Wyniki wyszukiwania - BazTech

1

Dynamic motions of the cabin mounted on the mono-hull planing boat using suspension system in waves

Bahrami Hassan, Ghassemi Hassan

Polish Maritime Research

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2022

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nr 1

13--25

EN

The necessity for higher speed and appropriate seakeeping performance of boats has led to extensive research. Hence, this research mainly discusses the optimal behavior of the boat against motions. From an economic point of view, reducing motions of the boat minimizes the damage caused by shock and vibration to the boat and equipment. Other benefits include comfort and safety and, as a result, improved human operating ability. Suspension systems are rarely used as motion controller in a boat. In multi-hull boats, the hull is an inseparable part of the vessels, so the wave will affect crew and equipment. This paper proposes and evaluates a novel concept boat equipped with a suspended cabin. The hull and superstructure (cabin) are separated in this new form by a simple passive suspension system. This study used numerical analysis to examine the seakeeping performance of the planing boat Fridsma model equipped with a passive suspension system under regular wave conditions. The hydrodynamics of the planing hull were modeled using commercial software, STAR-CCM+. For simulation of the passive suspension system between boat and cabin, MATLAB software was used. Results showed that the motion of the cabin, which is where the crew and equipment are located, decreased in regular waves.

2

The hydrodynamic resistance of stepped planing hulls under different geometrical and physical conditions

Najafi Amin, Nowruzi Hashem, Salari Mahmoud, Kazemi Hamid

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2019

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nr 58 (130)

24--31

EN

In this paper, the hydrodynamic resistance of one-step planing craft has been experimentally investigated under different geometrical and physical conditions. For this to be accomplished, a Fridsma body model with different deadrise angles was considered. Moreover, the effect of the longitudinal distance of the step from the transom and the step height on the hydrodynamic resistance of a stepped planing craft has been evaluated at different hull velocities. According to the experimental results, frictional resistance can be enhanced by decreasing the height of the step. However, a greater total resistance can be obtained by increasing the longitudinal distance of the step from the transom. Moreover, it was found that the proportionality of the longitudinal distance of the step from the transom to the step height has a remarkable effect on the hydrodynamic efficiency of the step in stepped planing craft.

3

Numerical study of step forward swept angle effects on the hydrodynamic performance of a planing hull

Nourghasemi H., Bakhtiari M., Ghassemi H.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2017

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nr 51 (123)

35--42

EN

One of the most effective methods to diminish the drag of a planing craft is to use a step at the bottom of the hull. A stepped hull causes a reduction of the wetted area and, as a result, a decrease in the drag. The step may be designed as a straight line through the entire width of the hull or may be V-shaped with a forward or backward swept angle. In this paper, the effects of the step forward swept angle on the hydrodynamic performance of a hard chine planing vessel are investigated by finite volume method (FVM). Reynolds-Averaged Navier Stokes (RANS) equations with a standard k-ε turbulence model coupled with volume of fluid (VOF) equations are solved in order to simulate a transient turbulent free surface flow around the hull with the help of Ansys CFX software. In order to predict hull motions, equations of rigid body motions for two degrees of freedom (2-DOF) are coupled with fluid flow governing equations. To validate the presented numerical model, first the numerical results are compared with available experimental data, and then the obtained numerical results of the drag, dynamic trim, sinkage, wetted keel length, wetted chine length, pressure distribution on the hull, wetted surface and wake profile at different Froude numbers and step angles are presented and discussed.

4

Experimental evaluation of forward speed effect on maneuvering hydrodynamic derivatives of a planing hull

Kazerooni M. F., Seif M. S.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2017

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nr 49 (121)

40--53

EN

The calculation of unknown hydrodynamic derivatives of the equations of motion is the first step to estimate ship maneuverability and dynamic stability. These derivatives can be obtained theoretically, experimentally and numerically. Despite the development of the oblique towing model test to measure the hydrodynamic derivatives of displacement ships, limited experimental results are available for hydrodynamic derivatives of high speed crafts and speed dependency of the hydrodynamic derivatives is not understood well. In this paper a systematic series of model tests is described to determine the effect of forward speed on hydrodynamic derivatives of a monohull planing craft and the variations of the hydrodynamic derivatives by forward speed are derived. According to the results, hydrodynamic derivatives of planing hull are dramatically changed by variations of forward speed. Moreover, it is not possible to introduce a constant hydrodynamic derivative in the all the ranges of drift angle. Thus, the method of known constant hydrodynamic derivatives is not applicable to the simulation of planing craft maneuvering and variable hydrodynamic derivatives should be applied.

5

A hydrodynamic methodology and CFD analysis for performance prediction of stepped planing hulls

Ghassemi H., Kamarlouei M., Veysi S. T. G.

Polish Maritime Research

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2015

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nr 2

23--31

EN

Nowadays all efforts in planing hull research are focused on resistance reduction for achieving the highest speed in fast planing crafts. Furthermore, many fruitful research projects have been carried out on marine coatings, planning equipment, and optimization of propeller and hull form, which revolutionized industry of high - speed crafts and made them an efficient survival vehicle in coastal areas and rivers. In this paper the hydrodynamic performance of planing hulls are investigated by means of a modified Savitsky model for both non-stepped and stepped bodies. Meanwhile, in order to meet this goal reasonably, effective geometrical parameters of planing hull are investigated and then operational hydrodynamic characteristics of the craft are predicted by using a computational program. Finally, the calculation results are verified by means of a CFD- analysis model.