scholarly journals EVALUATION OF INFLUENCE OF CONTAINER�S CENTER OF GRAVITY POSITION ON CONTAINER SHIP�S METACENTRIC HEIGHT

Author(s):  
Ruslan Stanislavovich Tsarik ◽  
◽  
Denis Aleksandrovich Akmaykin ◽  
Author(s):  
Ivan N. Porciuncula ◽  
Claudio A. Rodríguez ◽  
Paulo T. T. Esperança

Along its lifetime, an offshore unit is subjected to several equipment interventions. These modifications may include large conversions in loco that usually are not adequately documented. Hence, the accurate determination of the platform's center of gravity (KG) is not possible. For vessels with low metacentric height (GM), such as semisubmersibles, Classification Societies penalize the platform's KG, inhibiting the installation of new equipment until an accurate measurement of KG is provided, i.e., until an updated inclining test is performed. For an operating semisubmersible, the execution of this type of test is not an alternative because it implies in removing the vessel from its in-service location to sheltered waters. Relatively recently, some methods have been proposed for the estimation of KG for in-service vessels. However, as all of the methods depend on accurate measurements of inclination angles and, eventually, on numerical tools for the simulation of vessel dynamics onboard, they are not straightforward for practical implementation. The objective of the paper is to present a practical methodology for the experimental determination of KG, without the need of accurate measurements of inclinations and/or complex numerical simulations, but based on actual operations that can be performed onboard. Indeed, the proposed methodology relies on the search, identification, and execution of a neutral equilibrium condition where, for instance, KG = KM. The method is exemplified using actual data of a typical semisubmersible. The paper also numerically explores and discusses the stability of the platform under various conditions with unstable initial GM, as well as the effect of mooring and risers.


2020 ◽  
Vol 180 ◽  
pp. 02003
Author(s):  
Mihail-Vlad Vasilescu ◽  
Ionut Voicu ◽  
Cornel Panait ◽  
Violeta-Vali Ciucur

This article is presenting the influence on the stability of a container ship, by connecting four modern Flettner rotors, as wind energy capturing system. Modern Flettner rotors, are energy power generators. They are one of the various equipment used to capture and harness wind energy. By reading the article, the reader can discover what are the forces which influence the modern Flettner rotors and how they influence the ship stability.This article major points are: calculation the influence of the modern Flettner rotors on the ship transverse and longitudinal stability, calculation of the ship new displacement, new draft, new metacentric height and period of rolling.


1997 ◽  
Vol 36 (04/05) ◽  
pp. 356-359 ◽  
Author(s):  
M. Sekine ◽  
M. Ogawa ◽  
T. Togawa ◽  
Y. Fukui ◽  
T. Tamura

Abstract:In this study we have attempted to classify the acceleration signal, while walking both at horizontal level, and upstairs and downstairs, using wavelet analysis. The acceleration signal close to the body’s center of gravity was measured while the subjects walked in a corridor and up and down a stairway. The data for four steps were analyzed and the Daubecies 3 wavelet transform was applied to the sequential data. The variables to be discriminated were the waveforms related to levels -4 and -5. The sum of the square values at each step was compared at levels -4 and -5. Downstairs walking could be discriminated from other types of walking, showing the largest value for level -5. Walking at horizontal level was compared with upstairs walking for level -4. It was possible to discriminate the continuous dynamic responses to walking by the wavelet transform.


2020 ◽  
Vol 20 (3) ◽  
pp. 343-353
Author(s):  
Ngo Van He ◽  
Le Thi Thai

In this paper, a commercial CFD code, ANSYS-Fluent has been used to investigate the effect of mesh number generated in the computed domain on the CFD aerodynamic performances of a container ship. A full-scale model of the 1200TEU container ship has been chosen as a reference model in the computation. Five different mesh numbers for the same dimension domain have been used and the CFD aerodynamic performances of the above water surface hull of the ship have been shown. The obtained CFD results show a remarkable effect of mesh number on aerodynamic performances of the ship and the mesh convergence has been found. The study is an evidence to prove that the mesh number has affected the CFD results in general and the accuracy of the CFD aerodynamic performances in particular.


2013 ◽  
Vol 12 (3) ◽  
Author(s):  
Iskendar Iskendar ◽  
Andi Jamaludin ◽  
Paulus Indiyono

This paper describes hydrodynamic model tests of Wing in Surface Effect (WiSE) Craft. These craft  was fitted with  stephull  form in different location on longitudinal flat bottom (stepedhull planning craft) to determine the influences of sticking and porpoising motion performances. These motions are usually occured when the craft start to take-off from water surfaces. The test models with scale of 1 : 7 were comprised of 4 (four) stephull models and 1 (one) non-stephull model  as a comparative study. The hydrodynamic  tests were performed with craft speed of 16 – 32 knots (prototype values) in Towing Tank at UPT. Balai Pengkajian dan Penelitian Hidrodinamika (BPPH), BPPT, Surabaya. The resistance (drag) was measured by dynamo meter and the trim of model (draft changing at fore and aft  of model due to model speed) was measured by trim meter. By knowing the value of model trim, the wetted surface area can be determined. Then, the lift forces were calculated based on these measured values. The model test results were presented on tables and curves.  Test results show that models  with step located far away from center of gravity of the WiSE craft tend to porpoising and sticking condition, except if the step location on the below of these center of gravity. While model without step tends to sticking conditions.


2010 ◽  
Vol 8 (2) ◽  
pp. 803
Author(s):  
Ramli Usman ◽  
Achmad As'ad Sonief ◽  
Bambang Indrayadi

PT. Ima Montaz Sejahtera merupakan suatu Perusahaan Industri Air Minum Dalam Kemasan (AMDK) dengan merk “Mount Agua” dan perusahaan ini menghasilkan produk berupa produk gallon 19 liter, produk botol 1500 ml, produk botol 600 ml, dan produk gelas 240 ml. Pabrik PT. Ima Montaz Sejahtera memiliki dua buah gudang yaitu gudang material dan gudang produk jadi, didalam pengoperasian proses produksi banyak waktu yang terbuang untuk mengangkut material dari gudang ke mesin produksi dan ini disebabkan letak gudang material jauh dari mesin produksi dan juga dalam mengangkut material dari gudang ke mesin produksi harus melalui gudang produk jadi sehingga mengganggu aktifitas proses produksi. Metode yang digunakan pada penelitian ini menggunakan metode center of gravity yaitu menentukan titik pusat letak gudang baru berdasarkan tata letak mesin-mesin produksi.Dengan meningkatnya waktu produksi maka dengan sendirinya kapasitas produksi juga meningkat untuk produk gallon 19 liter sebesar 36 gallon per minggu (0,490 %), produk botol 1500 ml sebesar 211 karton per minggu (2,475 %), produk botol 600 ml sebesar 71 karton per minggu (1,172 %), dan produk gelas 240 ml sebesar 186 karton per minggu(0,731 %).Kata Kunci: Optimalisasi, Tata Letak Gudang, Centre of Gravity, Lay Out.


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