Powei Huang Publications Content

Publications

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Underlined names are links to current or past GEG members

REFEREED PUBLICATIONS IN JOURNALS

3. 
Huang, P.-W., B. Flemisch, C.-Z. Qin, M.O. Saar, and A. Ebigbo, Relating Darcy-scale chemical reaction order to pore-scale spatial heterogeneity, Transport in Porous Media, 2022. [Download PDF] [View Abstract]Due to spatial scaling effects, there is a discrepancy in mineral dissolution rates measured at different spatial scales. Many reasons for this spatial scaling effect can be given. We investigate one such reason, i.e., how pore-scale spatial heterogeneity in porous media affects overall mineral dissolution rates. Using the bundle-of-tubes model as an analogy for porous media, we show that the Darcy-scale reaction order increases as the statistical similarity between the pore sizes and the effective-surface-area ratio of the porous sample decreases. The analytical results quantify mineral spatial heterogeneity using the Darcy-scale reaction order and give a mechanistic explanation to the usage of reaction order in Darcy-scale modeling. The relation is used as a constitutive relation of reactive transport at the Darcy scale. We test the constitutive relation by simulating flow-through experiments. The proposed constitutive relation is able to model the solute breakthrough curve of the simulations. Our results imply that we can infer mineral spatial heterogeneity of a porous media using measured solute concentration over time in a flow-through dissolution experiment.

2. 
Naets, I., M. Ahkami, P.-W. Huang, M. O. Saar, and X.-Z. Kong, Shear induced fluid flow path evolution in rough-wall fractures: A particle image velocimetry examination, Journal of Hydrology, 610/127793, 2022. [Download PDF] [View Abstract]Rough-walled fractures in rock masses, as preferential pathways, largely influence fluid flow, solute and energy transport. Previous studies indicate that fracture aperture fields could be significantly modified due to shear displacement along fractures. We report experimental observations and quantitative analyses of flow path evolution within a single fracture, induced by shear displacement. Particle image velocimetry and refractive index matching techniques were utilized to determine fluid velocity fields inside a transparent 3D-printed shear-able rough fracture. Our analysis indicate that aperture variability and correlation length increase with the increasing shear displacement, and they are the two key parameters, which govern the increases in velocity variability, velocity longitudinal correlation length, streamline tortuosity, and variability of streamline spacing. The increase in aperture heterogeneity significantly impacts fluid flow behaviors, whilst changes in aperture correlation length further refine these impacts. To our best knowledge, our study is the first direct measurements of fluid velocity fields and provides insights into the impact of fracture shear on flow behavior.

1. 
Huang, P.W., and F. Wellmann, An Explanation to the Nusselt–Rayleigh Discrepancy in Naturally Convected Porous Media, Transport in Porous Media, 2021. [Download PDF] [View Abstract]We model hydrothermal convection using a partial differential equation formed by Darcy velocity and temperature—the velocity formulation. Using the Elder problem as a benchmark, we found that the velocity formulation is a valid model of hydrothermal convection. By performing simulations with Rayleigh numbers in the non-oscillatory regime, we show that multiple quasi-steady-state solutions can be one of the reasons that caused the Nusselt–Rayleigh discrepancy found in previous experiments. The results reveal more understandings about the nature of uncertainty of convection modes in porous media.


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PROCEEDINGS REFEREED

1. 
Huang, P.W., and J.F. Wellmann, Investigating Different Formulations for Hydrothermal Convection in Geothermal Systems, Proceedings World Geothermal Congress 2020, 2020. [View Abstract]Hydrothermal convection in porous media is an essential piece of physics in geothermal reservoirs, and understanding them leads to better development of geothermal energy. We analyze the validity of simulating hydrothermal convection using different formulations of partial differential equations. Using the Elder problem as a benchmark, we found out that the stream function formulation and the velocity formulation are a valid and efficient model of hydrothermal convection. The Nusselt number and entropy production are measurements of the quality of convective heat transfer. The Rayleigh number describes the physical properties of a porous media. We use simulations to investigate further the discrepancy in the Nusselt Rayleigh relationship found in previous experiments. The conclusion is that the multiple steady states of convection pattern in a 3D box are the main reason for the discrepancy found in the Nusselt-Rayleigh relationship.


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THESES

1. 
Huang, P.W., Investigating different formulations for hydrothermal convection in geothermal systems, MSc Thesis, RWTH Aachen, 2017. [View Abstract]Hydrothermal convection in porous media is an important piece of physics in geothermal reservoirs, and understanding them leads to better development of geothermal energy. We analyze the validity of simulating hydrothermal convection using different formulations of partial differential equations. Using the Elder problem as a physical benchmark, we found out that the stream function formulation and the velocity formulation are a valid and efficient model of hydrothermal convection. The Nusselt number and entropy production are measurements of the quality of convective heat transfer. The Rayleigh number describes the physical properties of a porous media. We use simulations to further investigate the discrepancy in the Nusselt Rayleigh relationship found in previous experiments. The conclusion is that the multiple steady states of convection pattern in a 3D box are the main reason for the discrepancy in the Nusselt Rayleigh relationship.