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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Numerical Analysis of Cavitation-Induced Two-Phase Fluid Transients in Cryogenic Feedlines Using Finite Volume Procedure

This article presents a numerical investigation of the cavitation induced fluid transient in cryogenic feedline due to sudden closure of the valve A one dimensional numerical model based on finite volume procedure consisting of nodes and branches using Generalized Fluid System Simulation Program ( has been employed for the prediction of pressure variations The unsteady friction formulation accurately determines wall shear stress, and a homogeneous mixture model is used for two phase flow modeling Numerical results obtained with the present formulation are compared with experimental results and Method of Characteristic ( based results It is observed that low residual in flow variable calculation improves the solution providing numerically stable results GFSSP is able to reproduce the fluid transient peak due to vapor collapse Subsequently, it can retain the shape of pressure wave for two phase fluid transients, but it is dampening faster compared to experiments Further investigation is required with set of experiments to validate the present numerical approach for different experimental data.

Fluid Transient↗
NASA NTRSDate not supplied

Passive Fluid Transport in Microgravity Environments for the Stabilization of Rotating Spacecrafts

Rotating spacecraft offers the potential to create artificial gravity for extended space missions. However, designing a guidance and control system for such vehicles involves complex considerations. This paper examines a vehicle segmented into three parts, with the propulsion unit positioned at the vehicle’s center of mass. The vehicle must maintain stability around this central point, even under atypical conditions. Consequently, a durable and passive spin stabilization system is essential, requiring the passive transport of fluids. A combined system consisting of microcapillary bundles and hydraulic ram pumps is explored to transport fluids without any external energy added to the system. The dynamics of such a system are investigated, establishing performance and control limitations, and developing a control strategy predicated on the fluid dynamics between the segments. A model of the system is developed to validate the approach, showing that passive stabilization is possible, however, not as effective as an active stabilization system. Additionally, the model can be expanded for broader applications, including mass redistribution, a theoretical fluid ring, and three axis rotating systems.

Dynamics↗
NASA NTRSDate not supplied

Plant Watering in Low Gravity: The Study of the Fluid Dynamic Characteristics of Lunar Regolith Simulant for the Application of Crop Production Systems Using Scaled Capillary Devices

Bioregenerative life support is key to sustaining human life on the surface of other celestial bodies for missions beyond Low Earth Orbit (LEO). One example of such life support includes crop production systems capable of producing both plants and fungi for astronaut consumption. There have been numerous efforts to design and deploy such systems; however, there have been persistent fundamental issues with the water delivery systems. This study aims to understand and model the fluid dynamics of crop production systems to inform engineers about the key parameters needed for the design of such systems. The primary objective is to validate and expand upon NASA’s previous study, the Plant Water Management (PWM) experiments, to understand the fluid phenomena present in substrate-based systems. The model will then be expanded to include parameters for changing the test material of potential growth media as well as the varying water demands of the crop throughout its different stages in its life cycle. Specifically, this study is focused on the viability of using lunar regolith for agricultural purposes. Terrestrial-based scaled capillary models will be utilized to mimic the fluid phenomena occurring due to the low gravity environment seen on the lunar surface. Ultimately, the study will model the fluid flow present in the lunar regolith simulant and inform researchers on how to incorporate the material into crop production systems on the lunar surface.

gravity↗
DOE OSTI2016

High-fidelity simulation-driven model development for coarse-grained computational fluid dynamics

Nuclear reactor safety analysis requires analysis of a broad range of accident scenarios and determining their consequences. For a nuclear power plant behavior, it is impossible to obtain experimental data at sufficiently large scales to support calibration and validation of various system models. In single-phase flow convective problems, high-resolution methods of Computational Fluid Dynamics (CFD) such as Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) can provide high fidelity results under conditions where physical measurements are unavailable. However, such high-resolution simulations are computationally expensive and not suitable for simulation of long transient scenarios in nuclear reactor accidents. In this work, we investigate the use of a high fidelity simulation-driven approach to model sub-grid scale (SGS) effect in Coarse Grained Computational Fluid Dynamics CG-CFD. Notably, fine-mesh simulations are used to construct physics-informed statistical surrogate of coarse-mesh SGS model. For an initial analysis, we consider a case of turbulent natural convection in a volumetrically heated fluid layer with a thermally insulated lower boundary and isothermal upper boundary. This scenario of unstable stratification is relevant to turbulent natural convection in a severe nuclear reactor accident, as well as in containment mixing and passive cooling. For this type of flow, the SGS effect is modeled by an added turbulent diffusivity in the energy equation. It is shown that a global correction for the energy equation is sufficient to achieve a significant improvement to the CG-CFD prediction of thermal mixing in the fluid layer. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

Fluid Properties for MOOSE

The Multiphysics Object-Oriented Simulation Environment (MOOSE) enables a wide range of advanced nuclear reactor simulations. Under the guidance of MOOSE's Finite Volume Team, we worked on the fluid properties module. Significant contributions include enabling Tabulated Fluid Properties (TFP) for systems thermal hydraulics analysis, Temperature and Pressure functionalized Fluid Properties, and Lead & Lead-Bismuth properties. Along with improving the capabilities of the fluid properties module, we also improved the documentation to allow for future users and developers to understand how the module works.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Fault structure, stress, or pressure control of the seismicity in shale? Insights from a controlled experiment of fluid-induced fault reactivation

It is clear that clay formations are present in reservoirs and earthquake faults, but questions remain on their mechanical behavior, as they can vary from ductile (aseismic) to brittle (seismic). An experiment, at a scale of 10 m, aims to reactivate a natural fault by fluid pressure in shale materials. The injection area was surrounded by a dense monitoring network comprising pressure, deformation, and seismicity sensors, in a well-characterized geological setting. Thirty-two microseismic events were recorded during several injection phases in five different locations within the fault zone. Their computed magnitude ranged between -4.3 and -3.7. Their spatiotemporal distribution, compared with the measured displacement at the injection points, shows that most of the deformation induced by the injection is aseismic. Whether the seismicity is controlled by the fault architecture, mineralogy of fracture filling, fluid, and/or stress state is then discussed. The fault damage zone architecture and mineralogy are of crucial importance, as seismic slip mainly localizes on the sealed-with-calcite fractures which predominate in the fault damage zone. As no seismicity is observed in the close vicinity of the injection areas, the presence of fluid seems to prevent seismic slips. The fault core acts as an impermeable hydraulic barrier that favors fluid confinement and pressurization. Therefore, the seismic behavior seems to be strongly sensitive to the structural heterogeneity (including permeability) of the fault zone, which leads to a heterogeneous stress response to the pressurized volume.

58 GEOSCIENCES↗
DOE OSTI2017

Investigation of multiphase fluid imbibition in shale through synchrotron-based dynamic micro-CT imaging

While substantial advances were made in pore system characterization in shale in the past decade, understanding of fundamentals of multiphase fluid flow in shale remains limited. The complexity of multiphase fluid flow in shale is related to many factors including nanoscale to submicron-scale pore systems, differences in mineralogy and associated surface wettability, heterogeneity of these properties at different scales, and possible existence of microfractures. Previous work related to fluid flow, such as permeability measurement, spontaneous imbibition, and wettability analysis, includes many simplified assumptions/hypotheses with limited consideration of small-scale details. In addition, these studies were mostly focused on single-phase phenomena. Direct observation of multiphase fluid flow in shale showing small-scale details is highly desired. In this study, dynamic imaging using synchrotron-based micro-CT (computed microtomography) was conducted on two shale samples to investigate multiphase (oil and water) spontaneous imbibition. Here, the results revealed many details of multiphase flow in shale, including pore connectivity, porosity and permeability layered distribution, and wettability of microfractures and pores. At the same time, results illustrate the complexity of multiphase flow in shale and gaps in understanding that need further investigation.

58 GEOSCIENCES↗
DOE OSTI2015

Development of a discontinuous approach for modeling fluid flow in heterogeneous media using the numerical manifold method

Summary In the numerical modeling of fluid flow in heterogeneous geological media, large material contrasts associated with complexly intersected material interfaces are challenging, not only related to mesh discretization but also for the accurate realization of the corresponding boundary constraints. To address these challenges, we developed a discontinuous approach for modeling fluid flow in heterogeneous media using the numerical manifold method (NMM) and the Lagrange multiplier method (LMM) for modeling boundary constraints. The advantages of NMM include meshing efficiency with fixed mathematical grids (covers), the convenience of increasing the approximation precision, and the high integration precision provided by simplex integration. In this discontinuous approach, the elements intersected by material interfaces are divided into different elements and linked together using the LMM. We derive and compare different forms of LMMs and arrive at a new LMM that is efficient in terms of not requiring additional Lagrange multiplier topology, yet stringently derived by physical principles, and accurate in numerical performance. To demonstrate the accuracy and efficiency of the NMM with the developed LMM for boundary constraints, we simulate a number of verification and demonstration examples, involving a Dirichlet boundary condition and dense and intersected material interfaces. Last, we applied the developed model for modeling fluid flow in heterogeneous media with several material zones containing a fault and an opening. We show that the developed discontinuous approach is very suitable for modeling fluid flow in strongly heterogeneous media with good accuracy for large material contrasts, complex Dirichlet boundary conditions, or complexly intersected material interfaces. Copyright © 2015 John Wiley & Sons, Ltd.

Hu, Mengsu↗
DOE OSTI2021

Phase-field modeling of rate-dependent fluid-driven fracture initiation and propagation

The rate-dependent behavior associated with deformation and fracturing of materials, such as natural rocks, poses significant challenges for modeling. In addition to the complications of the viscoelastic response, the speed of fracture propagation reflects micromechanical mechanisms in the fracture process zone(FPZ). In order to represent these complicated behaviors, a thermodynamically consistent, rate-dependent fracture model is required. Based on rigorous thermodynamic principles, we derive a rate-dependent phase-field mechanical model coupled with single-phase fluid flow in both the matrix and the fracture. The model is guaranteed to satisfy energy conservation during fracture propagation. Here, the system of equations is solved using the introduced solution procedure and a novel preconditioner that accounts for the complex fluid-structure interaction. The proposed phase-field model is tested against several benchmark problems on solid-fluid coupling, fluid-driven fracture propagation and rate-dependent viscoelastic deformation. The model serves as a strong basis for investigating rate-dependent fracturing experiments and for making predictions of material behaviors under new conditions.

42 ENGINEERING↗
DOE OSTI2022

A two-fluid single-column model of turbulent shallow convection, Part III: Results and parameter sensitivity

Two-fluid modelling has recently emerged as a promising approach to representing cumulus convection in weather and climate models. This study applies the two-fluid model described in Part II Thuburn et al., 2021b to a shallow cumulus convection case study over land (ARM). Large eddy simulation data is used to tune the majority of the closures that determine the properties of entrained and detrained air. The two-fluid model is generally able to reproduce the profiles of the mean and turbulent quantities over all stages of the diurnal cycle. As such, the initiation of shallow convection and the evolution of the cloud layer are well captured. The robustness of the two-fluid model is further verified using a steady-state test case (BOMEX), in which the cloud properties are also well modelled.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

A space-time parallel algorithm with adaptive mesh refinement for computational fluid dynamics

This work describes a space-time parallel algorithm with space-time adaptive mesh refinement (AMR). AMR with subcycling is added to multigrid reduction-in-time (MGRIT) in order to provide solution efficient adaptive grids with a reduction in work performed on coarser grids. This algorithm is achieved by integrating two software libraries: XBraid (Parallel time integration with multigrid. https://computation.llnl.gov/projects/parallel-timeintegration-multigrid) and Chombo (Chombo software package for AMR applications—design document, 2014). The former is a parallel time integration library using multigrid and the latter is a massively parallel structured AMR library. Employing this adaptive space-time parallel algorithm is Chord (Comput Fluids 123:202–217, 2015), a computational fluid dynamics (CFD) application code for solving compressible fluid dynamics problems. For the same solution accuracy, speedups are demonstrated from the use of space-time parallelization over the time-sequential integration on Couette flow and Stokes’ second problem. On a transient Couette flow case, at least a 1.5× speedup is achieved, and with a time periodic problem, a speedup of up to 13.7× over the time-sequential case is obtained. In both cases, the speedup is achieved by adding processors and exploring additional parallelization in time. The numerical experiments show the algorithm is promising for CFD applications that can take advantage of the time parallelism. Future work will focus on improving the parallel performance and providing more tests with complex fluid dynamics to demonstrate the full potential of the algorithm.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

The Impact of Wettability on the Co-moving Velocity of Two-Fluid Flow in Porous Media

Abstract The impact of wettability on the co-moving velocity of two-fluid flow in porous media is analyzed herein. The co-moving velocity, developed by Roy et al. (Front Phys 8:4, 2022), is a novel representation of the flow behavior of two fluids through porous media. Our study aims to better understand the behavior of the co-moving velocity by analyzing simulation data under various wetting conditions. We analyzed 46 relative permeability curves based on the Lattice–Boltzmann color fluid model and two experimentally determined relative permeability curves. The analysis of the relative permeability data followed the methodology proposed by Roy et al. (Front Phys 8:4, 2022) to reconstruct a constitutive equation for the co-moving velocity. Surprisingly, the coefficients of the constitutive equation were found to be nearly the same for all wetting conditions. On the basis of these results, a simple approach was proposed to reconstruct the relative permeability of the oil phase using only the co-moving velocity relationship and the relative permeability of the water phase. This proposed method provides new information on the interdependence of the relative permeability curves, which has implications for the history matching of production data and the solution of the associated inverse problem. The research findings contribute to a better understanding of the impact of wettability on fluid flow in porous media and provide a practical approach for estimating relative permeability based on the co-moving velocity relationship, which has never been shown before.

Engineering↗
DOE OSTI2013

Prominin-2 expression increases protrusions, decreases caveolae and inhibits Cdc42 dependent fluid phase endocytosis

Highlights: •Prominin-2 expression induced protrusions that co-localized with lipid raft markers. •Prominin-2 expression decreased caveolae, caveolar endocytosis and increased pCav1. •Prominin-2 expression inhibited fluid phase endocytosis by inactivation of Cdc42. •These endocytic effects can be reversed by adding exogenous cholesterol. •Caveolin1 knockdown restored fluid phase endocytosis in Prominin2 expressing cells. -- Abstract: Background: Membrane protrusions play important roles in biological processes such as cell adhesion, wound healing, migration, and sensing of the external environment. Cell protrusions are a subtype of membrane microdomains composed of cholesterol and sphingolipids, and can be disrupted by cholesterol depletion. Prominins are pentaspan membrane proteins that bind cholesterol and localize to plasma membrane (PM) protrusions. Prominin-1 is of great interest as a marker for stem and cancer cells, while Prominin-2 (Prom2) is reportedly restricted to epithelial cells. Aim: To characterize the effects of Prom-2 expression on PM microdomain organization. Methods: Prom2-fluorescent protein was transfected in human skin fibroblasts (HSF) and Chinese hamster ovary (CHO) cells for PM raft and endocytic studies. Caveolae at PM were visualized using transmission electron microscopy. Cdc42 activation was measured and caveolin-1 knockdown was performed using siRNAs. Results: Prom2 expression in HSF and CHO cells caused extensive Prom2-positive protrusions that co-localized with lipid raft markers. Prom2 expression significantly decreased caveolae at the PM, reduced caveolar endocytosis and increased caveolin-1 phosphorylation. Prom2 expression also inhibited Cdc42-dependent fluid phase endocytosis via decreased Cdc42 activation. Effects on endocytosis were reversed by addition of cholesterol. Knockdown of caveolin-1 by siRNA restored Cdc42 dependent fluid phase endocytosis in Prom2-expressing cells. Conclusions: Prom2 protrusions primarily localize to lipid rafts and recruit cholesterol into protrusions and away from caveolae, leading to increased phosphorylation of caveolin-1, which inhibits Cdc42-dependent endocytosis. This study provides a new insight for the role for prominins in the regulation of PM lipid organization.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Adsorption of simple square-well fluids in slit nanopores: Modeling based on Generalized van der Waals partition function and Monte Carlo simulation

A model based on the Generalized van der Waals partition function is derived to predict the adsorption of square-well fluid in slit pores of any size, the walls of which also have square-well potential. The space inside the pore is divided into several regions based on the extent of the attractive regions generated by the walls. Closed-form expressions of the chemical potentials of the confined fluid in different regions in the pore are obtained. The densities of fluid in different regions are calculated by equalizing the chemical potentials of fluid in those regions to that of the bulk phase. To examine the accuracy of the model, the Grand Canonical Monte Carlo (GCMC) simulation is also conducted. Here we find that the model well captures the effects of the bulk conditions and the properties of adsorbate and pore on the density of adsorbate in the pore. The model is also shown to be able to predict the adsorption of real gases in various activated carbons.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Selective transport of light vs. heavy rare earth elements by sulfate/bisulfate complexes in hydrothermal fluids

Here, this study explores the transport of rare earth elements (REE) in acidic sulfate-bearing hydrothermal fluids and the implications for the fractionation of light/heavy REE in critical mineral deposits. The speciation of Nd (light REE) and Yb (heavy REE) sulfate complexes were determined via in situ Raman spectroscopy using fused SiO 2 capillary cells up to 300 ºC at saturated water vapor pressure and in a hydrothermal diamond anvil cell up to 500 ºC and 540 MPa. The REE monosulfate (REESO 4 + ) and REE disulfate (REE(SO 4 ) 2 - ) species are stable below 150 to 250 ºC but become less stable at higher temperatures, particularly the light REE, due to the decreased solubility of REE sulfate solids. At higher pressure, these REE sulfate complexes display an increased stability field up to 400 ℃. The REE bisulfate complex (REEHSO 4 2+ ) was identified with a wide stability field below 400 ºC for the HREE in acidic Yb 2 (SO 4 ) 3 -bearing solutions, whereas in Nd 2 (SO 4 ) 3 -bearing solutions, the LREE bisulfate complex is restricted to below 100 ℃. These results suggest that bisulfate is a previously unrecognized selective ligand for heavy REE transport at low temperature in acidic oxidized hydrothermal fluids. Such fluids are responsible for hydrothermal alteration in many REE deposits. Prediction of phase stabilities across pressure, temperature, and composition space (P-T- x ) is crucial for predicting the role of aqueous REE sulfate complexes in the mobilization of REE in crustal fluids.

58 GEOSCIENCES↗
DOE OSTI2018

A novel algorithm of immersed moving boundary scheme for fluid-particle interactions in DEMLBM

This paper presents an efficient and accurate Immersed Moving Boundary (IMB) algorithm for solving fluid-particle interactions in the framework of the Lattice Boltzmann Method (LBM). Although the IMB scheme has been widely employed in many fluid-particle coupling problems in a wide range of applications, the algorithm of its implementation, especially in identifying both fluid and solid boundary nodes for particles, is seldom reported. Besides, the computational cost of handling fluid-particle coupling is very expensive. To provide a bridge between theory and application and improve the computing efficiency of IMB, a novel boundary tracing procedure and an efficient method for computing the solid nodal ratio using Gaussian quadrature are proposed in this paper. Both accuracy and efficiency of the proposed algorithm are examined by two benchmark tests. It is also found that the IMB scheme are more efficient and stable compared to another widely used the Immersed Boundary Method (IBM) in LBM.

42 ENGINEERING↗
DOE OSTI2017

Special issue of Computers and Fluids in honor of Cecil E. (Chuck) Leith

Here, this special issue of Computers and Fluids is dedicated to Cecil E. (Chuck) Leith in honor of his research contributions, leadership in the areas of statistical fluid mechanics, computational fluid dynamics, and climate theory. Leith's contribution to these fields emerged from his interest in solving complex fluid flow problems--even those at high Mach numbers--in an era well before large scale supercomputing became the dominant mode of inquiry into these fields. Yet the issues raised and solved by his research effort are still of vital interest today.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Sr and O isotopes in western Aleutian seafloor lavas: Implications for the source of fluids and trace element character of arc volcanic rocks

High Mg# andesites and dacites (Mg# = molar Mg/Mg + Fe) from western Aleutian seafloor volcanoes carry high concentrations of Sr (>1000 ppm) that is unradiogenic ( 87 Sr/ 86 Sr < 0.7029) compared to lavas from emergent volcanoes throughout the arc (200–800 ppm Sr, 87 Sr/ 86 Sr >0.7030). Data patterns in plots of 87 Sr/ 86 Sr vs Y/Sr and Nd/Sr imply the existence of an eclogite-melt source component – formed by partial melting of MORB eclogite in the subducting Pacific Plate – which is most clearly expressed in the compositions of western Aleutian andesites and dacites (Nd/Sr and Y/Sr < 0.02) and which dominates the source budget for Sr in volcanic rocks throughout the arc. When viewed in combination with inversely correlated ε Nd and 87 Sr/ 86 Sr, these patterns rule out aqueous fluids as an important source of Sr because mixtures of fluids from altered oceanic crust with depleted mantle and sediment produce compositions with 87 Sr/ 86 Sr higher than in common Aleutian rocks. The unradiogenic nature of Sr in the western Aleutian andesite–dacite end-member may be understood if H 2 O required to drive melting of the subducting oceanic crust is transported in fluids containing little Sr. Mass balance demonstrates that such fluids may be produced by dewatering of serpentinite in the mantle section of the subducting plate. If the eclogite-melt source component is present throughout the Aleutian arc, melting of the subducting plate must extend into minimally altered parts of the sheeted dike section or upper gabbros, at depths >2 km below the paleo-seafloor. Oxygen isotopes in western Aleutian seafloor lavas, which fall within a narrow range of MORB-like values (δ 18 O=5.1–5.7), are also consistent with this model. These results indicate that the subducting Pacific lithosphere beneath the Aleutian arc is significantly hotter than indicated my most thermal models.

58 GEOSCIENCES↗