TY - CHAP A1 - Öngüner, Emir A1 - Dittmar, Mirko A1 - Meyer, P. A1 - Zanoun, El-Sayed A1 - Egbers, Christoph T1 - Wall-bounded turbulent Structures in pipe flow based on streamwise and cross-sectional PIV at Re=10^4-10^5 T2 - 11th European Fluid Mechanics Conference, Sept. 12-16, 2016, Sevilla, Spain Y1 - 2016 UR - http://www.efmc11.org/download/com/com_0703_KFARSY.pdf ER - TY - CHAP A1 - Zanoun, El-Sayed A1 - Egbers, Christoph A1 - Öngüner, Emir T1 - Integral Flow parapeters for evaluating the law of the wall in pipe and channel facilities T2 - 11th European Fluid Mechanics Conference, Sept. 12-16, 2016, Sevilla, Spain Y1 - 2016 UR - https://www-docs.b-tu.de/fg-aerodynamik-stroemungslehre/public/PDF/Pubs/efmc11/com_0003_VPZ7VS.pdf ER - TY - CHAP A1 - Sevlam, Kamal A1 - Öngüner, Emir A1 - Peixinho, Jorge A1 - Zanoun, El-Sayed A1 - Egbers, Christoph T1 - Wall pressure fluctuations in developing turbulent pipe flow T2 - Book of abstracts, School ISTROF 2016, Instabilities and Turbulence in Strato-Rotational Flows, July 11-13th, 2016, Le Havre Y1 - 2016 UR - https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxzY2hvb2xpc3Ryb2Z8Z3g6NDA3Y2E3ZGQ2OWIwMTdmNQ ER - TY - CHAP A1 - Öngüner, Emir A1 - Zanoun, El-Sayed A1 - Egbers, Christoph ED - Örlü, Ramis ED - Talamelli, Alessandro ED - Peinke, Joachim ED - Oberlack, Martin T1 - Streamwise Auto-Correlation Analysis in Turbulent Pipe Flow Using Particle Image Velocimetry at High Reynolds Numbers T2 - Progress in Turbulence VII, Proceedings of the iTi Conference in Turbulence 2016 Y1 - 2017 UR - https://link.springer.com/chapter/10.1007/978-3-319-57934-4_16 SN - 978-3-319-57933-7 SP - 107 EP - 112 PB - Springer CY - Cham ER - TY - CHAP A1 - Öngüner, Emir A1 - Zanoun, El-Sayed A1 - Fiorini, Tommaso A1 - Bellani, Gabriele A1 - Shahirpour, Amir A1 - Egbers, Christoph A1 - Talamelli, Alessandro ED - Örlü, Ramis ED - Talamelli, Alessandro ED - Peinke, Joachim ED - Oberlack, Martin T1 - Wavenumber Dependence of Very Large-Scale Motions in CICLoPE at 4800 ≤ Reτ ≤ 37.000 T2 - Progress in Turbulence VII, Proceedings of the iTi Conference in Turbulence 2016 Y1 - 2017 UR - https://link.springer.com/chapter/10.1007/978-3-319-57934-4_15 SN - 978-3-319-57933-7 SP - 101 EP - 106 PB - Springer CY - Cham ER - TY - CHAP A1 - Egbers, Christoph A1 - Shahirpour, Amir A1 - Öngüner, Emir A1 - Zanoun, El-Sayed T1 - Spectral Analysis of Large Scale Structures in Fully Developed Turbulent Pipe Flow T2 - 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics GAMM, March 6-10, 2017, Weimar, Germany, Book of abstracts Y1 - 2017 UR - https://www.tu-ilmenau.de/fileadmin/media/analysis/trunk/170304_BoA_GAMM_2017.pdf SP - S. 46 ER - TY - CHAP A1 - Zanoun, El-Sayed A1 - Öngüner, Emir A1 - Motuz, Vasyl A1 - Egbers, Christoph A1 - Fiorini, Tommaso A1 - Örlü, Ramis A1 - Bellani, Gabriele A1 - Talamelli, Alessandro T1 - Direct and in-direct measurement of momentum structure in ColaPipe T2 - 16th European Turbulence Conference, 21-24 August, 2017, Stockholm, Sweden Y1 - 2017 UR - http://www.delegia.com/app/data/8684/Abstract/29099/ETC16_Zanoun.pdf ER - TY - GEN A1 - Zanoun, El-Sayed A1 - Öngüner, Emir A1 - Shahirpour, Amir A1 - Merbold, Sebastian A1 - Egbers, Christoph T1 - Spectral Analysis of Large Scale Structures in Fully Developed Turbulent Pipe Flow T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2018 U6 - https://doi.org/10.1002/pamm.201710293 SN - 1617-7061 N1 - Special Issue: 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM), Weimar 2017; Editors: C. Könke, Weimar, and C. Trunk, Ilmenau VL - 17 IS - 1 SP - 647 EP - 650 ER - TY - GEN A1 - Selvam, Kamal A1 - Öngüner, Emir A1 - Peixinho, Jorge A1 - Zanoun, El-Sayed A1 - Egbers, Christoph T1 - Wall pressure in developing turbulent pipe flows T2 - Journal of Fluids Engineering Y1 - 2018 SN - 1528-901X SN - 0098-2202 VL - 140 IS - 8 ER - TY - CHAP A1 - Zanoun, El-Sayed A1 - Öngüner, Emir A1 - Egbers, Christoph A1 - Bellani, Gabriele A1 - Talamelli, Alessandro T1 - One-Dimensional Flow Spectra and Cumulative Energy from Two Pipe Facilities T2 - iTi 2018 Conference on Turbulence VIII, September 5–7, 2018, Bertinoro, Italy, Book of abstract Y1 - 2018 UR - https://www.fdy.tu-darmstadt.de/iti/author_information/submit_abstract_1/abstract_submission_1.en.jsp SP - S. 100 ER - TY - CHAP A1 - Zanoun, El-Sayed A1 - Motuz, Vasyl A1 - Egbers, Christoph A1 - Keller, J. A1 - Dörner, K. ED - Kähler, Christian J. ED - Hain, Rainer ED - Scharnowski, Sven ED - Fuchs, Thomas T1 - Stereoscopic-PIV and Hot Wire Measurements in Pipe Flow at Relatively High T2 - Proceedings of the 5th International Conference on Experimental Fluid Mechanics, Munich 2018 Y1 - 2018 SN - 978-3-943207-32-3 U6 - https://doi.org/10.18726/2018_2 SP - 877 EP - 882 PB - Institute of Fluid Mechanics and Aerodynamics, Universität der Bundeswehr CY - Neubiberg ER - TY - GEN A1 - Zanoun, El-Sayed A1 - Egbers, Christoph A1 - Örli, Ramis A1 - Fiorini, Tommaso A1 - Bellani, Gabriele A1 - Talamelli, Alessandro T1 - Experimental evaluation of the mean momentum and kinetic energy balance equations in turbulent pipe flows at high Reynolds number T2 - Journal of Turbulence Y1 - 2019 U6 - https://doi.org/10.1080/14685248.2019.1628968 SN - 1468-5248 VL - 20 IS - 5 SP - 285 EP - 299 ER - TY - GEN A1 - Zanoun, El-Sayed A1 - Egbers, Christoph A1 - Dewidar, Yasser T1 - Two-Point Velocity Correlations in Fully Developed Turbulent Pipe Flow at Shear Reynolds Number of Reτ ≈ 4000 T2 - Proceedings in Applied Mathematics and Mechanics : (PAMM) Y1 - 2021 U6 - https://doi.org/10.1002/pamm.202000330 SN - 1617-7061 VL - 20 IS - 1 ER - TY - GEN A1 - Richter, Stefan A1 - Zanoun, El-Sayed A1 - Egbers, Christoph T1 - Investigation of Large Scale Motion Interaction with the Near‐Wall Turbulence T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2021 U6 - https://doi.org/10.1002/pamm.202000331 SN - 1617-7061 VL - 20 IS - 1 ER - TY - GEN A1 - Zanoun, El-Sayed A1 - Egbers, Christoph A1 - Nagib, H. M. A1 - Durst, F. A1 - Bellani, Gabriele A1 - Talamelli, Alessandro T1 - Wall friction relations in wall-bounded shear flows T2 - European Journal of Mechanics - B/Fluids Y1 - 2021 U6 - https://doi.org/10.1016/j.euromechflu.2021.03.007 SN - 1873-7390 SN - 0997-7546 VL - Vol. 89 SP - 171 EP - 179 ER - TY - GEN A1 - Richter, Stefan A1 - Zanoun, El-Sayed A1 - Peixinho, Jorge A1 - Egbers, Christoph T1 - Pipe Flow Development and Transition in CoSmaPipe Facility T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2023 U6 - https://doi.org/10.1002/pamm.202300001 SN - 1617-7061 N1 - 92nd Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM) May 2023 VL - 23 IS - 1 ER - TY - GEN A1 - Zanoun, El-Sayed A1 - Dewidar, Yasser A1 - Egbers, Christoph T1 - Reynolds number dependence of azimuthal and streamwise pipe flow structures T2 - Journal of Fluid Mechanics Y1 - 2023 U6 - https://doi.org/10.1017/jfm.2023.700 SN - 0022-1120 VL - Vol. 973 SP - 1 EP - 36 ER - TY - GEN A1 - EL-Sheikh, Mohamed A1 - EL-Batsh, Hesham M. A1 - Zanoun, El-Sayed A1 - Attia, Ali M. A. T1 - Numerical and experimental investigations of flow separation control through a linear compressor cascade T2 - Discover applied sciences N2 - Modern large-scale gas turbines are equipped with high-pressure ratio compressors to increase engine work and its overall efficiency. Flow separation and energy losses are also two interrelated phenomenon associated with changes in compressor loading level and performance. This paper examines therefore the control of flow separation using a passive-control technique. An arced divergent-convergent slot grooved from the blade pressure side to its suction side was adopted to control flow separation, reducing the losses through a linear compressor cascade. The spanwise location of the slot was selected based on CFD simulations where the corner separation was predicted. The slot height in the spanwise direction was selected to be 8% of the blade height at the end-wall side. The present work was performed experimentally and numerically at an inlet Reynolds number, Rec=ρV∞C/μ=2.98×105, covering a wide range of incidence angles from +6∘to-6∘. The experimental work was carried out using a linear cascade test section consisting of six NACA 65-009 blade profiles integrated into a low-speed wind tunnel. A five-hole pressure probe system was used to obtain main flow parameters. Numerically, four turbulence models, including Spalart–Allmaras (S–A) model, Realizable (R k-ε) model, Shear-Stress Transport (SST k-ω) model, and Reynolds Stress model (RSM) were tested to predict the velocity and pressure fields. Good agreement between the experimental measurements and the numerical results, which were obtained using the RSM turbulence model in terms of velocity profiles and total pressure downstream of blades. It was observed also that the use of the arced-slotted blades for positive incident angles was more effective in reducing the separation than the negative and zero incident angles, approaching a maximum value of 33% for 6° with enhanced blade loading reaching 17.6%. It is to be concluded that, the use of arced slotted blade improves the compressor performance specially for positive incident angles. KW - Linear compressor cascade KW - Flow separation KW - Passive flow control KW - Turbulence model KW - Slotted blade Y1 - 2024 U6 - https://doi.org/10.1007/s42452-024-05982-3 SN - 3004-9261 VL - 6 IS - 9 SP - 1 EP - 24 PB - Springer International Publishing CY - Cham ER - TY - GEN A1 - Durst, Franz A1 - Zanoun, El-Sayed T1 - Laminar pipe flow instability : a theoretical-experimental perspective T2 - Fluids N2 - This paper revisits the theoretically predicted inherent stability of fully developed laminar pipe flow, which remains unconfirmed by experimental evidence. A recently developed theory of pipe-flow stability/instability addresses the gap between experimental observations and classical theoretical predictions by accounting for a parallel secondary flow through the pipe’s roughness layer that accompanies the main stream. This secondary flow alters the near-wall velocity profile in the rough-wall region, creating an inflection point that promotes shear-driven instabilities and triggers the laminar-to-turbulent transition. A stability factor 𝑆=𝐷𝑐/𝐷 is introduced, where D is the nominal pipe diameter and 𝐷𝑐 refers to the critical pipe diameter. The pipe flow remains laminar and stable for 𝑆>1.0, and becomes unstable for 𝑆<1. Various experimental findings are theoretically derived, and the laminar-to-turbulent transition is identified at 𝑆=1.0. Particular attention is paid to the dependence of flow transition on both pipe diameter and pipe length. Rather than relying on a critical Reynolds number 𝑅𝑒𝑐, this study proposes the critical pipe diameter 𝐷𝑐 as the key parameter governing the laminar pipe flow instability, where 𝑅𝑒𝑐 refers here to the condition-dependent threshold at which laminar pipe flow becomes unstable and transition to turbulence occurs. The present analysis further suggests that instability arises only if the pipe length L exceeds a critical threshold 𝐿𝑐, that is, 𝐿>𝐿𝑐. The theoretical treatment presented provides deeper physical insights into the onset of laminar pipe flow instability including the phenomenon of reverse transition. It also distinguishes between natural and forced flow transitions, providing a refined understanding of the transition process. Finally, suggestions for future experimental work are made to further validate or challenge this new theoretical perspective on pipe flow instability. Y1 - 2025 U6 - https://doi.org/10.3390/fluids10080216 SN - 2311-5521 VL - 10 IS - 8 SP - 1 EP - 21 PB - MDPI CY - Basel ER - TY - GEN A1 - Zanoun, El-Sayed A1 - Bauer, Christian A1 - Wagner, Claus A1 - Durst, Franz A1 - Egbers, Christoph A1 - Bellani, Gabriele A1 - Talamelli, Alessandro T1 - Cross-validation of numerical and experimental data in turbulent pipe flow with new scaling correlations T2 - Journal of turbulence N2 - The dependence of turbulence statistics and wall friction on Reynolds number in fully developed turbulent pipe flow remains a fundamental subject in fluid mechanics. This paper cross-validates experimental and numerical results, focusing on the scaling of turbulence statistics at the pipe centerline and across the inner-outer flow region. Pipe flow experiments were reviewed for friction Reynolds numbers 810≤Re𝜏≤55×103, where Re𝜏=𝑢𝜏⁢𝑅/𝜈, 𝑢𝜏 is the wall friction velocity, 𝑅 the pipe radius, and 𝜈 the kinematic viscosity. Complementary DNS data for 180≤Re𝜏≤2880 provide detailed insight into near-wall turbulence. A novel friction correlation, Re𝜏=0.048Re0.923 c is introduced, predicting pipe-wall friction across a wide range of Re𝑐 with accuracy better than ±2.06%, where Re𝑐 is the Reynolds number based on the centerline streamwise mean velocity component 𝑈zc. This correlation enables reliable friction estimates from centerline single-point measurements or DNS data without requiring near-wall or streamwise pressure-gradient information and is validated by consistent agreement with both experiments and DNS. The monotonic decrease in centerline turbulence intensity ⟨𝑢′𝑧2⟩1/2/𝑈zc with increasing Re𝑐 is explained using the streamwise mean momentum equation. Finally, azimuthal spatial filtering of DNS data highlights the limitations of hot-wire resolution near the wall. For Re𝜏≥2880, higher-order experimental statistics agree well with DNS for 𝑦+≥30 and into the logarithmic region, with both datasets equally well described by logarithmic or power-law correlations, while near-wall discrepancies remain due to resolution limits. KW - Pipe flow KW - Turbulence statistics KW - DNS KW - Experiments Y1 - 2025 U6 - https://doi.org/10.1080/14685248.2025.2560314 SP - 1 EP - 22 PB - Taylor & Francis CY - London ER -