scholarly journals Experimental and Numerical Study of the Hydroelastic Response of a River-Sea-Going Container Ship

2020 ◽  
Vol 8 (12) ◽  
pp. 978
Author(s):  
Yiwen Wang ◽  
Weiguo Wu ◽  
C. Guedes Soares
Keyword(s):  
Numerical Study ◽  
Arbitrary Lagrangian Eulerian ◽  
Strip Theory ◽  
Slamming Load ◽  
High Frequency Vibrations ◽  
Response Amplitude Operators ◽  
Improved Model ◽  
Hydroelastic Response ◽  
Wave Induced ◽  
Good Agreement

The hydroelastic behaviour of a river-sea-going ship hull is analysed experimentally and numerically. A segmented ship model connected by a steel backbone is tested in regular waves, and its high-frequency vibrations such as springing and whipping responses are identified. The hydroelastic response of the ship is numerically calculated using a hydroelastic time domain method based on strip theory, which is extended to include an improved model of the slamming load. The slamming forces in the bow section are determined using the Modified Longvinovich Model (MLM) instead of the Von Karman model. The vertical motions and wave-induced loads are calculated and compared with the experimental results. The response amplitude operators of the vertical loads and the high-order harmonics are analysed under different speeds, showing good agreement with the experiments. The slamming loads on the bow section of a river-to-sea ship are predicted utilizing the MLM model and compared with the Arbitrary Lagrangian Eulerian algorithm by LS-DYNA and with the measured results.

scholarly journals Ship Loading Influence on the Slamming Impact of Typical Sections of an S-175 Container Ship

2020 ◽  
Vol 8 (3) ◽  
pp. 163
Author(s):  
Guanghua He ◽  
Binyang Xie ◽  
Wei Wang ◽  
Shuang Liu ◽  
Penglin Jing
Keyword(s):  
Loading Condition ◽  
Early Stage ◽  
Water Entry ◽  
Container Ship ◽  
Arbitrary Lagrangian Eulerian ◽  
Explicit Finite Element ◽  
Loading Effects ◽  
Sectional Shape ◽  
Wave Induced ◽  
Good Agreement

This paper investigates the influence of ship-loading condition on slamming during water entry. Three typical sections of the S-175 container ship, namely the bow, parallel middle body and stern, under three different loading conditions are studied. Full-sized models are established and simulated by commercial software LS-DYNA based on the explicit finite element method (FEM) using the arbitrary Lagrangian–Eulerian (ALE) algorithm. At first, validation is carried out by simulating the Wave Induced Loads on Ships Joint Industry Project II (WILS JIP-II) ship section entering the water and by verifying that the response is in good agreement with published experimental data. Then, nine different cases with three typical sections of the container ship and three different loadings, including the no-load (lightship weight), half-load and full-load weights of the ship, are investigated. Finally, the influence of the ship loading and sectional shape on the water impacts is analyzed and discussed. The present study is useful for the analysis of loading effects on ship slamming at the early stage of ship design.

scholarly journals A Comparative Study of Computational Methods for Wave-Induced Motions and Loads

2021 ◽  
Vol 9 (1) ◽  
pp. 83 ◽  
Author(s):  
Jens Ley ◽  
Ould el Moctar
Keyword(s):  
Numerical Methods ◽  
Comparative Study ◽  
Computational Methods ◽  
Boundary Element Methods ◽  
Navier Stokes ◽  
Strip Theory ◽  
Time Histories ◽  
Structural Failures ◽  
Response Amplitude Operators ◽  
Wave Induced

Ship hull structural damages are often caused by extreme wave-induced loads. Reliable load predictions are required to minimize the risk of structural failures. One conceivable approach relies on direct computations of extreme events with appropriate numerical methods. In this perspective, we present a systematic study comparing results obtained with different computational methods for wave-induced loads and motions of different ship types in regular and random irregular long-crested extremes waves. Significant wave heights between 10.5 and 12.5 m were analyzed. The numerical methods differ in complexity and are based on strip theory, boundary element methods (BEM) and unsteady Reynolds-Averaged Navier–Stokes (URANS) equations. In advance to the comparative study, the codes applied have been enhanced by different researchers to account for relevant nonlinearities related to wave excitations and corresponding ship responses in extreme waves. The sea states investigated were identified based on the Coefficient of Contribution (CoC) method. Computed time histories, response amplitude operators and short-term statistics of ship responses and wave elevation were systematically compared against experimental data. While the results of the numerical methods, based on potential theory, in small and moderate waves agreed favorably with the experiments, they deviated considerably from the measurements in higher waves. The URANS-based predictions compared fairly well to experimental measurements with the drawback of significantly higher computation times.

scholarly journals Research on Hydroelastic Response of an FMRC Hexagon Enclosed Platform

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1110
Author(s):  
Wei-Qin Liu ◽  
Luo-Nan Xiong ◽  
Guo-Wei Zhang ◽  
Meng Yang ◽  
Wei-Guo Wu ◽  
...  
Keyword(s):  
Time Domain ◽  
Numerical Models ◽  
Structural Response ◽  
Deep Ocean ◽  
Surface Model ◽  
Large Area ◽  
Floating Structure ◽  
Small Depth ◽  
Response Amplitude Operators ◽  
Hydroelastic Response

The numerical hydroelastic method is used to study the structural response of a hexagon enclosed platform (HEP) of flexible module rigid connector (FMRC) structure that can provide life accommodation, ship berthing and marine supply for ships sailing in the deep ocean. Six trapezoidal floating structures constitute the HEP structure so that it is a symmetrical very large floating structure (VLFS). The HEP has the characteristics of large area and small depth, so its hydroelastic response is significant. Therefore, this paper studies the structural responses of a hexagon enclosed platform of FMRC structure in waves by means of a 3D potential-flow hydroelastic method based on modal superposition. Numerical models, including the hydrodynamic model, wet surface model and finite element method (FEM) model, are established, a rigid connection is simulated by many-point-contraction (MPC) and the number of wave cases is determined. The load and structural response of HEP are obtained and analyzed in all wave cases, and frequency-domain hydroelastic calculation and time-domain hydroelastic calculation are carried out. After obtaining a number of response amplitude operators (RAOs) for stress and time-domain stress histories, the mechanism of the HEP structure is compared and analyzed. This study is used to guide engineering design for enclosed-type ocean platforms.

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.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Added Resistance in Seaways and its Impact on Yacht Performance

2007 ◽  
Author(s):  
Kai Graf ◽  
Marcus Pelz ◽  
Volker Bertram ◽  
H. Söding
Keyword(s):  
Strong Impact ◽  
Wave Spectra ◽  
Linear Extensions ◽  
Added Resistance ◽  
Optimum Length ◽  
Prediction Program ◽  
Strip Theory ◽  
Velocity Prediction ◽  
Added Resistance In Waves ◽  
Response Amplitude Operators

A method for the prediction of seakeeping behaviour of sailing yachts has been developed. It is based on linear strip theory with some non-linear extensions. The method is capable to take into account heeling and yawing yacht hulls, yacht appendages and sails. The yacht's response amplitude operators (RAO) and added resistance in waves can be predicted for harmonic waves as well as for natural wave spectra. The method is used to study added resistance in seaways for ACC-V5 yachts of varying beam. Results are used for further VPP investigations. The AVPP velocity prediction program is used to study optimum length to beam ratio of the yachts depending on wind velocity and upwind to downwind weighting. This investigation is carried out for flat water conditions as well as for two typical wave spectra. The results show that taking into account added resistance in seaways has a strong impact on predicted performance of the yacht.

An experimental and numerical study of the resonant flow between a hull and a wall

2021 ◽  
Vol 930 ◽  
Author(s):  
I.A. Milne ◽  
O. Kimmoun ◽  
J.M.R. Graham ◽  
B. Molin
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Numerical Study ◽  
Numerical Models ◽  
Vertical Wall ◽  
Liquefied Natural Gas ◽  
Narrow Gap ◽  
Image Velocimetry ◽  
High Degree ◽  
Wave Induced

The wave-induced resonant flow in a narrow gap between a stationary hull and a vertical wall is studied experimentally and numerically. Vortex shedding from the sharp bilge edge of the hull gives rise to a quadratically damped free surface response in the gap, where the damping coefficient is approximately independent of wave steepness and frequency. Particle image velocimetry and direct numerical simulations were used to characterise the shedding dynamics and explore the influence of discretisation in the measurements and computations. Secondary separation was identified as a particular feature which occurred at the hull bilge in these gap flows. This can result in the generation of a system with multiple vortical regions and asymmetries between the inflow and outflow. The shedding dynamics was found to exhibit a high degree of invariance to the amplitude in the gap and the spanwise position of the barge. The new measurements and the evaluation of numerical models of varying fidelity can assist in informing offshore operations such as the side by side offloading from floating liquefied natural gas facilities.

Performance of rectangular labyrinth weir- an experimental and numerical study

2022 ◽  
Author(s):  
Mosbah Ben Said ◽  
Ahmed Ouamane
Keyword(s):  
Discharge Capacity ◽  
Numerical Study ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Experimental Models ◽  
Absolute Relative Error ◽  
Labyrinth Weir ◽  
Specific Discharge ◽  
Labyrinth Weirs ◽  
Good Agreement

Abstract Labyrinth weirs are commonly used to increase the capacity of existing spillways and provide more efficient spillways for new dams due to their high specific discharge capacity compared to the linear weir. In the present study, experimental and numerical investigation was conducted to improve the rectangular labyrinth weir performance. In this context, four configurations were tested to evaluate the influence of the entrance shape and alveoli width on its discharge capacity. The experimental models, three models of rectangular labyrinth weir with rounded entrance and one with flat entrance, were tested in rectangular channel conditions for inlet width to outlet width ratios (a/b) equal to 0.67, 1 and 1.5. The results indicate that the rounded entrance increases the weir efficiency by up to 5%. A ratio a/b equal to 1.5 leads to an 8 and 18% increase in the discharge capacity compared to a/b ratio equal to 1 and 0.67, respectively. In addition, a numerical simulation was conducted using the opensource CFD OpenFOAM to analyze and provide more information about the flow behavior over the tested models. A comparison between the experimental and numerical discharge coefficient was performed and good agreement was found (Mean Absolute Relative Error of 4–6%).

THE INFLUENCE OF CENTRE BOW LENGTH ON SLAMMING LOADS AND MOTIONS OF LARGE WAVE-PIERCING CATAMARANS

2021 ◽  
Vol 160 (A1) ◽  
Author(s):  
J R Shahraki ◽  
G A Thomas ◽  
M R Davis
Keyword(s):  
Wave Height ◽  
Full Scale ◽  
Bending Moments ◽  
Regular Waves ◽  
Large Wave ◽  
Towing Tank ◽  
Segmented Model ◽  
Model Experiments ◽  
Slamming Load ◽  
Wave Induced

The effect of various centre bow lengths on the motions and wave-induced slamming loads on wave-piercing catamarans is investigated. A 2.5 m hydroelastic segmented model was tested with three different centre bow lengths and towed in regular waves in a towing tank. Measurements were made of the model motions, slam loads and vertical bending moments in the model demi-hulls. The model experiments were carried out for a test condition equivalent to a wave height of 2.68 m and a speed of 20 knots at full scale. Bow accelerations and vertical bending moments due to slamming showed significant changes with the change in centre bow, the longest centre bow having the highest wave-induced loads and accelerations. The increased volume of displaced water which is constrained beneath the bow archways is identified as the reason for this increase in the slamming load. In contrast it was found that the length of centre bow has a relatively small effect on the heave and pitch motions in slamming conditions.

Experimental, numerical and parametric studies on stress concentration factors of T-joints under tension

2021 ◽  
pp. 136943322110499
Author(s):  
Feleb Matti ◽  
Fidelis Mashiri
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Numerical Study ◽  
Hot Spot ◽  
Joint Models ◽  
Element Analysis ◽  
T Joints ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Good Agreement

This paper investigates the behaviour of square hollow section (SHS) T-joints under static axial tension for the determination of stress concentration factors (SCFs) at the hot spot locations. Five empty and corresponding concrete-filled SHS-SHS T-joint connections were tested experimentally and numerically. The experimental investigation was carried out by attaching strain gauges onto the SHS-SHS T-joint specimens. The numerical study was then conducted by developing three-dimensional finite element (FE) T-joint models using ABAQUS finite element analysis software for capturing the distribution of the SCFs at the hot spot locations. The results showed that there is a good agreement between the experimental and numerical SCFs. A series of formulae for the prediction of SCF in concrete-filled SHS T-joints under tension were proposed, and good agreement was achieved between the maximum SCFs in SHS T-joints calculated from FE T-joint models and those from the predicted formulae.

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