Mixing enhancement of jets and drag reduction in manipulated bluff body wakes.

摘要

In the first part of this work a direct numerical simulation of the approach is employed in the study of a planar jet immersed in a co-flowing stream. An aerodynamic vectoring effect on the jet is achieved by the application of asymmetrically distributed suction at the lips of the exit nozzle. An optimal suction distribution for maximum lift generation is located and used in conjunction with time-dependent stimulation to enhance the mixing characteristics of the jet. The dynamic behavior of the system in the phase plane is explored and a regime of suction parameters for maximum mixing enhancement is revealed. The attractor selection sensitivity to initial conditions of the system is also investigated.; The second part of this dissertation used direct numerical simulation in the study of the flow dynamics in the near wake of a two dimensional rectangular bluff body. The suppression of the global mode of instability via base suction or bleed is investigated and the ventilation coefficient cvent , a non-dimensional measure of the ventilation mass flux, is identified as a major scaling parameter in the determination of the structural characteristics and suppression of the global mode of via base bleed.; Aerodynamic drag reduction is pursued by modifying the base pressure component of the drag. Boat-tails (blocks and plates) are attached at the trailing edge of the rectangular forebody and an optimal aspect ratio for boat-tail notches at the separation point is identified. The use of boat-tailing in conjunction with base bleed is also investigated and the common underlying mechanism leading to elevated base pressure in different configurations is revealed.