Assessment of VIV Induced Fatigue in Long Free Spanning Pipelines

2003 ◽  
Author(s):  
Kim Mo̸rk ◽  
Olav Fyrileiv ◽  
Muthu Chezhian ◽  
Finn G. Nielsen ◽  
Tore So̸reide
Keyword(s):  
Failure Modes ◽  
Cross Flow ◽  
Computational Procedure ◽  
Design Guidelines ◽  
Model Tests ◽  
The State ◽  
Mode Behavior ◽  
Vortex Induced Vibrations ◽  
Current Design ◽  
Sensitivity Studies

Current design practice for free spanning pipelines is to allow free spans as long as the integrity with respect to potential failure modes are checked and found acceptable. The case study for Ormen Lange (OL) pipelines planned in the deep waters of the Norwegian Sea is associated with a large number of very long free spans, which requires significant intervention work if based on the state-of-practice acceptance criteria. The design philosophy of the state-of-the-art design code DNV-RP-F105 “Free Spanning Pipelines” is applied in combination with the experience gained from dedicated OL model tests. Updated project specific design guidelines with multi-mode behavior, typical for OL long free spans, is taken into account and an updated Cross-Flow (CF) response model has been developed. An approach to select the In-Line (IL) mode excited by CF response is suggested. Methods for combining stresses from multiple active modes have been proposed and tested, for both IL and CF Vortex Induced Vibrations (VIV). Fatigue analysis has also been performed on the stress series measured in the model tests and this has been successfully used to verify and validate the presented computational procedure. Uncertainty in the model test based fatigue estimates has been assessed and sensitivity studies have been carried out. Reasons for deviations and potential problem areas for long free spanning pipelines have been identified.

Model Testing for Vortex Induced Motions of Spar Platforms

2004 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
State Of The Art ◽  
Model Testing ◽  
Model Tests ◽  
The State ◽  
Test Results ◽  
Test Set ◽  
Vortex Induced Vibrations ◽  
Set Up

The state-of-the art in model testing for Vortex Induced Vibrations (VIV) of Spars is presented. Important issues related to Spar VIV model testing are highlighted. The parameters that need to be modeled including hull geometry, strake configuration, mass and mooring properties and, considerations of test set-up and instrumentation are discussed. Results are presented from model tests of an as-built Spar deployed in the Gulf of Mexico. It is shown that the model test results compare well with the VIV responses measured in the field.

Comparison Between Static, Forced Oscillation and Free Oscillation Model Tests for the Assessment of Galloping Instability at High Reynolds Numbers

2013 ◽  
Author(s):  
Alexandre Cinello ◽  
François Pétrié ◽  
Thierry Rippol ◽  
Bernard Molin ◽  
Guillaume Damblans
Keyword(s):  
Cross Sections ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Model Tests ◽  
Square Cylinder ◽  
Vortex Induced Vibrations ◽  
Electric Power Line ◽  
Section Model ◽  
High Reynolds ◽  
Fixed Cylinder

Galloping may take place for non-circular cross sections, such as an ice-coated electric power line or a riser bundle, under current action. This type of instabilities occurs at lower frequency than Vortex Induced Vibrations but with unbounded amplitude, and might be detrimental for riser integrity. In a recent joint industry project, the CITEPH “Gallopan” project, galloping instabilities were investigated for two types of cylinders: an academic square cylinder and a generic riser tower cross section. Model tests and numerical computations were performed to assess the propensity of both cylinders to gallop. Experiments on the square cylinder are reported here. Three types of tests were performed in steady flow: loads measurement on fixed cylinder, at various headings; loads measurement on the cylinder with over imposed cross-flow harmonic oscillations; free transverse oscillations. By using analytical calculations, the ability to predict galloping instability occurrence and amplitude, of each of the three above methods, was compared. Compared to typical results found in literature, these experiments were conducted at a larger scale, and thus with Reynolds number closer to on-site values, i.e. over 105.

Benchmark of Numerical Codes for Coupled CSD/CFD Computations on an Elementary Vortex Induced Vibration Problem

2009 ◽  
Author(s):  
Marie Pomarede ◽  
Elisabeth Longatte ◽  
Jean-Franc¸ois Sigrist
Keyword(s):  
Numerical Study ◽  
Tube Bundle ◽  
Cross Flow ◽  
Practical Interest ◽  
Computational Procedure ◽  
Industrial Applications ◽  
Interface Motion ◽  
Vortex Induced Vibrations ◽  
Flow Induced Vibrations ◽  
Lock In

Numerical simulation of vortex-induced-vibrations (VIV) of an elastically supported rigid circular cylinder in a fluid cross-flow has been thoroughly studied over the past years, both from the experimental and numerical points of view, because of its theoretical and practical interest in the understanding of flow-induced vibrations problems. In this context, the present paper aims at exposing a numerical study based on a coupled fluid-structure simulation, compared with previously published studies [34], [36]. The computational procedure relies on a partitioned method ensuring the coupling between fluid and structure solvers. The fluid solver involves a moving mesh formulation for simulation of the interface motion. Energy exchanges between both systems are ensured through convenient coupling schemes. The present study is devoted to a low Reynolds number configuration ( Re = 100). Cylinder motion magnitude, hydrodynamic forces, oscillation frequency and fluid vortex shedding modes are investigated with the intention to observe the “lock-in” phenomenon. These numerical simulations are proposed for code validation purposes prior to industrial applications to tube bundle configurations [4].

Comparison of Calculated In-Line Vortex Induced Vibrations to Model Tests

2012 ◽  
Author(s):  
Elizabeth Passano ◽  
Carl M. Larsen ◽  
Halvor Lie
Keyword(s):  
Cross Flow ◽  
Added Mass ◽  
Model Tests ◽  
The Finite Element Method ◽  
Response Frequency ◽  
Flow Response ◽  
Vortex Induced Vibrations ◽  
Flow Directions ◽  
The Cross ◽  
Semi Empirical

The purpose of the present paper is to compare vortex-induced vibrations (VIV) in both in-line and cross-flow directions calculated by a semi-empirical computer program to experimental data. The experiments used are the Bearman and Chaplin experiments in which a model of a tensioned riser is partly exposed to current and partly in still water. The VIVANA program is a semi-empirical frequency domain program based on the finite element method. The program was developed by MARINTEK and the Norwegian University of Science and Technology (NTNU) to predict cross-flow response due to VIV. The fluid-structure interaction in VIVANA is described using added mass, excitation and damping coefficients. Later, curves for excitation, added mass and damping for pure in-line VIV response were added. These curves are valid for low current levels, before the onset of cross-flow VIV response. Recently, calculation of response from simultaneous cross-flow and in-line excitation has been included in VIVANA. The in-line response frequency is fixed at twice the cross-flow response frequency and the in-line added mass is adjusted so that this frequency becomes an eigenfrequency. A set of curves based on forces measured during combined cross-flow and inline motions are used. At present, the in-line excitation curves are not dependent on the cross-flow response amplitude. In the paper, in-line and cross-flow response predicted by VIVANA will be compared to the Bearman and Chaplin model tests. The choice of added mass and excitation coefficients will be discussed.

scholarly journals Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

2012 ◽  
Author(s):  
Halvor Lie ◽  
Henning Braaten ◽  
Vikas Gopal Jhingran ◽  
Octavio E. Sequeiros ◽  
Kim Vandiver
Keyword(s):  
Cross Flow ◽  
Model Tests ◽  
Test Material ◽  
Test Program ◽  
Research Activity ◽  
Good Test ◽  
Vortex Induced Vibrations ◽  
Set Up ◽  
Oil Company ◽  
Made In

Despite of considerable research activity during the last decades considerable uncertainties still remain in prediction of Vortex Induced Vibrations (VIV) of risers. Model tests of risers subjected to current have been shown to be a useful method for investigation of the VIV behavior of risers with and without suppression devices. In order to get further insight on VIV of risers, an extensive hydrodynamic test program of riser models subjected to vortex-induced vibrations was undertaken during the winter 2010 by Shell Oil Company. The VIV-model test campaign was performed in the MARINTEK Offshore Basin Laboratory. A new test rig was constructed and showed to give good test conditions. Three different 38m long riser models were towed horizontally at different speeds, simulating uniform and linearly varying sheared current. Measurements were made In-Line (IL) and Cross-Flow (CF) of micro bending strains and accelerations along the risers. The test program compromised about 400 tests, which give a rich test material for further studies. In the present paper the test set-up and program are presented and selected results are reported.

VIV of Free Spanning Pipelines: Comparison of Response From Semi-Empirical Code to Model Tests

2010 ◽  
Author(s):  
Elizabeth Passano ◽  
Carl M. Larsen ◽  
Jie Wu
Keyword(s):  
Cross Flow ◽  
Model Tests ◽  
Test Series ◽  
The Finite Element Method ◽  
Field Development ◽  
Long Span ◽  
Flow Response ◽  
Pipe Model ◽  
Vortex Induced Vibrations ◽  
Semi Empirical

The purpose of this paper is to compare predictions of vortex-induced vibrations (VIV) from a semi-empirical program to experimental data. The data is taken from a VIV model test program of a free span pipeline using a long elastic pipe model. Both in-line (IL) and cross-flow (CF) vibrations are compared. The Norwegian Ormen Lange field development included pipelines laid on very uneven seafloors, resulting in many free spans. As part of the preparations for this field development, VIV model tests of single- and multi-span pipelines were carried out at MARINTEK for Norsk Hydro, which later became a part of Statoil. The VIVANA program is a semi-empirical frequency domain program based on the finite element method. The program was originally developed by MARINTEK and the Norwegian University of Science and Technology (NTNU) to predict cross-flow response due to VIV. The fluid-structure interaction in VIVANA is described using added mass, excitation and damping coefficients. Default curves are available or the user may input other data. VIVANA originally included only cross-flow excitation but pure in-line excitation was later added. Recently, simultaneous cross-flow and in-line excitation has also been included. At present, the excitation in the cross-flow and in-line directions is not coupled. Coefficients for simultaneous cross-flow and in-line excitation have been proposed and are available in VIVANA. In this paper, response predicted by VIVANA has been compared to the Ormen Lange model tests for selected test series. The analyses with pure IL loading gave good estimates of IL response up to and beyond the start of CF response. The analyses with combined CF and IL loading gave good response estimates for the test series with a long span. The experiments with short spans tended to give CF and IL mode 1 response while the present version of the program gave IL response at higher modes. The present coefficient based approach is, however, promising. Further work should aim at establishing better coefficients and to understanding the interaction between CF and IL response.

Front steering design guidelines formulation for e-scooters considering the influence of sitting and standing riders on self-stability and safety performance

2021 ◽  
pp. 095440702199217
Author(s):  
Milan Paudel ◽  
Fook Fah Yap
Keyword(s):  
Preventive Measures ◽  
Recent Trend ◽  
Dynamic Performance ◽  
Design Guidelines ◽  
Safety Performance ◽  
Design Parameters ◽  
Single Track ◽  
Standing Posture ◽  
Last Mile ◽  
Current Design

E-scooters are a recent trend and are viewed as a sustainable solution to ease the first and last mile problem in modern transportation. However, an alarming rate of accidents, injuries, and fatalities have caused a significant setback for e-scooters. Many preventive measures and legislation have been put on the e-scooters, but the number of accidents and injuries has not reduced considerably. In this paper, the current design approach of e-scooters has been analyzed, and the most common range of design parameters have been identified. Thereafter, validated mathematical models have been used to quantify the performance of e-scooters and relate them with the safety aspects. Both standing and seated riders on e-scooters have been considered, and their influence on the dynamic performance has been analyzed and compared with the standard 26-in wheel reference safety bicycle. With more than 80% of the accidents and injuries occurring from falling or colliding with obstacles, this paper tries to correlate the dynamics of uncontrolled single-track vehicles with the safety performance of e-scooters. The self-stability, handling, and braking effect have been considered as major performance matrices. The analysis has shown that the current e-scooter designs are not as stable as the reference safety bicycle. Moreover, these e-scooters have been found unstable within the most common range of legislated riding velocity. The results corroborate with the general perception that the current designs of e-scooters are less stable, easy to lose control, twitchy, or wobbly to ride. Furthermore, the standing posture of the rider on the e-scooter has been found dangerous while braking to avoid any disturbances such as potholes or obstacles. Finally, the front steering design guidelines have been proposed to help modify the current design of e-scooters to improve the dynamic performance, hence the safety of the e-scooter riders and the surroundings.

scholarly journals Fluid-Structure Energy Transfer of a Tensioned Beam Subject to Vortex-Induced Vibrations in Shear Flow

2011 ◽  
Author(s):  
Remi Bourguet ◽  
Michael S. Triantafyllou ◽  
Michael Tognarelli ◽  
Pierre Beynet
Keyword(s):  
Energy Transfer ◽  
Shear Flow ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Structural Vibrations ◽  
Fluid Structure ◽  
Vortex Induced Vibrations ◽  
Linear Shear ◽  
Structural Responses ◽  
Lock In

The fluid-structure energy transfer of a tensioned beam of length to diameter ratio 200, subject to vortex-induced vibrations in linear shear flow, is investigated by means of direct numerical simulation at three Reynolds numbers, from 110 to 1,100. In both the in-line and cross-flow directions, the high-wavenumber structural responses are characterized by mixed standing-traveling wave patterns. The spanwise zones where the flow provides energy to excite the structural vibrations are located mainly within the region of high current where the lock-in condition is established, i.e. where vortex shedding and cross-flow vibration frequencies coincide. However, the energy input is not uniform across the entire lock-in region. This can be related to observed changes from counterclockwise to clockwise structural orbits. The energy transfer is also impacted by the possible occurrence of multi-frequency vibrations.

Vortex-Induced Vibrations of a Cylinder at Subcritical Reynolds Number

2011 ◽  
Author(s):  
Yoann Jus ◽  
Elisabeth Longatte ◽  
Jean-Camille Chassaing ◽  
Pierre Sagaut
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Cross Flow ◽  
Physical Analysis ◽  
Arbitrary Lagrangian Eulerian ◽  
Vortex Induced Vibrations ◽  
Low Mass

The present work focusses on the numerical study of Vortex-Induced Vibrations (VIV) of an elastically mounted cylinder in a cross flow at moderate Reynolds numbers. Low mass-damping experimental studies show that the dynamic behavior of the cylinder exhibits a three-branch response model, depending on the range of the reduced velocity. However, few numerical simulations deal with accurate computations of the VIV amplitudes at the lock-in upper branch of the bifurcation diagram. In this work, the dynamic response of the cylinder is investigated by means of three-dimensional Large Eddy Simulation (LES). An Arbitrary Lagrangian Eulerian framework is employed to account for fluid solid interface boundary motion and grid deformation. Numerous numerical simulations are performed at a Reynolds number of 3900 for both no damping and low-mass damping ratio and various reduced velocities. A detailed physical analysis is conducted to show how the present methodology is able to capture the different VIV responses.

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