TY - JOUR
T1 - Characteristics of low-speed streaks and vortex structures in drag-reduced turbulent channel flow investigated by stereoscopic PIV
AU - Li, Feng Chen
AU - Segawa, Takehiko
AU - Kawaguchi, Yasuo
AU - Hishida, Koichi
PY - 2004/12/1
Y1 - 2004/12/1
N2 - In the present study, we employed stereoscopic particle image velocimetry (SPIV) to investigate the characteristics of turbulence structures in a drag-reduced turbulent channel flow with addition of surfactant. The tested drag-reducing fluid was a CTAC (cetyltrimethyl ammonium chloride)/NaSal/Water system maintained at 25°C, having a 30-ppm concentration of CTAC. SPIV measurement was performed for a water flow (Re = 1.1×105) and a CTAC solution flow (Re = 1.5×105 with 54% drag reduction) in both the streamwise-spanwise and wall-normal-spanwise planes, respectively. A series of wall-normal vortex cores were found to align with the low-speed streaks with opposite vorticity signals at both sides of the streaks and with the vorticity decreased averagely by about one order in CTAC solution flow compared with water flow; the spanwise spacing between the low-speed streaks in the solution flow is increased by about 42%. The streamwise vorticity of the vortex cores appearing in the wall-normal-spanwise plane was also decreased by the use of additives.
AB - In the present study, we employed stereoscopic particle image velocimetry (SPIV) to investigate the characteristics of turbulence structures in a drag-reduced turbulent channel flow with addition of surfactant. The tested drag-reducing fluid was a CTAC (cetyltrimethyl ammonium chloride)/NaSal/Water system maintained at 25°C, having a 30-ppm concentration of CTAC. SPIV measurement was performed for a water flow (Re = 1.1×105) and a CTAC solution flow (Re = 1.5×105 with 54% drag reduction) in both the streamwise-spanwise and wall-normal-spanwise planes, respectively. A series of wall-normal vortex cores were found to align with the low-speed streaks with opposite vorticity signals at both sides of the streaks and with the vorticity decreased averagely by about one order in CTAC solution flow compared with water flow; the spanwise spacing between the low-speed streaks in the solution flow is increased by about 42%. The streamwise vorticity of the vortex cores appearing in the wall-normal-spanwise plane was also decreased by the use of additives.
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U2 - 10.1115/IMECE2004-61023
DO - 10.1115/IMECE2004-61023
M3 - Conference article
AN - SCOPUS:21444443180
VL - 260
SP - 855
EP - 862
JO - American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED
JF - American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED
SN - 0888-8116
M1 - IMECE2004-61023
T2 - 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE 2004
Y2 - 13 November 2004 through 19 November 2004
ER -