Control of flow geometry using electromagnetic body forcing

Rossi, Lionel; Bocquet, S.; Ferrari, Simone; Cruz, J. M. García de la; Lardeau, Sylvain

doi:10.1016/j.ijheatfluidflow.2009.02.024

Cited by 22 publications

(15 citation statements)

References 25 publications

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“…[5,26]. At low Reynolds number, such body forcing can also be used to design bespoke flows, [17]. Fig.…”

Section: Electromagnetically Driven Flowsmentioning

confidence: 99%

“…The electromagnetic forcing model is based on an analytical model [35,52], considering the 3D distribution of the permanent magnets. Previous numerical simulations have been carried out and validated for different intensity of the forcing, geometries and brine thickness which were chosen accordingly to experiments (more details in [17,50]). Magnets are modeled with a height equal to 2L M and a magnetic intensity at the center of B r = 0.68T.…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…In this paper, we introduce a measure of lamination and a quantification of the lamination rate process. This process and measure are then quantified and illustrated using canonical flows driven by mono-and multi-scale electromagnetic forcing [17]. The aim is to provide a basic analytical description of the mixing process of turbulent flows, based on few assumptions.…”

Section: Introductionmentioning

confidence: 99%

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Lamination and folding in electromagnetically driven flows of specified geometries

Rossi¹,

Lardeau²

2011

Journal of Turbulence

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In this paper, a new characterization and a quantification of lamination are presented. The lamination is identified by tracking material lines and by the estimation of the ratio between the length of the material lines within circles and the diameter of the circles. The quantification of the lamination rate relies on the interlaced structure of velocity and Lagrangian acceleration, which allows the determination of the spatial variation of the Lagrangian angular velocity. Those definitions are illustrated using quasi-steady flows driven by electromagnetic forces using mono-and multi-scale configurations with turbulent-like properties. Both experimental and numerical data are used to compute folding rate intensities and lamination for a large range of length scales. Good agreement is found between grid deformation and the prediction of lamination rate, an agreement further confirmed by the measure of lamination. The quantification of lamination is simple and well defined at chosen length-scales. Also, the present form applies to any lines and can be extended to 3D flows. The lamination rate process rely on physical quantities which scale according to the structures' length-scales. It is shown that the lamination rate increases with the reduction of the length-scales and in particular it is found thatṘ f ol ∼ ℓ −3/4 . In turbulent flows, the lamination should then be faster within small coherent structures. This quantification of lamination rate, complemented by a measure of lamination opens new routes for the description and the quantification of mixing in complex and turbulent flows.

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“…[5,26]. At low Reynolds number, such body forcing can also be used to design bespoke flows, [17]. Fig.…”

Section: Electromagnetically Driven Flowsmentioning

confidence: 99%

Section: Numerical Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lamination and folding in electromagnetically driven flows of specified geometries

Rossi¹,

Lardeau²

2011

Journal of Turbulence

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“…For instance, turbulent flows play a huge role in the motion of air around and behind cars, airplanes, boats, and other moving objects, because of drag and wake; in the reduction of the concentration of pollutants released in the atmosphere or in the sea (Ferrari and Querzoli, 2010 [1]) by human activities; in the weather forecasts, in the study of the motion of hurricanes, water and air masses in the ocean and in the atmosphere; in the optimization of mixing and combustion and in flow control (Rossi et al 2009 [2]) in engines and chemical reactors; in biological flows such as the air flowing through the lungs (Ramuzat and Riethmuller, 2001 [3]) or the blood motion in the aorta (Elkins et al, 2005 [4]) or downstream a stenosis (Zhu et al, 2011 [5]). The scalar quantity transport by turbulent flows plays a relevant role in many environmental phenomena, such as particle transport in geophysical flows (Boffetta et al, 2000 [6]).…”

Section: Introduction: Image Analysismentioning

confidence: 99%

Image analysis techniques for the study of turbulent flows

Ferrari

2017

EPJ Web Conf.

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Abstract. In this paper, a brief review of Digital Image Analysis techniques employed in Fluid Mechanics for the study of turbulent flows is given. Particularly the focus is on the techniques developed by the research teams the Author worked in, that can be considered relatively "low cost" techniques. Digital Image Analysis techniques have the advantage, when compared to the traditional techniques employing physical point probes, to be non-intrusive and quasi-continuous in space, as every pixel on the camera sensor works as a single probe: consequently, they allow to obtain two-dimensional or three-dimensional fields of the measured quantity in less time. Traditionally, the disadvantages are related to the frequency of acquisition, but modern high-speed cameras are typically able to acquire at frequencies from the order of 1 KHz to the order of 1 MHz. Digital Image Analysis techniques can be employed to measure concentration, temperature, position, displacement, velocity, acceleration and pressure fields with similar equipment and setups, and can be consequently considered as a flexible and powerful tool for measurements on turbulent flows.

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“…The PIV processing is performed using an in-house, e.g. Rossi et al [2009], Rossi [2010], code based on an iterative method to adapt the size of the correlation windows with sub-pixel interpolation (and accuracy) for the estimation of the final displacement. The frames resolution is about 12.35 pixels/mm.…”

Section: Introductionmentioning

confidence: 99%

Exploration of the rotational power consumption of a rigid flapping wing

Truppel

Rossi

2011

Exp Fluids

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The development of Micro Air Vehicles with flapping wings is inspired from the observation and study of natural flyers such as insects and birds. This article explores the rotational power consumption of a flapping wing using a mechanical flapper at Re ≃ 4500. This mechanical flapper is simplified to a 2D translation and a rotation in a water tank. Moreover, the wing kinematics are reduced to a linear translation and a rotation for the purpose of our study. We introduce the notion of non-ideal flapper and associated non-ideal rotational power. Such non-ideal devices are defined as consuming power for adding and removing mechanical power to the flow. First we use a traditional symmetrical wing kinematic which is a simplified kinematic inspired from natural flyers. The lift coefficient of this flapping is about C L ≃ 1.5. This symmetrical wing kinematic is chosen as a reference. Further wing kinematics with asymmetric rotations are then compared to this one. These new kinematics are built using a differential velocity defined according to the translational kinematics, a time lag and a distance, r kp . The analogy of this distance is discussed as a key point to follow along the chord. First, the wing kinematics are varied keeping a similar shape for the profiles of the angular velocity. It is shown that when compared to the reference wing kinematic, a 10% reduction of the rotational power is obtained whilst the lift is reduced by 9%. Second, we release the limitation to a similar shape for the profiles of the angular velocity leading to a novel shape for the angular velocity profile named here as "double bump" profile. With these new wing kinematics, we show that a 60% reduction of the non-ideal rotational power can be achieved whilst the lift coefficient is only reduced by 1.7%. Such "double bump kinematics" could then be of interest to increase the endurance of Micro-Air-Vehicles.

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Control of flow geometry using electromagnetic body forcing

Cited by 22 publications

References 25 publications

Lamination and folding in electromagnetically driven flows of specified geometries

Lamination and folding in electromagnetically driven flows of specified geometries

Image analysis techniques for the study of turbulent flows

Exploration of the rotational power consumption of a rigid flapping wing

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