Development and Application of a New Unsteady Far-Field Drag Decomposition Method

Toubin, Hélène; Bailly, Didier

doi:10.2514/6.2014-2991

Cited by 5 publications

(4 citation statements)

References 7 publications

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“…Aerodynamic forces may be decomposed by far-field drag extraction methods (Destarac 2003;van der Vooren & Destarac 2004;Toubin & Bailly 2015;among others), but these methods are non-local and in some cases rely on the spatial isolation of global physical processes which however tend to overlap within the boundary layer. Sometimes, thermodynamic considerations are inserted together with mathematical transformations which may have no physical interpretation, so that the final decomposition is not always intuitive or straightforwardly related to simple physical phenomena.…”

Section: Introductionmentioning

confidence: 99%

A theoretical decomposition of mean skin friction generation into physical phenomena across the boundary layer

2016

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A theoretical decomposition of mean skin friction generation into physical phenomena across the whole profile of the incompressible zero-pressure-gradient smooth-flat-plate boundary layer is derived from a mean streamwise kinetic-energy budget in an absolute reference frame (in which the undisturbed fluid is not moving). The Reynolds-number dependences in the laminar and turbulent cases are investigated from direct numerical simulation datasets and Reynolds-averaged Navier-Stokes simulations, and the asymptotic trends are consistently predicted by theory. The generation of the difference between the mean friction in the turbulent and laminar cases is identified with the total production of turbulent kinetic energy (TKE) in the boundary layer, represented by the second term of the proposed decomposition of the mean skin friction coefficient. In contrast, the analysis introduced by Fukagata et al. on a streamwise momentum budget in the wall reference frame, relates the turbulence-induced excess friction to the Reynolds shear stress weighted by a linear function of the wall distance. The wall-normal distribution of the linearly-weighted Reynolds shear stress differs from the distribution of TKE production involved in the present discussion, which consequently draws different conclusions on the contribution of each layer to the mean skin friction coefficient. At low Reynolds numbers, the importance of the buffer-layer dynamics is confirmed. At high Reynolds numbers, the present decomposition quantitatively shows for the first time that the generation of the turbulence-induced excess friction is dominated by the logarithmic layer. This is caused by the well-known decay of the relative contributions of the buffer layer and wake region to TKE production with increasing Reynolds numbers. This result on mean skin friction, with a physical interpretation relying on an energy budget, is consistent with the well-established general importance of the logarithmic layer at high Reynolds numbers, contrary to the friction breakdown obtained from the approach of Fukagata et al. based on a momentum budget. The new decomposition suggests that it may be worth investigating new drag reduction strategies focusing on TKE production and on the nature of the logarithmic layer dynamics. The decomposition is finally extended to the pressure-gradient case and to channel and pipe flows.

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Section: Introductionmentioning

confidence: 99%

A theoretical decomposition of mean skin friction generation into physical phenomena across the boundary layer

2016

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“…The term s denotes entropy and ∆s = (s − s ∞ ). FFX provides the exergy-based formulation summarized within the equation (2) for aeropropulsive performance assessment developed by A. Arntz during his PhD thesis [6]. More details of the theoretical development are available in reference [8].…”

Section: Formulationmentioning

confidence: 99%

“…Moreover farfield drag extraction approach is still a living research topic. For example, extensions for postprocessing unsteady flow fields have been proposed by Toubin et al [2] and Gariepy et al [3] and a new approach based on a Lamb vector approach is currently under study [4] [5]. However, future commercial aircraft are likely to get highly integrated propulsion systems.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Exergy Analysis of CFD Simulations for the Evaluation of Aero-Thermo-Propulsive Performance of Aerial Vehicles

Wervaecke

Petropoulos

Bailly

2020

Computational Methods in Applied Sciences

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“…Nose-shape effects on submarine model wake were also considered in their research. Toubin and Bailly [24] developed a formulation based on thermodynamic considerations. The brand new formulation decomposed the drag force into shock wave term, viscous interaction term, and lift-induced vortices component.…”

Section: Introductionmentioning

confidence: 99%

Streamlined bodies drag force estimation using wake integration technique

Shirazi

Manshadi

2020

J Braz. Soc. Mech. Sci. Eng.

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In this paper, the drag force calculation around the SUBOFF submarine in axisymmetric configuration was investigated using the "Wake Integration Technique." This method is usually used in wind tunnels as an auxiliary method instead of the common "surface integral technique" for flow around complex geometries or shock wave flows. The results of this method are dependent on data collection vertex space, distance, and section size, where practical suggestions were made for each parameter in this research. Furthermore, the contribution of the pressure, momentum, and fluctuation terms in the total drag force were also evaluated at different cross sections. These findings can be implemented in wind tunnels with small test section length and also to compare the results obtained by the common surface integral method. Simulations were carried out at different aspect ratios at zero angles of attack, and the capabilities of this method at inclined flows were also discussed. The obtained results were also compared against the common method, and the results show only 4% deviation at zero angle. Keywords Wake survey • Wind tunnel • Drag force • Momentum defect principle • Suboff submarine List of symbols L Body length D Maximum body diameter AR Length-to-the-diameter aspect ratio x, y, z Coordinate system Δx, Δy Grid space in x and y-direction d The ratio of grid space to diameter X Longitudinal distance from the body r Measurement radius S Surface area P , u Local pressure and velocity P ∞ , U ∞ Free-stream pressure and velocity C D Drag coefficient C p Pressure coefficient Incidence angle y + Dimensionless wall distance Fluid density xx Normal stress component

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Development and Application of a New Unsteady Far-Field Drag Decomposition Method

Cited by 5 publications

References 7 publications

A theoretical decomposition of mean skin friction generation into physical phenomena across the boundary layer

A theoretical decomposition of mean skin friction generation into physical phenomena across the boundary layer

Assessment of Exergy Analysis of CFD Simulations for the Evaluation of Aero-Thermo-Propulsive Performance of Aerial Vehicles

Streamlined bodies drag force estimation using wake integration technique

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