ETD

• angle between co-moving flows and their velocity
• DNS
• mixing layer development
• openfoam code
• quantity of interest
• stresses field

In the present thesis the mixing-layer evolution has been studied by means of numerical simulations. The effect of two parameters have been investigated,namely the angle between the two co-moving flows (θ) and their velocity ratio (α). These parameters are found to be important because they would influence the flow transitions from the laminar to the fully developed turbulent regime. The angle θ is considered as a possible uncertain parameter because an error angle during misalignment of experimental setup of mixing layer can happen. The considered range is equal to θ =0÷15 degrees. As for the velocity ratio, α =0.2÷0.7 is chosen as a suitable range for the investigation. Four simulations are carried out for the four corner values. In addition, two simulations are performed for θ = 0. Direct numerical simulation are carried out at Reynolds number Re =100, by using the open-source code OpenFoam. The results show that the two considered parameters have a significant effect in the development and evolution of the mixing-layers, in terms of velocity, vorticity and Reynolds stresses. The increase in the velocity ratio value leads to an increase in the mixing layer cross-flow dimension. This is related with an increase of the shear effects that is proportional with the velocity ratio. The angle θ has a significant effect in promoting mixing, especially for the case with minimum velocity ratio. However, the topology of the vortical structures in the latter case (minimum α and maximum θ) present a swirled flow, that is not present in the cases with a good alignment between the two co-moving flows.