caa a22 4500 60619875X CHVBK 20210128100935.0 cr unu---uuuuu 210128e20150501xx s 000 0 eng 10.1007/s00348-015-1983-x doi (NATIONALLICENCE)springer-10.1007/s00348-015-1983-x Experimental assessment of spanwise-oscillating dielectric electroactive surfaces for turbulent drag reduction in an air channel flow [Elektronische Daten] [Davide Gatti, Andreas Güttler, Bettina Frohnapfel, Cameron Tropea] In the present work, wall oscillations for turbulent skin friction drag reduction are realized in an air turbulent duct flow by means of spanwise-oscillating active surfaces based on dielectric electroactive polymers. The actuator system produces spanwise wall velocity oscillations of 820mm/s semi-amplitude at its resonance frequency of 65Hz while consuming an active power of a few 100 mW. The actuators achieved a maximum integral drag reduction of 2.4%. The maximum net power saving, budget of the power benefit and cost of the control, was measured for the first time with wall oscillations. Though negative, the net power saving is order of magnitudes higher than what has been estimated in previous studies. Two new direct numerical simulations of turbulent channel flow show that the finite size of the actuator only partially explains the lower values of integral drag reduction typically achieved in laboratory experiments compared to numerical simulations. Springer-Verlag Berlin Heidelberg, 2015 Gatti Davide Department of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstraße 10, 76131, Karlsruhe, Germany aut Güttler Andreas Department of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstraße 10, 76131, Karlsruhe, Germany aut Frohnapfel Bettina Department of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstraße 10, 76131, Karlsruhe, Germany aut Tropea Cameron Center of Smart Interfaces, Technische Universtät Darmstadt, Alarich-Weiss-Straße 10, 64287, Darmstadt, Germany aut Experiments in Fluids Springer Berlin Heidelberg 56/5(2015-05-01), 1-15 0723-4864 56:5<1 2015 56 348 https://doi.org/10.1007/s00348-015-1983-x text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00348-015-1983-x text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Gatti Davide Department of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstraße 10, 76131, Karlsruhe, Germany aut NATIONALLICENCE 700 1- Güttler Andreas Department of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstraße 10, 76131, Karlsruhe, Germany aut NATIONALLICENCE 700 1- Frohnapfel Bettina Department of Fluid Mechanics, Karlsruhe Institute of Technology, Kaiserstraße 10, 76131, Karlsruhe, Germany aut NATIONALLICENCE 700 1- Tropea Cameron Center of Smart Interfaces, Technische Universtät Darmstadt, Alarich-Weiss-Straße 10, 64287, Darmstadt, Germany aut NATIONALLICENCE 773 0- Experiments in Fluids Springer Berlin Heidelberg 56/5(2015-05-01), 1-15 0723-4864 56:5<1 2015 56 348