SECONDARY FLOW VELOCITY FIELD IN LAMINAR PULSATING FLOW THROUGH CURVED PIPES - PIV MEASUREMENTS
PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER CONFERENCE
1, PTS A-C
Effects of different parameters on the secondary flow pattern have been studied experimentally by particle image velocimetry (PIV) for a developing laminar pulsating flow through a circular curved pipe. The curvature ratio is eta=r(c)/r(0) = 11 and the curvature angle is 90 degrees. As different secondary flow patterns formed by oscillation cause different transverse mixings, the enhancement of transverse mixing is investigated here. A T-shaped structure installed downstream of the curved pipe allowed PIV measurements obviating light diffraction effects. From knowledge of the velocity components of the secondary flow, the variation in axial vorticity (xi) and transverse strain (epsilon) were calculated. The experiments were carried out for the range of stationary Reynolds numbers 420 <= Re(st)<= 1000 (corresponding to Dean numbers 126.6 <= Dn <= 301.51), velocity component ratios 1 <=(beta=U(max,osc)/U(m,st))<= 4 and frequency parameters 8.37<(alpha=r(0)(omega/nu)(0.5))<24.5. To guarantee being in the laminar regime, the higher values of beta(beta=3 and 4) were studied just for Re(st)=420. The effects of each parameter ((Re(st), beta and alpha) on transverse mixing are discussed by comparing the dimensionless vorticities (vertical bar zeta(P)vertical bar/vertical bar zeta(S)vertical bar) and dimensionless transverse strains (vertical bar epsilon(P)vertical bar/vertical bar epsilon(S)vertical bar) during a complete oscillation period.