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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) str...
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Figure 2 shows the overview of the complete experimental setup in air. The experimental setup includes two parts: one is the lower underwater section, which has a motion control track welded on the fake bottom; the other section is the top motion control apparatus attached beneath the carriage as shown in Figure 3. Both top and bottom end connections were pin-pin ...
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... For planar flows, travelling waves prevail. The effects of vessel's oscillatory motion on VIV of a catenary riser with a lay-down part have been experimentally studied in Wang et al. (2014) and Zhang et al. (2021). The former study highlighted the effect of in-plane VIV on the riser's touch-down point whereas the latter study discussed chaotic features in the obtained hydrodynamic forces strongly dependent on the vessel motion and coupling of in-plane and out-of-plane responses. ...
This study presents an advanced numerical prediction model based on nonlinear wake oscillators for the investigation of multidirectional vortex-induced vibration (VIV) responses of a long catenary riser depending on the structural curved configuration versus the incoming flow direction. By considering a uniform free-stream flow aligned with the initial curvature plane of the catenary riser in a convex or concave shape, the normal flow velocity component is nonlinearly sheared owing to the spanwise variation of inclination angles. This is different from the perpendicular flow case in which the normal flow velocity is spatially constant. To capture the influence of flow direction on the three-dimensionally coupled cross-flow and in-line VIV, distributed wake oscillators are introduced and applied to simulate the fluctuating hydrodynamic lift and drag forces that account for the important effects of cylinder inclination, variable vortex excitation frequencies, global-local displacement relationships, and relative flow-cylinder velocities. The amplified mean drag force and the axial force depending on the tangential flow velocity are also considered. These empirical hydrodynamic effects are nonlinearly coupled with the equations of riser three-dimensional motion, and the overall governing equations are numerically solved to assess the multimode, multi-frequency and multi-degree-of-freedom responses. Validation of the model is carried out for VIV of flexible straight and curved cylinders based on experimental results in the literature. Parametric investigations are performed by varying the incoming flow velocities in perpendicular, convex and concave configurations for a long catenary riser with a low mass-damping ratio. In-plane (horizontal and vertical) and out-of-plane VIV features are presented and discussed in terms of space-time varying amplitudes, drag-amplified shape reconfigurations, oscillation frequencies, lock-in occurrences, dual resonances, orbital motion trajectories, fluid-structure energy transfer, and multimodal contributions. Overall prediction results highlight the influence of the cylinder geometric configuration versus the incoming flow orientation on multidirectional VIV characteristics that should be recognised and incorporated into practical analysis tools.
... Comparing to the top-tensioned riser, steel catenary riser (SCR) has become a better choice owing to its great adaptability to the high-temperature, high-pressure environment, and economy. 8 However, SCR will also suffer from collision, vibration, fatigue damage, and other problems under the actions of various complex loads. The motion of SCR takes place due to some factors such as wind, waves, current, and platform motion and generates the vortex shedding phenomenon around risers when SCR is in the water. ...
The vortex-induced vibration (VIV) response performances of a two-degree-of-freedom circular cylinder with different surface roughnesses were numerically investigated in this work. Four typical roughnesses values of 1 × 10 ⁻⁴ , 5 × 10 ⁻³ , 1 × 10 ⁻² , and 2 × 10 ⁻² were examined for the range of the reduced velocity ( V r = 1–20). The VIV response characteristics including the vibration amplitude, vibration frequency, VIV trajectory, vortex shedding flowing pattern, and hydrodynamic force for different rough cylinders were systematically compared. The numerical results showed that the VIV response of roughness cylinder experiences five evolutions as V r increases, including five typical X–Y trajectories: centrosymmetry, “M” or “W,” “dough twists” or “candy,” “∞,” and asymmetrical ∞, exhibiting three vortex shedding flow pattern: S mode, C + S mode, and SS mode (a pair of symmetric vortices along the x-axis) under certain conditions. The VIV response was sensitive to the roughness in regime IV and regime V. Furthermore, the normalized vibration frequency of the rough cylinder was an integer multiple of the oscillatory flow frequency, except for the V r ranged from 6 to 7. The vibration frequency in in-line (IL) direction was consistent with the frequency of the oscillatory flow, which was immune to the change of roughness. Additionally, when roughness was equal to 2 × 10 ⁻² , the reduction of maximum vibration amplitude in the cross-flow direction reached 31.2%, comparing with smooth cylinder, whereas the maximum vibration amplitude in the IL direction increased only by 6.2%.
... Under in-plane vessel motions, the SCR will experience relatively oscillatory flow due to its motions in in-plane direction (X-Z plane). The oscillatory flow has been proved to induce VIV responses in the out-of-plane direction [24]. Such kinds of VIV still belong to the small displacement and small deformation problems; thus, it can be described by Euler-Bernoulli beam, an equation with time-varying tension in local coordinate system: ...
... When an SCR undergoes in-plane vessel motion, out-of plane VIV will be excited [24]. Multi-frequency coupling, amplitude modulation, and time-sharing frequency [6,10,29] are usually observed in vessel motion-induced VIV. ...
... The model test [24] was carried out in the ocean basin at Shanghai Jiao Tong University. The goal of the model test was to investigate VIV effects caused by in-plane vessel motion. ...
A method to identify vortex-induced forces and coefficients from measured strains of a Steel Catenary Riser (SCR) undergoing vessel motion-induced Vortex-induced Vibration (VIV) is proposed. Euler–Bernoulli beam vibration equations with time-varying tension is adopted to describe the out-of-plane VIV responses. Vortex-induced forces are reconstructed via inverse analysis method, and the Forgetting Factor Least Squares (FF-LS) method is employed to identify time-varying vortex-induced force coefficients, including excitation coefficients and added mass coefficients. The method is verified via a finite element analysis procedure in commercial software Orcaflex. The time-varying excitation coefficients and added mass coefficients of an SCR undergoing vessel motion-induced VIV are investigated. Results show that vessel motion-induced VIV is excited at the middle or lower part of the SCR and in the acceleration period of in-plane velocity, where most of the excitation coefficients are positive, while during the deceleration period, the excitation coefficients becomes too small to excite VIVs. Parameter γ [1] has strong correlation with excitation coefficients. In addition, time-varying tensions contribute significantly to the variations of added mass coefficients under the condition that the ratio of dynamic top tension to pretension exceeds the range of 0.7–1.3. Moreover, chaotic behaviors are observed in vortex-induced force coefficients and are more evident with the increase of vessel motion velocity. This behavior may attribute to the randomness existing in in-plane velocity and its coupling with out-of-plane vibrations.
... Gonzalez [21] conducted a series of VIV model tests and verified the occurrence of intermittent VIV of risers under oscillatory flows. Fu et al. [22] and Wang et al. [23][24][25] conducted a systematic experimental study on oscillatory flow VIV of flexible risers. They discovered and described distinct features of oscillatory flow VIV responses, and characterized the VIV developing process with three stages: building-up, lock-in and dying-out. ...
In this study, an efficient time-domain prediction model is developed to predict unsteady flow vortex-induced vibrations (VIV) of flexible risers. The hydrodynamic forces on flexible risers are calculated on the basis of forced oscillation experiments on rigid cylinders. A period identification criterion, based on the spatial and temporal variations of reduced velocity, is proposed to divide the entire vibration process into exciting and damping periods of each exited mode. In exciting periods, assuming that VIV enters an ideal lock-in stage, a non-iterative solving model is established under modal space for response calculations, which efficiently predicts time domain VIV responses. In damping periods, free-decay vibration theory based recurrence formulas are established under modal space, and they get solved stepwise for modal responses. After some slight response adjustments to smooth period transitions, the VIV response time history can be obtained efficiently. This model is validated by steady flow VIV prediction cases, and further applied to predict oscillatory flow VIV experimental results. The prediction cases reveal that this model is able to realize high-speed VIV predictions with satisfactory results and no convergence problems. This model, with high efficiency and stability, is highly suitable for unsteady flow VIV prediction in engineering applications.
... Recent research has reported a new type of vortex-induced vibration (VIV) in compliant risers caused by pure vessel motion, known as vessel motion-induced VIV [1][2][3]. Vessel motioninduced VIV occurs due to the equivalent oscillating current, which is generated by the riser global motion with respect to the water particles. Vessel motion-induced VIV is known to be dominated by the equivalent oscillating current parameters: both the inplane velocity and the Keulegan-Carpenter (KC) number distribution [4]. ...
... This further opens up the possibility of vessel motion-induced VIV for the free-hanging risers (FHRs). Jung et al. [6] carried out a scaled model test on the free-hanging Ocean Thermal Energy Conversion (OTEC) Riser under top end forced oscillation with small top KC number (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), and has found that vessel motion-induced VIV would occur even when the top KC number was as low as 4. Based on the same test data, Kwon et al. [7] further investigated the ocean current effect on the vessel motion-induced VIV responses, and he concluded that the in-line riser response was weakened, but crossflow VIV was strengthened owing to a large relative current velocity. Xiang et al. [8] carried out a series of free-hanging water intake riser model tests considering vessel motion and internal flow effect. ...
A free-hanging riser (FHR) is a typical riser configuration seen in the disconnected drilling riser, the water-intake riser, and the deep-sea mining riser. In offshore productions, these marine risers will move back and forth in water and further generate an equivalent oscillatory current around themselves, due to the vessel motions. Both in full-scale marine operations and model tests, it has been reported that such oscillatory current leads to riser vortex-induced vibration (VIV) and therefore causes structural fatigue damage. Recently, there have been some attempts to numerically predict vessel motioninduced VIV on the compliant production risers, with emphasize on relatively large Keulegan-Carpenter (KC) numbers. In the real marine operations, the risers experience small KC number scenarios during most of their service life. Therefore, the investigation of vessel motion-induced VIV under small KC number is of great significance, especially considering its contribution to the fatigue damage. In this paper, numerical investigation of VIV of a FHR attached to a floating vessel is carried out. A new response frequency model for vessel motion-induced VIV under small KC numbers is proposed and implemented in VIVANA. Validation of the proposed numerical methodology is performed against the published experimental results, where a good agreement is achieved.
... Recent research has reported a new type of VIV in compliant risers caused by pure vessel motion, known as vessel motion-induced VIV [1,2,3]. Vessel motion-induced VIV occurs because of the equivalent oscillating current generated by the riser global motion with respect to the water particles. ...
... As discussed above, one of the challenges in predicting vessel motion-induced VIV in the small KC number regime is to have a response frequency model which is capable of identifying the dominant frequency of vessel motion-induced VIV. Based on (or with reference to ) the governing relationship in Eq. (2), and the excitation frequency identification scheme used in VIVANA, a preliminary response frequency model for vessel motion-induced VIV in small KC numbers is proposed and illustrated in Figure 1. ...
... The dominant frequency for this case is 0.2 Hz, which is twice that of the vessel motion frequency. This is in accordance with the integral relationship as per Eq (2). The response frequency for the lower part of the riser is affected by the local shedding 8 Copyright © 2017 by ASME frequency distribution, similar to the trend discussed for the validation case. ...
A free-hanging riser is a typical riser configuration seen in the disconnected drilling riser, the water-intake riser and the deep-sea mining riser. In offshore productions, these marine risers will move back and forth in water and further generate an equivalent oscillatory current around themselves, due to the vessel motions. Both in marine operations in the field and model tests, it has been reported that such oscillatory current lead to riser vortex-induced vibration (VIV) and cause structural fatigue damage. Recently, there have been some attempts to numerically predict vessel motion-induced VIV on the compliant production risers, with emphasize on relatively large Keulegan-Carpenter (KC) numbers. In the real marine operations, the risers experience small KC number scenarios during most of their service life. Therefore, the investigation of vessel motion-induced VIV under small KC number is of great significance, especially considering its contribution to fatigue damage. In this paper, numerical investigation of VIV of a free-hanging riser attached to a floating vessel is carried out. A new response frequency model for vessel motion-induced VIV under small KC numbers is proposed and implemented in VIVANA. Validation of the proposed numerical methodology is performed against the published experimental results, where a good agreement is achieved.
... As a matter of fact, Pereira et al. [6] , from a small-scale SCR experiment and using an optical tracking system, were able to group transversal response frequency relations in Sumer and Fredsøe diagrams. Moreover, Wang et al., [7] - [8] naming the phenomenon 'Vessel Motion Induced VIV' (VMI-VIV), unveiled the relationship between the out-of-plane VIV dominant response frequency and the imposed frequency, through a maximum equivalent flow velocity KC number, determining a 'Strouhal-like' number St=0.14 as the proportionality factor. Pereira et al., [6] had obtained St=0. ...
... A set of six immersed and three emerged cameras -Qualisys® -is used to optically track the instantaneous position of reflective targets placed all along the catenary line. In fact, common instrumentation schemes use strain-gages and accelerometers, making the elastica monitoring an indirect process; see for instance, in chronological order, [26] - [31] , [13] - [14] , [7] - [8] . Figure 1 shows a schematic view of the camera assemblage. ...
This paper presents further experimental results of the dynamic response of a small-scale catenary riser model subjected to sinusoidal vertical motion imposed to the top, as a continuation of a previous one, presented at OMAE’2013. In that paper, a general view of an innovative experimental methodology using underwater optical techniques was given, together with some experimental results on VSIV – Vortex Self-Induced Vibrations, also referred to as Heave-Induced Lateral Motion, or Vessel Motion Induced VIV. It was then shown that such a behavior recovered similar ones reported in the technical literature by other authors and resembled fundamental studies, by Sumer and Fredsøe. In the present paper, new experimental tests are reported and analyzed. A similar catenary configuration is assessed. The analysis of VSIV trajectories is made via space-frequency amplitude spectra and space-time amplitude scalograms, revealing rich dynamic responses. The results are meant to serve as an experimental basis, contributing to the understanding of the VSIV phenomenology and to the benchmarking of numerical models.
... This VIV response is named as heave induced lateral motion (HILM) by Cunff et al. (2005) and is named as vortex selfinduced vibration (VSIV) by Fernandes et al. (2008Fernandes et al. ( , 2014. Vessel motion-induced VIV occurs because the riser is exposed to the equivalent oscillatory current due to the relative motion between the oscillating riser and the still water particles around (Wang et al., 2014a(Wang et al., , 2014b(Wang et al., , 2015a(Wang et al., , 2015b. We name such oscillatory current as equivalent current because this current is not physically existed in the environmental conditions, but it has an equivalent effect as oscillatory current acting on the risers. ...
... To further understand vessel motion-induced VIV, Statoil conducted a large-scale model test on a truncated SCR with forced motion at the top of the model (Fu et al., 2013a;Wang 2014a). Previous case study has confirmed that vessel motion-induced VIV was characterized by strongly time-varying features (Wang et al., 2014a(Wang et al., , 2015b. ...
... To further understand vessel motion-induced VIV, Statoil conducted a large-scale model test on a truncated SCR with forced motion at the top of the model (Fu et al., 2013a;Wang 2014a). Previous case study has confirmed that vessel motion-induced VIV was characterized by strongly time-varying features (Wang et al., 2014a(Wang et al., , 2015b. Moreover, vessel motion-induced VIV differs considerably for different test cases, as observed in the equivalent flow field, touch down point variation and top axial tension variation. ...
Recent research has confirmed a new type of vortex-induced vibration (VIV) in steel catenary risers (SCRs), purely caused by vessel motion. Vessel motion-induced VIV occurs because the SCR is exposed to the equivalent oscillating current due to its own motions relative to the still water. Preliminary results indicate that vessel motion-induced VIV is quite different from ocean current-induced VIV and is characterized with distinct time-varying features. In the present study, we aim at further summarizing the dominant parameters that govern the general vessel motion-induced VIV responses. Throughout the comparative studies on the instantaneous and statistical VIV responses including strain, displacement, response frequency, fatigue damage and top tension variation, the maximum Keulegan-Carpenter number and the maximum equivalent current velocity Vn_max are found to be the two dominant parameters that govern the vessel motion-induced VIV responses. Generally speaking, when is sufficiently large (larger than 39 according to the present study), the general vessel motion-induced VIV response is dominated by . However, when is small, the VIV response is less time-varying and shows strong correlation with both and the local number distribution along the SCR. Vessel motion-induced VIV response frequency models are also reviewed and discussed considering different and ranges. Hopefully, these results can provide some general guidelines for future vessel motion-induced VIV prediction and for industrial references.
... Recent research has confirmed a new type of vortex-induced vibration (VIV) under pure vessel motion, known as vessel motion-induced VIV. Vessel motion-induced VIV occurs owing to the equivalent oscillating current generated by the riser-water relative motion, which is typically seen in the compliant production risers like steel catenary riser (SCRs) and steel lazy-wave risers (SLWRs) [1,2]. Vessel motion-induced VIV for compliant risers is characterized with strong time-varying features like amplitude modulation and mode variation. ...
... However, other riser responses, such as internal flow effect and VIVs, were not addressed. Jung et al. [7] carried out a scaled model test on the free-hanging ocean thermal energy conversion riser under the top end forced oscillation with small top KC number (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17) and has roughly found that vessel motion-induced VIV would occur even when the top KC number was as low as 4. Based on the same test data, Kwon et al. [8] further investigated the ocean current effect on the vessel motion-induced VIV responses, and he concluded that the in-line riser response was weakened, but crossflow VIV was strengthened owing to a large relative current velocity. Xiang et al. [9] carried out a series of free-hanging water intake riser model test considering vessel motion and internal flow effect, she compared the numerical and experimental riser response in the riser plane that align with the vessel motion direction and found good agreement. ...
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. Top end of the riser is forced to oscillate or move, in order to simulate vessel motion or ocean current effects. Fiber Brag 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.
... Recent research has confirmed a new type of VIV under pure vessel motion, known as vessel motion-induced VIV. Vessel motion-induced VIV occurs owing to the equivalent oscillating current generated by the riser-water relative motion, which is typically seen in the compliant production risers like steel catenary riser (SCRs) and steel lazy-wave risers (SLWRs) where the riser has a large relative motion with the water particles around [1,2]. Vessel motion-induced VIV for compliant risers is characterized with strong time-varying features. ...
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.
Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
