{{short description|German aerospace engineer and professor}} {{Infobox person | name = Markus Raffel | image = Markus Raffel, 2015.jpg | alt = | caption = Markus Raffel in 2017 | birth_name = | birth_date = {{birth year and age|1962}} | birth_place = Göttingen, West Germany<ref name="Helmholtz" /> | death_date = | death_place = | other_names = | education = Leibniz University Hannover (Dr.-Ing.), Clausthal University of Technology (Dr.-Ing. habil.) | occupation = mechanical engineer and professor of aerodynamics | years_active = | known_for = experimental fluid mechanics, flights in authentic replicas of Otto Lilienthal gliders | notable_works = | awards = Helmholtz Prize (1996),<ref name="Helmholtz" /> Howard Hughes Award (2004), Otto Lilienthal Research Award (2017), Leonardo da Vinci Award (2023)<ref name="arc" /> | spouse = | children = | website = }} '''Markus Raffel''' (born 1962)<ref name="Helmholtz" /> is a German aerospace engineer and professor of aerodynamics at Leibniz University Hannover. He is also the head of the Helicopters Department at the German Aerospace Center (DLR) in Göttingen,<ref name="Nordkurier">{{Cite web |author=Matthias Diekhoff |url=https://www.nordkurier.de/regional/anklam/neue-lilienthal-biografie-reicht-bis-in-die-gegenwart-1127181 |title=Neue Lilienthal-Biografie reicht bis in die Gegenwart |work=Nordkurier |date=2022-07-20 |language=de |access-date=2025-08-20}}</ref> where he conducts research in flow visualization,<ref>{{Cite news |author=Markus Raffel |title=Background-oriented schlieren (BOS) techniques |work=Experiments in Fluids |volume=56 |number=3 |date=2015-03-06 |ISSN=1432-1114 |DOI=10.1007/s00348-015-1927-5 |pages=60 |url=https://doi.org/10.1007/s00348-015-1927-5 |access-date=2025-08-20}}</ref> rotorcraft aerodynamics,<ref>{{Cite news |author1=Alexander J. Heintz |author2=Clemens Schwarz |author3=Christian Wolf |author4=Markus Raffel |title=Influence of Configurational Parameters on the Vortex System of a Rotor in Hover |work=AIAA SCITECH 2024 Forum |publisher=American Institute of Aeronautics and Astronautics |date=2024-01-04 |volume=AIAA SciTech Forum |DOI=10.2514/6.2024-0896 |url=https://arc.aiaa.org/doi/10.2514/6.2024-0896 |access-date=2025-09-08}}</ref> and experimental fluid mechanics.<ref>{{Cite web |author1=Agis Spentzos |author2=G. Barakos |author3=K. Badcock |author4=B. Richards |author5=P. Wernert |author6=Scott Schreck |author7=Markus Raffel |url=https://scholar.google.com/citations?view_op=view_citation&hl=de&user=ZRNYRjsAAAAJ&citation_for_view=ZRNYRjsAAAAJ:UeHWp8X0CEIC |title=Investigation of three-dimensional dynamic stall using computational fluid dynamics |work=Google Scholar |access-date=2025-09-08}}</ref>
== Life and career == Raffel studied mechanical engineering at the Clausthal University of Technology and at the Karlsruhe Institute of Technology until 1990. He received his doctoral degree (Dr.-Ing.) in engineering from the Leibniz University Hannover in 1993, and completed his habilitation in fluid mechanics at Clausthal University in 2001.<ref name="Helmholtz" />
Raffel has worked at the German Aerospace Center (DLR) since 1991,<ref name="Helmholtz" /> primarily at the Institute of Aerodynamics and Flow Technology in Göttingen. He serves as head of the Helicopters Department at the same institute.<ref>{{Cite web |url=https://www.hna.de/lokales/goettingen/goettingen-ort28741/krach-wird-sichtbar-viel-laerm-um-tanzenden-helikopter-92001723.html |title=DLR-Forscher machen Krach sichtbar: Viel Lärm um "tanzenden" Helikopter |work=Hessische/Niedersächsische Allgemeine |date=2022-12-30 |language=de |access-date=2025-08-20}}</ref><ref>{{Cite news |author=Dirk Eidemüller |title=Kompakt |work=Die Welt |date=2011-04-08 |pages=22}}</ref> Since 2007, he has been a full professor of aerodynamics at Leibniz University Hannover, a position jointly held with DLR.<ref name="Nordkurier" /><ref name="Helmholtz" />
Raffel has collaborated with national and international institutions on various research initiatives related to rotorcraft aerodynamics, transonic wind tunnel testing,<ref>{{Cite news |author1=Hughes Richard |author2=Wolfgang Geissler |author3=Markus Raffel |title=Simultaneous density and velocity measurement for rotorcraft research in a transonic wind tunnel |work=CD: 27th European Rotorcraft -Forum |place=Moscow |date=2001 |pages=29.1–29.10 |url=https://elib.dlr.de/13813/ |access-date=2025-08-20}}</ref> and optical flow measurement technologies.<ref>{{Cite web |author=Markus Raffel |title=Optical Measurements of Helicopter Rotor Flows |url=https://elib.dlr.de/121024/ |publisher=DLR |date=June 2018 |language=en |access-date=2025-08-20}}</ref> He is lead author of a number of books, including the widely distributed 2018 textbook ''Particle Image Velocimetry: A Practical Guide''<ref>{{cite web |date=2025-05-14 |title=Aerodynamic research – Examples from present and past (seminar series at UCSD, May 2025) |url=https://maeweb.ucsd.edu/seminar/2025/aerodynamic-research-examples-present-and-past |access-date=2025-08-20 |website=UCSD |publisher=University of California, San Diego}}</ref> and the 2022 ''The Flying Man: Otto Lilienthal—History, Flights and Photographs''.<ref>{{Cite web |author1=Markus Raffel |author2=Bernd Lukasch |title=The Flying Man. Otto Lilienthal – History, Flights and Photographs |publisher=Springer Verlag |date=August 2022 |ISBN=978-3-030-95032-3 |url=https://link.springer.com/content/pdf/10.1007/978-3-030-95033-0.pdf |access-date=2025-08-21}}</ref>
== Research and work == Raffel works in flow diagnostics, including particle image velocimetry (PIV),<ref>{{Cite news |author1=Markus Raffel |author2=Christian Willert |author3=Fulvio Scarano |author4=Christian J. Kähler |author5=Steven T. Wereley |author6=Jürgen Kompenhans |title=Particle Image Velocimetry – A Practical Guide (3rd Edition) |volume=1 |publisher=Springer Verlag |date=April 2018 |ISBN=978-3-319-68851-0 |url=https://link.springer.com/book/10.1007%2F978-3-319-68852-7#about |access-date=2025-08-20}}</ref> background-oriented schlieren (BOS),<ref>{{Cite news |author=Markus Raffel |title=Background-oriented schlieren (BOS) techniques |work =Experiments in Fluids |volume=56 |number=3 |date=2015 |ISSN=0723-4864 |pages=1–17 |url=http://link.springer.com/article/10.1007%2Fs00348-015-1927-5 |access-date=2025-08-20}}</ref> and differential infrared thermography (DIT).<ref>{{Cite journal |author1=Markus Raffel |author2=Christoph B. Merz |title=Differential Infrared Thermography for Unsteady Boundary-Layer Transition Measurements |journal=AIAA Journal |volume=52 |issue=9 |pages=2065–2073 |date=September 2014 |doi=10.2514/1.J053235 |url=https://arc.aiaa.org/doi/10.2514/1.J053235 |language=en |access-date=2025-08-20|url-access=subscription }}</ref> As part of the DLR and together with NASA, he researched ways to reduce helicopter noise.<ref>{{Cite news |author=John McHale |title=Rotor noise reduction methods being investigated by DLR and NASA engineers |work=Military & Aerospace Electronics |date=2011-04-13 |url=https://www.militaryaerospace.com/commercial-aerospace/article/14225421/rotor-noise-reduction-methods-being-investigated-by-dlr-and-nasa-engineers |language=en |access-date=2025-08-20}}</ref>
Raffel has led research programs exploring the aerodynamics and flight characteristics of historical Otto Lilienthal glider replicas. He and his team successfully constructed replicas of flight pioneer Otto Lilienthal's 1890s gliders standard soaring apparatus (Normalsegelapparat), his large bi-plane (Großer Doppeldecker), and his experimental monoplane (Experimentiergerät).<ref>{{Cite web |author1=Markus Raffel |author2=Felix Wienke |author3=Andreas Dillmann |url=https://arc.aiaa.org/doi/pdf/10.2514/1.C035399 |title=Flight-Testing Stability and Controllability of Otto Lilienthal's Monoplane Design from 1893 |work=Journal of Aircraft |date=2019 |format=PDF |language=en |access-date=2025-09-09}}</ref><ref>{{Cite news |author1=Markus Raffel |author2=Felix Wienke |author3=Andreas Dillmann |title=Flying Qualities of Otto Lilienthal's Large Biplane |work=Journal of Aircraft |volume=58 |number=2 |date=March 2021 |ISSN=0021-8669 |DOI=10.2514/1.C036022 |pages=413–419 |url=https://arc.aiaa.org/doi/10.2514/1.C036022 |access-date=2025-09-09}}</ref><ref>{{Cite news |author1=Markus Raffel |author2=Felix Wienke |author3=Clemens Schwarz |author4=Andreas Dillmann |title=Flight Controls of Otto Lilienthal‘s Experimental Monoplane from 1895 |work=Journal of Aircraft |volume=59 |number=6 |date=November 2022 |ISSN=0021-8669 |DOI=10.2514/1.C037047 |pages=1616–1625 |url=https://arc.aiaa.org/doi/10.2514/1.C037047 |access-date=2025-09-09}}</ref> Since 2018<ref>{{Cite web |author=Bärbel Hilbig |work=Hannoversche Allgemeine Zeitung |url=https://www.haz.de/lokales/hannover/professor-aus-hannover-fliegt-wie-otto-lilienthal-H4ZP6KH5VJA43JEJTYVSDV466U.html |title=Leibniz-Universität Hannover: Professor fliegt wie Otto Lilienthal |date=2018-08-25 |language=de |access-date=2025-08-20}}</ref> and together with the Otto Lilienthal Museum in Anklam,<ref>{{Cite web |url=https://www.dlr.de/de/aktuelles/nachrichten/2019/03/20190918_dlr-mitarbeiter-gelingt-flug-mit-nachbau-von-lilienthal |title=DLR – Flug mit Nachbau von Otto Lilienthal |work=German Aerospace Center |date=2019-09-18 |language=de |access-date=2025-09-08}}</ref> Raffel himself has conducted several flights with the gliders. The goal was to confirm the flight performance and potential static stability of Lilienthal's gliders, the efficacy of Otto Lilienthal's control surfaces and the wing warping mechanism.<ref>{{Cite web |author=Joachim Wilisch |url=https://www.maz-online.de/lokales/havelland/stoelln-markus-raffel-und-sein-erstaunlicher-lilienthal-stunt-25CTLH6DGZFSNKNF5DIG65UFEI.html |title=Stölln: Markus Raffel und sein erstaunlicher Lilienthal-Stunt |date=2025-08-15 |work=Märkische Allgemeine |language=de |access-date=2025-08-20}}</ref>
During his employment at DLR, Raffel worked on a number of topics during research stays at international research establishments and contributed to the advancement of optical flow measurement techniques. At the California Institute of Technology (Caltech), he collaborated on dual-plane PIV, enabling three-dimensional analysis of turbulent flows.<ref>{{Cite web |author1=M. Raffel |author2=J. Westerweel |author3=C. Willert |author4=M. Gharib |author5=J. Kompenhans |title=Analytical and experimental investigations of dual-plane PIV |language=en |date=1995 |url=https://authors.library.caltech.edu/records/7sxy7-w9420 |work=Optical Techniques in Fluid, Thermal, and Combustion Flow |access-date=2025-09-09}}</ref> He worked on background-oriented schlieren methods (BOS) for large-scale visualization of complex flow fields at ETH Zurich.<ref>{{Cite journal |author1=Markus Raffel |title=Background-oriented schlieren (BOS) techniques |journal=Experiments in Fluids |issue=3 |volume=56 |pages=60 |date=2015 |doi=10.1007/s00348-015-1927-5|doi-access=free }}</ref> At the Aix-Marseille University, he investigated micro-PIV techniques to study flows at the microscale.<ref>{{Cite journal |author1=Markus Raffel |author2=Didier Favier |author3=Eric Berton |author4=Christophe Rondot |author5=Michel Nsimba |author6=Wolfgang Geissler |title=Micro-PIV and ELDV wind tunnel investigations of the laminar separation bubble above a helicopter blade tip |journal=Measurement Science and Technology |volume=17 |issue=7 |pages=1652–1660 |date=2006 |doi=10.1088/0957-0233/17/7/003 |url=https://iopscience.iop.org/article/10.1088/0957-0233/17/7/003 |language=en |access-date=2025-09-09|url-access=subscription }}</ref> His experimental work also extended to flight testing Otto Lilienthal's gliders at Caltech, combining historical flight reconstruction with aerodynamic analysis.<ref>{{Cite journal |author1=Markus Raffel |author2=Felix Wienke |author3=Andreas Dillmann |title=Flight-Testing Stability and Controllability of Otto Lilienthal's Monoplane Design from 1893 |journal=Journal of Aircraft |volume=56 |issue=6 |pages=2298–2305 |date=2019 |doi=10.2514/1.C035399 |url=https://arc.aiaa.org/doi/10.2514/1.C035399 |language=en |access-date=2025-09-09|url-access=subscription }}</ref> Further collaborations at the University of Alberta focused on PIV wind tunnel seeding strategies,<ref>{{Cite journal |author1=Bradley Gibeau |author2=Drew Gingras |author3=Jan Raffel |author4=Markus Raffel |author5=Sina Ghaemi |title=Effect of internal geometry and orientation on the performance of a helium-filled soap bubble nozzle |journal=13th International Symposium on Particle Image Velocimetry – ISPIV 2019 |place=Munich, Germany |date=July 22–24, 2019 |url=https://elib.dlr.de/144211/ |publisher=DLR |language=en |access-date=2025-09-09}}</ref> while subsequent work at NASA Ames included stereoscopic PIV recordings of helicopter rotor wakes in large-scale facilities.<ref>{{Cite journal |author1=Markus Raffel |author2=André Bauknecht |author3=Manikandan Ramasamy |author4=Gloria K. Yamauchi |author5=James T. Heineck |author6=Luther N. Jenkins |title=Contributions of Particle Image Velocimetry to Helicopter Aerodynamics |journal=AIAA Journal |volume=55 |issue=7 |pages=2261–2275 |date=June 2017 |doi=10.2514/1.J055571 |url=https://arc.aiaa.org/doi/10.2514/1.J055571 |language=en |access-date=2025-09-09|pmc=7839999 }}</ref> According to Google Scholar, Raffel has authored or co-authored over 400 publications, with more than 17,000 citations including 16 patents as of 2025.<ref>{{cite web |title=Markus Raffel – Google Scholar Profile |url=https://scholar.google.com/citations?hl=de&user=ZRNYRjsAAAAJ |access-date=2025-08-20 |work=Google Scholar}}</ref><ref>{{Cite web |url=https://patents.google.com/?inventor=Markus+Raffel&oq=Markus+Raffel |title=Markus Raffel |work=Google Patents |language=en |access-date=2025-09-23}}</ref>
== Honors and recognition (selection) == * 1996: Helmholtz Prize for work on measurement techniques<ref name="Helmholtz">{{cite web |title=Helmholtz-Preis – Preisträger 1996 |url=https://www.helmholtz-fonds.de/helmholtz-prize/helmholtz-prizewinners/awarding-ceremony/news/preistraeger-1996-schnelle-dreidimensionale-stroemungsmessung/?L=1&tx_news_pi1%5Bcontroller%5D=News&tx_news_pi1%5Baction%5D=detail&cHash=d7d31d4745c23024b1b540ee2f8fc0e9 |work=Helmholtz-Fonds e. V. (PTB) |language=en |access-date=2025-08-20}}</ref> * 1998: DLR Science Award * 2004: Howard Hughes Award from the American Helicopter Society<ref name="arc">{{Cite web |url=https://arc.aiaa.org/doi/pdf/10.2514/1.C035399 |title=Flight-Testing Stability and Controllability of Otto Lilienthal’s Monoplane Design from 1893 |work=Journal of Aircraft |date=2019 |format=PDF |language=en |access-date=2025-08-20}}</ref> * 2005: Post Rouge of the French National Center for Scientific Research<ref>{{Cite web |url=https://vtol.org/awards-and-contests/vertical-flight-society-award-winners?awardID=5 |title=VFS: Vertical Flight Society Award Winners |language=en |access-date=2025-09-23}}</ref> * 2017: Otto Lilienthal Research Award from DLR<ref name="arc" /> * 2023: Leonardo da Vinci Award from the International Society on Flow Visualization<ref>{{Cite web |url=https://www.isfv20.org/home/highlights |title=20th International Symposium on Flow Visualization ISFV-20: Highlights |work=International Symposium on Flow Visualization |language=en |access-date=2025-09-08 }}</ref> * 2024: Lilienthal Prize by the town of Anklam<ref>{{Cite web |author=Anne-Marie Pankratz |url=https://www.nordkurier.de/regional/anklam/lilienthal-preis-an-flugpionier-der-heutigen-zeit-in-anklam-verliehen-2964473 |title=Lilienthal-Preis an Flugpionier der heutigen Zeit in Anklam verliehen |work=Nordkurier |date=2024-10-14 |language=de |access-date=2025-09-09}}</ref> * 2024: STAB-Prize for research and development in the field of fluid mechanics<ref>{{Cite web |url=https://www.dlr.de/de/as/aktuelles/veranstaltungen/stab/stab-preis/verleihung-des-stab-preis-2024 |title=Verleihung STAB-Preis 2024 |work=German Aerospace Center |language=de |access-date=2025-09-23}}</ref>
Raffel was named an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA) in 2025.<ref>{{Cite web |url=https://aiaa.org/2024/09/23/aiaa-announces-its-class-of-2025-associate-fellows/ |title=AIAA Announces its Class of 2025 Associate Fellows |work=AIAA - Shaping the future of aerospace |date=2024-09-23 |language=en |access-date=2025-09-08}}</ref>
== Selected works == * Raffel, M., Willert, C., Wereley, S., & Kompenhans, J., Scarano F., Kähler C. J. (3rd edition 2018). ''Particle Image Velocimetry: A Practical Guide''. Springer. {{ISBN|9783319688510}} * Raffel, M., Lukasch, B. (2022): ''The Flying Man: Otto Lilienthal—History, Flights and Photographs''. Springer. {{ISBN|9783030950323}}
== References == <references />
== External links == * [https://www.epv.uni-hannover.de/en/staff-search/staff-member-details/person/prof-dr-markus-raffel Profile at Leibniz University Hannover] * [https://www.dlr.de/en/as/about-us/departments/helicopters Profile at the Helicopters Department of the German Aerospace Center] * Paul Glenshaw: [https://www.smithsonianmag.com/air-space-magazine/more-century-later-lilienthal-and-wright-gliders-fly-together-first-time-kitty-hawk-180973882/ ''More Than a Century Later, Lilienthal and Wright Gliders Fly Together for the First Time at Kitty Hawk''], ''Smithsonian'', 2020. * [https://scholar.google.com/citations?user=ZRNYRjsAAAAJ&hl=de Markus Raffel] at Google Scholar
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{{DEFAULTSORT:Raffel, Markus}} Category:1962 births Category:German aerospace engineers Category:German engineers Category:Living people