Identification of boundary layer structures by unsteady surface pressure measurements

Botero, Laura; Liptiay, Eki; Venner, Cornelis H.; Santana, Leandro D. de

doi:10.2514/6.2022-1649

Cited by 3 publications

(2 citation statements)

References 25 publications

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“…These laminar structures are not fully broken down into smaller turbulent structures, yielding to the higher spectral levels of the WPFs for high frequencies, as was also observed in Ref. [30]. Therefore, for roughness trip heights of k∕δ k ≤ 0.37, the turbulent boundary layer at the TE is not fully developed because laminar structures are still present or small turbulent scales are still being developed.…”

Section: Effects Of the Roughness Trips On The Wall-pressure Fluctuat...mentioning

confidence: 73%

Influence of Roughness Trips on Near- and Far-Field Trailing-Edge Noise

et al. 2022

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Roughness trips are widely applied in wind-tunnel testing to hasten the laminar-turbulent boundary-layer transition. It is well known that they influence the boundary-layer transition and its development. However, their influence on aeroacoustic quantities (in particular, on the airfoil trailing-edge noise) is not yet fully understood. This paper discusses the relationship between the trip height and the boundary-layer development and radiated trailingedge noise. Wind-tunnel experiments were performed with zigzag strips and grit elements placed on the surface of a NACA 0012 airfoil. The roughness trip heights k ranged from 17 to 214% of the undisturbed boundary-layer thickness δ k at the trip location. The chord-based Reynolds number varied from 1.3 × 10 5 to 3.3 × 10 5 . This paper shows that trip heights within 50 to 105% of δ k have little influence on the near field and the trailing-edge noise. However, trips with k∕δ k > 1.05 increase the spectra of velocity and pressure fluctuations in the low-frequency range up to 2.5 and 3 dB, respectively, resulting in an increase of the trailing-edge radiated noise up to 4 dB in a similar frequency range. In summary, this paper shows the importance of carefully defining the roughness trip used to trigger a laminar-turbulent transition in aeroacoustic and aerodynamic measurements.

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Section: Effects Of the Roughness Trips On The Wall-pressure Fluctuat...mentioning

confidence: 73%

Influence of Roughness Trips on Near- and Far-Field Trailing-Edge Noise

et al. 2022

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“…For the no trip case, peaks attributed to TS waves [22] in the boundary layer were observed in the low-frequency range. The spectrum reached a plateau after 1 kHz.…”

Section: B Transition Processmentioning

confidence: 98%

Tripping Device Effects on the Turbulent Boundary Layer Development

Santos

Venner

Santana

2022

AIAA AVIATION 2022 Forum

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Study of the development of a boundary layer using the remote microphone probe technique

et al. 2023

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The experimental identification of the transition region and the different flow structures inside the boundary layer is still a challenge. For the first time, this research uses the remote microphone probe technique to experimentally evaluate the boundary layer development, the transition process, and the type of flow structures. The remote microphone probe technique is an effective and accurate experimental method to measure wall-pressure fluctuations. The development of the boundary layer was evaluated under natural and forced transition for different inflow velocities and angles of attack. Results of the wall-pressure spectrum, spanwise coherence at different chord positions, and the spanwise correlation length close to the trailing edge are presented. Furthermore, boundary layer and far-field noise measurements at several conditions are also shown. This paper shows the growth of the turbulent structures that contain most of the turbulent energy along the airfoil chord. Further, it is demonstrated that the spanwise correlation length increases with the inflow velocity. Results for the no forced transition cases form a complete database to determine the different transition stages, which were linked with different components of the wall-pressure spectra. The primary and secondary instability mechanisms leading the transition process appear in the wall-pressure spectrum as peaks and a hump, respectively. The two- and three-dimensional nature of the boundary layer structures is also discussed by analyzing the spanwise coherence. Finally, it is shown that when two-dimensional structures reach the airfoil trailing edge, a feedback loop between the acoustic waves at the airfoil trailing edge and a point upstream in the airfoil surface is generated. This feedback loop influences the wall-pressure fluctuations along the entire airfoil chord. Graphical abstract

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Identification of boundary layer structures by unsteady surface pressure measurements

Cited by 3 publications

References 25 publications

Influence of Roughness Trips on Near- and Far-Field Trailing-Edge Noise

Influence of Roughness Trips on Near- and Far-Field Trailing-Edge Noise

Tripping Device Effects on the Turbulent Boundary Layer Development

Study of the development of a boundary layer using the remote microphone probe technique

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