NUMERICAL PREDICTION OF THE LOCAL PRESSURE COEFFICIENT FOR SLAMMING LOADS ON SHIP HULL IN WAVES
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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.Keywords:
Slamming
Pressure coefficient
Impact pressure
Ship motions
Naval architecture
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This paper presents the forecast method of ships' inserting velocities by considering the relationship between waves and ship motions. It uses two dimension slamming empirical formula to calculate the slamming pressure.
Slamming
Impact pressure
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A review of the existing literature on the overall response of ships to bottom slamming is presented. A mathematical formulation of the vibratory bending moment due to bottom impact slamming in regular waves is then developed. The hydrodynamic problem concerning the definition of the loads is first discussed and a particular physical model is adopted for determining the hull vibratory behavior. Based on this formulation, a general computerized procedure leading to the time-history representation of the midship bending moment is developed. Finally, an illustrative example of application to a Mariner ship is described and the results are related to some available data.
Slamming
Representation
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Slamming
Ship motions
Response amplitude operator
Sea state
Gambit
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In rough seas, actual behaviours of a ship may not be estimated by the linear strip theory, because of Nonlinearities due to the hull shape, bottom slamming and bottom and/or bow-flare slamming. In case of slamming, impulsive hydrodynamic pressure occurs on the fore body surface of the ship, resulting hull vibration called whipping, by which the ship may suffer from serious structural damages and the impact pressure, depends critically on the relative velocity at re-entry. In this paper, the Time history of impact froce at each station, the longitudinal distribution of impact force at critical time, the Time history of acceleration at F.P. and the Time history of Bending moment at midship are illustrated. That is, authors analyzed Dynamic response of container ship to be subjected slamming impact force.
Slamming
Keel
Impact
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A simulation method was developed to determine the oscillations of ship sections in deep and shallow water. Ship vibrations caused by a slam wave are computed by means of a simulation method. The results indicate that hull elasticity must be taken into consideration when determining the loads caused by slams.
Response amplitude operator
Elasticity
Ship motions
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The research on the hydrodynamic pressure field of a ship is the foundation of designing a new pressure mine,developing a minesweeper and protecting the ship,which is of great military significance.A mathematical model for the ship hydrodynamic pressure field was established based on the marine hydrodynamic potential flow theory.The sources were distributed on the ship hull surface by using the Hess-Smith method.The pressure caused by the ship at the limited water depth was calculated and compared with the experimental results.The characters of the ship hydrodynamic pressure field and the effect of water depth and the ship hull shapes on the pressure field were analyzed.The comparison shows that a good agreement is achieved between the theoretical calculation results and the experimental ones.
Naval architecture
Impact pressure
Surface pressure
Foundation (evidence)
Water pressure
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We present a numerical procedure to predict impact-related wave-induced (slamming) loads on ships. The procedure was applied to predict slamming loads on two ships that feature a flared bow with a pronounced bulb, hull shapes typical of modern offshore supply vessels. The procedure used a chain of seakeeping codes. First, a linear Green function panel code computed ship responses in unit amplitude regular waves. Wave frequency and wave heading were systematically varied to cover all possible combinations likely to cause slamming. Regular design waves were selected on the basis of maximum magnitudes of relative normal velocity between ship critical areas and wave, averaged over the critical areas. Second, a nonlinear strip theory seakeeping code determined ship motions under design wave conditions, thereby accounting for the ship’s forward speed, the swell-up of water in finite amplitude waves, as well as the ship’s wake that influences the wave elevation around the ship. Third, these nonlinearly computed ship motions constituted part of the input for a Reynolds-averaged Navier-Stokes equations (RANSE) code that was used to obtain slamming loads. Favourable comparison with available model test data validated the procedure and demonstrated its capability to predict slamming loads suitable for design of ship structures.
Slamming
Seakeeping
Ship motions
Swell
Rogue wave
Response amplitude operator
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When the ship navigates in the sea, the dynamic deformation of the ship hull will be induced by the waves. The relative large deformation of the ship hull induced by the waves may affect the operation of some certain equipment. In order to keep the equipment operating normally, the influence of the ship deformation should be evaluated. The method for the calculation and analysis of the ship deformation is discussed here. The wave loads of the ship in unit regular wave amplitude are calculated based on 3-D linear potential flow theory. The sea pressure and inertial force of the ship are obtained and applied to the global finite element model of the ship. Under the quasi-static assumption, the structural deformation response in unit regular wave amplitude is calculated with the use of finite element analysis. Then, the amplitude frequency response of the relative deformation between two arbitrary positions in the hull is achieved. The history of the deformation can be obtained based on the simulation of deformation response in irregular waves or the modal superposition method. With the help of spectral analysis method, the spectrum of the relative deformation between two arbitrary positions in the hull may be obtained. The statistical analysis of ship hull deformation in the short-term sea state is realized. Considering the critical value of ship deformation, the reliability analysis method is adopted to assess the ability of hull to resist the deformation.
Sea state
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A computational procedure of predicting bottom slamming motion and loads for FPSO is presented.The approach of transition of frequency-time domain is used to determine the occurrence of slamming and the impact loads on hull-bottom for FPSO in which ship hull motions in waves are calculated by using the three-dimensional Green function method and the wave slamming pressure is determined by means of the empirical formula.The effect of the encountered phase-angle between ship hull and incident wave and of design wave period on slamming loads at bow hull-bottom is considered in computation and analysis.This procedure can be used to predict slamming loads for FPSO with the environmental conditions in operative sea area and the occurrence frequency of slamming expediently.The calculating results can be applied as input message for fatigue analysis of hull-bottom of FPSO to predict slamming loads for hull with various loading states under different angles of wave direction.
Slamming
Ship motions
Impact pressure
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This paper discusses a method to estimate slamming characteristics of a ship at an early design stage using the ship lines. The first section of the paper deals with the derivation of a regression equation which yields a coefficient necessary to estimate impact pressure for any given hull form. The second section discusses the procedure of application of the regression equation in conjunction with other computer programs to estimate frequency and severity of slamming for ship design. As an example of the application, the extreme values of impact pressure are computed at several forward stations of the Mariner as a function of ship operation time in various sea states. By assigning an allowable extreme pressure magnitude and tolerable number of slams, it is possible to estimate the limiting sea state or limiting ship speed below which safe navigation without seriously suffering from slamming is anticipated.
Slamming
Naval architecture
Limiting
Response amplitude operator
Impact pressure
Sea state
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