), USA
HighCurrent
Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms—Working Stress Design
Both provide methodologies for calculating environmental forces, including currents, on fixed offshore structures using Morison's equation.
ISO 19902:2020International Organization for Standardization (ISO), International
HighCurrent
Petroleum and natural gas industries — Fixed steel offshore structures
Represents the modern, comprehensive global standard for fixed structures, including detailed current force calculation procedures.
DNV-RP-C205 (2021)Det Norske Veritas (DNV), Norway
MediumCurrent
Environmental conditions and environmental loads
Focuses specifically on the detailed characterization and modeling of environmental loads, including currents, for marine structures.
BS 6349-1-1:2013British Standards Institution (BSI), UK
MediumCurrent
Maritime works. General. Code of practice for planning and design for operations
Provides general design principles for maritime works, including a section on loads from waves and currents, albeit less specialized than API or ISO.
Key Differences
≠IS 12165 provides simplified, constant values for drag (Cd) and inertia (Cm) coefficients, whereas modern standards like ISO 19902 and DNV-RP-C205 specify coefficients that vary with Reynolds number (Re), Keulegan-Carpenter (KC) number, and surface roughness.
≠The Indian standard suggests simplified current profiles (e.g., 1/7 power law). International standards mandate the use of more sophisticated, often site-specific profiles that distinguish between tidal, wind-driven, and other current components.
≠IS 12165 has very limited guidance on wave-current interaction, generally suggesting simple vector addition. Modern codes like ISO 19902 provide detailed procedures for modifying wave kinematics (stretching, Doppler effect) in the presence of current.
≠IS 12165 focuses on static or quasi-static forces. International standards place significant emphasis on dynamic effects, such as Vortex-Induced Vibrations (VIV), and provide detailed methodologies for their analysis and mitigation.
Key Similarities
≈All standards use Morison's equation as the fundamental basis for calculating wave and current forces on slender cylindrical members.
≈The core principle of combining a velocity-squared drag component and an acceleration-proportional inertia component is common to IS 12165 and all its international counterparts.
≈All standards recognize the importance of accounting for marine growth, which increases the effective diameter, weight, and surface roughness of structural members.
≈The basic methodology of vectorially adding the current velocity to the wave particle velocity before calculating the drag force is a shared concept, even if the implementation details differ.
Parameter Comparison
Parameter
IS Value
International
Source
Drag Coefficient (Cd) for smooth cylinder (post-critical Re)
1.2 (constant)
~0.65-0.7 (dependent on Re and roughness)
DNV-RP-C205
Inertia Coefficient (Cm) for smooth cylinder
2.0 (constant)
Variable, typically 1.6-2.0 depending on KC number
API RP 2A-WSD
Default Current Profile Model
Power law profile with 1/7 exponent, V(z) = Vs * (z/d)^(1/7)
Separate profiles for near-surface (wind), full-depth (tidal), and combined using logarithmic or power law with site-specific exponents.
ISO 19902
Guidance on Shielding/Interference
Not explicitly covered in detail.
Detailed factors are provided to modify coefficients for members in the wake of or adjacent to other members.
ISO 19902
Consideration of Wave-Current Interaction
Simple vector addition of velocities.
Requires modification of wave period (Doppler shift) and stretching of kinematics to the instantaneous free surface.
DNV-RP-C205
Vortex-Induced Vibration (VIV) Analysis
Mentions the phenomenon but provides no detailed calculation procedure.
Mandatory screening and detailed fatigue analysis procedures required if critical velocities are exceeded.
DNV-RP-C205
⚠ Verify details from original standards before use
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
Tables & Referenced Sections
Key Tables
Table 1 - Values of Drag Coefficient Cd for a Smooth Circular Cylinder in a Uniform Steady Flow
Table 2 - Drag Coefficients for Flat Plates and Structural Shapes
Table 3 - Roughness Values for Various Types of Marine Growths
Key Clauses
Clause 4 - Types of Currents
Clause 5 - Current Velocity Profile
Clause 6 - Estimation of Current Forces
Clause 7 - Effect of Marine Growth
Frequently Asked Questions3
What is the main formula for calculating current force?+
The drag force is Fd = 0.5 * ρ * Cd * A * V², where ρ is water density, Cd is drag coefficient, A is projected area, and V is current velocity (Clause 6.1).
How does marine growth impact the force calculation?+
Marine growth increases the effective diameter of the member (increasing Area 'A') and increases the surface roughness, which typically increases the drag coefficient 'Cd' (Clause 7).
What is the difference between drag and lift force on a structure?+
Drag force acts parallel to the direction of current flow, while lift force acts perpendicular to the flow direction, often caused by vortex shedding (Clause 6.1 and 6.2).