Forced motion experiments using cylinders with helical strakes

Senga, Hidetaka; Larsen, Carl M.

doi:10.1016/j.jfluidstructs.2016.11.004

Cited by 21 publications

(5 citation statements)

References 8 publications

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“…Besides, the excitation coefficients on the strakes almost always keep in negative as expected, and are in the same ranges as those from forced oscillation tests [13], and more fluctuations and larger amplitude are observed.…”

Section: Discussionsupporting

confidence: 78%

Hydrodynamic Coefficients of a Flexible Pipe With Staggered Buoyancy Elements and Strakes Under VIV Conditions

Lie

et al. 2017

Volume 2: Prof. Carl Martin Larsen and Dr. Owen Oakley Honoring Symposia on CFD and VIV

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A 38m long flexible pipe with staggered buoyancy modules and strakes has been tested in the ocean basin of SINTEF Ocean (former Marintek) for VIV investigation of a lazy wave riser. In this paper the inverse analysis method was presented and applied into the investigation of the hydrodynamic force coefficients along this tested flexible pipe with the measured responses as inputs. The feasibility of the inverse analysis method is firstly validated by numerical simulations. The distributions of the added mass and excitation coefficients along the flexible pipe with staggered buoyancy modules and strakes are then investigated. The identified coefficients are validated by check of the natural frequencies and responses of the model, and are finally compared against those from the forced oscillation tests.

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Section: Discussionsupporting

confidence: 78%

Hydrodynamic Coefficients of a Flexible Pipe With Staggered Buoyancy Elements and Strakes Under VIV Conditions

Lie

et al. 2017

Volume 2: Prof. Carl Martin Larsen and Dr. Owen Oakley Honoring Symposia on CFD and VIV

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“…Drengsrud [10] studied the modelling of strakes in VIVANA-TD. The hydrodynamic coefficients were estimated from analytical formulations proposed by Nestegård et al [11], which shows reasonable agreement with experimental results [47].…”

Section: Empirical Parameters For Strakessupporting

confidence: 69%

Time Domain Viv Analysis Tool Vivana-Td: Validations and Improvements

Jin¹,

Lie²,

Wu³

et al. 2021

Preprint

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An empirical time-domain (TD) vortex-induced vibration (VIV) prediction model has been implemented in a software called VIVANA-TD based on its earlier development by Thorsen at NTNU. It models the synchronization of VIV loads and structural responses with a set of empirical parameters generalized from model tests. Combining this time domain hydrodynamic load model with a non-linear finite element structural model makes it possible to account for structural nonlinearities and time-varying flow.A joint industry project (JIP), i.e., Lazy Wave Riser JIP has been organized to improve the design basis for SLWRs. This JIP is executed by SINTEF Ocean with support from NTNU. The industry participants are Equinor, BP, Subsea7, Kongsberg Maritime and Aker Solutions. The overall objective of this JIP is to systematically validate VIVANA-TD, in order to establish it as an industrial tool for VIV prediction. It is also aimed to improve the empirical basis and methods for calculation of VIV of deepwater steel lazy wave risers (SLWRs).In the present paper, the validation study is presented for selected model tests in constant flow conditions with uniform and sheared profiles. The test model includes bare pipe, pipe with partial strake coverage and riser model with staggered buoyancy elements. The empirical parameters have been generalized based on extensive model test data. Limitations and improvement of the model have been also been explored. The results show that the present TD model can represent reasonably the VIV loads and that the prediction has good agreement with measurements in general.

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“…Passive flow control does not require external supply of energy to work but relies on modifications of the shape or some other characteristic of the exterior surface of the body interacting with fluid flow. Helical strakes are often wrapped around long flexible pipelines that bring oil from the sea bottom so as to suppress unwanted flow-induced vibrations [7][8][9]. As an alternative to passively control the flow around a cylindrical structure, its surface can be fully or partially covered with hydrophobic or hairy-like microfiber coatings [10][11][12], or the geometry of the cylinder exterior be modified to have mild disturbances along its span [13,14].…”

Section: Flow Control Definitions and Preliminary Remarksmentioning

confidence: 99%

Active Control of Bluff-Body Flows Using Plasma Actuators

Konstantinidis

2019

Actuators

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Actuators play an important role in modern active flow control technology. Dielectric barrier discharge plasma can be used to induce localized velocity perturbations in air, so as to accomplish modifications to the global flow field. This paper presents a selective review of applications from the published literature with emphasis on interactions between plasma-induced perturbations and original unsteady fields of bluff-body flows. First, dielectric barrier discharge (DBD)-plasma actuator characteristics, and the local disturbance fields these actuators induce into the exterior flow, are described. Then, instabilities found in separated flows around bluff bodies that controlled actuation should target at are briefly presented. Key parameters for effective control are introduced using the nominally two-dimensional flow around a circular cylinder as a paradigm. The effects of the actuator configuration and location, amplitude and frequency of excitation, input waveform, as well as the phase difference between individual actuators are illustrated through examples classified based on symmetry properties. In general, symmetric excitation at frequencies higher than approximately five times the uncontrolled frequency of vortex shedding acts destructively on regular vortex shedding and can be safely employed for reducing the mean drag and lift fluctuations. Antisymmetric and symmetric excitation at low frequencies of the order of the natural frequency can amplify the wake instability and increase the mean and fluctuating aerodynamic forces, respectively, due to vortex locking-on to the excitation frequency or its subharmonics. Results from several studies show that the geometry and arrangement of the electrodes is of utmost significance. Power consumption is typically very low, but the electromechanical efficiency can be optimized by input waveform modulation.

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Forced motion experiments using cylinders with helical strakes

Cited by 21 publications

References 8 publications

Hydrodynamic Coefficients of a Flexible Pipe With Staggered Buoyancy Elements and Strakes Under VIV Conditions

Hydrodynamic Coefficients of a Flexible Pipe With Staggered Buoyancy Elements and Strakes Under VIV Conditions

Time Domain Viv Analysis Tool Vivana-Td: Validations and Improvements

Active Control of Bluff-Body Flows Using Plasma Actuators

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