Study on the Hydrodynamic Characteristics for Heave Plate Structure of Truss Spar

2010 ◽  
Author(s):  
Wenjun Shen ◽  
Yougang Tang ◽  
Liqin Liu
Keyword(s):  
Numerical Simulations ◽  
Forced Oscillation ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Coefficients ◽  
Plate Structure ◽  
Plate Spacing ◽  
Mesh Method ◽  
Truss Spar ◽  
Heave Plate

The hydrodynamic characteristics of heave plates are studied in this paper. Firstly, different motion amplitudes and plate spacing influencing hydrodynamic coefficients are considered. Secondly, heave plates with different thicknesses are calculated, the case of edges with inclined form for heave plate is also taken into account. Numerical simulations are made for the plate forced oscillation, employing the dynamic mesh method and UDF (User defined functions). The values of Cm and Cd for heave plate are calculated. It is found that, in a certain amplitude range, Cm increases with increasing of amplitudes, Cd decreases with increasing of amplitudes. The values of Cm and Cd increase with increasing of plate spacing. Furthermore with the same effective thickness, the hydrodynamic performance of heave plate with inclined form is improved greatly.

Numerical and Experimental Investigation on Hydrodynamic Characteristics of FLNG With an Account of the Inner-Tank Sloshing

2011 ◽  
Author(s):  
Wenhua Zhao ◽  
Jianmin Yang ◽  
Zhiqiang Hu ◽  
Tao Peng
Keyword(s):  
Numerical Simulations ◽  
Model Tests ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Fast Fourier Transformation ◽  
Motion Responses ◽  
Comparison Results ◽  
New Type ◽  
Lng Liquefaction ◽  
Tank Sloshing

FLNG is a new type of floating LNG platform which is ship-shaped FPSO hull equipped with LNG storage tanks and liquefaction plants and has been developed as an alternative to long pipelines to LNG liquefaction plant on land for stranded offshore fields. Different to the conventional FPSO, the hydrodynamic performance of the being-proposed FLNG can be significantly affected by the inner-tank liquid sloshing, due to the fact that LNG performs better liquidity than crude oil. In order to investigate the hydrodynamic characteristics of FLNG with large hull and high center of gravity, a series of numerical simulations on an FLNG designed by CNOOC and MARIC were conducted with the help of the well-known code WADAM. In addition, corresponding model tests on the same vessel with solid ballast were completed, serving as a verification of the numerical simulations. In order to inspect the sloshing effects of inner tanks on the global motion responses of the FLNG vessel, model tests with liquid ballast were also conducted. Comparisons were made between numerical and experimental results with methods of Fast Fourier Transformation technology and spectral analysis. The numerical simulation results were in good accordance with those of the model tests, which proves the feasibility of the numerical simulations. Furthermore, the effects of the inner tank sloshing on the FLNG hydrodynamic characteristics were summed up. Conclusions obtained from the comparison results would be of significant importance for the design of the FLNG system.

Investigation of the Hydrodynamic Characteristics of Asymmetric Cross-Sections Advancing in Regular Waves

2011 ◽  
Author(s):  
Sergio Ribeiro e Silva ◽  
Emre Uzunoglu ◽  
Carlos Guedes Soares ◽  
Adolfo Maro´n ◽  
Cesar Gutierrez
Keyword(s):  
Cross Sections ◽  
Forced Oscillation ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Coefficients ◽  
Parametric Rolling ◽  
Captive Model Tests ◽  
Strip Theory ◽  
Added Masses ◽  
Decay Tests ◽  
Hull Forms

A series of experiments were carried out to assess the instantaneous hydrodynamic coefficients and the parametric rolling characteristics of a C11 class container vessel model. The experiments consisted of captive model tests at various heel angles, forced oscillation tests, free roll decay tests and parametric rolling tests. The results obtained from the forced oscillation tests in calm water on symmetric (upright) and asymmetric (heeled) cross-sections are discussed in here. The main objective of the forced oscillation tests was to obtain the heave, roll and pitch added masses and damping coefficients for two different speeds and also three different amplitudes of forced motions. The most important aspect was to assess the influence of taking instantaneous cross-section into account on calculation of these hydrodynamic coefficients. In addition, these tests allowed the identification of the level of non-linear effects with the amplitude of the forced motions for both symmetric and asymmetric hull forms. The experimental data obtained is compared with the results from two strip theory codes for symmetric and asymmetric cross-sections.

Experimental Investigation on Hydrodynamics of a Fish Cage Floater-net System in Oscillatory and Steady Flows by Forced Oscillation Tests

2014 ◽  
Vol 58 (01) ◽  
pp. 20-29
Author(s):  
Shixiao Fu ◽  
Yuwang Xu ◽  
Ke Hu ◽  
Qian Zhong ◽  
Runpei Li
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Oscillatory Flow ◽  
Forced Oscillation ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Steady Flows ◽  
Steady Current ◽  
Mass Coefficient ◽  
Added Mass Coefficient

In this article, the hydrodynamic characteristics of a floater-net system in oscillatory and steady flows are investigated through forced oscillation experiments in a towing tank. The effects of Keulegan-Carpenter number, Reynolds number, and reduced velocity are studied. Also, hydrodynamic forces on the floater and net are compared in detail to analyze their respective contributions to the total drag force. The results indicate that in oscillatory flow, the added mass coefficient of the floater is larger than that of the floater-net system, whereas the drag coefficient is smaller. The proportion of the drag force exerted on the floating cylinder reaches its maximum in oscillatory flow and its minimum in steady current flow. In addition, the reduced velocity has a very clear influence on the hydrodynamic performance of the floater-net system; specifically, the drag coefficient in oscillatory flow becomes smaller as reduced velocity increases.

Hydrodynamic characteristics of vertical and quadrant face pile supported breakwater under oblique waves

2021 ◽  
pp. 147509022110313
Author(s):  
T J Jemi Jeya ◽  
V Sriram ◽  
V Sundar
Keyword(s):  
Experimental Study ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Scattering Parameter ◽  
Oblique Waves ◽  
Test Conditions ◽  
Relative Water ◽  
Identical Test ◽  
Run Up ◽  
Water Depths

This paper presents the results from a comprehensive experimental study on the Quadrant Face Pile Supported Breakwater (QPSB) in two different water depths exposed to three different oblique wave attacks. The results are compared with that for a Vertical face Pile Supported Breakwater (VPSB) for identical test conditions. The paper compares the reflection coefficient, transmission coefficient, energy loss coefficient, non-dimensional pressure, and non-dimensional run-up as a function of the relative water depth and scattering parameter. The results obtained for QPSB are validated with existing results. The salient observations show that QPSB experiences better hydrodynamic performance characteristics than the VPSB under oblique waves.

RANS Study on Hydrodynamic Characteristics of Flapped Rudders

2018 ◽  
Author(s):  
Jialun Liu ◽  
Robert Hekkenberg ◽  
Bingqian Zhao
Keyword(s):  
Yangtze River ◽  
Area Ratio ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Coefficients ◽  
Sectional Area ◽  
The Yangtze River ◽  
Long Distance ◽  
Ansys Fluent ◽  
Rans Simulations ◽  
Rudder Angle

Ships that equipped with flapped rudders have better manoeuvring performance than ships fitted with traditional spade rudders. Moreover, this advantage is achieved without significantly affecting the ship’s resistance during normal cruising. Flapped rudders are, therefore, favourable for ships that require high manoeuvring performance and sail long distance. Nowadays, there is a trend of using twin flapped rudders on newly built inland vessels in the Yangtze River. To properly design these ships and analyse their manoeuvring performance, the hydrodynamic characteristics of the flapped rudders are required. In this paper, a RANS study is performed to analyse the impacts of the three main properties of a flapped rudder on its hydrodynamic coefficients. The target properties are the rudder profile, the flap-linkage ratio (the flapped angle relative to the rudder chord line divided by the applied rudder angle), and the flap-area ratio (the sectional area of the flap divided by the total sectional area). The RANS simulations are carried out with commercial meshing tool ANSYS Meshing and CFD solver ANSYS Fluent.

Forced oscillation experiments

1991 ◽  
Vol 334 (1634) ◽  
pp. 199-211
Keyword(s):  
Numerical Methods ◽  
Water Depth ◽  
Forced Oscillation ◽  
Vertical Plane ◽  
Forced Oscillations ◽  
Hydrodynamic Characteristics ◽  
Scale Models ◽  
Ship Speed

Forced oscillation experiments with scale models are carried out to determine hydrodynamic characteristics of ships, with respect to motions in waves or steering and manoeuvring qualities. Depending on the considered motion components, in a horizontal or vertical plane, various methods are used to induce forced oscillations which are discussed briefly. Some results of forced oscillation experiments are presented as examples of this technique and compared with calculations based on numerical methods. The comparisons include, among others, the effects of ship speed and restricted water depth.

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