Paula Kozlowski Pitombeira Reis

• Reis, Paula Kozlowski Pitombeira; Flekkøy, Eirik Grude; Toussaint, Renaud & Måløy, Knut Jørgen (2026). Linear response theory of front back-contraction during a single Haines jump. Journal of Fluid Mechanics. ISSN 0022-1120. 1041. doi: 10.1017/jfm.2026.11960. Fulltekst i vitenarkiv Vis sammendrag

  We study the linear response of a fluid–fluid interface in a porous medium subjected to a localised, transient perturbation. A single pore is driven out of mechanical equilibrium by a small displacement, initiating a back-contraction of the interface. Assuming negligible total flow, the interface relaxes with a time- and space-dependent profile h(x,t), modelled for a flat geometry. This set-up reflects conditions achievable experimentally using a localised heterogeneity in pore-throat sizes. We determine the evolving interface shape during the relaxation process, together with the associated pressure and velocity fields, using both analytical calculations and pore-network simulations.

• Vargdal, Sigurd; Reis, Paula Kozlowski Pitombeira; Sveinsson, Henrik Andersen & Linga, Gaute (2026). Neural Networks for Predicting Permeability Tensors of 2D Porous Media: Comparison of Convolution- and Transformer-based Architectures. arXiv. doi: 10.48550/ARXIV.2512.01517. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira & Måløy, Knut Jørgen (2025). Drainage front width in a three-dimensional random porous medium under gravitational and capillary effects. Physical Review Research (PRResearch). 7(3). doi: 10.1103/5bbz-ksds. Fulltekst i vitenarkiv
• Brodin, Joachim Falck; Pierce, James Kevin; Reis, Paula Kozlowski Pitombeira; Rikvold, Per Arne; Moura, Marcel & Jankov, Mihailo [Vis alle 7 forfattere av denne artikkelen] (2025). Interface instability of two-phase flow in a three-dimensional porous medium. Physical Review Fluids. 10(6). doi: 10.1103/hm82-167x. Fulltekst i vitenarkiv Vis sammendrag

  We present an experimental study of immiscible, two-phase fluid flow through a three-dimensional porous medium consisting of randomly packed, monodisperse glass spheres. Our experiments combine refractive-index matching and laser-induced fluorescence imaging to resolve the morphology and stability of the moving interface resulting from the injection of one fluid into another. The imposed injection rate sets a balance between gravitational and viscous forces, producing interface morphologies which range from unstable collections of tangled fingers at low rates to stable sheets at high rates. The image data are complemented by time-resolved pressure measurements. We develop a stability criterion for the fluid interface based on the analysis of the 3D images and the pressure data. This criterion involves the Darcy permeability in each of the two phases and the time derivative of the pressure drop across the medium. We observe that the relative permeability encountered by the invading fluid is modified by the imposed flow rate in our experiment, which impacts the two-phase flow dynamics. We show that, in addition to the balance between the relevant forces driving the dynamics, local regions of crystalline order in the beadpack (crystallites) affect the stability of the invading front. This work provides insights into how disorder on multiple length scales in porous media can interact with viscous, capillary, and gravitational forces to determine the stability and dynamics of immiscible fluid interfaces.

• Reis, Paula Kozlowski Pitombeira & Måløy, Knut Jørgen (2025). Drainage front width in a three-dimensional random porous medium under gravitational and capillary effects. http://arxiv.org/abs/cond-mat. Fulltekst i vitenarkiv Vis sammendrag

  A theoretical approach to estimating stable drainage front widths in three-dimensional random porous media under gravitational and capillary effects is presented. Based on the frontier of the infinite cluster in gradient percolation, we propose an expression for the 3D front width dependent on the pore-network topology, the distribution of capillary pressure thresholds for the pore throats, the stabilizing capillary pressure gradient, the average pore size, and the correlation length critical exponent from percolation in three dimensions. Theoretical predictions are successfully compared to numerical results obtained with a bond invasion-percolation model for a wide range of drainage flow parameters.

• Khobaib, Khobaib; Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Toussaint, Renaud; Flekkøy, Eirik Grude & Måløy, Knut Jørgen (2025). Gravity stabilized drainage in porous media with controlled disorder. Physical Review Research (PRResearch). 7(2). doi: 10.1103/PhysRevResearch.7.023040. Fulltekst i vitenarkiv Vis sammendrag

  This work presents an experimental, numerical, and theoretical investigation of slow drainage processes in porous media, focusing on systematic variations in pore-scale disorder. We examine a system comprising a monolayer of cylinders in a quasi-two-dimensional (2D) geometry, where the medium's disorder is controlled via a disorder parameter, 𝜀. By systematically altering 𝜀, we randomly shift the positions of the cylinders and analyze the resulting effects on the gravity stabilized invasion front. Our results show that increasing 𝜀 has a significant impact on the stable width of the invasion front, with this width scaling with the disorder parameter according to an exponent 𝛽=0.57, which closely matches the theoretical value predicted by percolation theory for 2D systems. Additionally, we derive a reciprocal relationship between the dimensionless fluctuation number and the disorder parameter 𝜀. Moreover, we find a correlation between the invasion front width and the size of trapped clusters in the system, and we explore how pore disorder affects the air saturation left behind the invasion front. Both our experimental and numerical findings exhibit exponent values that align with theoretical scaling predictions. This study advances the current understanding of multiphase flows in porous media by specifically addressing the influence of pore-scale disorder on the morphology of invasion fronts.

• Reis, Paula Kozlowski Pitombeira; Linga, Gaute; Moura, Marcel; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2025). Interaction between corner and bulk flows during drainage in granular porous media. Advances in Water Resources. ISSN 0309-1708. 198. doi: 10.1016/j.advwatres.2025.104914. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Linga, Gaute; Moura, Marcel; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2024). Interaction between corner and bulk flows during drainage in granular porous media. arXiv.org. ISSN 2331-8422. doi: 10.48550/arXiv.2409.05574. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Linga, Gaute; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2023). A simplified pore-scale model for slow drainage including film-flow effects. Advances in Water Resources. ISSN 0309-1708. 182. doi: 10.1016/j.advwatres.2023.104580. Fulltekst i vitenarkiv Vis sammendrag

  Liquid-filled corners and capillary bridges can establish networks connecting seemingly isolated clusters during drainage in porous media. Coupled with drainage through the bulk of pores and throats, the flow through these networks constitutes a secondary drainage mechanism that can significantly affect fluid configurations and residual saturations. In order to investigate the prevalence of this drainage mechanism, we propose a quasi-static pore-network model based on modifying the trapped-cluster-identification algorithm in an invasion-percolation model. With the modification, wetting-phase connectivity is provided by direct successions of pores and throats, represented by sites and bonds, as well as by chains of interconnected capillary bridges. The advancement of the fluid interface in the porous matrix is determined by the bonds’ invasion thresholds and local capillary pressure values, calculated taking into consideration gravitational effects. With the proposed model, experimentally verified phenomena related to slow drainage in granular porous media are reproduced, showing good qualitative agreement.

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• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Pierce, Kevin; Måløy, Knut Jørgen & Linga, Gaute (2026). Secondary imbibition in 2D porous media: The role of flow direction in trapping. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Flekkøy, Eirik Grude; Toussaint, Renaud & Måløy, Knut Jørgen (2026). Linear Response Theory of Front-Back Contraction During a Single Haines Jump. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira & Måløy, Knut Jørgen (2026). A Theoretical Model for Stable Drainage Fronts in 3D Porous Media. Fulltekst i vitenarkiv
• Moura, Marcel; Brodin, Joachim Falck; Reis, Paula Kozlowski Pitombeira; Pierce, Kevin; Jankov, Mihailo & Rikvold, Per Arne [Vis alle 11 forfattere av denne artikkelen] (2026). From Thin Films to Stable Fronts: Tabletop Experimental Approaches to 2D and 3D Porous Media Flows. doi: https:/www.youtube.com/live/bSQ-sHK6FTU?si=W9_rbJ5BkyRPHP0m. Fulltekst i vitenarkiv
• Moura, Marcel; Reis, Paula Kozlowski Pitombeira; Rikvold, Per Arne; Linga, Gaute; Flekkøy, Eirik Grude & Schäfer, Gerhard [Vis alle 8 forfattere av denne artikkelen] (2026). Thin Film Flow: Fluid Transport via Thin Liquid Films in Slow Porous Media Flows. Fulltekst i vitenarkiv
• Moura, Marcel; Reis, Paula Kozlowski Pitombeira; Rikvold, Per Arne; Linga, Gaute; Flekkøy, Eirik Grude & Schäfer, Gerhard [Vis alle 8 forfattere av denne artikkelen] (2025). Thin Film Flow: Fluid Transport via Thin Liquid Films in Slow Porous Media Flows. Fulltekst i vitenarkiv
• Brodin, Joachim Falck; Moura, Marcel; Pierce, James Kevin; Reis, Paula Kozlowski Pitombeira; Rikvold, Per Arne & Jankov, Mihailo [Vis alle 7 forfattere av denne artikkelen] (2025). Experimental Investigation of Two-Phase Flow with a Table-Top Optical Scanner: Interface Instability in a Three-Dimensional Porous Medium. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Linga, Gaute; Toussaint, Renaud; Rikvold, Per Arne & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2025). Modeling Gas-Liquid Drainage in Porous Media with Network Models. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira & Måløy, Knut Jørgen (2025). Drainage fronts in two and three-dimensional random porous media under gravitational and capillary effects. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira & Måløy, Knut Jørgen (2025). Numerical investigation of invasion-front characteristics during stable drainage in a three-dimensional porous medium. Fulltekst i vitenarkiv
• Moura, Marcel; Måløy, Knut Jørgen; Flekkøy, Eirik Grude; Brodin, Joachim Falck; Reis, Paula Kozlowski Pitombeira & Linga, Gaute [Vis alle 7 forfattere av denne artikkelen] (2024). A pool of two-phase flows experiments: films, bursts, patterns and avalanches. Fulltekst i vitenarkiv
• Moura, Marcel; Måløy, Knut Jørgen; Flekkøy, Eirik Grude; Brodin, Joachim Falck; Reis, Paula Kozlowski Pitombeira & Linga, Gaute [Vis alle 7 forfattere av denne artikkelen] (2024). A little bit of our activity at PoreLab and Njord. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Linga, Gaute; Moura, Marcel; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2024). Investigation of liquid connectivity and drainage in granular porous media. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira (2024). Multiphase Flow Through Porous Media. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Linga, Gaute; Moura, Marcel; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2024). Investigation of liquid connectivity and drainage in granular porous media. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Vincent-Dospital, Tom Yannick Yves; Toussaint, Renaud & Måløy, Knut Jørgen (2024). Modeling drainage in porous media with stratified gradient in pore sizes. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Linga, Gaute; Moura, Marcel; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2024). Network modeling of corner and bulk flows during drainage in granular porous media. Fulltekst i vitenarkiv
• Moura, Marcel; Reis, Paula Kozlowski Pitombeira; Schäfer, Gerhard; Toussaint, Renaud; Flekkøy, Eirik Grude & Rikvold, Per Arne [Vis alle 7 forfattere av denne artikkelen] (2023). Thin film flow: fluid transport via thin liquid films in slow porous media flows. Fulltekst i vitenarkiv
• Khobaib, Khobaib; Reis, Paula Kozlowski Pitombeira; Jankov, Mihailo; Moura, Marcel & Måløy, Knut Jørgen (2023). Experimental studies of slow drainage in porous media: Effect of the randomness of the porous medium on the fluid flow. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Linga, Gaute; Rikvold, Per Arne; Flekkøy, Eirik Grude & Måløy, Knut Jørgen (2023). A simplified pore-scale model for drainage including film flow effects. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Linga, Gaute; Rikvold, Per Arne; Flekkøy, Eirik Grude & Måløy, Knut Jørgen (2023). A modified-invasion-percolation model for drainage in quasi-2D porous media. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Linga, Gaute; Rikvold, Per Arne; Flekkøy, Eirik Grude & Måløy, Knut Jørgen (2023). A simplified pore-scale model for slow drainage including film-flow effects. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Linga, Gaute; Rikvold, Per Arne; Toussaint, Renaud & Flekkøy, Eirik Grude [Vis alle 7 forfattere av denne artikkelen] (2023). Numerical analysis of drainage in porous media using network models. Fulltekst i vitenarkiv
• Reis, Paula Kozlowski Pitombeira; Moura, Marcel; Måløy, Knut Jørgen; Flekkøy, Eirik Grude & Rikvold, Per Arne (2022). Pore-scale modeling of film flow effects during gas-liquid drainage. Fulltekst i vitenarkiv

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