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    Wyświetlanie 1-9 z 9
    Tytuł:
    The hydrodynamic resistance of stepped planing hulls under different geometrical and physical conditions
    Autorzy:
    Najafi, Amin
    Nowruzi, Hashem
    Salari, Mahmoud
    Kazemi, Hamid
    Powiązania:
    https://bibliotekanauki.pl/articles/135246.pdf
    Data publikacji:
    2019
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    towing tank test
    planing hull
    transverse step
    hydrodynamic resistance
    Fridsma
    height of the step
    Opis:
    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.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2019, 58 (130); 24-31
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of the stern wedge length and height on the drag and trim of a chine-planing hull
    Autorzy:
    Ghassemi, Mohammad A.
    Ghadimi, Parviz
    Sajedi, Sayyed Mahdi
    Powiązania:
    https://bibliotekanauki.pl/articles/2033606.pdf
    Data publikacji:
    2021
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    chine-planing hull
    stern wedge
    wedge width and height
    drag
    trim
    pressure distribution
    Opis:
    This paper examines the effect of the stern wedge length and height on the drag and trim of a chine-planing hull in calm water. To this end, fluid flow was simulated by Star-CCM+ software by applying an overset mesh and k-ε turbulent model. The finite volume method was used to discretize the fluid domain, and the fluid volume was utilized to capture the generated free surface. The considered model is a prismatic planing hull with a deadrise angle of 24°, a mass of 86 kg, a length (L) of 2.64 m, and a beam (B) of 0.55 m. For validation, the numerical results of drag and trim were compared against experimental data, which displayed good compliance. Subsequently, the hydrodynamic performance of the planing hull was investigated, and the wedge effect was assessed. The stern wedge was located at the bottom and near the aft perpendicular to the hull to facilitate a moderate distribution. Various wedge lengths of 0.2B, 0.5B, and B at two different heights of 5 mm and 10 mm were examined to assess the hydrodynamic performance of the hull at various speeds. The trim angle, resistance, water surface elevation, porpoising, roster tail, and the stern and bow were computed and analyzed. Based on the numerical results, it was concluded that when the wedge length increased, the drag and trim were reduced. It was also concluded that the best wedge for a vessel with desirable wake generation is one with a length of 0.2B and a height of 5 mm.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2021, 67 (139); 39-52
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Test studies of the resistance and seakeeping performance of a trimaran planing hull
    Autorzy:
    Ma, W.
    Sun, H.
    Zou, J.
    Zhuang, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/259495.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    trimaran planing hull
    appendix
    resistance
    seakeeping
    model test
    Opis:
    Towing tank tests in calm water were performed on a trimaran planing hull to verify its navigational properties with different displacements and centres of gravity, as well as to assess the effects of air jets and bilge keels on the hull’s planing capabilities, and to increase the longitudinal stability of the hull. Hydrostatic roll tests, zero speed tests, and sea trials in the presence of regular waves were conducted to investigate the hull’s seakeeping ability. The test results indicate that the influence of the location of the centre of gravity on the hull resistance is similar to that of a normal trimaran planing hull; namely, moving the centre of gravity backward will reduce the resistance but lower the stability. Bilge keels improve the longitudinal stability but slightly affect the resistance, and the presence of air jets in the hull’s channels decreases the trim angle and increases heaving but has little effect on the resistance. Frequent small-angle rolling occurs in waves. The heaving and pitching motions peak at the encounter frequency of , and the peaks increase with velocity and move towards greater encounter frequencies. When the encounter frequency exceeds, the hull motion decreases, which leads to changes in the navigation speed and frequency.
    Źródło:
    Polish Maritime Research; 2015, 1; 22-27
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Test research on the resistance performance of high-speed trimaran planing hull
    Autorzy:
    Ma, W.
    Sun, H.
    Zou, J.
    Yang, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/259708.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    trimaran planing hull
    side hulls
    high speed
    step
    resistance
    model test
    Opis:
    In order to identify high-speed navigation ability of trimaran planing hull, as well as investigate the characteristics of its resistance and hull form, ship model tests were conducted to measure resistance, trim and heaving under different displacements and gravity centre locations. The test results were then used to study the influence of spray strips on resistance and sea-keeping qualities. Moreover, different planning surfaces were compared in the model tests which helped to look into influence of steps on hull resistance and its moving position. Also, the resistance features of monohull and trimaran planing hulls, both with and without steps, were compared to each other. From the tests it can be concluded that: the two auxiliary side hulls increase aerodynamic lift at high-speed motion, which improves the hydrodynamic performance; the trimaran planing hull has also excellent longitudinal stability and low wave-making action; when Fr∇> 8, its motion is still stable and two distinct resistance peaks and two changes of sailing state (the second change is smaller) appear; spray strips are favourable for sea-keeping qualities at high speed. The change trends before the second resistance peak as to the resistance and sailing behaviour of trimaran planing hull without steps are the same as for monohull planing hull without steps. but when steps in both hulls exist the change trends are different; more specifically: trimaran planing hull with steps has only one resistance peak and its resistance increases along with its speed increasing, and the resistance is improved at the increasing speed as the number of steps increases.
    Źródło:
    Polish Maritime Research; 2013, 4; 45-51
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical study of step forward swept angle effects on the hydrodynamic performance of a planing hull
    Autorzy:
    Nourghasemi, H.
    Bakhtiari, M.
    Ghassemi, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/135251.pdf
    Data publikacji:
    2017
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    planing hull
    step forward swept angle
    hydrodynamic performance
    drag
    wake profile
    RANS
    Opis:
    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.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2017, 51 (123); 35-42
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental evaluation of forward speed effect on maneuvering hydrodynamic derivatives of a planing hull
    Autorzy:
    Kazerooni, M. F.
    Seif, M. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/135366.pdf
    Data publikacji:
    2017
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    planing hull
    maneuvering
    model test
    derivative
    hydrodynamic
    Opis:
    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.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2017, 49 (121); 40-53
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic motions of the cabin mounted on the mono-hull planing boat using suspension system in waves
    Autorzy:
    Bahrami, Hassan
    Ghassemi, Hassan
    Powiązania:
    https://bibliotekanauki.pl/articles/32891487.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    planing hull
    Fridsma model
    cabin
    suspension system
    dynamic motions
    wave effect
    Opis:
    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.
    Źródło:
    Polish Maritime Research; 2022, 1; 13-25
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An experimental study of interceptor’s effectiveness on hydrodynamic performance of high-speed planing crafts
    Autorzy:
    Karimi, M. H.
    Seif, M. S.
    Abbaspoor, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/258886.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    interceptors
    drag reduction
    hydrodynamic quality
    planing catamaran
    mono-hull
    Opis:
    Trim control mechanisms such as interceptors and trim flaps have been widely used in recent years in highspeed crafts for ride and trim control. In spite of their extensive application, a few studies investigating the impact of interceptors on planing craft performance, have been published. In the present study, the impact of interceptors on planing crafts hydrodynamic quality is investigated through application of an experimental method. Two scaled-down models of high-speed planing mono-hull and catamaran are tested with and without interceptors in calm water at different heights of the interceptors to investigate the effect of interceptors on drag reduction of the models. The first one is a scaled-down model of 11 m planning mono-hull boat and the test was conducted at the towing tank of Sharif University of Technology, Iran. The second one is a scaled-down model of 18 m planing catamaran boat and the test was conducted at the towing tank of Krylov Shipbuilding Research Institute (KSRI), Russia. The experimental results show a remarkable drag reduction of up to 15% for mono-hull model and up to 12% for catamaran model over the wide speed range of the models.
    Źródło:
    Polish Maritime Research; 2013, 2; 21-29
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A hydrodynamic methodology and CFD analysis for performance prediction of stepped planing hulls
    Autorzy:
    Ghassemi, H.
    Kamarlouei, M.
    Veysi, S. T. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/260311.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    planing hull
    Hydrodynamic performance
    CFD analyzed
    Opis:
    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.
    Źródło:
    Polish Maritime Research; 2015, 2; 23-31
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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