Vortical Flow Structure Genesis of Lobed Nozzle Flows

摘要

Mixing flows is essential for a lot of industrial and aerodynamical applications. In particular, mixing of the hot engine exhaust flows with colder bypass air stream is a topic in the research field of military aircraft design. Often, lobed nozzles are prefered configurations in order to increase mixing of hot and cold air and, thereby, to enforce the decreasing of the exhaust jet core temperatures. In the present study the flow field generated by generic lobed nozzles is considered. Focal points of this work are the generated vortical flow structures and their complex interaction in dependence of geometry variations of the lobes. Especially, the spreading of the vortices and the behaviour of the core part is examined in regard to the objective to derive order parameters which might be useful for the design of better mixing devices. This study is based on numerical flow simulations using a standard finite volume flow solver. Incompressible laminar flows at low Reynolds numbers are simulated addressing the fundamental physical mechanisms of vortex interaction, destructive shearing flows and vortex reorganisation and reconnection in the wake field of lobed nozzles.