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Liquid hydrogen (LH2) spills share many of the characteristics of liquefied natural gas (LNG) spills. LNG spills on water sometimes result in localized vapor explosions known as rapid phase transitions (RPTs), and are a concern in the LNG industry. LH2 RPT is not well understood, and its relevance to hydrogen safety is to be determined. Based on established theory from LNG research, we present a theoretical assessment of an accidental spill of a cryogen on water, including models for pool spreading, RPT triggering, and consequence quantification. The triggering model is built upon film-boiling theory, and predicts that the mechanism for RPT is a collapse of the gas film separating the two liquids (cryogen and water). The consequence model is based on thermodynamical analysis of the physical processes following a film-boiling collapse, and is able to predict peak pressure and energy yield. The models are applied both to LNG and LH2, and the results reveal that (i) an LNG pool will be larger than an LH2 pool given similar sized constant rate spills, (ii) triggering of an LH2 RPT event as a consequence of a spill on water is very unlikely or even impossible, and (iii) the consequences of a hypothetical LH2 RPT are small compared to LNG RPT. Hence, we conclude that LH2 RPT seems to be an issue of only minor concern.
Lars Odsæter; Hans Skarsvåg; Eskil Aursand; Federico Ustolin; Gunhild Reigstad; Nicola Paltrinieri. Liquid Hydrogen Spills on Water—Risk and Consequences of Rapid Phase Transition. Energies 2021, 14, 4789 .
AMA StyleLars Odsæter, Hans Skarsvåg, Eskil Aursand, Federico Ustolin, Gunhild Reigstad, Nicola Paltrinieri. Liquid Hydrogen Spills on Water—Risk and Consequences of Rapid Phase Transition. Energies. 2021; 14 (16):4789.
Chicago/Turabian StyleLars Odsæter; Hans Skarsvåg; Eskil Aursand; Federico Ustolin; Gunhild Reigstad; Nicola Paltrinieri. 2021. "Liquid Hydrogen Spills on Water—Risk and Consequences of Rapid Phase Transition." Energies 14, no. 16: 4789.
Accurate simulation of fluid flow and transport in fractured porous media is a key challenge in subsurface reservoir engineering. Due to the high ratio between its length and width, fractures can be modeled as lower dimensional interfaces embedded in the porous rock. We apply a recently developed embedded finite element method (EFEM) for the Darcy problem. This method allows for general fracture geometry, and the fractures may cut the finite element mesh arbitrarily. We present here a velocity model for EFEM and couple the Darcy problem to a transport problem for a passive solute. The main novelties of this work is a locally conservative velocity approximation derived from the EFEM solution, and the development of a lowest order upwind finite volume method for the transport problem. This numerical model is compatible with EFEM in the sense that the same computational mesh may be applied, so that we retain the same flexibility with respect to fracture geometry and meshing. Hence, our coupled solution strategy represents a simple approach in terms of formulation, implementation and meshing. We demonstrate our model by some numerical examples on both synthetic and realistic problems, including a benchmark study for single-phase flow. Despite the simplicity of the method, the results are promising.
Lars H. Odsæter; Trond Kvamsdal; Mats G. Larson. A simple embedded discrete fracture–matrix model for a coupled flow and transport problem in porous media. Computer Methods in Applied Mechanics and Engineering 2018, 343, 572 -601.
AMA StyleLars H. Odsæter, Trond Kvamsdal, Mats G. Larson. A simple embedded discrete fracture–matrix model for a coupled flow and transport problem in porous media. Computer Methods in Applied Mechanics and Engineering. 2018; 343 ():572-601.
Chicago/Turabian StyleLars H. Odsæter; Trond Kvamsdal; Mats G. Larson. 2018. "A simple embedded discrete fracture–matrix model for a coupled flow and transport problem in porous media." Computer Methods in Applied Mechanics and Engineering 343, no. : 572-601.
Steady-state upscaling of relative permeability is studied for a range of reservoir models. Both rate-dependent upscaling and upscaling in the capillary and viscous limits are considered. In particular, we study fluvial depositional systems, which represent a large and important class of reservoirs. Numerical examples show that steady-state upscaling is rate dependent, in accordance with previous work. In this respect we introduce a scale-dependent capillary number to estimate the balance between viscous and capillary forces. The difference between the limit solutions can be large, and we show that the intermediate flow rates can span several orders of magnitude. This substantiate the need for rate-dependent steady-state upscaling in a range of flow scenarios. We demonstrate that steady-state upscaling converges from the capillary to the viscous limit solution as the flow rate increases, and we identify a simple synthetic model where the convergence fails to be monotone. Two different sets of boundary conditions were tested, but had only minor effects on the presented reservoir models. Finally, we demonstrate the applicability of steady-state upscaling by performing dynamic flow simulation at the reservoir scale, both on fine-scaled and on upscaled models. The considered model is viscous dominated for realistic flow rates, and the simulation results indicate that viscous limit upscaling is appropriate.
Lars Hov Odsæter; Carl Fredrik Berg; Alf Birger Rustad. Rate Dependency in Steady-State Upscaling. 2017, 1 .
AMA StyleLars Hov Odsæter, Carl Fredrik Berg, Alf Birger Rustad. Rate Dependency in Steady-State Upscaling. . 2017; ():1.
Chicago/Turabian StyleLars Hov Odsæter; Carl Fredrik Berg; Alf Birger Rustad. 2017. "Rate Dependency in Steady-State Upscaling." , no. : 1.
A conservative flux postprocessing algorithm is presented for both steady-state and dynamic flow models. The postprocessed flux is shown to have the same convergence order as the original flux. An arbitrary flux approximation is projected into a conservative subspace by adding a piecewise constant correction that is minimized in a weighted $L^2$ norm. The application of a weighted norm appears to yield better results for heterogeneous media than the standard $L^2$ norm which has been considered in earlier works. We also study the effect of different flux calculations on the domain boundary. In particular we consider the continuous Galerkin finite element method for solving Darcy flow and couple it with a discontinuous Galerkin finite element method for an advective transport problem.Comment: 34 pages, 17 figures, 11 table
Lars Hov Odsæter; Mary F. Wheeler; Trond Kvamsdal; Mats G. Larson. Postprocessing of non-conservative flux for compatibility with transport in heterogeneous media. Computer Methods in Applied Mechanics and Engineering 2017, 315, 799 -830.
AMA StyleLars Hov Odsæter, Mary F. Wheeler, Trond Kvamsdal, Mats G. Larson. Postprocessing of non-conservative flux for compatibility with transport in heterogeneous media. Computer Methods in Applied Mechanics and Engineering. 2017; 315 ():799-830.
Chicago/Turabian StyleLars Hov Odsæter; Mary F. Wheeler; Trond Kvamsdal; Mats G. Larson. 2017. "Postprocessing of non-conservative flux for compatibility with transport in heterogeneous media." Computer Methods in Applied Mechanics and Engineering 315, no. : 799-830.
A conservative flux postprocessing algorithm is presented for both steady-state and dynamic flow models. The postprocessed flux is shown to have the same convergence order as the original flux. An arbitrary flux approximation is projected into a conservative subspace by adding a piecewise constant correction that is minimized in a weighted $L^2$ norm. The application of a weighted norm appears to yield better results for heterogeneous media than the standard $L^2$ norm which has been considered in earlier works. We also study the effect of different flux calculations on the domain boundary. In particular we consider the continuous Galerkin finite element method for solving Darcy flow and couple it with a discontinuous Galerkin finite element method for an advective transport problem.
Lars H. Odsæter; Mary F. Wheeler; Trond Kvamsdal; Mats G. Larson. Postprocessing of Non-Conservative Flux for Compatibility with Transport in Heterogeneous Media. 2016, 1 .
AMA StyleLars H. Odsæter, Mary F. Wheeler, Trond Kvamsdal, Mats G. Larson. Postprocessing of Non-Conservative Flux for Compatibility with Transport in Heterogeneous Media. . 2016; ():1.
Chicago/Turabian StyleLars H. Odsæter; Mary F. Wheeler; Trond Kvamsdal; Mats G. Larson. 2016. "Postprocessing of Non-Conservative Flux for Compatibility with Transport in Heterogeneous Media." , no. : 1.
Steady-state upscaling of relative permeability is studied for a range of reservoir models. Both rate-dependent upscaling and upscaling in the capillary and viscous limits are considered. In particular, we study fluvial depositional systems, which represent a large and important class of reservoirs. Numerical examples show that steady-state upscaling is rate dependent, in accordance with previous work. In this respect we introduce a scale-dependent capillary number to estimate the balance between viscous and capillary forces. The difference between the limit solutions can be large, and we show that the intermediate flow rates can span several orders of magnitude. This substantiate the need for rate-dependent steady-state upscaling in a range of flow scenarios. We demonstrate that steady-state upscaling converges from the capillary to the viscous limit solution as the flow rate increases, and we identify a simple synthetic model where the convergence fails to be monotone. Two different sets of boundary conditions were tested, but had only minor effects on the presented reservoir models. Finally, we demonstrate the applicability of steady-state upscaling by performing dynamic flow simulation at the reservoir scale, both on fine-scaled and on upscaled models. The considered model is viscous dominated for realistic flow rates, and the simulation results indicate that viscous limit upscaling is appropriate.
Lars Hov Odsæter; Carl Fredrik Berg; Alf Birger Rustad. Rate Dependency in Steady-State Upscaling. Transport in Porous Media 2015, 110, 565 -589.
AMA StyleLars Hov Odsæter, Carl Fredrik Berg, Alf Birger Rustad. Rate Dependency in Steady-State Upscaling. Transport in Porous Media. 2015; 110 (3):565-589.
Chicago/Turabian StyleLars Hov Odsæter; Carl Fredrik Berg; Alf Birger Rustad. 2015. "Rate Dependency in Steady-State Upscaling." Transport in Porous Media 110, no. 3: 565-589.