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

Pfeiffer, Jens; King, Rudibert

doi:10.2514/6.2014-2406

Cited by 4 publications

(1 citation statement)

References 23 publications

(13 reference statements)

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“…Since active systems require energy to operate, it is critical that the power gained through drag reductions and the use of AFC to be as large as possible in comparison to the expanded power of the blown jet. This relation can be quantified by the power ratio [18],…”

Section: Introductionmentioning

confidence: 99%

Shape Optimization of Active and Passive Drag-Reducing Devices on a D-shaped Bluff Body

Semaan

2017

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Shape optimization of an active and a passive drag-reducing device on a two-dimensional D-shaped bluff body is performed. The two devices are: Coanda actuator, and randomly-shaped trailing-edge flap. The optimization sequence is performed by coupling the genetic algorithm software DAKOTA to the mesh generator Pointwise and to the CFD solver OpenFOAM. For the the active device the cost functional is the power ratio, whereas for the passive device it is the drag coefficient. The optimization leads to total power savings of ≈ 70% for the optimal Coanda actuator, and a 40% drag reduction for the optimal flap. This reduction is mainly achieved through streamlining the base flow and suppressing the vortex shedding. The addition of either an active or a passive device creates two additional smaller recirculation regions in the base cavity that shifts the larger recirculation region away from the body and increases the base pressure. The results are validated against more refined URANS simulations for selected cases.

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Section: Introductionmentioning

confidence: 99%

Shape Optimization of Active and Passive Drag-Reducing Devices on a D-shaped Bluff Body

Semaan

2017

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Robust control of drag and lateral dynamic response for road vehicles exposed to cross-wind gusts

Pfeiffer

King

2018

Exp Fluids

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A robust closed-loop active flow control strategy for road vehicles under unsteady cross-wind conditions is presented. It is designed based on black-box models identified from experimental data for a 3D bluff body equipped with Coanda actuators along the rear edges. The controller adjusts the blowing rates of the actuators individually, achieving a drag reduction of about 15% while simultaneously improving cross-wind sensitivity. Hereby, the lateral vehicle dynamics and driver behavior are taken into account and replicated in the wind tunnel via a novel model support system. The effectiveness of the control strategy is demonstrated via cross-wind gust experiments.

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Explorative gradient method for active drag reduction of the fluidic pinball and slanted Ahmed body

Cui

Jia

et al. 2021

J. Fluid Mech.

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We address a challenge of active flow control: the optimization of many actuation parameters guaranteeing fast convergence and avoiding suboptimal local minima. This challenge is addressed by a new optimizer, called the explorative gradient method (EGM). EGM alternatively performs one exploitive downhill simplex step and an explorative Latin hypercube sampling iteration. Thus, the convergence rate of a gradient based method is guaranteed while, at the same time, better minima are explored. For an analytical multi-modal test function, EGM is shown to significantly outperform the downhill simplex method, the random restart simplex, Latin hypercube sampling, Monte Carlo sampling and the genetic algorithm. EGM is applied to minimize the net drag power of the two-dimensional fluidic pinball benchmark with three cylinder rotations as actuation parameters. The net drag power is reduced by 29 % employing direct numerical simulations at a Reynolds number of $100$ based on the cylinder diameter. This optimal actuation leads to 52 % drag reduction employing Coanda forcing for boat tailing and partial stabilization of vortex shedding. The price is an actuation energy corresponding to 23 % of the unforced parasitic drag power. EGM is also used to minimize drag of the $35^\circ$ slanted Ahmed body employing distributed steady blowing with 10 inputs. 17 % drag reduction are achieved using Reynolds-averaged Navier–Stokes simulations at the Reynolds number $Re_H=1.9 \times 10^5$ based on the height of the Ahmed body. The wake is controlled with seven local jet-slot actuators at all trailing edges. Symmetric operation corresponds to five independent actuator groups at top, middle, bottom, top sides and bottom sides. Each slot actuator produces a uniform jet with the velocity and angle as free parameters, yielding 10 actuation parameters as free inputs. The optimal actuation emulates boat tailing by inward-directed blowing with velocities which are comparable to the oncoming velocity. We expect that EGM will be employed as efficient optimizer in many future active flow control plants as alternative or augmentation to pure gradient search or explorative methods.

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

Cited by 4 publications

References 23 publications

Shape Optimization of Active and Passive Drag-Reducing Devices on a D-shaped Bluff Body

Shape Optimization of Active and Passive Drag-Reducing Devices on a D-shaped Bluff Body

Robust control of drag and lateral dynamic response for road vehicles exposed to cross-wind gusts

Explorative gradient method for active drag reduction of the fluidic pinball and slanted Ahmed body

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