George Pechlivanidis

Optimum design of the entrance of a fishpond laterally to the main stream of an open channel

In this study, the optimum design of the entrance of a fishpond laterally to the main flow of an open channel was investigated numerically and experimentally. The flow characteristic measurements were realized with the PIV (particle image velocimetry) method. The mathematical simulations were based on the development of a two dimensional -mean in depthhydrodynamic model and a quasi three dimensional sediment transport model which includes processes of advection, diffusion, and settling of conservative suspended matter. The study was completed with the comparison of the final results of the mathematical models with the findings of the physical model revealing the hydrodynamic interaction and coupling between the main flow of the channel and the lateral reservoir—fishpond and leading to the optimum technical design of the system.

Turbulent Simulation of the Flow around Different Positions of Mussel Shocks

This study presents the results of laboratory experiments that were performed to simulate the positions of mussel shocks which were selected aiming at the optimization of the quality of mussels’ production in mussel farming areas. The mussel shocks were studied in natural scale. Velocity measurements were taken upstream of two successive mussel shocks and for different positions in relation to the central axis of the channel and different distances between the shocks for three different mean velocities. Based on the results of several numbers of experiments, the main conclusion of this study was that the position and the distance between the mussel shocks play a significant role to the quality of mussels’ production in mussel farming areas. This is due to the fact that the different distances between the mussel shocks influence the velocities and the eddies around them.

Inclined Open Channels: The Influence of Bed in Turbulent Characteristics of the Flow

In this paper the characteristics of turbulent flow in an open inclined channel are studied experimentally for impermeable and permeable bed. For the simulation of porous bed two different types of permeable bed with the same thickness (mathrm {h_{v}=2,cm}) and the same porosity (upvarepsilon =0.80) are used: (a) flexible vegetation with grass and (b) gravel bed. Laboratory experiments were used for the calculation of turbulent velocity profiles. The measurements were obtained using a two-dimensional (2D) Particle Image Velocimetry (PIV). The experiments were conducted in the laboratory of Hydraulics in the department of Civil Infrastructure Engineering of Alexander Technological Educational Institute of Thessaloniki, Greece. The measurements were conducted at a (12 times 10,text {cm}^{2}) region in a distance of 4 m from the channel’s entrance, where the flow is considered fully developed. The total discharge was estimated using a calibrated venture apparatus. Measurements of velocity were taken for inclined channel for four different slopes ((mathrm{S},=,2, 4, 6,text {and},8,permille )) and for three different total heights (h (=) 5, 10 and 15 cm). The experiments were conducted for (a) impermeable bed and (b) permeable bed. Results showed that the presence of porous bed in inclined open channels influence significantly the turbulent characteristics of the flow such as the variation of longitudinal turbulent intensity (mathrm {u/U}_{*}), the variation of vertical turbulent intensity (mathrm {v/U}_{*}) and the turbulent kinetic energy. The channel slope doesn’t influence the Reynolds stress. Also, the type of porous bed influences with different way the turbulent characteristics of the flow.