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1.
In this paper the probability of green water occurrence is investigated by taking into account the threshold of the vertical relative motion exceeding the freeboard. The number of wetting of the unit/vessel is predicted using probabilistic method. This paper compares the significant load, due to shipping of green water with the works of other researchers, and the loads are found to be close with the results presented in this paper. There is no direct relation between the velocities in the waves and the water velocity over the deck. The water velocities around the bow are heavily distributed by the presence of the bow. This scenario makes the flow very complex for schematic modelling. 相似文献
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Squat effects on high speed craft in restricted waterways 总被引：1，自引：0，他引：1
The vessels considered here for the squat studies are a bulk carrier and an High Speed Craft (HSC). The bulk carrier of full form (CB=0.81) is used for validation purpose and subsequently the numerical computations are performed for a High Speed Craft with fine hull form of CB=0.467. A high speed ferry, with LCB and LCF quite aft of midship is considered for squat study. For a vessel speed of above 6.0 knots and for a waterway width greater than the vessel length there appears to be a sudden increase in sinkage at the stern accompanied by a large value of bow emergence. It could be seen that the speed of the vessel has a much greater influence on the sinkage and trim of the vessel than the waterway restrictions. 相似文献
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Modification of ship hydrodynamic interaction forces and moment by underwater ship geometry 总被引：1，自引：0，他引：1
The hydrodynamic interaction forces/moments acting on a moored ship due to the passage of another ship in its proximity is researched by considering the influence of ship form against the idealized approach of the use of parabolic sectional area distribution. Comparisons with experimental results show that the interaction effects are predicted better by inclusion of ship's form. 相似文献
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SK Pathan VK Shukla RG Patel BR Patel KS Mehta 《Journal of the Indian Society of Remote Sensing》1991,19(2):95-112
Proper urban planning and effective implementation requires reliable urban land use statistics. In this context, satellite remote sensing data has been studied using both visual and digital techniques. A portable eight-band radiometer has been used to collect spectral signatures of surface features present in Ahmedabad city and its environs. Using these signatures a suitable approach employing visual and digital techniques has been developed for urban land use/sprawl mapping. Urban land-use maps of Ahmedabad city and its environs were prepared on 1:25,000 scale and for Ahmedabad Urban Development Authority Area on 1:50,000 scale using this methodology. It has been found that edge-enhancement techniques are useful to enhance the contrast among different urban land uses. Classification techniques such as MXL and Bayes classifiers are not successful in discriminating urban land uses. Tonal characteristics alongwith other elements of interpretation are required to classify urban land uses such as residential, industrial etc. Spatial distribution of various urban and uses and the space devoted to each urban land use has been brought out. 相似文献
6.
The research into hydrodynamic loading on ocean structures has concentrated mostly on circular cross-section members and relatively limited work has been carried out on wave loading on other cross-sections such as rectangular sections. These find applications in many offshore structures as columns and pontoons in semi-submersibles and tension-leg platforms. The present investigation demonstrates the behaviour of rectangular cylinders subject to wave loading and also supplies the hydrodynamic coefficients for the design of these sections.This paper presents the results of wave forces acting on a surface piercing truncated rectangular cylinder set vertically in a towing tank. The experiments are carried out in a water depth of 2.2 m with regular and random waves for low Keulegan–Carpenter number up to 6. The rectangular cylinder is of 2 m length, 0.2 m breadth and 0.4 m width with a submergence depth of 1.45 m from still water level. Based on Morison equation, the relationship between inertia and drag coefficients are evaluated and are presented as a function of KC number for various values of frequency parameter β, for two aspect ratios of cylinders, equals to 1/2 and 2/1. Drag and inertia coefficients obtained through regular wave tests are used for the random wave analysis to compute the in-line force spectrum.The results of the experiments show the drag and inertia coefficients are strongly affected by the variation in the aspect ratios of the cylinder. The drag coefficients decreases and inertia coefficients increases with increase in Keulegan–Carpenter number up to the range of KC number tested. The random wave results show a good correlation between measured and computed force spectrums. The transverse forces in both regular and random waves are found to be small compared to in-line forces. 相似文献
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Motions and slamming impact on catamaran 总被引：1，自引：0，他引：1
Prediction of craft motions and the dynamic loads acting on a catamaran hull are of great importance to the designer. This paper presents the motions of a Vosper International catamaran in head seas with and without forward speed. Two approaches are used—strip theory and the 3D pulsating source method. A method to predict slamming loads acting on this catamaran section using Computational Fluid Dynamics is presented. The loads acting on catamaran hulls and the cross structure are illustrated. 相似文献
8.
To understand the nature of land degradation and factors responsible for it, investigations were carried out in Etah district with an area of 4.45 lakh hectares. For identification of soil/land degradation problems, multidate Landsat, TM spectral bands and FCC were used. It is observed that salt-affected soils are sharply depicted by light and dark gray mixed tone on band 3, while they are not clear on band 4. Flood plain and waterlogged soils are clearly observed on band 4. Band 6 (10.3 – 12.5 µm) helps in separation of broad zones of coarse and fine-textured soils, active flood plain of rivers, and eroded and gullied lands. The confusion between coarse-textured droughty soils and salt-affected areas in TM FCC (2, 3, 4) could be eliminated by use of band-6 data in combination with FCC. For delineation of problematic areas, two approaches were followed viz. (i) physiographic approach, and (ii) direct approach. In the physiographic approach landscape map associated with image characteristics was prepared. Further the image interpretation units were interpreted for land degradation hazards. With this approach physiography and soil relationship and the degradation problems vis-a-vis soil units could be established and ameliorative measures as per soil condition can be suggested. In direct approach, the problematic areas as per predetermined key were demarcated. Out of 4.45 lakh ha of the area, 1.99 lakh ha is affected by various soil degradation problems, like droughty soils, flooding hazard and salinity and alkalinity which cover 22.1%, 50.0% and 27.9%, respectively. To study the distribution of a salt-affected lands, major physiographic boundaries were superimposed over the land degradation map prepared by direct approach. It is observed that 81.5% of the salt-affected areas lie in the old alluvial plain while 18.5% is in recent flood plain. 相似文献
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A three-dimensional Lump-Mass formulation of a catenary riser, capable of handling irregular seabed interaction, with bending and torsional stiffness is presented in this paper. This formulation uses only three degrees of translational freedom and one independent torque variable for each computational node. The generality of the present formulation permits static and dynamic analyses of a wide range of offshore-related slender structure systems such as mooring cables, rigid and flexible risers as well as submarine pipelines. Four sets of results are presented for (i) a hanging catenary, (ii) as (i) but subjected to end torsion, (iii) a wire, chain and spring buoy mooring and (iv) a steel catenary riser on an irregular seabed. 相似文献
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A semi-analytical quasi-static formulation based on the catenary approach capable of solving three-dimensional partially grounded and fully suspended multi-leg mooring-system problems is presented in this paper. The advantage of the present formulation is that only a compact governing vector equation, derived in terms of grounded cable length and anchor tension vector, need to be solved for each mooring cable to determine its grounded and suspended body response, and only a small number of discrete segments are needed to predict its behaviour accurately due to its inherent slope continuity. In addition, it is capable of handling arbitrarily inclined seabed interaction effects, varying cross-sectional and material properties as well as external attachment objects. The generality of the present formulation allows quick parametric analysis of different forms of multi-leg mooring system configurations as well as different types of flexible riser systems to be carried out. 相似文献