RIFLEX

RIFLEX is a FEM program for static and dynamic analysis of slender marine structures. Complex cluster configurations and non-linearities can be modelled. 

• Nonlinear finite element program
• Time domain simulation of riser motion and forces
• Nonlinear cross section properties
• Simplified input for standard systems
• Riser bundles, connected risers
• Simple analysis options for parametric studies
  - Catenary static analysis
  - Linearized dynamic analysis

RIFLEX is a tailor-made computer program system for static and dynamic analysis of flexible riser systems.

User friendliness is achieved by taking advantage of the simple geometry of flexible risers which allows for very simple input/output specifications and automatic mesh generation. Special input/output specifications are available for standard riser systems such as the Free Hanging, Steep Wave, Lazy Wave, Steep S and Lazy S configurations. Several alternatives are available for static and dynamic analyses from very simple methods which are useful in the early stage design, to advanced 3-D analyses of arbitrary flexible riser systems.

General features

• Flexible modeling of simple as well as complex riser systems including connected systems and riser bundles.
• Finite element formulation allowing for unlimited displacements and rotations in 3-D space.
• Beam and bar elements
• Nonlinear material properties including a hysteritic material description
• Nonlinear static finite element analysis
• Nonlinear time domain dynamic analysis

Load models

• External/internal hydrostatic pressure described by the effective tension concept
• Hydrodynamic loading described by the generalized Morison's equation
• Forced support motion due to one or several support vessels
• System loading due to regular or irregular waves and vessel motions
• Arbitrary current profiles
• Seafloor friction

Features for simplified analysis

• Simplified input specifications for standard systems
• Static parameter variation, i.e. system behavior is studied by variation of vessel position, current profile and specified forces.
• Linearized time domain analysis by linearization of mass, damping and stiffness matrices at static position. Nonlinearities in external hydrodynamic loading are, however, included.
• Frequency domain analysis by stochastic linearization of the hydrodynamic loading (under implementation per 92.02.01)

• Efficient static finite element analysis of the standard systems utilizing the catenary start configuration.
• Connector element for modeling of swivels and hinges
• Arbitrary boundary conditions at supports
• Identification of contact problems
• Special options available: Restart, release/rupture
• Loading due to internal slug flow

The RIFLEX program system is built up of five separate programs. INPMOD, STAMOD, DYNMOD and OUTMOD are batch oriented programs, while PLOMOD is an interactive program for design and analysis of flexible risers are also available.

Development project

The RIFLEX program has been developed by MARINTEK and SINTEF in cooperation with the Norwegian University of Science and Technology (NTNU) as a joint industry project. The following companies have participated:

• BP Petroleum Development
• Conoco Norway
• Esso Norge
• Norsk Hydro
• Saga Petroleum
• Statoil

Program documentation comprises:

• General description
• User Manual
• Theory manual
• Test manual
• Maintenance manual 

RIFLEX is developed and maintained by MARINTEK, - marketing and sale is handled by DNV Software (http://www.dnv.com/software)

RIFLEX product pamphlet in PDF format.

For more information please contact: Div. Offshore Structures