Experimental investigation of the wall shear stress in a circular impinging jet

Hassan, Mouhammad El; Assoum, Hassan; Martinuzzi, Robert J.; Sobolı́k, V.; Abed-Meraïm, Kamel; Sakout, Anas

doi:10.1063/1.4811172

Cited by 36 publications

(14 citation statements)

References 22 publications

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“…The observation that the boundary layer distribution of a concentration is largely unaffected by advection far from the wall motivates a reduced-order, near-wall approach, which can be based on the WSS vector field. It should be noted however that the large scale core flow features determine the WSS patterns (El Hassan et al 2013), therefore the near wall transport depends on the flow topology away from the wall indirectly.…”

Section: Introductionmentioning

confidence: 99%

Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

et al. 2016

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The wall shear stress (WSS) vector field provides a signature for near wall convective transport, and can be scaled to obtain a first order approximation of the near wall fluid velocity. The near wall flow field governs mass transfer problems in convection dominated open flows with high Schmidt number, in which case a flux at the wall will lead to a thin concentration boundary layer. Such near wall transport is of particular interest in cardiovascular flows whereby hemodynamics can initiate and progress biological events at the vessel wall. In this study we consider mass transfer processes in pulsatile blood flow of abdominal aortic aneurysms resulting from complex WSS patterns. Specifically, the Lagrangian surface transport of a species released at the vessel wall was advected in forward and backward time based on the near wall velocity field. Exposure time and residence time measures were defined to quantify accumulation of trajectories, as well as the time required to escape the near wall domain. The effect of diffusion and normal velocity was investigated. The trajectories induced by the WSS vector field were observed to form attracting and repelling coherent structures that delineated species distribution inside the boundary layer consistent with exposure and residence time measures. The results indicate that Lagrangian wall shear stress structures can provide a template for near wall transport.

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Section: Introductionmentioning

confidence: 99%

Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

et al. 2016

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“…Alternatively, most studies rely on the measures based on the WSS magnitude, and the relationship between the vectorial behavior of WSS and its magnitude or angle has received little attention. Likewise, WSS as a vector conveys information about near wall flow transport [25][26][27][28], which is often not considered in WSS characterizations. This is particularly important in the aneurysmal flows where transport of biochemicals/ platelets to and from the wall is of great importance and could be potentially regulated by complex WSS behaviors.…”

Section: Introductionmentioning

confidence: 99%

Characterizations and Correlations of Wall Shear Stress in Aneurysmal Flow

Arzani

Shadden

2015

Journal of Biomechanical Engineering

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Wall shear stress (WSS) is one of the most studied hemodynamic parameters, used in correlating blood flow to various diseases. The pulsatile nature of blood flow, along with the complex geometries of diseased arteries, produces complicated temporal and spatial WSS patterns. Moreover, WSS is a vector, which further complicates its quantification and interpretation. The goal of this study is to investigate WSS magnitude, angle, and vector changes in space and time in complex blood flow. Abdominal aortic aneurysm (AAA) was chosen as a setting to explore WSS quantification. Patient-specific computational fluid dynamics (CFD) simulations were performed in six AAAs. New WSS parameters are introduced, and the pointwise correlation among these, and more traditional WSS parameters, was explored. WSS magnitude had positive correlation with spatial/temporal gradients of WSS magnitude. This motivated the definition of relative WSS gradients. WSS vectorial gradients were highly correlated with magnitude gradients. A mix WSS spatial gradient and a mix WSS temporal gradient are proposed to equally account for variations in the WSS angle and magnitude in single measures. The important role that WSS plays in regulating near wall transport, and the high correlation among some of the WSS parameters motivates further attention in revisiting the traditional approaches used in WSS characterizations.

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“…Secondary counter-rotating vortices are formed at the place where these vortices detach from the wall. These secondary vortices are at the origin of the secondary peak in heat/mass transfer distribution occurring at the radial distance ranging from 1.2d to 2.5d (Lee and Lee, 2000;Violato et al, 2012;Roux et al, 2011;Lytle and Webb 1994;El Hassan et al, 2013). It should be noted that the spatial resolution (0.28d Â 0.28d Â 0.28d) of the tomographic PIV technic used in the present study do not allow to capture this secondary structure, captured previously by the 2D PIV technic in El Hassan et al (2013) (see Fig.…”

Section: Mass Transfer and Wall Shear Ratementioning

confidence: 96%

Mass transfer and shear rate on a wall normal to an impinging circular jet

Kristiawan

Sodjavi

Montagné

et al. 2015

Chemical Engineering Science

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International audienceThe electrodiffusion technique and the time-resolved tomographic PIV were used in impinging jet issued from a convergent conical nozzle at a Reynolds number of 2450 based on the nozzle diameter d and the jet exit velocity. The relative distance from the nozzle to the impinging wall was equal to h/d=2. The experimentally gained velocity fields provides information on the organization of coherent flow structures, which play a role in the wall shear rate and the mass transfer phenomenon at the impinged wall. Instantaneous wall shear rate and local mass transfer were measured at an impinging wall using platinum electrodes with a diameter of 0.5 mm flush mounted into a platinum disc electrode with a diameter of 49.5 mm. The small electrodes were used alternately for the measurement of wall shear rate and mass transfer. The proposed correction factor on the inertia of the concentration boundary layer, which is the ratio of the corrected fluctuations of wall shear rate to their primary values, along with the analysis of the signals history, provide valuable information on the state of the hydrodynamic boundary layer. The mean wall shear rate and local mass transfer exhibit their maximum values at the normalised radial positions r/d=0.6–0.7. There are the interactions of the primary Kelvin–Helmholtz (K–H) vortices with smaller structures issued from the breaking-down of these vortices, both rotating in the same direction. Counter-rotating secondary vortices form between the wall and primary K–H vortices at a radial distance about r/d=1.5. They are present in a wide region (r/d~1.5 to 2.5); around r/d=1.5 they are very close to the wall leading to a clear periodicity of wall shear rate, and at r/d=2.5 they are farther above the wall since no periodicity of the wall shear rate was observed. The local mass transfer rates were integrated and compared with the global mass transfer measured by a platinum disc electrod

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Experimental investigation of the wall shear stress in a circular impinging jet

Cited by 36 publications

References 22 publications

Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

Lagrangian wall shear stress structures and near-wall transport in high-Schmidt-number aneurysmal flows

Characterizations and Correlations of Wall Shear Stress in Aneurysmal Flow

Mass transfer and shear rate on a wall normal to an impinging circular jet

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