Forced Vibration Tests for In-Line VIV to Assess Partially Strake-Covered Pipeline Spans

2019 ◽  
Author(s):  
Jie Wu ◽  
Decao Yin ◽  
Elizabeth Passano ◽  
Halvor Lie ◽  
Ralf Peek ◽  
...  
Keyword(s):  
Hydrodynamic Force ◽  
Added Mass ◽  
Optimal Location ◽  
Test Rig ◽  
Towing Tank ◽  
Harmonic Motion ◽  
Intermediate Support ◽  
Series Of Experiments ◽  
Vibration Tests ◽  
Mass Functions

Abstract A series of experiments is performed in which a strake-covered rigid cylinder undergoes harmonic purely in-line motion while subject to a uniform “flow” created by towing the test rig along SINTEF Ocean’s towing tank. These tests are performed for a range of frequencies and amplitudes of the harmonic motion, to generate added-mass and excitation functions are derived from the in-phase and 90° out-of-phase components of the hydrodynamic force on the pipe, respectively. Using these excitation- and added-mass functions in VIVANA together with those from experiments on bare pipe by Aronsen (2007), the in-line VIV response of partially strake-covered pipeline spans is calculated. It is found that as little as 10% strake coverage at the optimal location effectively suppresses pure in-line VIV. Further advantages of strakes rather than intermediate supports to suppress in-line VIV include: strakes are not affected by the scour which can lower an intermediate support (in addition to creating the span in the first place). Further they do not prevent self-lowering of the pipeline or act as a point of concentration of VIV damage as the spans to each side of the intermediate support grow again.

Forced Vibration Tests for In-Line Vortex-Induced Vibration to Assess Partially Strake-Covered Pipeline Spans

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Jie Wu ◽  
Decao Yin ◽  
Elizabeth Passano ◽  
Halvor Lie ◽  
Ralf Peek ◽  
...  
Keyword(s):  
Forced Vibration ◽  
Hydrodynamic Force ◽  
Cross Flow ◽  
Added Mass ◽  
Vortex Induced Vibrations ◽  
Helical Strakes ◽  
Vibration Tests ◽  
Flow Vortex ◽  
Hydrodynamic Data ◽  
Mass Functions

Abstract Helical strakes can suppress vortex-induced vibrations (VIVs) in pipelines spans and risers. Pure in-line (IL) VIV is more of a concern for pipelines than for risers. To make it possible to assess the effectiveness of partial strake coverage for this case, an important gap in the hydrodynamic data for strakes is filled by the reported IL forced-vibration tests. Therein, a strake-covered rigid cylinder undergoes harmonic purely IL motion while subject to a uniform “flow” created by towing the test rig along SINTEF Ocean's towing tank. These tests cover a range of frequencies, and amplitudes of the harmonic motion to generate added-mass and excitation functions are derived from the in-phase and 90 deg out-of-phase components of the hydrodynamic force on the pipe, respectively. Using these excitation- and added-mass functions in VIVANA together with those from experiments on bare pipe by Aronsen (2007 “An Experimental Investigation of In-Line and Combined In-Line and Cross-Flow Vortex Induced Vibrations,” Ph.D. thesis, Norwegian University of Science and Technology, Trondheim, Norway.), the IL VIV response of partially strake-covered pipeline spans is calculated. It is found that as little as 10% strake coverage at the optimal location effectively suppresses pure IL VIV.

FUNDAMENTAL ANALYSIS OF THREE-DIMENSIONAL ‘NEAR FLING’

1993 ◽  
Vol 183 (1) ◽  
pp. 217-248 ◽  
Author(s):  
S. Sunada ◽  
K. Kawachi ◽  
I. Watanabe ◽  
A. Azuma
Keyword(s):  
Numerical Calculation ◽  
Hydrodynamic Force ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Added Mass ◽  
Opening Angle ◽  
Rotation Axes ◽  
Adequate Accuracy ◽  
Series Of Experiments ◽  
The Moment

A series of experiments on three-dimensional ‘near fling’ was carried out. Two pairs of plates, rectangular and triangular, were selected, and the distance between the rotation axes of the two plates of each pair was varied. The motion of the plates as well as the forces and the moment were measured, and the interference between the two plates of a pair was studied. In addition, a method of numerical calculation was developed to aid in the understanding of the experimental results. The interference between the two plates of a pair, which acted to increase both the added mass of each plate and the hydrodynamic force due to dynamic pressure, was noted only when the opening angle between the plates was small. The hydrodynamic forces were strongly influenced by separated vortices that occurred during the rotation. A method of numerical calculation, which took into account the effect both of interference between the plates and of separated vortices, was developed to give adequate accuracy in analyzing beating wings in ‘near fling’.

Dynamics of Continuous-Mode Icebreaking by a Polar-Class Hull—Part 2: Spectral Analysis

1989 ◽  
Vol 33 (03) ◽  
pp. 236-251
Author(s):  
Frederick Stern ◽  
Robert Ettema ◽  
Javier Lazaro
Keyword(s):  
Reasonable Agreement ◽  
Natural Frequencies ◽  
Ice Sheet ◽  
Added Mass ◽  
Dominant Frequency ◽  
Towing Tank ◽  
Damping Coefficients ◽  
Series Of Experiments ◽  
The Mean ◽  
Scale Data

Part 2 of this two-part paper presents additional results from an ice towing-tank study of a Polar-Class hull for two conditions: for one, the hull was free to pitch, heave, and undergo limited roll (free hull); for the other, the hull was restrained from motions (fixed hull). Measurements were made of resistance as well as motions and restraining forces and moments for the free-and fixed-hull conditions, respectively. In Part 1, the values of the mean and standard deviation for both conditions are compared and related to observed patterns of icebreaking. In Part 2, the spectral densities are examined with regard to the natural frequencies of hull motions and frequencies associated with icebreaking pattern to determine the dominant cycles of resistance and motions. A series of experiments was conducted to determine values of zero-speed natural frequencies and added-mass and damping coefficients for ice-covered conditions. The presence of an ice sheet significantly reduces the natural frequencies and increases the added-mass and damping coefficients. It was found that hull motions and icebreaking pattern determined the dominant cycles of resistance for the free hull. Icebreaking frequency, the frequency of individual breaking events, was significant only for thin ice such that significant heave and pitch did not occur. When w b was less than the natural frequencies of coupled heave and pitch amid ice, w the dominant frequency of resistance and motions occurred at integral fractions of usually b/2. The frequencies, (b/n, are associated with the icebreaking pattern, that is, cyclic manner by which hull trim changed as the hull broke and cleared a track through an ice sheet. When b equaled or exceeded to„, the dominant frequency of resistance coincided with The fixed hull responded at higher frequencies than the free hull, usually at u>0. Also, available full-scale data are shown to be in reasonable agreement with the present results for the free hull. Lastly, the principal conclusions of the overall study are summarized and the implications of the present work with regard to the development of prediction methods are discussed.

Interaction Between Two Closely Spaced Azimuthing Thrusters

1998 ◽  
Vol 42 (01) ◽  
pp. 15-32 ◽  
Author(s):  
Paul Brandner ◽  
Martin Renilson
Keyword(s):  
Mathematical Model ◽  
Satisfactory Agreement ◽  
Vehicle Dynamics ◽  
Operating Conditions ◽  
Towing Tank ◽  
Empirical Relations ◽  
Series Of Experiments ◽  
Flow Effects ◽  
Semi Empirical

To assist in predicting the performance of omni-directional propelled vehicles a series of experiments has been conducted to measure the interaction between two closely spaced ductedazimuthing thrusters. The thrusters were tested below a shallow draft ground board in a towing tank at a spacing of approximately 2 propeller diameters. Measurements were made of forces acting on a single thruster for a range of operating conditions and similarly on two thrusters for a range of relative positions. The results show that forces from the trailing thruster are heavily affected by interaction, particularly due to impingement of the race from the leading thruster, where as forces from the leading thruster remain essentially unaffected despite its proximity to the trailing thruster. A semi-empirical mathematical model suitable for simulation of omni-directional vehicle dynamics is presented. The model is based on the trajectory of the race from the leading thruster derived from momentum considerations with additional empirical relations to account for other more minor flow effects. Comparison of the predicted and measured results show satisfactory agreement.

In-Plane Vibration Damping of a U-Tube With Wet and Dry Flat-Bar Supports

2014 ◽  
Author(s):  
Paul A. Feenstra ◽  
Victor P. Janzen ◽  
Bruce A. W. Smith
Keyword(s):  
Energy Dissipation ◽  
Plane Motion ◽  
Test Facility ◽  
Vibration Energy ◽  
Test Rig ◽  
Two Phase ◽  
Support Conditions ◽  
Vibration Tests ◽  
Energy Dissipated ◽  
Steam Generator Tubes

Tests are being planned which will use AECL’s MR-3 Freon test facility and a Multi-Span U-Bend (MSUB) test rig to investigate the dynamics of tube vibration in two-phase flow, in particular those mechanisms that can cause excessive damage to steam-generator tubes. In preparation for the tests, free- and forced-vibration tests were conducted to measure the vibration energy dissipation (damping) of a single U-bend tube in air, with dry and wet anti-vibration bars, under a variety of tube-support conditions. This paper presents the relevant damping mechanisms and documents methods used to conduct the tests and to analyze the energy dissipated at the supports. Results indicate that for in-plane motion without tube-to-support contact, viscous damping related to wet AV B supports is much smaller than guidelines based on other types of supports suggest. To begin to examine the effects of the tube coming into contact with its supports, such as friction-related energy dissipation, the results of tests with light tube-to-support preloads are also presented.

scholarly journals Influence of Pressure on Gas/Liquid Interfacial Area in a Tray Column

2020 ◽  
Vol 10 (13) ◽  
pp. 4617
Author(s):  
Adel Almoslh ◽  
Falah Alobaid ◽  
Christian Heinze ◽  
Bernd Epple
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volumetric Flow Rate ◽  
Interfacial Area ◽  
Gas Flow Rate ◽  
Test Rig ◽  
Flow Rates ◽  
Waste Gas ◽  
Simulated Waste ◽  
Series Of Experiments

The influence of pressure on the gas/liquid interfacial area is investigated in the pressure range of 0.2–0.3 MPa by using a tray column test rig. A simulated waste gas, which consisted of 30% CO2 and 70% air, was used in this study. Distilled water was employed as an absorbent. The temperature of the inlet water was 19 °C. The inlet volumetric flow rate of water was 0.17 m3/h. Two series of experiments were performed; the first series was performed at inlet gas flow rate 15 Nm3/h, whereas the second series was at 20 Nm3/h of inlet gas flow rate. The results showed that the gas/liquid interfacial area decreases when the total pressure is increased. The effect of pressure on the gas/liquid interfacial area at high inlet volumetric gas flow rates is more significant than at low inlet volumetric gas flow rates. The authors studied the effect of decreasing the interfacial area on the performance of a tray column for CO2 capture.

Paper 24: A Study of Column Separation following Valve Closure in a Pipeline Carrying Aviation Kerosine

1969 ◽  
Vol 184 (7) ◽  
pp. 57-64 ◽  
Author(s):  
J. A. Swaffield
Keyword(s):  
Computer Program ◽  
Method Of Characteristics ◽  
Hyperbolic Partial Differential Equations ◽  
Valve Closure ◽  
Test Rig ◽  
Cavity Collapse ◽  
Upstream Side ◽  
Column Separation ◽  
Series Of Experiments ◽  
The Subject

The occurrence of column separation on the upstream side of a valve following valve closure has been the subject of a series of experiments on a test rig utilizing Concorde L56 alloy fuel piping and Esso Aviation Kerosine Specification 2494. A Fortran IV computer program based on the method of characteristics has been employed to solve the quasi-linear hyperbolic partial differential equations governing the propagation of transient pressures and to predict the duration of vapour cavities formed either at the valve or at any point in the pipeline. Comparison of computer and observed results indicates an accuracy within 3 per cent for the first peak following valve closure and for the duration of the vapour cavities, and within 10 per cent for the later pressure peaks following vapour cavity collapse.

scholarly journals Added Mass and Damping of a Vibrating Rod in Confined Viscous Fluids

1976 ◽  
Vol 43 (2) ◽  
pp. 325-329 ◽  
Author(s):  
S. S. Chen ◽  
M. W. Wambsganss ◽  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Cylindrical Shell ◽  
Closed Form Solution ◽  
Added Mass ◽  
Form Solution ◽  
Viscous Fluids ◽  
Series Of Experiments ◽  
Theoretical Results ◽  
Good Agreement

This paper presents an analytical and experimental study of a cylindrical rod vibrating in a viscous fluid enclosed by a rigid, concentric cylindrical shell. A closed-form solution for the added mass and damping coefficient is obtained and a series of experiments with cantilevered rods vibrating in various viscous fluids is performed. Experimental data and theoretical results are in good agreement.

scholarly journals Simplified VIV Response of Partially Strake-Covered Pipe Spans

2021 ◽  
Author(s):  
Ralf Peek ◽  
Decao Yin ◽  
Jie Wu ◽  
Malcolm Carr ◽  
Sze Yu Ang ◽  
...  
Keyword(s):  
Response Function ◽  
Single Mode ◽  
Added Mass ◽  
Mode Analysis ◽  
Frequency Domain Method ◽  
Assessment Practice ◽  
Damping Parameter ◽  
Wave Effects ◽  
Mass Functions ◽  
Forward Extension

A simplified method for the fatigue assessment for partially strake-covered pipeline spans is provided and calibrated so that for the bare pipe case it is consistent with the current DNVGL Recommended Practice (DNVGL-RP-F105). It is based on a Rayleigh-Ritz approximation using the first undamped mode shape. In that sense it is equivalent to a single-mode analysis using Shear7, except that it accounts for frequency-dependent added mass, and the formulation is presented in a compact and convenient non-dimensional form. The method presented may also be considered a simplification of that in Vivana in that it does not account for propagating wave effects, and is therefore named “Sivana”.Like any frequency-domain method Sivana is based on the assumption of harmonic response. This requires excitation and added mass functions that define a harmonic hydrodynamic force as a function of the harmonic motion. On the other hand, current practice by DNVGL-RP-F105 is based on a response function, which gives VIV amplitude as function of reduced velocity and the Scruton mass-damping parameter Ks. To bridge this gap, an inversion technique is developed whereby the excitation function for bare pipe is derived from the DNVGL-RP-F105 response function, such that for bare pipe the Sivana calculation will lead to the same response amplitudes as DNVGL-RP-F105. The Sivana method is illustrated by an example involving a single span with different degrees of strake coverage centered at midspan.Although the Sivana method might be considered a natural and straight-forward extension of current span assessment practice to include partial strake coverage, caution is in order for certain approximations in the DNVGL-RP-F105 response function may be less appropriate for the use in this paper, than for the use envisioned by the developers of the DNVGL guidance.

Hydrodynamics of High-Speed Planing Craft: Savitsky Method and 2D+t Approach

2021 ◽  
Author(s):  
M. Javad Javaherian ◽  
Richard Royce ◽  
Raju Datla ◽  
Christine M. Gilbert
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Hydrodynamic Force ◽  
Prediction Method ◽  
Water Entry ◽  
Planing Craft ◽  
Towing Tank ◽  
Entry Model ◽  
Calm Water

The progressive interest in high-speed planing craft has made it crucial to conduct more accurate assessments of the behavior of these vessels in motion. In this paper, a 2D+t approach is employed to predict the resistance, trim and wetted length of a prismatic planing craft cruising in calm water. Although this approach is based on original Zarnick 2D+t model, the hydrodynamic force is estimated using experimental wedge drop experiments in conjunction with the Logvinovich wedge water entry model. The analysis is repeated employing Savitsky prediction method and results are compared with that of towing tank measurements of Naples series. The comparison shows that the Savitsky prediction results match very well with the experimental data. The 2D+t approach also shows reasonable outcomes for the trim and wetted length. However, this approach slightly underestimates the resistance of the craft at very low Froude numbers.

Sign in / Sign up

Export Citation Format

Share Document