Jacopo Serpieri

Politecnico di Torino | polito · DIMEAS - Department of Mechanical and Aerospace

A novel concept for actively isolating neighbouring electrodes of multi-electrodes plasma actuators for flow control is presented. For these actuators, such as the phased-array actuators (e.g. Corke & Matlis 2000) or the oscillating-wall ones (e.g. Choi et al. 2011), at different time instants, different sets of electrodes are operated; meanwhile t...

Hot-wire measurements of the streamwise velocity are conducted in the large-scale pipe-flow facility CICLoPE in the friction Reynolds number range of 7800⩽Reτ<40000. Measurements are performed both with a rake of five synchronised probes arranged at different radial locations, and through a radial scan with a single wire traversing the whole pipe r...

The present work describes an experimental investigation that applies stereo particle image velocimetry in a cross-plane of a turbulent channel flow that is additionally perturbed by spanwise oscillatory body forces, induced by a plasma actuator and designed to mimic the effect of spanwise wall oscillations. The experiment is aimed at retrieving th...

The present work experimentally investigates two forcing strategies toward controlling stationary crossflow instability (CFI) induced transition manifesting on a swept wing at subsonic conditions. The effectiveness of upstream flow deformation (UFD) and the base-flow modification strategies, realized through the application of spanwise-modulated an...

Very-large-scale structures in pipe flows are characterized using an extended Proper Orthogonal Decomposition (POD)-based estimation. Synchronized non-time-resolved Particle Image Velocimetry (PIV) and time-resolved, multi-point hot-wire measurements are integrated for the estimation of turbulent structures in a pipe flow at friction Reynolds numbe...

A combined experimental and numerical approach to the analysis of the secondary stability of realistic swept-wing boundary layers is presented. Global linear stability theory is applied to experimentally measured base flows. These base flows are three-dimensional laminar boundary layers subject to spanwise distortion due to the presence of primary...

Control of laminar-to-turbulent transition on a swept-wing is achieved by base-flow modification in an experimental framework, up to a chord Reynolds number of 2.5 million. This technique is based on the control strategy used in the numerical simulation by Dörr & Kloker ( J. Phys. D: Appl. Phys. , vol. 48, 2015 b , 285205). A spanwise uniform body...

In this study, experiments are performed towards the identification and measurement of unsteady modes occurring in a transitional swept wing boundary layer. These modes are generated by the interaction between the primary stationary and travelling cross-flow instabilities or by secondary instability mechanisms of the stationary cross-flow vortices...

In the current study, selective forcing of cross-flow instability modes evolving on a 45 degrees swept wing at Re=2.17 10^6 is achieved by means of spanwise-modulated plasma actuators, positioned near the leading edge. In the perspective of laminar flow control, the followed methodology holds on the discrete roughness elements/upstream flow deforma...

An experimental investigation of primary and secondary crossflow instability developing in the boundary layer of a 45 degress swept wing at a chord Reynolds number of 2.17 10^6 is presented. Linear stability theory is applied for preliminary estimation of the flow stability while surface flow visualisation using fluorescent oil is employed to inspe...

The need to investigate the cross-flow instability resides on the fact that this is the main cause of laminar to turbulent transition for swept wing flows in free flight. In this paper the procedure to design a wind tunnel model for cross-flow instability investigation is illustrated. The steps that are presented involve the airfoil and the wall li...

Wings operating at low and moderate Reynolds number such as the ones of UAVs or the blades of small wind turbines and of compressor fans, can be the source of an aeroacoustics phenomenon called laminar boundary layer instability noise. This paper presents an investigation with time-resolved PIV and far field microphones of the dynamical flow phenom...

In this work the flow visualization of the transition pattern occurring on a swept wing in a subsonic flow is presented. This is done by means of fluorescent oil flow technique and boundary layer hot-wire scans. The experiment was performed at Reynolds number of 2:15 � 106 and at angle of attack of 􀀀3�. At these conditions, three different flows ar...

The present study investigates the mechanisms associated with tonal noise emission from a NACA 0012 aerofoil at moderate incidence (0 degrees; 1 degrees; 2 degrees and 4 degrees angle of attack) and with Reynolds numbers ranging from 100 000 to 270 000. Simultaneous time-resolved particle image velocimetry (PIV) of the aeroacoustic source region ne...

Tonal noise generated by airfoils at low to moderate Reynolds numbers has been focus of research since decades. Several explanations of the observed phenomena relate the noise spectrum to the instability of the laminar boundary layer, which has lead to the term laminar boundary layer instability noise. The particular features of boundary layer inst...