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

Abstract

Quantitative and nonintrusive fluid velocity and turbulence measurements obtained using laser Doppler velocimetry (LDV) in a circular jet that is positioned nonconcentrically in a confining pipe are presented. The experimental findings are compared with the results obtained by the finite-element computational simulation of the flow. The measured and predicted contours of the time-averaged axial velocity reveal the presence of a three-dimensional (3-D) asymmetric reverse-flow region, with its radial and circumferential extent depending on the axial position and the eccentricity ratio. Due to the weakened radial mixing and spreading of the jet for the higher eccentricities, the transition to the fully developed state is delayed for the high eccentricity 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 stations, the ringlike distribution tends to become more symmetric. The basic phenomena of flow reversal, preferential mixing, and shear layer growth are recovered 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 between the measured and predicted turbulence fluctuations.