Showing 4 results for Riser
Mehdi Behzad, Hamid Salmasi, Siamak Kazemzade Hanani, Mohammad Saied Seif,
Volume 2, Issue 1 (3-2006)
Abstract
In this paper, several models of structure-fluid coupling are employed to investigate on the vibration behavior of the structure. Using basic equations of vibration and employing a mathematical model, a single degree of freedom system is analyzed. Some parameters of the mathematical model are obtained from test. To examine structure-flow interaction, coupled system of nonlinear second-order differential equations, including vibration equation of structure and van der Pol's equation, are solved synchronously. Lift coefficient is obtained by solving the coupled equations. Numerical solution is accomplished for three coupling models: displacement coupling, velocity coupling and acceleration coupling in each of which force is function of displacement, velocity and acceleration respectively. Time response, lift coefficient and vibration amplitude in steady state are obtained and plotted. Phase angle between the structure motion and lift coefficient change considerably when passing the locking zone which is well coincident with experimental results. Steady state vibration amplitudes for mentioned models are verified by comparing with experimental results.
Amir Moghiseh, Abbas Rahi,
Volume 9, Issue 18 (3-2014)
Abstract
The corrosion fracture life of marine riser is investigated. Riser will be modeled as a long beam and the wave and current forces is estimated by short wave theory and modified Morison’s equation. Dynamic equilibrium equations of riser will be obtained on based of Euler theory. After bending stress calculation along the riser that includes effect of riser weight and platform motion, loading history can be obtained in riser cross section. Since risers exposed to seawater and sour crude oil, an initial crack can have destructive effects and corrosion fracture can be occurred. So effect of initial crack in riser cross sections in different depths and at present of corrosive fluid is studied. At the end the effect of seawater and crude oil on crack propagation and corrosion fracture life is investigated. In order to solve riser dynamic equilibrium equation Range-Kutta and finite difference methods will be used.
Mahmud Poorjamshidian, Saied Mahjoubmoghadas, Amiralaldin Motalebi, Javad Sheikhi,
Volume 10, Issue 19 (9-2014)
Abstract
In this study, Homotopy analysis method is employed for nonlinear vibrational analysis of marine riser subjected to variable axial loads. Mid-plane stretching effect has been considered in the model. Galerkin's decomposition technique is used to convert the Partial differential equation of the motion to nonlinear ordinary differential equation. Homotopy analysis method (HAM) is applied to find analytical expressions for nonlinear natural frequencies of the riser. Effects of design parameters such as riser’s length and Initial static displacement of upper support on riser frequency are investigated. The analytical expressions are valid for a wide range of vibration amplitudes. Comparing the semi-analytical solutions with numerical results, presented in the literature, indicates proper agreement.
Ali Balouei, Jaafar Ghanbari,
Volume 19, Issue 41 (12-2023)
Abstract
Flexible risers are one of the crucial pieces of equipment for moving the output fluid from the well to the platform during the extraction of oil and gas from deep sea resources. One of the causes of collapse in these pipes is the high hydrostatic pressure that is applied to the riser in deep water. Its innermost layer, known as the carcass, is the layer that plays the most significant role in the resistance to external pressure. This article uses the finite element method to investigate the collapse (non-linear buckling) of the riser under pressure from the outside. A new design that draws inspiration from the structure of a beetle's exoskeleton has been presented to increase the load capacity of the carcass layer. This type of beetle's skeleton is constructed in such a way that it creates a strong connection between various parts of the external skeleton to produce high strength against external pressures while still allowing for the necessary movement flexibility. To assess how well the new design performs in comparison to the original, nonlinear buckling of the new structure under external pressure has been examined. The critical pressure in the new design is increased compared to the old design.
