Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

Abstract

This paper describes a set of turbulence measurements at sea in the area of high flow distortion in the nearwake and recirculation zone behind a ship's superstructure that is similar in geometry to a helicopter hangar/ flight deck arrangement found on many modern U.S. Navy ships. The instrumented ship is a 32-m-long training vessel operated by the United States Naval Academy that has been modified by adding a representative flight deck and hangar structure. The flight deck is instrumented with up to seven sonic anemometers/ thermometers that are used to obtain simultaneous velocity measurements at various spatial locations on the flight deck, and one sonic anemometer at bow mast is used to characterize inflow atmospheric boundary conditions. Data characterizing wind over the deck at an incoming angle of 08 (head winds) and wind speeds from 2 to 10 m s 21 obtained in the Chesapeake Bay are presented and discussed. Turbulent statistics of inflow conditions are analyzed using the Kaimal universal turbulence spectral model for the atmospheric surface layer and show that for the present dataset this approach eliminates the need to account for platform motion in computing variances and covariances. Conditional sampling of mean flow and turbulence statistics at the flight deck indicate no statistically significant variations between unstable, stable, and neutral atmospheric inflow conditions, and the results agree with the published data for flows over the backward-facing step geometries.

Propagation characteristics of ship waves in navigation tunnel and its influence on continuous navigation safety of ship

“…. 目前, 国内外很多学者通过现场调查 [8,9] 、物理实 验 [10,11] 以及数值模拟 [12,13] 等方法研究了船行波的物理 特性 [14] 、对船舶自身稳定性 [15] 以及对周围护岸 [9] 、水 底 [16] 和周围设施 [17] 的影响. 众所周知, 船行波包括首波 系、尾波系、散波和横波等不同的分类形式, 通常随 弗劳德数Fr的不同呈现不同的表现形式 [18] .…”