Turbulent kinetic energy (TKE) budget measurements were conducted for a symmetric turbulent planar wake flow subjected to constant zero, favorable, and adverse pressure gradients. The purpose of this study is to clarify the flow physics issues underlying the demonstrated influence of pressure gradient on wake development, and provide experimental support for turbulence modeling. To ensure the reliability of these notoriously difficult measurements, the experimental procedure was carefully designed on the basis of an uncertainty analysis. Three different approaches were applied for the estimate of the dissipation term. An approach for the determination of the pressure diffusion term together with correction of the bias error associated with the dissipation estimate is proposed and validated with the DNS results of Moser et al (J Fluid Mech (1998) 367:255–289). This paper presents the results of the turbulent kinetic energy budget measurement and discusses their implications for the development of strained turbulent wakes.

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Measurement of the turbulent kinetic energy budget of a planar wake flow in pressure gradients

A geosim analysis of ship resistance decomposition and scale effects with the aid of CFD

The main purpose of this investigation was to demonstrate a useful application of the particle image velocimetry (PIV) method to analyze the complex flow characteristics around a ship. For a sample illustration, the KRISO 3600TEU container ship model was chosen. The flow structure in the stern and near-wake region of the model has been investigated experimentally in a circulating water channel. Instantaneous velocity fields measured by the PIV velocity field measurement technique have been ensemble-averaged to give details of flow structures such as the spatial distributions of the local mean velocity, vorticity, and turbulent kinetic energy. The free-stream velocity was fixed at Uo = 0.6 m/s, and the corresponding Reynolds number based on the length between perpendiculars was about 9.0 × 105. The container ship model shows a complicated three-dimensional flow structure in the stern and near-wake regions. The PIV results clearly revealed the formation of large-scale bilge vortices in the stern region and their effect on the flow in the near-wake. The results shown here provide valuable information for hull form design and the validation of viscous ship flow codes and of turbulence models.

PIV velocity field measurements of flow around a KRISO 3600TEU container ship model

https://www.pure.ed.ac.uk/ws/files/80705096/Speranza_etal_2019OE.pdf

Modelling of hull roughness

Turbulent ship wake conservation at a long distance is one of unsolved problems at present. It is well known that wakes have a rotational structure and slowly expand with distance. Nevertheless, experimental data on their structure and properties are not sufficient. On the other hand, these experimental data show that the divergence of wakes does not change according to the law 1/5, as predicted by the theory. In our work we study the effect of helicity on the parameters of a turbulent ship wake. Taking into account the helical nature of the wake, we can clarify the difference between turbulence inside and outside of the wake on the one hand, and slow its expansion with time.

On the helical behavior of turbulence in the ship wake

Experiments have been conducted in a wind tunnel on a 10-foot-long model of a mathematical ship form to study the flow in the boundary layer and wake. The measurements were made with a five-hole pilot and a three-sensor hotwire probe, and extend from midships to 0.8 ship length downstream of the stern. The data include the pressure and mean-velocity fields, all six components of the Reynolds-stress tensor, and all ten components of the triple-product tensor. The evolution of the wake from the thick boundary layer over the stern has been documented in detail.

O. P. Sarda

Papers

Mean-flow and turbulence measurements in the boundary layer and wake of a ship double model