Jean-Marc Foucaut

Assessment of Different SPIV Processing Methods for an Application to Near-Wall Turbulence

An experiment has been performed in a large wind tunnel with the objectives to record 2D3C velocity fields of a fully developed turbulent boundary layer along a flat plate by means of stereoscopic PIV (SPIV) and to study the characteristics of this turbulence. The present study starts from determining the suitable method to process the database that was recorded with the stereoscopic PIV system. It suggests that the Soloff method with 3 calibration planes and integer shift is the best choice. Then, by using this method the analysis of the mean streamwise velocity, velocity fluctuations, Reynolds shear stress, spectrum, probability density function (PDF) as well as skewness and flatness, was performed and compared with values from hot-wire anemometry (HWA) and direct numerical simulation (DNS). The comparison indicates that SPIV is a well-qualified method to investigate near-wall turbulence.

Analysis and Modelling of a Fluidic Actuator

This paper deals with the fluidic actuators in the pulsed mode used in turbulent boundary layer control, in particular as vortex generator (VG) in order to delay separation. Recently the study by Kostas et al (2007) has shown the importance of the transient phase of the VG actuators. In particular, an enhancement of the vortex-generation mechanism has been observed during the transient period, that is responsible for an increase of turbulence stress levels up to 200% relatively to the non actuated case. A large dependency of the exit velocity on the physical characteristic of the feed tube has been detected. This dependency suggests that a precise quantification of the pulsed jet dynamic during the transient period is necessary. In this work the transient behavior of the fluidic actuators used by Kostas et al (2007) is analyzed and experimented. A model is developed to explain the dynamics of the flow inside the actuator. On the whole, experiments show that the role of all physical parameters is consistent with the foreseen properties. The results obtained help to separate the input dynamic of the controller from the controlled flow. Another perspective of this work is to provide a guide for the design of fluidic actuators.Copyright