Hence, fatigue damage and VF due to in-line VIV is important from the TDP to most parts of the UR on the VRR irrespective of the wave spectra and requires proper analysis in riser designs. The results for both spectra showed zero in-line VF on the VRR at 23.69m, 26.21m and End B (31.031m). Whereas, for the Ochi-Hubble spectra, VF range, from TDP to the UR, of 0.16 - 0.302kN/m 0.018 - 0.56kN/m 0 - 1.42kN/m at End A (0m) 8.74m and 21.00m, respectively, were obtained. Also, the in-line vortex force (VF) analysis on the VRR for the JONSWAP spectra showed VF range, beginning from the touchdown point (TDP) to the unstraked region (UR), of 0.16 - 0.34kN/m 0.01 - 0.53kN/m and 0 - 0.85kN/m at End A (0m) 8.74m and 21.00m, respectively. The results from the Ochi-Hubble spectra indicate a fatigue damage value of 96.2 x 10 -5 due to in-line VIV which is greater than 7.03 x 10 -5 due to transverse VIV.
Orcaflex theory manual manual#
7ANSYS.AQWA User Manual V14.5Z.2015 8OCINA.Orcaflex User Manual 9.8aZ.2015. The results from JONSWAP spectra showed a fatigue damage value of 102.5 x 10 -5 due to in-line VIV which is greater than 29.1 x 10 -5 due to transverse VIV. 6MORIARTY P J,COLORADO G,CRAIG H A.Aero Dyn Theory ManualR.National Renewable Energy Laboratory,2005. The process was statically and dynamically simulated using different wave spectra on Orcaflex platform.
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In this paper, a typical VRR of 31.031m length clamped to a fixed jacket platform in 18.29m water depth was used while relevant metOcean data were used to simulate the environmental conditions. Figure: OrcaFlex line model: The line is divided into a series of line segments which are then modelled by straight massless model segments with a node at each end. In-line and Transverse Vortex Induced Vibrations (VIV) pose potential Fatigue damage threat to Vertical Rigid Risers (VRR) even in the less volatile Nigeria Shallow Waters. Line theory: Overview: OrcaFlex uses a finite element model for a line as shown in the figure below.