Investigations of air cushion effect on the slamming load acting on trimaran cross deck during water entry
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Slamming
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Using FLUENT software to calculate the pressure of the different section of ship hull in waves.And then application the boundary element software to calculate ship hull relative to the vertical velocity of wave surface under appointed sea situation,and established enter water model of ship hull section,to calculate distribution of the pressure and the vertical force.The finally results could be as experiential formulas ensure local pressure coefficient in future project design.
Slamming
Pressure coefficient
Impact pressure
Ship motions
Naval architecture
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Choosing the right hull shape is important in designing a ship, for example, a U-section or V-section of the hull. The hull shape will affect various aspects, such as design, resistance, seakeeping, structure and production. The ship hull must be properly designed so that it can operate according to the ship’s mission. From the seakeeping aspect of the ship's motion at sea, the difference in the hull shape will result in different motions and dynamic effects such as the slamming phenomenon. Based on the difference in the hull shape cases, this study analyzed the difference in the probability of slamming between the U and V hulls. Both hulls were made based on Formdata and almost all parameters were made the same. Parameters that cannot be forced to be the same are WSA (wetted surface area), (coefficient of waterplane area), and (distance of keel to buoyancy), where those parameters determine the difference in the results. The calculation of RAO (operator amplitude response) was obtained using the strip theory method which assisted by Maxsurf Motion software. The results became the input for the calculation of the slamming probability. The study results show that the U hull has a higher probability of slamming occurrence than that of the V hull, with the difference in values ranging from 20% to 35%. Therefore, the U hull will get more frequent slamming loads, so it has the potential to have a higher structural failure (fatigue) than that of the V hull.
Slamming
Seakeeping
Ship motions
Keel
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For wave piercing catamarans, the centre bow length and tunnel clearance are important design factors for slamming, passenger comfort and deck diving. This experimental study determined the influence of centre bow (CB) and wet-deck geometry on their motions and loads at reduced speed using five configurations. A 2.5 m hydroelastic segmented catamaran model was tested in regular head seas in wave heights equivalent to 2.7 m, 4.0 m and 5.4 m at full scale. Higher wet-decks had higher vertical accelerations but reduced slamming loads. The greatest peak vertical CB loads ranged between 18–105% of the total hull weight. Regression models were obtained for the vertical loads and bending moments. A reduction of speed from 38 knots to 20 knots reduces the maximum slam loads by approximately 30% in regular waves. Considering both low and high speeds, the Short CB was found to be a consistent design for slamming reduction.
Slamming
Ship motions
Bow wave
Scale model
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Slamming against the wet deck of a multihull vessel in head sea waves is studied analytically and numerically. The theoretical slamming model is a two-dimensional, asymptotic method valid for small local angles between the undisturbed water surface and the wet deck in the impact region. The disturbance of the water surface as well as the local hydroelastic effects in the slamming area are accounted for. The elastic deflections of the wet deck are expressed in terms of "dry" normal modes. The structural formulation accounts for the shear deformations and the rotatory inertia effects in the wet deck. The findings show that the slamming loads on the wet deck and the resulting elastic stresses in the wet deck are strongly influenced by the elasticity of the wet deck structure.
Slamming
Hydroelasticity
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Among all kinds of loads that floating and fixed marine constructions experience, water wave slamming can be considered as one of the most critical. To prevent naval constructions from failing due to slamming impact, slamming loads should be carefully investigated. Besides analytical and numerical calculations, experimental data is of crucial importance. Slamming loads can be measured by performing pressure measurements on the surface of the object during impact. Previous publications showed that precise and correct measurements are very difficult to perform, especially for slamming events with small deadrise angles. Large scatter mostly characterizes these measurements. This research focuses on improving the accuracy and reproducibility of the pressure recordings. Therefore, slamming drop tests are performed on a rigid cylindrical body. Most attention is paid to the bottom of the cylinder where the deadrise angle is 0°.
Slamming
Impact pressure
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In this paper the results of the destructive experiment of a 1/5 scale ship hull model is reported. The model was designed to be as similar as possible to the midship part of the destroyer escort and subjected to pure bending moment.The general buckling strength of the upper deck was mainly studied considering the effects of under-deck structures.A loading device was specially constructed for this experiment.Buckling of the upper deck occured over two frame spaces and its load agreed with a theoretical estimation.
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An explicit finite element method which is combined with the Arbitrary Lagrangian-Eulerian (ALE) algorithm is applied to forecast slamming loads during the structure entries into the water. By adjusting the contact parameter, the result of slamming force is improved and this result is compared with the corresponding experimental values to verify the numerical prediction method of slamming loads. By simulating the wedge into the water at a constant speed and evenly variable speed, the effect of the impact velocity on local slamming pressure and global slamming force is studied.
Slamming
Wedge (geometry)
Impact pressure
Impact
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Slamming is harmful to ships and the status of bow slamming in heeling is rarely studied. Because yacht heeling will inevitably occur when navigating in storm,it is necessary to be studied the effect of bow slamming. The slamming performance on the bow of a 40 m steel yacht was studied using numerical simulation method. Based on the validation of ship analysis model established to simulate the slamming process in two-dimensional,the influences of slamming pressure with different speeds and angles on yacht bow have been analyzed and exhibited by employing LS / DYNA finite element method. The comparison results can be a reference to predict the time- varying dynamics of bow slamming pressure,which is of great importance for the structure design and operating performance of yacht.
Slamming
Bow tie
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Ships hydroelasticity theory is employed to predict the wave induced dynamic response of a hull. There are propeller forces on the stern and slamming forces on the bow which must also be considered. In this paper, the Hamiltonian method is proposed to solve this problem. Results are presented for a 35 000 ton ship under wave and propeller excitation.
Slamming
Stern
Hydroelasticity
Propulsor
Response amplitude operator
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This article describes a series of model tests conducted to examine extreme wave events associated with tropical cyclonic conditions and their impacts on an offshore deck structure. Extreme waves of a representative cyclonic sea state were examined in a towing tank within long-crested irregular wave trains. Experimental results presented include global forces and localised slamming pressures acting on a rigidly mounted box-shaped deck, which represents a simplified topside structure of a tension leg platform. The effect of static set-down on the still-water air gap was investigated by applying an equivalent reduction for the deck clearance. It was found that a small reduction of 20 mm (2.5 m full scale) in the original deck clearance can lead to a doubling of the magnitude of the horizontal force and the vertical upward-directed force components, as well as significantly increased slamming pressures in many locations on the deck underside.
Slamming
Towing
Ship motions
Impact pressure
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Citations (18)