Cleaning of a Rough Rigid Surface: Removal of a Dissolved Contaminant by Convection‐Enhanced Diffusion and Chemical Reaction

Chilukuri, R.; Middleman, Stanley

doi:10.1149/1.2115772

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…Physically, we know this enforcement to be an oversimplification of the recirculatory flow within the dead-end pore space. Chilukuri and Middleman (1984) corrected for this oversimplification by describing mass transport from dead-end pores as a result of vortex-enhanced diffusion -a conclusion that coincides with a series of publications that detail the vortex structures within dead-ended pores (Moffatt, 1963;Mehta and Lavan, 1969;O' Brien, 1972;Shen and Floryan, 1985;Kang and Chang, 1982;Fang et al, 1997). The evolution of the dead-end pore model is illustrated in Figure 4, below.…”

Section: The Dead-end Pore Modelmentioning

confidence: 64%

“…Most of this work is geared at industry for the guise of expediting rate-limited manufacturing processes (e.g., etching, finishing, cleaning, etc.) that are applied to surfaces with cavities (Chilukuri and Middleman, 1984;Alkire et al, 1990;Fang et al, 1999).…”

Section: Cavity Flowsmentioning

confidence: 99%

“…To observe movement of the separatrix in the idealized pore space, we use Mathematica's numerical differential equation solver, NDSolve, to solve the continuity equation (mass conservation), Navier-Stokes equations (momentum evolution), and associated boundary conditions. The solver domain is a replica of the idealized pore space utilized by Kahler and Kabala (2016) and is similar in geometry to the domain commonly used in the study of flow past cavities (Chilukuri and Middleman, 1984;Higdon, 1985;Fang et al, 1997). For the sake of simplicity, the flow is modeled as being two-dimensional.…”

Section: Numerical Flow Solvermentioning

confidence: 99%

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Hydrodynamic Porosity: A Paradigm Shift in Flow and Contaminant Transport Through Porous Media, Part I

Young,

Kabala

2023

Preprint

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Abstract. Pore-scale flow velocity is an essential parameter in determining transport through porous media, but it is often miscalculated. Researchers use a static porosity value to relate volumetric or superficial velocities to pore-scale flow velocities. We know this modeling assumption to be an oversimplification. The variable fraction of porosity conducive to flow, what we define as hydrodynamic porosity, θmobile, exhibits a quantifiable dependence on Reynolds number (i.e., pore-scale flow velocity) in the Laminar flow regime. This fact remains largely unacknowledged in the literature. In this work, we quantify the dependence of θmobile on Reynolds number via numerical flow simulation at the pore scale. We demonstrate that, for a medium with the chosen cavity geometries, θmobile decreases by as much as 42 % over the Laminar flow regime. Moreover, θmobile exhibits an exponential dependence on Reynolds number. The fit quality is effectively perfect, with a coefficient of determination (R²) of approximately 1 for each set of simulation data. Finally, we show that this exponential dependence can be easily solved for pore-scale flow velocity through use of only a few Picard iterations, even with an initial guess that is 10 orders of magnitude off. Not only is this relationship a more accurate definition of pore-scale flow velocity, but it is also a necessary modeling improvement that can be easily implemented.

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Section: The Dead-end Pore Modelmentioning

confidence: 64%

Section: Cavity Flowsmentioning

confidence: 99%

Section: Numerical Flow Solvermentioning

confidence: 99%

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Hydrodynamic Porosity: A Paradigm Shift in Flow and Contaminant Transport Through Porous Media, Part I

Young,

Kabala

2023

Preprint

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“…A problem analogous to the one described here in porous media has been investigated in cleaning small‐scale ducts and manufacturing high‐performance electronics (e.g., semiconductor boards), as surfaces must be exceptionally clean for proper operation. In semiconductor manufacture, surfactants must therefore be removed from microscopic cavities in the surfaces of materials at multiple stages of the process, which is done by a continuous flow of cleanser over the surface [ Chilukuri , ; Chilukuri and Middleman , ]. The contaminant transfer between the cavity and surface flow is greatest before the vortex fully forms in the cavity because the flow at this transient stage is traveling deep into the cavity [ Fang , ]; a process that we will refer to as a deep sweep , the first of two mechanisms studied here.…”

Section: Introductionmentioning

confidence: 99%

Acceleration of groundwater remediation by deep sweeps and vortex ejections induced by rapidly pulsed pumping

Kahler

Kabala

2016

Water Resources Research

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One key limiting factor to groundwater remediation is contaminant sequestered in pores whose contents do not mix well with the bulk flow. Mixing between well-connected (pores whose volume is flushed as water flows through the aquifer) and poorly connected pores (pores whose volume does not exchange readily when water flows through the aquifer) is of primary concern. Under steady flow, contaminants are effectively trapped in the poorly connected pores and are transferred only by molecular diffusion. This slow mixing process between pore types is a bottleneck to remediation. We present a novel rapidly pulsed pumping method that increases the mixing between these pore types. We do it in the context of pump-and-treat remediation because it is the most common remediation practice. In rapidly pulsed pumping, the increase in flow causes a deep sweep, which pushes the flow into poorly connected pores and sweeps out sequestered contaminants. The decrease in flow causes a vortex ejection, which causes the vortex within the poorly connected pore to emerge with contaminant. These actions are modeled with computational fluid mechanics to elucidate the individual mechanisms and determine how they function and interact. Cleanup of single and multiple poorly connected pore systems were simulated and show the acceleration possible. This technique can decrease the time and cost needed to remediate contaminated aquifers, which in the United States has been estimated to exceed $1 trillion. Since our rapidly pulsed pumping method enhances mixing between well-connected and poorly connected pores, it can be applied to other remediation schemes such as in situ methods.Pump-and-treat remediation (P&T) is a process where contaminant-rich water from the aquifer is pumped out and cleaned at the surface by one of several methods [see Khan et al., 2004], then pumped back into the aquifer or released to surface water. P&T is the most common remediation technique; in a survey of sites under Superfund, 83% use P&T: 56% use P&T exclusively and 27% use P&T with another technology [EPA, 2007]. Remediation times depend on the contaminant, porous media, and other hydrologic factors. Unfortunately, the P&T process typically lasts decades to as much as a century [NRC, 1994]. Of P&T sites surveyed, median annual costs are one tenth of capital costs with totals of millions to tens of millions of dollars [EPA, 1999]. Reduction in the duration of remediation would dramatically decrease the total cost.

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“…Another application of mass transfer in restricted geometries is given in the study of the problem of contamination and cleaning of a rough metal surface by Chilukuri and Middleman [109], In particular, a model was developed which calculated the rate of disappearance of a species dissolved in a fluid trapped in a microscopic cavity. This model accounted for diffusion, convection and chemical reaction and assumed constant shear stress along the cavity lid, so that solution of the Stokes equation to obtain the flow field was unnecessary.…”

Section: Townes and Saberskymentioning

confidence: 99%

Theoretical and Experimental Investigation of Chemical Pattern Etching

Γεωργιαδου¹

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Cleaning of a Rough Rigid Surface: Removal of a Dissolved Contaminant by Convection‐Enhanced Diffusion and Chemical Reaction

Cited by 4 publications

References 5 publications

Hydrodynamic Porosity: A Paradigm Shift in Flow and Contaminant Transport Through Porous Media, Part I

Hydrodynamic Porosity: A Paradigm Shift in Flow and Contaminant Transport Through Porous Media, Part I

Acceleration of groundwater remediation by deep sweeps and vortex ejections induced by rapidly pulsed pumping

Theoretical and Experimental Investigation of Chemical Pattern Etching

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