2-DOF vortex-induced vibration of two tandem square cylinders with varying natural frequency ratios

The study is about submarine pipeline. Considering the impact of different axial force, The reduced velocity is introduced as the pipeline vibration effect of vortex trail releasing. The vibration parameters of the span pipeline are analyzed and vibration control formula is built. The natural span length of the submarine pipeline is calculated according to the DNV-OS-F101 rule. The natural frequency of the span pipeline and the allowable span length are solved. The case study of submarine pipeline in Chengdao oil field is made and the variation law of natural frequency of span pipeline is got. The stream reduced velocity decreases as the axial force increase. The theory analysis of the vortex induced vibration can provide the scientific basis for the safety design of offshore submarine pipeline.

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Three-dimensional numerical simulation of two-degree-of-freedom VIV of a circular cylinder with varying natural frequency ratios atRe=500

Journal of Fluids and Structures ◽

10.1016/j.jfluidstructs.2017.06.001 ◽

2017 ◽

Vol 73 ◽

pp. 162-182 ◽

Cited By ~ 19

Author(s):

Enhao Wang ◽

Qing Xiao ◽

Atilla Incecik

Keyword(s):

Numerical Simulation ◽

Circular Cylinder ◽

Natural Frequency ◽

Three Dimensional ◽

Degree Of Freedom ◽

Frequency Ratios ◽

Two Degree Of Freedom

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Experimental Analysis of Vortex Induced Vibration in the Bladeless Small Wind Turbine

Volume 2: Combustion, Fuels, and Emissions; Renewable Energy: Solar and Wind; Inlets and Exhausts; Emerging Technologies: Hybrid Electric Propulsion and Alternate Power Generation; GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2019-2484 ◽

2019 ◽

Author(s):

Micha Premkumar Thomai ◽

Lasoodawanki Kharsati ◽

Nakandhrakumar Rama Samy ◽

Seralathan Sivamani ◽

Hariram Venkatesan

Keyword(s):

Energy Conversion ◽

Wind Turbine ◽

Natural Frequency ◽

Cross Section ◽

Vortex Shedding ◽

Rectangular Cross Section ◽

The Body ◽

Test Facility ◽

Vortex Induced Vibration ◽

Small Wind Turbine

Abstract Vortex-induced vibration is one of the predominant fundamental concepts for forced oscillation which attracts considerable practical engineering application for energy conversion. In this work, an oscillation of a mast arising as a result of wind force is utilized for energy conversion. The paradigm for energy conversion from vortex-induced vibration in the mast is the bladeless wind turbine. It consists of a rigid mass known as a mast, fixed in the spring of stiffness (k) and allowed to oscillate along the direction of the flow. In this work, four different types of mast have been fabricated and tested. The first is uniform tapered hollow conical mast (MAST1), the cross-section of the second is uniform tapered plus symbol (MAST2), the third is uniform tapered inversed plus symbol (MAST3) and the fourth is uniform tapered simple rectangular cross-section (MAST4). All the masts were fabricated using fiber carbon. The experiments were conducted in a versatile small wind turbine testing facility of Hindustan Institute of Technology and Science, Chennai. This test facility contained an open jet wind tunnel with variable frequency drive and other measuring instruments. The vibration sensor was located in the mast where it experienced a large oscillation in a free stream. In this experiment, an increase in wind velocity led to a terrible change in the amplitude of vibration. A vigorous oscillation was experienced in this mast at this critical frequency, when the natural frequency of the mast was synchronized with the frequency of the vortex shedding and the frequency of the oscillation of the mast. The total force in this oscillation was a summation of the body force due to the mass of the mast and vorticity force that is mainly which was the result of the shedding of the vortices. In this work, extensive studies have been carried out for Reynolds number ranging from 2.5 × 105 to 5.0 × 105. The mast length to diameter ratio of 13 was exposed to various speeds of wind and response was measured. The occurrence of the maximum oscillation in a simple rectangular mast was seen where vortex shedding due to the bluff body was large for constant mass and spring stiffness. The frequency of the oscillation at maximum amplitude of the rectangular cross-section mast was equal to the natural frequency, due to vortices shedding at critical velocity. This demonstrated the appropriateness of the simple rectangular cross-section for harnessing the low rated wind energy and its suitability for renewable energy conversion in the small bladeless wind turbine.

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Flow-Induced Streamwise Oscillation of Two Square Cylinders in Tandem Arrangement

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2007-26123 ◽

2007 ◽

Author(s):

Atsushi Okajima ◽

Takahiro Kiwata ◽

Satoru Yasui ◽

Yoshiki Mori ◽

Shigeo Kimura

Keyword(s):

Vortex Shedding ◽

The Other ◽

Limit Cycle Oscillation ◽

Response Characteristics ◽

Excitation Region ◽

Square Cylinders ◽

Reference Length ◽

Tandem Square Cylinders ◽

Karman Vortex ◽

Cycle Oscillation

Flow-induced streamwise oscillation of two tandem square cylinders has been studied by means of free-oscillation testing in a wind tunnel. One cylinder was elastically supported so as to allow it to move in the streamwise direction; the other was fixed to the tunnel sidewalls. Small values of the reduced mass-damping parameter (Cn ≤ 1.63) have been considered. When the upstream cylinder is free to oscillate, there are two excitation regions: the first for reduced velocity, Vr, in the range 2.5 ≤ Vr ≤ 5 and cylinder gap distance to reference-length ratio, s, between 0.3 and 2, is due to movement-induced excitation accompanied by symmetrical vortex shedding, while the second, for 0.75 ≤ s ≤ 1.5 and 4.5 ≤ Vr ≤ 6.5, is due to vortex excitation by alternate Karman vortex shedding, accompanied with unstable limit-cycle oscillation. For wide gap distances over 2.5, an excitation region of the upstream cylinder occurs for 3.5 ≤ Vr ≤ 4.7, which is due to alternate Karman vortex shedding, and resembles the streamwise oscillation of a single cylinder. On the other hand, when the downstream cylinder is free to oscillate for narrow gap distances of 0.3 ≤ s ≤ 0.75, the response characteristics have an excitation region due to alternate Karman vortex shedding from the two cylinders, connected by dead water region between them, for 3.2 ≤ Vr ≤ 5.4. When s is greater than 1, the downstream cylinder experiences buffeting by wake fluctuation of the upstream cylinder.

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Numerical studies of the flow structure and aerodynamic forces on two tandem square cylinders with different chamfered-corner ratios

Physics of Fluids ◽

10.1063/1.5100266 ◽

2019 ◽

Vol 31 (7) ◽

pp. 075102 ◽

Cited By ~ 3

Author(s):

Jingmiao Shang ◽

Qiang Zhou ◽

Md. Mahbub Alam ◽

Haili Liao ◽

Shuyang Cao

Keyword(s):

Flow Structure ◽

Aerodynamic Forces ◽

Numerical Studies ◽

Square Cylinders ◽

Tandem Square Cylinders

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Managing Vortex Induced Vibration in Well Jumper Systems

Volume 3: Pipeline and Riser Technology; Ocean Space Utilization ◽

10.1115/omae2008-57026 ◽

2008 ◽

Author(s):

Kenneth Bhalla ◽

Lixin Gong

Keyword(s):

Natural Frequency ◽

Natural Frequencies ◽

Cross Flow ◽

Mitigation Measures ◽

Mode Shapes ◽

Bottom Current ◽

Vortex Induced Vibration ◽

Flow Response ◽

Out Of Plane ◽

Lock In

The purpose of this paper is to present a method that has been developed to identify if vortex induced vibration (VIV) occurs in well jumper systems. Moreover, a method has been developed to determine when VIV mitigation measures such as strakes are required. The method involves determining the in-plane and out-of-plane natural frequencies and mode shapes. The natural frequencies are then used, in conjunction with the maximum bottom current expected at a given location to determine if suppression is required. The natural frequency of a jumper system is a function of many variables, e.g. span length, leg height, pipe diameter and thickness, buoyancy placement, buoyancy uplift, buoyancy OD, insulation thickness, and contents of the jumper. The suppression requirement is based upon calculating a lower bound lock-in current speed based upon an assumed velocity bandwidth centered about the lock-in current. The out-of-plane VIV cross-flow response is produced by a current in the plane of the jumper; whereas the in-plane VIV cross-flow response is produced by the out-of-plane current. Typically, the out-of-plane natural frequency is smaller than the in-plane natural frequency. Jumpers with small spans have higher natural frequencies; thus small span jumpers may require no suppression or suppression on the vertical legs. Whereas, larger span jumpers may require no suppression, suppression on the vertical legs or suppression on all the legs. The span of jumper systems (i.e. production, water injection, gas lift/injection ...) may vary in one given field; it has become apparent that not all jumper systems require suppression. This technique has allowed us to recognize when certain legs of a given jumper system may require suppression, thus leading to a jumper design whose safety is not compromised while in the production mode, as well as minimizing downtime and identifying potential savings from probable fatigue failures.

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