Experimental Investigation on Vortex-Induced Vibration of a Free-Hanging Riser Under Vessel Motion

A model test of a free-hanging riser under vessel motion was performed in the ocean basin at Shanghai Jiao Tong University to confirm whether vortex-induced vibration (VIV) can happen due to pure vessel motion, to investigate the equivalent current velocity and Keulegan–Carpenter (KC) number effect on the VIV responses and to obtain the correlations for free-hanging riser VIV under vessel motion with VIV for other compliant risers. Top end of the riser was forced to oscillate at given vessel motion trajectories. Fiber Brag Grating (FBG) strain sensors were used to measure the riser dynamic responses. Experimental results confirmed that the free-hanging riser would experience significant out-of-plane VIV. Meanwhile, VIV responses in terms of response amplitude, response frequency and cross-section trajectories under different test cases were further compared and discussed. Most importantly, the correlation among VIV response frequency, vortex shedding pairs and maximum KC number KCmax was revealed. The presented work is supposed to provide useful references for gaining a better understanding on VIV induced by vessel motion, and for the development of future prediction models.

Download Full-text

Experimental Investigation on Vortex-Induced Vibration of a Free-Hanging Riser Under Vessel Motion and Uniform Current

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4036370 ◽

2017 ◽

Vol 139 (4) ◽

Cited By ~ 12

Author(s):

Jungao Wang ◽

Shixiao Fu ◽

Jiasong Wang ◽

Huajun Li ◽

Muk Chen Ong

Keyword(s):

Prediction Models ◽

Ocean Basin ◽

Dynamic Responses ◽

Ocean Current ◽

Response Frequency ◽

Vortex Induced Vibration ◽

Out Of Plane ◽

Future Prediction ◽

Uniform Current ◽

Vessel Motion

A model test of a free-hanging riser under vessel motion and uniform current is performed in the ocean basin at Shanghai Jiao Tong University to address four topics: (1) confirm whether vortex-induced vibration (VIV) can happen due to pure vessel motion; (2) to investigate the equivalent current velocity and Keulegan–Carpenter (KC) number effect on the VIV responses; (3) to obtain the correlations for free-hanging riser VIV under vessel motion with VIV for other compliant risers; and (4) to study the similarities and differences with VIV under uniform current. The top end of the riser is forced to oscillate or move, in order to simulate vessel motion or ocean current effects. Fiber Bragg Grating (FBG) strain sensors are used to measure the riser dynamic responses. Experimental results confirm that the free-hanging riser will experience significant out-of-plane VIV under vessel motion. Meanwhile, vessel motion-induced VIV responses in terms of response amplitude, response frequency, and cross section trajectories under different test cases are further discussed and compared to those under ocean uniform current. Most importantly, the correlation among VIV response frequency, vortex shedding pairs, and maximum KC number KCmax is revealed. The presented work is supposed to provide useful references for gaining a better understanding on VIV of a free-hanging riser and for the development of future prediction models.

Download Full-text

Vortex-Induced Vibration of Steel Catenary Riser Under Vessel Motion

Volume 2: CFD and VIV ◽

10.1115/omae2014-23584 ◽

2014 ◽

Cited By ~ 5

Author(s):

Jungao Wang ◽

Shixiao Fu ◽

Rolf Baarholm

Keyword(s):

Wave Speed ◽

Ocean Basin ◽

Mean Square ◽

Wall Effects ◽

Vortex Induced Vibration ◽

Steel Catenary Riser ◽

Out Of Plane ◽

Push Down ◽

Vessel Motion ◽

Scr Model

A truncated steel catenary riser (SCR) model was experimentally tested in the ocean basin by oscillating the top end of the model to simulate the heave and surge vessel motion in order to investigate the vortex-induced vibration (VIV) features. Out-of-plane VIV responses were generally analyzed revealing that although the root mean square (RMS) strain distributed rather broadband, the displacement was quite consistent within a narrowband from 0.2D to 0.3D, and the touch-down point (TDP) area was found not to be the place suffering the maximum out-of-plane VIV response due to near wall effects. What’s more, strong wave propagations were firstly reported and summarized as a distinguished feature for VIV of a SCR under vessel motions, and further results reveal that wave propagation during the ‘lift up’ phase was quite different from that during ‘push down’ in terms of both wave speed and ‘power-in’ region location which is assumed to be caused by the tension variation along the model.

Download Full-text

Vortex Induced Vibration of a Steel Catenary Riser Under Out-of-Plane Current: An Experimental Study

Volume 2: CFD and FSI ◽

10.1115/omae2019-96112 ◽

2019 ◽

Author(s):

Yuwang Xu ◽

Jungao Wang ◽

Haojie Ren ◽

Mengmeng Zhang ◽

Shixiao Fu

Keyword(s):

Large Scale ◽

Ocean Basin ◽

Strain Sensors ◽

Scale Model ◽

Vortex Induced Vibration ◽

Steel Catenary Riser ◽

Numerical Predictions ◽

Large Scale Model ◽

Out Of Plane ◽

Vibration Responses

Abstract To investigate the VIV characteristics and to further develop the corresponding numerical predictions of a steel catenary riser under out-of-plane current, a large-scale model of a steel catenary riser was towing in an ocean basin at various speeds and directions. Fiber Bragg grating strain sensors are instrumented on the riser model to measure both in-plane and out-of-plane responses. The vortex-induced vibration responses of the steel catenary riser under out-of-plane current, i.e., the oscillating amplitude, the response frequency, and the traveling wave phenomenon, are compared with those under the in-plane current.

Download Full-text

Experimental Investigation on Vortex-Induced Vibration of a Flexible Pipe under Higher Mode in an Oscillatory Flow

Journal of Marine Science and Engineering ◽

10.3390/jmse8060408 ◽

2020 ◽

Vol 8 (6) ◽

pp. 408 ◽

Cited By ~ 1

Author(s):

Haojie Ren ◽

Mengmeng Zhang ◽

Jingyun Cheng ◽

Peimin Cao ◽

Yuwang Xu ◽

...

Keyword(s):

Oscillatory Flow ◽

Cross Flow ◽

Dominant Frequency ◽

Ocean Basin ◽

Dominant Mode ◽

Flexible Pipe ◽

Vortex Induced Vibration ◽

Displacement Reconstruction ◽

Vessel Motion ◽

Lock In

Different from the previous studies of the vortex-induced vibration (VIV) dominated by first mode of flexible pipe in an oscillatory flow, the features of a higher mode dominated are experimentally investigated in the ocean basin. The flexible pipe is forced to harmonically oscillate with different combinations of a period and amplitude. The design dominant mode consists of first and second modes under the maximum reduced velocity (VR) of approximately 5.5 with a KC number ranging from 22 to 165. The VIV responses between only the excited first mode and the excited higher mode are compared and studied using displacement reconstruction and wavelet transform methods. The discrepancies of spatial and temporal response between smaller and larger KC numbers (KC = 56 and 121) are first observed. The strong alternate mode dominance and lock-in phenomena occur in the case of larger KC numbers, while they cannot be observed in the case of smaller KC numbers under higher modes. The VIV dominant frequency in the in-line (IL) direction is found to be always triple the oscillatory flow frequency and not twice that in the cross flow (CF) direction. The dominant frequency in the CF direction can be predicted by the Strouhal law, and the Strouhal number is approximately 0.18 under VR = 5.5, which is not affected by the excited mode. Moreover, differences of response motion trajectory are also revealed in this paper. The present work improves the basic understanding of vessel motion induced VIV and provides helpful references for developing prediction methods of VIV in an oscillatory flow.

Download Full-text

Evaluation of Process Control Schemes for Sour Water Strippers in Petroleum Refining

Processes ◽

10.3390/pr9020363 ◽

2021 ◽

Vol 9 (2) ◽

pp. 363

Author(s):

Chii-Dong Ho ◽

Yih-Hang Chen ◽

Chao-Min Chang ◽

Hsuan Chang

Keyword(s):

Feedback Control ◽

Prediction Models ◽

Feedforward Control ◽

Absolute Error ◽

Dynamic Responses ◽

Control Schemes ◽

Online Measurements ◽

Measurement Delay ◽

Water Feed ◽

Sour Water

For the sour water strippers in petroleum refinery plants, three prediction models were developed first, including the estimators of sour water feed concentrations using convenient online measurements, the minimum reboiler duty and the corresponding internal temperature at a specific location (Tstage,29). Feedforward control schemes were developed based on these prediction models. Four categories of control schemes, including feedforward, feedback, feedback with external reset, and feedforward-feedback, were proposed and evaluated by the rigorous dynamic simulation model of the sour water stripper for their dynamic responses to the sour water feed stream disturbances. The comparison of control performance, in terms of the settling time, integrated absolute error (IAE) of the NH3 concentration of the stripped sour water and IAE of the specific reboiler duty, reveals that FFT (feedforward control of Tstage,29) and FBA-DT3 (feedback control with 3 min concentration measurement delay) are the best control schemes. The second-best control scheme is FBAT (cascade feedback control of concentration with temperature).

Download Full-text

VIV Excitation Competition Between Bare and Buoyant Segments of Flexible Cylinders

Volume 7: CFD and VIV ◽

10.1115/omae2013-11296 ◽

2013 ◽

Cited By ~ 2

Author(s):

Zhibiao Rao ◽

J. Kim Vandiver ◽

Vikas Jhingran

Keyword(s):

Model Test ◽

Practical Problem ◽

Excitation Frequency ◽

Ocean Basin ◽

Recent Model ◽

Total Amplitude ◽

Vortex Induced Vibration ◽

Pipe Model ◽

Exploration And Production ◽

Different Diameters

This paper addresses a practical problem: “Under which coverage of buoyancy modules, would the Vortex Induced Vibration (VIV) excitation on buoyant segments dominate the response?” This paper explores the excitation competition between bare and buoyant segments of a 38 meter long model riser. The source of data is a recent model test, conducted by SHELL Exploration and Production at the MARINTEK Ocean Basin in Trondheim Norway. A pipe model with five buoyancy configurations was tested. The results of these tests show that (1) the excitation on the bare and buoyant regions could be identified by frequency, because the bare and buoyant regions are associated with two different frequencies due to the different diameters; (2) a new phenomenon was observed; A third frequency in the spectrum is found not to be a multiple of the frequency associated with either bare or buoyancy regions, but the sum of the frequency associated with bare region and twice of the frequency associated with buoyancy region; (3) the contribution of the response at this third frequency to the total amplitude is small; (4) the power dissipated by damping at each excitation frequency is the metric used to determine the winner of excitation competition. For most buoyancy configurations, the excitation on buoyancy regions dominates the VIV response; (5) a formula is proposed to predict the winner of the excitation competition between bare and buoyant segments for a given buoyancy coverage.

Download Full-text

Seismic Response of Embankment Dams Based on Recorded Strong-Motion Data in Japan

Earthquake Spectra ◽

10.1193/042918eqs107m ◽

2019 ◽

Vol 35 (2) ◽

pp. 955-976 ◽

Cited By ~ 2

Author(s):

DongSoon Park ◽

Tadahiro Kishida

Keyword(s):

Time Series ◽

Seismic Response ◽

Prediction Models ◽

Strong Motion ◽

Dynamic Responses ◽

Design Stage ◽

Ground Acceleration ◽

Motion Data ◽

Embankment Dams ◽

Strong Motion Database

It is important to investigate strong-motion time series recorded at dams to understand their complex seismic responses. This paper develops a strong-motion database recorded at existing embankment dams and analyzes correlations between dam dynamic responses and ground-motion parameters. The Japan Commission on Large Dams database used here includes 190 recordings at the crests and foundations of 60 dams during 54 earthquakes from 1978 to 2012. Seismic amplifications and fundamental periods from recorded time series were computed and examined by correlation with shaking intensities and dam geometries. The peak ground acceleration (PGA) at the dam crest increases as the PGA at the foundation bedrock increases, but their ratio gradually decreases. The fundamental period broadly increases with the dam height and PGA at the foundation bedrock. The nonlinear dam response becomes more apparent as the PGA at the foundation bedrock becomes >0.2 g. The prediction models of these correlations are proposed for estimating the seismic response of embankment dams, which can inform the preliminary design stage.

Download Full-text

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.

Download Full-text