LDV measurements and computation of a turbulent circular jet placed non-concentrically in a confining pipe

Quantitative and nonintrusive fluid velocity and turbulence measurements ob tained using laser Doppler velocimetry (LDV) in a circular jet that is posi tioned nonconcentrically in a confining pipe are presented. The experimenta l findings are compared with the results obtained by the finite-element com putational simulation of the flow. The measured and predicted contours of t he time-averaged axial velocity reveal the presence of a three-dimensional (3-D) asymmetric reverse-flow region, with its radial and circumferential e xtent depending on the axial position and the eccentricity ratio. Due to th e weakened radial mixing and spreading of the jet for the higher eccentrici ties, the transition to the fully developed state is delayed for the high e ccentricity cases. Measured and predicted contours of the axial turbulence fluctuations exhibit the ringlike distribution, although it is observed in an offset position for a given eccentricity ratio. At the downstream statio ns, the ringlike distribution tends to become more symmetric. The basic phe nomena of flow reversal, preferential mixing, and shear layer growth are re covered by the computational predictions based on the high-Reynolds-number turbulence model. The time-averaged velocity measurements compare well with the predictions, whereas only qualitative comparison can be observed betwe en the measured and predicted turbulence fluctuations.