This paper presents a drag reduction study using active flow control (AFC) on a generic bluff body. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the two other rounded vertical front corners. The pressure induced separation reproduces the flow detachment occurring at the front A-pillar of a real truck [1]. The prediction of the flow field by partially averaged Navier-Stokes (PANS) simulations, conducted on a relatively coarse mesh, is validated against wind tunnel data (pressure measurements and particle image velocimetry (PIV)) and resolved large eddy simulations (LES) data. The Reynolds number for both simulations and experiments is Re = 5 × 10 5 (which corresponds to 1/6 of a full scale truck Re) based on the inlet velocity U inf and the width of the model W = 0.4m. A validation of PANS results is followed by a CFD study on the actuation frequency that minimizes the aerodynamic drag and suppresses the side recirculation bubbles. PANS accurately predicts the flow field measured in experiments and predicted by a resolved LES. The side recirculation bubble of a simplified truck cabin model is suppressed almost completely and a notable drag reduction by means of AFC is observed.
Porous media model computational fluid dynamics (CFD) is a valuable approach allowing an entire heat exchanger system, including the interactions with its associated installation ducts, to be studied at an affordable computational effort. Previous work of this kind has concentrated on developing the heat transfer and pressure loss characteristics of the porous medium model. Experimental validation has mainly been based on the measurements at the far field from the porous media exit. Detailed near field data are rare. In this paper, the fluid dynamics characteristics of a tubular heat exchanger concept developed for aero-engine intercooling by the authors are presented. Based on a rapid prototype manufactured design, the detailed flow field in the intercooler system is recorded by particle image velocimetry (PIV) and pressure measurements. First, the computational capability of the porous media to predict the flow distribution within the tubular heat transfer units was confirmed. Second, the measurements confirm that the flow topology within the associated ducts can be described well by porous media CFD modeling. More importantly, the aerodynamic characteristics of a number of critical intercooler design choices have been confirmed, namely, an attached flow in the high velocity regions of the in-flow, particularly in the critical region close to the intersection and the in-flow guide vane, a well-distributed flow in the two tube stacks, and an attached flow in the cross-over duct.
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