Papers by Roney Leon Thompson
Journal of Non-Newtonian Fluid Mechanics, 2017
The so-called avalanche effect is one of the fingerprints of thixotropic materials. This self-rei... more The so-called avalanche effect is one of the fingerprints of thixotropic materials. This self-reinforcing process where the decrease in viscosity, due to a rejuvenation process triggered by a stress field, induces a motion which in turn contributes to decrease the viscosity again, is well exemplified by the inclined plane problem. In this situation, the material in its fully-structured state is placed on an inclined plane with respect to the gravity force which is responsible for the beginning of the breakdown process. These thixotropic systems generally have a yield stress, a strength that must be overcome in order to induce rejuvenation. In addition, they exhibit elastic features, especially in the pre-yield state. In the present work we numerically solve the transient evolution of an elasto-viscoplastic thixotropic material subjected to the action of gravity on an inclined plane. In order to handle with the moving free-surface boundary condition encountered in the avalanche effect , we have used a combination of the Marker-And-Cell (MAC) method with the front-tracking scheme. This formulation was successfully employed for this kind of material in the recent paper of Oishi et al. (2016) [28]. In the present work, we have adapted our finite difference formulation to analyze the effects associated with an extended Herschel-Bulkley model in the simulation of a transient complex free surface flow. Concerning the parameters of the flow curve, it is shown that the dimensionless yield stress (plastic number) is the most significant one. However, for a fixed plastic number, different combinations of dimensionless consistency index and dimensionless Newtonian viscosity plateau can lead to a diversity of responses. The thixotropic equilibrium time had a significant impact on shifting the instant when the flow regime changes from an accelerating (when the front part of the material accelerates) to a retardation one (when this front part decelerates). Higher elasticity, as captured by the Weissenberg number, led to longer distances covered by the material.
A Numerical Formulation for the Simulation of Highly Heterogeneous Porous Media
Journal of Porous Media
Although it is a tradition to investigate porous media flow with the aid of Darcy's law, ther... more Although it is a tradition to investigate porous media flow with the aid of Darcy's law, there are several applications in which heterogeneity makes this approach inadequate. Carbonate reservoirs found in the pre-salt layer in Brazil are examples of highly heterogeneous naturally fractured formations, with severe variations in their petrophysical properties. Rocks submitted to acidifying treatments are another example of highly heterogeneous porous media, where, by the injection of an acid system in the rock matrix, wormholes (highly conductive channels) are created. In this work, we numerically compare the employment of Darcy's equation with a more general formulation based on the average conservation equations for highly heterogeneous porous media. The coupled continuity and momentum equations are solved employing the open source software OpenFOAM. We apply the new formulation to three cases. The first is more academic, followed by two more applied situations associated wi...
Rheological Characterization and Formation Protocol of Tetrahydrofuran Hydrate Slurries
Energy & Fuels
Modeling and simulation of the carbonate reactive-dissolution process by viscoelastic-surfactant-based acid
Journal of Petroleum Science and Engineering
Analysis of the Convergent Channel as an Extensional Rheometer
Rheology and Fluid Mechanics of Nonlinear Materials, 1999
An important aspect while designing an “R2 z = constant” convergent channel as an extensional rhe... more An important aspect while designing an “R2 z = constant” convergent channel as an extensional rheometer is the appropriate choice of the geometrical parameters and of the Reynolds number range of operation. The higher is the Reynolds number value, the thinner will be the boundary layer where the undesirable no-slip effect is confined, as discussed in the literature. However, if the Reynolds number, Re, is too large, then shear-related pressure losses become important, which is also undesirable in rheometry. Therefore, one design task is to find a range of Re within which the boundary layer is thin enough, and the velocity field in most of the domain is reasonably close to the desired kinematics. In this work we obtained numerical solutions for the flow of Newtonian and viscoelastic fluids through a convergent channel, for representative ranges of Re, dimensionless channel length, L, and dimensionless axial coordinate of inlet section, z0. For all cases, we determined fields of flow ...
Bulletin of the American Physical Society, 2016
Submitted for the DFD16 Meeting of The American Physical Society Quantifying the Discrepancy in R... more Submitted for the DFD16 Meeting of The American Physical Society Quantifying the Discrepancy in RANS Modeling of Reynolds Stress Eigenvectors System JINLONG WU, Virginia Tech, RONEY THOMPSON, Federal University of Rio de Janeiro, JIANXUN WANG, Virginia Tech, LUIZ SAMPAIO, Stanford University, HENG XIAO, Virginia Tech — Reynolds-Averaged Navier-Stokes (RANS) equations are the dominant tool for engineering design and analysis applications involving wall bounded turbulent flows. However, the modeled Reynolds stress tensor is known to be a main source of uncertainty, comparing to other sources like geometry, boundary conditions, etc. Recently, several works have been conducted with the aim to quantify the uncertainty of RANS simulation by studying the discrepancy of anisotropy and turbulence kinetic energy of the Reynolds stress tensor with respect to a reference database obtained from DNS. On the other hand, the eigenvectors system of Reynolds stress tensor is less investigated. In thi...
Bulletin of the American Physical Society, 2016
Submitted for the DFD16 Meeting of The American Physical Society The Use of the Reynolds Stress T... more Submitted for the DFD16 Meeting of The American Physical Society The Use of the Reynolds Stress Transport Equation to Constrain Eigenvectors Perturbations on Model Form UQ of RANS Simulations LUIZ SAMPAIO, Stanford Univ, RONEY THOMPSON, Universidade Federal do Rio de Janeiro, WOUTER EDELING, AASHWIN MISHRA, GIANLUCA IACCARINO, Stanford Univ — Despite the recent developments in LES and DNS approaches for turbulent flow simulations, RANS modeling is still vastly used by industry, due to its inherent low cost. Since accuracy is a concern in RANS modeling, model-form UQ is an essential tool for assessing the impacts of this uncertainty on quantities of interest. Bounding values for the eigenvalues of the dimensionless deviatoric part of the Reynolds Stress tensor (RST) can be obtained from realizability constraints, and therefore can be used as a first step towards a general perturbation approach. In this connection, decoupling the perturbation into an intensity (kinetic energy), a shap...
Rheological Measurements of Tetrahydrofuran Hydrate Slurries
Procceedings of the 18th Brazilian Congress of Thermal Sciences and Engineering, 2020
Strategies to mitigate the error propagation of explicit Reynolds Stress Tensor closures
Procceedings of the 18th Brazilian Congress of Thermal Sciences and Engineering, 2020
Persistence–of–straining and polymer alignment in viscoelastic turbulence
Applications in Engineering Science, 2020
Abstract Drag reduction in turbulent flows by the addition of polymers is a phenomenon that has a... more Abstract Drag reduction in turbulent flows by the addition of polymers is a phenomenon that has a variety of applications in the engineering. The highly nonlinear interactions between the turbulent flow and the polymers in the polymeric solution still impose challenges to the understanding of this phenomenon. Efforts to address this problem come mainly from two sources: experiments and direct numerical simulations. In the present work we investigate through direct numerical simulations the roles of the non–persistence–of–straining tensor and the covariant strain acceleration tensor from the statistical and their alignment with the conformation tensor. In this regard, we provide a better picture of the relative orientation of this quantity.
Nonlinear subgrid-scale models employing the non-persistence-of-straining tensor
Mechanics Research Communications, 2021
Abstract Nonlinear subgrid-scale (SGS) models using the resolved rate-of-strain and non-persisten... more Abstract Nonlinear subgrid-scale (SGS) models using the resolved rate-of-strain and non-persistence-of-straining tensors are assessed employing an a priori test for turbulent channel flows using Direct Numerical Simulation (DNS) results. The modeled and DNS subgrid stress tensors are compared. The results have shown that including the non-persistence-of-straining tensor in the tensorial basis of the SGS model leads to a better representation of the anisotropy of these scales. The near-wall region modeling can be significantly improved when compared to linear models that do not consider the non-persistence-of-straining tensor.
Computers & Fluids, 2019
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights • New measures of the propagation error in a DNS database for the turbulent flow in a square duct are provided. • Data-driven models that have the Reynolds stress tensor as target are subjected to this error. • We propose to have as target, the Reynolds force vector, the divergence of the Reynolds stress tensor. • Results show that the proposed approach is promissing.
Energy & Fuels, 2018
Gas hydrates are crystalline solids formed by water and light molecules when a specific thermodyn... more Gas hydrates are crystalline solids formed by water and light molecules when a specific thermodynamic condition of high pressure and low temperature is attained. The formation of such structures can plug the production line, causing a shutdown with expensive consequences. In fact, besides waxy deposition, gas hydrate formation is among the hugest problems in flow assurance faced by the oil companies. High concentrations of CO 2 have been reported in the Brazilian Pre-salt oil wells, with large 1
Physical Review Fluids, 2019
Reynolds-averaged Navier-Stokes (RANS) models are the primary numerical recourse to investigate c... more Reynolds-averaged Navier-Stokes (RANS) models are the primary numerical recourse to investigate complex engineering turbulent flows in industrial applications. However, to establish RANS models as reliable design tools, it is essential to provide estimates for the uncertainty in their predictions. In the recent past, an uncertainty estimation framework relying on eigenvalue and eigenvector perturbations to the modeled Reynolds stress tensor has been widely applied with satisfactory results. However, the methodology for the eigenvector perturbations is not well established. Evaluations using only eigenvalue perturbations do not provide comprehensive estimates of model form uncertainty, especially in flows with streamline curvature, recirculation, or flow separation. In this article, we outline a methodology for the eigenvector perturbations using a predictor-corrector approach, which uses the incipient eigenvalue perturbations along with the Reynolds stress transport equations to determine the eigenvector perturbations. This approach was applied to benchmark cases of complex turbulent flows. The uncertainty intervals estimated using the proposed framework exhibited substantial improvement over eigenvalue-only perturbations and are able to account for a significant proportion of the discrepancy between RANS predictions and high-fidelity data.
Nonlinear eddy viscosity models for viscoelastic turbulence
Procceedings of the 24th ABCM International Congress of Mechanical Engineering, 2017
Rheological Study of Gas Hydrates Formed from Carbon Dioxide Molecules
Procceedings of the 24th ABCM International Congress of Mechanical Engineering, 2017
Procceedings of the 24th ABCM International Congress of Mechanical Engineering, 2017
Dissertation presented to COPPE/UFRJ as a partial fulfillment of the requirements for the degree ... more Dissertation presented to COPPE/UFRJ as a partial fulfillment of the requirements for the degree of Master of Science (M.Sc.
Displacement of Viscous Liquids by a Viscoplastic Material on Capillary Tubes
Procceedings of the 16th Brazilian Congress of Thermal Sciences and Engineering, 2016
Displacement of Viscous Liquids by a Newtonian Material on Capillary Tubes
Procceedings of the 16th Brazilian Congress of Thermal Sciences and Engineering, 2016
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Papers by Roney Leon Thompson