Experimental And Numerical Investigations On The Vortical Structures Of An Impinging Jet In Crossflow

Investigations on an impinging jet under the influence of crossflow are carried out in this dissertation. There exit jet shear layer, impingement on the bottom wall, interactions between the induced wall jet and the ambient crossflow in near field. There are few intensive studies of the impinging jet in crossflow at home and abroad due to the flow complexities such as the formation and evolution of the vortical structures, interactions between vortices, while researches on the temporal and spatial evolving of these vortical structures can promote the practical applications in environment engineering, hydroelectricity engineering etc. as well as reveal the inherent mechanism and development of the vortical structures and provide the basis for flow control and improvement.Both experimental investigation and numerical simulation are conducted to obtain the detailed flow features and vortical structures in the near field of the impinging jet in crossflow. For the experiment, LIF (laser induced fluorescence) flow visualization and PIV (particle image velocimetry) measurement are adopted to study the effects of the flow parameters on the unsteady characteristics of the flow and vortical structures. For the numerical simulation, unsteady three-dimensional LES (large eddy simulation) is used to obtain the temporal and spatial evolving of the jet and the 3D configuration of the vortices formed by the interactions among jet, bottom wall and ambient crossflow. Results from experiment and computation can be validation and complement to each other.It can be inferred from flow visualization and PIV measurement that the shear layer vortices, jet wake vortices, upstream wall vortex and scarf vortex vary with the flow parameters and there exist interactions in various vortical structures. There are three arrangement types of the original vortices in the upwind and lee sides of the jet, namely approximate axisymmetry, alternation and helicity while any arrangement type will grow into helical one during developing with the main jet and being affected by the crossflow and interaction between vortices. Vortices in the upwind shear layer will form a more regular arrangement than those in the lee side, and there exist obvious intervals between vortices. The jet wake vortices occurring in the lee side of the jet show an evident three dimensional movement including the spin and stretch in the horizontal plane as well as the torsion in the vertical plane. And the global feature of the jet wake vortices appear to be very complicated, there exit not only the alternating circulation but also the same rotation direction for vortices...