Write your message
   [Home ] [Archive]    
:: Main :: About :: Current Issue :: Archive :: Search :: Submit :: Contact ::
:: Volume 1, Issue 1 (5-2017) ::
ijcoe 2017, 1(1): 9-16 Back to browse issues page
The Effect of Shifting Natural Frequency on the Reduction of Vortex-Induced Vibrations of Marine Risers
Younes Komachi, Said Mazaheri , Mohammadreza Tabeshpour
Ocean Engineering and Technology Research Center, National Institute for Oceanography
Abstract:   (2119 Views)

Many procedures suggest for reduction of responses of riser to Vortex Induced Vibrations (VIV). Natural frequencies of marine risers is an important parameter that can affect the responses of riser to VIV. Change of riser properties such as top tension and bending stiffness can alter natural frequencies. In this study effects of riser specifications on the responses and fatigue damage of marine risers were investigated analytically and numerically. For numerically analysis 2D wake-structure coupled model is used for modeling of VIV of riser in two directions of Cross Flow (CF) and In Line (IL). The wake dynamics, including IL and CF vibrations, is represented using a pair of non-linear Van der Pol equations that solved using modified Euler method. The Palmgren–Miner Rule is used for evaluation of fatigue damage. Riser of Amir-Kabir semisubmersible placed in Caspian sea is used for case study. Because VIV is self-limiting, it is showed that lower modes have lower curvature, that in some cases this is lead to lesser stress and also fatigue damage. The results show that for tension dominant modes of vibration, natural frequencies was increased with top tension and for a certain Strouhal frequency, dominant modes of vibration was reduced which leads to reduction of stress and fatigue damage. The results show that stress and fatigue damage increased with module of elasticity of riser and reduction of this leads to reducing of stress and fatigue damage. Therefore suitable procedure for reduction of VIV responses of riser should be selected based on the current velocity.

Keywords: VIV, Wake oscillator model, Finite Element Method, Shifting frequency
Full-Text [PDF 775 kb]   (1519 Downloads)    
Type of Study: Research | Subject: Offshore Engineering
Received: 2016/04/30 | Accepted: 2017/03/9 | Published: 2017/05/10
1. Griffin, O.M., and Ramberg, S.E., (1982), Some recent studies of vortex shedding with application to marine tubular sand risers. ASME Journal of Energy Resource Technology Vol.104, p.2–13.
2. Bearman, P.W., (1984), Vortex shedding from oscillating bluff bodies. Annual Review of Fluid Mechanics Vol.16, p.195–222.
3. Parkinson, G., (1989), Phenomena and modeling of flow-induced vibrations of bluff bodies. Progression Aerospace Sciences Vol.26, p.169–224.
4. Sarpkaya, T., (2004), A critical review of the intrinsic nature of vortex-induced vibrations, Journal of Fluids and Structures 1Vol.9, p.389–447.
5. Williamson, C.H.K., and Govardhan, R., (2004), Vortex-induced vibrations, Annual Review of Fluid Mechanics, Vol.36, p.413–455.
6. Bearman, P.W., (2000), Developments in Vortex Shedding Research, Workshop on Vortex-Induced Vibrations of Offshore Structures. Sao Paulo, Brazil.
7. Wanderley J.B., and Levi, C., (2005), Vortex induced loads on marine risers, Ocean Engineering Vol.32, p.1281–1295.
8. Khalak, A., and Williamson, C.H.K., (1996) Dynamics of a hydroelastic cylinder with very low mass and damping. Journal of Fluids and Structures, Vol.10, p.455–472.
9. Steger, J.L., and Warming, R.F, (1979), Flux vector splitting of invicid gas dynamic equations with application to finite difference method. NASA. TM-78605.
10. Favre, A., (1965) Equations des gaz turbulents compressibles: 1 Formes Ge´ne´rales. Journal of Mechanics, Vol.4, p.361–390.
11. Jones W.P., and Launder, B.E., (1997), The prediction of relaminarization with a two-equation model of turbulence, International Journal of Heat and Mass Transfer, Vol.15, p.301-314.
12. Goldberg, U.C., (1986), Separated flow treatment with a new turbulence model, AIAA Journal, Vol.24(10), p. 1711-1713.
13. Houzeaux, G., and Codina, R., (2003), A chimera method on a Dirichlet/Neumann (Robin) coupling for the Navier—Stokes equations. Computational Methods Application and Mechanical Engineering, Vol.192, p.3343–3377.
14. Herfjord, K., (1995), A study of two-dimensional separated flow by a combination of the finite element method and Navier–Stokes Equations, Dr. Eng. Theses, The Norwegian Institute of Technology, Trondheim, Norway.
15. Tritton, D.J., (1959), Experiments on the flow past a circular cylinder at low Reynolds number, Journal of Fluid Mechanics, Vol.6, p.
Send email to the article author

Add your comments about this article
Your username or Email:


XML     Print

Download citation:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:

Komachi Y, Mazaheri S, Tabeshpour M. The Effect of Shifting Natural Frequency on the Reduction of Vortex-Induced Vibrations of Marine Risers. ijcoe. 2017; 1 (1) :9-16
URL: http://ijcoe.org/article-1-24-en.html

Volume 1, Issue 1 (5-2017) Back to browse issues page
International Journal of Coastal and Offshore Engineering International Journal of Coastal and Offshore Engineering
Persian site map - English site map - Created in 0.09 seconds with 33 queries by YEKTAWEB 4130