Aeroacoustic Investigation of Rod-Airfoil Noise based on Time-Resolved PIV

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

Influence of mouthpiece geometry on saxophone playing

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.Design EngineeringIndustrial Design Engineerin

Embracing the digital in instrument making: Towards a musician-tailored mouthpiece by 3D printing

At present, the manufacturing of musical instruments still strongly relies on the tacit knowledge of experienced handcrafts while is commonly based on standard machining or casting techniques. This limits the musician-tailoredness to a small group of players, while others take compromises by employing stock parts. The present article describes a new methodology for the design and production of woodwind instruments mouthpieces. By embracing digital modeling and manufacturing, this methodology encompasses four phases, which can be cut short when necessary. The aim of the presented methodology is to link the geometry of the mouthpiece to tone properties. Based on 3D printing, the inside geometry can be altered to complex and reproducible detail to obtain the desired acoustic features - eventually leading to mouthpiece geometries tailored to the player’s sound and playability requirements. The results of aerodynamic investigations together with the subjective experience of saxophone players have been used to design mouthpieces with modified inside geometries of both baffle and chamber. Prototypes have been produced at the Delft University of Technology (TU Delft) using several 3D printing technologies and different materials. Both professional and amateur saxophone players tested these at the Royal Conservatoire of The Hague and at the North Sea Jazz festival (Rotterdam 2012). Based on the judgment of the players, specific geometrical features were revealed to emphasize specific tone characteristics. A number of professional players are actively performing with our mouthpieces. The application and further development of the methodology will lead to a better empirical basis to reason about acoustics and playability, and can be applied to other instruments as well. Future work includes additional measurements and developing a parameterized datdatabase of 3D modelsDesign EngineeringIndustrial Design Engineerin

Combined Particle Image Velocimetry and acoustic measurements on a rod-airfoil configuration: Pilot test of the FLOVIST project

Aerospace Engineerin