Experimental and Numerical Analysis of Hull Girder Vibrations and Bow Impact of a Large Ship Sailing in Waves

J. Zhejiang Univ. Sci. A

Sun

et al. 2016

Self Cite

Abstract:The traditional laboratory models for the hydroelasticity and seakeeping performance of ships are tested in calm water and in uni-directional, artificially generated waves. A new alternative to the tank model measurement methodology is to conduct experiments using large-scale models in actual sea conditions. To implement the tests, a large-scale segmented self-propelling model and testing system were designed and assembled. A buoy wave meter was adopted to record the coastal waves that the model encountered during the tests. The analysis of the results of waves in sheltered waters by the spectral method shows good agreement with ISSC spectra. To investigate the difference between this new methodology and the traditional towing tank tests, a small-scale model, whose type and configuration are the same as those of the large-scale model ship, was used and tests were conducted in a towing tank. Comparison of the two experimental results shows that there is a remarkable difference in the response characteristics between the large-scale model at sea and the small-scale model in the tank. Numerical simulations of the responses of the ship under equivalent sea states were also carried out. The influence of directional spreading functions on the results was analyzed by a numerical approach. The classical model tests under long-crested waves in the towing tank over-estimate the motion and wave load responses; however, large-scale model tests carried out at sea are more reasonable for ship design and scientific research.

Section: Model Designmentioning

confidence: 99%

“…The layout of the sensors for wave loads and motions is the same as that in the large-scale model. The propulsion equipment is also installed on the small model to achieve sailing speeds by itself Jiao et al, 2015). Photos of the two ship models are shown in Fig.…”

Section: Comparison Of the Small-scale Model Test In The Tankmentioning

confidence: 99%

Investigation of a ship’s hydroelasticity and seakeeping performance by means of large-scale segmented self-propelling model sea trials

Jia

J. Zhejiang Univ. Sci. A

Sun

et al. 2016

Self Cite

“…FP denotes fore perpendicular. The interval in each part of segments is 1 cm to satisfy the wave-induced hydroelastic vibration of the model [9,10]. And the watertight in each interval was made by using the latex, which can be also observed in Figure 2.…”

Section: Trimaran Modelmentioning

confidence: 99%

Experimental Investigation of Wave-Induced Hydroelastic Vibrations of Trimaran in Oblique Irregular Waves

Tang

et al. 2016

Shock and Vibration

Self Cite

The irregular wave condition, especially the oblique irregular wave condition, is the actual circumstances when trimaran is sailing in sea. In order to identify the characteristic of the wave-induced hydroelastic vibration in irregular waves, as well as investigate the change of vibration in different oblique irregular wave conditions, trimaran model tests were conducted to measure vibrations, wave impact, and motion under different azimuth and wave height. The vibration on main hull, side hull, and cross-desk is measured and analyzed separately to observe the influence of irregular wave in different structural parts. The longitudinal vibration, transverse vibration, and torsion are also included in the model tests measurement to investigate the relationship between these vibration deformation components and parameters of the irregular waves. The wave-induced hydroelastic vibrations and whipping effect is extracted and analyzed to find influence of whipping and springing on the total vibration. Based on the analysis, the dangerous positions and the critical waves condition is introduced to ensure that the subsequent structural strength assessment is more reliable.

“…The characteristics of hydroelastic vibrations and bowflare slamming of a small-scale model in regular waves have already been studied through laboratory tank tests, which can be found in the authors' previous work [16]. In the present work, a large-scale model, corresponding to the same prototype as that of the small-scale model, was designed and manufactured to allow for the measurement of wave-induced hydroelastic vibrations and slamming experienced in coastal waves.…”

Section: Introductionmentioning

confidence: 98%

Experimental Investigation of Wave-Induced Ship Hydroelastic Vibrations by Large-Scale Model Measurement in Coastal Waves

Jia

Sun

et al. 2016

Shock and Vibration

Self Cite

Ship hydroelastic vibration is an issue involving mutual interactions among inertial, hydrodynamic, and elastic forces. The conventional laboratory tests for wave-induced hydroelastic vibrations of ships are performed in tank conditions. An alternative approach to the conventional laboratory basin measurement, proposed in this paper, is to perform tests by large-scale model measurement in real sea waves. In order to perform this kind of novel experimental measurement, a large-scale free running model and the experiment scheme are proposed and introduced. The proposed testing methodology is quite general and applicable to a wide range of ship hydrodynamic experimental research. The testing procedure is presented by illustrating a 5-hour voyage trial of the large-scale model carried out at Huludao harbor of China in August 2015. Hammer tests were performed to identify the natural frequencies of the ship model at the beginning of the tests. Then a series of tests under different sailing conditions were carried out to investigate the vibrational characteristics of the model. As a postvoyage analysis, load, pressure, acceleration, and motion responses of the model are studied with respect to different time durations based on the measured data.