Cumulative reports and publications

A complete list of Institute for Computer Applications in Science and Engineering (ICASE) reports are listed. Since ICASE reports are intended to be preprints of articles that will appear in journals or conference proceedings, the published reference is included when it is available. The major categories of the current ICASE research program are: applied and numerical mathematics, including numerical analysis and algorithm development; theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustics and combustion; experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and computer science

Robust statistical approaches for local planar surface fitting in 3D laser scanning data

This paper proposes robust methods for local planar surface fitting in 3D laser scanning data. Searching through the literature revealed that many authors frequently used Least Squares (LS) and Principal Component Analysis (PCA) for point cloud processing without any treatment of outliers. It is known that LS and PCA are sensitive to outliers and can give inconsistent and misleading estimates. RANdom SAmple Consensus (RANSAC) is one of the most well-known robust methods used for model fitting when noise and/or outliers are present. We concentrate on the recently introduced Deterministic Minimum Covariance Determinant estimator and robust PCA, and propose two variants of statistically robust algorithms for fitting planar surfaces to 3D laser scanning point cloud data. The performance of the proposed robust methods is demonstrated by qualitative and quantitative analysis through several synthetic and mobile laser scanning 3D data sets for different applications. Using simulated data, and comparisons with LS, PCA, RANSAC, variants of RANSAC and other robust statistical methods, we demonstrate that the new algorithms are significantly more efficient, faster, and produce more accurate fits and robust local statistics (e.g. surface normals), necessary for many point cloud processing tasks.Consider one example data set used consisting of 100 points with 20% outliers representing a plane. The proposed methods called DetRD-PCA and DetRPCA, produce bias angles (angle between the fitted planes with and without outliers) of 0.20° and 0.24° respectively, whereas LS, PCA and RANSAC produce worse bias angles of 52.49°, 39.55° and 0.79° respectively. In terms of speed, DetRD-PCA takes 0.033 s on average for fitting a plane, which is approximately 6.5, 25.4 and 25.8 times faster than RANSAC, and two other robust statistical methods, respectively. The estimated robust surface normals and curvatures from the new methods have been used for plane fitting, sharp feature preservation and segmentation in 3D point clouds obtained from laser scanners. The results are significantly better and more efficiently computed than those obtained by existing methods

Reactive Flow and Transport Through Complex Systems

The meeting focused on mathematical aspects of reactive flow, diffusion and transport through complex systems. The research interest of the participants varied from physical modeling using PDEs, mathematical modeling using upscaling and homogenization, numerical analysis of PDEs describing reactive transport, PDEs from fluid mechanics, computational methods for random media and computational multiscale methods

Hydromechanical Frameworks for Assessing the Occurrence of Wellbore Bridging and Fracture Broaching During Blowouts

Rigorous hydromechanical frameworks needed for modeling wellbore bridging and broaching during uncontrolled production of oil and gas are developed in this work. First, two sources of sand production are identified: borehole breakout and erosion of the producing formation. Theoretical framework for predicting the morphology of type B breakout mode is developed for the first time in this study; both fracture mechanics and shear failure theories are used in predicting the breakout geometry. Furthermore, a framework for estimating the size of caving produced during breakout (type A or B) is presented. Using asymptotic analysis of crack-boundary interactions, the state of damage around the borehole during the breakout process is determined, and the limiting buckling lengths of the resulting wing-cracks are predicted based on plate buckling theory. Third, a three-phase erosion kinetic equations, coupled with an erosion constitutive law, which is based on virtual power principle, are used in modeling radial and axial erosion in the reservoir and along the wellbore respectively. The proposed erosion constitutive law identifies the limitation of the pressure-gradient phenomenological model, which is currently being used. For a rigorous investigation into the self-killing of the well, a thermodynamically multiphase field model is developed for the gas-liquid-solid flow. The model, which is the combination of Navier-Stokes and Cahn-Hilliard type equations, incorporates the hydrodynamic interactions among the different species of the mixture. Lastly, this work considers a faster means for estimating fracture propagation in heterogeneous media (layered or naturally fractured) in the event the well is shut-in