Komponen Gaya Hambatan Kapal Cepat

Ship resistance is very importance to learn as we need to calculate the main power of the ship to reach the defined speed. In fact ship resistance has several components, which one and each other make interaction and mechanism in the emerging of ship resistance. This paper will focus on the explanation of the component of ship resistance in the case of high speed vessel

On the importance of antifouling coatings regarding ship resistance and powering

This paper aims to introduce one of the latest investigations on development of marine antifouling coatings and also to demonstrate the importance of the type of antifouling coatings on fouling accumulation and ship resistance/powering. First, marine biofouling and fouling prevention methods are reviewed. A recent research study (EU FP7 FOUL-X-SPEL Project) concerning a novel and environmentally friendly antifouling coating is presented and discussed. Next, a case study is carried out to assess the effect of fouling on ship resistance and powering. A vessel is selected and the roughness on the hull surface induced by different level of fouling is considered. The increase in frictional resistance and effective power is evaluated for each particular case by using boundary layer similarity law analysis and experimental data. The results emphasise that the type of antifouling coatings has a great importance on the amount of fouling accumulation, hence on ship performance especially in low speed

Ship resistance in ice floe covered waters

The developmemt of new analytical and numerical methods for the calculation of ship resistance in broken, pack icef or ice floe covered waters, as well as full scale and model testing, has been addressed in this dissertation. -- In this study three methods for the calculation of ship resistance are presented. The first analytical formulation of ship resistance in ice fragments (The Micro Model) is based on the calculation of energy loss due to an impact between an advancing ship and an ice floe. Based on The Kinetic Theory of Gases (molecule collision and pressure) the number of possible ice floes colliding with the ship, in a given time, was estimated and consequently total ship energy loss and ship resistance was determined. The second approach for the calculation of ship resistance due to ice floes (The Macro Model) was formulated and developed based on the analysis of water drag of displaced ice floes. The Macro Model is based on the prediction of the total forces acting on the ship as a result of the displacement of a large number of ice floes out of the ship's path. -- Both analytical models have been formulated to account for both the ship characteristics and ice cover properties. Numerical calculations of ship resistance for existing ship hull forms have been performed and presented, in this study, using the newly developed models. -- A numerical calculation method based on the distinct element method has been introduced in this dissertation as a new approach for the calculation of ship resistance in ice floe or pack ice. -- Besides the analytical and the numerical approaches developed, a number of model test experiments were conducted in simulated broken ice cover to measure ship resistance increase due to ice fragments. -- A Full-Scale field measurement program was beyond the scope of this study. However, results from existing full scale tests, available in the literature, have been collected, analysed and presented in this study. -- Results from the new analytical and numerical models, model test experiments, and full scale field measurements, have been presented in this study to verify the validity of the different approaches. -- This study has developed new methods or tools for calculating the ship resistance in broken ice. This study has shown that it is possible to predict with reasonable accuracy, the magnitude of ship resistance in a given ice floe or pack ice cover

Ship resistance analysis using CFD simulations in Flow-3D

While designing the power requirements of a ship, the most important factor to be considered is the ship resistance, or the sea drag forces acting on the ship. It is important to have an estimate of the ship resistance while designing the propulsion system since the power required to overcome the sea drag forces contribute to ‘losses’ in the propulsion system. There are three main methods to calculate ship resistance: Statistical methods like the Holtrop-Mennen (HM) method, numerical analysis or CFD (Computational Fluid Dynamics) simulations, and model testing, i.e. scaled model tests in towing tanks. At the start of the design stage, when only basic ship parameters are available, only statistical models like the HM method can be used. Numerical analysis/ CFD simulations and model tests can be performed only when the complete 3D design of the ship is completed. The present paper aims at predicting the calm water ship resistance using CFD simulations, using the Flow-3D software package. A case study of a roll-on/roll-off passenger (RoPax) ferry was investigated. Ship resistance was calculated at various ship speeds. Since the mesh affects the results in any CFD simulation, multiple meshes were used to check the mesh sensitivity. The results from the simulations were compared with the estimate from the HM method. The results from simulations agreed well with the HM method for low ship speeds. The difference in the results was considerably high compared to the HM method for higher ship speeds. The capability of Flow-3D to perform ship resistance analysis was demonstrated

Unsteady effects during resistance tests on a ship model in a towing tank

It is known that there are oscillations in the wave resistance during the constantvelocity phase of a towing-tank resistance test on a ship model. In this work, the unsteady thin-ship resistance theory has been applied to this case. The results have been compared with experiment data obtained using a towing carriage the velocity history of which can be programmed. It is demonstrated here that generally excellent correlation exists between the theory and the experiments. In particular, one can predict the influence of Froude number, rate of acceleration, and type of smoothing of the acceleration on the characteristics of the oscillations. These characteristics include the amplitude, rate of decay, frequency, and phasing of the oscillations in the curve of wave resistance versus time

Hydrodynamic Characteristics of 30 GT Fishing Ship Hull Form in Sulawesi Waters

This study aims to determine the hydrodynamic characteristics of the 30 GT fishing ship hull form, operating around Sulawesi waters. The hydrodynamic study includes determinations of; i) ship main dimensions, ii) ship resistance and power, iii) ship stability and maneuvering. The main dimensions identifications were based on a several fishing ship. Ship resistance and power aproximination used Holtrop method. The investigation of ship stability and maneuvering was based on the IMO criteria. Three samples of the fishing ship were investigated. The results of the hydrodynamic analysis showed that the influences of B/T ratio is significant. Properly selecting the B/T ratio on fishing ships can be improved in power reduction and possible increase in safety of shi

Hydrodynamic Characteristics of 30 GT Fishing Ship Hull Form in Sulawesi Waters

This study aims to determine the hydrodynamic characteristics of the 30 GT fishing ship hull form, operating around Sulawesi waters. The hydrodynamic study includes determinations of; i) ship main dimensions, ii) ship resistance and power, iii) ship stability and maneuvering. The main dimensions identifications were based on a several fishing ship. Ship resistance and power aproximination used Holtrop method. The investigation of ship stability and maneuvering was based on the IMO criteria. Three samples of the fishing ship were investigated. The results of the hydrodynamic analysis showed that the influences of B/T ratio is significant. Properly selecting the B/T ratio on fishing ships can be improved in power reduction and possible increase in safety of shi

PENGGUNAAN METODE KOMPUTERISASI DALAM PENENTUAN TAHANAN KAPAL TANKER

The ship resistance is influential to choose the ship's main engine, especially tankers that have large block coefficients. In general, ship resistance was obtained by modeling the vessel on a certain scale and then testing on the experimental tank. However, this test requires high funding, because testing requires special places such as towing tanks that have expensive operating costs. This research is intended to get ship prisoner with computerized method for tanker ship. Then the result is validated by Holtrop mathematical approximation method. The result of computerized method for speed 11.4 knots got the value of ship resistance is 86.2 KN. While the method of mathematical approach generated ship resistance is 74.38 KN. So the ship's resistance used to determine the tanker machine is 86.2 KN. Keywords: Ship resistance, tanker, computerize

Improving the Accuracy of Ship Resistance Prediction Using Computational Fluid Dynamics Tool

The ship resistance prediction using CFD tool has become an accepted method over the last decade; however, the CFD-based ship resistance results are not always accurate. This paper presents the approach of determining the input parameters of the CFD solution for ship resistance prediction, including of size and boundary conditions of the computational domain, and parameters of turbulent model in accordance with the geometric characteristics of hull to improve the accuracy of CFD-based resistance values for a specific ship type. Two same type of fishing vessels named FAO 72 and FAO 75 which are tested in towing tank are chosen as the computed ship to apply this approach for resistance prediction accurately. The CFD-based resistance results of these vessels are compared with corresponding model testing results to analyze accuracy and reliability of this approach as well as discussing the effect of the initial parameters of the CFD solution on the resistance results as mentioned. The research results shown that the accuracy of three dimensions (3D) model of computational ship, the appropriate values of computational domain size and turbulent model parameters for resistance prediction using CFD are the input factor to improve the accuracy of resistance values. Especially the specific values of computational domain size and turbulent model parameters are presented in this paper will be the input parameters to predict the resistance using CFD for the fishing vessels with the same geometric characteristics as the computed ship