@misc{SharmaGeyerArcondoulis, author = {Sharma, Sparsh and Geyer, Thomas and Arcondoulis, Elias}, title = {Effect of Coating Thickness on Aerodynamic Noise Reduction by Porous-Coated Cylinders}, series = {28th AIAA/CEAS Aeroacoustics Conference 2022, Southampton, UK, 14 - 18 June 2021}, journal = {28th AIAA/CEAS Aeroacoustics Conference 2022, Southampton, UK, 14 - 18 June 2021}, doi = {10.2514/6.2022-2889}, language = {en} } @misc{SharmaGeyer, author = {Sharma, Sparsh and Geyer, Thomas}, title = {Numerical Investigation of Aerodynamic Noise Generation by Porous-Coated Staggered Cylinders}, series = {28th AIAA/CEAS Aeroacoustics Conference 2019, Southampton, UK, 14 - 18 June 2022}, journal = {28th AIAA/CEAS Aeroacoustics Conference 2019, Southampton, UK, 14 - 18 June 2022}, doi = {10.2514/6.2022-2890}, language = {en} } @misc{GeyerEnghardt, author = {Geyer, Thomas and Enghardt, Lars}, title = {Noise generation by two staggered circular cylinders of equal diameter in cross-flow}, series = {28th AIAA/CEAS Aeroacoustics Conference 2019, Southampton, UK, 14 - 18 June 2022}, journal = {28th AIAA/CEAS Aeroacoustics Conference 2019, Southampton, UK, 14 - 18 June 2022}, doi = {10.2514/6.2022-3093}, language = {en} } @misc{PallejaCabreChaitanyaJosephetal., author = {Palleja-Cabre, Sergi and Chaitanya, Paruchuri and Joseph, Phillip and Kim, Jae-Wook and Priddin, Matthew and Ayton, Lorna and Geyer, Thomas and Chong, Tze Pei}, title = {Downstream porosity for the reduction of turbulence-aerofoil interaction noise}, series = {Journal of Sound and Vibration}, journal = {Journal of Sound and Vibration}, issn = {0022-460X}, doi = {10.1016/j.jsv.2022.117324}, pages = {17}, language = {en} } @misc{SchneehagenGeyerSarradj, author = {Schneehagen, Erik W. and Geyer, Thomas and Sarradj, Ennes}, title = {Reduzierung des Eigenger{\"a}uschs von Tragfl{\"u}geln durch Seitenplatten}, series = {Fortschritte der Akustik - DAGA, 48. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 48. Jahrestagung f{\"u}r Akustik}, language = {de} } @misc{LuciusGeyerDietrichetal., author = {Lucius, Andreas and Geyer, Thomas and Dietrich, Philipp and Dietrich, Marc and Ruck, Richard}, title = {Experimentelle und numerische Untersuchungen eines Tragfl{\"u}gelprofils unter gest{\"o}rten Zustr{\"o}mbedingungen}, series = {Fortschritte der Akustik - DAGA, 48. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 48. Jahrestagung f{\"u}r Akustik}, language = {de} } @misc{CzwielongBerchtenbreiterOckeretal., author = {Czwielong, Felix and Berchtenbreiter, Benedikt and Ocker, Christof and Geyer, Thomas and Stockmeier, Gabriel and Merkel, Markus and Becker, Stefan}, title = {On the Application and Limitations of Sound-Absorbing Materials for Axial Fan Blades}, series = {FAN 2022 - International Conference on Fan Noise, Aerodynamics, Applications and Systems}, journal = {FAN 2022 - International Conference on Fan Noise, Aerodynamics, Applications and Systems}, pages = {10}, language = {en} } @misc{SchneehagenGeyerSarradj, author = {Schneehagen, Erik W. and Geyer, Thomas and Sarradj, Ennes}, title = {Influence of end plate placement on the reduction of airfoil tip vortex formation noise}, series = {Acta Acustica}, volume = {6}, journal = {Acta Acustica}, issn = {2681-4617}, doi = {10.1051/aacus/2022053}, pages = {1 -- 14}, language = {en} } @misc{SharmaGeyerArcondoulis, author = {Sharma, Sparsh and Geyer, Thomas and Arcondoulis, Elias}, title = {On the influence of porous coating thickness and permeability on passive flow and noise control of cylinders}, series = {Journal of Sound and Vibration}, journal = {Journal of Sound and Vibration}, doi = {10.1016/j.jsv.2023.117563}, language = {en} } @misc{GeyerSchneehagenHeroldetal., author = {Geyer, Thomas and Schneehagen, Erik W. and Herold, Gert and Zhang, Tingyi and Moreau, Danielle J.}, title = {Reduction of rotor aerodynamic noise using porous blade tips}, series = {Fortschritte der Akustik - DAGA, 50. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 50. Jahrestagung f{\"u}r Akustik}, pages = {4}, abstract = {Motivated by promising results from experiments on the noise reduction performance of finite wall-mounted airfoils with a porous tip in an aeroacoustic wind tunnel, corresponding measurements were performed in a dedicated rotor test rig. This rig features a 3 kW direct-drive electric motor with three rotor blades of 1.1 m diameter. In the experiments, a variety of different tip modifications was tested regarding their noise reducing performance, including different porous materials that were manufactured using rapid prototyping. Acoustic measurements were performed at different rotationals speeds and blade angles using a ring-shaped microphone array consisting of 60 evenly spaced microphones. The rotational speed was measured using a laser sensor. Different beamforming algorithms were used in post-processing to help analyzing the data. The results show that porous tips can lead to a notable noise reduction at low frequencies, but a small penalty at medium and high frequencies which may be due to the surface roughness of the porous tips. This trend seems more severe for lower blade angles than for higher ones. These findings agree well with those obtained from the previous wind tunnel measurements.}, language = {en} } @misc{KaraHenkeGeyer, author = {Kara, Emre and Henke, Anna-Sophia and Geyer, Thomas}, title = {Konzeption und Inbetriebnahme eines kleinen Messaufbaus f{\"u}r Freistrahll{\"a}rm}, series = {Fortschritte der Akustik - DAGA, 49. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 49. Jahrestagung f{\"u}r Akustik}, pages = {4}, language = {de} } @misc{GeyerEnghardt, author = {Geyer, Thomas and Enghardt, Lars}, title = {Minderung von turbulenzinduziertem Schall an L{\"u}ftern durch perforierte Blattvorderkanten}, series = {Fortschritte der Akustik - DAGA, 49. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 49. Jahrestagung f{\"u}r Akustik}, pages = {4}, language = {de} } @misc{GeyerVelpulaSharma, author = {Geyer, Thomas and Velpula, Rishi and Sharma, Sparsh}, title = {Experimental Investigation of Tonal Noise Radiation from Trapezoidal Cylinders in Cross-Flow}, series = {AIAA AVIATION 2023 Forum, 12-16 June 2023, San Diego, CA and Online}, journal = {AIAA AVIATION 2023 Forum, 12-16 June 2023, San Diego, CA and Online}, doi = {10.2514/6.2023-3496}, language = {en} } @misc{KershnerJaworskiGeyer, author = {Kershner, John and Jaworski, Justin and Geyer, Thomas}, title = {Experimental study of trailing-edge bluntness noise reduction by porous plates}, series = {AIAA AVIATION 2023 Forum, 12-16 June 2023, San Diego, CA and Online}, journal = {AIAA AVIATION 2023 Forum, 12-16 June 2023, San Diego, CA and Online}, doi = {10.2514/6.2023-4284}, language = {en} } @misc{GeyerEnghardt, author = {Geyer, Thomas and Enghardt, Lars}, title = {Experimental Evaluation of the Turbulence Interaction Noise Reduction by Flat Plates with Perforated Leading Edges}, series = {AIAA AVIATION 2023 Forum, 12-16 June 2023}, journal = {AIAA AVIATION 2023 Forum, 12-16 June 2023}, doi = {10.2514/6.2023-4287}, language = {en} } @misc{KershnerGeyerJaworski, author = {Kershner, John and Geyer, Thomas and Jaworski, Justin}, title = {Setup for experimental study of porous plate acoustics and local flow features}, series = {Fortschritte der Akustik - DAGA, 49. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 49. Jahrestagung f{\"u}r Akustik}, pages = {530 -- 533}, language = {en} } @misc{LyuXuGeyeretal., author = {Lyu, Benshuai and Xu, Jiali and Geyer, Thomas and Paruchuri, Chaitanya and Ye, Qingqing and Cui, Jiahuan and Ayton, Lorna}, title = {Experimental investigation into the acoustical superiority of ogee serrations in reducing leading edge noise}, series = {Applied Acoustics}, volume = {216}, journal = {Applied Acoustics}, issn = {1872-910X}, doi = {10.1016/j.apacoust.2023.109722}, language = {en} } @misc{AbromeitRaghuramGeyeretal., author = {Abromeit, Paul and Raghuram, Priyanka and Geyer, Thomas Fritz and Enghardt, Lars}, title = {Investigation on aerodynamic noise generated by porous coated, staggered tandem cylinders}, series = {Proceedings of DAS|DAGA 2025 : 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen}, journal = {Proceedings of DAS|DAGA 2025 : 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen}, editor = {DEGA e.V.,}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, address = {Berlin}, organization = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, isbn = {978-3-939296-23-2}, doi = {10.71568/dasdaga2025.165}, pages = {521 -- 524}, abstract = {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.}, language = {en} } @misc{AbromeitGeyerEnghardt, author = {Abromeit, Paul and Geyer, Thomas and Enghardt, Lars}, title = {Aerodynamische Schallentstehung an zwei versetzt angeordneten Zylindern gleichen Durchmessers}, series = {Fortschritte der Akustik - DAGA, 50. Jahrestagung f{\"u}r Akustik}, journal = {Fortschritte der Akustik - DAGA, 50. Jahrestagung f{\"u}r Akustik}, pages = {4}, abstract = {Die komplexe Umstr{\"o}mung 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, besch{\"a}ftigen 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 auff{\"a}llige tonale Merkmale und bei bestimmten Winkeln und Abst{\"a}nden 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 h{\"o}heren Anstellwinkeln wieder zu einem Maximum. Zum besseren Verst{\"a}ndnis dieser Mechanismen wurden f{\"u}r verschiedene Anstellwinkel qualitative Str{\"o}mungssimulationen durchgef{\"u}hrt.}, language = {de} } @misc{GeyerAbromeitPruegel, author = {Geyer, Thomas Fritz and Abromeit, Paul and Pr{\"u}gel, Maximilian}, title = {Noise generation by tandem cylinders of different diameter in cross-flow}, series = {Proceedings of DAS|DAGA 2025 : 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen}, journal = {Proceedings of DAS|DAGA 2025 : 51st Annual Meeting on Acoustics, March 17-20, 2025, Copenhagen}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, address = {Berlin}, isbn = {978-3-939296-23-2}, doi = {10.71568/dasdaga2025.242}, pages = {525 -- 528}, abstract = {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.}, language = {en} } @misc{GeyerLuciusSchneideretal., author = {Geyer, Thomas and Lucius, Andreas and Schneider, Marc and Enghardt, Lars}, title = {Aerodynamic noise from circular cylinders under turbulent inflow conditions}, series = {AIAA journal}, volume = {63}, journal = {AIAA journal}, number = {8}, publisher = {AIAA}, address = {Reston, Va.}, issn = {1533-385X}, doi = {10.2514/1.J064504}, pages = {3250 -- 3260}, abstract = {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.}, language = {en} }