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Papers by valerio lorenzoni

Journal of Sound and Vibration, 2012

The present study investigates an experimental methodology to determine aeroacoustic emission fro... more The present study investigates an experimental methodology to determine aeroacoustic emission from vortex-structure interaction by means of Time-resolved Particle Image Velocimetry (TR-PIV). The aeroacoustic investigation is conducted on a rod-airfoil configuration at Re ¼6000 based on the rod diameter. The time-resolved velocity field obtained from 2D PIV is employed to evaluate the instantaneous planar pressure field by spatial integration of the Navier-Stokes equations under the assumption of 2D incompressible flow. The instantaneous pressure field computed on a control surface approximating that of the physical airfoil is used as source term of Curle's aeroacoustic analogy in both a distributed and a lumped formulation to obtain the far-field acoustic prediction. The spanwise coherence function of velocity and pressure fluctuations is determined by means of additional experiments, and is applied to weight the contributions at different frequencies. Results are compared with far-field microphone measurements in terms of spectra and directivity pattern. A good agreement is observed for the tonal component corresponding to the periodic interaction of the Ká rmá n vortices with the airfoil leading edge. The contributions at higher frequencies also show an acceptable agreement when the spanwise coherence is taken into account.

Journal of the Acoustical Society of America, 2012

An experimental study of the flow inside a saxophone mouthpiece in playing conditions is carried ... more An experimental study of the flow inside a saxophone mouthpiece in playing conditions is carried out by means of particle image velocimetry at high acquisition rate. Planar velocity measurements on the midsection of a Plexiglas tenor saxophone mouthpiece are performed, respectively, in the mouthpiece baffle and in the reed channel. Sequences of velocity fields inside the mouthpiece baffle and around the reed tip are shown for one reed duty cycle. Maxima of the velocity fluctuations are observed at the upper surface of the mouthpiece at a distance between five and ten reed apertures from the tip. The proper orthogonal decomposition analysis reveals that almost 50% of the kinetic energy in the baffle is distributed in the first two modes displaying a periodic behavior at the fundamental frequency, the rest being turbulent flow behavior. The measured dynamical vena contracta coefficient at the inlet is reasonably constant around the value of 0.6 for reed positions far from closure. This is in agreement with existing steady flow analytical models and previous experimental results. V

The rod-airfoil configuration is a benchmark test case for aeroacoustic assessments of vortex- st... more The rod-airfoil configuration is a benchmark test case for aeroacoustic assessments of vortex- structure interaction noise. Several industrial devices are arranged in such a way that down- stream bodies are embedded in the wake of upstream bodies, such as gas turbines, high lift devices, helicopters among others. Aeroacoustic predictions usually rely on time dependent Flow field information obtained from CFD for the determination of the aeroacoustic sources. The present work proposes a novel approach for the aeroacoustic prediction of rod-airfoil noise based on time-resolved PIV experimental data. The aeroacoustic emission of a NACA0012 airfoil in the Karman wake of a rod is investigated by means of 2D TR-PIV in combination with beamforming and microphone measurements. First the time evolving velocity field around the airfoil is measured using high-speed PIV. The corresponding pressure field is then deduced by spatial integration of a Poisson-based algorithm for quasi-2D incompressible flows. Pressure and velocity computed on specific surfaces around the airfoil constitute the source terms of the implemented Curle's and Ffowcs Williams-Hawkings's aeroacoustic analogies. The calculated Sound Pressure Level (SPL) is compared with the measurements obtained by far field microphones. Velocity visualizations in the spanwise direction provide qualitative information about the phase coherence of the vortical impingement along the airfoil span. Parametric studies are performed to evaluate the effect on the acoustic prediction of the position of the integration surface and the numerical discretization methods employed. The vortex release-impinging mechanism revealed to be the main cause of the noise emission. Beamforming visualizations confirmed the major contribution of the airfoil to the total noise radiation. All the calculated acoustic spectra exhibit a main peak corresponding to the rod- shedding frequency. The high frequency components are the most affected by numerical and experimental noise. If the analysis is focused on the tonal peak of the computed spectra the method reveals an accuracy within 10 % of the measured SPL, varying with the spanwise correlation length. This provides good prospects for developments of experimental PIV-based aeroacoustic investigations.Aerospace Engineerin

Running retraining through biofeedback on a measure of impact loading combined with simple instru... more Running retraining through biofeedback on a measure of impact loading combined with simple instruction can decrease running related injuries [1]. Running retraining through real-time biofeedback on a direct measure of impact loading has been exclusively executed on treadmill [1,2]. For example, Peak Tibial Acceleration (PTA) was reduced by provision of simple auditory biofeedback within a single, treadmill-based retraining session [2]. Ecological validity could be improved by conducting retraining programs in an over-ground environment outside the laboratory and with a motivational bio-feedback approach.

The use of music in the fields of sport and rehabilitation has been explored in several ways. Mos... more The use of music in the fields of sport and rehabilitation has been explored in several ways. Mostly, these studies have dealt with the effect of different types or genres of music and the difference between using synchronous or asynchronous music. Within the studies on synchronous music there is some discrepancy as to what is considered to be synchronous. This varies from music with a tempo in the range of the tempo belonging to a certain task, to music that is exactly matched in tempo to the task's tempo. The use of tempo- matching music allows us to even do more fine-grained music alterations: shifting the beat to try to spontaneously manipulate a runner's cadence. Musical tempo has been shown to have an effect on running. Instead of changing running cadence by manipulating the musical tempo, we explored the possibility of manipulating cadence by changing the relative phase angle of the musical beat. Twenty-six recreational runners ran four minutes, nine times. The first ...

Proceedings of the 5th International Conference on Movement and Computing, 2018

Auditory feedbacks are becoming increasingly popular in sports providing opportunities for monito... more Auditory feedbacks are becoming increasingly popular in sports providing opportunities for monitoring and gait (re)training in ecological environments. We present the design process of a sonification strategy for modification of running parameters. The sonification provides real-time feedback of the performance through introduction of distortion of a baseline music track. The music BPM is continuously matched to the runners' cadence. The noise-based continuous feedback was able to significantly alter the mean running cadence in a non-instructed and non-disturbing way and performed better than standard verbal instructions. Although some of the participants did not respond effectively to the feedback, a large majority of the participants positively rated the feedback system in terms of pleasantness and motivation.

Running with music is becoming increasingly popular and software has been developed that provides... more Running with music is becoming increasingly popular and software has been developed that provides music at the runners’ tempo. This work aims at investigating the effect of different music synchronization strategies on runners' foot strike impact. Tests were performed in the Flanders Sports Arena in Ghent with 28 participants. The impact on the tibia was measured by accelerometers. Participants were asked to run in five different synchronization strategy conditions, each starting with a thirty-second no music reference. Speed during each condition was kept constant. Results showed no significant difference in impact among the different synchronization strategies regarding both impact level and SPM. However, a non-negligible average increase of foot strike impact could be observed when running with music compared to running

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Time-resolved Tomographic PIV was used to characterize the flow around the leading edge of a NACA... more Time-resolved Tomographic PIV was used to characterize the flow around the leading edge of a NACA 0012 airfoil in rod-airfoil configuration at ReD = 3500. The volumetric approach at relatively high temporal resolution allows the measurement of the evolution of the 3D vortical structures constituting the Kármán wake of the rod at interaction with the airfoil. The pressure gradient is reconstructed exploiting the definition of Lagrangian derivative and the pressure field is obtained by spatial integration of the Poisson equation. Time-correlation is performed between the aeroacoustic sources of Curle's aeroacoustic analogy and Vortex Sound Theory represented by respectively, time derivative of the pressure fluctuations at the surface and time derivative of the Lamb vector in the surrounding flow. The region of highest correlation is located underneath the airfoil leading edge and appears not to coincide with the region of most intense vortex stretching.

Experiments in Fluids, 2010

In this paper, we discuss techniques by which the aeroacoustic properties of the turbulent flow i... more In this paper, we discuss techniques by which the aeroacoustic properties of the turbulent flow in a rod-airfoil benchmark experiment can be inferred from time-resolved PIV measurement. While acoustic measurements can be made directly using microphones, the proposed techniques provide a means to directly link acoustic waves with specific flow events, which is invaluable in devising noise mitigation strategies. The approaches are possible thanks to recent improvements in digital and camera technology that can provide time-resolved measurements in air flows, necessary for the determination of unsteady flow quantities related to aeroacoustic production. Both techniques are based on Curle's acoustic analogy, where one is based on Lagrangian determination of the required quantities, while the other requires all flow quantities to be converted into Fourier modes. Application of both techniques yields results that are in reasonable agreement with microphone noise measurements for the rod-airfoil experiment.

Saxophonists agree that the detailed geometry of the mouthpiece plays an important role in both p... more Saxophonists agree that the detailed geometry of the mouthpiece plays an important role in both playability and sound production of the saxophone. The hypothesis to be tested in this paper is whether there is difference in 1. radiated sound (in terms of spectral centroid and sound pressure level) and in 2. playability when playing mouthpieces with different internal geometries. The results revealed that the radiated sound is scarcely influenced, but that the playability differs significantly depending on the mouthpiece.

Rod-Airfoil PIV Sound Acoustic Analogy Curle's Analogy Aeroacoustic analysis of a rod-airfoil flo... more Rod-Airfoil PIV Sound Acoustic Analogy Curle's Analogy Aeroacoustic analysis of a rod-airfoil flow by means of timeresolved PIV Left: Predicted wave fronts that are emanating from the airfoil Right: Predicted directivity pattern, green dots represent measurements Problem area The present paper investigates the feasibility of prediction of vortexstructure noise based on time resolved Particle Image Velocimetry (PIV). We consider the case of an airfoil immersed in the wake of a cylindrical rod.

Scientific Reports

Methods to reduce impact in distance runners have been proposed based on real-time auditory feedb... more Methods to reduce impact in distance runners have been proposed based on real-time auditory feedback of tibial acceleration. These methods were developed using treadmill running. In this study, we extend these methods to a more natural environment with a proof-of-concept. We selected ten runners with high tibial shock. They used a music-based biofeedback system with headphones in a running session on an athletic track. The feedback consisted of music superimposed with noise coupled to tibial shock. The music was automatically synchronized to the running cadence. The level of noise could be reduced by reducing the momentary level of tibial shock, thereby providing a more pleasant listening experience. The running speed was controlled between the condition without biofeedback and the condition of biofeedback. The results show that tibial shock decreased by 27% or 2.96 g without guided instructions on gait modification in the biofeedback condition. The reduction in tibial shock did not...

Annals of the New York Academy of Sciences

Musicae Scientiae

Running with musical accompaniment is becoming increasingly popular and several pieces of softwar... more Running with musical accompaniment is becoming increasingly popular and several pieces of software have been developed that match the music tempo to the exerciser’s running cadence, that is, foot strikes per minute. Synchronizing music with running cadence has been shown to affect several aspects of performance output and perception. The purpose of this study was to investigate the effect of synchronous music on runners’ foot impact loading. This represents the ground reaction force on the runner’s lower leg when the foot impacts the ground and is an important parameter for the prevention of tibial fracture injuries. Twenty-eight participants ran five times for three minutes and 30 seconds with a short break between each run. During the first 30 seconds of each running sequence, participants ran at a self-paced tempo without musical accompaniment, and running speed and cadence were measured. Subsequently, they were requested to keep their reference speed constant for the following t...

Journal on Multimodal User Interfaces