湍流边界层,聚合物,拖曳减阻中速度矢量场,浓度场检测方案(粒子图像测速)

Much progress has been made in the understanding of the phenomenon of drag reduction by dilute solutions of polymers since its discovery in 1948. While the use of advanced techniques in experiments and computational simulations have dramatically advanced our understanding of the phenomenon, a complete and conclusive explanation of the physics associated with the phenomenon is still lacking. In particular, drag reduction in boundary layers with injection has not been studied extensively to understand the processes and physics that govern the spread and mixing of the injected polymer in the flow. To overcome this limitation, in the present work, drag reduction due to polymer injection in a turbulent boundary layer is studied using simultaneous Particle Imaging Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF). PIV is used to measure the velocity of the flow in the boundary layer and to calculate higher order velocity statistics. PLIF is used to study the distribution and spread of the injected polymer in the boundary layer by tracking a fluorescent dye mixed in with it. The polymer of choice, polyethylene oxide, is injected as a dilute solution into a fully turbulent Newtonian boundary layer and measurements of velocity and concentration are made at different downstream locations on the flat plate to study the effect of the polymer on the flow and the evolution of drag reduction. The data from the two measurement techniques are combined to calculate turbulent fluxes and to estimate the turbulent Schmidt number in polymer drag reduced flows.