RIASSUNTO
Abstract
With the enhanced ship hydrodynamic in Xicheng Canal, the shipgenerated waves are the main factor inducing turbidity in the water column and damages of the channel revetments. In this study, to clarify the characteristics of ship-generated waves in Xicheng Canal, field observations and numerical analysis were carried out. The field observations were conducted at a straight section of Xin xiagang River and the ship-generated waves model is established based on depth averaged non-linear shallow water (NLSW) equations. The water level fluctuations at different wave gauges calculated by Delft3D-FLOW model agree fairly well with the observed data. Then, the relation among maximum non-dimensional ship-generated wave height, depth Froude number and blocking coefficient is established based on the validated model.
Introduction
Xi cheng Canal is an important part of the Yangtze River delta highgrade waterway network. With the development of economy in the region along Yangtze River in Jiangsu province, China, the quantities of ships passing through Xicheng Canal is growing rapidly and the ship dimensions become larger and larger. The ship-generated waves and currents become more intense and the increased fluid velocity can easily result in sediment re-suspension (Smaoui et al, 2011). The enhanced ship hydrodynamic effects in Xi cheng Canal have led to bad results of the channel cross-section according to the Channel Survey conducted in 2012 in Jiangsu Province.
The wave system created by a ship is typically divided into primary and secondary components (Bertram, 2012). The primary wave often referred to as drawdown, originating from the pressure and velocity distributions along the moving ship hull. The secondary wave denoted as a Kelvin wake, including divergent and transverse waves. The drawdown is a major concern in restricted channels (Göransson et al, 2014) and it can lead to large water particle velocities at the riverbed. In recent years, many numerical modeling about ship-generated waves were carried out. Kazi (1998) had used Delft2D-Rivers to model ship-generated currents. Zhou et al (2013) had confirmed that Delft3D-FLOW could simulate the primary water movement induced by the moving ship. Dam et al (2008) carried out a field observation at a restricted channel which has strong river current and had simulated the propagation of ship-generated waves by solving 2-D depth-integrated Boussinesq equations. The results computed by the model agree fairly well with the observed data.