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In order to reveal the complete topology of unsteady coherent flow structures the instantaneous measurement of the 3D velocity field is being of the great interest in fluid mechanic. Several different methods were proposed to achieve a 3D version of the technique (scanning light sheet, holography, 3D PTV). We aimed in our study to develop a 3D technique than enables to obtain the 3D kinematic field of an impinging jet by using 2D measurements. In this study and in order to validate the proposed technique [1], the tomographic particle image velocimetry technique has been applied to time resolved PIV recordings. The first step before the validation was to study the vortex shedding phenomena between the jet exit and the slotted plate. The experiments were performed at a Re = 4458 with an initial velocity U0=7m/s using three cameras Phantom V711 and a Nd: YLF LDY 300 Litron laser. In the present study, we analyzed the coherent structures organization by a 3D-velocity visualization. Both mean and fluctuating part of velocity were analyzed for several positions in z. The results has shown that a couple of vortex rolls are created downstream the flow at y/H=2.

Impinging jets which interact with sharp edges like slotted plates can be found in ventilation and air conditioning systems. In some cases, these configurations can be a source of desirable sounds like in musical instruments. However, they can be a source of noise in other applications such as air conditioning systems. Thus in order to reduce the noise produced from such configurations a more profound study of the flow dynamics should be implemented. All previous studies of impinging jets on a slotted plate were done in 2D. Accordingly, the objective of the present study was to reconstruct the studied volume by combining stereoscopic PIV measurements and the POD method. Consequently, an experimental set up has been developed and implemented in order to generate a flow that hits a slotted plate. On the other side, the PIV technique was used in order to study the dynamics of such a flow. The kinematic fields of twenty two parallel planes are measured by means of stereoscopic PIV. Afterwards, the analysis of the most energetic modes was obtained by the application of the snapshot POD on the kinematic fields obtained by POD. The results showed that the reconstruction of each of the planes needed only three first three modes. The reconstructed volume is obtained by an interpolation of the reconstructed planes which were phased by a trigger signal. The analysis of the vortex structures were done by the application of several vortex detection criteria.

Harmonics are one of the major quality concerns. The increasing use of power semiconductor devices (i.e., nonlinear loads) is keeping harmonic distortion in electrical installations on the rise. Harmonics generally cause the distortions of voltage and current waveforms, which result in many harmful effects on both utilities and customers. A parallel active harmonic conditioner can be used to compensate current harmonics demanded by nonlinear devices so that the supply current remains quasi-sinusoidal. In principle, this conditioner consists of a voltage-source inverter connected in parallel between the utility system and the customer. The control of such an inverter is an essential step in harmonic compensation. Most of the existing control methods are formulated as a classical tracking problem that requires reference generation. In a previous work, a parallel active harmonic conditioner was formulated as a perturbation rejection problem rather than a reference tracking one, and a linear state feedback [H.sub.[infinity]] controller was synthesized in order to drive the inverter. The objective of this paper is to reduce the number of measured outputs, and therefore to design a linear output feedback [H.sub.[infinity]] controller by noniterative means. The robustness of such a controller with respect to the system impedance uncertainties is investigated. Moreover, the validity of the synthesized output feedback control law is revealed through both simulation and experimental results. Index Terms--Harmonics, output feedback control, perturbation rejection problem, power quality, shunt active filter.