TY - GEN A1 - Kershner, John A1 - Jaworski, Justin A1 - Geyer, Thomas T1 - Experimental study of trailing-edge bluntness noise reduction by porous plates T2 - AIAA AVIATION 2023 Forum, 12-16 June 2023, San Diego, CA and Online Y1 - 2023 U6 - https://doi.org/10.2514/6.2023-4284 ER - TY - GEN A1 - Geyer, Thomas A1 - Enghardt, Lars T1 - Experimental Evaluation of the Turbulence Interaction Noise Reduction by Flat Plates with Perforated Leading Edges T2 - AIAA AVIATION 2023 Forum, 12-16 June 2023 Y1 - 2023 U6 - https://doi.org/10.2514/6.2023-4287 ER - TY - GEN A1 - Kershner, John A1 - Geyer, Thomas A1 - Jaworski, Justin T1 - Setup for experimental study of porous plate acoustics and local flow features T2 - Fortschritte der Akustik - DAGA, 49. Jahrestagung für Akustik Y1 - 2023 UR - https://pub.dega-akustik.de/DAGA_2023/data/articles/000077.pdf SP - 530 EP - 533 ER - TY - GEN A1 - Lyu, Benshuai A1 - Xu, Jiali A1 - Geyer, Thomas A1 - Paruchuri, Chaitanya A1 - Ye, Qingqing A1 - Cui, Jiahuan A1 - Ayton, Lorna T1 - Experimental investigation into the acoustical superiority of ogee serrations in reducing leading edge noise T2 - Applied Acoustics Y1 - 2024 UR - https://www.sciencedirect.com/science/article/pii/S0003682X23005200 U6 - https://doi.org/10.1016/j.apacoust.2023.109722 SN - 1872-910X SN - 0003-682X VL - 216 ER - TY - GEN A1 - Abromeit, Paul A1 - Raghuram, Priyanka A1 - Geyer, Thomas Fritz A1 - Enghardt, Lars ED - DEGA e.V., T1 - Investigation on aerodynamic noise generated by porous coated, staggered tandem cylinders T2 - Proceedings of DAS|DAGA 2025 : 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen N2 - The aerodynamic noise generated by the landing gear of an aircraft or the protective guard grille of a fan is often studied by a tandem cylinder configuration, modeling the interaction between main strut and hydraulic lines and the rods of the mesh, respectively. Previous investigations have shown that the angle between the upstream and downstream cylinder has a great effect on the peak sound pressure level. The present study describes both acoustic and hot-wire measurements of a tandem cylinder configuration to investigate the flow field around the staggered cylinders and to evaluate the effects of porous coatings of the cylinders. A cylinder spacing of S = 4.7D was used, where D represents the diameter of the cylinders. Spacing and diameter of the cylinders are known to affect the flow behavior. The results show that increasing the angle up to a certain limit of 30° to 35° leads to complex interactions of the wake flows. For large angles, the interference between the two cylinders decreases. It can also be observed that porous materials with high permeability reduce the tonal noise better than materials with low permeability, effectively shifting the peak towards lower frequencies. Y1 - 2025 UR - https://pub.dega-akustik.de/DAS-DAGA_2025/files/upload/paper/165.pdf SN - 978-3-939296-23-2 U6 - https://doi.org/10.71568/dasdaga2025.165 SP - 521 EP - 524 PB - Deutsche Gesellschaft für Akustik e.V. CY - Berlin ER - TY - GEN A1 - Abromeit, Paul A1 - Geyer, Thomas A1 - Enghardt, Lars T1 - Aerodynamische Schallentstehung an zwei versetzt angeordneten Zylindern gleichen Durchmessers T2 - Fortschritte der Akustik - DAGA, 50. Jahrestagung für Akustik N2 - Die komplexe Umströmung von zwei versetzt angeordneten Zylindern ist in verschiedenen technischen Anwendungen, wie zum Beispiel dem Fahrwerk von Flugzeugen oder Schutzgittern von Ventilatoren, wiederzufinden. Obwohl es zahlreiche numerische und experimentelle Untersuchungen zu diesem Aufbau gibt, beschäftigen sich nur wenige davon mit der Schallentstehung. In der hier vorgestellten Untersuchung wurde die Schallentstehung einer Tandemzylinderanordnung bei verschiedenen Anstellwinkeln in einem kleinen akustischen Freistrahlwindkanal bei Reynolds-Zahlen (bezogen auf den Zylinderdurchmesser) zwischen 3.300 und 11.500 gemessen. Der Winkel zwischen den Zylindern wurde zwischen 0° und 90° in Schritten von 5° variiert. Die resultierenden Spektren der Schalldruckpegel zeigen auffällige tonale Merkmale und bei bestimmten Winkeln und Abständen zwischen den Zylindern konnte ein bistabiles Verhalten beobachtet werden. Dabei teilt sich das tonale Maximum des Spektrums in zwei Maxima auf und vereinigt sich bei höheren Anstellwinkeln wieder zu einem Maximum. Zum besseren Verständnis dieser Mechanismen wurden für verschiedene Anstellwinkel qualitative Strömungssimulationen durchgeführt. Y1 - 2024 UR - https://pub.dega-akustik.de/DAGA_2024/konferenz?article=589 ER - TY - GEN A1 - Geyer, Thomas Fritz A1 - Abromeit, Paul A1 - Prügel, Maximilian T1 - Noise generation by tandem cylinders of different diameter in cross-flow T2 - Proceedings of DAS|DAGA 2025 : 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen N2 - The noise generation by two circular cylinders placed in a tandem configuration is of large interest in aeroacoustic research, as it constitutes a simple model for technical applications like parts of the landing gear of aircraft or the protective guard grille of axial fans. The resulting tonal noise depends on parameters such as the diameter of the cylinders and their spacing, the angle between the cylinders with respect to the flow and the flow velocity and inflow turbulence parameters. In a recent study in a small aeroacoustic wind tunnel facility, the far-field noise generated by parallel tandem cylinders with different diameter was measured for various cylinder spacings, allowing for the analysis of the effect that the wake impingement of the upstream cylinder on the downstream cylinder has on the tonal noise. In the paper, results from these experiments are presented and discussed together with results from flow field measurements that enable a better understanding of the physical noise generation mechanisms. Y1 - 2025 UR - http://pub.dega-akustik.de/DAS-DAGA_2025/files/upload/paper/242.pdf SN - 978-3-939296-23-2 U6 - https://doi.org/10.71568/dasdaga2025.242 SP - 525 EP - 528 PB - Deutsche Gesellschaft für Akustik e.V. CY - Berlin ER - TY - GEN A1 - Geyer, Thomas A1 - Lucius, Andreas A1 - Schneider, Marc A1 - Enghardt, Lars T1 - Aerodynamic noise from circular cylinders under turbulent inflow conditions T2 - AIAA journal N2 - The aerodynamic noise generated by a circular cylinder in a subsonic crossflow is a classical problem in aeroacoustics, which has been investigated experimentally and numerically in the past. The presence of a turbulent inflow is known to have an effect on the generation of tonal noise due to vortex shedding, although the available experimental data are sparse. The present paper describes an experimental study on the noise generated by a set of circular cylinders in grid-generated turbulence conducted in an aeroacoustic wind tunnel facility. Acoustic measurements were performed using microphone array technology. The results show that the free stream turbulence broadens the spectral peak of the vortex shedding tones, especially for cylinders with a diameter that is small compared to the turbulent integral length scale. One key result of the study is that the turbulent inflow leads to an increase in the vortex shedding Strouhal number compared to the case with clean inflow as well as to an additional increase of the Strouhal number with Reynolds number. This trend can also be observed qualitatively in the velocity power spectral densities measured in the wake of a selected cylinder using hot-wire anemometry. Y1 - 2025 U6 - https://doi.org/10.2514/1.J064504 SN - 1533-385X VL - 63 IS - 8 SP - 3250 EP - 3260 PB - AIAA CY - Reston, Va. ER -