Numerical Calculation Of The Hydrodynamic Forecs On A Ship Travelling Along A Sloping Riverbed

Ship hydrodynamic performance can be divided into three categories,namely the ship speedability, seakeeping and maneuverability. Especially,the maneuverability is particularly important for the ship navigation safety.For a long time, marine accidents such as ship collision and groundingoccurred frequently due to the poor ship maneuverability. Especially inrecent decades, with the development of modern shipping industry, on onehand, ships are becoming large-scale; and on the other hand, they travel inmore kinds of restricted waters, which make the ship maneuvering moredifficult, and induce larger risk of marine accidents. In last decade, withthe promulgation and implementation of the International MaritimeOrganization (IMO)“Standards for Ship Maneuverability”, and rising ofthe people’s safety awareness, ship maneuverability gradually attractspeople’s attention and becomes more and more emphasized.When a ship travels in restricted waters, its hydrodynamicperformance is very different from that in infinite waters. Especially in therestricted waterways, due to the restricted depth and bank, the ship will beinfluenced by the shallow water effect and bank effect, which cause moreserious maneuverability problems. The IMO’s “Standards for ShipManeuverability” sets a well-documented regulation which requires thatthe prediction and evaluation of ship maneuverability must be conducted inthe early stage of ship design. However, this regulation only aims at thecase of the infinite waters. Therefore, it is necessary to study the shipmaneuverability in restricted waters, in order to assure the navigationsafety of ships travelling in restricted waters.Since the end of last century, computer technology and computationalmethods have achieved great progress, which establishes a solidfoundation for computational fluid dynamics (CFD) method applied to theship hydrodynamics. After years of development, making use of CFD method can attain reasonable results for simulation of ship viscous flowfield and calculation of ship hydrodynamic forces in the stage of shipdesign. As a result, CFD method gradually becomes a reliable andeffective tool for the research on ship maneuverability. In the past, captivemodel test was adopted to investigate ship maneuverability. This method istime-consuming, costly, and of low adaptability. In the contrary, CFDmethod not only overcomes the shortcomings of the model test method,but also allows more deeply analysis of the ship viscous flow field andprovides guidance on optimization of the ship hull form. CFD method canbe combined with model test method, to verify the numerical prediction,thus to obtain more accurate numerical results.In this thesis, a large container ship KCS model is used for the studyon the hydrodynamic behaviors of a ship travelling in restricted waters.Based on the general-purpose commercial software FLUENT, in which thefinite volume method is used for discretization, the viscous flow fieldaround the ship hull is simulated by solving the Reynolds-averagedNavier-Stokes equations (RANS equations); and the hydrodynamic forceson the ship are calculated to achieve the numerical prediction of the shiphydrodynamics.This thesis has mainly studied three cases of ships navigating inrestricted waters:(1) The ship model moving straight ahead in restrictedwaters with a sloping bottom and a vertical bank on one side;(2) The shipmodel moving straight ahead in restricted waters with a sloping bank;(3)The ship model moving obliquely in restricted waters with a sloping bank.To validate the effectiveness of the CFD method, the calculation results ofship hydrodynamic forces for the three cases mentioned above arecompared with the calculated results by the empirical formulas ortheoretical method. Besides, the influences of the ship-bank distance, angleof the sloping bottom or bank, water depth, ship speed and drift angle onthe ship hydrodynamics are also analyzed.The CFD method applied in this thesis can be used to some extent tomake prediction and assessment of the ship hydrodynamic performance inrestricted waters. The results obtained can provide a reference tomaneuvering and control of a ship navigating in restricted waters, so thatto ensure a safe ship navigation.