VIVA is a vortex induced vibration (VIV) analysis software that to date has not been widely used as a design tool in the offshore oil and gas industry. VIVA employs a hydrodynamic database that has been benchmarked and calibrated against test data [1]. It offers relatively few input variables reducing the risk of user induced variability of results [2]. In addition to cross flow current induced standing wave vibration, VIVA has the capability of predicting traveling waves on a subsea riser, or a combination of standing and traveling waves. Riser boundary conditions including fixed, pinned, flex joint or SCR seabed interaction can be modeled using springs and dashpots. VIVA calculates riser natural frequencies and mode shapes and also has the flexibility to import external modal solutions. In this paper, the applicability of VIVA for the design of straked steel catenary risers (SCR) and top tensioned risers (TTR) is explored. The use of linear and rotational springs provided by VIVA to model SCR soil interaction and flex joint articulation is evaluated. Comparisons of the VIV fatigue damage output with internal and external modal solution is presented in this paper. This paper includes validation of the VIVA generated modal solution by comparing the modal frequencies and curvatures against a finite element (FE) model of the risers. Fatigue life is calculated using long term Gulf of Mexico (GoM) currents and is compared against the industry standard software SHEAR7. Three different lift curve selections in SHEAR7 are used for this comparison. The differences in riser response prediction by the two software tools are discussed in detail. The sensitivity of the VIVA predicted riser response to the absence of VIV suppression devices is presented in this paper. The riser VIV response with and without external FE generated modal input is compared and the relative merits of the two modeling approaches are discussed. Finally, the recommended approach for VIVA usage for SCR and TTR design is given.Copyright © 2010 by ASME
[1]
Halvor Lie,et al.
Experimental investigation of vortex-induced vibration of long marine risers
,
2005
.
[2]
Rolf Baarholm,et al.
Effect of Marine Growth on an Elastically Mounted Circular Cylinder
,
2008
.
[3]
Franz S. Hover,et al.
VIV Hydrodynamic Data Extraction From Field Data
,
2009
.
[4]
Carl M. Larsen,et al.
Time and Frequency Domain Analysis of Catenary Risers Subjected to Vortex Induced Vibrations
,
2006
.
[5]
Rolf Baarholm,et al.
Modelling and Characterization of Artificial Marine Growth
,
2008
.