Velocity measurements of dilute particulate suspension over and through a porous medium model

Haffner, Eileen; Mirbod, Parisa

doi:10.1063/5.0015207

Cited by 20 publications

(8 citation statements)

References 85 publications

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“…We observe that for the two volume fractions considered, the variations due to these parameters are small, indicating that the variations in the permeability provide the major contribution, consistent with what was previously observed by Rosti et al [41]. More precisely, we find no appreciable differences when changing the porous layer thickness [62,63,43,64], while small variations are found when changing the porosity. In particular, the two largest values of ε (0.6 and 0.9) provide very close results, while the smallest value of ε (0.3) leads to a slight reduction in the mean shear rate by further increasing the Φe for various permeabilities σ.…”

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confidence: 91%

The impact of porous walls on the rheology of suspensions

Rosti¹,

Mirbod²,

Brandt³

2020

Preprint

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We study the effect of isotropic porous walls on a plane Couette flow laden with spherical and rigid particles. We perform a parametric study varying the volume fraction between 0 and 30%, the porosity between 0.3 and 0.9 and the non-dimensional permeability between 0 and 7.9 × 10 −3 We find that the porous walls induce a progressive decrease in the suspension effective viscosity as the wall permeability increases. This behavior is explained by the weakening of the wall-blocking effect and by the appearance of a slip velocity at the interface of the porous medium, which reduces the shear rate in the channel. Therefore, particle rotation and the consequent velocity fluctuations in the two phases are dampened, leading to reduced particle interactions and particle stresses. Based on our numerical evidence, we provide a closed set of equations for the suspension viscosity, which can be used to estimate the suspension rheology in the presence of porous walls.

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confidence: 91%

The impact of porous walls on the rheology of suspensions

Rosti¹,

Mirbod²,

Brandt³

2020

Preprint

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“…By increasing σ (i.e., decreasing the permeability K), the velocity diminishes because the lower permeability decreases the velocity at the suspension-porous interface as well as in the porous layer by stronger viscous drag originated from Darcy's law, whereas the velocity is larger than that of suspension flows past impermeable walls even for very high σ (i.e., low permeability). As reported in Mirbod et al (2017), Mirbod (2018), andHaffner and, the flow of pure Newtonian fluid in the fluid layer is also enhanced by the presence of a permeable wall.…”

Section: Problem Formulationmentioning

confidence: 54%

“…For the fluid flow through porous media, the slip velocity U s defined as the streamwise (or axial) velocity at the interface is the most important parameter of the flow since it is required to evaluate the penetration of the fluid region into the porous medium (Agelinchaab et al 2006;Arthur et al 2009;Mirbod et al 2017;Wu and Mirbod (2018); Wu and Mirbod (2019); Haffner and Mirbod (2020)). To characterize the variation of the slip velocity U s normalized by U o and shear rate γ at the suspension-porous interface, we then calculate U s for all values of ϕ b and σ; the plots of U s (ϕ b ,σ) are shown in Fig.…”

Section: Problem Formulationmentioning

confidence: 99%

Pressure-driven pipe flow of semi-dilute and dense suspensions over permeable surfaces

Kang

Mirbod

2021

Rheol Acta

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We study pressure-driven suspensions of non-colloidal, non-Brownian, and rigid spheres in a Newtonian solvent where the pipe surface is replaced by porous media using numerical simulations. We examine various values of the permeability of the porous medium K, while we keep the porosity and the thickness of the porous layer constant to clarify the effect of the permeable wall on the suspension flows at bulk particle volume fractions 0.1 ≤ ϕ b ≤ 0.5. In the limit of vanishing inertia, the rate of suspension flow decreases as the bulk volume fraction ϕ b increases and it builds up as the permeability of the porous media increases. There are also two different regimes characterizing the dimensionless slip velocity normalized by both shear rate and penetration depth, namely, the strong permeability regime and the weak permeability regime. In the former, the solvent penetrates deeper and the streamwise velocity at the interface increases with the porous media permeability, while in the latter, the fluid cannot go through the porous media deeply and the variation of the slip velocity with the permeability is small. Our results might suggest a new passive technique to reduce drag by enhancing the rate of suspension flow in devices where the suspension transport is crucial. It might also offer basic insights for the extension to the flow of suspensions over and through complex porous media.

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“…This flow rate was closer to what is typically used in dental practice in conjunction with a CUS. The shadowgraphy procedure has been discussed in detail in our previous publications (Haffner and Mirbod 2020 ; Mirbod et al 2021 ; Wu and Mirbod 2018 ). Using the shadowgraphy technique, we obtained the raw images.…”

Section: Resultsmentioning

confidence: 99%

An experimental approach to analyze aerosol and splatter formations due to a dental procedure

et al. 2021

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Graphical abstract Throughout 2020 and beyond, the entire world has observed a continuous increase in the infectious spread of the novel coronavirus (SARS-CoV-2) otherwise known as COVID-19. The high transmission of this airborne virus has raised countless concerns regarding safety measures employed in the working conditions for medical professionals. Specifically, those who perform treatment procedures on patients which intrinsically create mists of fine airborne droplets, i.e., perfect vectors for this and other viruses to spread. The present study focuses on understanding the splatter produced due to a common dentistry technique to remove plaque buildup on teeth. This technique uses a high-speed dentistry instrument, e.g., a Cavitron ultrasonic scaler, to scrape along the surface of a patient’s teeth. This detailed understanding of the velocity and the trajectory of the droplets generated by the splatter will aid in the development of hygiene mechanisms to guarantee the safety of those performing these procedures and people in clinics or hospitals. Optical flow tracking velocimetry (OFTV) method was employed to obtain droplet velocity and trajectory in a two-dimensional plane. Multiple data collection planes were taken in different orientations around a model of adult mandibular teeth. This technique provided pseudo-three-dimensional velocity information for the droplets within the splatter developed from this high-speed dental instrument. These results indicated that within the three-dimensional splatter produced there were high velocities (1–2 m/s) observed directly below the intersection point between the front teeth and the scaler. The splatter formed a cone-shape structure that propagated 10–15 mm away from the location of the scaler tip. From the droplet trajectories, it was observed that high velocity isolated droplets propagate away from the bulk of the splatter. It is these droplets which are concerning for health safety to those performing the medical procedures. Using a shadowgraphy technique, we further characterize the individual droplets’ size and their individual velocity. We then compare these results to previously published distributions. The obtained data can be used as a first step to further examine flow and transport of droplets in clinics/dental offices.

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Velocity measurements of dilute particulate suspension over and through a porous medium model

Cited by 20 publications

References 85 publications

The impact of porous walls on the rheology of suspensions

The impact of porous walls on the rheology of suspensions

Pressure-driven pipe flow of semi-dilute and dense suspensions over permeable surfaces

An experimental approach to analyze aerosol and splatter formations due to a dental procedure

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