Wyniki wyszukiwania - BazTech

1

Application of 2nd generation stability code for 7600DWT bulk carrier with high value of GM, being in dead ship condition in irregular waves

Kacprzak Paweł

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2023

|

nr 75 (147)

14--19

EN

The main issue of this article is to apply and investigate the application of second stability criteria for bulk carriers in typical loading conditions sailing in irregular waves. The author, by the use of linear strip theory, calculates the significant amplitudes of the ship roll with respect to wave height, incident wave angles, and mean sea period. A basic stability analysis, in this case, could be insufficient when considering other related factors like cargo shift, taking up water on the weather deck, wind gusts, inaccuracy of transverse metacentric height, and the case of changing transverse metacentric height in long-crested waves. This article shows that, in some waving conditions, the weather criteria based on standard assumptions of the ISC 2008 may be insufficient. The application of the author’s method of safety margin may increase vessel safety in view of weather criteria.

2

Efficient Positioning of Two Long-Range Passenger Aircraft in Formation Flight

Antczak Adam, Lasek Maciej, Sibilski Krzysztof

Transactions on Aerospace Research

|

2022

|

Nr 3 (268)

21--31

EN

In today’s world, each airline is forced to look for new savings opportunities. One of the methods may be the use of formation flights in daily flight operations, which may allow a reduction in fuel consumption by several percentages. The paper presents the genesis of how the consideration of such flights and the possibility of their implementation in an airline had started. The leader’s plane generates vortices, which, with the proper alignment of the planes to one another, can reduce the drag on the wingman. However, the wrong position may not only have no positive effect but also may be a threat to stable wingman flight. The article presents a method of using these vortices in such a way as to have a positive impact on the aerodynamics of the wingman. A favourable position in the vertical and horizontal axes will be determined in relation to the vortex generated by the leader’s plane in order to obtain the greatest benefit in reducing fuel consumption. The paper presents an operational analysis of the possibility of maintaining such a distance to obtain profit on fuel but also to ensure the highest level of safety of the flight.

3

Determination of seakeeping performance for a case study vessel by the strip theory method

Niklas Karol, Karczewski Artur

Polish Maritime Research

|

2020

|

nr 4

4--16

EN

The increase of seakeeping performance is of particular importance for car and passenger ferries, service ships in the gas and oil extraction industry and offshore wind power farm industry, as well as for special purpose ships (including military applications). In the water areas of the Baltic Sea, North Sea, and Mediterranean Sea, which are characterised by a short and steep wave, the hull shape has a substantial impact on the operational capacity and propulsion efficiency of the ship, as well as on comfort and safety of navigation. The article analyses selected aspects of seakeeping for four variants of a selected case study vessel, indicating practical limitations of the strip method. The analysed aspects included hull heaving and pitching, added resistance, Motion Thickness Indicator (MSI), and Subjective Magnitude (SM). Experimental tests were also performed in the towing tank. Their comparison with the numerical results has indicated high inaccuracy of the strip method. What is more, the simplified representation of hull shape used in the strip method makes it impossible to analyse the effect of hull shape changes on the predicted seakeeping characteristics. Especially for the case of head wave, neglecting highly non-linear phenomena, such as slamming or head wave breaking, in strip method-based computer simulations will significantly decrease the reliability of the obtained results. When using the strip method, the seakeeping analysis should be complemented with model tests in a towing tank, or by another more complex numerical analysis, such as CFD for instance.

4

Modelowanie nieustalonych sił aerodynamicznych na nieodkształcalnych skrzydłach machających

Lasek M., Pietrucha J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2001

|

z. 15

203-208

PL

Opisano osobliwości aerodynamiki ptaków z punktu widzenia wyznaczania sił aerodynamicznych. Rozważono dwie metody: pierwsza z nich to zmodyfikowana metoda pasowa, w której współczynniki siły nośnej i siły oporu są obliczane dla wartości lokalnej prędkości opływu i lokalnego kąta natarcia (w oparciu o nieliniowe charakterystyki aerodynamiczne profilu skrzydła). Druga z rozważanych metod jest niestacjonarną metodą panelową, w której zastosowano technikę "time-stepping" do wyznaczania zwijającego się śladu wirowego za skrzydłem.

EN

Features of birds aerodynamics from aerodynamic forces calculations point of view are described. Two methods will be taken into account, namely: the modified strip theory and unsteady non-linear panel method. Modified strip theory, where the lift and drag coefficient are considered as equal to the product of the local angle of attack and the wing-lift curve slope, the latter being corrected for aspect ratio. In the range of unsteady, non-linear panel methods, "time stepping" approach to determine the rolling-up of the vortex wake is used.