Introduction to Offshore Structure Analysis in Abaqus AQUA

Overview
Abaqus AQUA is a specialized module within the SIMULIA Abaqus finite element analysis software that provides capabilities for analyzing offshore structures subjected to environmental loads from waves, currents, and wind. This module is particularly valuable for the oil & gas and renewable energy industries when designing and assessing platforms, pipelines, risers, and other marine structures.

Key Features of Abaqus AQUA

1. Wave Loading Capabilities:
Regular (Airy) wave theory
Stokes’ higher-order wave theories
Stream function wave theory
User-defined wave spectra (Pierson-Moskowitz, JONSWAP, etc.)

2. Current Modeling:
Uniform current profiles
Shear current profiles
Combined wave-current loading

3. Hydrodynamic Load Calculation:
Morison’s equation implementation
Drag and inertia forces
Relative velocity formulation

4. Structural Components Supported:
Jacket structures
Risers and pipelines
Mooring lines
Floating platforms
Subsea equipment

5. Load Application:
Apply AQUA loading to structural members
Combine with other loads (gravity, topside loads, etc.)

6. Analysis Types:
– Static analysis for extreme environmental conditions
– Frequency domain analysis for fatigue assessment
– Time domain analysis for dynamic response

Applications

Abaqus AQUA is commonly used for:
Offshore platform design verification
Riser and pipeline analysis
Mooring system design
Floating structure analysis
Wave load calculations for wind turbine foundations
Structural integrity assessments under extreme weather conditions

The module integrates seamlessly with Abaqus/Standard and Abaqus/Explicit, allowing for comprehensive static and dynamic analyses of offshore structures in harsh marine environments.

In this case, a steel riser is considered a structure that interacts with both water and air. The current is considered in the X direction with a velocity of 0 at the seabed and 0,8m/s at the free surface of the water. Two wave models with different heights, lengths, and angles are also selected. The drag load is applied to the section of the structure that is outside the water