Finlet rails for the reduction of the trailing-edge noise

The present study focuses on the application of finlet rails as a passive technique of flow control to mitigate trailing-edge noise. Finlet rails are small cylinders whose axes are aligned along the streamwise direction, transversally positioned with respect to the trailing edge. In the first part of this study, the effects of finlet geometry...

Jet noise predictions by time marching of single-snapshot tomographic PIV fields

Abstract: This work combines the latest advancements in time marching of 3D vector fields from tomographic particle image velocimetry, with an adapted version of Lighthill’s formulation, for the prediction of far-field jet noise. Three-dimensional velocity vector fields of the jet flow are first reconstructed from a tomographic volume of 4× 3...

Streamwise fences for the reduction of trailing-edge noise in a NACA633018 airfoil

Streamwise fences for the reduction of the trailing-edge noise are experimentally investigated on a NACA633018 airfoil. Interchangeable trailing-edge inserts with streamwise fences of different spacing and height are tested in an anechoic wind tunnel. Far-field trailing-edge noise was measured by an array of microphone and the airfoil drag was...

Tomographic long-distance µPIV to investigate the small scales of turbulence in a jet at high Reynolds number

The small scales of turbulence in a high-Reynolds-number jet (R e λ≈ 350) are investigated with a µPIV setup to overcome the optical limitations of conventional tomographic PIV setups. With the aim of validating the performances of tomographic long-distance µPIV, analyses are carried out involving statistical aspects of the small scales of...

Near-field coherent structures in circular and fractal orifice jets

To investigate the influence of the orifice geometry on near-field coherent structures in a jet, Fourier proper orthogonal decomposition (Fourier-POD) is applied. Velocity and vorticity snapshots obtained from tomographic particle image velocimetry at the downstream distance of two equivalent orifice diameters are analyzed. Jets issuing from...

Small-scale motions in turbulent boundary-free shear flows

The present work is an experimental and numerical investigation of the small-scale motions in turbulent free-shear flows. In the far-field turbulence of a jet at high Reynolds number (Re? = 350) hot-wire anemometry (HWA) is applied to measure time series of flow velocity. By filtering these time series, large- and small-scale velocity...

Scale dependence of the alignment between strain rate and rotation in turbulent shear flow

The scale dependence of the statistical alignment tendencies of the eigenvectors of the strain-rate tensor ei, with the vorticity vector ω, is examined in the self-preserving region of a planar turbulent mixing layer. Data from a direct numerical simulation are filtered at various length scales and the probability density functions of the...

Scale interaction in a mixing layer: The role of the large-scale gradients

The interaction between scales is investigated in a turbulent mixing layer. The large-scale amplitude modulation of the small scales already observed in other works depends on the crosswise location. Large-scale positive fluctuations correlate with a stronger activity of the small scales on the low speed-side of the mixing layer, and a reduced...

Scale interaction in a mixing layer: The role of the large-scale gradients

The interaction between scales is investigated in a turbulent mixing layer. The large-scale amplitude modulation of the small scales already observed in other works depends on the crosswise location. Large-scale positive fluctuations correlate with a stronger activity of the small scales on the low speed-side of the mixing layer, and a reduced...

Long-range lPIV to resolve the small scales in a jet at high Reynolds number

The investigation of flows at high Reynolds number is of great interest for the theory of turbulence, in that the large and the small scales of turbulence show a clear separation. But, as the Reynolds number of the flow increases, the size of the Kolmogorov length scale ( ? ) drops almost proportionally. Aiming at achieving the adequate spatial...

Amplitude and frequency modulation of the small scales in a turbulent jet

This work involves the large-scale amplitude and frequency modulation of the small-scale motions in fullydeveloped turbulence of a high Reynolds number jet. The scales responsible for the production of turbulent kinetic energy (large scales), and those responsible for its viscous dissipation (small scales) are extracted from time series of...

Long-range μPIV in the turbulent region of a jet, at high Reynolds numbers

The present work involves the investigation of the fine scale motions in the turbulent region of a high Reynolds number air jet. In the fully developed region of the jets, the small scales of turbulence are assumed to be isotropic, and expected to contain elongated vortices (worms), whose diameter scales with the Kolmogorov length scale. Aimed...

Long-range ?PIV in the turbulent region of a jet, at high Reynolds numbers

The present work involves the investigation of the fine scale motions in the turbulent region of a high Reynolds number air jet. In the fully developed region of the jets, the small scales of turbulence are assumed to be isotropic, and expected to contain elongated vortices (worms), whose diameter scales with the Kolmogorov length scale. Aimed...