To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

Wind tunnel experiments of a newly developed two-bladed Savonius-style wind turbine

Vortex-induced motions are generally known as destructive phenomena for engineering structures. Nevertheless, they have a positive effect which is their great potential to extract renewable energy from the fluid flow. The phenomenology of vortex-induced motions has been studied and several energy harvesting technologies based on these motions have been reported, separately through literature. However, a comprehensive study that bonds together the phenomenology and the energy extraction technologies does not exist yet. Now that this area has become well established, classification of the relevant phenomena and technologies has become necessary as well. The present paper has two main objectives; The first objective is to classify the whole vortex-induced motion phenomena into several groups which include Flutter, Transverse and Torsional Galloping, Buffeting, Vortex-Induced Vibration (VIV), and Fluttering-Autorotation. The second objective is to review the literature, with the aim of classifying different technologies of renewable energy harvesting based on vortex-induced motion. Also, the performance characteristics and economical costs of these technologies are benchmarked.

Renewable energy harvesting by vortex-induced motions: Review and benchmarking of technologies

Pure and Al doped ZnO thin films were fabricated on glass substrates by sol-gel method. It is found that all the thin films have a preferential c-axis orientation. With increase of Al doping, the peak position of the (002) plane is shifted to the low 2θ value. A minimum resistivity of 6.2×10~(-4) Ω·cm is obtained for the film doped with 1.5 % Al. However, the resistivity increases with increasing Al concentration. The bandgap is found to broaden with increasing dopant concentration, and it is found that doping with Al has the effect of shifting the optical absorption to the shorter wavelength, which both cases are attributed to the Burstein-Moss shift.

Al-doping effects on structure, electrical and optical properties of c-axis-orientated ZnO:Al thin films

Effects of end plates with various shapes and sizes on helical Savonius wind turbines

Experimental investigation of helical Savonius rotor with a twist of 180

Numerical simulation and experimental validation of the turbulent flow around a small incurved Savonius wind rotor

Experimental and numerical study of the impact of the collector roof inclination on the performance of a solar chimney power plant

Performance study of a Helical Savonius hydrokinetic turbine with a new deflector system design

A specific computational fluid dynamics (CFD) code is developed to predict the turbulent flow field in a stirred tank equipped with the pitched blade turbines (PBT) and to choose the most effective agitation system. The computer method permits the numerical analyses of turbines with complex geometries. After defining the list of nodes belonging to the interface separating the turbine shape and the flow domain, the meshes in the flow domain are automatically generated on a finite volume discretization. The three-dimensional flow of a fluid is numerically analyzed using the Navier–Stokes equations in conjunction with the standard k – e turbulence model. The effects of inclined angle on the local and global flow characteristics have been particularly determined. To verify our computer simulations, the power numbers were measured and compared with computer results. Also, the flow patterns have been compared with the ones found by other experimental results. These matching results indicate the validity of our computer method.

Zied Driss

Papers

Experimental investigation of helical Savonius rotor with a twist of 180

Numerical simulation and experimental validation of the turbulent flow around a small incurved Savonius wind rotor

Experimental and numerical study of the impact of the collector roof inclination on the performance of a solar chimney power plant

Performance study of a Helical Savonius hydrokinetic turbine with a new deflector system design

Computational studies of the pitched blade turbines design effect on the stirred tank flow characteristics