Study On Smart Management And Control For VIV Of Marine Riser

For the oil and gas development in deep sea,marine riser system is key component in the drilling and production operation,and vortex-induced vibration(VIV)is the main cause of its fatigue failure.In the current research,most people use passive control methods to suppress the VIV of marine risers.However,when the VIV of the marine riser occurs,the flow field itself contains enormous energy.How to use the energy and apply it to the VIV suppression,there are currently few related technologies proposed.On the other hand,as a kind of smart material,the energy harvesting and driving function of piezoelectric material has a wide application prospect.However,how to apply it to marine risers is still under research.Based on this,this paper systematically explores the management technology of marine riser VIV control,and take intelligent optimization as the method,take smart materials as the carrier to provide new ideas for the realization of smart marine riser.In this paper,two-dimensional numerical simulations of VIV of a cylinder at low Reynolds number and high Reynolds number are carried out respectively,and the fatigue analysis of the marine riser is performed.Secondly,for the case of low Reynolds number,the optimization design of the cross-section shape of the fairing is carried out based on the genetic algorithm.For the high Reynolds number,the U-shape fairing is optimized based on parameter sensitivity.Then,a full-coupled fluid-solid-electric model was established and the energy harvesting and control characteristics of the bimorph cantilever piezoelectric vibrator were studied.Finally,this paper conducetd a comparison of marine riser VIV monitoring systems and the design of a VIV energy harvesting and control device for marine risers.In order to achieve the goal that harvest energy when the VIV of marine risers is not severe,and suppress VIV actively when the vibration is severe.The results show that:(1)Under the condition of low Reynolds number with two degrees of freedom,the numerical simulation results well reproduce the initial and lower branches of the VIV response;for the single degree of freedom at high Reynolds number,the k-ε model is used for simulation and the results show that the initial,upper and lower branches of the VIV response are well reproduced.Based on the fatigue analysis of the marine riser by SHEAR7,the root mean square displacement curve and the fatigue curve of the riser are obtained.(2)In the fairing optimization design,for two degrees of freedom,the flow velocity plays a more important role in the shape optimization process,and the number of design variables has less influence on the optimization process;for three degrees of freedom,the Caudal Fin-like Shape fairing has better stability than Teardrop fairing;moreover,the U-shaped fairings of different shapes are suitable for different flow speed ranges.(3)Regarding the energy harvesting characteristics of the piezoelectric vibrator,as the flow rate increases or the length of the piezoelectric vibrator increases,the terminal voltage of the piezoelectric vibrator increases.The thickness of the piezoelectric layer in the piezoelectric vibrator has no significant effect on the floating energy effect.With regard to the control characteristics,the higher the input terminal voltage is,the greater the bending deformation of the piezoelectric vibrator is,and the vibrator responds to the input voltage signal accordingly.(4)Proposed the implementation process of marine riser VIV control and control technology,provided a new idea for smart control for VIV of marine riser and preliminary testify its feasibility.