Bauer, Andreas ; Bopp, Maximilian ; Jakirlic, Suad ; Tropea, Cameron ; Krafft, Axel Joachim ; Shokina, Nina ; Hennig, Jürgen (2024)
Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions.
In: Experiments in Fluids : Experimental Methods and their Applications to Fluid Flow, 2020, 61 (2)
doi: 10.26083/tuprints-00023899
Artikel, Zweitveröffentlichung, Verlagsversion
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Kurzbeschreibung (Abstract)
In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow conditions is examined with magnetic resonance velocimetry (MRV), laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD). The influence of flow phenomena on the wall shear stress (WSS) is examined. It is seen that a strong vortex ring develops during systole at the proximal end of the aneurysm and subsequently travels downstream and decays. The vortex formation plays a major role in the temporal and spatial distribution of the WSS, which is analyzed in detail. A peak of the WSS is observed for a very limited time and in a very localized region where the vortex ring initially develops. The intrinsic temporal averaging during the acquisition of the MRV data is found to significantly decrease this peak. CFD and LDV results, which are averaged in the same manner, show a similar behavior. This indicates that besides the spatial resolution, the temporal resolution is a crucial factor, which needs to be considered especially in flows where vortex rings are observed. Results from LDV and CFD show excellent agreement for the velocity field obtained by MRV. While the flow is found to be laminar in the undilated diameter, results show laminar–turbulent transitional behavior for specific phases of the cycle within the aneurysm bulk. Although MRV is not capable of measuring instantaneous velocity fluctuations, we show that the periodic increase in turbulence intensity can be observed from image artifacts in the MRV data. These artifacts increase the velocity uncertainty, which correlates well with the velocity fluctuations measured with LDV. Although the flow encounters laminar and transitional conditions as well as multiple vortices and stagnation and reattachment points, the improved instability-sensitive Reynolds stress model, which is used for the numerical simulations of this work, shows very good agreement with the measurements. Significant effort has been expended by numerous research groups in recent years in improving the estimation of WSS from MRV data. However, an assessment of these various post-processing methods is only possible if the true values of the WSS are known. The present study is therefore aimed at providing such ground truth WSS values as well as the corresponding MRV data, allowing also other research groups to validate their WSS estimation methods using the experimental data set presented in this work.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2024 |
| Autor(en): | Bauer, Andreas ; Bopp, Maximilian ; Jakirlic, Suad ; Tropea, Cameron ; Krafft, Axel Joachim ; Shokina, Nina ; Hennig, Jürgen |
| Art des Eintrags: | Zweitveröffentlichung |
| Titel: | Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions |
| Sprache: | Englisch |
| Publikationsjahr: | 23 April 2024 |
| Ort: | Darmstadt |
| Publikationsdatum der Erstveröffentlichung: | Februar 2020 |
| Ort der Erstveröffentlichung: | Berlin ; Heidelberg |
| Verlag: | Springer |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Experiments in Fluids : Experimental Methods and their Applications to Fluid Flow |
| Jahrgang/Volume einer Zeitschrift: | 61 |
| (Heft-)Nummer: | 2 |
| Kollation: | 16 Seiten |
| DOI: | 10.26083/tuprints-00023899 |
| URL / URN: | https://tuprints.ulb.tu-darmstadt.de/23899 |
| Zugehörige Links: | |
| Herkunft: | Zweitveröffentlichung DeepGreen |
| Kurzbeschreibung (Abstract): | In this study, the flow through a generic abdominal aneurysm under realistic pulsating flow conditions is examined with magnetic resonance velocimetry (MRV), laser Doppler velocimetry (LDV) and computational fluid dynamics (CFD). The influence of flow phenomena on the wall shear stress (WSS) is examined. It is seen that a strong vortex ring develops during systole at the proximal end of the aneurysm and subsequently travels downstream and decays. The vortex formation plays a major role in the temporal and spatial distribution of the WSS, which is analyzed in detail. A peak of the WSS is observed for a very limited time and in a very localized region where the vortex ring initially develops. The intrinsic temporal averaging during the acquisition of the MRV data is found to significantly decrease this peak. CFD and LDV results, which are averaged in the same manner, show a similar behavior. This indicates that besides the spatial resolution, the temporal resolution is a crucial factor, which needs to be considered especially in flows where vortex rings are observed. Results from LDV and CFD show excellent agreement for the velocity field obtained by MRV. While the flow is found to be laminar in the undilated diameter, results show laminar–turbulent transitional behavior for specific phases of the cycle within the aneurysm bulk. Although MRV is not capable of measuring instantaneous velocity fluctuations, we show that the periodic increase in turbulence intensity can be observed from image artifacts in the MRV data. These artifacts increase the velocity uncertainty, which correlates well with the velocity fluctuations measured with LDV. Although the flow encounters laminar and transitional conditions as well as multiple vortices and stagnation and reattachment points, the improved instability-sensitive Reynolds stress model, which is used for the numerical simulations of this work, shows very good agreement with the measurements. Significant effort has been expended by numerous research groups in recent years in improving the estimation of WSS from MRV data. However, an assessment of these various post-processing methods is only possible if the true values of the WSS are known. The present study is therefore aimed at providing such ground truth WSS values as well as the corresponding MRV data, allowing also other research groups to validate their WSS estimation methods using the experimental data set presented in this work. |
| Freie Schlagworte: | Engineering Fluid Dynamics, Fluid- and Aerodynamics, Engineering Thermodynamics, Heat and Mass Transfer |
| ID-Nummer: | Artikel-ID: 59 |
| Status: | Verlagsversion |
| URN: | urn:nbn:de:tuda-tuprints-238999 |
| Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau |
| Fachbereich(e)/-gebiet(e): | 16 Fachbereich Maschinenbau 16 Fachbereich Maschinenbau > Fachgebiet Strömungslehre und Aerodynamik (SLA) |
| Hinterlegungsdatum: | 23 Apr 2024 12:52 |
| Letzte Änderung: | 24 Apr 2024 10:06 |
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| Suche nach Titel in: | TUfind oder in Google |
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- Analysis of the wall shear stress in a generic aneurysm under pulsating and transitional flow conditions. (deposited 23 Apr 2024 12:52) [Gegenwärtig angezeigt]
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