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Study on the Method for Calculating Ship Squat in the Restricted Channel
Abstract
Safety is essential for the great ship which are sailing in the restricted channel, by estimating the squat and the Under Keel Clearance (UKC) correctly. This paper conducted the study on the method for calculating the squat in restricted channel. While the ship is sailing in the restrictive channel, the squat is affected by ship boundary layer. In this paper, hydrodynamic theory and flat boundary layer theory were applied to put forward the approximate formula to calculate ship boundary layer. Considering the impact of ship boundary layer, the method of squat calculating was put forward. Finally, the method was verified by real ship data.
The integration of wireless access networks with optical access networks in so-called fiber-wireless (FiWi) networks has recently emerged as a promising strategy for providing flexible network services at relative high transmission rates. FiWi network research to date has mainly focused on optical access networks with the normal reach (around 20 km) of passive optical networks (PONs). We make two main contributions to the study of FiWi networking with a long-range PON with a propagation distance on the order of 100 km in this article. First, through extensive simulations, we investigate the packet delays when relatively low-rate traffic that has traversed a wireless network is mixed with conventional high-rate PON-only traffic. We consider a range of different FiWi network architectures with different dynamic bandwidth allocation (DBA) mechanisms. Second, we closely examine the grouping of the optical network units (ONUs) in the double-phase polling (DPP) DBA mechanism in long-range FiWi networks. We introduce a novel grouping by cycle length (GCL) strategy that achieves favorable packet delay performance.
The variation of squat with speed in shallow water has been shown to be important with the sinking of the ferry Herald of Free Enterprise, yet it is not easily predictable, particularly at higher speeds. The squat characteristics of a number of ship models have been analyzed and an empirical method of predicting the squat at subcritical speeds has been devised. This method has been compared with data from the model tests of the Herald of Free Enterprise and has shown good agreement.
Tests with ship models sailing in head waves at restricted water depths
of 1.875, 2.5, and 3.75 times the ship's draft are discussed. Squat and
trim of ships in still water are dealt with, and equations of motion of
ships in waves are given. Hydrodynamic coefficients of the ship and
wave-excited forces on the ship were calculated. Motions of a ship in
restricted water depth are discussed. Motion equations of a ship sailing
at restricted water depths and thrust and power measurements are
annexed.
The problem solved concerns the disturbance to a stream of shallow water due to an immersed slender body, with special application to the steady motion of ships in shallow water. Formulae valid to first order in slenderness are given for the wave resistance and vertical forces at both sub- and supercritical speeds. The vertical forces are used to predict sinkage and trim of ships and satisfactory comparisons with model experiments are made.
On the evaluation of underkeel clearances in finish waterways
- O Huuska
Fairway design with respect to ship dynamics and operational requirements
- N H Norrbin