Investigation of aeroacoustic noise generation by simultaneous particle image velocimetry and microphone measurements

Henning, Аrne; Kaepernick, Kristian; Ehrenfried, Klaus; Koop, Lars; Dillmann, Andreas

doi:10.1007/s00348-008-0528-y

Cited by 66 publications

(34 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They also showed that Lighthill stress tensor can be statistically modeled by space-time second-order velocity correlations. Recalling Howe's acoustic analogy, Henning et al 44 performed planar PIV and phased-microphone-array measurements and investigated the acoustic source in the vicinity of a circular cylinder and an airfoil leading-edge slat by crosscorrelation function between the acoustic pressure and velocity/vorticity fluctuations. In cavity flows, Haigermoser, 45 and later Koschatzky et al, 46 reconstructed the pressure field from time-resolved planar PIV and then predicted far-field acoustics by Curle's analogy using the pressure information on the cavity surface.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional evolution of flow structures in transitional circular and chevron jets

2011

View full text Add to dashboard Cite

The three-dimensional behavior of flow transition in circular and 6-chevron jets at Re ¼ 5000 is investigated with experiments conducted on a free water jet by time-resolved tomographic particle image velocimetry. The emphasis is on the unsteady organization of coherent flow structures, which play a role in the generation of acoustic noise. Shedding and pairing of vortices are the most pronounced phenomena observed in the near field of the circular jet. The first and second pairing amplify the axial pulsatile motion in the jet column and lead to the growth of azimuthal waves culminating in the breakup of the vortex ring. Streamwise vortices of axial and radial vorticity are observed in the outer region and move inward and outward under the effect of the vortex rings. In the jet with chevrons, the axisymmetric ring-like coherence of the circular jet is not encountered. Instead, streamwise flow structures of azimuthal vorticity emanate from the chevron apices, and counter-rotating streamwise vortices of axial and radial vorticity develop from the chevron notches. The decay of streamwise vortices is accompanied by the formation of C-shaped structures. The three-dimensional analysis allows quantifying the vortex stretching and tilting activity, which, for the circular jet exit, is related to the azimuthal instabilities and the streamwise vortices connecting the vortex rings. In the chevron jet, stretching and tilting peak during the formation of C-structures. Following Powell's aeroacoustic analogy, the spatial distribution of the source term is mapped, evaluating the temporal derivative of the Lamb vector. The spatio-temporal evolution of such source term is visualized revealing that the events of highest activity are associated with the processes of vortex-ring pairing and vortex-ring disruption for the circular jet, and with the decay of streamwise instabilities and the formation of C-shaped structures for the chevron case.

show abstract

Section: Introductionmentioning

confidence: 99%

Three-dimensional evolution of flow structures in transitional circular and chevron jets

2011

View full text Add to dashboard Cite

show abstract

“…The particle image velocimetry (PIV) is obviously used in fluid mechanics (Raffel et al, 2007). The proposed adaptation of the noninvasive laser methods for acoustical purposes (A-PIV) gives us the opportunity to explain many vibroacoustical phenomena and allows to complete missing knowledge about disturbed acoustic flows in real systems (Henning et al, 2008). Figure 6 shows the experimental acoustic square waveguide model investigated with the PIV technique.…”

Section: Laser Methods Measurement Resultsmentioning

confidence: 99%

Experimental Acoustic Flow Analysis Inside a Section of an Acoustic Waveguide

Weyna¹,

Mickiewicz²,

Pyla³

et al. 2013

Archives of Acoustics

View full text Add to dashboard Cite

Noise propagation within ducts is of practical concern in many areas of industrial processes where a fluid has to be transported in piping systems. The paper presents experimental data and visualization of flow in the vicinity of an abrupt change in cross-section of a circular duct and on obstacles inside where the acoustic wave generates nonlinear separated flow and vortex fields.For noise produced by flow wave of low Mach number, laminar and turbulent flows are studied using experimental sound intensity (SI) and laser particle image velocimetry (PIV) technique adopted to acoustics (A-PIV). The emphasis is put on the development and application of these methods for better understanding of noise generation inside the acoustic ducts with different cross-sections. The intensity distribution inside duct is produced by the action of the sum of modal pressures on the sum of modal particle velocities. However, acoustic field is extremely complicated because pressures in non-propagating (cut-off) modes cooperate with particle velocities in propagating modes, and vice versa. The discrete frequency sound is strongly influenced by the transmission of higher order modes in the duct. By understanding the mechanism of energy in the sound channels and pipes we can find the best solution to noise abatement technology.In the paper, numerous methods of visualization illustrate the vortex flow as an acoustic velocity or sound intensity stream which can be presented graphically. Diffraction and scattering phenomena occurring inside and around the open-end of the acoustic duct are shown.

show abstract

“…Cross-correlation between the acoustic pressure and velocity or vorticity fluctuations (Henning et al 2008) was applied to characterize flow structures involved in noise production. From the temporal evolution of the cross-correlation coefficient, the authors suggested that the source region was located by the leading edge of the airfoil.…”

Section: Introductionmentioning

confidence: 99%

Lagrangian and Eulerian pressure field evaluation of rod-airfoil flow from time-resolved tomographic PIV

2010

View full text Add to dashboard Cite

This work investigates the rod-airfoil air flow by time-resolved Tomographic Particle Image Velocimetry (TR-TOMO PIV) in thin-light volume configuration. Experiments are performed at the region close to the leading edge of a NACA0012 airfoil embedded in the von Kármán wake of a cylindrical rod. The 3D velocity field measured at 5 kHz is used to evaluate the instantaneous planar pressure field by integration of the pressure gradient field. The experimental data are treated with a discretized model based on multiple velocity measurements. The time separation used to evaluate the Lagrangian derivative along a fluid parcel trajectory has to be taken into account to reduce precision error. By comparing Lagrangian and Eulerian approaches, the latter is restricted to shorter time separations and is found not applicable to evaluate pressure gradient field if a relative precision error lower than 10% is required. Finally, the pressure evaluated from tomographic velocity measurements is compared to that obtained from simulated planar ones to discuss the effect of 3D flow phenomena on the accuracy of the proposed technique.

show abstract

Investigation of aeroacoustic noise generation by simultaneous particle image velocimetry and microphone measurements

Cited by 66 publications

References 24 publications

Three-dimensional evolution of flow structures in transitional circular and chevron jets

Three-dimensional evolution of flow structures in transitional circular and chevron jets

Experimental Acoustic Flow Analysis Inside a Section of an Acoustic Waveguide

Lagrangian and Eulerian pressure field evaluation of rod-airfoil flow from time-resolved tomographic PIV

Contact Info

Product

Resources

About