{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,7]],"date-time":"2026-01-07T07:58:35Z","timestamp":1767772715978,"version":"build-2065373602"},"reference-count":51,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2023,10,14]],"date-time":"2023-10-14T00:00:00Z","timestamp":1697241600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"German Federal Ministry for Economic Affairs and Climate Action and the Ministry for Science, Research and the Arts of the State of Baden-Wuerttemberg","award":["20M2237G"],"award-info":[{"award-number":["20M2237G"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>As an indispensable part of the engine manufacturer supply chain, the eco-efficiency of altitude test facility (ATF) operations must improve. Automation is a key enabler in this context since it not only increases precision and reproducibility but also allows for reducing the test time and energy consumption. A suitable controller and reliable validation are crucial to ensure the stability and appropriate response of the control system. Both aspects necessitate a thorough understanding of the control plant, expressed in a numerical model. These models have to be suitable for control system design and validation while covering asymmetric flow phenomena that occur in the pipe system and detailing the nonlinear system dynamics to a high degree of accuracy. One-dimensional network models, state-space models, highly resolving numerical models, and data-driven models are relevant applications for this task. We compare the results of state-of-the-art one-dimensional network models which mainly imply symmetric flow conditions with those of three-dimensional Reynolds-averaged-Navier\u2013Stokes (RANS) simulations which cover asymmetric flow phenomena. The findings show that the assumptions of idealized, axis-symmetric flow in the one-dimensional flow elements do not hold true for the complex flows in an altitude test facility. In a second step, we have compared the results of one-dimensional simulations with in-service measurements taken during ATF test campaigns. Deviations were observed, which become explainable based on the insights gained from the comparison with the RANS simulation. The findings reveal that the one-dimensional simulation-based approach is insufficient to adequately reflect the plant and subsequently for validation due to the observed asymmetric flow phenomena. To overcome this limitation, the application of an empirical first-order transfer function using system identification methods is proposed. Its applicability is successfully demonstrated for the exhaust gas section of the ATF. Subsequently, essential criteria for the design of a suitable control concept for the outlet condition are derived.<\/jats:p>","DOI":"10.3390\/sym15101918","type":"journal-article","created":{"date-parts":[[2023,10,14]],"date-time":"2023-10-14T14:38:42Z","timestamp":1697294322000},"page":"1918","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Asymmetric Flow Phenomena Affecting the Characterization of the Control Plant of an Altitude Test Facility for Aircraft Engines"],"prefix":"10.3390","volume":"15","author":[{"given":"Christopher","family":"Roth","sequence":"first","affiliation":[{"name":"Institute of Aircraft Propulsion Systems (ILA), University of Stuttgart, 70569 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jan","family":"Hartmann","sequence":"additional","affiliation":[{"name":"Institute of Aircraft Propulsion Systems (ILA), University of Stuttgart, 70569 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Constanze","family":"Schiewe","sequence":"additional","affiliation":[{"name":"Institute of Aircraft Propulsion Systems (ILA), University of Stuttgart, 70569 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2582-907X","authenticated-orcid":false,"given":"Stephan","family":"Staudacher","sequence":"additional","affiliation":[{"name":"Institute of Aircraft Propulsion Systems (ILA), University of Stuttgart, 70569 Stuttgart, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,10,14]]},"reference":[{"unstructured":"(2023, August 31). EASA CS-E Certification Specification for Engines. Available online: https:\/\/www.easa.europa.eu\/sites\/default\/files\/dfu\/agency-measures-docs-certification-specifications-CS-E-CS-E_Amendment-2.pdf.","key":"ref_1"},{"unstructured":"(2023, August 31). FAA AC 33-2C: General Type Certification Guidelines for Turbine Engines, Available online: https:\/\/www.faa.gov\/documentLibrary\/media\/Advisory_Circular\/AC_33-2C.pdf.","key":"ref_2"},{"unstructured":"K\u00f6cke, S. (2010). Simulation eines H\u00f6henpr\u00fcfstands zur Untersuchung der Verdichter-Pumpverh\u00fctungsregelung. [Ph.D. Thesis, University of Stuttgart].","key":"ref_3"},{"key":"ref_4","first-page":"2116","article-title":"PW4084 Engine Testing in Altitude & Sea Level Test Facilities","volume":"103","author":"Roberts","year":"1994","journal-title":"SAE Trans."},{"unstructured":"Adolf, M. (2012). More Energy Efficiency through Process Automation, ZVEI-Zentralverband Elektrotechnik und Elektronikindustrie eV. Available online: https:\/\/www.zvei.org\/fileadmin\/user_upload\/Presse_und_Medien\/Publikationen\/2013\/januar\/More_energy_efficiency_through_process_automation\/ZVEI_Energienutzung-englisch.pdf.","key":"ref_5"},{"doi-asserted-by":"crossref","unstructured":"Luppold, R.H., Meisner, R., and Norton, J.M. (1999, January 7\u201310). Design and Evaluation of an Auto-Tuning Control System for an Altitude Test Facility. Proceedings of the ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition, Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation, Indianapolis, IN, USA.","key":"ref_6","DOI":"10.1115\/99-GT-061"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2074","DOI":"10.1177\/09544100221144342","article-title":"Comparative study of hydrogen and kerosene commercial aircraft with advanced airframe and propulsion technologies for more sustainable aviation","volume":"237","author":"Karpuk","year":"2023","journal-title":"Proc. Inst. Mech. Eng. Part J. Aerosp. Eng."},{"doi-asserted-by":"crossref","unstructured":"Schiewe, C., Neuburger, N., and Staudacher, S. (2019, January 16\u201317). How Future Propulsion Systems Influence Future Component Testing: Latest Results from Stuttgart Univerity\u2019s Altitude Test Facility. Proceedings of the Global Power and Propulsion Society Technical Conference, Zurich, Switzerland.","key":"ref_8","DOI":"10.33737\/GPPS19-TC-051"},{"doi-asserted-by":"crossref","unstructured":"Richter, H. (2012). Advanced Control of Turbofan Engines, Springer Science + Business Media, LLC.","key":"ref_9","DOI":"10.1007\/978-1-4614-1171-0"},{"doi-asserted-by":"crossref","unstructured":"Bierkamp, J., K\u00f6cke, S., Staudacher, S., and Fiola, R. (2007, January 14\u201317). Influence of ATF Dynamics and Controls on Jet Engine Performance. Proceedings of the ASME Turbo Expo 2007: Power for Land, Sea, and Air. Volume 1: Turbo Expo 2007, Montreal, QC, Canada.","key":"ref_10","DOI":"10.1115\/GT2007-27586"},{"unstructured":"Schiewe, C., Staudacher, S., and Elter, M. (2019, January 22\u201327). Automation of Stuttgart Universitys multi-functional Altitude Test Facility. Proceedings of the 24th International Symposium on Air Breathing Engines (ISABE), Canberra, Australia.","key":"ref_11"},{"unstructured":"Lunze, J. (2020). Regelungstechnik 1, Springer. [12th ed.].","key":"ref_12"},{"doi-asserted-by":"crossref","unstructured":"Montgomery, P., Burdette, R., and Krupp, B. (2000, January 8\u201311). A real-time turbine engine facility model and simulation for test operations modernization and integration. Proceedings of the ASME Turbo Expo 2000: Power for Land, Sea, and Air. Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, Munich, Germany.","key":"ref_13","DOI":"10.1115\/2000-GT-0576"},{"doi-asserted-by":"crossref","unstructured":"Montgomery, P., Burdette, R., Wilhite, L., and Salita, S. (2001, January 4\u20137). Modernization of a Turbine Engine Test Facility Utilizing a Real-Time Facility Model and Simulation. Proceedings of the ASME Turbo Expo 2001: Power for Land, Sea, and Air. Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, New Orleans, LA, USA.","key":"ref_14","DOI":"10.1115\/2001-GT-0573"},{"doi-asserted-by":"crossref","unstructured":"Montgomery, P., Burdette, R., Klepper, J., and Milhoan, A. (2002, January 3\u20136). Evolution of a Turbine Engine Test Facility to Meet the Test Needs of Future Aircraft Systems. Proceedings of the ASME Turbo Expo 2002: Power for Land, Sea, and Air. Volume 1: Turbo Expo 2002, Amsterdam, The Netherlands.","key":"ref_15","DOI":"10.1115\/GT2002-30605"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1115\/1.1806452","article-title":"A Flight Simulation Vision for Aeropropulsion Altitude Ground Test Facilities","volume":"127","author":"Davis","year":"2005","journal-title":"J. Eng. Gas Turbines Power"},{"doi-asserted-by":"crossref","unstructured":"Sheeley, J., Sells, D., Bates, R., and Bates, L. (2004, January 5\u20138). Experiences with Coupling Facility Control Systems with Control Volume Facility Models. Proceedings of the 42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, USA.","key":"ref_17","DOI":"10.2514\/6.2004-932"},{"unstructured":"K\u00f6cke, S., Bierkamp, J., and Staudacher, S. (2009, January 6\u20139). Simulation des Gesamtsystems bestehend aus H\u00f6henpr\u00fcfstand und Triebwerk. Proceedings of the Deutscher Luft- und Raumfahrtkongress, Braunschweig, Germany.","key":"ref_18"},{"unstructured":"Bolk, S., and Staudacher, S. (2008, January 23\u201325). Entwurf und Identifikation eines modularen Modells des H\u00f6henpr\u00fcfstandes der Universit\u00e4t Stuttgart. Proceedings of the Deutscher Luft- und Raumfahrtkongress, Darmstadt, Germany.","key":"ref_19"},{"unstructured":"Bolk, S. (2011). Entwurf einer Mehrgr\u00f6\u00dfenregelung zur Sollwertfolge am H\u00f6henpr\u00fcfstand der Universit\u00e4t Stuttgart. [Ph.D. Thesis, University of Stuttgart].","key":"ref_20"},{"doi-asserted-by":"crossref","unstructured":"Boylston, B., and Milhoan, A. (2014, January 16\u201320). Upgrades to the Aerodynamic and Propulsion Test Unit Facility Control System and Simulator in Support of the Medium Scale Critical Components Direct Connect Test Program. Proceedings of the 19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, Atlanta, GA, USA.","key":"ref_21","DOI":"10.2514\/6.2014-2766"},{"unstructured":"Weisser, M., Bolk, S., and Staudacher, S. (2013, January 10\u201312). Hardware-In-The-Loop-Simulation of a Feedforward Multivariable Controller for the Altitude Test Facility at the University of Stuttgart. Proceedings of the Deutscher Luft- und Raumfahrtkongress, Stuttgart, Germany.","key":"ref_22"},{"doi-asserted-by":"crossref","unstructured":"Borairi, M., and Van Every, D.H. (2006, January 5\u20138). Design and Commissioning of a Multivariable Control System for a Gas Turbine Engine Test Facility. Proceedings of the 25th AIAA Aerodynamic Measurement Technology and Ground Testing Conference, San Francisco, CA, USA.","key":"ref_23","DOI":"10.2514\/6.2006-3151"},{"doi-asserted-by":"crossref","unstructured":"Miao, K., Wang, X., Zhu, M., Zhang, S., Dan, Z., Liu, J., Yang, S., Pei, X., Wang, X., and Zhang, L. (2022). A Multi-Cavity Iterative Modeling Method for the Exhaust Systems of Altitude Ground Test Facilities. Symmetry, 14.","key":"ref_24","DOI":"10.3390\/sym14071399"},{"doi-asserted-by":"crossref","unstructured":"Liu, J., Wang, X., Pei, X., Zhu, M., Zhang, L., Yang, S., and Zhang, S. (2022). Generic Modeling Method of Quasi-One-Dimensional Flow for Aeropropulsion System Test Facility. Symmetry, 14.","key":"ref_25","DOI":"10.3390\/sym14061161"},{"doi-asserted-by":"crossref","unstructured":"Pei, X., Liu, J., Wang, X., Zhu, M., Zhang, L., and Dan, Z. (2022). Quasi-One-Dimensional Flow Modeling for Flight Environment Simulation System of Altitude Ground Test Facilities. Processes, 10.","key":"ref_26","DOI":"10.3390\/pr10020377"},{"doi-asserted-by":"crossref","unstructured":"Zhu, M., and Wang, X. (2017, January 26\u201330). An Integral Type \u00b5 Synthesis Method for Temperature and Pressure Control of Flight Environment Simulation Volume. Proceedings of the ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. Volume 6: Ceramics; Controls, Diagnostics and Instrumentation; Education; Manufacturing Materials and Metallurgy, Charlotte, NC, USA.","key":"ref_27","DOI":"10.1115\/GT2017-63529"},{"doi-asserted-by":"crossref","unstructured":"Zhu, M., Wang, X., Yang, S., Chen, H., Miao, K., and Gu, N. (2019, January 17\u201321). Two Degree-of-Freedom \u00b5 Synthesis Control With Kalman Filter for Flight Environment Simulation Volume With Sensors Uncertainty. Proceedings of the ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. Volume 6: Ceramics; Controls, Diagnostics, and Instrumentation; Education; Manufacturing Materials and Metallurgy, Phoenix, AZ, USA.","key":"ref_28","DOI":"10.1115\/GT2019-90116"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"420","DOI":"10.1016\/j.cja.2020.03.017","article-title":"Modified robust optimal adaptive control for flight environment simulation system with heat transfer uncertainty","volume":"34","author":"Zhu","year":"2021","journal-title":"Chin. J. Aeronaut."},{"doi-asserted-by":"crossref","unstructured":"Zhang, S., Dan, Z., Qian, Q., Guo, Y., and Zhang, J. (2020, January 27\u201329). Nonlinear PID Pressure Control Based on Extremum Seeking. Proceedings of the 39th Chinese Control Conference (CCC), Shenyang, China.","key":"ref_30","DOI":"10.23919\/CCC50068.2020.9189051"},{"doi-asserted-by":"crossref","unstructured":"Li, J., Wang, H., Lun, Y., Qian, Q., and Wu, T. (2022, January 23\u201325). Air Exhaust Environment Simulation of Altitude Test Facility Control Based on Model-Assisted Active Disturbance Rejection Control. Proceedings of the 2022 International Conference on Autonomous Unmanned Systems (ICAUS 2022), Xi\u2019an, China.","key":"ref_31","DOI":"10.1007\/978-981-99-0479-2_93"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1204","DOI":"10.1016\/j.cja.2019.01.017","article-title":"Two freedom linear parameter varying \u00b5 synthesis control for flight environment testbed","volume":"32","author":"Zhu","year":"2019","journal-title":"Chin. J. Aeronaut."},{"unstructured":"Schiewe, C. (2023). Automatisierte Betriebspunktoptimierung des Stuttgarter H\u00f6henpr\u00fcfstandes in Hinblick auf die Energieeffizienz. [Ph.D. Thesis, University of Stuttgart].","key":"ref_33"},{"unstructured":"(2023, September 01). Flownex Homepage. Available online: https:\/\/flownex.com\/.","key":"ref_34"},{"unstructured":"(2020). Flownex Library Manual, Flownex Simulation Environment.","key":"ref_35"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1598","DOI":"10.2514\/3.12149","article-title":"Two-equation eddy-viscosity turbulence models for engineering applications","volume":"32","author":"Menter","year":"1994","journal-title":"AIAA J."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1115\/1.2910291","article-title":"Perspective: A Method for Uniform Reporting of Grid Refinement Studies","volume":"116","author":"Roache","year":"1994","journal-title":"J. Fluids Eng."},{"key":"ref_38","first-page":"7","article-title":"Experimental and Numerical Study of Blockage Effects on Flow Characteristics around a Square-Section Cylinder","volume":"13","author":"Sharify","year":"2013","journal-title":"J. Jpn. Soc. Exp. Mech."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.nucengdes.2013.04.002","article-title":"Large-eddy simulations of velocity and temperature fluctuations in hot and cold fluids mixing in a tee junction with an upstream elbow main pipe","volume":"263","author":"Lu","year":"2013","journal-title":"Nucl. Eng. Des."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1243\/095440803322328827","article-title":"Prediction of pressure drop for turbulent fluid flow in 90\u2218 bends","volume":"217","author":"Crawford","year":"2003","journal-title":"Proc. Inst. Mech. Eng. Part E: J. Process Mech. Eng."},{"unstructured":"Crawford, N. (2005). Pressure Losses at Bends and Junctions. [Ph.D. Thesis, Faculty of Engineering, School of Mechanical and Manufacturing Engineering, Queen\u2019s University].","key":"ref_41"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1243\/09544089JPME206","article-title":"A numerical investigation of the flow structures and losses for turbulent flow in 90\u2218 elbow bends","volume":"223","author":"Crawford","year":"2009","journal-title":"Proc. Inst. Mech. Eng. Part E J. Process Mech. Eng."},{"unstructured":"Weigand, B. (2002). Analytische L\u00f6sungsmethoden f\u00fcr W\u00e4rme- und Stoff\u00fcbertragungsprobleme, Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart. Manuscript for the Lecture.","key":"ref_43"},{"unstructured":"VDI-Gesellschaft Verfahrenstechnik und Chemieingenieurwesen Hrsg (2013). VDI-W\u00e4rmeatlas, Springer. [11th ed.]. Chapters C, D and N3.","key":"ref_44"},{"doi-asserted-by":"crossref","unstructured":"Baehr, H.D., and Stephan, K. (2010). W\u00e4rme- und Stoff\u00fcbertragung, Springer. [7th ed.].","key":"ref_45","DOI":"10.1007\/978-3-642-10194-6"},{"unstructured":"Incropera, F.P., DeWitt, D.P., Bergmann, T.L., and Lavine, A.S. (1996). Fundamentals of Heat and Mass Transfer, John Wiley & Sons. [6th ed.].","key":"ref_46"},{"unstructured":"Weisser, M. (2015). Grenzen des manuellen und geregelten Betriebs am H\u00f6henpr\u00fcfstand der Universit\u00e4t Stuttgart. [Ph.D. Thesis, University of Stuttgart].","key":"ref_47"},{"doi-asserted-by":"crossref","unstructured":"Bernhard, F. (2014). Handbuch der Technischen Temperaturmessung, Springer. [2nd ed.].","key":"ref_48","DOI":"10.1007\/978-3-642-24506-0"},{"doi-asserted-by":"crossref","unstructured":"Gaddis, E.S. (2013). W\u00e4rme\u00fcbertragung und Leistungsaufnahme in R\u00fchrkesseln; VDI-W\u00e4rmeatlas, Springer. [11th ed.].","key":"ref_49","DOI":"10.1007\/978-3-642-19981-3_108"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1401","DOI":"10.1016\/S0005-1098(00)00058-3","article-title":"Research on gain scheduling","volume":"36","author":"Rugh","year":"2000","journal-title":"Automatica"},{"unstructured":"Ogata, K. (2010). Modern Control Engineering, Prentice Hall. [5th ed.].","key":"ref_51"}],"container-title":["Symmetry"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-8994\/15\/10\/1918\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:06:55Z","timestamp":1760130415000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-8994\/15\/10\/1918"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,10,14]]},"references-count":51,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2023,10]]}},"alternative-id":["sym15101918"],"URL":"https:\/\/doi.org\/10.3390\/sym15101918","relation":{},"ISSN":["2073-8994"],"issn-type":[{"type":"electronic","value":"2073-8994"}],"subject":[],"published":{"date-parts":[[2023,10,14]]}}}