Pressure fluctuations from large-scale PIV over a serrated trailing edge

Pereira, Lourenço Tércio Lima; Ragni, Daniele; Avallone, Francesco; Scarano, Fulvio

doi:10.1007/s00348-020-2888-x

Cited by 14 publications

(9 citation statements)

References 43 publications

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“…The boundary layer was tripped at a distance of 5 cm after the leading edge of the plate using distributed roughness elements of 1.0 cm height (Lima Pereira et al, 2020). The schematic layout of the experiment is illustrated in Fig.…”

Section: A Wind Tunnel and Oscillating Wallmentioning

confidence: 99%

3-dimensional particle image velocimetry based evaluation of turbulent skin-friction reduction by spanwise wall oscillation

et al. 2020

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The reduction of turbulent skin-friction drag and the response of vortical structures in a zero-pressure gradient, turbulent boundary layer subjected to spanwise wall oscillation is investigated using planar and tomographic particle image velocimetry (PIV). The experiments are conducted at a momentum based Reynolds number of 1000, while the range of spanwise oscillation amplitude and frequency is chosen around the optimum reported in previous studies. A high-resolution planar PIV measurement is employed to determine the drag reduction directly from wall shear measurements and to analyze the accompanying modifications in the turbulent vortical structures. Drag reduction of up to 15% is quantified, with variations following the trends reported in the literature. The analysis of the turbulence structure of the flow is made in terms of Reynolds shear stresses, turbulence production, and vortex visualization. A pronounced drop of turbulence production is observed up to a height of 100 wall units from the wall. The vorticity analysis, both in the streamwise wall-normal plane and in the volumetric results, indicates a reduction of vorticity fluctuations in the near-wall domain. A distortion of the hairpin-packet arrangement is hypothesized, suggesting that the drag-reduction mechanism lies in the inhibition of the hairpin auto-generation by the spanwise wall oscillations.

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Section: A Wind Tunnel and Oscillating Wallmentioning

confidence: 99%

3-dimensional particle image velocimetry based evaluation of turbulent skin-friction reduction by spanwise wall oscillation

et al. 2020

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“…The wall-pressure fluctuations are primarily used as input for the modelling of trailing-edge noise generation (Amiet 1976), but they have only been studied in recent works (Chong & Vathylakis 2015;Avallone et al 2017Avallone et al , 2018Ragni et al 2019;Lima Pereira et al 2020). Although these works have illustrated the overall distribution of the wall pressure on the surface of serrations, the underlying causes of its distortions have not yet been established.…”

Section: Introductionmentioning

confidence: 99%

A physics-based description and modelling of the wall-pressure fluctuations on a serrated trailing edge

et al. 2022

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A physical description of the flow mechanisms that govern the distribution of the wall-pressure fluctuations over the surface of a serrated trailing edge is proposed. Three main mechanisms that define the variation of turbulent pressure fluctuations across the serrated edge are discussed and semi-empirical models are formulated accordingly. It is shown that the intensity of the wall-pressure fluctuations increases at the tips under the effect of an increased convective velocity as a result of sidewise momentum diffusion. Furthermore, the change of impedance across the edge causes a local reduction of the pressure fluctuations in the vicinity of the trailing edge. Finally, aerodynamic loading over the serrations due to the non-symmetric flow created at different angles of attack establishes secondary flow patterns that induce higher wall-pressure fluctuations over the serration edges. The latter effect is present only for serrations under high aerodynamic loading, while the former ones are observed under any conditions. Semi-empirical models are formulated for predicting the variation of the wall-pressure fluctuations over the serration surface based on the three physical mechanisms described. These models are calibrated and compared against experiments conducted on a symmetric airfoil model at high Reynolds numbers.

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“…The use of submillimetre HFSB has been reported to reflect 10 4 to 10 5 times more light than micrometre particles (Caridi 2018). In the past two decades, HFSB have been applied to several PIV experiments at metre scale: aircraft cabins (Bosbach et al 2009), wind turbines (Caridi et al 2016), thermal plumes (Huhn et al 2017), aeronautics (Sciacchitano et al 2018), full-scale cyclists (Jux et al 2018;Terra et al 2019;Spoelstra et al 2019), aeroacoustics (Lima Pereira et al 2020) and bird flight (Usherwood et al 2020).…”

Section: Introductionmentioning

confidence: 99%

The slip velocity of nearly neutrally buoyant tracers for large-scale PIV

Faleiros

Tuinstra²,

Sciacchitano

et al. 2021

Exp Fluids

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The behaviour of nearly neutrally buoyant tracers is studied by means of experiments with helium-filled soap bubbles and numerical simulations. The current models used for estimating the slip velocity of heavy micro particles and neutrally buoyant particles are reviewed and extended to include the effect of unsteady forces and particle Reynolds number. The particle motion is analysed via numerical simulations of a rectilinear oscillatory flow and in the flow around an airfoil within a particle flow parameter space that is typical of large-scale PIV experiments. An empirical relation is obtained that estimates the particle slip velocity, depending on the particle-to-fluid density ratio, the particle Reynolds number and frequency of the local flow fluctuations. The model developed is applied to assess the slip velocity of helium-filled soap bubbles in a large-scale experiment conducted at the German–Dutch wind (DNW) tunnels in the flow around an airfoil, with chord Reynolds numbers up to three millions. Furthermore, a procedure is proposed that can be used to retrieve the bubbles mean density and dispersion from measurements of mean velocity and fluctuations, respectively. Graphic abstract

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Pressure fluctuations from large-scale PIV over a serrated trailing edge

Cited by 14 publications

References 43 publications

3-dimensional particle image velocimetry based evaluation of turbulent skin-friction reduction by spanwise wall oscillation

3-dimensional particle image velocimetry based evaluation of turbulent skin-friction reduction by spanwise wall oscillation

A physics-based description and modelling of the wall-pressure fluctuations on a serrated trailing edge

The slip velocity of nearly neutrally buoyant tracers for large-scale PIV

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