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Laminar separation bubble bursting in a surging stream

  • The effect of high-amplitude harmonic surging on airfoil laminar separation bubbles, at small angles of attack, was investigated experimentally in a dedicated surging-flow wind tunnel. A generalized pressure coefficient was developed that accounts for local static pressure variations due to surging. This critical generalization facilitated direct comparisons between surging and quasisteady pressure coefficients, and thus unsteady effects could be distinguished from Reynolds number effects. A momentum-integral boundary layer analysis was implemented to determine movement of the bubble separation point, and movement of the transition point was extracted from experimental surface pressure coefficients. The most significant finding was that bubble bursting occurs, counterintuitively, during early imposition of the favorable temporal pressure gradient, because the favorable pressure gradient rapidly drives the bubble aft, rendering it unable to reattach. This surge-induced dynamic stallThe effect of high-amplitude harmonic surging on airfoil laminar separation bubbles, at small angles of attack, was investigated experimentally in a dedicated surging-flow wind tunnel. A generalized pressure coefficient was developed that accounts for local static pressure variations due to surging. This critical generalization facilitated direct comparisons between surging and quasisteady pressure coefficients, and thus unsteady effects could be distinguished from Reynolds number effects. A momentum-integral boundary layer analysis was implemented to determine movement of the bubble separation point, and movement of the transition point was extracted from experimental surface pressure coefficients. The most significant finding was that bubble bursting occurs, counterintuitively, during early imposition of the favorable temporal pressure gradient, because the favorable pressure gradient rapidly drives the bubble aft, rendering it unable to reattach. This surge-induced dynamic stall mechanism resulted in large lift and form-drag coefficient oscillations. Furthermore, failure to implement the generalized pressure coefficient definition resulted in temporal form-drag coefficient errors of up to 400 counts.zeige mehrzeige weniger

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Metadaten
Autor*innen:D. GreenblattORCiD, H. Müller-Vahl, Christoph StrangfeldORCiD
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Laminar separation bubble bursting in a surging stream
Jahr der Erstveröffentlichung:2023
Organisationseinheit der BAM:8 Zerstörungsfreie Prüfung
8 Zerstörungsfreie Prüfung / 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen
Verlag:American Physical Society
Jahrgang/Band:8
Ausgabe/Heft:1
Aufsatznummer:L012102
Erste Seite:1
Letzte Seite:11
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Angewandte Physik
Freie Schlagwörter:Aerodynamics; Boundary layer receptivity, stability & separation; Boundary layers
Themenfelder/Aktivitätsfelder der BAM:Energie
DOI:10.1103/PhysRevFluids.8.L012102
ISSN:2469-990X
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:23.01.2023
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:03.05.2023
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