Application of Active Flow Control on Generic 3D Car Models

Krentel, Daniel; Muminovic, Rifet; Brunn, A.; Nitsche, W.; King, Rudibert

doi:10.1007/978-3-642-11735-0_15

Cited by 22 publications

(13 citation statements)

References 11 publications

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“…Without curved appendices, steady blowing increases base pressure by approximately 5 %, reducing the drag by at most 3 % in the range C µ ∈ [0, 0.015], corresponding to blowing velocities V j /U o ∈ [0, 1.1]. This performance agrees with drag reductions obtained by previous studies with similar steady jet amplitudes in axisymmetric or square-back models (Freund & Mungal 1994;Wassen et al 2010;Krentel et al 2010). In the case of steady blowing, while no difference is measured up to C µ ∼ 7.5 × 10 −3 (V j /U o ∼ 0.55), the Coanda effect improves base pressure recovery at higher blowing velocities.…”

Section: Impact On the Base Pressure And Wake Flowsupporting

confidence: 87%

Bluff body drag manipulation using pulsed jets and Coanda effect

et al. 2016

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The impact of fluidic actuation on the wake and drag of a 3D blunt body is experimentally investigated. The wake is forced by jets pulsed tangentially to the main flow with variable frequency and velocity. Depending on the forcing conditions, two flow regimes can be identified. First, for a broadband range of frequencies comprising the natural wake instabilities, the convection of the jet structures enhances wake entrainment, shortening the recirculating flow length with an augmentation of the bluff body drag. Further increase of the actuation frequency induces a wake fluidic boat-tailing by shear-layer deviation. It additionally lowers turbulent intensity and entrainment of high momentum fluid in the shear layer, leading to an overall reduction of the wake fluctuating kinetic energy. The association of both mechanisms is responsible for a raise of base pressure and decrease of the model's drag. The physical features of such regimes are discussed on the basis of drag, pressure and velocity measurements at several upstream conditions and control parameters. By adding curved surfaces at the jet outlets to take advantage of the so-called Coanda effect, periodic actuation can be further reinforced leading to drag reductions of about 20 % in unsteady regime. In general, the unsteady Coanda blowing not only intensifies the base pressure recovery but also preserves the effect of unsteady high frequency forcing on the turbulent field. The present results encourage the development of fluidic control in road vehicles' aerodynamics as well as provide a complement to our current understanding of bluff body drag and its manipulation.Comment: 47 pages, 35 figures, extended versio

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Section: Impact On the Base Pressure And Wake Flowsupporting

confidence: 87%

Bluff body drag manipulation using pulsed jets and Coanda effect

et al. 2016

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“…Rouméas et al (2008) used steady aspiration on the top of the slant: he obtained numerically a drag reduction of 17% and noticed experimentally a suppression of the separation area (Rouméas 2006). Experimental studies were carried out by Leclerc (2008) with synthetic jets (zero net mass flux) at the top slant edge area (8.5% reduction) and by Krentel et al (2010) with pulsed jets at the bottom slant edge (5.7% reduction). Both Krajnovic et al (2009) and Lehugeur (2009) made numerical simulations of the same case: the former obtained a little bit more than 7% reduction using steady blowing and suction at the slant top edge (and also studied several other blowing locations and jet types), while the latter used steady blowing to force the bursting of longitudinal coherent structures, leading to a 6% drag reduction.…”

Section: Introductionmentioning

confidence: 99%

Drag reduction on the 25° slant angle Ahmed reference body using pulsed jets

2011

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This paper highlights steady and unsteady measurements and flow control results obtained on an Ahmed model with slant angle of 25°in wind tunnel. On this high-drag configuration characterized by a large separation bubble along with energetic streamwise vortices, time-averaged and time-dependent results without control are first presented. The influence of rear-end periodic forcing on the drag coefficient is then investigated using electrically operated magnetic valves in an open-loop control scheme. Four distinct configurations of flow control have been tested: rectangular pulsed jets aligned with the spanwise direction or in winglets configuration on the roof end and rectangular jets or a large open slot at the top of the rear slant. For each configuration, the influence of the forcing parameters (non-dimensional frequency, injected momentum) on the drag coefficient has been studied, along with their impact on the static pressure on both the rear slant and vertical base of the model. Depending on the type and location of pulsed jets actuation, the maximum drag reduction is obtained for increasing injected momentum or well-defined optimal pulsation frequencies.

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“…Increasing the momentum coefficient beyond 0.04 provides only small further savings, mostly due to the thrust of the actuation jets. Since this effect would also be present in an application to a real vehicle, we rate the AFC efficiency by calculating the net power savings ∆P/P 0 , as suggested by Krentel et al 30 For the baseline case without actuation the power…”

Section: Flow Characteristicsmentioning

confidence: 99%

Linear parameter-varying active flow control for a 3D bluff body exposed to cross-wind gusts

Pfeiffer

King

2014

32nd AIAA Applied Aerodynamics Conference

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A linear-parameter varying (LPV) gain-scheduling controller for closed-loop active flow control of base pressure and yaw moment of a 3D bluff body is presented. It is designed based on a LPV model identified from experimental data, which takes the parameter dependency of the actuated flow characteristics on time-varying side-wind angles better into account than linear black-box models. The LPV control performance is demonstrated and compared to a linear robust H∞-controller in wind tunnel experiments with realistic crosswind gusts. A novel model traverse mechanism is used to replicate the lateral vehicle dynamics and driver behaviour in the wind tunnel. The controller is able to provide net power savings of up to 8%, corresponding to a 15% drag reduction, while simultaneously reducing the cross-wind sensitivity of the vehicle. This results in smaller lateral deviations and yaw rates of the vehicle, effectively improving safety and comfort for the driver, who needs less steering effort to compensate for side-wind gusts.

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Application of Active Flow Control on Generic 3D Car Models

Cited by 22 publications

References 11 publications

Bluff body drag manipulation using pulsed jets and Coanda effect

Bluff body drag manipulation using pulsed jets and Coanda effect

Drag reduction on the 25° slant angle Ahmed reference body using pulsed jets

Linear parameter-varying active flow control for a 3D bluff body exposed to cross-wind gusts

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