This paper reports multi-point dynamic pressure fluctuation measurements made beneath a high-Reynoldsnumber turbulent boundary layer (TBL) with wall-injection of air or polymer additives for the purpose of skin-friction drag reduction. Two independent experiments were conducted in the U.S. Navy's Large Cavitation Channel (LCC) on a 12.9 m long, 3.05 m wide hydro-dynamically smooth (k(+) < 1) flat plate at free-stream speeds from 6.5 to 20.0 m/s. The first, a bubble drag reduction experiment (BDR), involved injecting gas at flow rates ranging from 100 to 800 CFM (17.8 to 142.5 liter/s per meter of injector span) from one of two injectors located 1.32 and 9.78 m from the model leading edge. The second, a polymer drag reduction experiment (PDR), involved injecting polymer from a single slot injector, 1.32 m from the leading edge, at flow-rates ranging from 6 to 30 GPM (0.14 to 0.71 liter/s per meter of injector span). Dynamic pressure measurements were made with 16 flush-mounted transducers in 'L'-shaped arrays located 10.7 and 9.8 m (70 x 106 < Rex < 210 x 106) from the leading edge for the BDR and PDR experiments, respectively. Measurements show modifications in the spectra, stream-wise coherence, and convection velocity of the pressure fluctuations due to the presence of gas or polymer in the near-wall region of the TBL. At the dynamic pressure measurement locations the maximum skin-friction drag reduction approached 100 % for the BDR experiment and 63 % for the PDR experiment.
High-Reynolds-number turbulent-boundary-layer surface pressure fluctuations with bubble or polymer additives
Oberflächen-Druckschwankungen in turbulenten Blasen- oder Polymer-Additiv-Grenzschichten mit großer Reynolds-Zahl
2005
10 Seiten, 19 Bilder, 3 Tabellen, 14 Quellen
Conference paper
English
Strömungsmechanik , Grenzschichtströmung , Reynolds-Zahl , turbulente Strömung , Strömungswiderstand , Reibungswiderstand , Strömungsgeschwindigkeit , Gasblase , Druckmessung , Strömungsmessung , Hydrodynamik , experimentelle Untersuchung , Wasserkanal , Viskosität , dynamischer Druck , Versuchsaufbau , Schiffbau
STRUCTURE OF HIGH REYNOLDS NUMBER ADVERSE PRESSURE GRADIENT TURBULENT BOUNDARY LAYER
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