Wyniki wyszukiwania - BazTech

1

Investigation of asymmetric twin-rudder load behaviour through free-running model tests

Efremov Dobrin, Milanov Evgeni

Polish Maritime Research

|

2023

|

nr 3

4--11

EN

During tight manoeuvres, twin-screw ships equipped with two rudders located in the propeller slip stream experience a fairly large imbalance in the hydrodynamic loads on the propeller and rudders. To investigate the phenomenon of rudder asymmetric load in some depth, manoeuvring experiments based on a free-running model were set up in which the kinematics of the model, the forces on the rudder and the stock moment were recorded. In parallel, with the aim of obtaining an exact estimation of free-stream characteristics of the rudder blade, corresponding wind tunnel experiments were also performed. Based on the results of this investigation, an analysis of the interaction effects within the hull-propeller-rudder system was performed and some conclusions were drawn.

2

Effects of rudder and blade pitch on hydrodynamic performance of marine propeller using CFD

Quang Pham Ky, Hung Phan Van, Cong Nguyen Chi, Tung Trinh Xuan

Polish Maritime Research

|

2022

|

nr 2

55--63

EN

The use of computational fluid dynamics (CFD) to predict internal and external flows has risen dramatically in the past decade. This research aims to use the commercial software, ANSYS Fluent V.14.5, to illustrate the effects of the rudder and blade pitch on the hydrodynamic performance of the marine propeller by experimenting with propellers and rudders of the M/V Tan Cang Foundation ship, which has designed conditions as follows: diameter of 3.65 m; speed of 200 rpm; average pitch of 2.459 m; boss ratio of 0.1730. Using CFD, the characteristic curves of the marine propeller and some important results showed that the maximum efficiency of the propeller is 0.66 with the open water propeller and 0.689 with the rudder‒propeller system at the advance ratio of 0.6. The obtained outcomes of this research are a significant foundation to calculate and design an innovative kind of propulsion for ships with high performance.

3

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.

4

Różne rozwiązania konstrukcyjne sterów jako sposób ograniczania zużycia paliwa na statkach morskich

Giernalczyk M., Górski Z., Krefft J.

Logistyka

|

2015

|

nr 6

1415--1420, CD

PL

Wprowadzony w życie 19 maja 2005 roku Załącznik VI Konwencji MARPOL dotyczący zapobiegania zanieczyszczania powietrza przez statki, wymusił na armatorach stosowanie rozwiązań zmierzających do ograniczenia emisji do atmosfery szkodliwych substancji. Poziom emisji tych związków jest proporcjonalny do ilości spalanego paliwa, stąd poszukiwane są rozwiązania pozwalające ograniczyć jego zużycie. Pośród czynników mających znaczący wpływ na zużycie paliwa jest opór statku. Jedną ze składowych tego oporu stanowi opór steru. W artykule przedstawiono zasadę działania steru płetwowego oraz strukturę sił powstałych w wyniku rozkładu ciśnień w strumieniu wody opływającym wychyloną płetwę, w tym siłę oporu. Przedstawiono różne rozwiązania konstrukcyjne sterów biernych i aktywnych. Zwrócono uwagę na elementy konstrukcje sterów mające wpływ na ograniczanie oporu podczas eksploatacji statku. Na koniec podano przykłady aplikacji opisanych rozwiązań na współczesnych jednostkach pływających.

EN

Annex VI of the MARPOL Convention concerning prevention of air pollution from ships, in force since May 19th 2005, has forced the ship owners to use means for reduction of environment harmful substances emitted into the atmosphere. The emission level of the harmful substances is proportional to the ship’s fuel consumption. Therefore the new solutions are developed to reduce fuel consumption with its application into the marine environment. The ship’s resistance is one of the factors significantly influencing the fuel consumption. The rudder resistance is one of the ship’s total drag. The principle of the passive blade rudder and the phenomenon of the created forces structure as a result of pressure distribution in the water flow along the laid rudder blade, including the resistance force have been presented. Different construction of the passive blade and active rudder types has been discussed in the paper. Structural rudder elements that influence the reduction of drag effect during the ship’s operation were highlighted. The examples of their application in the contemporary oceangoing ships have been raised at the end of the paper.

5

Dynamic interaction of the cavitating propeller tip vortex with the rudder

Szantyr J. A.

Polish Maritime Research

|

2007

|

nr 4

10-14

EN

The hydrodynamic interaction between the ship propeller and the rudder has many aspects. One of the most interesting is the interaction between the cavitating tip vortex shed from the propeller blades and the rudder. This interaction leads to strongly dynamic behaviour of the cavitating vortex, which in turn generates unusually high pressure pulses in its vicinity. Possibly accurate prediction of these pulses is one of the most important problems in the hydrodynamic design of a new ship. The paper presents a relatively simple computational model of the propeller cavitating tip vortex behaviour close to the rudder leading edge. The model is based on the traditional Rankine vortex and on the potential solution of the dynamics of the cylindrical sections of the cavitating kernel passing through the strongly variable pressure field in the vicinity of the rudder leading edge. The model reproduces numerically the experimentally observed process of initial compression of the vortex kernel in the high pressure region near the stagnation point at the rudder leading edge and subsequent explosive growth of the kernel in the low pressure region further downstream. Numerical simulation of this process enables computation of the additional pressure pulses generated due to this phenomenon and transmitted onto the hull surface. This new numerical model of the cavitating tip vortex is incorporated in the modified unsteady lifting surface program for prediction of propeller cavitation, which has been successfully used in the process of propeller design for several years and which recently has been extended to include the effects of propeller – rudder interaction. The results of calculations are compared with the experimental measurements and they demonstrate reasonable agreement between theory and physical reality.

6

Mutual hydrodynamic interaction between the operating propeller and the rudder

Szantyr J. A.

Archives of Civil and Mechanical Engineering

|

2007

|

Vol. 7, no 3

191-203

EN

The paper presents a description of the algorithm and computer program developed for numerical analysis of the hydrodynamic interaction between operating propeller and ship rudder. The program is based on unsteady lifting surface model representing the propeller and on boundary element model rep resenting the rudder. The program accepts arbitrary geometry of both the rudder and the propeller as the input data. Interaction with the ship hull is taken into account in the form of given non-uniform vclocity field of the ship wake. The mutual hydrodynamic interaction is taken into account by simultaneous solution of the unsteady kinematic boundary condition on both objects. The results of ca1culation include time-dependent pressure distribution on the propeller and on the rudder together with fluctuating hydrodynamic forces on both objects. Apart from that the program is capable of detecting and describing the dynamic development of different forms of the cavitation phenomena on the propeller and on the rudder. The paper includes the results of calculation of the hydrodynamic characteristics and cavitation phenomena of different propeller-rudder configurations. These results are compared with experimental data wherever available. This comparison confirms the effectiveness of the described computation method as the tool for design and analysis of the propeller-rudder configurations.

PL

Referat przedstawia opis algorytmu i programu komputerowego do analizy numerycznej oddziaływania hydrodynamicznego pomiędzy pracującą śrubą a sterem. Program jest oparty na niestacjonarnej powierzchni nośnej reprezentującej śrubę i na metodzie elementów brzegowych do reprezentacji steru. Danymi wejściowymi są dowolna geometria śruby i dowolna geometria steru. Oddziaływanie kadłuba statku jest brane pod uwagę w postaci niejednorodnego pola prędkości strumienia nadążającego. Wzajemne oddziaływanie hydrodynamiczne jest uwzględniane poprzez jednoczesne rozwiązanie niestacjonarnego kinematycznego warunku brzegowego na sterze i na śrubie. Wyniki obliczeń obejmują zmienne w czasie rozkłady ciśnienia na śrubie i na sterze wraz z wynikającymi z nich siłami hydrodynamicznymi. Ponadto program może wykrywać i opisywać różne formy dynamicznie zmiennych zjawisk kawitacyjnych występujących na sterze i na śrubie oraz wyznaczać ich hydrodynamiczne skutki. Referat zawiera wyniki obliczeń charakterystyk hydrodynamicznych i zjawisk kawitacyjnych różnych konfiguracji ster-śruba. Wyniki obliczeń zostały porównane z dostępnymi rezultatami badań eksperymentalnych. Porównanie to potwierdza skuteczność przedstawionej metody obliczeniowej jako narzędzia do projektowania i analizy konfiguracji śruba-ster.

7

Calculation of the influence of propeller operation on the hydrodynamic characteristics of the rudder

Hang T.

Polish Maritime Research

|

2001

|

Vol. 8, nr 2

3-9

EN

The paper presents a lifting surface method for calculation of the hydrodynamic characteristics of the rudder in the propeller slipstream. Flow velocity induced by the propeller in given points on the rudder is calculated. Pressure distribution, lift and drag of the rudder is computed with taking into account propeller interaction. The calculation results show good consistence with experimental data.