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Golliard, Thomas
Publications (3 of 3) Show all publications
Golliard, T. & Mihaescu, M. (2024). Computational Aeroacoustics for a Cold, Non-Ideally Expanded Aerospike Nozzle. Journal of turbomachinery, 146(2), Article ID 021003.
Open this publication in new window or tab >>Computational Aeroacoustics for a Cold, Non-Ideally Expanded Aerospike Nozzle
2024 (English)In: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 146, no 2, article id 021003Article in journal (Refereed) Published
Abstract [en]

In supersonic aerospace applications, aerospike nozzles have been subject of growing interest. This study sheds light on the noise components of a cold jet exhausting an aerospike nozzle. Implicit large eddy simulations (ILES) are deployed to simulate the jet at a nozzle pressure ratio (NPR)=3. For far-field acoustic computation, the Ffowcs Williams-Hawk-ings (FWH) equation is applied. A mesh sensitivity study is performed and the jet instantaneous and time-averaged flow characteristics are analyzed. The annular shock structure displays short non-attached shock-cells and longer attached shock-cells. Downstream of the aerospike, a circular shock-cell structure is formed with long shock-cells. Two-point cross-correlations of data acquired at monitoring points located along the shear layers allow to identify upstream propagating waves associated to screech. Power spectral density at monitoring points in the annular shock-cell structure allows to identify its radial oscillation modes. Furthermore, a vortex sheet model is adapted to predict the annular shock-cells length and the BBSAN central frequency. High sound pressure levels (SPL) are detected at the determined BBSAN central frequencies. Finally, high SPL are obtained at the radial oscillation frequencies for the annular shock-cell structure.

Place, publisher, year, edition, pages
ASME International, 2024
Keywords
aeroacoustics, computational fluid dynamics (CFD), nozzle, turbine aerodynamic design
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-341742 (URN)10.1115/1.4063877 (DOI)001134180600006 ()2-s2.0-85180070049 (Scopus ID)
Note

QC 20240103

Available from: 2024-01-03 Created: 2024-01-03 Last updated: 2024-02-06Bibliographically approved
Golliard, T. & Mihaescu, M. (2024). Temperature Impact on an Aerospike Nozzle Jet, a Computational Aeroacoustics Approach. In: AIAA SciTech Forum and Exposition, 2024: . Paper presented at AIAA SciTech Forum and Exposition, 2024, Orlando, United States of America, Jan 8 2024 - Jan 12 2024. American Institute of Aeronautics and Astronautics (AIAA)
Open this publication in new window or tab >>Temperature Impact on an Aerospike Nozzle Jet, a Computational Aeroacoustics Approach
2024 (English)In: AIAA SciTech Forum and Exposition, 2024, American Institute of Aeronautics and Astronautics (AIAA) , 2024Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, the flow and acoustic characteristics of an aerospike nozzle jet at a Nozzle Pressure Ratio (NPR) = 3 and three different Temperature Ratios (TR) = 1, 3, 7 are presented. Implicit Large Eddy Simulations (ILES) are deployed to simulate the flow of the aerospike nozzle. The LES calculations are completed by aeroacoustic computations based on the Ffowcs Williams-Hawkings (FWH) equation. In the supersonic jet exhausting an aerospike nozzle, two shock-cell structures are observed: an annular and a circular one. In the direct vicinity of the annular nozzle, the annular jet is non-attached and reattaches further downstream at increasing distance with increasing jet Temperature Ratio (TR). The observed shock cells in the non-attached annular jet structure are longer for TR3 and TR7 compared to TR1. The shock strength in the annular jet is increasing with increasing jet TR. In the meantime, the total number of shock cells in the circular part of the jet decreases with increasing jet TR. Pressure spectra in the near-field show the presence of a strong tonal noise at upstream angles corresponding to screech tones. Two-point cross-correlations of pressure data acquired in monitoring points located along axial lines in the circular shear layer are computed to quantify the upstream propagating waves associated to this tonal component. Power spectral density of the radial velocity at several monitoring points located at the shock cells as well as at the separation bubble, highlights the main oscillation modes of the annular shock-cell structure. Supersonic convection velocities of turbulent structures are detected with increasing jet temperature by means of two-point cross-correlation. This confirms the presence of Mach waves observed in the instantaneous snapshots. The Mach waves radiation angles are in agreement with existing models. In the far-field spectra, the highest Sound Pressure Levels (SPL) are associated to those Mach waves at angles around 140° (TR3) and 120° (TR7). High skewness and kurtosis in the pressure signals indicate crackle noise at higher jet temperatures. Additionally, the shock-cell length is used to predict the central frequency of Broadband Shock-Associated Noise (BBSAN) as a function of observation angles. The far-field spectra display mixing noise as well as BBSAN, related to the interaction between the convected vortices in the shear layers and the shock-cell structure. With increasing jet temperature, higher SPL are detected in agreement with the BBSAN central frequencies which were computed using the annular and circular shock-cell length.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics (AIAA), 2024
National Category
Fluid Mechanics and Acoustics Aerospace Engineering Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-349899 (URN)10.2514/6.2024-2100 (DOI)2-s2.0-85196819366 (Scopus ID)
Conference
AIAA SciTech Forum and Exposition, 2024, Orlando, United States of America, Jan 8 2024 - Jan 12 2024
Note

QC 20240704

ISBN 978-1-62410-711-5

Available from: 2024-07-03 Created: 2024-07-03 Last updated: 2024-07-04Bibliographically approved
Golliard, T. & Mihaescu, M. (2023). Computational Aeroacoustics for a Cold, Non-Ideally Expanded Aerospike Nozzle. In: Proceedings of ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition, GT 2023. Paper presented at ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition, GT 2023, Boston, United States of America, Jun 26 2023 - Jun 30 2023. American Society of Mechanical Engineers (ASME), Article ID v13ct33a004.
Open this publication in new window or tab >>Computational Aeroacoustics for a Cold, Non-Ideally Expanded Aerospike Nozzle
2023 (English)In: Proceedings of ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition, GT 2023, American Society of Mechanical Engineers (ASME) , 2023, article id v13ct33a004Conference paper, Published paper (Refereed)
Abstract [en]

In supersonic aerospace applications, aerospike nozzles have been subject of growing interest. These devices lead to enhanced thrust performance compared to conventional nozzles due to continuous altitude adaption and improved thrust vector control. However, supersonic non-ideally expanded jets are known to generate high levels of noise. The aeroacoustic behaviour of circular and rectangular nozzles has been largely discussed whereas data on the aeroacoustic behaviour of aerospike nozzles is scarce. For further industrial development, the identification of the noise generation mechanisms in such configurations is necessary. This study sheds light on the main noise components of a cold jet exhausting an aerospike nozzle. Implicit Large Eddy Simulations (ILES) are deployed to simulate the flow of the cold aerospike at a Nozzle Pressure Ratio (NPR) = 3. For far-field acoustic computation, the Ffowcs-Williams Hawkings (FWH) equation is applied. A mesh sensitivity study is first performed. Then, the configuration is analyzed in terms of near-field instantaneous and time-averaged flow characteristics. It is of crucial interest to characterize the features of the shock-cell structures. The annular shock structure near the aerospike bluff body displays two non-attached shock-cells of length L/Dj ∼ 0.43. The annular jet is then reattaching and this reattachment leads to longer shock-cells of length L/Dj ∼ 0.77. Downstream of the bluff body, a second expansion process takes place and leads to the emergence of a circular shock-cell structure with a first shock-cell length of L/Dj ∼ 1.20. The interaction between the vortical flow structures in the shear layers and the shocks generates Broadband Shock-Associated Noise (BBSAN). In order to enhance understanding of the noise generation mechanism for this configuration, several analyses are performed. Two-point cross-correlations of data acquired in monitoring points located along axial lines in the circular shear layers are used for quantifying the upstream propagating waves associated to a strong tonal component at a Strouhal number St = 0.51. This strong tonal component is known as screech. It is generated by a feedback mechanism between the coherent fluid flow structures propagating downstream in the jet shear layer and the upstream propagating acoustic waves generated at the same frequency by vortex-shock interactions, waves that are interacting with the nozzle lip and excite shear layer instabilities at the frequency of screech. Power spectral density of the radial velocity at monitoring points in the annular jet structure displays three main peaks at St = 0.68, St = 1.21 and St = 2.59. These frequencies correspond to the oscillation modes of the annular shock-cell structure in radial direction. Furthermore, a vortex sheet model is adapted to predict the length of the annular shock-cells. A good agreement is reached between the analytically derived shock-cell length and the simulation results. The shock-cell length is used to predict the central frequency of BBSAN as a function of observation angles. The far-field spectra show mixing noise as well as Broadband Shock-Associated Noise, related to the interaction between the convected vortices in the shear layers and the shock-cell structure. High sound pressure levels (SPL) are detected in agreement with the BBSAN central frequencies which were computed using the annular and circular shock-cell length. Finally, high SPL are obtained at the radial oscillation frequencies for the annular shock-cell structure.

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME), 2023
Keywords
acoustic analogy, aeroacoustics, aerospike nozzle, Ffowcs Williams-Hawkings, Large eddy simulation, supersonic jet noise
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-340382 (URN)10.1115/GT2023-101947 (DOI)001214818300057 ()2-s2.0-85177171478 (Scopus ID)
Conference
ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition, GT 2023, Boston, United States of America, Jun 26 2023 - Jun 30 2023
Note

Part of ISBN 9780791887103

QC 20231204

Available from: 2023-12-04 Created: 2023-12-04 Last updated: 2024-06-14Bibliographically approved
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