Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures

Rahman, Mohd Nordin Abdul; Hussin, W.N.W.; Mohd, Mohd Hairil; Harun, Fatimah Noor; Quen, Lee Kee; Paik, Jeom Kee

doi:10.1080/17445302.2019.1593308

Cited by 10 publications

(6 citation statements)

References 28 publications

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“…is will increase the riser VIV peak frequencies, which cause the riser VIV displacement to decrease. On the other hand, it can be known from equations (13) and 14that when the towing speed increases, the external excitation forces acting on the riser increase continuously.…”

Section: Long Flexible Risermentioning

confidence: 99%

“…Based on the van der Pol equation, Bishop and Hassan [3] first put forward the specific expression of the wake oscillator model. en, wake oscillator models have been continuously improved by some researchers [4][5][6][7][8][9][10][11][12][13]. Based on wake oscillator models, some studies have analyzed the coupled in-line and cross-flow VIV response of long slender flexible cylinders in uniform flows [14][15][16], and some scholars have also focused their attention on the study of coupled in-line and cross-flow VIV response of long slender flexible cylinders in sheared flows [17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…It can be known from this that when the seawater flow speed changes, the variation rules of the riser in-line and cross-flow are related to factors such as the vortex shedding frequency, the seawater flow speed, and the axial tension force. According to equations (8),(13), and(14), when the seawater…”

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confidence: 99%

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Study on Vortex-Induced Vibration of Deep-Water Marine Drilling Risers in Linearly Sheared Flows in consideration of Changing Added Mass

Gao

Cong

Cui

et al. 2020

Mathematical Problems in Engineering

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In order to more accurately predict the coupled in-line and cross-flow vortex-induced vibration (VIV) response of deep-water marine drilling risers in linearly sheared flows, an improved three-dimensional time-domain coupled model based on van der Pol wake oscillator models was established in this paper. The impact of the in-line and cross-flow changing added mass coefficients was taken into account in the model. The finite element, Newmark-β, and Newton–Raphson methods were adopted to solve the coupled nonlinear partial differential equations. The entire numerical solution process was realized by a self-developed program based on MATLAB. Comparisons between the numerical calculations and the published experimental tests showed that the improved model can more accurately predict some main features of the coupled in-line and cross-flow VIV of long slender flexible risers in linearly sheared flows to some extent. The coupled in-line and cross-flow VIV of a real-size marine drilling riser, usually used in the deep-water oil/gas industry in the South China Sea, was analyzed. The influence of top tension force and seawater flow speed, as well as platform heave amplitude and frequency, on the riser in-line and cross-flow VIV was also discussed. The results show that the platform heave motion increases the VIV displacements and changes the magnitudes of peak frequencies as well as the components of frequencies. The platform heave motion also has a significant influence on the vibration modes of the middle and upper sections of the riser. The impact level of each factor on the in-line and cross-flow VIV response of the riser is different. The improved model and the results of this paper can be used as a reference for the engineering design of deep-water marine drilling risers.

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Section: Long Flexible Risermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Study on Vortex-Induced Vibration of Deep-Water Marine Drilling Risers in Linearly Sheared Flows in consideration of Changing Added Mass

Gao

Cong

Cui

et al. 2020

Mathematical Problems in Engineering

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“…Flow-induced vibration (FIV) of a bluff body has received huge attention in various fields such as the aerospace industry, bridges, tall buildings, smokestacks, power generation, and engineering infrastructure. Therefore, FIV has been a hot topic for researchers for the past 20 years and various methods have been undertaken such as experiments and simulations to investigate FIV on cylindrical structures [1][2]. VIV and galloping can be categorized under FIV phenomenon, where VIV occurs at steady conditions while galloping can be considered as unsteady FIV phenomenon that usually arises in asymmetrical bodies.…”

Section: Introductionmentioning

confidence: 99%

Flow Induced Vibration in Square Cylinder of Various Angles of Attack

Ramzi

Lee²,

ZAINURI³

et al. 2022

IIUMEJ

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An experimental study was carried out to identify the effect of angle of attack on flow-induced vibration (FIV) of square cylinders. The experiment was conducted at the Aeronautical and Wind Engineering Laboratory (AEROLAB), UTM Kuala Lumpur using a wind tunnel that was free from external wind conditions. A supporting structure was designed and fabricated to conduct this experiment. The importance of this support structure was to enable the rigid cylinder to suspend and vibrate freely upon excitation of wind speed. The results were analysed through the response of amplitude and frequency of the rigid cylinder over a velocity range of 0.5m/s to 4.0m/s. The results showed that for a square cylinder of ?=0°, vortex-induced vibration (VIV) occurred at low reduced velocity (UR) in range of 5 ? UR ? 10 and galloping occurred at higher reduced velocity which started at UR=15. A tranquil zone was found between VIV and galloping in the reduced velocity range of 10 ? UR ? 15. As for ?=22.5° and 45°, only VIV response was found at low reduced velocity in range of 4? UR ? 9. ABSTRAK: Satu kajian eksperimentasi telah dilakukan bagi mengenal pasti pengaruh sudut serangan oleh getaran cetusan-aliran (FIV) dalam silinder persegi. Eksperimen ini dijalankan di Makmal Kejuruteraan Aeronautika dan Angin (AEROLAB), UTM Kuala Lumpur dengan menggunakan terowong angin yang bebas dari pengaruh angin luar. Struktur sokongan telah direka dan difabrikasi bagi tujuan eksperimen ini. Ini penting bagi membolehkan silinder pegun tergantung dan bergetar dengan bebas semasa ujian kelajuan angin. Dapatan kajian dianalisis melalui tindak balas amplitud dan frekuensi silinder pegun pada kadar halaju 0.5m/s sehingga 4.0m/s. Hasil kajian menunjukkan bahawa bagi silinder persegi ? = 0 °, getaran pengaruh-vorteks (VIV) berlaku pada halaju rendah (UR) dalam julat 5 ? UR ? 10 dan getaran lebih teruk telah ketara berlaku pada kadar halaju berkurang iaitu bermula pada UR = 15. Zon tenang dijumpai antara VIV dan getaran teruk pada kadar halaju berkurang 10 ? UR ? 15. Adapun pada ? = 22.5° dan 45°, hanya tindak balas VIV dijumpai pada halaju rendah dalam kadar 4? UR ? 9.

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“…Contributions towards understanding VIV have been carried out by using experiments, numerical simulation and analytical modelling [2][3][4][5][6][7]. Recently, Lou et al, [8] divided the suppression devices into two categories which are, active and passive controls.…”

Section: Introductionmentioning

confidence: 99%

Flow Past a Fixed and Freely Vibrating Drilling Riser System with Auxiliaries in Laminar Flow

Alias

Mohd

Musa

et al. 2021

ARFMTS

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Drilling risers used in oil and gas operations are subjected to external loads such as wave and current. One of the phenomena that arise from the external loads is the Vortex-Induced Vibration (VIV), which affects the performance of the riser due to excessive vibration from the vortex shedding. A significant factor influencing the VIV is the design of the drilling riser and its auxiliary lines. Until now, the optimum geometrical size and gap between the auxiliary and the main riser are still very scarcely studied. In this paper, the main objective is to study the effects of the gap ratio (G/D) on the vortex shedding phenomenon on a fixed and freely vibrating riser. The riser system was modelled with a main drilling riser and six auxiliary lines with a constant diameter ratio (d/D) of 0.45 and gap ratio (G/D) = 0 to 2.0 in the laminar flow regime with Reynold Number, Re = 200. The simulations were conducted for Single Degree of Freedom (SDOF) using Computational Fluid Dynamics (CFD) software, Altair AcuSolve. It was found that the freely vibrating riser experienced higher lift and drag forces as compared to the fixed riser due to the synchronization (lock-in) of the shedding vibration and the natural frequencies. The lock-in phenomenon is normally observed on the drilling riser at different current directions. The forces are reduced when G/D is higher. The vortex shedding was significantly reduced for auxiliaries between 0.3 to 1.4. It is confirmed that by modifying the interaction of the vortices in the wake region with auxiliary lines, the hydrodynamic forces will be decreased. Finally, this fundamental study could potentially be used in the designing stage of an optimum drilling riser system by considering significant governing factors.

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Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures

Cited by 10 publications

References 28 publications

Study on Vortex-Induced Vibration of Deep-Water Marine Drilling Risers in Linearly Sheared Flows in consideration of Changing Added Mass

Study on Vortex-Induced Vibration of Deep-Water Marine Drilling Risers in Linearly Sheared Flows in consideration of Changing Added Mass

Flow Induced Vibration in Square Cylinder of Various Angles of Attack

Flow Past a Fixed and Freely Vibrating Drilling Riser System with Auxiliaries in Laminar Flow

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