Wyniki wyszukiwania - BazTech

1

Numerical investigating the effect of water depth on ship resistance using RANS CFD method

Hoa Nguyen Thi Ngoc, Vu Bich Ngoc, Tran Ngoc Tu, Chien Nguyen Manh, Le Tat Hien

Polish Maritime Research

|

2019

|

nr 3

56--64

EN

On inland waterways the ship resistance and propulsive characteristics are strictly related to the depth of the waterway, thus it is important to have an understanding of the influence of water depth on ship hydrodynamic characteristics. Therefore, accurate predictions of hydrodynamic forces in restricted waterways are required and important. The aim of this paper is investigating the capability of the commercial unsteady Reynolds– Averaged Navier–Stokes (RANS) solver to predict the influence of water depth on ship resistance. The volume of fluid method (VOF) is applied to simulate the free surface flow around the ship. The hull resistance in shallow and deep water is compared. The obtained numerical results are validated against related experimental studies available in the literature.

2

Hull resistance of an inland waterway vessel in model scale and in full scale

Tabaczek T., Zawiślak M.

Polish Maritime Research

|

2018

|

S 1

80--84

EN

Data from model tests of an inland waterway vessel in shallow water have been used by the authors to prepare the resistance prediction in full scale. The common ITTC-1978 extrapolation procedure was applied using form factor determined according to the Prohaska method and, separately, by fitting the approximation function to resistance data. At the same time a series of CFD computations of ship flow has been carried out in model scale and in full scale, with double-body model as well as including the effect of free surface. The results of computations were used to determine total resistance and form factor. The values of form factor determined using different methods are similar and relatively high in comparison to values being applied to conventional sea going ships. Resistance prediction according to the ITTC-1978 with form factor was compared to prediction without form factor. The relative difference of resistance amounts 28% at ship speed of 10 km/h and 24% at ship speed of 12 km/h.

3

Comparison of selected parametric methods for prediction of inland waterways ship hull resistance in towing tank test

Karczewski A., Kozak J.

Polish Maritime Research

|

2018

|

S 1

63--67

EN

In the paper selected approximate methods for calculation of inland waterways ship resistance and their verification by towing tests, compared on the example of a small urban ferry, are presented. The test results are made for both the bare hull and the hull with appendages (skeg, azimuthal propeller). Significant differences between results of the theoretical methods and experimental ones, especially in the case of the model with skegs and propulsion, are pointed out. The purposefulness of using several parametric methods and the use of average results at the preliminary design stage were also discussed.

4

An approximate method for calculating total ship resistance on a given shipping route under statistical weather conditions and its application in the initial design of container ships

Szelangiewicz T., Żelazny K.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2015

|

nr 44 (116)

99--106

EN

During ship design, its service speed is one of the crucial parameters that determine its future operational profitability. As sufficiently exact calculation methods applicable to preliminary design stage are lacking, the so-called contract speed, the speed a ship reaches in calm water, is usually specified during the draft stage. The service speed obtainable by a ship under real weather conditions (mainly wind and waves) is one of the most important parameters influencing a ship’s profitability on a given shipping route. This paper presents a parametric model of calculating total ship resistance on a given shipping route under actual weather conditions (wind, waves, sea current), that could be useful in the initial design of container ships.

5

Methods of calculating ship resistance on limited waterways

Skupień E., Prokopowicz J.

Polish Maritime Research

|

2014

|

nr 4

12--17

EN

Nowadays predicting transportation costs is more and more important. Most significant part of inland navigation’s costs are the costs of fuel. Fuel consumption is related to operating conditions of ship’s propulsion system and its resistance. On inland waterways the ship resistance is strictly related to the depth of the waterway. There is a tendency to build a formula that allows its user to calculate the resistance of any inland waterway vessel, but researches claim that most of them are accurate only for particular types of ships and/or operating conditions. The paper presents selected methods of calculating ship resistance on inland waterways. These methods are examined for different types of ships and different conditions using results of model tests. The performed comparison enabled selecting the best option for pushboats and pushed barge trains, but also showed that any of the tested methods is good enough to be used for calculating the resistance of motor cargo vessels. For this reason, based on known equations and using the regression method, the authors have formulated a new method to calculate the resistance of motor cargo vessels on limited waterway. The method makes use of ship’s geometry and depth of waterway in relation to ship’s speed. Correlating the ship’s speed with its resistance and going further with fuel consumption, enables to calculate the costs of voyage depending on the delivery time. The comparison of the methods shows that the new equation provides good accuracy in all examined speed ranges and all examined waterway depths.