TY - GEN A1 - Geyer, Thomas A1 - Enghardt, Lars T1 - Noise generation by two staggered circular cylinders of equal diameter in cross-flow T2 - 28th AIAA/CEAS Aeroacoustics Conference 2019, Southampton, UK, 14 - 18 June 2022 Y1 - 2022 U6 - https://doi.org/10.2514/6.2022-3093 ER - TY - GEN A1 - Neubauer, Moritz A1 - Genßler, Julia A1 - Radmann, Vincent A1 - Kohlenberg, Fleming A1 - Pohl, Michael A1 - Böhme, Kurt A1 - Knobloch, Karsten A1 - Sarradj, Ennes A1 - Höschler, Klaus A1 - Modler, Niels A1 - Enghardt, Lars T1 - Experimental and Numerical Investigation of Novel Acoustic Liners and Their Design for Aero-Engine Applications T2 - Aerospace N2 - This paper presents a combined experimental and numerical investigation on a novel liner concept for enhanced low-frequency and broadband acoustic attenuation. In particular, two different realizations, derived from conventional Helmholtz resonators (HR) and plate resonators (PR) are investigated, which both deploy flexible materials with material inherent damping. In this context, a comprehensive experimental investigation was carried out focusing the identification and evaluation of various geometric parameters and material properties on the acoustics dissipation and related properties of various materials in a simplified setup of a single Helmholtz resonator with flexible walls (FHR concept). Furthermore, a parameter study based on analytical models was performed for both liner concepts, taking into account material as well as geometric parameters and their effects on transmission loss. In addition, design concepts that enable cylindrical or otherwise curved liner structures and the corresponding manufacturing technologies are presented, while considering essential structural features such as drainage. With respect to the potential application in jet engines, a structural–mechanical analysis considering the relevant load cases to compare and discuss the mechanical performance of a classical HR and the FHR concept liner is presented. Finally, both concepts are evaluated and possible challenges and potentials for further implementation are described. Y1 - 2023 U6 - https://doi.org/10.3390/aerospace10010005 SN - 2226-4310 VL - 10 IS - 1 ER - TY - GEN A1 - Geyer, Thomas A1 - Enghardt, Lars T1 - Minderung von turbulenzinduziertem Schall an Lüftern durch perforierte Blattvorderkanten T2 - Fortschritte der Akustik - DAGA, 49. Jahrestagung für Akustik Y1 - 2023 UR - https://pub.dega-akustik.de/DAGA_2023/data/index.html 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 - 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 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 -